From 25505898530a333011f4fd5cbc841ad6b26c089c Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 16:40:04 +0200 Subject: Adding upstream version 1:9.2p1. Signed-off-by: Daniel Baumann --- auth2-hostbased.c | 266 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 266 insertions(+) create mode 100644 auth2-hostbased.c (limited to 'auth2-hostbased.c') diff --git a/auth2-hostbased.c b/auth2-hostbased.c new file mode 100644 index 0000000..6b517db --- /dev/null +++ b/auth2-hostbased.c @@ -0,0 +1,266 @@ +/* $OpenBSD: auth2-hostbased.c,v 1.50 2022/09/17 10:34:29 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 + +#include +#include +#include +#include + +#include "xmalloc.h" +#include "ssh2.h" +#include "packet.h" +#include "kex.h" +#include "sshbuf.h" +#include "log.h" +#include "misc.h" +#include "servconf.h" +#include "compat.h" +#include "sshkey.h" +#include "hostfile.h" +#include "auth.h" +#include "canohost.h" +#ifdef GSSAPI +#include "ssh-gss.h" +#endif +#include "monitor_wrap.h" +#include "pathnames.h" +#include "ssherr.h" +#include "match.h" + +/* import */ +extern ServerOptions options; + +static int +userauth_hostbased(struct ssh *ssh, const char *method) +{ + Authctxt *authctxt = ssh->authctxt; + struct sshbuf *b; + struct sshkey *key = NULL; + char *pkalg, *cuser, *chost; + u_char *pkblob, *sig; + size_t alen, blen, slen; + int r, pktype, authenticated = 0; + + /* XXX use sshkey_froms() */ + if ((r = sshpkt_get_cstring(ssh, &pkalg, &alen)) != 0 || + (r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0 || + (r = sshpkt_get_cstring(ssh, &chost, NULL)) != 0 || + (r = sshpkt_get_cstring(ssh, &cuser, NULL)) != 0 || + (r = sshpkt_get_string(ssh, &sig, &slen)) != 0) + fatal_fr(r, "parse packet"); + + debug_f("cuser %s chost %s pkalg %s slen %zu", + cuser, chost, pkalg, slen); +#ifdef DEBUG_PK + debug("signature:"); + sshbuf_dump_data(sig, slen, stderr); +#endif + pktype = sshkey_type_from_name(pkalg); + if (pktype == KEY_UNSPEC) { + /* this is perfectly legal */ + logit_f("unsupported public key algorithm: %s", + pkalg); + goto done; + } + if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) { + error_fr(r, "key_from_blob"); + goto done; + } + if (key == NULL) { + error_f("cannot decode key: %s", pkalg); + goto done; + } + if (key->type != pktype) { + error_f("type mismatch for decoded key " + "(received %d, expected %d)", key->type, pktype); + goto done; + } + if (sshkey_type_plain(key->type) == KEY_RSA && + (ssh->compat & SSH_BUG_RSASIGMD5) != 0) { + error("Refusing RSA key because peer uses unsafe " + "signature format"); + goto done; + } + if (match_pattern_list(pkalg, options.hostbased_accepted_algos, 0) != 1) { + logit_f("signature algorithm %s not in " + "HostbasedAcceptedAlgorithms", pkalg); + goto done; + } + if ((r = sshkey_check_cert_sigtype(key, + options.ca_sign_algorithms)) != 0) { + logit_fr(r, "certificate signature algorithm %s", + (key->cert == NULL || key->cert->signature_type == NULL) ? + "(null)" : key->cert->signature_type); + goto done; + } + if ((r = sshkey_check_rsa_length(key, + options.required_rsa_size)) != 0) { + logit_r(r, "refusing %s key", sshkey_type(key)); + goto done; + } + + if (!authctxt->valid || authctxt->user == NULL) { + debug2_f("disabled because of invalid user"); + goto done; + } + + if ((b = sshbuf_new()) == NULL) + fatal_f("sshbuf_new failed"); + /* reconstruct packet */ + if ((r = sshbuf_put_stringb(b, ssh->kex->session_id)) != 0 || + (r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 || + (r = sshbuf_put_cstring(b, authctxt->user)) != 0 || + (r = sshbuf_put_cstring(b, authctxt->service)) != 0 || + (r = sshbuf_put_cstring(b, method)) != 0 || + (r = sshbuf_put_string(b, pkalg, alen)) != 0 || + (r = sshbuf_put_string(b, pkblob, blen)) != 0 || + (r = sshbuf_put_cstring(b, chost)) != 0 || + (r = sshbuf_put_cstring(b, cuser)) != 0) + fatal_fr(r, "reconstruct packet"); +#ifdef DEBUG_PK + sshbuf_dump(b, stderr); +#endif + + auth2_record_info(authctxt, + "client user \"%.100s\", client host \"%.100s\"", cuser, chost); + + /* test for allowed key and correct signature */ + authenticated = 0; + if (PRIVSEP(hostbased_key_allowed(ssh, authctxt->pw, cuser, + chost, key)) && + PRIVSEP(sshkey_verify(key, sig, slen, + sshbuf_ptr(b), sshbuf_len(b), pkalg, ssh->compat, NULL)) == 0) + authenticated = 1; + + auth2_record_key(authctxt, authenticated, key); + sshbuf_free(b); +done: + debug2_f("authenticated %d", authenticated); + sshkey_free(key); + free(pkalg); + free(pkblob); + free(cuser); + free(chost); + free(sig); + return authenticated; +} + +/* return 1 if given hostkey is allowed */ +int +hostbased_key_allowed(struct ssh *ssh, struct passwd *pw, + const char *cuser, char *chost, struct sshkey *key) +{ + const char *resolvedname, *ipaddr, *lookup, *reason; + HostStatus host_status; + int len; + char *fp; + + if (auth_key_is_revoked(key)) + return 0; + + resolvedname = auth_get_canonical_hostname(ssh, options.use_dns); + ipaddr = ssh_remote_ipaddr(ssh); + + debug2_f("chost %s resolvedname %s ipaddr %s", + chost, resolvedname, ipaddr); + + if (((len = strlen(chost)) > 0) && chost[len - 1] == '.') { + debug2("stripping trailing dot from chost %s", chost); + chost[len - 1] = '\0'; + } + + if (options.hostbased_uses_name_from_packet_only) { + if (auth_rhosts2(pw, cuser, chost, chost) == 0) { + debug2_f("auth_rhosts2 refused user \"%.100s\" " + "host \"%.100s\" (from packet)", cuser, chost); + return 0; + } + lookup = chost; + } else { + if (strcasecmp(resolvedname, chost) != 0) + logit("userauth_hostbased mismatch: " + "client sends %s, but we resolve %s to %s", + chost, ipaddr, resolvedname); + if (auth_rhosts2(pw, cuser, resolvedname, ipaddr) == 0) { + debug2_f("auth_rhosts2 refused " + "user \"%.100s\" host \"%.100s\" addr \"%.100s\"", + cuser, resolvedname, ipaddr); + return 0; + } + lookup = resolvedname; + } + debug2_f("access allowed by auth_rhosts2"); + + if (sshkey_is_cert(key) && + sshkey_cert_check_authority_now(key, 1, 0, 0, lookup, &reason)) { + error("%s", reason); + auth_debug_add("%s", reason); + return 0; + } + + host_status = check_key_in_hostfiles(pw, key, lookup, + _PATH_SSH_SYSTEM_HOSTFILE, + options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE); + + /* backward compat if no key has been found. */ + if (host_status == HOST_NEW) { + host_status = check_key_in_hostfiles(pw, key, lookup, + _PATH_SSH_SYSTEM_HOSTFILE2, + options.ignore_user_known_hosts ? NULL : + _PATH_SSH_USER_HOSTFILE2); + } + + if (host_status == HOST_OK) { + if (sshkey_is_cert(key)) { + if ((fp = sshkey_fingerprint(key->cert->signature_key, + options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) + fatal_f("sshkey_fingerprint fail"); + verbose("Accepted certificate ID \"%s\" signed by " + "%s CA %s from %s@%s", key->cert->key_id, + sshkey_type(key->cert->signature_key), fp, + cuser, lookup); + } else { + if ((fp = sshkey_fingerprint(key, + options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) + fatal_f("sshkey_fingerprint fail"); + verbose("Accepted %s public key %s from %s@%s", + sshkey_type(key), fp, cuser, lookup); + } + free(fp); + } + + return (host_status == HOST_OK); +} + +Authmethod method_hostbased = { + "hostbased", + NULL, + userauth_hostbased, + &options.hostbased_authentication +}; -- cgit v1.2.3