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-rw-r--r--debian/patches/gssapi.patch4156
1 files changed, 4156 insertions, 0 deletions
diff --git a/debian/patches/gssapi.patch b/debian/patches/gssapi.patch
new file mode 100644
index 0000000..072c079
--- /dev/null
+++ b/debian/patches/gssapi.patch
@@ -0,0 +1,4156 @@
+From 61798b25a23b55d72a86a35062106cc3fc0ab834 Mon Sep 17 00:00:00 2001
+From: Simon Wilkinson <simon@sxw.org.uk>
+Date: Sun, 9 Feb 2014 16:09:48 +0000
+Subject: GSSAPI key exchange support
+
+This patch has been rejected upstream: "None of the OpenSSH developers are
+in favour of adding this, and this situation has not changed for several
+years. This is not a slight on Simon's patch, which is of fine quality, but
+just that a) we don't trust GSSAPI implementations that much and b) we don't
+like adding new KEX since they are pre-auth attack surface. This one is
+particularly scary, since it requires hooks out to typically root-owned
+system resources."
+
+However, quite a lot of people rely on this in Debian, and it's better to
+have it merged into the main openssh package rather than having separate
+-krb5 packages (as we used to have). It seems to have a generally good
+security history.
+
+Author: Simon Wilkinson <simon@sxw.org.uk>
+Author: Colin Watson <cjwatson@debian.org>
+Author: Jakub Jelen <jjelen@redhat.com>
+Origin: other, https://github.com/openssh-gsskex/openssh-gsskex/pull/23
+Bug: https://bugzilla.mindrot.org/show_bug.cgi?id=1242
+Last-Updated: 2023-01-02
+
+Patch-Name: gssapi.patch
+---
+ Makefile.in | 5 +-
+ README.md | 36 +++
+ auth.c | 94 +-------
+ auth2-gss.c | 56 ++++-
+ auth2.c | 2 +
+ canohost.c | 91 ++++++++
+ canohost.h | 3 +
+ clientloop.c | 13 ++
+ configure.ac | 24 ++
+ gss-genr.c | 297 +++++++++++++++++++++++-
+ gss-serv-krb5.c | 87 ++++++-
+ gss-serv.c | 205 +++++++++++++++--
+ kex.c | 66 +++++-
+ kex.h | 29 +++
+ kexdh.c | 10 +
+ kexgen.c | 2 +-
+ kexgssc.c | 599 ++++++++++++++++++++++++++++++++++++++++++++++++
+ kexgsss.c | 474 ++++++++++++++++++++++++++++++++++++++
+ monitor.c | 139 ++++++++++-
+ monitor.h | 2 +
+ monitor_wrap.c | 57 ++++-
+ monitor_wrap.h | 4 +-
+ readconf.c | 74 ++++++
+ readconf.h | 6 +
+ servconf.c | 47 ++++
+ servconf.h | 3 +
+ session.c | 10 +-
+ ssh-gss.h | 54 ++++-
+ ssh-null.c | 108 +++++++++
+ ssh.1 | 8 +
+ ssh.c | 6 +-
+ ssh_config | 2 +
+ ssh_config.5 | 57 +++++
+ sshconnect2.c | 156 ++++++++++++-
+ sshd.c | 62 ++++-
+ sshd_config | 2 +
+ sshd_config.5 | 30 +++
+ sshkey.c | 8 +-
+ sshkey.h | 1 +
+ 39 files changed, 2765 insertions(+), 164 deletions(-)
+ create mode 100644 kexgssc.c
+ create mode 100644 kexgsss.c
+ create mode 100644 ssh-null.c
+
+diff --git a/Makefile.in b/Makefile.in
+index c0ebfa041..32b607719 100644
+--- a/Makefile.in
++++ b/Makefile.in
+@@ -101,7 +101,7 @@ LIBSSH_OBJS=${LIBOPENSSH_OBJS} \
+ readpass.o ttymodes.o xmalloc.o addr.o addrmatch.o \
+ atomicio.o dispatch.o mac.o misc.o utf8.o \
+ monitor_fdpass.o rijndael.o ssh-dss.o ssh-ecdsa.o ssh-ecdsa-sk.o \
+- ssh-ed25519-sk.o ssh-rsa.o dh.o \
++ ssh-ed25519-sk.o ssh-rsa.o ssh-null.o dh.o \
+ msg.o progressmeter.o dns.o entropy.o gss-genr.o umac.o umac128.o \
+ ssh-pkcs11.o smult_curve25519_ref.o \
+ poly1305.o chacha.o cipher-chachapoly.o cipher-chachapoly-libcrypto.o \
+@@ -110,6 +110,7 @@ LIBSSH_OBJS=${LIBOPENSSH_OBJS} \
+ kex.o kexdh.o kexgex.o kexecdh.o kexc25519.o \
+ kexgexc.o kexgexs.o \
+ kexsntrup761x25519.o sntrup761.o kexgen.o \
++ kexgssc.o \
+ sftp-realpath.o platform-pledge.o platform-tracing.o platform-misc.o \
+ sshbuf-io.o
+
+@@ -126,7 +127,7 @@ SSHDOBJS=sshd.o auth-rhosts.o auth-passwd.o \
+ auth-bsdauth.o auth2-hostbased.o auth2-kbdint.o \
+ auth2-none.o auth2-passwd.o auth2-pubkey.o auth2-pubkeyfile.o \
+ monitor.o monitor_wrap.o auth-krb5.o \
+- auth2-gss.o gss-serv.o gss-serv-krb5.o \
++ auth2-gss.o gss-serv.o gss-serv-krb5.o kexgsss.o \
+ loginrec.o auth-pam.o auth-shadow.o auth-sia.o \
+ srclimit.o sftp-server.o sftp-common.o \
+ sandbox-null.o sandbox-rlimit.o sandbox-systrace.o sandbox-darwin.o \
+diff --git a/README.md b/README.md
+index 3da933817..a338802ff 100644
+--- a/README.md
++++ b/README.md
+@@ -1,3 +1,39 @@
++Portable OpenSSH with GSSAPI Key Exchange patches
++=================================================
++
++[![Language grade: C/C++](https://img.shields.io/lgtm/grade/cpp/g/openssh-gsskex/openssh-gsskex.svg?logo=lgtm&logoWidth=18)](https://lgtm.com/projects/g/openssh-gsskex/openssh-gsskex/context:cpp)
++
++Currently, there are two branches with gssapi key exchange related
++patches:
++
++ * fedora/master: Changes that are shipped in Fedora [![Build Status](https://travis-ci.org/openssh-gsskex/openssh-gsskex.svg?branch=fedora%2Fmaster)](https://travis-ci.org/openssh-gsskex/openssh-gsskex)
++ * debian/master: Changes that are shipped in Debian [![Build Status](https://travis-ci.org/openssh-gsskex/openssh-gsskex.svg?branch=debian%2Fmaster)](https://travis-ci.org/openssh-gsskex/openssh-gsskex)
++
++The target is to converge to a shared repository with single master
++branch from where we could build releases for both OSes.
++
++
++What is in:
++
++ * The original patch implementing missing parts of RFC4462 by Simon Wilkinson
++ adapted to the current OpenSSH versions and with several fixes
++ * New methods for GSSAPI Kex from IETF draft [1] from Jakub Jelen
++
++
++Missing kerberos-related parts:
++
++ * .k5login and .kusers support available in Fedora [2] [3].
++ * Improved handling of kerberos ccache location [4]
++
++
++
++[1] https://tools.ietf.org/html/draft-ietf-curdle-gss-keyex-sha2-08
++[2] https://src.fedoraproject.org/rpms/openssh/blob/master/f/openssh-6.6p1-kuserok.patch
++[3] https://src.fedoraproject.org/rpms/openssh/blob/master/f/openssh-6.6p1-GSSAPIEnablek5users.patch
++[4] https://bugzilla.mindrot.org/show_bug.cgi?id=2775
++
++-------------------------------------------------------------------------------
++
+ # Portable OpenSSH
+
+ [![C/C++ CI](https://github.com/openssh/openssh-portable/actions/workflows/c-cpp.yml/badge.svg)](https://github.com/openssh/openssh-portable/actions/workflows/c-cpp.yml)
+diff --git a/auth.c b/auth.c
+index 03a777cce..946dc6074 100644
+--- a/auth.c
++++ b/auth.c
+@@ -358,7 +358,8 @@ auth_root_allowed(struct ssh *ssh, const char *method)
+ case PERMIT_NO_PASSWD:
+ if (strcmp(method, "publickey") == 0 ||
+ strcmp(method, "hostbased") == 0 ||
+- strcmp(method, "gssapi-with-mic") == 0)
++ strcmp(method, "gssapi-with-mic") == 0 ||
++ strcmp(method, "gssapi-keyex") == 0)
+ return 1;
+ break;
+ case PERMIT_FORCED_ONLY:
+@@ -638,97 +639,6 @@ fakepw(void)
+ return (&fake);
+ }
+
+-/*
+- * Returns the remote DNS hostname as a string. The returned string must not
+- * be freed. NB. this will usually trigger a DNS query the first time it is
+- * called.
+- * This function does additional checks on the hostname to mitigate some
+- * attacks on based on conflation of hostnames and IP addresses.
+- */
+-
+-static char *
+-remote_hostname(struct ssh *ssh)
+-{
+- struct sockaddr_storage from;
+- socklen_t fromlen;
+- struct addrinfo hints, *ai, *aitop;
+- char name[NI_MAXHOST], ntop2[NI_MAXHOST];
+- const char *ntop = ssh_remote_ipaddr(ssh);
+-
+- /* Get IP address of client. */
+- fromlen = sizeof(from);
+- memset(&from, 0, sizeof(from));
+- if (getpeername(ssh_packet_get_connection_in(ssh),
+- (struct sockaddr *)&from, &fromlen) == -1) {
+- debug("getpeername failed: %.100s", strerror(errno));
+- return xstrdup(ntop);
+- }
+-
+- ipv64_normalise_mapped(&from, &fromlen);
+- if (from.ss_family == AF_INET6)
+- fromlen = sizeof(struct sockaddr_in6);
+-
+- debug3("Trying to reverse map address %.100s.", ntop);
+- /* Map the IP address to a host name. */
+- if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
+- NULL, 0, NI_NAMEREQD) != 0) {
+- /* Host name not found. Use ip address. */
+- return xstrdup(ntop);
+- }
+-
+- /*
+- * if reverse lookup result looks like a numeric hostname,
+- * someone is trying to trick us by PTR record like following:
+- * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5
+- */
+- memset(&hints, 0, sizeof(hints));
+- hints.ai_socktype = SOCK_DGRAM; /*dummy*/
+- hints.ai_flags = AI_NUMERICHOST;
+- if (getaddrinfo(name, NULL, &hints, &ai) == 0) {
+- logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
+- name, ntop);
+- freeaddrinfo(ai);
+- return xstrdup(ntop);
+- }
+-
+- /* Names are stored in lowercase. */
+- lowercase(name);
+-
+- /*
+- * Map it back to an IP address and check that the given
+- * address actually is an address of this host. This is
+- * necessary because anyone with access to a name server can
+- * define arbitrary names for an IP address. Mapping from
+- * name to IP address can be trusted better (but can still be
+- * fooled if the intruder has access to the name server of
+- * the domain).
+- */
+- memset(&hints, 0, sizeof(hints));
+- hints.ai_family = from.ss_family;
+- hints.ai_socktype = SOCK_STREAM;
+- if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
+- logit("reverse mapping checking getaddrinfo for %.700s "
+- "[%s] failed.", name, ntop);
+- return xstrdup(ntop);
+- }
+- /* Look for the address from the list of addresses. */
+- for (ai = aitop; ai; ai = ai->ai_next) {
+- if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
+- sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
+- (strcmp(ntop, ntop2) == 0))
+- break;
+- }
+- freeaddrinfo(aitop);
+- /* If we reached the end of the list, the address was not there. */
+- if (ai == NULL) {
+- /* Address not found for the host name. */
+- logit("Address %.100s maps to %.600s, but this does not "
+- "map back to the address.", ntop, name);
+- return xstrdup(ntop);
+- }
+- return xstrdup(name);
+-}
+-
+ /*
+ * Return the canonical name of the host in the other side of the current
+ * connection. The host name is cached, so it is efficient to call this
+diff --git a/auth2-gss.c b/auth2-gss.c
+index 2062609d9..4566d425c 100644
+--- a/auth2-gss.c
++++ b/auth2-gss.c
+@@ -1,7 +1,7 @@
+ /* $OpenBSD: auth2-gss.c,v 1.33 2021/12/19 22:12:07 djm Exp $ */
+
+ /*
+- * Copyright (c) 2001-2003 Simon Wilkinson. All rights reserved.
++ * Copyright (c) 2001-2007 Simon Wilkinson. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+@@ -55,6 +55,48 @@ static int input_gssapi_mic(int type, u_int32_t plen, struct ssh *ssh);
+ static int input_gssapi_exchange_complete(int type, u_int32_t plen, struct ssh *ssh);
+ static int input_gssapi_errtok(int, u_int32_t, struct ssh *);
+
++/*
++ * The 'gssapi_keyex' userauth mechanism.
++ */
++static int
++userauth_gsskeyex(struct ssh *ssh)
++{
++ Authctxt *authctxt = ssh->authctxt;
++ int r, authenticated = 0;
++ struct sshbuf *b = NULL;
++ gss_buffer_desc mic, gssbuf;
++ u_char *p;
++ size_t len;
++
++ if ((r = sshpkt_get_string(ssh, &p, &len)) != 0 ||
++ (r = sshpkt_get_end(ssh)) != 0)
++ fatal_fr(r, "parsing");
++
++ if ((b = sshbuf_new()) == NULL)
++ fatal_f("sshbuf_new failed");
++
++ mic.value = p;
++ mic.length = len;
++
++ ssh_gssapi_buildmic(b, authctxt->user, authctxt->service,
++ "gssapi-keyex", ssh->kex->session_id);
++
++ if ((gssbuf.value = sshbuf_mutable_ptr(b)) == NULL)
++ fatal_f("sshbuf_mutable_ptr failed");
++ gssbuf.length = sshbuf_len(b);
++
++ /* gss_kex_context is NULL with privsep, so we can't check it here */
++ if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gss_kex_context,
++ &gssbuf, &mic))))
++ authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user,
++ authctxt->pw, 1));
++
++ sshbuf_free(b);
++ free(mic.value);
++
++ return (authenticated);
++}
++
+ /*
+ * We only support those mechanisms that we know about (ie ones that we know
+ * how to check local user kuserok and the like)
+@@ -261,7 +303,8 @@ input_gssapi_exchange_complete(int type, u_int32_t plen, struct ssh *ssh)
+ if ((r = sshpkt_get_end(ssh)) != 0)
+ fatal_fr(r, "parse packet");
+
+- authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
++ authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user,
++ authctxt->pw, 1));
+
+ if ((!use_privsep || mm_is_monitor()) &&
+ (displayname = ssh_gssapi_displayname()) != NULL)
+@@ -307,7 +350,8 @@ input_gssapi_mic(int type, u_int32_t plen, struct ssh *ssh)
+ gssbuf.length = sshbuf_len(b);
+
+ if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic))))
+- authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
++ authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user,
++ authctxt->pw, 0));
+ else
+ logit("GSSAPI MIC check failed");
+
+@@ -327,6 +371,12 @@ input_gssapi_mic(int type, u_int32_t plen, struct ssh *ssh)
+ return 0;
+ }
+
++Authmethod method_gsskeyex = {
++ "gssapi-keyex",
++ userauth_gsskeyex,
++ &options.gss_authentication
++};
++
+ Authmethod method_gssapi = {
+ "gssapi-with-mic",
+ NULL,
+diff --git a/auth2.c b/auth2.c
+index 6c061934b..44bd49177 100644
+--- a/auth2.c
++++ b/auth2.c
+@@ -71,6 +71,7 @@ extern Authmethod method_passwd;
+ extern Authmethod method_kbdint;
+ extern Authmethod method_hostbased;
+ #ifdef GSSAPI
++extern Authmethod method_gsskeyex;
+ extern Authmethod method_gssapi;
+ #endif
+
+@@ -78,6 +79,7 @@ Authmethod *authmethods[] = {
+ &method_none,
+ &method_pubkey,
+ #ifdef GSSAPI
++ &method_gsskeyex,
+ &method_gssapi,
+ #endif
+ &method_passwd,
+diff --git a/canohost.c b/canohost.c
+index a810da0ee..99f1cd406 100644
+--- a/canohost.c
++++ b/canohost.c
+@@ -35,6 +35,97 @@
+ #include "canohost.h"
+ #include "misc.h"
+
++/*
++ * Returns the remote DNS hostname as a string. The returned string must not
++ * be freed. NB. this will usually trigger a DNS query the first time it is
++ * called.
++ * This function does additional checks on the hostname to mitigate some
++ * attacks on legacy rhosts-style authentication.
++ */
++
++char *
++remote_hostname(struct ssh *ssh)
++{
++ struct sockaddr_storage from;
++ socklen_t fromlen;
++ struct addrinfo hints, *ai, *aitop;
++ char name[NI_MAXHOST], ntop2[NI_MAXHOST];
++ const char *ntop = ssh_remote_ipaddr(ssh);
++
++ /* Get IP address of client. */
++ fromlen = sizeof(from);
++ memset(&from, 0, sizeof(from));
++ if (getpeername(ssh_packet_get_connection_in(ssh),
++ (struct sockaddr *)&from, &fromlen) == -1) {
++ debug("getpeername failed: %.100s", strerror(errno));
++ return xstrdup(ntop);
++ }
++
++ ipv64_normalise_mapped(&from, &fromlen);
++ if (from.ss_family == AF_INET6)
++ fromlen = sizeof(struct sockaddr_in6);
++
++ debug3("Trying to reverse map address %.100s.", ntop);
++ /* Map the IP address to a host name. */
++ if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
++ NULL, 0, NI_NAMEREQD) != 0) {
++ /* Host name not found. Use ip address. */
++ return xstrdup(ntop);
++ }
++
++ /*
++ * if reverse lookup result looks like a numeric hostname,
++ * someone is trying to trick us by PTR record like following:
++ * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5
++ */
++ memset(&hints, 0, sizeof(hints));
++ hints.ai_socktype = SOCK_DGRAM; /*dummy*/
++ hints.ai_flags = AI_NUMERICHOST;
++ if (getaddrinfo(name, NULL, &hints, &ai) == 0) {
++ logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
++ name, ntop);
++ freeaddrinfo(ai);
++ return xstrdup(ntop);
++ }
++
++ /* Names are stored in lowercase. */
++ lowercase(name);
++
++ /*
++ * Map it back to an IP address and check that the given
++ * address actually is an address of this host. This is
++ * necessary because anyone with access to a name server can
++ * define arbitrary names for an IP address. Mapping from
++ * name to IP address can be trusted better (but can still be
++ * fooled if the intruder has access to the name server of
++ * the domain).
++ */
++ memset(&hints, 0, sizeof(hints));
++ hints.ai_family = from.ss_family;
++ hints.ai_socktype = SOCK_STREAM;
++ if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
++ logit("reverse mapping checking getaddrinfo for %.700s "
++ "[%s] failed.", name, ntop);
++ return xstrdup(ntop);
++ }
++ /* Look for the address from the list of addresses. */
++ for (ai = aitop; ai; ai = ai->ai_next) {
++ if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
++ sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
++ (strcmp(ntop, ntop2) == 0))
++ break;
++ }
++ freeaddrinfo(aitop);
++ /* If we reached the end of the list, the address was not there. */
++ if (ai == NULL) {
++ /* Address not found for the host name. */
++ logit("Address %.100s maps to %.600s, but this does not "
++ "map back to the address.", ntop, name);
++ return xstrdup(ntop);
++ }
++ return xstrdup(name);
++}
++
+ void
+ ipv64_normalise_mapped(struct sockaddr_storage *addr, socklen_t *len)
+ {
+diff --git a/canohost.h b/canohost.h
+index 26d62855a..0cadc9f18 100644
+--- a/canohost.h
++++ b/canohost.h
+@@ -15,6 +15,9 @@
+ #ifndef _CANOHOST_H
+ #define _CANOHOST_H
+
++struct ssh;
++
++char *remote_hostname(struct ssh *);
+ char *get_peer_ipaddr(int);
+ int get_peer_port(int);
+ char *get_local_ipaddr(int);
+diff --git a/clientloop.c b/clientloop.c
+index fef9efc6c..8f1fac58a 100644
+--- a/clientloop.c
++++ b/clientloop.c
+@@ -115,6 +115,10 @@
+ #include "ssherr.h"
+ #include "hostfile.h"
+
++#ifdef GSSAPI
++#include "ssh-gss.h"
++#endif
++
+ /* Permitted RSA signature algorithms for UpdateHostkeys proofs */
+ #define HOSTKEY_PROOF_RSA_ALGS "rsa-sha2-512,rsa-sha2-256"
+
+@@ -1415,6 +1419,15 @@ client_loop(struct ssh *ssh, int have_pty, int escape_char_arg,
+ /* Do channel operations. */
+ channel_after_poll(ssh, pfd, npfd_active);
+
++#ifdef GSSAPI
++ if (!ssh_packet_is_rekeying(ssh) &&
++ options.gss_renewal_rekey &&
++ ssh_gssapi_credentials_updated(NULL)) {
++ debug("credentials updated - forcing rekey");
++ need_rekeying = 1;
++ }
++#endif
++
+ /* Buffer input from the connection. */
+ if (conn_in_ready)
+ client_process_net_input(ssh);
+diff --git a/configure.ac b/configure.ac
+index 22fee70f6..75a9e5670 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -756,6 +756,30 @@ int main(void) { if (NSVersionOfRunTimeLibrary("System") >= (60 << 16))
+ [Use tunnel device compatibility to OpenBSD])
+ AC_DEFINE([SSH_TUN_PREPEND_AF], [1],
+ [Prepend the address family to IP tunnel traffic])
++ AC_MSG_CHECKING([if we have the Security Authorization Session API])
++ AC_TRY_COMPILE([#include <Security/AuthSession.h>],
++ [SessionCreate(0, 0);],
++ [ac_cv_use_security_session_api="yes"
++ AC_DEFINE([USE_SECURITY_SESSION_API], [1],
++ [platform has the Security Authorization Session API])
++ LIBS="$LIBS -framework Security"
++ AC_MSG_RESULT([yes])],
++ [ac_cv_use_security_session_api="no"
++ AC_MSG_RESULT([no])])
++ AC_MSG_CHECKING([if we have an in-memory credentials cache])
++ AC_TRY_COMPILE(
++ [#include <Kerberos/Kerberos.h>],
++ [cc_context_t c;
++ (void) cc_initialize (&c, 0, NULL, NULL);],
++ [AC_DEFINE([USE_CCAPI], [1],
++ [platform uses an in-memory credentials cache])
++ LIBS="$LIBS -framework Security"
++ AC_MSG_RESULT([yes])
++ if test "x$ac_cv_use_security_session_api" = "xno"; then
++ AC_MSG_ERROR([*** Need a security framework to use the credentials cache API ***])
++ fi],
++ [AC_MSG_RESULT([no])]
++ )
+ m4_pattern_allow([AU_IPv])
+ AC_CHECK_DECL([AU_IPv4], [],
+ AC_DEFINE([AU_IPv4], [0], [System only supports IPv4 audit records])
+diff --git a/gss-genr.c b/gss-genr.c
+index 2cd695e54..9f9745b7f 100644
+--- a/gss-genr.c
++++ b/gss-genr.c
+@@ -1,7 +1,7 @@
+ /* $OpenBSD: gss-genr.c,v 1.28 2021/01/27 10:05:28 djm Exp $ */
+
+ /*
+- * Copyright (c) 2001-2007 Simon Wilkinson. All rights reserved.
++ * Copyright (c) 2001-2009 Simon Wilkinson. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+@@ -42,9 +42,33 @@
+ #include "sshbuf.h"
+ #include "log.h"
+ #include "ssh2.h"
++#include "cipher.h"
++#include "sshkey.h"
++#include "kex.h"
++#include "digest.h"
++#include "packet.h"
+
+ #include "ssh-gss.h"
+
++typedef struct {
++ char *encoded;
++ gss_OID oid;
++} ssh_gss_kex_mapping;
++
++/*
++ * XXX - It would be nice to find a more elegant way of handling the
++ * XXX passing of the key exchange context to the userauth routines
++ */
++
++Gssctxt *gss_kex_context = NULL;
++
++static ssh_gss_kex_mapping *gss_enc2oid = NULL;
++
++int
++ssh_gssapi_oid_table_ok(void) {
++ return (gss_enc2oid != NULL);
++}
++
+ /* sshbuf_get for gss_buffer_desc */
+ int
+ ssh_gssapi_get_buffer_desc(struct sshbuf *b, gss_buffer_desc *g)
+@@ -60,6 +84,159 @@ ssh_gssapi_get_buffer_desc(struct sshbuf *b, gss_buffer_desc *g)
+ return 0;
+ }
+
++/* sshpkt_get of gss_buffer_desc */
++int
++ssh_gssapi_sshpkt_get_buffer_desc(struct ssh *ssh, gss_buffer_desc *g)
++{
++ int r;
++ u_char *p;
++ size_t len;
++
++ if ((r = sshpkt_get_string(ssh, &p, &len)) != 0)
++ return r;
++ g->value = p;
++ g->length = len;
++ return 0;
++}
++
++/*
++ * Return a list of the gss-group1-sha1 mechanisms supported by this program
++ *
++ * We test mechanisms to ensure that we can use them, to avoid starting
++ * a key exchange with a bad mechanism
++ */
++
++char *
++ssh_gssapi_client_mechanisms(const char *host, const char *client,
++ const char *kex) {
++ gss_OID_set gss_supported = NULL;
++ OM_uint32 min_status;
++
++ if (GSS_ERROR(gss_indicate_mechs(&min_status, &gss_supported)))
++ return NULL;
++
++ return ssh_gssapi_kex_mechs(gss_supported, ssh_gssapi_check_mechanism,
++ host, client, kex);
++}
++
++char *
++ssh_gssapi_kex_mechs(gss_OID_set gss_supported, ssh_gssapi_check_fn *check,
++ const char *host, const char *client, const char *kex) {
++ struct sshbuf *buf = NULL;
++ size_t i;
++ int r = SSH_ERR_ALLOC_FAIL;
++ int oidpos, enclen;
++ char *mechs, *encoded;
++ u_char digest[SSH_DIGEST_MAX_LENGTH];
++ char deroid[2];
++ struct ssh_digest_ctx *md = NULL;
++ char *s, *cp, *p;
++
++ if (gss_enc2oid != NULL) {
++ for (i = 0; gss_enc2oid[i].encoded != NULL; i++)
++ free(gss_enc2oid[i].encoded);
++ free(gss_enc2oid);
++ }
++
++ gss_enc2oid = xmalloc(sizeof(ssh_gss_kex_mapping) *
++ (gss_supported->count + 1));
++
++ if ((buf = sshbuf_new()) == NULL)
++ fatal_f("sshbuf_new failed");
++
++ oidpos = 0;
++ s = cp = xstrdup(kex);
++ for (i = 0; i < gss_supported->count; i++) {
++ if (gss_supported->elements[i].length < 128 &&
++ (*check)(NULL, &(gss_supported->elements[i]), host, client)) {
++
++ deroid[0] = SSH_GSS_OIDTYPE;
++ deroid[1] = gss_supported->elements[i].length;
++
++ if ((md = ssh_digest_start(SSH_DIGEST_MD5)) == NULL ||
++ (r = ssh_digest_update(md, deroid, 2)) != 0 ||
++ (r = ssh_digest_update(md,
++ gss_supported->elements[i].elements,
++ gss_supported->elements[i].length)) != 0 ||
++ (r = ssh_digest_final(md, digest, sizeof(digest))) != 0)
++ fatal_fr(r, "digest failed");
++ ssh_digest_free(md);
++ md = NULL;
++
++ encoded = xmalloc(ssh_digest_bytes(SSH_DIGEST_MD5)
++ * 2);
++ enclen = __b64_ntop(digest,
++ ssh_digest_bytes(SSH_DIGEST_MD5), encoded,
++ ssh_digest_bytes(SSH_DIGEST_MD5) * 2);
++
++ cp = strncpy(s, kex, strlen(kex));
++ for ((p = strsep(&cp, ",")); p && *p != '\0';
++ (p = strsep(&cp, ","))) {
++ if (sshbuf_len(buf) != 0 &&
++ (r = sshbuf_put_u8(buf, ',')) != 0)
++ fatal_fr(r, "sshbuf_put_u8 error");
++ if ((r = sshbuf_put(buf, p, strlen(p))) != 0 ||
++ (r = sshbuf_put(buf, encoded, enclen)) != 0)
++ fatal_fr(r, "sshbuf_put error");
++ }
++
++ gss_enc2oid[oidpos].oid = &(gss_supported->elements[i]);
++ gss_enc2oid[oidpos].encoded = encoded;
++ oidpos++;
++ }
++ }
++ free(s);
++ gss_enc2oid[oidpos].oid = NULL;
++ gss_enc2oid[oidpos].encoded = NULL;
++
++ if ((mechs = sshbuf_dup_string(buf)) == NULL)
++ fatal_f("sshbuf_dup_string failed");
++
++ sshbuf_free(buf);
++
++ if (strlen(mechs) == 0) {
++ free(mechs);
++ mechs = NULL;
++ }
++
++ return (mechs);
++}
++
++gss_OID
++ssh_gssapi_id_kex(Gssctxt *ctx, char *name, int kex_type) {
++ int i = 0;
++
++#define SKIP_KEX_NAME(type) \
++ case type: \
++ if (strlen(name) < sizeof(type##_ID)) \
++ return GSS_C_NO_OID; \
++ name += sizeof(type##_ID) - 1; \
++ break;
++
++ switch (kex_type) {
++ SKIP_KEX_NAME(KEX_GSS_GRP1_SHA1)
++ SKIP_KEX_NAME(KEX_GSS_GRP14_SHA1)
++ SKIP_KEX_NAME(KEX_GSS_GRP14_SHA256)
++ SKIP_KEX_NAME(KEX_GSS_GRP16_SHA512)
++ SKIP_KEX_NAME(KEX_GSS_GEX_SHA1)
++ SKIP_KEX_NAME(KEX_GSS_NISTP256_SHA256)
++ SKIP_KEX_NAME(KEX_GSS_C25519_SHA256)
++ default:
++ return GSS_C_NO_OID;
++ }
++
++#undef SKIP_KEX_NAME
++
++ while (gss_enc2oid[i].encoded != NULL &&
++ strcmp(name, gss_enc2oid[i].encoded) != 0)
++ i++;
++
++ if (gss_enc2oid[i].oid != NULL && ctx != NULL)
++ ssh_gssapi_set_oid(ctx, gss_enc2oid[i].oid);
++
++ return gss_enc2oid[i].oid;
++}
++
+ /* Check that the OID in a data stream matches that in the context */
+ int
+ ssh_gssapi_check_oid(Gssctxt *ctx, void *data, size_t len)
+@@ -216,7 +393,7 @@ ssh_gssapi_init_ctx(Gssctxt *ctx, int deleg_creds, gss_buffer_desc *recv_tok,
+ }
+
+ ctx->major = gss_init_sec_context(&ctx->minor,
+- GSS_C_NO_CREDENTIAL, &ctx->context, ctx->name, ctx->oid,
++ ctx->client_creds, &ctx->context, ctx->name, ctx->oid,
+ GSS_C_MUTUAL_FLAG | GSS_C_INTEG_FLAG | deleg_flag,
+ 0, NULL, recv_tok, NULL, send_tok, flags, NULL);
+
+@@ -245,9 +422,43 @@ ssh_gssapi_import_name(Gssctxt *ctx, const char *host)
+ return (ctx->major);
+ }
+
++OM_uint32
++ssh_gssapi_client_identity(Gssctxt *ctx, const char *name)
++{
++ gss_buffer_desc gssbuf;
++ gss_name_t gssname;
++ OM_uint32 status;
++ gss_OID_set oidset;
++
++ gssbuf.value = (void *) name;
++ gssbuf.length = strlen(gssbuf.value);
++
++ gss_create_empty_oid_set(&status, &oidset);
++ gss_add_oid_set_member(&status, ctx->oid, &oidset);
++
++ ctx->major = gss_import_name(&ctx->minor, &gssbuf,
++ GSS_C_NT_USER_NAME, &gssname);
++
++ if (!ctx->major)
++ ctx->major = gss_acquire_cred(&ctx->minor,
++ gssname, 0, oidset, GSS_C_INITIATE,
++ &ctx->client_creds, NULL, NULL);
++
++ gss_release_name(&status, &gssname);
++ gss_release_oid_set(&status, &oidset);
++
++ if (ctx->major)
++ ssh_gssapi_error(ctx);
++
++ return(ctx->major);
++}
++
+ OM_uint32
+ ssh_gssapi_sign(Gssctxt *ctx, gss_buffer_t buffer, gss_buffer_t hash)
+ {
++ if (ctx == NULL)
++ return -1;
++
+ if ((ctx->major = gss_get_mic(&ctx->minor, ctx->context,
+ GSS_C_QOP_DEFAULT, buffer, hash)))
+ ssh_gssapi_error(ctx);
+@@ -255,6 +466,19 @@ ssh_gssapi_sign(Gssctxt *ctx, gss_buffer_t buffer, gss_buffer_t hash)
+ return (ctx->major);
+ }
+
++/* Priviledged when used by server */
++OM_uint32
++ssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic)
++{
++ if (ctx == NULL)
++ return -1;
++
++ ctx->major = gss_verify_mic(&ctx->minor, ctx->context,
++ gssbuf, gssmic, NULL);
++
++ return (ctx->major);
++}
++
+ void
+ ssh_gssapi_buildmic(struct sshbuf *b, const char *user, const char *service,
+ const char *context, const struct sshbuf *session_id)
+@@ -271,11 +495,16 @@ ssh_gssapi_buildmic(struct sshbuf *b, const char *user, const char *service,
+ }
+
+ int
+-ssh_gssapi_check_mechanism(Gssctxt **ctx, gss_OID oid, const char *host)
++ssh_gssapi_check_mechanism(Gssctxt **ctx, gss_OID oid, const char *host,
++ const char *client)
+ {
+ gss_buffer_desc token = GSS_C_EMPTY_BUFFER;
+ OM_uint32 major, minor;
+ gss_OID_desc spnego_oid = {6, (void *)"\x2B\x06\x01\x05\x05\x02"};
++ Gssctxt *intctx = NULL;
++
++ if (ctx == NULL)
++ ctx = &intctx;
+
+ /* RFC 4462 says we MUST NOT do SPNEGO */
+ if (oid->length == spnego_oid.length &&
+@@ -285,6 +514,10 @@ ssh_gssapi_check_mechanism(Gssctxt **ctx, gss_OID oid, const char *host)
+ ssh_gssapi_build_ctx(ctx);
+ ssh_gssapi_set_oid(*ctx, oid);
+ major = ssh_gssapi_import_name(*ctx, host);
++
++ if (!GSS_ERROR(major) && client)
++ major = ssh_gssapi_client_identity(*ctx, client);
++
+ if (!GSS_ERROR(major)) {
+ major = ssh_gssapi_init_ctx(*ctx, 0, GSS_C_NO_BUFFER, &token,
+ NULL);
+@@ -294,10 +527,66 @@ ssh_gssapi_check_mechanism(Gssctxt **ctx, gss_OID oid, const char *host)
+ GSS_C_NO_BUFFER);
+ }
+
+- if (GSS_ERROR(major))
++ if (GSS_ERROR(major) || intctx != NULL)
+ ssh_gssapi_delete_ctx(ctx);
+
+ return (!GSS_ERROR(major));
+ }
+
++int
++ssh_gssapi_credentials_updated(Gssctxt *ctxt) {
++ static gss_name_t saved_name = GSS_C_NO_NAME;
++ static OM_uint32 saved_lifetime = 0;
++ static gss_OID saved_mech = GSS_C_NO_OID;
++ static gss_name_t name;
++ static OM_uint32 last_call = 0;
++ OM_uint32 lifetime, now, major, minor;
++ int equal;
++
++ now = time(NULL);
++
++ if (ctxt) {
++ debug("Rekey has happened - updating saved versions");
++
++ if (saved_name != GSS_C_NO_NAME)
++ gss_release_name(&minor, &saved_name);
++
++ major = gss_inquire_cred(&minor, GSS_C_NO_CREDENTIAL,
++ &saved_name, &saved_lifetime, NULL, NULL);
++
++ if (!GSS_ERROR(major)) {
++ saved_mech = ctxt->oid;
++ saved_lifetime+= now;
++ } else {
++ /* Handle the error */
++ }
++ return 0;
++ }
++
++ if (now - last_call < 10)
++ return 0;
++
++ last_call = now;
++
++ if (saved_mech == GSS_C_NO_OID)
++ return 0;
++
++ major = gss_inquire_cred(&minor, GSS_C_NO_CREDENTIAL,
++ &name, &lifetime, NULL, NULL);
++ if (major == GSS_S_CREDENTIALS_EXPIRED)
++ return 0;
++ else if (GSS_ERROR(major))
++ return 0;
++
++ major = gss_compare_name(&minor, saved_name, name, &equal);
++ gss_release_name(&minor, &name);
++ if (GSS_ERROR(major))
++ return 0;
++
++ if (equal && (saved_lifetime < lifetime + now - 10))
++ return 1;
++
++ return 0;
++}
++
+ #endif /* GSSAPI */
+diff --git a/gss-serv-krb5.c b/gss-serv-krb5.c
+index a151bc1e4..ef20401ec 100644
+--- a/gss-serv-krb5.c
++++ b/gss-serv-krb5.c
+@@ -1,7 +1,7 @@
+ /* $OpenBSD: gss-serv-krb5.c,v 1.9 2018/07/09 21:37:55 markus Exp $ */
+
+ /*
+- * Copyright (c) 2001-2003 Simon Wilkinson. All rights reserved.
++ * Copyright (c) 2001-2007 Simon Wilkinson. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+@@ -120,7 +120,7 @@ ssh_gssapi_krb5_storecreds(ssh_gssapi_client *client)
+ krb5_error_code problem;
+ krb5_principal princ;
+ OM_uint32 maj_status, min_status;
+- int len;
++ const char *new_ccname;
+ const char *errmsg;
+
+ if (client->creds == NULL) {
+@@ -180,11 +180,16 @@ ssh_gssapi_krb5_storecreds(ssh_gssapi_client *client)
+ return;
+ }
+
+- client->store.filename = xstrdup(krb5_cc_get_name(krb_context, ccache));
++ new_ccname = krb5_cc_get_name(krb_context, ccache);
++
+ client->store.envvar = "KRB5CCNAME";
+- len = strlen(client->store.filename) + 6;
+- client->store.envval = xmalloc(len);
+- snprintf(client->store.envval, len, "FILE:%s", client->store.filename);
++#ifdef USE_CCAPI
++ xasprintf(&client->store.envval, "API:%s", new_ccname);
++ client->store.filename = NULL;
++#else
++ xasprintf(&client->store.envval, "FILE:%s", new_ccname);
++ client->store.filename = xstrdup(new_ccname);
++#endif
+
+ #ifdef USE_PAM
+ if (options.use_pam)
+@@ -193,9 +198,76 @@ ssh_gssapi_krb5_storecreds(ssh_gssapi_client *client)
+
+ krb5_cc_close(krb_context, ccache);
+
++ client->store.data = krb_context;
++
+ return;
+ }
+
++int
++ssh_gssapi_krb5_updatecreds(ssh_gssapi_ccache *store,
++ ssh_gssapi_client *client)
++{
++ krb5_ccache ccache = NULL;
++ krb5_principal principal = NULL;
++ char *name = NULL;
++ krb5_error_code problem;
++ OM_uint32 maj_status, min_status;
++
++ if ((problem = krb5_cc_resolve(krb_context, store->envval, &ccache))) {
++ logit("krb5_cc_resolve(): %.100s",
++ krb5_get_err_text(krb_context, problem));
++ return 0;
++ }
++
++ /* Find out who the principal in this cache is */
++ if ((problem = krb5_cc_get_principal(krb_context, ccache,
++ &principal))) {
++ logit("krb5_cc_get_principal(): %.100s",
++ krb5_get_err_text(krb_context, problem));
++ krb5_cc_close(krb_context, ccache);
++ return 0;
++ }
++
++ if ((problem = krb5_unparse_name(krb_context, principal, &name))) {
++ logit("krb5_unparse_name(): %.100s",
++ krb5_get_err_text(krb_context, problem));
++ krb5_free_principal(krb_context, principal);
++ krb5_cc_close(krb_context, ccache);
++ return 0;
++ }
++
++
++ if (strcmp(name,client->exportedname.value)!=0) {
++ debug("Name in local credentials cache differs. Not storing");
++ krb5_free_principal(krb_context, principal);
++ krb5_cc_close(krb_context, ccache);
++ krb5_free_unparsed_name(krb_context, name);
++ return 0;
++ }
++ krb5_free_unparsed_name(krb_context, name);
++
++ /* Name matches, so lets get on with it! */
++
++ if ((problem = krb5_cc_initialize(krb_context, ccache, principal))) {
++ logit("krb5_cc_initialize(): %.100s",
++ krb5_get_err_text(krb_context, problem));
++ krb5_free_principal(krb_context, principal);
++ krb5_cc_close(krb_context, ccache);
++ return 0;
++ }
++
++ krb5_free_principal(krb_context, principal);
++
++ if ((maj_status = gss_krb5_copy_ccache(&min_status, client->creds,
++ ccache))) {
++ logit("gss_krb5_copy_ccache() failed. Sorry!");
++ krb5_cc_close(krb_context, ccache);
++ return 0;
++ }
++
++ return 1;
++}
++
+ ssh_gssapi_mech gssapi_kerberos_mech = {
+ "toWM5Slw5Ew8Mqkay+al2g==",
+ "Kerberos",
+@@ -203,7 +275,8 @@ ssh_gssapi_mech gssapi_kerberos_mech = {
+ NULL,
+ &ssh_gssapi_krb5_userok,
+ NULL,
+- &ssh_gssapi_krb5_storecreds
++ &ssh_gssapi_krb5_storecreds,
++ &ssh_gssapi_krb5_updatecreds
+ };
+
+ #endif /* KRB5 */
+diff --git a/gss-serv.c b/gss-serv.c
+index b5d4bb2d1..4287579ae 100644
+--- a/gss-serv.c
++++ b/gss-serv.c
+@@ -1,7 +1,7 @@
+ /* $OpenBSD: gss-serv.c,v 1.32 2020/03/13 03:17:07 djm Exp $ */
+
+ /*
+- * Copyright (c) 2001-2003 Simon Wilkinson. All rights reserved.
++ * Copyright (c) 2001-2009 Simon Wilkinson. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+@@ -44,17 +44,19 @@
+ #include "session.h"
+ #include "misc.h"
+ #include "servconf.h"
++#include "uidswap.h"
+
+ #include "ssh-gss.h"
++#include "monitor_wrap.h"
+
+ extern ServerOptions options;
+
+ static ssh_gssapi_client gssapi_client =
+- { GSS_C_EMPTY_BUFFER, GSS_C_EMPTY_BUFFER,
+- GSS_C_NO_CREDENTIAL, NULL, {NULL, NULL, NULL, NULL}};
++ { GSS_C_EMPTY_BUFFER, GSS_C_EMPTY_BUFFER, GSS_C_NO_CREDENTIAL,
++ GSS_C_NO_NAME, NULL, {NULL, NULL, NULL, NULL, NULL}, 0, 0};
+
+ ssh_gssapi_mech gssapi_null_mech =
+- { NULL, NULL, {0, NULL}, NULL, NULL, NULL, NULL};
++ { NULL, NULL, {0, NULL}, NULL, NULL, NULL, NULL, NULL};
+
+ #ifdef KRB5
+ extern ssh_gssapi_mech gssapi_kerberos_mech;
+@@ -140,6 +142,29 @@ ssh_gssapi_server_ctx(Gssctxt **ctx, gss_OID oid)
+ return (ssh_gssapi_acquire_cred(*ctx));
+ }
+
++/* Unprivileged */
++char *
++ssh_gssapi_server_mechanisms(void) {
++ if (supported_oids == NULL)
++ ssh_gssapi_prepare_supported_oids();
++ return (ssh_gssapi_kex_mechs(supported_oids,
++ &ssh_gssapi_server_check_mech, NULL, NULL,
++ options.gss_kex_algorithms));
++}
++
++/* Unprivileged */
++int
++ssh_gssapi_server_check_mech(Gssctxt **dum, gss_OID oid, const char *data,
++ const char *dummy) {
++ Gssctxt *ctx = NULL;
++ int res;
++
++ res = !GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctx, oid)));
++ ssh_gssapi_delete_ctx(&ctx);
++
++ return (res);
++}
++
+ /* Unprivileged */
+ void
+ ssh_gssapi_supported_oids(gss_OID_set *oidset)
+@@ -150,7 +175,9 @@ ssh_gssapi_supported_oids(gss_OID_set *oidset)
+ gss_OID_set supported;
+
+ gss_create_empty_oid_set(&min_status, oidset);
+- gss_indicate_mechs(&min_status, &supported);
++
++ if (GSS_ERROR(gss_indicate_mechs(&min_status, &supported)))
++ return;
+
+ while (supported_mechs[i]->name != NULL) {
+ if (GSS_ERROR(gss_test_oid_set_member(&min_status,
+@@ -276,8 +303,48 @@ OM_uint32
+ ssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client)
+ {
+ int i = 0;
++ int equal = 0;
++ gss_name_t new_name = GSS_C_NO_NAME;
++ gss_buffer_desc ename = GSS_C_EMPTY_BUFFER;
++
++ if (options.gss_store_rekey && client->used && ctx->client_creds) {
++ if (client->mech->oid.length != ctx->oid->length ||
++ (memcmp(client->mech->oid.elements,
++ ctx->oid->elements, ctx->oid->length) !=0)) {
++ debug("Rekeyed credentials have different mechanism");
++ return GSS_S_COMPLETE;
++ }
++
++ if ((ctx->major = gss_inquire_cred_by_mech(&ctx->minor,
++ ctx->client_creds, ctx->oid, &new_name,
++ NULL, NULL, NULL))) {
++ ssh_gssapi_error(ctx);
++ return (ctx->major);
++ }
+
+- gss_buffer_desc ename;
++ ctx->major = gss_compare_name(&ctx->minor, client->name,
++ new_name, &equal);
++
++ if (GSS_ERROR(ctx->major)) {
++ ssh_gssapi_error(ctx);
++ return (ctx->major);
++ }
++
++ if (!equal) {
++ debug("Rekeyed credentials have different name");
++ return GSS_S_COMPLETE;
++ }
++
++ debug("Marking rekeyed credentials for export");
++
++ gss_release_name(&ctx->minor, &client->name);
++ gss_release_cred(&ctx->minor, &client->creds);
++ client->name = new_name;
++ client->creds = ctx->client_creds;
++ ctx->client_creds = GSS_C_NO_CREDENTIAL;
++ client->updated = 1;
++ return GSS_S_COMPLETE;
++ }
+
+ client->mech = NULL;
+
+@@ -292,6 +359,13 @@ ssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client)
+ if (client->mech == NULL)
+ return GSS_S_FAILURE;
+
++ if (ctx->client_creds &&
++ (ctx->major = gss_inquire_cred_by_mech(&ctx->minor,
++ ctx->client_creds, ctx->oid, &client->name, NULL, NULL, NULL))) {
++ ssh_gssapi_error(ctx);
++ return (ctx->major);
++ }
++
+ if ((ctx->major = gss_display_name(&ctx->minor, ctx->client,
+ &client->displayname, NULL))) {
+ ssh_gssapi_error(ctx);
+@@ -309,6 +383,8 @@ ssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client)
+ return (ctx->major);
+ }
+
++ gss_release_buffer(&ctx->minor, &ename);
++
+ /* We can't copy this structure, so we just move the pointer to it */
+ client->creds = ctx->client_creds;
+ ctx->client_creds = GSS_C_NO_CREDENTIAL;
+@@ -319,11 +395,20 @@ ssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client)
+ void
+ ssh_gssapi_cleanup_creds(void)
+ {
+- if (gssapi_client.store.filename != NULL) {
+- /* Unlink probably isn't sufficient */
+- debug("removing gssapi cred file\"%s\"",
+- gssapi_client.store.filename);
+- unlink(gssapi_client.store.filename);
++ krb5_ccache ccache = NULL;
++ krb5_error_code problem;
++
++ if (gssapi_client.store.data != NULL) {
++ if ((problem = krb5_cc_resolve(gssapi_client.store.data, gssapi_client.store.envval, &ccache))) {
++ debug_f("krb5_cc_resolve(): %.100s",
++ krb5_get_err_text(gssapi_client.store.data, problem));
++ } else if ((problem = krb5_cc_destroy(gssapi_client.store.data, ccache))) {
++ debug_f("krb5_cc_destroy(): %.100s",
++ krb5_get_err_text(gssapi_client.store.data, problem));
++ } else {
++ krb5_free_context(gssapi_client.store.data);
++ gssapi_client.store.data = NULL;
++ }
+ }
+ }
+
+@@ -356,19 +441,23 @@ ssh_gssapi_do_child(char ***envp, u_int *envsizep)
+
+ /* Privileged */
+ int
+-ssh_gssapi_userok(char *user)
++ssh_gssapi_userok(char *user, struct passwd *pw, int kex)
+ {
+ OM_uint32 lmin;
+
++ (void) kex; /* used in privilege separation */
++
+ if (gssapi_client.exportedname.length == 0 ||
+ gssapi_client.exportedname.value == NULL) {
+ debug("No suitable client data");
+ return 0;
+ }
+ if (gssapi_client.mech && gssapi_client.mech->userok)
+- if ((*gssapi_client.mech->userok)(&gssapi_client, user))
++ if ((*gssapi_client.mech->userok)(&gssapi_client, user)) {
++ gssapi_client.used = 1;
++ gssapi_client.store.owner = pw;
+ return 1;
+- else {
++ } else {
+ /* Destroy delegated credentials if userok fails */
+ gss_release_buffer(&lmin, &gssapi_client.displayname);
+ gss_release_buffer(&lmin, &gssapi_client.exportedname);
+@@ -382,14 +471,90 @@ ssh_gssapi_userok(char *user)
+ return (0);
+ }
+
+-/* Privileged */
+-OM_uint32
+-ssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic)
++/* These bits are only used for rekeying. The unpriviledged child is running
++ * as the user, the monitor is root.
++ *
++ * In the child, we want to :
++ * *) Ask the monitor to store our credentials into the store we specify
++ * *) If it succeeds, maybe do a PAM update
++ */
++
++/* Stuff for PAM */
++
++#ifdef USE_PAM
++static int ssh_gssapi_simple_conv(int n, const struct pam_message **msg,
++ struct pam_response **resp, void *data)
+ {
+- ctx->major = gss_verify_mic(&ctx->minor, ctx->context,
+- gssbuf, gssmic, NULL);
++ return (PAM_CONV_ERR);
++}
++#endif
+
+- return (ctx->major);
++void
++ssh_gssapi_rekey_creds(void) {
++ int ok;
++#ifdef USE_PAM
++ int ret;
++ pam_handle_t *pamh = NULL;
++ struct pam_conv pamconv = {ssh_gssapi_simple_conv, NULL};
++ char *envstr;
++#endif
++
++ if (gssapi_client.store.filename == NULL &&
++ gssapi_client.store.envval == NULL &&
++ gssapi_client.store.envvar == NULL)
++ return;
++
++ ok = PRIVSEP(ssh_gssapi_update_creds(&gssapi_client.store));
++
++ if (!ok)
++ return;
++
++ debug("Rekeyed credentials stored successfully");
++
++ /* Actually managing to play with the ssh pam stack from here will
++ * be next to impossible. In any case, we may want different options
++ * for rekeying. So, use our own :)
++ */
++#ifdef USE_PAM
++ if (!use_privsep) {
++ debug("Not even going to try and do PAM with privsep disabled");
++ return;
++ }
++
++ ret = pam_start("sshd-rekey", gssapi_client.store.owner->pw_name,
++ &pamconv, &pamh);
++ if (ret)
++ return;
++
++ xasprintf(&envstr, "%s=%s", gssapi_client.store.envvar,
++ gssapi_client.store.envval);
++
++ ret = pam_putenv(pamh, envstr);
++ if (!ret)
++ pam_setcred(pamh, PAM_REINITIALIZE_CRED);
++ pam_end(pamh, PAM_SUCCESS);
++#endif
++}
++
++int
++ssh_gssapi_update_creds(ssh_gssapi_ccache *store) {
++ int ok = 0;
++
++ /* Check we've got credentials to store */
++ if (!gssapi_client.updated)
++ return 0;
++
++ gssapi_client.updated = 0;
++
++ temporarily_use_uid(gssapi_client.store.owner);
++ if (gssapi_client.mech && gssapi_client.mech->updatecreds)
++ ok = (*gssapi_client.mech->updatecreds)(store, &gssapi_client);
++ else
++ debug("No update function for this mechanism");
++
++ restore_uid();
++
++ return ok;
+ }
+
+ /* Privileged */
+diff --git a/kex.c b/kex.c
+index 8cdefcf7c..c259e00fc 100644
+--- a/kex.c
++++ b/kex.c
+@@ -57,11 +57,16 @@
+ #include "misc.h"
+ #include "dispatch.h"
+ #include "monitor.h"
++#include "xmalloc.h"
+
+ #include "ssherr.h"
+ #include "sshbuf.h"
+ #include "digest.h"
+
++#ifdef GSSAPI
++#include "ssh-gss.h"
++#endif
++
+ /* prototype */
+ static int kex_choose_conf(struct ssh *);
+ static int kex_input_newkeys(int, u_int32_t, struct ssh *);
+@@ -117,15 +122,28 @@ static const struct kexalg kexalgs[] = {
+ #endif /* HAVE_EVP_SHA256 || !WITH_OPENSSL */
+ { NULL, 0, -1, -1},
+ };
++static const struct kexalg gss_kexalgs[] = {
++#ifdef GSSAPI
++ { KEX_GSS_GEX_SHA1_ID, KEX_GSS_GEX_SHA1, 0, SSH_DIGEST_SHA1 },
++ { KEX_GSS_GRP1_SHA1_ID, KEX_GSS_GRP1_SHA1, 0, SSH_DIGEST_SHA1 },
++ { KEX_GSS_GRP14_SHA1_ID, KEX_GSS_GRP14_SHA1, 0, SSH_DIGEST_SHA1 },
++ { KEX_GSS_GRP14_SHA256_ID, KEX_GSS_GRP14_SHA256, 0, SSH_DIGEST_SHA256 },
++ { KEX_GSS_GRP16_SHA512_ID, KEX_GSS_GRP16_SHA512, 0, SSH_DIGEST_SHA512 },
++ { KEX_GSS_NISTP256_SHA256_ID, KEX_GSS_NISTP256_SHA256,
++ NID_X9_62_prime256v1, SSH_DIGEST_SHA256 },
++ { KEX_GSS_C25519_SHA256_ID, KEX_GSS_C25519_SHA256, 0, SSH_DIGEST_SHA256 },
++#endif
++ { NULL, 0, -1, -1},
++};
+
+-char *
+-kex_alg_list(char sep)
++static char *
++kex_alg_list_internal(char sep, const struct kexalg *algs)
+ {
+ char *ret = NULL, *tmp;
+ size_t nlen, rlen = 0;
+ const struct kexalg *k;
+
+- for (k = kexalgs; k->name != NULL; k++) {
++ for (k = algs; k->name != NULL; k++) {
+ if (ret != NULL)
+ ret[rlen++] = sep;
+ nlen = strlen(k->name);
+@@ -140,6 +158,18 @@ kex_alg_list(char sep)
+ return ret;
+ }
+
++char *
++kex_alg_list(char sep)
++{
++ return kex_alg_list_internal(sep, kexalgs);
++}
++
++char *
++kex_gss_alg_list(char sep)
++{
++ return kex_alg_list_internal(sep, gss_kexalgs);
++}
++
+ static const struct kexalg *
+ kex_alg_by_name(const char *name)
+ {
+@@ -149,6 +179,10 @@ kex_alg_by_name(const char *name)
+ if (strcmp(k->name, name) == 0)
+ return k;
+ }
++ for (k = gss_kexalgs; k->name != NULL; k++) {
++ if (strncmp(k->name, name, strlen(k->name)) == 0)
++ return k;
++ }
+ return NULL;
+ }
+
+@@ -317,6 +351,29 @@ kex_assemble_names(char **listp, const char *def, const char *all)
+ return r;
+ }
+
++/* Validate GSS KEX method name list */
++int
++kex_gss_names_valid(const char *names)
++{
++ char *s, *cp, *p;
++
++ if (names == NULL || *names == '\0')
++ return 0;
++ s = cp = xstrdup(names);
++ for ((p = strsep(&cp, ",")); p && *p != '\0';
++ (p = strsep(&cp, ","))) {
++ if (strncmp(p, "gss-", 4) != 0
++ || kex_alg_by_name(p) == NULL) {
++ error("Unsupported KEX algorithm \"%.100s\"", p);
++ free(s);
++ return 0;
++ }
++ }
++ debug3("gss kex names ok: [%s]", names);
++ free(s);
++ return 1;
++}
++
+ /* put algorithm proposal into buffer */
+ int
+ kex_prop2buf(struct sshbuf *b, char *proposal[PROPOSAL_MAX])
+@@ -719,6 +776,9 @@ kex_free(struct kex *kex)
+ sshbuf_free(kex->session_id);
+ sshbuf_free(kex->initial_sig);
+ sshkey_free(kex->initial_hostkey);
++#ifdef GSSAPI
++ free(kex->gss_host);
++#endif /* GSSAPI */
+ free(kex->failed_choice);
+ free(kex->hostkey_alg);
+ free(kex->name);
+diff --git a/kex.h b/kex.h
+index c35329501..240dca89d 100644
+--- a/kex.h
++++ b/kex.h
+@@ -102,6 +102,15 @@ enum kex_exchange {
+ KEX_ECDH_SHA2,
+ KEX_C25519_SHA256,
+ KEX_KEM_SNTRUP761X25519_SHA512,
++#ifdef GSSAPI
++ KEX_GSS_GRP1_SHA1,
++ KEX_GSS_GRP14_SHA1,
++ KEX_GSS_GRP14_SHA256,
++ KEX_GSS_GRP16_SHA512,
++ KEX_GSS_GEX_SHA1,
++ KEX_GSS_NISTP256_SHA256,
++ KEX_GSS_C25519_SHA256,
++#endif
+ KEX_MAX
+ };
+
+@@ -159,6 +168,12 @@ struct kex {
+ u_int flags;
+ int hash_alg;
+ int ec_nid;
++#ifdef GSSAPI
++ int gss_deleg_creds;
++ int gss_trust_dns;
++ char *gss_host;
++ char *gss_client;
++#endif
+ char *failed_choice;
+ int (*verify_host_key)(struct sshkey *, struct ssh *);
+ struct sshkey *(*load_host_public_key)(int, int, struct ssh *);
+@@ -180,8 +195,10 @@ struct kex {
+
+ int kex_names_valid(const char *);
+ char *kex_alg_list(char);
++char *kex_gss_alg_list(char);
+ char *kex_names_cat(const char *, const char *);
+ int kex_assemble_names(char **, const char *, const char *);
++int kex_gss_names_valid(const char *);
+
+ int kex_exchange_identification(struct ssh *, int, const char *);
+
+@@ -209,6 +226,12 @@ int kexgex_client(struct ssh *);
+ int kexgex_server(struct ssh *);
+ int kex_gen_client(struct ssh *);
+ int kex_gen_server(struct ssh *);
++#if defined(GSSAPI) && defined(WITH_OPENSSL)
++int kexgssgex_client(struct ssh *);
++int kexgssgex_server(struct ssh *);
++int kexgss_client(struct ssh *);
++int kexgss_server(struct ssh *);
++#endif
+
+ int kex_dh_keypair(struct kex *);
+ int kex_dh_enc(struct kex *, const struct sshbuf *, struct sshbuf **,
+@@ -241,6 +264,12 @@ int kexgex_hash(int, const struct sshbuf *, const struct sshbuf *,
+ const BIGNUM *, const u_char *, size_t,
+ u_char *, size_t *);
+
++int kex_gen_hash(int hash_alg, const struct sshbuf *client_version,
++ const struct sshbuf *server_version, const struct sshbuf *client_kexinit,
++ const struct sshbuf *server_kexinit, const struct sshbuf *server_host_key_blob,
++ const struct sshbuf *client_pub, const struct sshbuf *server_pub,
++ const struct sshbuf *shared_secret, u_char *hash, size_t *hashlen);
++
+ void kexc25519_keygen(u_char key[CURVE25519_SIZE], u_char pub[CURVE25519_SIZE])
+ __attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE)))
+ __attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE)));
+diff --git a/kexdh.c b/kexdh.c
+index c1084f214..0faab21b0 100644
+--- a/kexdh.c
++++ b/kexdh.c
+@@ -49,13 +49,23 @@ kex_dh_keygen(struct kex *kex)
+ {
+ switch (kex->kex_type) {
+ case KEX_DH_GRP1_SHA1:
++#ifdef GSSAPI
++ case KEX_GSS_GRP1_SHA1:
++#endif
+ kex->dh = dh_new_group1();
+ break;
+ case KEX_DH_GRP14_SHA1:
+ case KEX_DH_GRP14_SHA256:
++#ifdef GSSAPI
++ case KEX_GSS_GRP14_SHA1:
++ case KEX_GSS_GRP14_SHA256:
++#endif
+ kex->dh = dh_new_group14();
+ break;
+ case KEX_DH_GRP16_SHA512:
++#ifdef GSSAPI
++ case KEX_GSS_GRP16_SHA512:
++#endif
+ kex->dh = dh_new_group16();
+ break;
+ case KEX_DH_GRP18_SHA512:
+diff --git a/kexgen.c b/kexgen.c
+index 20f3c5711..ca704844e 100644
+--- a/kexgen.c
++++ b/kexgen.c
+@@ -44,7 +44,7 @@
+ static int input_kex_gen_init(int, u_int32_t, struct ssh *);
+ static int input_kex_gen_reply(int type, u_int32_t seq, struct ssh *ssh);
+
+-static int
++int
+ kex_gen_hash(
+ int hash_alg,
+ const struct sshbuf *client_version,
+diff --git a/kexgssc.c b/kexgssc.c
+new file mode 100644
+index 000000000..1c62740e7
+--- /dev/null
++++ b/kexgssc.c
+@@ -0,0 +1,599 @@
++/*
++ * Copyright (c) 2001-2009 Simon Wilkinson. All rights reserved.
++ *
++ * Redistribution and use in source and binary forms, with or without
++ * modification, are permitted provided that the following conditions
++ * are met:
++ * 1. Redistributions of source code must retain the above copyright
++ * notice, this list of conditions and the following disclaimer.
++ * 2. Redistributions in binary form must reproduce the above copyright
++ * notice, this list of conditions and the following disclaimer in the
++ * documentation and/or other materials provided with the distribution.
++ *
++ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR
++ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
++ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
++ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
++ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
++ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
++ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
++ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
++ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
++ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
++ */
++
++#include "includes.h"
++
++#if defined(GSSAPI) && defined(WITH_OPENSSL)
++
++#include "includes.h"
++
++#include <openssl/crypto.h>
++#include <openssl/bn.h>
++
++#include <string.h>
++
++#include "xmalloc.h"
++#include "sshbuf.h"
++#include "ssh2.h"
++#include "sshkey.h"
++#include "cipher.h"
++#include "kex.h"
++#include "log.h"
++#include "packet.h"
++#include "dh.h"
++#include "digest.h"
++#include "ssherr.h"
++
++#include "ssh-gss.h"
++
++int
++kexgss_client(struct ssh *ssh)
++{
++ struct kex *kex = ssh->kex;
++ gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER,
++ recv_tok = GSS_C_EMPTY_BUFFER,
++ gssbuf, msg_tok = GSS_C_EMPTY_BUFFER, *token_ptr;
++ Gssctxt *ctxt;
++ OM_uint32 maj_status, min_status, ret_flags;
++ struct sshbuf *server_blob = NULL;
++ struct sshbuf *shared_secret = NULL;
++ struct sshbuf *server_host_key_blob = NULL;
++ struct sshbuf *empty = NULL;
++ u_char *msg;
++ int type = 0;
++ int first = 1;
++ u_char hash[SSH_DIGEST_MAX_LENGTH];
++ size_t hashlen;
++ u_char c;
++ int r;
++
++ /* Initialise our GSSAPI world */
++ ssh_gssapi_build_ctx(&ctxt);
++ if (ssh_gssapi_id_kex(ctxt, kex->name, kex->kex_type)
++ == GSS_C_NO_OID)
++ fatal("Couldn't identify host exchange");
++
++ if (ssh_gssapi_import_name(ctxt, kex->gss_host))
++ fatal("Couldn't import hostname");
++
++ if (kex->gss_client &&
++ ssh_gssapi_client_identity(ctxt, kex->gss_client))
++ fatal("Couldn't acquire client credentials");
++
++ /* Step 1 */
++ switch (kex->kex_type) {
++ case KEX_GSS_GRP1_SHA1:
++ case KEX_GSS_GRP14_SHA1:
++ case KEX_GSS_GRP14_SHA256:
++ case KEX_GSS_GRP16_SHA512:
++ r = kex_dh_keypair(kex);
++ break;
++ case KEX_GSS_NISTP256_SHA256:
++ r = kex_ecdh_keypair(kex);
++ break;
++ case KEX_GSS_C25519_SHA256:
++ r = kex_c25519_keypair(kex);
++ break;
++ default:
++ fatal_f("Unexpected KEX type %d", kex->kex_type);
++ }
++ if (r != 0)
++ return r;
++
++ token_ptr = GSS_C_NO_BUFFER;
++
++ do {
++ debug("Calling gss_init_sec_context");
++
++ maj_status = ssh_gssapi_init_ctx(ctxt,
++ kex->gss_deleg_creds, token_ptr, &send_tok,
++ &ret_flags);
++
++ if (GSS_ERROR(maj_status)) {
++ /* XXX Useles code: Missing send? */
++ if (send_tok.length != 0) {
++ if ((r = sshpkt_start(ssh,
++ SSH2_MSG_KEXGSS_CONTINUE)) != 0 ||
++ (r = sshpkt_put_string(ssh, send_tok.value,
++ send_tok.length)) != 0)
++ fatal("sshpkt failed: %s", ssh_err(r));
++ }
++ fatal("gss_init_context failed");
++ }
++
++ /* If we've got an old receive buffer get rid of it */
++ if (token_ptr != GSS_C_NO_BUFFER)
++ gss_release_buffer(&min_status, &recv_tok);
++
++ if (maj_status == GSS_S_COMPLETE) {
++ /* If mutual state flag is not true, kex fails */
++ if (!(ret_flags & GSS_C_MUTUAL_FLAG))
++ fatal("Mutual authentication failed");
++
++ /* If integ avail flag is not true kex fails */
++ if (!(ret_flags & GSS_C_INTEG_FLAG))
++ fatal("Integrity check failed");
++ }
++
++ /*
++ * If we have data to send, then the last message that we
++ * received cannot have been a 'complete'.
++ */
++ if (send_tok.length != 0) {
++ if (first) {
++ if ((r = sshpkt_start(ssh, SSH2_MSG_KEXGSS_INIT)) != 0 ||
++ (r = sshpkt_put_string(ssh, send_tok.value,
++ send_tok.length)) != 0 ||
++ (r = sshpkt_put_stringb(ssh, kex->client_pub)) != 0)
++ fatal("failed to construct packet: %s", ssh_err(r));
++ first = 0;
++ } else {
++ if ((r = sshpkt_start(ssh, SSH2_MSG_KEXGSS_CONTINUE)) != 0 ||
++ (r = sshpkt_put_string(ssh, send_tok.value,
++ send_tok.length)) != 0)
++ fatal("failed to construct packet: %s", ssh_err(r));
++ }
++ if ((r = sshpkt_send(ssh)) != 0)
++ fatal("failed to send packet: %s", ssh_err(r));
++ gss_release_buffer(&min_status, &send_tok);
++
++ /* If we've sent them data, they should reply */
++ do {
++ type = ssh_packet_read(ssh);
++ if (type == SSH2_MSG_KEXGSS_HOSTKEY) {
++ debug("Received KEXGSS_HOSTKEY");
++ if (server_host_key_blob)
++ fatal("Server host key received more than once");
++ if ((r = sshpkt_getb_froms(ssh, &server_host_key_blob)) != 0)
++ fatal("Failed to read server host key: %s", ssh_err(r));
++ }
++ } while (type == SSH2_MSG_KEXGSS_HOSTKEY);
++
++ switch (type) {
++ case SSH2_MSG_KEXGSS_CONTINUE:
++ debug("Received GSSAPI_CONTINUE");
++ if (maj_status == GSS_S_COMPLETE)
++ fatal("GSSAPI Continue received from server when complete");
++ if ((r = ssh_gssapi_sshpkt_get_buffer_desc(ssh,
++ &recv_tok)) != 0 ||
++ (r = sshpkt_get_end(ssh)) != 0)
++ fatal("Failed to read token: %s", ssh_err(r));
++ break;
++ case SSH2_MSG_KEXGSS_COMPLETE:
++ debug("Received GSSAPI_COMPLETE");
++ if (msg_tok.value != NULL)
++ fatal("Received GSSAPI_COMPLETE twice?");
++ if ((r = sshpkt_getb_froms(ssh, &server_blob)) != 0 ||
++ (r = ssh_gssapi_sshpkt_get_buffer_desc(ssh,
++ &msg_tok)) != 0)
++ fatal("Failed to read message: %s", ssh_err(r));
++
++ /* Is there a token included? */
++ if ((r = sshpkt_get_u8(ssh, &c)) != 0)
++ fatal("sshpkt failed: %s", ssh_err(r));
++ if (c) {
++ if ((r = ssh_gssapi_sshpkt_get_buffer_desc(
++ ssh, &recv_tok)) != 0)
++ fatal("Failed to read token: %s", ssh_err(r));
++ /* If we're already complete - protocol error */
++ if (maj_status == GSS_S_COMPLETE)
++ sshpkt_disconnect(ssh, "Protocol error: received token when complete");
++ } else {
++ /* No token included */
++ if (maj_status != GSS_S_COMPLETE)
++ sshpkt_disconnect(ssh, "Protocol error: did not receive final token");
++ }
++ if ((r = sshpkt_get_end(ssh)) != 0) {
++ fatal("Expecting end of packet.");
++ }
++ break;
++ case SSH2_MSG_KEXGSS_ERROR:
++ debug("Received Error");
++ if ((r = sshpkt_get_u32(ssh, &maj_status)) != 0 ||
++ (r = sshpkt_get_u32(ssh, &min_status)) != 0 ||
++ (r = sshpkt_get_string(ssh, &msg, NULL)) != 0 ||
++ (r = sshpkt_get_string(ssh, NULL, NULL)) != 0 || /* lang tag */
++ (r = sshpkt_get_end(ssh)) != 0)
++ fatal("sshpkt_get failed: %s", ssh_err(r));
++ fatal("GSSAPI Error: \n%.400s", msg);
++ default:
++ sshpkt_disconnect(ssh, "Protocol error: didn't expect packet type %d",
++ type);
++ }
++ token_ptr = &recv_tok;
++ } else {
++ /* No data, and not complete */
++ if (maj_status != GSS_S_COMPLETE)
++ fatal("Not complete, and no token output");
++ }
++ } while (maj_status & GSS_S_CONTINUE_NEEDED);
++
++ /*
++ * We _must_ have received a COMPLETE message in reply from the
++ * server, which will have set server_blob and msg_tok
++ */
++
++ if (type != SSH2_MSG_KEXGSS_COMPLETE)
++ fatal("Didn't receive a SSH2_MSG_KEXGSS_COMPLETE when I expected it");
++
++ /* compute shared secret */
++ switch (kex->kex_type) {
++ case KEX_GSS_GRP1_SHA1:
++ case KEX_GSS_GRP14_SHA1:
++ case KEX_GSS_GRP14_SHA256:
++ case KEX_GSS_GRP16_SHA512:
++ r = kex_dh_dec(kex, server_blob, &shared_secret);
++ break;
++ case KEX_GSS_C25519_SHA256:
++ if (sshbuf_ptr(server_blob)[sshbuf_len(server_blob)] & 0x80)
++ fatal("The received key has MSB of last octet set!");
++ r = kex_c25519_dec(kex, server_blob, &shared_secret);
++ break;
++ case KEX_GSS_NISTP256_SHA256:
++ if (sshbuf_len(server_blob) != 65)
++ fatal("The received NIST-P256 key did not match"
++ "expected length (expected 65, got %zu)", sshbuf_len(server_blob));
++
++ if (sshbuf_ptr(server_blob)[0] != POINT_CONVERSION_UNCOMPRESSED)
++ fatal("The received NIST-P256 key does not have first octet 0x04");
++
++ r = kex_ecdh_dec(kex, server_blob, &shared_secret);
++ break;
++ default:
++ r = SSH_ERR_INVALID_ARGUMENT;
++ break;
++ }
++ if (r != 0)
++ goto out;
++
++ if ((empty = sshbuf_new()) == NULL) {
++ r = SSH_ERR_ALLOC_FAIL;
++ goto out;
++ }
++
++ hashlen = sizeof(hash);
++ if ((r = kex_gen_hash(
++ kex->hash_alg,
++ kex->client_version,
++ kex->server_version,
++ kex->my,
++ kex->peer,
++ (server_host_key_blob ? server_host_key_blob : empty),
++ kex->client_pub,
++ server_blob,
++ shared_secret,
++ hash, &hashlen)) != 0)
++ fatal_f("Unexpected KEX type %d", kex->kex_type);
++
++ gssbuf.value = hash;
++ gssbuf.length = hashlen;
++
++ /* Verify that the hash matches the MIC we just got. */
++ if (GSS_ERROR(ssh_gssapi_checkmic(ctxt, &gssbuf, &msg_tok)))
++ sshpkt_disconnect(ssh, "Hash's MIC didn't verify");
++
++ gss_release_buffer(&min_status, &msg_tok);
++
++ if (kex->gss_deleg_creds)
++ ssh_gssapi_credentials_updated(ctxt);
++
++ if (gss_kex_context == NULL)
++ gss_kex_context = ctxt;
++ else
++ ssh_gssapi_delete_ctx(&ctxt);
++
++ if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0)
++ r = kex_send_newkeys(ssh);
++
++out:
++ explicit_bzero(hash, sizeof(hash));
++ explicit_bzero(kex->c25519_client_key, sizeof(kex->c25519_client_key));
++ sshbuf_free(empty);
++ sshbuf_free(server_host_key_blob);
++ sshbuf_free(server_blob);
++ sshbuf_free(shared_secret);
++ sshbuf_free(kex->client_pub);
++ kex->client_pub = NULL;
++ return r;
++}
++
++int
++kexgssgex_client(struct ssh *ssh)
++{
++ struct kex *kex = ssh->kex;
++ gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER,
++ recv_tok = GSS_C_EMPTY_BUFFER, gssbuf,
++ msg_tok = GSS_C_EMPTY_BUFFER, *token_ptr;
++ Gssctxt *ctxt;
++ OM_uint32 maj_status, min_status, ret_flags;
++ struct sshbuf *shared_secret = NULL;
++ BIGNUM *p = NULL;
++ BIGNUM *g = NULL;
++ struct sshbuf *buf = NULL;
++ struct sshbuf *server_host_key_blob = NULL;
++ struct sshbuf *server_blob = NULL;
++ BIGNUM *dh_server_pub = NULL;
++ u_char *msg;
++ int type = 0;
++ int first = 1;
++ u_char hash[SSH_DIGEST_MAX_LENGTH];
++ size_t hashlen;
++ const BIGNUM *pub_key, *dh_p, *dh_g;
++ int nbits = 0, min = DH_GRP_MIN, max = DH_GRP_MAX;
++ struct sshbuf *empty = NULL;
++ u_char c;
++ int r;
++
++ /* Initialise our GSSAPI world */
++ ssh_gssapi_build_ctx(&ctxt);
++ if (ssh_gssapi_id_kex(ctxt, kex->name, kex->kex_type)
++ == GSS_C_NO_OID)
++ fatal("Couldn't identify host exchange");
++
++ if (ssh_gssapi_import_name(ctxt, kex->gss_host))
++ fatal("Couldn't import hostname");
++
++ if (kex->gss_client &&
++ ssh_gssapi_client_identity(ctxt, kex->gss_client))
++ fatal("Couldn't acquire client credentials");
++
++ debug("Doing group exchange");
++ nbits = dh_estimate(kex->dh_need * 8);
++
++ kex->min = DH_GRP_MIN;
++ kex->max = DH_GRP_MAX;
++ kex->nbits = nbits;
++ if ((r = sshpkt_start(ssh, SSH2_MSG_KEXGSS_GROUPREQ)) != 0 ||
++ (r = sshpkt_put_u32(ssh, min)) != 0 ||
++ (r = sshpkt_put_u32(ssh, nbits)) != 0 ||
++ (r = sshpkt_put_u32(ssh, max)) != 0 ||
++ (r = sshpkt_send(ssh)) != 0)
++ fatal("Failed to construct a packet: %s", ssh_err(r));
++
++ if ((r = ssh_packet_read_expect(ssh, SSH2_MSG_KEXGSS_GROUP)) != 0)
++ fatal("Error: %s", ssh_err(r));
++
++ if ((r = sshpkt_get_bignum2(ssh, &p)) != 0 ||
++ (r = sshpkt_get_bignum2(ssh, &g)) != 0 ||
++ (r = sshpkt_get_end(ssh)) != 0)
++ fatal("shpkt_get_bignum2 failed: %s", ssh_err(r));
++
++ if (BN_num_bits(p) < min || BN_num_bits(p) > max)
++ fatal("GSSGRP_GEX group out of range: %d !< %d !< %d",
++ min, BN_num_bits(p), max);
++
++ if ((kex->dh = dh_new_group(g, p)) == NULL)
++ fatal("dn_new_group() failed");
++ p = g = NULL; /* belong to kex->dh now */
++
++ if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0)
++ goto out;
++ DH_get0_key(kex->dh, &pub_key, NULL);
++
++ token_ptr = GSS_C_NO_BUFFER;
++
++ do {
++ /* Step 2 - call GSS_Init_sec_context() */
++ debug("Calling gss_init_sec_context");
++
++ maj_status = ssh_gssapi_init_ctx(ctxt,
++ kex->gss_deleg_creds, token_ptr, &send_tok,
++ &ret_flags);
++
++ if (GSS_ERROR(maj_status)) {
++ /* XXX Useles code: Missing send? */
++ if (send_tok.length != 0) {
++ if ((r = sshpkt_start(ssh,
++ SSH2_MSG_KEXGSS_CONTINUE)) != 0 ||
++ (r = sshpkt_put_string(ssh, send_tok.value,
++ send_tok.length)) != 0)
++ fatal("sshpkt failed: %s", ssh_err(r));
++ }
++ fatal("gss_init_context failed");
++ }
++
++ /* If we've got an old receive buffer get rid of it */
++ if (token_ptr != GSS_C_NO_BUFFER)
++ gss_release_buffer(&min_status, &recv_tok);
++
++ if (maj_status == GSS_S_COMPLETE) {
++ /* If mutual state flag is not true, kex fails */
++ if (!(ret_flags & GSS_C_MUTUAL_FLAG))
++ fatal("Mutual authentication failed");
++
++ /* If integ avail flag is not true kex fails */
++ if (!(ret_flags & GSS_C_INTEG_FLAG))
++ fatal("Integrity check failed");
++ }
++
++ /*
++ * If we have data to send, then the last message that we
++ * received cannot have been a 'complete'.
++ */
++ if (send_tok.length != 0) {
++ if (first) {
++ if ((r = sshpkt_start(ssh, SSH2_MSG_KEXGSS_INIT)) != 0 ||
++ (r = sshpkt_put_string(ssh, send_tok.value,
++ send_tok.length)) != 0 ||
++ (r = sshpkt_put_bignum2(ssh, pub_key)) != 0)
++ fatal("sshpkt failed: %s", ssh_err(r));
++ first = 0;
++ } else {
++ if ((r = sshpkt_start(ssh, SSH2_MSG_KEXGSS_CONTINUE)) != 0 ||
++ (r = sshpkt_put_string(ssh,send_tok.value,
++ send_tok.length)) != 0)
++ fatal("sshpkt failed: %s", ssh_err(r));
++ }
++ if ((r = sshpkt_send(ssh)) != 0)
++ fatal("sshpkt_send failed: %s", ssh_err(r));
++ gss_release_buffer(&min_status, &send_tok);
++
++ /* If we've sent them data, they should reply */
++ do {
++ type = ssh_packet_read(ssh);
++ if (type == SSH2_MSG_KEXGSS_HOSTKEY) {
++ debug("Received KEXGSS_HOSTKEY");
++ if (server_host_key_blob)
++ fatal("Server host key received more than once");
++ if ((r = sshpkt_getb_froms(ssh, &server_host_key_blob)) != 0)
++ fatal("sshpkt failed: %s", ssh_err(r));
++ }
++ } while (type == SSH2_MSG_KEXGSS_HOSTKEY);
++
++ switch (type) {
++ case SSH2_MSG_KEXGSS_CONTINUE:
++ debug("Received GSSAPI_CONTINUE");
++ if (maj_status == GSS_S_COMPLETE)
++ fatal("GSSAPI Continue received from server when complete");
++ if ((r = ssh_gssapi_sshpkt_get_buffer_desc(ssh,
++ &recv_tok)) != 0 ||
++ (r = sshpkt_get_end(ssh)) != 0)
++ fatal("sshpkt failed: %s", ssh_err(r));
++ break;
++ case SSH2_MSG_KEXGSS_COMPLETE:
++ debug("Received GSSAPI_COMPLETE");
++ if (msg_tok.value != NULL)
++ fatal("Received GSSAPI_COMPLETE twice?");
++ if ((r = sshpkt_getb_froms(ssh, &server_blob)) != 0 ||
++ (r = ssh_gssapi_sshpkt_get_buffer_desc(ssh,
++ &msg_tok)) != 0)
++ fatal("sshpkt failed: %s", ssh_err(r));
++
++ /* Is there a token included? */
++ if ((r = sshpkt_get_u8(ssh, &c)) != 0)
++ fatal("sshpkt failed: %s", ssh_err(r));
++ if (c) {
++ if ((r = ssh_gssapi_sshpkt_get_buffer_desc(
++ ssh, &recv_tok)) != 0 ||
++ (r = sshpkt_get_end(ssh)) != 0)
++ fatal("sshpkt failed: %s", ssh_err(r));
++ /* If we're already complete - protocol error */
++ if (maj_status == GSS_S_COMPLETE)
++ sshpkt_disconnect(ssh, "Protocol error: received token when complete");
++ } else {
++ /* No token included */
++ if (maj_status != GSS_S_COMPLETE)
++ sshpkt_disconnect(ssh, "Protocol error: did not receive final token");
++ }
++ break;
++ case SSH2_MSG_KEXGSS_ERROR:
++ debug("Received Error");
++ if ((r = sshpkt_get_u32(ssh, &maj_status)) != 0 ||
++ (r = sshpkt_get_u32(ssh, &min_status)) != 0 ||
++ (r = sshpkt_get_string(ssh, &msg, NULL)) != 0 ||
++ (r = sshpkt_get_string(ssh, NULL, NULL)) != 0 || /* lang tag */
++ (r = sshpkt_get_end(ssh)) != 0)
++ fatal("sshpkt failed: %s", ssh_err(r));
++ fatal("GSSAPI Error: \n%.400s", msg);
++ default:
++ sshpkt_disconnect(ssh, "Protocol error: didn't expect packet type %d",
++ type);
++ }
++ token_ptr = &recv_tok;
++ } else {
++ /* No data, and not complete */
++ if (maj_status != GSS_S_COMPLETE)
++ fatal("Not complete, and no token output");
++ }
++ } while (maj_status & GSS_S_CONTINUE_NEEDED);
++
++ /*
++ * We _must_ have received a COMPLETE message in reply from the
++ * server, which will have set dh_server_pub and msg_tok
++ */
++
++ if (type != SSH2_MSG_KEXGSS_COMPLETE)
++ fatal("Didn't receive a SSH2_MSG_KEXGSS_COMPLETE when I expected it");
++
++ /* 7. C verifies that the key Q_S is valid */
++ /* 8. C computes shared secret */
++ if ((buf = sshbuf_new()) == NULL ||
++ (r = sshbuf_put_stringb(buf, server_blob)) != 0 ||
++ (r = sshbuf_get_bignum2(buf, &dh_server_pub)) != 0)
++ goto out;
++ sshbuf_free(buf);
++ buf = NULL;
++
++ if ((shared_secret = sshbuf_new()) == NULL) {
++ r = SSH_ERR_ALLOC_FAIL;
++ goto out;
++ }
++
++ if ((r = kex_dh_compute_key(kex, dh_server_pub, shared_secret)) != 0)
++ goto out;
++ if ((empty = sshbuf_new()) == NULL) {
++ r = SSH_ERR_ALLOC_FAIL;
++ goto out;
++ }
++
++ DH_get0_pqg(kex->dh, &dh_p, NULL, &dh_g);
++ hashlen = sizeof(hash);
++ if ((r = kexgex_hash(
++ kex->hash_alg,
++ kex->client_version,
++ kex->server_version,
++ kex->my,
++ kex->peer,
++ (server_host_key_blob ? server_host_key_blob : empty),
++ kex->min, kex->nbits, kex->max,
++ dh_p, dh_g,
++ pub_key,
++ dh_server_pub,
++ sshbuf_ptr(shared_secret), sshbuf_len(shared_secret),
++ hash, &hashlen)) != 0)
++ fatal("Failed to calculate hash: %s", ssh_err(r));
++
++ gssbuf.value = hash;
++ gssbuf.length = hashlen;
++
++ /* Verify that the hash matches the MIC we just got. */
++ if (GSS_ERROR(ssh_gssapi_checkmic(ctxt, &gssbuf, &msg_tok)))
++ sshpkt_disconnect(ssh, "Hash's MIC didn't verify");
++
++ gss_release_buffer(&min_status, &msg_tok);
++
++ if (kex->gss_deleg_creds)
++ ssh_gssapi_credentials_updated(ctxt);
++
++ if (gss_kex_context == NULL)
++ gss_kex_context = ctxt;
++ else
++ ssh_gssapi_delete_ctx(&ctxt);
++
++ /* Finally derive the keys and send them */
++ if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0)
++ r = kex_send_newkeys(ssh);
++out:
++ sshbuf_free(buf);
++ sshbuf_free(server_blob);
++ sshbuf_free(empty);
++ explicit_bzero(hash, sizeof(hash));
++ DH_free(kex->dh);
++ kex->dh = NULL;
++ BN_clear_free(dh_server_pub);
++ sshbuf_free(shared_secret);
++ sshbuf_free(server_host_key_blob);
++ return r;
++}
++#endif /* defined(GSSAPI) && defined(WITH_OPENSSL) */
+diff --git a/kexgsss.c b/kexgsss.c
+new file mode 100644
+index 000000000..a2c02148b
+--- /dev/null
++++ b/kexgsss.c
+@@ -0,0 +1,474 @@
++/*
++ * Copyright (c) 2001-2009 Simon Wilkinson. All rights reserved.
++ *
++ * Redistribution and use in source and binary forms, with or without
++ * modification, are permitted provided that the following conditions
++ * are met:
++ * 1. Redistributions of source code must retain the above copyright
++ * notice, this list of conditions and the following disclaimer.
++ * 2. Redistributions in binary form must reproduce the above copyright
++ * notice, this list of conditions and the following disclaimer in the
++ * documentation and/or other materials provided with the distribution.
++ *
++ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR
++ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
++ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
++ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
++ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
++ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
++ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
++ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
++ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
++ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
++ */
++
++#include "includes.h"
++
++#if defined(GSSAPI) && defined(WITH_OPENSSL)
++
++#include <string.h>
++
++#include <openssl/crypto.h>
++#include <openssl/bn.h>
++
++#include "xmalloc.h"
++#include "sshbuf.h"
++#include "ssh2.h"
++#include "sshkey.h"
++#include "cipher.h"
++#include "kex.h"
++#include "log.h"
++#include "packet.h"
++#include "dh.h"
++#include "ssh-gss.h"
++#include "monitor_wrap.h"
++#include "misc.h" /* servconf.h needs misc.h for struct ForwardOptions */
++#include "servconf.h"
++#include "ssh-gss.h"
++#include "digest.h"
++#include "ssherr.h"
++
++extern ServerOptions options;
++
++int
++kexgss_server(struct ssh *ssh)
++{
++ struct kex *kex = ssh->kex;
++ OM_uint32 maj_status, min_status;
++
++ /*
++ * Some GSSAPI implementations use the input value of ret_flags (an
++ * output variable) as a means of triggering mechanism specific
++ * features. Initializing it to zero avoids inadvertently
++ * activating this non-standard behaviour.
++ */
++
++ OM_uint32 ret_flags = 0;
++ gss_buffer_desc gssbuf, recv_tok, msg_tok;
++ gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
++ Gssctxt *ctxt = NULL;
++ struct sshbuf *shared_secret = NULL;
++ struct sshbuf *client_pubkey = NULL;
++ struct sshbuf *server_pubkey = NULL;
++ struct sshbuf *empty = sshbuf_new();
++ int type = 0;
++ gss_OID oid;
++ char *mechs;
++ u_char hash[SSH_DIGEST_MAX_LENGTH];
++ size_t hashlen;
++ int r;
++
++ /* Initialise GSSAPI */
++
++ /* If we're rekeying, privsep means that some of the private structures
++ * in the GSSAPI code are no longer available. This kludges them back
++ * into life
++ */
++ if (!ssh_gssapi_oid_table_ok()) {
++ mechs = ssh_gssapi_server_mechanisms();
++ free(mechs);
++ }
++
++ debug2_f("Identifying %s", kex->name);
++ oid = ssh_gssapi_id_kex(NULL, kex->name, kex->kex_type);
++ if (oid == GSS_C_NO_OID)
++ fatal("Unknown gssapi mechanism");
++
++ debug2_f("Acquiring credentials");
++
++ if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, oid))))
++ fatal("Unable to acquire credentials for the server");
++
++ do {
++ debug("Wait SSH2_MSG_KEXGSS_INIT");
++ type = ssh_packet_read(ssh);
++ switch(type) {
++ case SSH2_MSG_KEXGSS_INIT:
++ if (client_pubkey != NULL)
++ fatal("Received KEXGSS_INIT after initialising");
++ if ((r = ssh_gssapi_sshpkt_get_buffer_desc(ssh,
++ &recv_tok)) != 0 ||
++ (r = sshpkt_getb_froms(ssh, &client_pubkey)) != 0 ||
++ (r = sshpkt_get_end(ssh)) != 0)
++ fatal("sshpkt failed: %s", ssh_err(r));
++
++ switch (kex->kex_type) {
++ case KEX_GSS_GRP1_SHA1:
++ case KEX_GSS_GRP14_SHA1:
++ case KEX_GSS_GRP14_SHA256:
++ case KEX_GSS_GRP16_SHA512:
++ r = kex_dh_enc(kex, client_pubkey, &server_pubkey,
++ &shared_secret);
++ break;
++ case KEX_GSS_NISTP256_SHA256:
++ r = kex_ecdh_enc(kex, client_pubkey, &server_pubkey,
++ &shared_secret);
++ break;
++ case KEX_GSS_C25519_SHA256:
++ r = kex_c25519_enc(kex, client_pubkey, &server_pubkey,
++ &shared_secret);
++ break;
++ default:
++ fatal_f("Unexpected KEX type %d", kex->kex_type);
++ }
++ if (r != 0)
++ goto out;
++
++ /* Send SSH_MSG_KEXGSS_HOSTKEY here, if we want */
++ break;
++ case SSH2_MSG_KEXGSS_CONTINUE:
++ if ((r = ssh_gssapi_sshpkt_get_buffer_desc(ssh,
++ &recv_tok)) != 0 ||
++ (r = sshpkt_get_end(ssh)) != 0)
++ fatal("sshpkt failed: %s", ssh_err(r));
++ break;
++ default:
++ sshpkt_disconnect(ssh,
++ "Protocol error: didn't expect packet type %d",
++ type);
++ }
++
++ maj_status = PRIVSEP(ssh_gssapi_accept_ctx(ctxt, &recv_tok,
++ &send_tok, &ret_flags));
++
++ gss_release_buffer(&min_status, &recv_tok);
++
++ if (maj_status != GSS_S_COMPLETE && send_tok.length == 0)
++ fatal("Zero length token output when incomplete");
++
++ if (client_pubkey == NULL)
++ fatal("No client public key");
++
++ if (maj_status & GSS_S_CONTINUE_NEEDED) {
++ debug("Sending GSSAPI_CONTINUE");
++ if ((r = sshpkt_start(ssh, SSH2_MSG_KEXGSS_CONTINUE)) != 0 ||
++ (r = sshpkt_put_string(ssh, send_tok.value, send_tok.length)) != 0 ||
++ (r = sshpkt_send(ssh)) != 0)
++ fatal("sshpkt failed: %s", ssh_err(r));
++ gss_release_buffer(&min_status, &send_tok);
++ }
++ } while (maj_status & GSS_S_CONTINUE_NEEDED);
++
++ if (GSS_ERROR(maj_status)) {
++ if (send_tok.length > 0) {
++ if ((r = sshpkt_start(ssh, SSH2_MSG_KEXGSS_CONTINUE)) != 0 ||
++ (r = sshpkt_put_string(ssh, send_tok.value, send_tok.length)) != 0 ||
++ (r = sshpkt_send(ssh)) != 0)
++ fatal("sshpkt failed: %s", ssh_err(r));
++ }
++ fatal("accept_ctx died");
++ }
++
++ if (!(ret_flags & GSS_C_MUTUAL_FLAG))
++ fatal("Mutual Authentication flag wasn't set");
++
++ if (!(ret_flags & GSS_C_INTEG_FLAG))
++ fatal("Integrity flag wasn't set");
++
++ hashlen = sizeof(hash);
++ if ((r = kex_gen_hash(
++ kex->hash_alg,
++ kex->client_version,
++ kex->server_version,
++ kex->peer,
++ kex->my,
++ empty,
++ client_pubkey,
++ server_pubkey,
++ shared_secret,
++ hash, &hashlen)) != 0)
++ goto out;
++
++ gssbuf.value = hash;
++ gssbuf.length = hashlen;
++
++ if (GSS_ERROR(PRIVSEP(ssh_gssapi_sign(ctxt, &gssbuf, &msg_tok))))
++ fatal("Couldn't get MIC");
++
++ if ((r = sshpkt_start(ssh, SSH2_MSG_KEXGSS_COMPLETE)) != 0 ||
++ (r = sshpkt_put_stringb(ssh, server_pubkey)) != 0 ||
++ (r = sshpkt_put_string(ssh, msg_tok.value, msg_tok.length)) != 0)
++ fatal("sshpkt failed: %s", ssh_err(r));
++
++ if (send_tok.length != 0) {
++ if ((r = sshpkt_put_u8(ssh, 1)) != 0 || /* true */
++ (r = sshpkt_put_string(ssh, send_tok.value, send_tok.length)) != 0)
++ fatal("sshpkt failed: %s", ssh_err(r));
++ } else {
++ if ((r = sshpkt_put_u8(ssh, 0)) != 0) /* false */
++ fatal("sshpkt failed: %s", ssh_err(r));
++ }
++ if ((r = sshpkt_send(ssh)) != 0)
++ fatal("sshpkt_send failed: %s", ssh_err(r));
++
++ gss_release_buffer(&min_status, &send_tok);
++ gss_release_buffer(&min_status, &msg_tok);
++
++ if (gss_kex_context == NULL)
++ gss_kex_context = ctxt;
++ else
++ ssh_gssapi_delete_ctx(&ctxt);
++
++ if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0)
++ r = kex_send_newkeys(ssh);
++
++ /* If this was a rekey, then save out any delegated credentials we
++ * just exchanged. */
++ if (options.gss_store_rekey)
++ ssh_gssapi_rekey_creds();
++out:
++ sshbuf_free(empty);
++ explicit_bzero(hash, sizeof(hash));
++ sshbuf_free(shared_secret);
++ sshbuf_free(client_pubkey);
++ sshbuf_free(server_pubkey);
++ return r;
++}
++
++int
++kexgssgex_server(struct ssh *ssh)
++{
++ struct kex *kex = ssh->kex;
++ OM_uint32 maj_status, min_status;
++
++ /*
++ * Some GSSAPI implementations use the input value of ret_flags (an
++ * output variable) as a means of triggering mechanism specific
++ * features. Initializing it to zero avoids inadvertently
++ * activating this non-standard behaviour.
++ */
++
++ OM_uint32 ret_flags = 0;
++ gss_buffer_desc gssbuf, recv_tok, msg_tok;
++ gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
++ Gssctxt *ctxt = NULL;
++ struct sshbuf *shared_secret = NULL;
++ int type = 0;
++ gss_OID oid;
++ char *mechs;
++ u_char hash[SSH_DIGEST_MAX_LENGTH];
++ size_t hashlen;
++ BIGNUM *dh_client_pub = NULL;
++ const BIGNUM *pub_key, *dh_p, *dh_g;
++ int min = -1, max = -1, nbits = -1;
++ int cmin = -1, cmax = -1; /* client proposal */
++ struct sshbuf *empty = sshbuf_new();
++ int r;
++
++ /* Initialise GSSAPI */
++
++ /* If we're rekeying, privsep means that some of the private structures
++ * in the GSSAPI code are no longer available. This kludges them back
++ * into life
++ */
++ if (!ssh_gssapi_oid_table_ok())
++ if ((mechs = ssh_gssapi_server_mechanisms()))
++ free(mechs);
++
++ debug2_f("Identifying %s", kex->name);
++ oid = ssh_gssapi_id_kex(NULL, kex->name, kex->kex_type);
++ if (oid == GSS_C_NO_OID)
++ fatal("Unknown gssapi mechanism");
++
++ debug2_f("Acquiring credentials");
++
++ if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, oid))))
++ fatal("Unable to acquire credentials for the server");
++
++ /* 5. S generates an ephemeral key pair (do the allocations early) */
++ debug("Doing group exchange");
++ ssh_packet_read_expect(ssh, SSH2_MSG_KEXGSS_GROUPREQ);
++ /* store client proposal to provide valid signature */
++ if ((r = sshpkt_get_u32(ssh, &cmin)) != 0 ||
++ (r = sshpkt_get_u32(ssh, &nbits)) != 0 ||
++ (r = sshpkt_get_u32(ssh, &cmax)) != 0 ||
++ (r = sshpkt_get_end(ssh)) != 0)
++ fatal("sshpkt failed: %s", ssh_err(r));
++ kex->nbits = nbits;
++ kex->min = cmin;
++ kex->max = cmax;
++ min = MAX(DH_GRP_MIN, cmin);
++ max = MIN(DH_GRP_MAX, cmax);
++ nbits = MAXIMUM(DH_GRP_MIN, nbits);
++ nbits = MINIMUM(DH_GRP_MAX, nbits);
++ if (max < min || nbits < min || max < nbits)
++ fatal("GSS_GEX, bad parameters: %d !< %d !< %d",
++ min, nbits, max);
++ kex->dh = PRIVSEP(choose_dh(min, nbits, max));
++ if (kex->dh == NULL) {
++ sshpkt_disconnect(ssh, "Protocol error: no matching group found");
++ fatal("Protocol error: no matching group found");
++ }
++
++ DH_get0_pqg(kex->dh, &dh_p, NULL, &dh_g);
++ if ((r = sshpkt_start(ssh, SSH2_MSG_KEXGSS_GROUP)) != 0 ||
++ (r = sshpkt_put_bignum2(ssh, dh_p)) != 0 ||
++ (r = sshpkt_put_bignum2(ssh, dh_g)) != 0 ||
++ (r = sshpkt_send(ssh)) != 0)
++ fatal("sshpkt failed: %s", ssh_err(r));
++
++ if ((r = ssh_packet_write_wait(ssh)) != 0)
++ fatal("ssh_packet_write_wait: %s", ssh_err(r));
++
++ /* Compute our exchange value in parallel with the client */
++ if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0)
++ goto out;
++
++ do {
++ debug("Wait SSH2_MSG_GSSAPI_INIT");
++ type = ssh_packet_read(ssh);
++ switch(type) {
++ case SSH2_MSG_KEXGSS_INIT:
++ if (dh_client_pub != NULL)
++ fatal("Received KEXGSS_INIT after initialising");
++ if ((r = ssh_gssapi_sshpkt_get_buffer_desc(ssh,
++ &recv_tok)) != 0 ||
++ (r = sshpkt_get_bignum2(ssh, &dh_client_pub)) != 0 ||
++ (r = sshpkt_get_end(ssh)) != 0)
++ fatal("sshpkt failed: %s", ssh_err(r));
++
++ /* Send SSH_MSG_KEXGSS_HOSTKEY here, if we want */
++ break;
++ case SSH2_MSG_KEXGSS_CONTINUE:
++ if ((r = ssh_gssapi_sshpkt_get_buffer_desc(ssh,
++ &recv_tok)) != 0 ||
++ (r = sshpkt_get_end(ssh)) != 0)
++ fatal("sshpkt failed: %s", ssh_err(r));
++ break;
++ default:
++ sshpkt_disconnect(ssh,
++ "Protocol error: didn't expect packet type %d",
++ type);
++ }
++
++ maj_status = PRIVSEP(ssh_gssapi_accept_ctx(ctxt, &recv_tok,
++ &send_tok, &ret_flags));
++
++ gss_release_buffer(&min_status, &recv_tok);
++
++ if (maj_status != GSS_S_COMPLETE && send_tok.length == 0)
++ fatal("Zero length token output when incomplete");
++
++ if (dh_client_pub == NULL)
++ fatal("No client public key");
++
++ if (maj_status & GSS_S_CONTINUE_NEEDED) {
++ debug("Sending GSSAPI_CONTINUE");
++ if ((r = sshpkt_start(ssh, SSH2_MSG_KEXGSS_CONTINUE)) != 0 ||
++ (r = sshpkt_put_string(ssh, send_tok.value, send_tok.length)) != 0 ||
++ (r = sshpkt_send(ssh)) != 0)
++ fatal("sshpkt failed: %s", ssh_err(r));
++ gss_release_buffer(&min_status, &send_tok);
++ }
++ } while (maj_status & GSS_S_CONTINUE_NEEDED);
++
++ if (GSS_ERROR(maj_status)) {
++ if (send_tok.length > 0) {
++ if ((r = sshpkt_start(ssh, SSH2_MSG_KEXGSS_CONTINUE)) != 0 ||
++ (r = sshpkt_put_string(ssh, send_tok.value, send_tok.length)) != 0 ||
++ (r = sshpkt_send(ssh)) != 0)
++ fatal("sshpkt failed: %s", ssh_err(r));
++ }
++ fatal("accept_ctx died");
++ }
++
++ if (!(ret_flags & GSS_C_MUTUAL_FLAG))
++ fatal("Mutual Authentication flag wasn't set");
++
++ if (!(ret_flags & GSS_C_INTEG_FLAG))
++ fatal("Integrity flag wasn't set");
++
++ /* calculate shared secret */
++ if ((shared_secret = sshbuf_new()) == NULL) {
++ r = SSH_ERR_ALLOC_FAIL;
++ goto out;
++ }
++ if ((r = kex_dh_compute_key(kex, dh_client_pub, shared_secret)) != 0)
++ goto out;
++
++ DH_get0_key(kex->dh, &pub_key, NULL);
++ DH_get0_pqg(kex->dh, &dh_p, NULL, &dh_g);
++ hashlen = sizeof(hash);
++ if ((r = kexgex_hash(
++ kex->hash_alg,
++ kex->client_version,
++ kex->server_version,
++ kex->peer,
++ kex->my,
++ empty,
++ cmin, nbits, cmax,
++ dh_p, dh_g,
++ dh_client_pub,
++ pub_key,
++ sshbuf_ptr(shared_secret), sshbuf_len(shared_secret),
++ hash, &hashlen)) != 0)
++ fatal("kexgex_hash failed: %s", ssh_err(r));
++
++ gssbuf.value = hash;
++ gssbuf.length = hashlen;
++
++ if (GSS_ERROR(PRIVSEP(ssh_gssapi_sign(ctxt, &gssbuf, &msg_tok))))
++ fatal("Couldn't get MIC");
++
++ if ((r = sshpkt_start(ssh, SSH2_MSG_KEXGSS_COMPLETE)) != 0 ||
++ (r = sshpkt_put_bignum2(ssh, pub_key)) != 0 ||
++ (r = sshpkt_put_string(ssh, msg_tok.value, msg_tok.length)) != 0)
++ fatal("sshpkt failed: %s", ssh_err(r));
++
++ if (send_tok.length != 0) {
++ if ((r = sshpkt_put_u8(ssh, 1)) != 0 || /* true */
++ (r = sshpkt_put_string(ssh, send_tok.value, send_tok.length)) != 0)
++ fatal("sshpkt failed: %s", ssh_err(r));
++ } else {
++ if ((r = sshpkt_put_u8(ssh, 0)) != 0) /* false */
++ fatal("sshpkt failed: %s", ssh_err(r));
++ }
++ if ((r = sshpkt_send(ssh)) != 0)
++ fatal("sshpkt failed: %s", ssh_err(r));
++
++ gss_release_buffer(&min_status, &send_tok);
++ gss_release_buffer(&min_status, &msg_tok);
++
++ if (gss_kex_context == NULL)
++ gss_kex_context = ctxt;
++ else
++ ssh_gssapi_delete_ctx(&ctxt);
++
++ /* Finally derive the keys and send them */
++ if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0)
++ r = kex_send_newkeys(ssh);
++
++ /* If this was a rekey, then save out any delegated credentials we
++ * just exchanged. */
++ if (options.gss_store_rekey)
++ ssh_gssapi_rekey_creds();
++out:
++ sshbuf_free(empty);
++ explicit_bzero(hash, sizeof(hash));
++ DH_free(kex->dh);
++ kex->dh = NULL;
++ BN_clear_free(dh_client_pub);
++ sshbuf_free(shared_secret);
++ return r;
++}
++#endif /* defined(GSSAPI) && defined(WITH_OPENSSL) */
+diff --git a/monitor.c b/monitor.c
+index 91e0e6245..5f7df9539 100644
+--- a/monitor.c
++++ b/monitor.c
+@@ -145,6 +145,8 @@ int mm_answer_gss_setup_ctx(struct ssh *, int, struct sshbuf *);
+ int mm_answer_gss_accept_ctx(struct ssh *, int, struct sshbuf *);
+ int mm_answer_gss_userok(struct ssh *, int, struct sshbuf *);
+ int mm_answer_gss_checkmic(struct ssh *, int, struct sshbuf *);
++int mm_answer_gss_sign(struct ssh *, int, struct sshbuf *);
++int mm_answer_gss_updatecreds(struct ssh *, int, struct sshbuf *);
+ #endif
+
+ #ifdef SSH_AUDIT_EVENTS
+@@ -217,11 +219,18 @@ struct mon_table mon_dispatch_proto20[] = {
+ {MONITOR_REQ_GSSSTEP, 0, mm_answer_gss_accept_ctx},
+ {MONITOR_REQ_GSSUSEROK, MON_ONCE|MON_AUTHDECIDE, mm_answer_gss_userok},
+ {MONITOR_REQ_GSSCHECKMIC, MON_ONCE, mm_answer_gss_checkmic},
++ {MONITOR_REQ_GSSSIGN, MON_ONCE, mm_answer_gss_sign},
+ #endif
+ {0, 0, NULL}
+ };
+
+ struct mon_table mon_dispatch_postauth20[] = {
++#ifdef GSSAPI
++ {MONITOR_REQ_GSSSETUP, 0, mm_answer_gss_setup_ctx},
++ {MONITOR_REQ_GSSSTEP, 0, mm_answer_gss_accept_ctx},
++ {MONITOR_REQ_GSSSIGN, 0, mm_answer_gss_sign},
++ {MONITOR_REQ_GSSUPCREDS, 0, mm_answer_gss_updatecreds},
++#endif
+ #ifdef WITH_OPENSSL
+ {MONITOR_REQ_MODULI, 0, mm_answer_moduli},
+ #endif
+@@ -290,6 +299,10 @@ monitor_child_preauth(struct ssh *ssh, struct monitor *pmonitor)
+ /* Permit requests for moduli and signatures */
+ monitor_permit(mon_dispatch, MONITOR_REQ_MODULI, 1);
+ monitor_permit(mon_dispatch, MONITOR_REQ_SIGN, 1);
++#ifdef GSSAPI
++ /* and for the GSSAPI key exchange */
++ monitor_permit(mon_dispatch, MONITOR_REQ_GSSSETUP, 1);
++#endif
+
+ /* The first few requests do not require asynchronous access */
+ while (!authenticated) {
+@@ -401,6 +414,10 @@ monitor_child_postauth(struct ssh *ssh, struct monitor *pmonitor)
+ monitor_permit(mon_dispatch, MONITOR_REQ_MODULI, 1);
+ monitor_permit(mon_dispatch, MONITOR_REQ_SIGN, 1);
+ monitor_permit(mon_dispatch, MONITOR_REQ_TERM, 1);
++#ifdef GSSAPI
++ /* and for the GSSAPI key exchange */
++ monitor_permit(mon_dispatch, MONITOR_REQ_GSSSETUP, 1);
++#endif
+
+ if (auth_opts->permit_pty_flag) {
+ monitor_permit(mon_dispatch, MONITOR_REQ_PTY, 1);
+@@ -1744,6 +1761,17 @@ monitor_apply_keystate(struct ssh *ssh, struct monitor *pmonitor)
+ # ifdef OPENSSL_HAS_ECC
+ kex->kex[KEX_ECDH_SHA2] = kex_gen_server;
+ # endif
++# ifdef GSSAPI
++ if (options.gss_keyex) {
++ kex->kex[KEX_GSS_GRP1_SHA1] = kexgss_server;
++ kex->kex[KEX_GSS_GRP14_SHA1] = kexgss_server;
++ kex->kex[KEX_GSS_GRP14_SHA256] = kexgss_server;
++ kex->kex[KEX_GSS_GRP16_SHA512] = kexgss_server;
++ kex->kex[KEX_GSS_GEX_SHA1] = kexgssgex_server;
++ kex->kex[KEX_GSS_NISTP256_SHA256] = kexgss_server;
++ kex->kex[KEX_GSS_C25519_SHA256] = kexgss_server;
++ }
++# endif
+ #endif /* WITH_OPENSSL */
+ kex->kex[KEX_C25519_SHA256] = kex_gen_server;
+ kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_server;
+@@ -1836,8 +1864,8 @@ mm_answer_gss_setup_ctx(struct ssh *ssh, int sock, struct sshbuf *m)
+ u_char *p;
+ int r;
+
+- if (!options.gss_authentication)
+- fatal_f("GSSAPI authentication not enabled");
++ if (!options.gss_authentication && !options.gss_keyex)
++ fatal_f("GSSAPI not enabled");
+
+ if ((r = sshbuf_get_string(m, &p, &len)) != 0)
+ fatal_fr(r, "parse");
+@@ -1869,8 +1897,8 @@ mm_answer_gss_accept_ctx(struct ssh *ssh, int sock, struct sshbuf *m)
+ OM_uint32 flags = 0; /* GSI needs this */
+ int r;
+
+- if (!options.gss_authentication)
+- fatal_f("GSSAPI authentication not enabled");
++ if (!options.gss_authentication && !options.gss_keyex)
++ fatal_f("GSSAPI not enabled");
+
+ if ((r = ssh_gssapi_get_buffer_desc(m, &in)) != 0)
+ fatal_fr(r, "ssh_gssapi_get_buffer_desc");
+@@ -1890,6 +1918,7 @@ mm_answer_gss_accept_ctx(struct ssh *ssh, int sock, struct sshbuf *m)
+ monitor_permit(mon_dispatch, MONITOR_REQ_GSSSTEP, 0);
+ monitor_permit(mon_dispatch, MONITOR_REQ_GSSUSEROK, 1);
+ monitor_permit(mon_dispatch, MONITOR_REQ_GSSCHECKMIC, 1);
++ monitor_permit(mon_dispatch, MONITOR_REQ_GSSSIGN, 1);
+ }
+ return (0);
+ }
+@@ -1901,8 +1930,8 @@ mm_answer_gss_checkmic(struct ssh *ssh, int sock, struct sshbuf *m)
+ OM_uint32 ret;
+ int r;
+
+- if (!options.gss_authentication)
+- fatal_f("GSSAPI authentication not enabled");
++ if (!options.gss_authentication && !options.gss_keyex)
++ fatal_f("GSSAPI not enabled");
+
+ if ((r = ssh_gssapi_get_buffer_desc(m, &gssbuf)) != 0 ||
+ (r = ssh_gssapi_get_buffer_desc(m, &mic)) != 0)
+@@ -1928,13 +1957,17 @@ mm_answer_gss_checkmic(struct ssh *ssh, int sock, struct sshbuf *m)
+ int
+ mm_answer_gss_userok(struct ssh *ssh, int sock, struct sshbuf *m)
+ {
+- int r, authenticated;
++ int r, authenticated, kex;
+ const char *displayname;
+
+- if (!options.gss_authentication)
+- fatal_f("GSSAPI authentication not enabled");
++ if (!options.gss_authentication && !options.gss_keyex)
++ fatal_f("GSSAPI not enabled");
+
+- authenticated = authctxt->valid && ssh_gssapi_userok(authctxt->user);
++ if ((r = sshbuf_get_u32(m, &kex)) != 0)
++ fatal_fr(r, "buffer error");
++
++ authenticated = authctxt->valid &&
++ ssh_gssapi_userok(authctxt->user, authctxt->pw, kex);
+
+ sshbuf_reset(m);
+ if ((r = sshbuf_put_u32(m, authenticated)) != 0)
+@@ -1943,7 +1976,11 @@ mm_answer_gss_userok(struct ssh *ssh, int sock, struct sshbuf *m)
+ debug3_f("sending result %d", authenticated);
+ mm_request_send(sock, MONITOR_ANS_GSSUSEROK, m);
+
+- auth_method = "gssapi-with-mic";
++ if (kex) {
++ auth_method = "gssapi-keyex";
++ } else {
++ auth_method = "gssapi-with-mic";
++ }
+
+ if ((displayname = ssh_gssapi_displayname()) != NULL)
+ auth2_record_info(authctxt, "%s", displayname);
+@@ -1951,5 +1988,83 @@ mm_answer_gss_userok(struct ssh *ssh, int sock, struct sshbuf *m)
+ /* Monitor loop will terminate if authenticated */
+ return (authenticated);
+ }
+-#endif /* GSSAPI */
+
++int
++mm_answer_gss_sign(struct ssh *ssh, int socket, struct sshbuf *m)
++{
++ gss_buffer_desc data;
++ gss_buffer_desc hash = GSS_C_EMPTY_BUFFER;
++ OM_uint32 major, minor;
++ size_t len;
++ u_char *p = NULL;
++ int r;
++
++ if (!options.gss_authentication && !options.gss_keyex)
++ fatal_f("GSSAPI not enabled");
++
++ if ((r = sshbuf_get_string(m, &p, &len)) != 0)
++ fatal_fr(r, "buffer error");
++ data.value = p;
++ data.length = len;
++ /* Lengths of SHA-1, SHA-256 and SHA-512 hashes that are used */
++ if (data.length != 20 && data.length != 32 && data.length != 64)
++ fatal_f("data length incorrect: %d", (int) data.length);
++
++ /* Save the session ID on the first time around */
++ if (session_id2_len == 0) {
++ session_id2_len = data.length;
++ session_id2 = xmalloc(session_id2_len);
++ memcpy(session_id2, data.value, session_id2_len);
++ }
++ major = ssh_gssapi_sign(gsscontext, &data, &hash);
++
++ free(data.value);
++
++ sshbuf_reset(m);
++
++ if ((r = sshbuf_put_u32(m, major)) != 0 ||
++ (r = sshbuf_put_string(m, hash.value, hash.length)) != 0)
++ fatal_fr(r, "buffer error");
++
++ mm_request_send(socket, MONITOR_ANS_GSSSIGN, m);
++
++ gss_release_buffer(&minor, &hash);
++
++ /* Turn on getpwnam permissions */
++ monitor_permit(mon_dispatch, MONITOR_REQ_PWNAM, 1);
++
++ /* And credential updating, for when rekeying */
++ monitor_permit(mon_dispatch, MONITOR_REQ_GSSUPCREDS, 1);
++
++ return (0);
++}
++
++int
++mm_answer_gss_updatecreds(struct ssh *ssh, int socket, struct sshbuf *m) {
++ ssh_gssapi_ccache store;
++ int r, ok;
++
++ if (!options.gss_authentication && !options.gss_keyex)
++ fatal_f("GSSAPI not enabled");
++
++ if ((r = sshbuf_get_string(m, (u_char **)&store.filename, NULL)) != 0 ||
++ (r = sshbuf_get_string(m, (u_char **)&store.envvar, NULL)) != 0 ||
++ (r = sshbuf_get_string(m, (u_char **)&store.envval, NULL)) != 0)
++ fatal_fr(r, "buffer error");
++
++ ok = ssh_gssapi_update_creds(&store);
++
++ free(store.filename);
++ free(store.envvar);
++ free(store.envval);
++
++ sshbuf_reset(m);
++ if ((r = sshbuf_put_u32(m, ok)) != 0)
++ fatal_fr(r, "buffer error");
++
++ mm_request_send(socket, MONITOR_ANS_GSSUPCREDS, m);
++
++ return(0);
++}
++
++#endif /* GSSAPI */
+diff --git a/monitor.h b/monitor.h
+index 683e5e071..2b1a2d590 100644
+--- a/monitor.h
++++ b/monitor.h
+@@ -63,6 +63,8 @@ enum monitor_reqtype {
+ MONITOR_REQ_PAM_FREE_CTX = 110, MONITOR_ANS_PAM_FREE_CTX = 111,
+ MONITOR_REQ_AUDIT_EVENT = 112, MONITOR_REQ_AUDIT_COMMAND = 113,
+
++ MONITOR_REQ_GSSSIGN = 150, MONITOR_ANS_GSSSIGN = 151,
++ MONITOR_REQ_GSSUPCREDS = 152, MONITOR_ANS_GSSUPCREDS = 153,
+ };
+
+ struct ssh;
+diff --git a/monitor_wrap.c b/monitor_wrap.c
+index 8e379a15c..a4b66c56f 100644
+--- a/monitor_wrap.c
++++ b/monitor_wrap.c
+@@ -1000,13 +1000,15 @@ mm_ssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic)
+ }
+
+ int
+-mm_ssh_gssapi_userok(char *user)
++mm_ssh_gssapi_userok(char *user, struct passwd *pw, int kex)
+ {
+ struct sshbuf *m;
+ int r, authenticated = 0;
+
+ if ((m = sshbuf_new()) == NULL)
+ fatal_f("sshbuf_new failed");
++ if ((r = sshbuf_put_u32(m, kex)) != 0)
++ fatal_fr(r, "buffer error");
+
+ mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_GSSUSEROK, m);
+ mm_request_receive_expect(pmonitor->m_recvfd,
+@@ -1019,4 +1021,57 @@ mm_ssh_gssapi_userok(char *user)
+ debug3_f("user %sauthenticated", authenticated ? "" : "not ");
+ return (authenticated);
+ }
++
++OM_uint32
++mm_ssh_gssapi_sign(Gssctxt *ctx, gss_buffer_desc *data, gss_buffer_desc *hash)
++{
++ struct sshbuf *m;
++ OM_uint32 major;
++ int r;
++
++ if ((m = sshbuf_new()) == NULL)
++ fatal_f("sshbuf_new failed");
++ if ((r = sshbuf_put_string(m, data->value, data->length)) != 0)
++ fatal_fr(r, "buffer error");
++
++ mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_GSSSIGN, m);
++ mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_GSSSIGN, m);
++
++ if ((r = sshbuf_get_u32(m, &major)) != 0 ||
++ (r = ssh_gssapi_get_buffer_desc(m, hash)) != 0)
++ fatal_fr(r, "buffer error");
++
++ sshbuf_free(m);
++
++ return (major);
++}
++
++int
++mm_ssh_gssapi_update_creds(ssh_gssapi_ccache *store)
++{
++ struct sshbuf *m;
++ int r, ok;
++
++ if ((m = sshbuf_new()) == NULL)
++ fatal_f("sshbuf_new failed");
++
++ if ((r = sshbuf_put_cstring(m,
++ store->filename ? store->filename : "")) != 0 ||
++ (r = sshbuf_put_cstring(m,
++ store->envvar ? store->envvar : "")) != 0 ||
++ (r = sshbuf_put_cstring(m,
++ store->envval ? store->envval : "")) != 0)
++ fatal_fr(r, "buffer error");
++
++ mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_GSSUPCREDS, m);
++ mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_GSSUPCREDS, m);
++
++ if ((r = sshbuf_get_u32(m, &ok)) != 0)
++ fatal_fr(r, "buffer error");
++
++ sshbuf_free(m);
++
++ return (ok);
++}
++
+ #endif /* GSSAPI */
+diff --git a/monitor_wrap.h b/monitor_wrap.h
+index 0df49c25b..830fdb308 100644
+--- a/monitor_wrap.h
++++ b/monitor_wrap.h
+@@ -65,8 +65,10 @@ int mm_sshkey_verify(const struct sshkey *, const u_char *, size_t,
+ OM_uint32 mm_ssh_gssapi_server_ctx(Gssctxt **, gss_OID);
+ OM_uint32 mm_ssh_gssapi_accept_ctx(Gssctxt *,
+ gss_buffer_desc *, gss_buffer_desc *, OM_uint32 *);
+-int mm_ssh_gssapi_userok(char *user);
++int mm_ssh_gssapi_userok(char *user, struct passwd *, int kex);
+ OM_uint32 mm_ssh_gssapi_checkmic(Gssctxt *, gss_buffer_t, gss_buffer_t);
++OM_uint32 mm_ssh_gssapi_sign(Gssctxt *, gss_buffer_t, gss_buffer_t);
++int mm_ssh_gssapi_update_creds(ssh_gssapi_ccache *);
+ #endif
+
+ #ifdef USE_PAM
+diff --git a/readconf.c b/readconf.c
+index cf7949884..55af0115d 100644
+--- a/readconf.c
++++ b/readconf.c
+@@ -67,6 +67,7 @@
+ #include "uidswap.h"
+ #include "myproposal.h"
+ #include "digest.h"
++#include "ssh-gss.h"
+
+ /* Format of the configuration file:
+
+@@ -161,6 +162,8 @@ typedef enum {
+ oClearAllForwardings, oNoHostAuthenticationForLocalhost,
+ oEnableSSHKeysign, oRekeyLimit, oVerifyHostKeyDNS, oConnectTimeout,
+ oAddressFamily, oGssAuthentication, oGssDelegateCreds,
++ oGssTrustDns, oGssKeyEx, oGssClientIdentity, oGssRenewalRekey,
++ oGssServerIdentity, oGssKexAlgorithms,
+ oServerAliveInterval, oServerAliveCountMax, oIdentitiesOnly,
+ oSendEnv, oSetEnv, oControlPath, oControlMaster, oControlPersist,
+ oHashKnownHosts,
+@@ -207,10 +210,22 @@ static struct {
+ /* Sometimes-unsupported options */
+ #if defined(GSSAPI)
+ { "gssapiauthentication", oGssAuthentication },
++ { "gssapikeyexchange", oGssKeyEx },
+ { "gssapidelegatecredentials", oGssDelegateCreds },
++ { "gssapitrustdns", oGssTrustDns },
++ { "gssapiclientidentity", oGssClientIdentity },
++ { "gssapiserveridentity", oGssServerIdentity },
++ { "gssapirenewalforcesrekey", oGssRenewalRekey },
++ { "gssapikexalgorithms", oGssKexAlgorithms },
+ # else
+ { "gssapiauthentication", oUnsupported },
++ { "gssapikeyexchange", oUnsupported },
+ { "gssapidelegatecredentials", oUnsupported },
++ { "gssapitrustdns", oUnsupported },
++ { "gssapiclientidentity", oUnsupported },
++ { "gssapiserveridentity", oUnsupported },
++ { "gssapirenewalforcesrekey", oUnsupported },
++ { "gssapikexalgorithms", oUnsupported },
+ #endif
+ #ifdef ENABLE_PKCS11
+ { "pkcs11provider", oPKCS11Provider },
+@@ -1122,10 +1137,46 @@ parse_time:
+ intptr = &options->gss_authentication;
+ goto parse_flag;
+
++ case oGssKeyEx:
++ intptr = &options->gss_keyex;
++ goto parse_flag;
++
+ case oGssDelegateCreds:
+ intptr = &options->gss_deleg_creds;
+ goto parse_flag;
+
++ case oGssTrustDns:
++ intptr = &options->gss_trust_dns;
++ goto parse_flag;
++
++ case oGssClientIdentity:
++ charptr = &options->gss_client_identity;
++ goto parse_string;
++
++ case oGssServerIdentity:
++ charptr = &options->gss_server_identity;
++ goto parse_string;
++
++ case oGssRenewalRekey:
++ intptr = &options->gss_renewal_rekey;
++ goto parse_flag;
++
++ case oGssKexAlgorithms:
++ arg = argv_next(&ac, &av);
++ if (!arg || *arg == '\0') {
++ error("%.200s line %d: Missing argument.",
++ filename, linenum);
++ goto out;
++ }
++ if (!kex_gss_names_valid(arg)) {
++ error("%.200s line %d: Bad GSSAPI KexAlgorithms '%s'.",
++ filename, linenum, arg ? arg : "<NONE>");
++ goto out;
++ }
++ if (*activep && options->gss_kex_algorithms == NULL)
++ options->gss_kex_algorithms = xstrdup(arg);
++ break;
++
+ case oBatchMode:
+ intptr = &options->batch_mode;
+ goto parse_flag;
+@@ -2343,7 +2394,13 @@ initialize_options(Options * options)
+ options->fwd_opts.streamlocal_bind_unlink = -1;
+ options->pubkey_authentication = -1;
+ options->gss_authentication = -1;
++ options->gss_keyex = -1;
+ options->gss_deleg_creds = -1;
++ options->gss_trust_dns = -1;
++ options->gss_renewal_rekey = -1;
++ options->gss_client_identity = NULL;
++ options->gss_server_identity = NULL;
++ options->gss_kex_algorithms = NULL;
+ options->password_authentication = -1;
+ options->kbd_interactive_authentication = -1;
+ options->kbd_interactive_devices = NULL;
+@@ -2502,8 +2559,18 @@ fill_default_options(Options * options)
+ options->pubkey_authentication = SSH_PUBKEY_AUTH_ALL;
+ if (options->gss_authentication == -1)
+ options->gss_authentication = 0;
++ if (options->gss_keyex == -1)
++ options->gss_keyex = 0;
+ if (options->gss_deleg_creds == -1)
+ options->gss_deleg_creds = 0;
++ if (options->gss_trust_dns == -1)
++ options->gss_trust_dns = 0;
++ if (options->gss_renewal_rekey == -1)
++ options->gss_renewal_rekey = 0;
++#ifdef GSSAPI
++ if (options->gss_kex_algorithms == NULL)
++ options->gss_kex_algorithms = strdup(GSS_KEX_DEFAULT_KEX);
++#endif
+ if (options->password_authentication == -1)
+ options->password_authentication = 1;
+ if (options->kbd_interactive_authentication == -1)
+@@ -3301,7 +3368,14 @@ dump_client_config(Options *o, const char *host)
+ dump_cfg_fmtint(oGatewayPorts, o->fwd_opts.gateway_ports);
+ #ifdef GSSAPI
+ dump_cfg_fmtint(oGssAuthentication, o->gss_authentication);
++ dump_cfg_fmtint(oGssKeyEx, o->gss_keyex);
+ dump_cfg_fmtint(oGssDelegateCreds, o->gss_deleg_creds);
++ dump_cfg_fmtint(oGssTrustDns, o->gss_trust_dns);
++ dump_cfg_fmtint(oGssRenewalRekey, o->gss_renewal_rekey);
++ dump_cfg_string(oGssClientIdentity, o->gss_client_identity);
++ dump_cfg_string(oGssServerIdentity, o->gss_server_identity);
++ dump_cfg_string(oGssKexAlgorithms, o->gss_kex_algorithms ?
++ o->gss_kex_algorithms : GSS_KEX_DEFAULT_KEX);
+ #endif /* GSSAPI */
+ dump_cfg_fmtint(oHashKnownHosts, o->hash_known_hosts);
+ dump_cfg_fmtint(oHostbasedAuthentication, o->hostbased_authentication);
+diff --git a/readconf.h b/readconf.h
+index 2ce1b4c33..d0eb92362 100644
+--- a/readconf.h
++++ b/readconf.h
+@@ -40,7 +40,13 @@ typedef struct {
+ int pubkey_authentication; /* Try ssh2 pubkey authentication. */
+ int hostbased_authentication; /* ssh2's rhosts_rsa */
+ int gss_authentication; /* Try GSS authentication */
++ int gss_keyex; /* Try GSS key exchange */
+ int gss_deleg_creds; /* Delegate GSS credentials */
++ int gss_trust_dns; /* Trust DNS for GSS canonicalization */
++ int gss_renewal_rekey; /* Credential renewal forces rekey */
++ char *gss_client_identity; /* Principal to initiate GSSAPI with */
++ char *gss_server_identity; /* GSSAPI target principal */
++ char *gss_kex_algorithms; /* GSSAPI kex methods to be offered by client. */
+ int password_authentication; /* Try password
+ * authentication. */
+ int kbd_interactive_authentication; /* Try keyboard-interactive auth. */
+diff --git a/servconf.c b/servconf.c
+index 2e039da8b..940de9e15 100644
+--- a/servconf.c
++++ b/servconf.c
+@@ -70,6 +70,7 @@
+ #include "auth.h"
+ #include "myproposal.h"
+ #include "digest.h"
++#include "ssh-gss.h"
+
+ static void add_listen_addr(ServerOptions *, const char *,
+ const char *, int);
+@@ -136,8 +137,11 @@ initialize_server_options(ServerOptions *options)
+ options->kerberos_ticket_cleanup = -1;
+ options->kerberos_get_afs_token = -1;
+ options->gss_authentication=-1;
++ options->gss_keyex = -1;
+ options->gss_cleanup_creds = -1;
+ options->gss_strict_acceptor = -1;
++ options->gss_store_rekey = -1;
++ options->gss_kex_algorithms = NULL;
+ options->password_authentication = -1;
+ options->kbd_interactive_authentication = -1;
+ options->permit_empty_passwd = -1;
+@@ -360,10 +364,18 @@ fill_default_server_options(ServerOptions *options)
+ options->kerberos_get_afs_token = 0;
+ if (options->gss_authentication == -1)
+ options->gss_authentication = 0;
++ if (options->gss_keyex == -1)
++ options->gss_keyex = 0;
+ if (options->gss_cleanup_creds == -1)
+ options->gss_cleanup_creds = 1;
+ if (options->gss_strict_acceptor == -1)
+ options->gss_strict_acceptor = 1;
++ if (options->gss_store_rekey == -1)
++ options->gss_store_rekey = 0;
++#ifdef GSSAPI
++ if (options->gss_kex_algorithms == NULL)
++ options->gss_kex_algorithms = strdup(GSS_KEX_DEFAULT_KEX);
++#endif
+ if (options->password_authentication == -1)
+ options->password_authentication = 1;
+ if (options->kbd_interactive_authentication == -1)
+@@ -520,6 +532,7 @@ typedef enum {
+ sHostKeyAlgorithms, sPerSourceMaxStartups, sPerSourceNetBlockSize,
+ sClientAliveInterval, sClientAliveCountMax, sAuthorizedKeysFile,
+ sGssAuthentication, sGssCleanupCreds, sGssStrictAcceptor,
++ sGssKeyEx, sGssKexAlgorithms, sGssStoreRekey,
+ sAcceptEnv, sSetEnv, sPermitTunnel,
+ sMatch, sPermitOpen, sPermitListen, sForceCommand, sChrootDirectory,
+ sUsePrivilegeSeparation, sAllowAgentForwarding,
+@@ -602,12 +615,22 @@ static struct {
+ #ifdef GSSAPI
+ { "gssapiauthentication", sGssAuthentication, SSHCFG_ALL },
+ { "gssapicleanupcredentials", sGssCleanupCreds, SSHCFG_GLOBAL },
++ { "gssapicleanupcreds", sGssCleanupCreds, SSHCFG_GLOBAL },
+ { "gssapistrictacceptorcheck", sGssStrictAcceptor, SSHCFG_GLOBAL },
++ { "gssapikeyexchange", sGssKeyEx, SSHCFG_GLOBAL },
++ { "gssapistorecredentialsonrekey", sGssStoreRekey, SSHCFG_GLOBAL },
++ { "gssapikexalgorithms", sGssKexAlgorithms, SSHCFG_GLOBAL },
+ #else
+ { "gssapiauthentication", sUnsupported, SSHCFG_ALL },
+ { "gssapicleanupcredentials", sUnsupported, SSHCFG_GLOBAL },
++ { "gssapicleanupcreds", sUnsupported, SSHCFG_GLOBAL },
+ { "gssapistrictacceptorcheck", sUnsupported, SSHCFG_GLOBAL },
++ { "gssapikeyexchange", sUnsupported, SSHCFG_GLOBAL },
++ { "gssapistorecredentialsonrekey", sUnsupported, SSHCFG_GLOBAL },
++ { "gssapikexalgorithms", sUnsupported, SSHCFG_GLOBAL },
+ #endif
++ { "gssusesessionccache", sUnsupported, SSHCFG_GLOBAL },
++ { "gssapiusesessioncredcache", sUnsupported, SSHCFG_GLOBAL },
+ { "passwordauthentication", sPasswordAuthentication, SSHCFG_ALL },
+ { "kbdinteractiveauthentication", sKbdInteractiveAuthentication, SSHCFG_ALL },
+ { "challengeresponseauthentication", sKbdInteractiveAuthentication, SSHCFG_ALL }, /* alias */
+@@ -1644,6 +1667,10 @@ process_server_config_line_depth(ServerOptions *options, char *line,
+ intptr = &options->gss_authentication;
+ goto parse_flag;
+
++ case sGssKeyEx:
++ intptr = &options->gss_keyex;
++ goto parse_flag;
++
+ case sGssCleanupCreds:
+ intptr = &options->gss_cleanup_creds;
+ goto parse_flag;
+@@ -1652,6 +1679,22 @@ process_server_config_line_depth(ServerOptions *options, char *line,
+ intptr = &options->gss_strict_acceptor;
+ goto parse_flag;
+
++ case sGssStoreRekey:
++ intptr = &options->gss_store_rekey;
++ goto parse_flag;
++
++ case sGssKexAlgorithms:
++ arg = argv_next(&ac, &av);
++ if (!arg || *arg == '\0')
++ fatal("%.200s line %d: Missing argument.",
++ filename, linenum);
++ if (!kex_gss_names_valid(arg))
++ fatal("%.200s line %d: Bad GSSAPI KexAlgorithms '%s'.",
++ filename, linenum, arg ? arg : "<NONE>");
++ if (*activep && options->gss_kex_algorithms == NULL)
++ options->gss_kex_algorithms = xstrdup(arg);
++ break;
++
+ case sPasswordAuthentication:
+ intptr = &options->password_authentication;
+ goto parse_flag;
+@@ -3018,6 +3061,10 @@ dump_config(ServerOptions *o)
+ #ifdef GSSAPI
+ dump_cfg_fmtint(sGssAuthentication, o->gss_authentication);
+ dump_cfg_fmtint(sGssCleanupCreds, o->gss_cleanup_creds);
++ dump_cfg_fmtint(sGssKeyEx, o->gss_keyex);
++ dump_cfg_fmtint(sGssStrictAcceptor, o->gss_strict_acceptor);
++ dump_cfg_fmtint(sGssStoreRekey, o->gss_store_rekey);
++ dump_cfg_string(sGssKexAlgorithms, o->gss_kex_algorithms);
+ #endif
+ dump_cfg_fmtint(sPasswordAuthentication, o->password_authentication);
+ dump_cfg_fmtint(sKbdInteractiveAuthentication,
+diff --git a/servconf.h b/servconf.h
+index 7ad43de87..38a68d576 100644
+--- a/servconf.h
++++ b/servconf.h
+@@ -141,8 +141,11 @@ typedef struct {
+ int kerberos_get_afs_token; /* If true, try to get AFS token if
+ * authenticated with Kerberos. */
+ int gss_authentication; /* If true, permit GSSAPI authentication */
++ int gss_keyex; /* If true, permit GSSAPI key exchange */
+ int gss_cleanup_creds; /* If true, destroy cred cache on logout */
+ int gss_strict_acceptor; /* If true, restrict the GSSAPI acceptor name */
++ int gss_store_rekey;
++ char *gss_kex_algorithms; /* GSSAPI kex methods to be offered by client. */
+ int password_authentication; /* If true, permit password
+ * authentication. */
+ int kbd_interactive_authentication; /* If true, permit */
+diff --git a/session.c b/session.c
+index f30d7ac51..96960f2da 100644
+--- a/session.c
++++ b/session.c
+@@ -2680,13 +2680,19 @@ do_cleanup(struct ssh *ssh, Authctxt *authctxt)
+
+ #ifdef KRB5
+ if (options.kerberos_ticket_cleanup &&
+- authctxt->krb5_ctx)
++ authctxt->krb5_ctx) {
++ temporarily_use_uid(authctxt->pw);
+ krb5_cleanup_proc(authctxt);
++ restore_uid();
++ }
+ #endif
+
+ #ifdef GSSAPI
+- if (options.gss_cleanup_creds)
++ if (options.gss_cleanup_creds) {
++ temporarily_use_uid(authctxt->pw);
+ ssh_gssapi_cleanup_creds();
++ restore_uid();
++ }
+ #endif
+
+ /* remove agent socket */
+diff --git a/ssh-gss.h b/ssh-gss.h
+index a8af117d2..6303ce185 100644
+--- a/ssh-gss.h
++++ b/ssh-gss.h
+@@ -1,6 +1,6 @@
+ /* $OpenBSD: ssh-gss.h,v 1.15 2021/01/27 10:05:28 djm Exp $ */
+ /*
+- * Copyright (c) 2001-2003 Simon Wilkinson. All rights reserved.
++ * Copyright (c) 2001-2009 Simon Wilkinson. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+@@ -61,10 +61,34 @@
+
+ #define SSH_GSS_OIDTYPE 0x06
+
++#define SSH2_MSG_KEXGSS_INIT 30
++#define SSH2_MSG_KEXGSS_CONTINUE 31
++#define SSH2_MSG_KEXGSS_COMPLETE 32
++#define SSH2_MSG_KEXGSS_HOSTKEY 33
++#define SSH2_MSG_KEXGSS_ERROR 34
++#define SSH2_MSG_KEXGSS_GROUPREQ 40
++#define SSH2_MSG_KEXGSS_GROUP 41
++#define KEX_GSS_GRP1_SHA1_ID "gss-group1-sha1-"
++#define KEX_GSS_GRP14_SHA1_ID "gss-group14-sha1-"
++#define KEX_GSS_GRP14_SHA256_ID "gss-group14-sha256-"
++#define KEX_GSS_GRP16_SHA512_ID "gss-group16-sha512-"
++#define KEX_GSS_GEX_SHA1_ID "gss-gex-sha1-"
++#define KEX_GSS_NISTP256_SHA256_ID "gss-nistp256-sha256-"
++#define KEX_GSS_C25519_SHA256_ID "gss-curve25519-sha256-"
++
++#define GSS_KEX_DEFAULT_KEX \
++ KEX_GSS_GRP14_SHA256_ID "," \
++ KEX_GSS_GRP16_SHA512_ID "," \
++ KEX_GSS_NISTP256_SHA256_ID "," \
++ KEX_GSS_C25519_SHA256_ID "," \
++ KEX_GSS_GRP14_SHA1_ID "," \
++ KEX_GSS_GEX_SHA1_ID
++
+ typedef struct {
+ char *filename;
+ char *envvar;
+ char *envval;
++ struct passwd *owner;
+ void *data;
+ } ssh_gssapi_ccache;
+
+@@ -72,8 +96,11 @@ typedef struct {
+ gss_buffer_desc displayname;
+ gss_buffer_desc exportedname;
+ gss_cred_id_t creds;
++ gss_name_t name;
+ struct ssh_gssapi_mech_struct *mech;
+ ssh_gssapi_ccache store;
++ int used;
++ int updated;
+ } ssh_gssapi_client;
+
+ typedef struct ssh_gssapi_mech_struct {
+@@ -84,6 +111,7 @@ typedef struct ssh_gssapi_mech_struct {
+ int (*userok) (ssh_gssapi_client *, char *);
+ int (*localname) (ssh_gssapi_client *, char **);
+ void (*storecreds) (ssh_gssapi_client *);
++ int (*updatecreds) (ssh_gssapi_ccache *, ssh_gssapi_client *);
+ } ssh_gssapi_mech;
+
+ typedef struct {
+@@ -94,10 +122,11 @@ typedef struct {
+ gss_OID oid; /* client */
+ gss_cred_id_t creds; /* server */
+ gss_name_t client; /* server */
+- gss_cred_id_t client_creds; /* server */
++ gss_cred_id_t client_creds; /* both */
+ } Gssctxt;
+
+ extern ssh_gssapi_mech *supported_mechs[];
++extern Gssctxt *gss_kex_context;
+
+ int ssh_gssapi_check_oid(Gssctxt *, void *, size_t);
+ void ssh_gssapi_set_oid_data(Gssctxt *, void *, size_t);
+@@ -109,6 +138,7 @@ OM_uint32 ssh_gssapi_test_oid_supported(OM_uint32 *, gss_OID, int *);
+
+ struct sshbuf;
+ int ssh_gssapi_get_buffer_desc(struct sshbuf *, gss_buffer_desc *);
++int ssh_gssapi_sshpkt_get_buffer_desc(struct ssh *, gss_buffer_desc *);
+
+ OM_uint32 ssh_gssapi_import_name(Gssctxt *, const char *);
+ OM_uint32 ssh_gssapi_init_ctx(Gssctxt *, int,
+@@ -123,17 +153,33 @@ void ssh_gssapi_delete_ctx(Gssctxt **);
+ OM_uint32 ssh_gssapi_sign(Gssctxt *, gss_buffer_t, gss_buffer_t);
+ void ssh_gssapi_buildmic(struct sshbuf *, const char *,
+ const char *, const char *, const struct sshbuf *);
+-int ssh_gssapi_check_mechanism(Gssctxt **, gss_OID, const char *);
++int ssh_gssapi_check_mechanism(Gssctxt **, gss_OID, const char *, const char *);
++OM_uint32 ssh_gssapi_client_identity(Gssctxt *, const char *);
++int ssh_gssapi_credentials_updated(Gssctxt *);
+
+ /* In the server */
++typedef int ssh_gssapi_check_fn(Gssctxt **, gss_OID, const char *,
++ const char *);
++char *ssh_gssapi_client_mechanisms(const char *, const char *, const char *);
++char *ssh_gssapi_kex_mechs(gss_OID_set, ssh_gssapi_check_fn *, const char *,
++ const char *, const char *);
++gss_OID ssh_gssapi_id_kex(Gssctxt *, char *, int);
++int ssh_gssapi_server_check_mech(Gssctxt **,gss_OID, const char *,
++ const char *);
+ OM_uint32 ssh_gssapi_server_ctx(Gssctxt **, gss_OID);
+-int ssh_gssapi_userok(char *name);
++int ssh_gssapi_userok(char *name, struct passwd *, int kex);
+ OM_uint32 ssh_gssapi_checkmic(Gssctxt *, gss_buffer_t, gss_buffer_t);
+ void ssh_gssapi_do_child(char ***, u_int *);
+ void ssh_gssapi_cleanup_creds(void);
+ void ssh_gssapi_storecreds(void);
+ const char *ssh_gssapi_displayname(void);
+
++char *ssh_gssapi_server_mechanisms(void);
++int ssh_gssapi_oid_table_ok(void);
++
++int ssh_gssapi_update_creds(ssh_gssapi_ccache *store);
++void ssh_gssapi_rekey_creds(void);
++
+ #endif /* GSSAPI */
+
+ #endif /* _SSH_GSS_H */
+diff --git a/ssh-null.c b/ssh-null.c
+new file mode 100644
+index 000000000..a934bda77
+--- /dev/null
++++ b/ssh-null.c
+@@ -0,0 +1,108 @@
++/*
++ * Copyright (c) 2023 Colin Watson. All rights reserved.
++ *
++ * Redistribution and use in source and binary forms, with or without
++ * modification, are permitted provided that the following conditions
++ * are met:
++ * 1. Redistributions of source code must retain the above copyright
++ * notice, this list of conditions and the following disclaimer.
++ * 2. Redistributions in binary form must reproduce the above copyright
++ * notice, this list of conditions and the following disclaimer in the
++ * documentation and/or other materials provided with the distribution.
++ *
++ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
++ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
++ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
++ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
++ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
++ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
++ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
++ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
++ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
++ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
++ */
++
++#include "includes.h"
++
++#ifdef GSSAPI
++
++#include "sshbuf.h"
++#include "ssherr.h"
++#include "sshkey.h"
++
++static int
++ssh_null_equal(const struct sshkey *a, const struct sshkey *b)
++{
++ return 1;
++}
++
++static int
++ssh_null_serialize_public(const struct sshkey *key, struct sshbuf *b,
++ enum sshkey_serialize_rep opts)
++{
++ return SSH_ERR_KEY_TYPE_UNKNOWN;
++}
++
++static int
++ssh_null_deserialize_public(const char *ktype, struct sshbuf *b,
++ struct sshkey *key)
++{
++ return SSH_ERR_KEY_TYPE_UNKNOWN;
++}
++
++static int
++ssh_null_serialize_private(const struct sshkey *key, struct sshbuf *b,
++ enum sshkey_serialize_rep opts)
++{
++ return SSH_ERR_KEY_TYPE_UNKNOWN;
++}
++
++static int
++ssh_null_deserialize_private(const char *ktype, struct sshbuf *b,
++ struct sshkey *key)
++{
++ return SSH_ERR_KEY_TYPE_UNKNOWN;
++}
++
++static int
++ssh_null_copy_public(const struct sshkey *from, struct sshkey *to)
++{
++ return SSH_ERR_KEY_TYPE_UNKNOWN;
++}
++
++static int
++ssh_null_verify(const struct sshkey *key, const u_char *sig, size_t siglen,
++ const u_char *data, size_t dlen, const char *alg, u_int compat,
++ struct sshkey_sig_details **detailsp)
++{
++ return SSH_ERR_KEY_TYPE_UNKNOWN;
++}
++
++static const struct sshkey_impl_funcs sshkey_null_funcs = {
++ /* .size = */ NULL,
++ /* .alloc = */ NULL,
++ /* .cleanup = */ NULL,
++ /* .equal = */ ssh_null_equal,
++ /* .ssh_serialize_public = */ ssh_null_serialize_public,
++ /* .ssh_deserialize_public = */ ssh_null_deserialize_public,
++ /* .ssh_serialize_private = */ ssh_null_serialize_private,
++ /* .ssh_deserialize_private = */ ssh_null_deserialize_private,
++ /* .generate = */ NULL,
++ /* .copy_public = */ ssh_null_copy_public,
++ /* .sign = */ NULL,
++ /* .verify = */ ssh_null_verify,
++};
++
++const struct sshkey_impl sshkey_null_impl = {
++ /* .name = */ "null",
++ /* .shortname = */ "null",
++ /* .sigalg = */ NULL,
++ /* .type = */ KEY_NULL,
++ /* .nid = */ 0,
++ /* .cert = */ 0,
++ /* .sigonly = */ 0,
++ /* .keybits = */ 0,
++ /* .funcs = */ &sshkey_null_funcs,
++};
++
++#endif /* GSSAPI */
+diff --git a/ssh.1 b/ssh.1
+index a3d1ba163..dfd80b8bc 100644
+--- a/ssh.1
++++ b/ssh.1
+@@ -534,7 +534,13 @@ For full details of the options listed below, and their possible values, see
+ .It GatewayPorts
+ .It GlobalKnownHostsFile
+ .It GSSAPIAuthentication
++.It GSSAPIKeyExchange
++.It GSSAPIClientIdentity
+ .It GSSAPIDelegateCredentials
++.It GSSAPIKexAlgorithms
++.It GSSAPIRenewalForcesRekey
++.It GSSAPIServerIdentity
++.It GSSAPITrustDns
+ .It HashKnownHosts
+ .It Host
+ .It HostbasedAcceptedAlgorithms
+@@ -612,6 +618,8 @@ flag),
+ (supported message integrity codes),
+ .Ar kex
+ (key exchange algorithms),
++.Ar kex-gss
++(GSSAPI key exchange algorithms),
+ .Ar key
+ (key types),
+ .Ar key-cert
+diff --git a/ssh.c b/ssh.c
+index 87454b84a..855777d7f 100644
+--- a/ssh.c
++++ b/ssh.c
+@@ -787,6 +787,8 @@ main(int ac, char **av)
+ else if (strcmp(optarg, "kex") == 0 ||
+ strcasecmp(optarg, "KexAlgorithms") == 0)
+ cp = kex_alg_list('\n');
++ else if (strcmp(optarg, "kex-gss") == 0)
++ cp = kex_gss_alg_list('\n');
+ else if (strcmp(optarg, "key") == 0)
+ cp = sshkey_alg_list(0, 0, 0, '\n');
+ else if (strcmp(optarg, "key-cert") == 0)
+@@ -814,8 +816,8 @@ main(int ac, char **av)
+ } else if (strcmp(optarg, "help") == 0) {
+ cp = xstrdup(
+ "cipher\ncipher-auth\ncompression\nkex\n"
+- "key\nkey-cert\nkey-plain\nkey-sig\nmac\n"
+- "protocol-version\nsig");
++ "kex-gss\nkey\nkey-cert\nkey-plain\n"
++ "key-sig\nmac\nprotocol-version\nsig");
+ }
+ if (cp == NULL)
+ fatal("Unsupported query \"%s\"", optarg);
+diff --git a/ssh_config b/ssh_config
+index 842ea866c..52aae8692 100644
+--- a/ssh_config
++++ b/ssh_config
+@@ -24,6 +24,8 @@
+ # HostbasedAuthentication no
+ # GSSAPIAuthentication no
+ # GSSAPIDelegateCredentials no
++# GSSAPIKeyExchange no
++# GSSAPITrustDNS no
+ # BatchMode no
+ # CheckHostIP yes
+ # AddressFamily any
+diff --git a/ssh_config.5 b/ssh_config.5
+index 9eb6b9779..43f3b642c 100644
+--- a/ssh_config.5
++++ b/ssh_config.5
+@@ -839,10 +839,67 @@ The default is
+ Specifies whether user authentication based on GSSAPI is allowed.
+ The default is
+ .Cm no .
++.It Cm GSSAPIClientIdentity
++If set, specifies the GSSAPI client identity that ssh should use when
++connecting to the server. The default is unset, which means that the default
++identity will be used.
+ .It Cm GSSAPIDelegateCredentials
+ Forward (delegate) credentials to the server.
+ The default is
+ .Cm no .
++.It Cm GSSAPIKeyExchange
++Specifies whether key exchange based on GSSAPI may be used. When using
++GSSAPI key exchange the server need not have a host key.
++The default is
++.Dq no .
++.It Cm GSSAPIRenewalForcesRekey
++If set to
++.Dq yes
++then renewal of the client's GSSAPI credentials will force the rekeying of the
++ssh connection. With a compatible server, this will delegate the renewed
++credentials to a session on the server.
++.Pp
++Checks are made to ensure that credentials are only propagated when the new
++credentials match the old ones on the originating client and where the
++receiving server still has the old set in its cache.
++.Pp
++The default is
++.Dq no .
++.Pp
++For this to work
++.Cm GSSAPIKeyExchange
++needs to be enabled in the server and also used by the client.
++.It Cm GSSAPIServerIdentity
++If set, specifies the GSSAPI server identity that ssh should expect when
++connecting to the server. The default is unset, which means that the
++expected GSSAPI server identity will be determined from the target
++hostname.
++.It Cm GSSAPITrustDns
++Set to
++.Dq yes
++to indicate that the DNS is trusted to securely canonicalize
++the name of the host being connected to. If
++.Dq no ,
++the hostname entered on the
++command line will be passed untouched to the GSSAPI library.
++The default is
++.Dq no .
++.It Cm GSSAPIKexAlgorithms
++The list of key exchange algorithms that are offered for GSSAPI
++key exchange. Possible values are
++.Bd -literal -offset 3n
++gss-gex-sha1-,
++gss-group1-sha1-,
++gss-group14-sha1-,
++gss-group14-sha256-,
++gss-group16-sha512-,
++gss-nistp256-sha256-,
++gss-curve25519-sha256-
++.Ed
++.Pp
++The default is
++.Dq gss-group14-sha256-,gss-group16-sha512-,gss-nistp256-sha256-,gss-curve25519-sha256-,gss-gex-sha1-,gss-group14-sha1- .
++This option only applies to connections using GSSAPI.
+ .It Cm HashKnownHosts
+ Indicates that
+ .Xr ssh 1
+diff --git a/sshconnect2.c b/sshconnect2.c
+index 58fe98db2..cb6a94e76 100644
+--- a/sshconnect2.c
++++ b/sshconnect2.c
+@@ -81,8 +81,6 @@
+ #endif
+
+ /* import */
+-extern char *client_version_string;
+-extern char *server_version_string;
+ extern Options options;
+
+ /*
+@@ -226,6 +224,11 @@ ssh_kex2(struct ssh *ssh, char *host, struct sockaddr *hostaddr, u_short port,
+ char *prop_kex = NULL, *prop_enc = NULL, *prop_hostkey = NULL;
+ int r, use_known_hosts_order = 0;
+
++#if defined(GSSAPI) && defined(WITH_OPENSSL)
++ char *orig = NULL, *gss = NULL;
++ char *gss_host = NULL;
++#endif
++
+ xxx_host = host;
+ xxx_hostaddr = hostaddr;
+ xxx_conn_info = cinfo;
+@@ -269,6 +272,42 @@ ssh_kex2(struct ssh *ssh, char *host, struct sockaddr *hostaddr, u_short port,
+ compat_pkalg_proposal(ssh, options.hostkeyalgorithms);
+ }
+
++#if defined(GSSAPI) && defined(WITH_OPENSSL)
++ if (options.gss_keyex) {
++ /* Add the GSSAPI mechanisms currently supported on this
++ * client to the key exchange algorithm proposal */
++ orig = myproposal[PROPOSAL_KEX_ALGS];
++
++ if (options.gss_server_identity) {
++ gss_host = xstrdup(options.gss_server_identity);
++ } else if (options.gss_trust_dns) {
++ gss_host = remote_hostname(ssh);
++ /* Fall back to specified host if we are using proxy command
++ * and can not use DNS on that socket */
++ if (strcmp(gss_host, "UNKNOWN") == 0) {
++ free(gss_host);
++ gss_host = xstrdup(host);
++ }
++ } else {
++ gss_host = xstrdup(host);
++ }
++
++ gss = ssh_gssapi_client_mechanisms(gss_host,
++ options.gss_client_identity, options.gss_kex_algorithms);
++ if (gss) {
++ debug("Offering GSSAPI proposal: %s", gss);
++ xasprintf(&myproposal[PROPOSAL_KEX_ALGS],
++ "%s,%s", gss, orig);
++
++ /* If we've got GSSAPI algorithms, then we also support the
++ * 'null' hostkey, as a last resort */
++ orig = myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS];
++ xasprintf(&myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS],
++ "%s,null", orig);
++ }
++ }
++#endif
++
+ if (options.rekey_limit || options.rekey_interval)
+ ssh_packet_set_rekey_limits(ssh, options.rekey_limit,
+ options.rekey_interval);
+@@ -287,16 +326,46 @@ ssh_kex2(struct ssh *ssh, char *host, struct sockaddr *hostaddr, u_short port,
+ # ifdef OPENSSL_HAS_ECC
+ ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_client;
+ # endif
+-#endif
++# ifdef GSSAPI
++ if (options.gss_keyex) {
++ ssh->kex->kex[KEX_GSS_GRP1_SHA1] = kexgss_client;
++ ssh->kex->kex[KEX_GSS_GRP14_SHA1] = kexgss_client;
++ ssh->kex->kex[KEX_GSS_GRP14_SHA256] = kexgss_client;
++ ssh->kex->kex[KEX_GSS_GRP16_SHA512] = kexgss_client;
++ ssh->kex->kex[KEX_GSS_GEX_SHA1] = kexgssgex_client;
++ ssh->kex->kex[KEX_GSS_NISTP256_SHA256] = kexgss_client;
++ ssh->kex->kex[KEX_GSS_C25519_SHA256] = kexgss_client;
++ }
++# endif
++#endif /* WITH_OPENSSL */
+ ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_client;
+ ssh->kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_client;
+ ssh->kex->verify_host_key=&verify_host_key_callback;
+
++#if defined(GSSAPI) && defined(WITH_OPENSSL)
++ if (options.gss_keyex) {
++ ssh->kex->gss_deleg_creds = options.gss_deleg_creds;
++ ssh->kex->gss_trust_dns = options.gss_trust_dns;
++ ssh->kex->gss_client = options.gss_client_identity;
++ ssh->kex->gss_host = gss_host;
++ }
++#endif
++
+ ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &ssh->kex->done);
+
+ /* remove ext-info from the KEX proposals for rekeying */
+ myproposal[PROPOSAL_KEX_ALGS] =
+ compat_kex_proposal(ssh, options.kex_algorithms);
++#if defined(GSSAPI) && defined(WITH_OPENSSL)
++ /* repair myproposal after it was crumpled by the */
++ /* ext-info removal above */
++ if (gss) {
++ orig = myproposal[PROPOSAL_KEX_ALGS];
++ xasprintf(&myproposal[PROPOSAL_KEX_ALGS],
++ "%s,%s", gss, orig);
++ free(gss);
++ }
++#endif
+ if ((r = kex_prop2buf(ssh->kex->my, myproposal)) != 0)
+ fatal_r(r, "kex_prop2buf");
+
+@@ -394,6 +463,7 @@ static int input_gssapi_response(int type, u_int32_t, struct ssh *);
+ static int input_gssapi_token(int type, u_int32_t, struct ssh *);
+ static int input_gssapi_error(int, u_int32_t, struct ssh *);
+ static int input_gssapi_errtok(int, u_int32_t, struct ssh *);
++static int userauth_gsskeyex(struct ssh *);
+ #endif
+
+ void userauth(struct ssh *, char *);
+@@ -410,6 +480,11 @@ static char *authmethods_get(void);
+
+ Authmethod authmethods[] = {
+ #ifdef GSSAPI
++ {"gssapi-keyex",
++ userauth_gsskeyex,
++ NULL,
++ &options.gss_keyex,
++ NULL},
+ {"gssapi-with-mic",
+ userauth_gssapi,
+ userauth_gssapi_cleanup,
+@@ -785,12 +860,32 @@ userauth_gssapi(struct ssh *ssh)
+ OM_uint32 min;
+ int r, ok = 0;
+ gss_OID mech = NULL;
++ char *gss_host = NULL;
++
++ if (options.gss_server_identity) {
++ gss_host = xstrdup(options.gss_server_identity);
++ } else if (options.gss_trust_dns) {
++ gss_host = remote_hostname(ssh);
++ /* Fall back to specified host if we are using proxy command
++ * and can not use DNS on that socket */
++ if (strcmp(gss_host, "UNKNOWN") == 0) {
++ free(gss_host);
++ gss_host = xstrdup(authctxt->host);
++ }
++ } else {
++ gss_host = xstrdup(authctxt->host);
++ }
+
+ /* Try one GSSAPI method at a time, rather than sending them all at
+ * once. */
+
+ if (authctxt->gss_supported_mechs == NULL)
+- gss_indicate_mechs(&min, &authctxt->gss_supported_mechs);
++ if (GSS_ERROR(gss_indicate_mechs(&min,
++ &authctxt->gss_supported_mechs))) {
++ authctxt->gss_supported_mechs = NULL;
++ free(gss_host);
++ return 0;
++ }
+
+ /* Check to see whether the mechanism is usable before we offer it */
+ while (authctxt->mech_tried < authctxt->gss_supported_mechs->count &&
+@@ -799,13 +894,15 @@ userauth_gssapi(struct ssh *ssh)
+ elements[authctxt->mech_tried];
+ /* My DER encoding requires length<128 */
+ if (mech->length < 128 && ssh_gssapi_check_mechanism(&gssctxt,
+- mech, authctxt->host)) {
++ mech, gss_host, options.gss_client_identity)) {
+ ok = 1; /* Mechanism works */
+ } else {
+ authctxt->mech_tried++;
+ }
+ }
+
++ free(gss_host);
++
+ if (!ok || mech == NULL)
+ return 0;
+
+@@ -1046,6 +1143,55 @@ input_gssapi_error(int type, u_int32_t plen, struct ssh *ssh)
+ free(lang);
+ return r;
+ }
++
++int
++userauth_gsskeyex(struct ssh *ssh)
++{
++ struct sshbuf *b = NULL;
++ Authctxt *authctxt = ssh->authctxt;
++ gss_buffer_desc gssbuf;
++ gss_buffer_desc mic = GSS_C_EMPTY_BUFFER;
++ OM_uint32 ms;
++ int r;
++
++ static int attempt = 0;
++ if (attempt++ >= 1)
++ return (0);
++
++ if (gss_kex_context == NULL) {
++ debug("No valid Key exchange context");
++ return (0);
++ }
++
++ if ((b = sshbuf_new()) == NULL)
++ fatal_f("sshbuf_new failed");
++
++ ssh_gssapi_buildmic(b, authctxt->server_user, authctxt->service,
++ "gssapi-keyex", ssh->kex->session_id);
++
++ if ((gssbuf.value = sshbuf_mutable_ptr(b)) == NULL)
++ fatal_f("sshbuf_mutable_ptr failed");
++ gssbuf.length = sshbuf_len(b);
++
++ if (GSS_ERROR(ssh_gssapi_sign(gss_kex_context, &gssbuf, &mic))) {
++ sshbuf_free(b);
++ return (0);
++ }
++
++ if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
++ (r = sshpkt_put_cstring(ssh, authctxt->server_user)) != 0 ||
++ (r = sshpkt_put_cstring(ssh, authctxt->service)) != 0 ||
++ (r = sshpkt_put_cstring(ssh, authctxt->method->name)) != 0 ||
++ (r = sshpkt_put_string(ssh, mic.value, mic.length)) != 0 ||
++ (r = sshpkt_send(ssh)) != 0)
++ fatal_fr(r, "parsing");
++
++ sshbuf_free(b);
++ gss_release_buffer(&ms, &mic);
++
++ return (1);
++}
++
+ #endif /* GSSAPI */
+
+ static int
+diff --git a/sshd.c b/sshd.c
+index 6321936c0..6ad9a845a 100644
+--- a/sshd.c
++++ b/sshd.c
+@@ -803,8 +803,8 @@ notify_hostkeys(struct ssh *ssh)
+ }
+ debug3_f("sent %u hostkeys", nkeys);
+ if (nkeys == 0)
+- fatal_f("no hostkeys");
+- if ((r = sshpkt_send(ssh)) != 0)
++ debug3_f("no hostkeys");
++ else if ((r = sshpkt_send(ssh)) != 0)
+ sshpkt_fatal(ssh, r, "%s: send", __func__);
+ sshbuf_free(buf);
+ }
+@@ -1914,7 +1914,8 @@ main(int ac, char **av)
+ free(fp);
+ }
+ accumulate_host_timing_secret(cfg, NULL);
+- if (!sensitive_data.have_ssh2_key) {
++ /* The GSSAPI key exchange can run without a host key */
++ if (!sensitive_data.have_ssh2_key && !options.gss_keyex) {
+ logit("sshd: no hostkeys available -- exiting.");
+ exit(1);
+ }
+@@ -2398,6 +2399,48 @@ do_ssh2_kex(struct ssh *ssh)
+ myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = prop_hostkey =
+ compat_pkalg_proposal(ssh, list_hostkey_types());
+
++#if defined(GSSAPI) && defined(WITH_OPENSSL)
++ {
++ char *orig;
++ char *gss = NULL;
++ char *newstr = NULL;
++ orig = myproposal[PROPOSAL_KEX_ALGS];
++
++ /*
++ * If we don't have a host key, then there's no point advertising
++ * the other key exchange algorithms
++ */
++
++ if (strlen(myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS]) == 0)
++ orig = NULL;
++
++ if (options.gss_keyex)
++ gss = ssh_gssapi_server_mechanisms();
++ else
++ gss = NULL;
++
++ if (gss && orig)
++ xasprintf(&newstr, "%s,%s", gss, orig);
++ else if (gss)
++ newstr = gss;
++ else if (orig)
++ newstr = orig;
++
++ /*
++ * If we've got GSSAPI mechanisms, then we've got the 'null' host
++ * key alg, but we can't tell people about it unless its the only
++ * host key algorithm we support
++ */
++ if (gss && (strlen(myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS])) == 0)
++ myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = "null";
++
++ if (newstr)
++ myproposal[PROPOSAL_KEX_ALGS] = newstr;
++ else
++ fatal("No supported key exchange algorithms");
++ }
++#endif
++
+ /* start key exchange */
+ if ((r = kex_setup(ssh, myproposal)) != 0)
+ fatal_r(r, "kex_setup");
+@@ -2413,7 +2456,18 @@ do_ssh2_kex(struct ssh *ssh)
+ # ifdef OPENSSL_HAS_ECC
+ kex->kex[KEX_ECDH_SHA2] = kex_gen_server;
+ # endif
+-#endif
++# ifdef GSSAPI
++ if (options.gss_keyex) {
++ kex->kex[KEX_GSS_GRP1_SHA1] = kexgss_server;
++ kex->kex[KEX_GSS_GRP14_SHA1] = kexgss_server;
++ kex->kex[KEX_GSS_GRP14_SHA256] = kexgss_server;
++ kex->kex[KEX_GSS_GRP16_SHA512] = kexgss_server;
++ kex->kex[KEX_GSS_GEX_SHA1] = kexgssgex_server;
++ kex->kex[KEX_GSS_NISTP256_SHA256] = kexgss_server;
++ kex->kex[KEX_GSS_C25519_SHA256] = kexgss_server;
++ }
++# endif
++#endif /* WITH_OPENSSL */
+ kex->kex[KEX_C25519_SHA256] = kex_gen_server;
+ kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_server;
+ kex->load_host_public_key=&get_hostkey_public_by_type;
+diff --git a/sshd_config b/sshd_config
+index 36894ace5..ecfe8d026 100644
+--- a/sshd_config
++++ b/sshd_config
+@@ -69,6 +69,8 @@ AuthorizedKeysFile .ssh/authorized_keys
+ # GSSAPI options
+ #GSSAPIAuthentication no
+ #GSSAPICleanupCredentials yes
++#GSSAPIStrictAcceptorCheck yes
++#GSSAPIKeyExchange no
+
+ # Set this to 'yes' to enable PAM authentication, account processing,
+ # and session processing. If this is enabled, PAM authentication will
+diff --git a/sshd_config.5 b/sshd_config.5
+index 7313a7f79..83f840511 100644
+--- a/sshd_config.5
++++ b/sshd_config.5
+@@ -719,6 +719,11 @@ Specifies whether to automatically destroy the user's credentials cache
+ on logout.
+ The default is
+ .Cm yes .
++.It Cm GSSAPIKeyExchange
++Specifies whether key exchange based on GSSAPI is allowed. GSSAPI key exchange
++doesn't rely on ssh keys to verify host identity.
++The default is
++.Cm no .
+ .It Cm GSSAPIStrictAcceptorCheck
+ Determines whether to be strict about the identity of the GSSAPI acceptor
+ a client authenticates against.
+@@ -733,6 +738,31 @@ machine's default store.
+ This facility is provided to assist with operation on multi homed machines.
+ The default is
+ .Cm yes .
++.It Cm GSSAPIStoreCredentialsOnRekey
++Controls whether the user's GSSAPI credentials should be updated following a
++successful connection rekeying. This option can be used to accepted renewed
++or updated credentials from a compatible client. The default is
++.Dq no .
++.Pp
++For this to work
++.Cm GSSAPIKeyExchange
++needs to be enabled in the server and also used by the client.
++.It Cm GSSAPIKexAlgorithms
++The list of key exchange algorithms that are accepted by GSSAPI
++key exchange. Possible values are
++.Bd -literal -offset 3n
++gss-gex-sha1-,
++gss-group1-sha1-,
++gss-group14-sha1-,
++gss-group14-sha256-,
++gss-group16-sha512-,
++gss-nistp256-sha256-,
++gss-curve25519-sha256-
++.Ed
++.Pp
++The default is
++.Dq gss-group14-sha256-,gss-group16-sha512-,gss-nistp256-sha256-,gss-curve25519-sha256-,gss-gex-sha1-,gss-group14-sha1- .
++This option only applies to connections using GSSAPI.
+ .It Cm HostbasedAcceptedAlgorithms
+ Specifies the signature algorithms that will be accepted for hostbased
+ authentication as a list of comma-separated patterns.
+diff --git a/sshkey.c b/sshkey.c
+index 43712253d..35a423e92 100644
+--- a/sshkey.c
++++ b/sshkey.c
+@@ -127,6 +127,9 @@ extern const struct sshkey_impl sshkey_dsa_cert_impl;
+ extern const struct sshkey_impl sshkey_xmss_impl;
+ extern const struct sshkey_impl sshkey_xmss_cert_impl;
+ #endif
++#ifdef GSSAPI
++extern const struct sshkey_impl sshkey_null_impl;
++#endif /* GSSAPI */
+
+ const struct sshkey_impl * const keyimpls[] = {
+ &sshkey_ed25519_impl,
+@@ -164,6 +167,9 @@ const struct sshkey_impl * const keyimpls[] = {
+ &sshkey_xmss_impl,
+ &sshkey_xmss_cert_impl,
+ #endif
++#ifdef GSSAPI
++ &sshkey_null_impl,
++#endif /* GSSAPI */
+ NULL
+ };
+
+@@ -319,7 +325,7 @@ sshkey_alg_list(int certs_only, int plain_only, int include_sigonly, char sep)
+
+ for (i = 0; keyimpls[i] != NULL; i++) {
+ impl = keyimpls[i];
+- if (impl->name == NULL)
++ if (impl->name == NULL || impl->type == KEY_NULL)
+ continue;
+ if (!include_sigonly && impl->sigonly)
+ continue;
+diff --git a/sshkey.h b/sshkey.h
+index 771c4bcee..a0742e8c2 100644
+--- a/sshkey.h
++++ b/sshkey.h
+@@ -71,6 +71,7 @@ enum sshkey_types {
+ KEY_ECDSA_SK_CERT,
+ KEY_ED25519_SK,
+ KEY_ED25519_SK_CERT,
++ KEY_NULL,
+ KEY_UNSPEC
+ };
+