Adding upstream version 1:9.6p1.upstream/1%9.6p1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 857 insertions, 0 deletions

diff --git a/auth2.c b/auth2.c
new file mode 100644
index 0000000..271789a
--- /dev/null
+++ b/auth2.c
@@ -0,0 +1,857 @@
+/* $OpenBSD: auth2.c,v 1.168 2023/12/18 14:45:49 djm Exp $ */
+/*
+ * Copyright (c) 2000 Markus Friedl.  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"
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/uio.h>
+
+#include <fcntl.h>
+#include <limits.h>
+#include <pwd.h>
+#include <stdarg.h>
+#include <string.h>
+#include <unistd.h>
+#include <time.h>
+
+#include "stdlib.h"
+#include "atomicio.h"
+#include "xmalloc.h"
+#include "ssh2.h"
+#include "packet.h"
+#include "log.h"
+#include "sshbuf.h"
+#include "misc.h"
+#include "servconf.h"
+#include "sshkey.h"
+#include "hostfile.h"
+#include "auth.h"
+#include "dispatch.h"
+#include "pathnames.h"
+#include "ssherr.h"
+#ifdef GSSAPI
+#include "ssh-gss.h"
+#endif
+#include "monitor_wrap.h"
+#include "digest.h"
+#include "kex.h"
+
+/* import */
+extern ServerOptions options;
+extern struct sshbuf *loginmsg;
+
+/* methods */
+
+extern Authmethod method_none;
+extern Authmethod method_pubkey;
+extern Authmethod method_passwd;
+extern Authmethod method_kbdint;
+extern Authmethod method_hostbased;
+#ifdef GSSAPI
+extern Authmethod method_gssapi;
+#endif
+
+Authmethod *authmethods[] = {
+	&method_none,
+	&method_pubkey,
+#ifdef GSSAPI
+	&method_gssapi,
+#endif
+	&method_passwd,
+	&method_kbdint,
+	&method_hostbased,
+	NULL
+};
+
+/* protocol */
+
+static int input_service_request(int, u_int32_t, struct ssh *);
+static int input_userauth_request(int, u_int32_t, struct ssh *);
+
+/* helper */
+static Authmethod *authmethod_byname(const char *);
+static Authmethod *authmethod_lookup(Authctxt *, const char *);
+static char *authmethods_get(Authctxt *authctxt);
+
+#define MATCH_NONE	0	/* method or submethod mismatch */
+#define MATCH_METHOD	1	/* method matches (no submethod specified) */
+#define MATCH_BOTH	2	/* method and submethod match */
+#define MATCH_PARTIAL	3	/* method matches, submethod can't be checked */
+static int list_starts_with(const char *, const char *, const char *);
+
+char *
+auth2_read_banner(void)
+{
+	struct stat st;
+	char *banner = NULL;
+	size_t len, n;
+	int fd;
+
+	if ((fd = open(options.banner, O_RDONLY)) == -1)
+		return (NULL);
+	if (fstat(fd, &st) == -1) {
+		close(fd);
+		return (NULL);
+	}
+	if (st.st_size <= 0 || st.st_size > 1*1024*1024) {
+		close(fd);
+		return (NULL);
+	}
+
+	len = (size_t)st.st_size;		/* truncate */
+	banner = xmalloc(len + 1);
+	n = atomicio(read, fd, banner, len);
+	close(fd);
+
+	if (n != len) {
+		free(banner);
+		return (NULL);
+	}
+	banner[n] = '\0';
+
+	return (banner);
+}
+
+static void
+userauth_send_banner(struct ssh *ssh, const char *msg)
+{
+	int r;
+
+	if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_BANNER)) != 0 ||
+	    (r = sshpkt_put_cstring(ssh, msg)) != 0 ||
+	    (r = sshpkt_put_cstring(ssh, "")) != 0 ||	/* language, unused */
+	    (r = sshpkt_send(ssh)) != 0)
+		fatal_fr(r, "send packet");
+	debug("%s: sent", __func__);
+}
+
+static void
+userauth_banner(struct ssh *ssh)
+{
+	char *banner = NULL;
+
+	if (options.banner == NULL)
+		return;
+
+	if ((banner = PRIVSEP(auth2_read_banner())) == NULL)
+		goto done;
+	userauth_send_banner(ssh, banner);
+
+done:
+	free(banner);
+}
+
+/*
+ * loop until authctxt->success == TRUE
+ */
+void
+do_authentication2(struct ssh *ssh)
+{
+	Authctxt *authctxt = ssh->authctxt;
+
+	ssh_dispatch_init(ssh, &dispatch_protocol_error);
+	if (ssh->kex->ext_info_c)
+		ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &kex_input_ext_info);
+	ssh_dispatch_set(ssh, SSH2_MSG_SERVICE_REQUEST, &input_service_request);
+	ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &authctxt->success);
+	ssh->authctxt = NULL;
+}
+
+static int
+input_service_request(int type, u_int32_t seq, struct ssh *ssh)
+{
+	Authctxt *authctxt = ssh->authctxt;
+	char *service = NULL;
+	int r, acceptit = 0;
+
+	if ((r = sshpkt_get_cstring(ssh, &service, NULL)) != 0 ||
+	    (r = sshpkt_get_end(ssh)) != 0)
+		goto out;
+
+	if (authctxt == NULL)
+		fatal("input_service_request: no authctxt");
+
+	if (strcmp(service, "ssh-userauth") == 0) {
+		if (!authctxt->success) {
+			acceptit = 1;
+			/* now we can handle user-auth requests */
+			ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST,
+			    &input_userauth_request);
+		}
+	}
+	/* XXX all other service requests are denied */
+
+	if (acceptit) {
+		if ((r = sshpkt_start(ssh, SSH2_MSG_SERVICE_ACCEPT)) != 0 ||
+		    (r = sshpkt_put_cstring(ssh, service)) != 0 ||
+		    (r = sshpkt_send(ssh)) != 0 ||
+		    (r = ssh_packet_write_wait(ssh)) != 0)
+			goto out;
+	} else {
+		debug("bad service request %s", service);
+		ssh_packet_disconnect(ssh, "bad service request %s", service);
+	}
+	ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &dispatch_protocol_error);
+	r = 0;
+ out:
+	free(service);
+	return r;
+}
+
+#define MIN_FAIL_DELAY_SECONDS 0.005
+#define MAX_FAIL_DELAY_SECONDS 5.0
+static double
+user_specific_delay(const char *user)
+{
+	char b[512];
+	size_t len = ssh_digest_bytes(SSH_DIGEST_SHA512);
+	u_char *hash = xmalloc(len);
+	double delay;
+
+	(void)snprintf(b, sizeof b, "%llu%s",
+	    (unsigned long long)options.timing_secret, user);
+	if (ssh_digest_memory(SSH_DIGEST_SHA512, b, strlen(b), hash, len) != 0)
+		fatal_f("ssh_digest_memory");
+	/* 0-4.2 ms of delay */
+	delay = (double)PEEK_U32(hash) / 1000 / 1000 / 1000 / 1000;
+	freezero(hash, len);
+	debug3_f("user specific delay %0.3lfms", delay/1000);
+	return MIN_FAIL_DELAY_SECONDS + delay;
+}
+
+static void
+ensure_minimum_time_since(double start, double seconds)
+{
+	struct timespec ts;
+	double elapsed = monotime_double() - start, req = seconds, remain;
+
+	if (elapsed > MAX_FAIL_DELAY_SECONDS) {
+		debug3_f("elapsed %0.3lfms exceeded the max delay "
+		    "requested %0.3lfms)", elapsed*1000, req*1000);
+		return;
+	}
+
+	/* if we've already passed the requested time, scale up */
+	while ((remain = seconds - elapsed) < 0.0)
+		seconds *= 2;
+
+	ts.tv_sec = remain;
+	ts.tv_nsec = (remain - ts.tv_sec) * 1000000000;
+	debug3_f("elapsed %0.3lfms, delaying %0.3lfms (requested %0.3lfms)",
+	    elapsed*1000, remain*1000, req*1000);
+	nanosleep(&ts, NULL);
+}
+
+static int
+input_userauth_request(int type, u_int32_t seq, struct ssh *ssh)
+{
+	Authctxt *authctxt = ssh->authctxt;
+	Authmethod *m = NULL;
+	char *user = NULL, *service = NULL, *method = NULL, *style = NULL;
+	int r, authenticated = 0;
+	double tstart = monotime_double();
+
+	if (authctxt == NULL)
+		fatal("input_userauth_request: no authctxt");
+
+	if ((r = sshpkt_get_cstring(ssh, &user, NULL)) != 0 ||
+	    (r = sshpkt_get_cstring(ssh, &service, NULL)) != 0 ||
+	    (r = sshpkt_get_cstring(ssh, &method, NULL)) != 0)
+		goto out;
+	debug("userauth-request for user %s service %s method %s", user, service, method);
+	debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
+
+	if ((style = strchr(user, ':')) != NULL)
+		*style++ = 0;
+
+	if (authctxt->attempt >= 1024)
+		auth_maxtries_exceeded(ssh);
+	if (authctxt->attempt++ == 0) {
+		/* setup auth context */
+		authctxt->pw = PRIVSEP(getpwnamallow(ssh, user));
+		authctxt->user = xstrdup(user);
+		if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
+			authctxt->valid = 1;
+			debug2_f("setting up authctxt for %s", user);
+		} else {
+			authctxt->valid = 0;
+			/* Invalid user, fake password information */
+			authctxt->pw = fakepw();
+#ifdef SSH_AUDIT_EVENTS
+			PRIVSEP(audit_event(ssh, SSH_INVALID_USER));
+#endif
+		}
+#ifdef USE_PAM
+		if (options.use_pam)
+			PRIVSEP(start_pam(ssh));
+#endif
+		ssh_packet_set_log_preamble(ssh, "%suser %s",
+		    authctxt->valid ? "authenticating " : "invalid ", user);
+		setproctitle("%s%s", authctxt->valid ? user : "unknown",
+		    use_privsep ? " [net]" : "");
+		authctxt->service = xstrdup(service);
+		authctxt->style = style ? xstrdup(style) : NULL;
+		if (use_privsep)
+			mm_inform_authserv(service, style);
+		userauth_banner(ssh);
+		if ((r = kex_server_update_ext_info(ssh)) != 0)
+			fatal_fr(r, "kex_server_update_ext_info failed");
+		if (auth2_setup_methods_lists(authctxt) != 0)
+			ssh_packet_disconnect(ssh,
+			    "no authentication methods enabled");
+	} else if (strcmp(user, authctxt->user) != 0 ||
+	    strcmp(service, authctxt->service) != 0) {
+		ssh_packet_disconnect(ssh, "Change of username or service "
+		    "not allowed: (%s,%s) -> (%s,%s)",
+		    authctxt->user, authctxt->service, user, service);
+	}
+	/* reset state */
+	auth2_challenge_stop(ssh);
+
+#ifdef GSSAPI
+	/* XXX move to auth2_gssapi_stop() */
+	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
+	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
+#endif
+
+	auth2_authctxt_reset_info(authctxt);
+	authctxt->postponed = 0;
+	authctxt->server_caused_failure = 0;
+
+	/* try to authenticate user */
+	m = authmethod_lookup(authctxt, method);
+	if (m != NULL && authctxt->failures < options.max_authtries) {
+		debug2("input_userauth_request: try method %s", method);
+		authenticated =	m->userauth(ssh, method);
+	}
+	if (!authctxt->authenticated && strcmp(method, "none") != 0)
+		ensure_minimum_time_since(tstart,
+		    user_specific_delay(authctxt->user));
+	userauth_finish(ssh, authenticated, method, NULL);
+	r = 0;
+ out:
+	free(service);
+	free(user);
+	free(method);
+	return r;
+}
+
+void
+userauth_finish(struct ssh *ssh, int authenticated, const char *packet_method,
+    const char *submethod)
+{
+	Authctxt *authctxt = ssh->authctxt;
+	Authmethod *m = NULL;
+	const char *method = packet_method;
+	char *methods;
+	int r, partial = 0;
+
+	if (authenticated) {
+		if (!authctxt->valid) {
+			fatal("INTERNAL ERROR: authenticated invalid user %s",
+			    authctxt->user);
+		}
+		if (authctxt->postponed)
+			fatal("INTERNAL ERROR: authenticated and postponed");
+		/* prefer primary authmethod name to possible synonym */
+		if ((m = authmethod_byname(method)) == NULL)
+			fatal("INTERNAL ERROR: bad method %s", method);
+		method = m->name;
+	}
+
+	/* Special handling for root */
+	if (authenticated && authctxt->pw->pw_uid == 0 &&
+	    !auth_root_allowed(ssh, method)) {
+		authenticated = 0;
+#ifdef SSH_AUDIT_EVENTS
+		PRIVSEP(audit_event(ssh, SSH_LOGIN_ROOT_DENIED));
+#endif
+	}
+
+	if (authenticated && options.num_auth_methods != 0) {
+		if (!auth2_update_methods_lists(authctxt, method, submethod)) {
+			authenticated = 0;
+			partial = 1;
+		}
+	}
+
+	/* Log before sending the reply */
+	auth_log(ssh, authenticated, partial, method, submethod);
+
+	/* Update information exposed to session */
+	if (authenticated || partial)
+		auth2_update_session_info(authctxt, method, submethod);
+
+	if (authctxt->postponed)
+		return;
+
+#ifdef USE_PAM
+	if (options.use_pam && authenticated) {
+		int r, success = PRIVSEP(do_pam_account());
+
+		/* If PAM returned a message, send it to the user. */
+		if (sshbuf_len(loginmsg) > 0) {
+			if ((r = sshbuf_put(loginmsg, "\0", 1)) != 0)
+				fatal("%s: buffer error: %s",
+				    __func__, ssh_err(r));
+			userauth_send_banner(ssh, sshbuf_ptr(loginmsg));
+			if ((r = ssh_packet_write_wait(ssh)) != 0) {
+				sshpkt_fatal(ssh, r,
+				    "%s: send PAM banner", __func__);
+			}
+		}
+		if (!success) {
+			fatal("Access denied for user %s by PAM account "
+			    "configuration", authctxt->user);
+		}
+	}
+#endif
+
+	if (authenticated == 1) {
+		/* turn off userauth */
+		ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST,
+		    &dispatch_protocol_ignore);
+		if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_SUCCESS)) != 0 ||
+		    (r = sshpkt_send(ssh)) != 0 ||
+		    (r = ssh_packet_write_wait(ssh)) != 0)
+			fatal_fr(r, "send success packet");
+		/* now we can break out */
+		authctxt->success = 1;
+		ssh_packet_set_log_preamble(ssh, "user %s", authctxt->user);
+	} else {
+		/* Allow initial try of "none" auth without failure penalty */
+		if (!partial && !authctxt->server_caused_failure &&
+		    (authctxt->attempt > 1 || strcmp(method, "none") != 0))
+			authctxt->failures++;
+		if (authctxt->failures >= options.max_authtries) {
+#ifdef SSH_AUDIT_EVENTS
+			PRIVSEP(audit_event(ssh, SSH_LOGIN_EXCEED_MAXTRIES));
+#endif
+			auth_maxtries_exceeded(ssh);
+		}
+		methods = authmethods_get(authctxt);
+		debug3_f("failure partial=%d next methods=\"%s\"",
+		    partial, methods);
+		if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_FAILURE)) != 0 ||
+		    (r = sshpkt_put_cstring(ssh, methods)) != 0 ||
+		    (r = sshpkt_put_u8(ssh, partial)) != 0 ||
+		    (r = sshpkt_send(ssh)) != 0 ||
+		    (r = ssh_packet_write_wait(ssh)) != 0)
+			fatal_fr(r, "send failure packet");
+		free(methods);
+	}
+}
+
+/*
+ * Checks whether method is allowed by at least one AuthenticationMethods
+ * methods list. Returns 1 if allowed, or no methods lists configured.
+ * 0 otherwise.
+ */
+int
+auth2_method_allowed(Authctxt *authctxt, const char *method,
+    const char *submethod)
+{
+	u_int i;
+
+	/*
+	 * NB. authctxt->num_auth_methods might be zero as a result of
+	 * auth2_setup_methods_lists(), so check the configuration.
+	 */
+	if (options.num_auth_methods == 0)
+		return 1;
+	for (i = 0; i < authctxt->num_auth_methods; i++) {
+		if (list_starts_with(authctxt->auth_methods[i], method,
+		    submethod) != MATCH_NONE)
+			return 1;
+	}
+	return 0;
+}
+
+static char *
+authmethods_get(Authctxt *authctxt)
+{
+	struct sshbuf *b;
+	char *list;
+	int i, r;
+
+	if ((b = sshbuf_new()) == NULL)
+		fatal_f("sshbuf_new failed");
+	for (i = 0; authmethods[i] != NULL; i++) {
+		if (strcmp(authmethods[i]->name, "none") == 0)
+			continue;
+		if (authmethods[i]->enabled == NULL ||
+		    *(authmethods[i]->enabled) == 0)
+			continue;
+		if (!auth2_method_allowed(authctxt, authmethods[i]->name,
+		    NULL))
+			continue;
+		if ((r = sshbuf_putf(b, "%s%s", sshbuf_len(b) ? "," : "",
+		    authmethods[i]->name)) != 0)
+			fatal_fr(r, "buffer error");
+	}
+	if ((list = sshbuf_dup_string(b)) == NULL)
+		fatal_f("sshbuf_dup_string failed");
+	sshbuf_free(b);
+	return list;
+}
+
+static Authmethod *
+authmethod_byname(const char *name)
+{
+	int i;
+
+	if (name == NULL)
+		fatal_f("NULL authentication method name");
+	for (i = 0; authmethods[i] != NULL; i++) {
+		if (strcmp(name, authmethods[i]->name) == 0 ||
+		    (authmethods[i]->synonym != NULL &&
+		    strcmp(name, authmethods[i]->synonym) == 0))
+			return authmethods[i];
+	}
+	debug_f("unrecognized authentication method name: %s", name);
+	return NULL;
+}
+
+static Authmethod *
+authmethod_lookup(Authctxt *authctxt, const char *name)
+{
+	Authmethod *method;
+
+	if ((method = authmethod_byname(name)) == NULL)
+		return NULL;
+
+	if (method->enabled == NULL || *(method->enabled) == 0) {
+		debug3_f("method %s not enabled", name);
+		return NULL;
+	}
+	if (!auth2_method_allowed(authctxt, method->name, NULL)) {
+		debug3_f("method %s not allowed "
+		    "by AuthenticationMethods", name);
+		return NULL;
+	}
+	return method;
+}
+
+/*
+ * Check a comma-separated list of methods for validity. Is need_enable is
+ * non-zero, then also require that the methods are enabled.
+ * Returns 0 on success or -1 if the methods list is invalid.
+ */
+int
+auth2_methods_valid(const char *_methods, int need_enable)
+{
+	char *methods, *omethods, *method, *p;
+	u_int i, found;
+	int ret = -1;
+
+	if (*_methods == '\0') {
+		error("empty authentication method list");
+		return -1;
+	}
+	omethods = methods = xstrdup(_methods);
+	while ((method = strsep(&methods, ",")) != NULL) {
+		for (found = i = 0; !found && authmethods[i] != NULL; i++) {
+			if ((p = strchr(method, ':')) != NULL)
+				*p = '\0';
+			if (strcmp(method, authmethods[i]->name) != 0)
+				continue;
+			if (need_enable) {
+				if (authmethods[i]->enabled == NULL ||
+				    *(authmethods[i]->enabled) == 0) {
+					error("Disabled method \"%s\" in "
+					    "AuthenticationMethods list \"%s\"",
+					    method, _methods);
+					goto out;
+				}
+			}
+			found = 1;
+			break;
+		}
+		if (!found) {
+			error("Unknown authentication method \"%s\" in list",
+			    method);
+			goto out;
+		}
+	}
+	ret = 0;
+ out:
+	free(omethods);
+	return ret;
+}
+
+/*
+ * Prune the AuthenticationMethods supplied in the configuration, removing
+ * any methods lists that include disabled methods. Note that this might
+ * leave authctxt->num_auth_methods == 0, even when multiple required auth
+ * has been requested. For this reason, all tests for whether multiple is
+ * enabled should consult options.num_auth_methods directly.
+ */
+int
+auth2_setup_methods_lists(Authctxt *authctxt)
+{
+	u_int i;
+
+	/* First, normalise away the "any" pseudo-method */
+	if (options.num_auth_methods == 1 &&
+	    strcmp(options.auth_methods[0], "any") == 0) {
+		free(options.auth_methods[0]);
+		options.auth_methods[0] = NULL;
+		options.num_auth_methods = 0;
+	}
+
+	if (options.num_auth_methods == 0)
+		return 0;
+	debug3_f("checking methods");
+	authctxt->auth_methods = xcalloc(options.num_auth_methods,
+	    sizeof(*authctxt->auth_methods));
+	authctxt->num_auth_methods = 0;
+	for (i = 0; i < options.num_auth_methods; i++) {
+		if (auth2_methods_valid(options.auth_methods[i], 1) != 0) {
+			logit("Authentication methods list \"%s\" contains "
+			    "disabled method, skipping",
+			    options.auth_methods[i]);
+			continue;
+		}
+		debug("authentication methods list %d: %s",
+		    authctxt->num_auth_methods, options.auth_methods[i]);
+		authctxt->auth_methods[authctxt->num_auth_methods++] =
+		    xstrdup(options.auth_methods[i]);
+	}
+	if (authctxt->num_auth_methods == 0) {
+		error("No AuthenticationMethods left after eliminating "
+		    "disabled methods");
+		return -1;
+	}
+	return 0;
+}
+
+static int
+list_starts_with(const char *methods, const char *method,
+    const char *submethod)
+{
+	size_t l = strlen(method);
+	int match;
+	const char *p;
+
+	if (strncmp(methods, method, l) != 0)
+		return MATCH_NONE;
+	p = methods + l;
+	match = MATCH_METHOD;
+	if (*p == ':') {
+		if (!submethod)
+			return MATCH_PARTIAL;
+		l = strlen(submethod);
+		p += 1;
+		if (strncmp(submethod, p, l))
+			return MATCH_NONE;
+		p += l;
+		match = MATCH_BOTH;
+	}
+	if (*p != ',' && *p != '\0')
+		return MATCH_NONE;
+	return match;
+}
+
+/*
+ * Remove method from the start of a comma-separated list of methods.
+ * Returns 0 if the list of methods did not start with that method or 1
+ * if it did.
+ */
+static int
+remove_method(char **methods, const char *method, const char *submethod)
+{
+	char *omethods = *methods, *p;
+	size_t l = strlen(method);
+	int match;
+
+	match = list_starts_with(omethods, method, submethod);
+	if (match != MATCH_METHOD && match != MATCH_BOTH)
+		return 0;
+	p = omethods + l;
+	if (submethod && match == MATCH_BOTH)
+		p += 1 + strlen(submethod); /* include colon */
+	if (*p == ',')
+		p++;
+	*methods = xstrdup(p);
+	free(omethods);
+	return 1;
+}
+
+/*
+ * Called after successful authentication. Will remove the successful method
+ * from the start of each list in which it occurs. If it was the last method
+ * in any list, then authentication is deemed successful.
+ * Returns 1 if the method completed any authentication list or 0 otherwise.
+ */
+int
+auth2_update_methods_lists(Authctxt *authctxt, const char *method,
+    const char *submethod)
+{
+	u_int i, found = 0;
+
+	debug3_f("updating methods list after \"%s\"", method);
+	for (i = 0; i < authctxt->num_auth_methods; i++) {
+		if (!remove_method(&(authctxt->auth_methods[i]), method,
+		    submethod))
+			continue;
+		found = 1;
+		if (*authctxt->auth_methods[i] == '\0') {
+			debug2("authentication methods list %d complete", i);
+			return 1;
+		}
+		debug3("authentication methods list %d remaining: \"%s\"",
+		    i, authctxt->auth_methods[i]);
+	}
+	/* This should not happen, but would be bad if it did */
+	if (!found)
+		fatal_f("method not in AuthenticationMethods");
+	return 0;
+}
+
+/* Reset method-specific information */
+void auth2_authctxt_reset_info(Authctxt *authctxt)
+{
+	sshkey_free(authctxt->auth_method_key);
+	free(authctxt->auth_method_info);
+	authctxt->auth_method_key = NULL;
+	authctxt->auth_method_info = NULL;
+}
+
+/* Record auth method-specific information for logs */
+void
+auth2_record_info(Authctxt *authctxt, const char *fmt, ...)
+{
+	va_list ap;
+	int i;
+
+	free(authctxt->auth_method_info);
+	authctxt->auth_method_info = NULL;
+
+	va_start(ap, fmt);
+	i = vasprintf(&authctxt->auth_method_info, fmt, ap);
+	va_end(ap);
+
+	if (i == -1)
+		fatal_f("vasprintf failed");
+}
+
+/*
+ * Records a public key used in authentication. This is used for logging
+ * and to ensure that the same key is not subsequently accepted again for
+ * multiple authentication.
+ */
+void
+auth2_record_key(Authctxt *authctxt, int authenticated,
+    const struct sshkey *key)
+{
+	struct sshkey **tmp, *dup;
+	int r;
+
+	if ((r = sshkey_from_private(key, &dup)) != 0)
+		fatal_fr(r, "copy key");
+	sshkey_free(authctxt->auth_method_key);
+	authctxt->auth_method_key = dup;
+
+	if (!authenticated)
+		return;
+
+	/* If authenticated, make sure we don't accept this key again */
+	if ((r = sshkey_from_private(key, &dup)) != 0)
+		fatal_fr(r, "copy key");
+	if (authctxt->nprev_keys >= INT_MAX ||
+	    (tmp = recallocarray(authctxt->prev_keys, authctxt->nprev_keys,
+	    authctxt->nprev_keys + 1, sizeof(*authctxt->prev_keys))) == NULL)
+		fatal_f("reallocarray failed");
+	authctxt->prev_keys = tmp;
+	authctxt->prev_keys[authctxt->nprev_keys] = dup;
+	authctxt->nprev_keys++;
+
+}
+
+/* Checks whether a key has already been previously used for authentication */
+int
+auth2_key_already_used(Authctxt *authctxt, const struct sshkey *key)
+{
+	u_int i;
+	char *fp;
+
+	for (i = 0; i < authctxt->nprev_keys; i++) {
+		if (sshkey_equal_public(key, authctxt->prev_keys[i])) {
+			fp = sshkey_fingerprint(authctxt->prev_keys[i],
+			    options.fingerprint_hash, SSH_FP_DEFAULT);
+			debug3_f("key already used: %s %s",
+			    sshkey_type(authctxt->prev_keys[i]),
+			    fp == NULL ? "UNKNOWN" : fp);
+			free(fp);
+			return 1;
+		}
+	}
+	return 0;
+}
+
+/*
+ * Updates authctxt->session_info with details of authentication. Should be
+ * whenever an authentication method succeeds.
+ */
+void
+auth2_update_session_info(Authctxt *authctxt, const char *method,
+    const char *submethod)
+{
+	int r;
+
+	if (authctxt->session_info == NULL) {
+		if ((authctxt->session_info = sshbuf_new()) == NULL)
+			fatal_f("sshbuf_new");
+	}
+
+	/* Append method[/submethod] */
+	if ((r = sshbuf_putf(authctxt->session_info, "%s%s%s",
+	    method, submethod == NULL ? "" : "/",
+	    submethod == NULL ? "" : submethod)) != 0)
+		fatal_fr(r, "append method");
+
+	/* Append key if present */
+	if (authctxt->auth_method_key != NULL) {
+		if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 ||
+		    (r = sshkey_format_text(authctxt->auth_method_key,
+		    authctxt->session_info)) != 0)
+			fatal_fr(r, "append key");
+	}
+
+	if (authctxt->auth_method_info != NULL) {
+		/* Ensure no ambiguity here */
+		if (strchr(authctxt->auth_method_info, '\n') != NULL)
+			fatal_f("auth_method_info contains \\n");
+		if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 ||
+		    (r = sshbuf_putf(authctxt->session_info, "%s",
+		    authctxt->auth_method_info)) != 0) {
+			fatal_fr(r, "append method info");
+		}
+	}
+	if ((r = sshbuf_put_u8(authctxt->session_info, '\n')) != 0)
+		fatal_fr(r, "append");
+}
+