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-rw-r--r--auth.c1191
1 files changed, 1191 insertions, 0 deletions
diff --git a/auth.c b/auth.c
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+++ b/auth.c
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+/* $OpenBSD: auth.c,v 1.147 2020/08/27 01:07:09 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/socket.h>
+#include <sys/wait.h>
+
+#include <netinet/in.h>
+
+#include <stdlib.h>
+#include <errno.h>
+#include <fcntl.h>
+#ifdef HAVE_PATHS_H
+# include <paths.h>
+#endif
+#include <pwd.h>
+#ifdef HAVE_LOGIN_H
+#include <login.h>
+#endif
+#ifdef USE_SHADOW
+#include <shadow.h>
+#endif
+#include <stdarg.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <limits.h>
+#include <netdb.h>
+#include <time.h>
+
+#include "xmalloc.h"
+#include "match.h"
+#include "groupaccess.h"
+#include "log.h"
+#include "sshbuf.h"
+#include "misc.h"
+#include "servconf.h"
+#include "sshkey.h"
+#include "hostfile.h"
+#include "auth.h"
+#include "auth-options.h"
+#include "canohost.h"
+#include "uidswap.h"
+#include "packet.h"
+#include "loginrec.h"
+#ifdef GSSAPI
+#include "ssh-gss.h"
+#endif
+#include "authfile.h"
+#include "monitor_wrap.h"
+#include "ssherr.h"
+#include "compat.h"
+#include "channels.h"
+
+/* import */
+extern ServerOptions options;
+extern struct include_list includes;
+extern int use_privsep;
+extern struct sshbuf *loginmsg;
+extern struct passwd *privsep_pw;
+extern struct sshauthopt *auth_opts;
+
+/* Debugging messages */
+static struct sshbuf *auth_debug;
+
+/*
+ * Check if the user is allowed to log in via ssh. If user is listed
+ * in DenyUsers or one of user's groups is listed in DenyGroups, false
+ * will be returned. If AllowUsers isn't empty and user isn't listed
+ * there, or if AllowGroups isn't empty and one of user's groups isn't
+ * listed there, false will be returned.
+ * If the user's shell is not executable, false will be returned.
+ * Otherwise true is returned.
+ */
+int
+allowed_user(struct ssh *ssh, struct passwd * pw)
+{
+ struct stat st;
+ const char *hostname = NULL, *ipaddr = NULL, *passwd = NULL;
+ u_int i;
+ int r;
+#ifdef USE_SHADOW
+ struct spwd *spw = NULL;
+#endif
+
+ /* Shouldn't be called if pw is NULL, but better safe than sorry... */
+ if (!pw || !pw->pw_name)
+ return 0;
+
+#ifdef USE_SHADOW
+ if (!options.use_pam)
+ spw = getspnam(pw->pw_name);
+#ifdef HAS_SHADOW_EXPIRE
+ if (!options.use_pam && spw != NULL && auth_shadow_acctexpired(spw))
+ return 0;
+#endif /* HAS_SHADOW_EXPIRE */
+#endif /* USE_SHADOW */
+
+ /* grab passwd field for locked account check */
+ passwd = pw->pw_passwd;
+#ifdef USE_SHADOW
+ if (spw != NULL)
+#ifdef USE_LIBIAF
+ passwd = get_iaf_password(pw);
+#else
+ passwd = spw->sp_pwdp;
+#endif /* USE_LIBIAF */
+#endif
+
+ /* check for locked account */
+ if (!options.use_pam && passwd && *passwd) {
+ int locked = 0;
+
+#ifdef LOCKED_PASSWD_STRING
+ if (strcmp(passwd, LOCKED_PASSWD_STRING) == 0)
+ locked = 1;
+#endif
+#ifdef LOCKED_PASSWD_PREFIX
+ if (strncmp(passwd, LOCKED_PASSWD_PREFIX,
+ strlen(LOCKED_PASSWD_PREFIX)) == 0)
+ locked = 1;
+#endif
+#ifdef LOCKED_PASSWD_SUBSTR
+ if (strstr(passwd, LOCKED_PASSWD_SUBSTR))
+ locked = 1;
+#endif
+#ifdef USE_LIBIAF
+ free((void *) passwd);
+#endif /* USE_LIBIAF */
+ if (locked) {
+ logit("User %.100s not allowed because account is locked",
+ pw->pw_name);
+ return 0;
+ }
+ }
+
+ /*
+ * Deny if shell does not exist or is not executable unless we
+ * are chrooting.
+ */
+ if (options.chroot_directory == NULL ||
+ strcasecmp(options.chroot_directory, "none") == 0) {
+ char *shell = xstrdup((pw->pw_shell[0] == '\0') ?
+ _PATH_BSHELL : pw->pw_shell); /* empty = /bin/sh */
+
+ if (stat(shell, &st) == -1) {
+ logit("User %.100s not allowed because shell %.100s "
+ "does not exist", pw->pw_name, shell);
+ free(shell);
+ return 0;
+ }
+ if (S_ISREG(st.st_mode) == 0 ||
+ (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) {
+ logit("User %.100s not allowed because shell %.100s "
+ "is not executable", pw->pw_name, shell);
+ free(shell);
+ return 0;
+ }
+ free(shell);
+ }
+
+ if (options.num_deny_users > 0 || options.num_allow_users > 0 ||
+ options.num_deny_groups > 0 || options.num_allow_groups > 0) {
+ hostname = auth_get_canonical_hostname(ssh, options.use_dns);
+ ipaddr = ssh_remote_ipaddr(ssh);
+ }
+
+ /* Return false if user is listed in DenyUsers */
+ if (options.num_deny_users > 0) {
+ for (i = 0; i < options.num_deny_users; i++) {
+ r = match_user(pw->pw_name, hostname, ipaddr,
+ options.deny_users[i]);
+ if (r < 0) {
+ fatal("Invalid DenyUsers pattern \"%.100s\"",
+ options.deny_users[i]);
+ } else if (r != 0) {
+ logit("User %.100s from %.100s not allowed "
+ "because listed in DenyUsers",
+ pw->pw_name, hostname);
+ return 0;
+ }
+ }
+ }
+ /* Return false if AllowUsers isn't empty and user isn't listed there */
+ if (options.num_allow_users > 0) {
+ for (i = 0; i < options.num_allow_users; i++) {
+ r = match_user(pw->pw_name, hostname, ipaddr,
+ options.allow_users[i]);
+ if (r < 0) {
+ fatal("Invalid AllowUsers pattern \"%.100s\"",
+ options.allow_users[i]);
+ } else if (r == 1)
+ break;
+ }
+ /* i < options.num_allow_users iff we break for loop */
+ if (i >= options.num_allow_users) {
+ logit("User %.100s from %.100s not allowed because "
+ "not listed in AllowUsers", pw->pw_name, hostname);
+ return 0;
+ }
+ }
+ if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
+ /* Get the user's group access list (primary and supplementary) */
+ if (ga_init(pw->pw_name, pw->pw_gid) == 0) {
+ logit("User %.100s from %.100s not allowed because "
+ "not in any group", pw->pw_name, hostname);
+ return 0;
+ }
+
+ /* Return false if one of user's groups is listed in DenyGroups */
+ if (options.num_deny_groups > 0)
+ if (ga_match(options.deny_groups,
+ options.num_deny_groups)) {
+ ga_free();
+ logit("User %.100s from %.100s not allowed "
+ "because a group is listed in DenyGroups",
+ pw->pw_name, hostname);
+ return 0;
+ }
+ /*
+ * Return false if AllowGroups isn't empty and one of user's groups
+ * isn't listed there
+ */
+ if (options.num_allow_groups > 0)
+ if (!ga_match(options.allow_groups,
+ options.num_allow_groups)) {
+ ga_free();
+ logit("User %.100s from %.100s not allowed "
+ "because none of user's groups are listed "
+ "in AllowGroups", pw->pw_name, hostname);
+ return 0;
+ }
+ ga_free();
+ }
+
+#ifdef CUSTOM_SYS_AUTH_ALLOWED_USER
+ if (!sys_auth_allowed_user(pw, loginmsg))
+ return 0;
+#endif
+
+ /* We found no reason not to let this user try to log on... */
+ return 1;
+}
+
+/*
+ * Formats any key left in authctxt->auth_method_key for inclusion in
+ * auth_log()'s message. Also includes authxtct->auth_method_info if present.
+ */
+static char *
+format_method_key(Authctxt *authctxt)
+{
+ const struct sshkey *key = authctxt->auth_method_key;
+ const char *methinfo = authctxt->auth_method_info;
+ char *fp, *cafp, *ret = NULL;
+
+ if (key == NULL)
+ return NULL;
+
+ if (sshkey_is_cert(key)) {
+ fp = sshkey_fingerprint(key,
+ options.fingerprint_hash, SSH_FP_DEFAULT);
+ cafp = sshkey_fingerprint(key->cert->signature_key,
+ options.fingerprint_hash, SSH_FP_DEFAULT);
+ xasprintf(&ret, "%s %s ID %s (serial %llu) CA %s %s%s%s",
+ sshkey_type(key), fp == NULL ? "(null)" : fp,
+ key->cert->key_id,
+ (unsigned long long)key->cert->serial,
+ sshkey_type(key->cert->signature_key),
+ cafp == NULL ? "(null)" : cafp,
+ methinfo == NULL ? "" : ", ",
+ methinfo == NULL ? "" : methinfo);
+ free(fp);
+ free(cafp);
+ } else {
+ fp = sshkey_fingerprint(key, options.fingerprint_hash,
+ SSH_FP_DEFAULT);
+ xasprintf(&ret, "%s %s%s%s", sshkey_type(key),
+ fp == NULL ? "(null)" : fp,
+ methinfo == NULL ? "" : ", ",
+ methinfo == NULL ? "" : methinfo);
+ free(fp);
+ }
+ return ret;
+}
+
+void
+auth_log(struct ssh *ssh, int authenticated, int partial,
+ const char *method, const char *submethod)
+{
+ Authctxt *authctxt = (Authctxt *)ssh->authctxt;
+ int level = SYSLOG_LEVEL_VERBOSE;
+ const char *authmsg;
+ char *extra = NULL;
+
+ if (use_privsep && !mm_is_monitor() && !authctxt->postponed)
+ return;
+
+ /* Raise logging level */
+ if (authenticated == 1 ||
+ !authctxt->valid ||
+ authctxt->failures >= options.max_authtries / 2 ||
+ strcmp(method, "password") == 0)
+ level = SYSLOG_LEVEL_INFO;
+
+ if (authctxt->postponed)
+ authmsg = "Postponed";
+ else if (partial)
+ authmsg = "Partial";
+ else
+ authmsg = authenticated ? "Accepted" : "Failed";
+
+ if ((extra = format_method_key(authctxt)) == NULL) {
+ if (authctxt->auth_method_info != NULL)
+ extra = xstrdup(authctxt->auth_method_info);
+ }
+
+ do_log2(level, "%s %s%s%s for %s%.100s from %.200s port %d ssh2%s%s",
+ authmsg,
+ method,
+ submethod != NULL ? "/" : "", submethod == NULL ? "" : submethod,
+ authctxt->valid ? "" : "invalid user ",
+ authctxt->user,
+ ssh_remote_ipaddr(ssh),
+ ssh_remote_port(ssh),
+ extra != NULL ? ": " : "",
+ extra != NULL ? extra : "");
+
+ free(extra);
+
+#ifdef CUSTOM_FAILED_LOGIN
+ if (authenticated == 0 && !authctxt->postponed &&
+ (strcmp(method, "password") == 0 ||
+ strncmp(method, "keyboard-interactive", 20) == 0 ||
+ strcmp(method, "challenge-response") == 0))
+ record_failed_login(ssh, authctxt->user,
+ auth_get_canonical_hostname(ssh, options.use_dns), "ssh");
+# ifdef WITH_AIXAUTHENTICATE
+ if (authenticated)
+ sys_auth_record_login(authctxt->user,
+ auth_get_canonical_hostname(ssh, options.use_dns), "ssh",
+ loginmsg);
+# endif
+#endif
+#ifdef SSH_AUDIT_EVENTS
+ if (authenticated == 0 && !authctxt->postponed)
+ audit_event(ssh, audit_classify_auth(method));
+#endif
+}
+
+
+void
+auth_maxtries_exceeded(struct ssh *ssh)
+{
+ Authctxt *authctxt = (Authctxt *)ssh->authctxt;
+
+ error("maximum authentication attempts exceeded for "
+ "%s%.100s from %.200s port %d ssh2",
+ authctxt->valid ? "" : "invalid user ",
+ authctxt->user,
+ ssh_remote_ipaddr(ssh),
+ ssh_remote_port(ssh));
+ ssh_packet_disconnect(ssh, "Too many authentication failures");
+ /* NOTREACHED */
+}
+
+/*
+ * Check whether root logins are disallowed.
+ */
+int
+auth_root_allowed(struct ssh *ssh, const char *method)
+{
+ switch (options.permit_root_login) {
+ case PERMIT_YES:
+ return 1;
+ case PERMIT_NO_PASSWD:
+ if (strcmp(method, "publickey") == 0 ||
+ strcmp(method, "hostbased") == 0 ||
+ strcmp(method, "gssapi-with-mic") == 0)
+ return 1;
+ break;
+ case PERMIT_FORCED_ONLY:
+ if (auth_opts->force_command != NULL) {
+ logit("Root login accepted for forced command.");
+ return 1;
+ }
+ break;
+ }
+ logit("ROOT LOGIN REFUSED FROM %.200s port %d",
+ ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
+ return 0;
+}
+
+
+/*
+ * Given a template and a passwd structure, build a filename
+ * by substituting % tokenised options. Currently, %% becomes '%',
+ * %h becomes the home directory and %u the username.
+ *
+ * This returns a buffer allocated by xmalloc.
+ */
+char *
+expand_authorized_keys(const char *filename, struct passwd *pw)
+{
+ char *file, uidstr[32], ret[PATH_MAX];
+ int i;
+
+ snprintf(uidstr, sizeof(uidstr), "%llu",
+ (unsigned long long)pw->pw_uid);
+ file = percent_expand(filename, "h", pw->pw_dir,
+ "u", pw->pw_name, "U", uidstr, (char *)NULL);
+
+ /*
+ * Ensure that filename starts anchored. If not, be backward
+ * compatible and prepend the '%h/'
+ */
+ if (path_absolute(file))
+ return (file);
+
+ i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file);
+ if (i < 0 || (size_t)i >= sizeof(ret))
+ fatal("expand_authorized_keys: path too long");
+ free(file);
+ return (xstrdup(ret));
+}
+
+char *
+authorized_principals_file(struct passwd *pw)
+{
+ if (options.authorized_principals_file == NULL)
+ return NULL;
+ return expand_authorized_keys(options.authorized_principals_file, pw);
+}
+
+/* return ok if key exists in sysfile or userfile */
+HostStatus
+check_key_in_hostfiles(struct passwd *pw, struct sshkey *key, const char *host,
+ const char *sysfile, const char *userfile)
+{
+ char *user_hostfile;
+ struct stat st;
+ HostStatus host_status;
+ struct hostkeys *hostkeys;
+ const struct hostkey_entry *found;
+
+ hostkeys = init_hostkeys();
+ load_hostkeys(hostkeys, host, sysfile);
+ if (userfile != NULL) {
+ user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
+ if (options.strict_modes &&
+ (stat(user_hostfile, &st) == 0) &&
+ ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
+ (st.st_mode & 022) != 0)) {
+ logit("Authentication refused for %.100s: "
+ "bad owner or modes for %.200s",
+ pw->pw_name, user_hostfile);
+ auth_debug_add("Ignored %.200s: bad ownership or modes",
+ user_hostfile);
+ } else {
+ temporarily_use_uid(pw);
+ load_hostkeys(hostkeys, host, user_hostfile);
+ restore_uid();
+ }
+ free(user_hostfile);
+ }
+ host_status = check_key_in_hostkeys(hostkeys, key, &found);
+ if (host_status == HOST_REVOKED)
+ error("WARNING: revoked key for %s attempted authentication",
+ host);
+ else if (host_status == HOST_OK)
+ debug("%s: key for %s found at %s:%ld", __func__,
+ found->host, found->file, found->line);
+ else
+ debug("%s: key for host %s not found", __func__, host);
+
+ free_hostkeys(hostkeys);
+
+ return host_status;
+}
+
+static FILE *
+auth_openfile(const char *file, struct passwd *pw, int strict_modes,
+ int log_missing, char *file_type)
+{
+ char line[1024];
+ struct stat st;
+ int fd;
+ FILE *f;
+
+ if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) {
+ if (log_missing || errno != ENOENT)
+ debug("Could not open %s '%s': %s", file_type, file,
+ strerror(errno));
+ return NULL;
+ }
+
+ if (fstat(fd, &st) == -1) {
+ close(fd);
+ return NULL;
+ }
+ if (!S_ISREG(st.st_mode)) {
+ logit("User %s %s %s is not a regular file",
+ pw->pw_name, file_type, file);
+ close(fd);
+ return NULL;
+ }
+ unset_nonblock(fd);
+ if ((f = fdopen(fd, "r")) == NULL) {
+ close(fd);
+ return NULL;
+ }
+ if (strict_modes &&
+ safe_path_fd(fileno(f), file, pw, line, sizeof(line)) != 0) {
+ fclose(f);
+ logit("Authentication refused: %s", line);
+ auth_debug_add("Ignored %s: %s", file_type, line);
+ return NULL;
+ }
+
+ return f;
+}
+
+
+FILE *
+auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes)
+{
+ return auth_openfile(file, pw, strict_modes, 1, "authorized keys");
+}
+
+FILE *
+auth_openprincipals(const char *file, struct passwd *pw, int strict_modes)
+{
+ return auth_openfile(file, pw, strict_modes, 0,
+ "authorized principals");
+}
+
+struct passwd *
+getpwnamallow(struct ssh *ssh, const char *user)
+{
+#ifdef HAVE_LOGIN_CAP
+ extern login_cap_t *lc;
+#ifdef BSD_AUTH
+ auth_session_t *as;
+#endif
+#endif
+ struct passwd *pw;
+ struct connection_info *ci;
+
+ ci = get_connection_info(ssh, 1, options.use_dns);
+ ci->user = user;
+ parse_server_match_config(&options, &includes, ci);
+ log_change_level(options.log_level);
+ process_permitopen(ssh, &options);
+
+#if defined(_AIX) && defined(HAVE_SETAUTHDB)
+ aix_setauthdb(user);
+#endif
+
+ pw = getpwnam(user);
+
+#if defined(_AIX) && defined(HAVE_SETAUTHDB)
+ aix_restoreauthdb();
+#endif
+ if (pw == NULL) {
+ logit("Invalid user %.100s from %.100s port %d",
+ user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
+#ifdef CUSTOM_FAILED_LOGIN
+ record_failed_login(ssh, user,
+ auth_get_canonical_hostname(ssh, options.use_dns), "ssh");
+#endif
+#ifdef SSH_AUDIT_EVENTS
+ audit_event(ssh, SSH_INVALID_USER);
+#endif /* SSH_AUDIT_EVENTS */
+ return (NULL);
+ }
+ if (!allowed_user(ssh, pw))
+ return (NULL);
+#ifdef HAVE_LOGIN_CAP
+ if ((lc = login_getclass(pw->pw_class)) == NULL) {
+ debug("unable to get login class: %s", user);
+ return (NULL);
+ }
+#ifdef BSD_AUTH
+ if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
+ auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
+ debug("Approval failure for %s", user);
+ pw = NULL;
+ }
+ if (as != NULL)
+ auth_close(as);
+#endif
+#endif
+ if (pw != NULL)
+ return (pwcopy(pw));
+ return (NULL);
+}
+
+/* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */
+int
+auth_key_is_revoked(struct sshkey *key)
+{
+ char *fp = NULL;
+ int r;
+
+ if (options.revoked_keys_file == NULL)
+ return 0;
+ if ((fp = sshkey_fingerprint(key, options.fingerprint_hash,
+ SSH_FP_DEFAULT)) == NULL) {
+ r = SSH_ERR_ALLOC_FAIL;
+ error("%s: fingerprint key: %s", __func__, ssh_err(r));
+ goto out;
+ }
+
+ r = sshkey_check_revoked(key, options.revoked_keys_file);
+ switch (r) {
+ case 0:
+ break; /* not revoked */
+ case SSH_ERR_KEY_REVOKED:
+ error("Authentication key %s %s revoked by file %s",
+ sshkey_type(key), fp, options.revoked_keys_file);
+ goto out;
+ default:
+ error("Error checking authentication key %s %s in "
+ "revoked keys file %s: %s", sshkey_type(key), fp,
+ options.revoked_keys_file, ssh_err(r));
+ goto out;
+ }
+
+ /* Success */
+ r = 0;
+
+ out:
+ free(fp);
+ return r == 0 ? 0 : 1;
+}
+
+void
+auth_debug_add(const char *fmt,...)
+{
+ char buf[1024];
+ va_list args;
+ int r;
+
+ if (auth_debug == NULL)
+ return;
+
+ va_start(args, fmt);
+ vsnprintf(buf, sizeof(buf), fmt, args);
+ va_end(args);
+ if ((r = sshbuf_put_cstring(auth_debug, buf)) != 0)
+ fatal("%s: sshbuf_put_cstring: %s", __func__, ssh_err(r));
+}
+
+void
+auth_debug_send(struct ssh *ssh)
+{
+ char *msg;
+ int r;
+
+ if (auth_debug == NULL)
+ return;
+ while (sshbuf_len(auth_debug) != 0) {
+ if ((r = sshbuf_get_cstring(auth_debug, &msg, NULL)) != 0)
+ fatal("%s: sshbuf_get_cstring: %s",
+ __func__, ssh_err(r));
+ ssh_packet_send_debug(ssh, "%s", msg);
+ free(msg);
+ }
+}
+
+void
+auth_debug_reset(void)
+{
+ if (auth_debug != NULL)
+ sshbuf_reset(auth_debug);
+ else if ((auth_debug = sshbuf_new()) == NULL)
+ fatal("%s: sshbuf_new failed", __func__);
+}
+
+struct passwd *
+fakepw(void)
+{
+ static struct passwd fake;
+
+ memset(&fake, 0, sizeof(fake));
+ fake.pw_name = "NOUSER";
+ fake.pw_passwd =
+ "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK";
+#ifdef HAVE_STRUCT_PASSWD_PW_GECOS
+ fake.pw_gecos = "NOUSER";
+#endif
+ fake.pw_uid = privsep_pw == NULL ? (uid_t)-1 : privsep_pw->pw_uid;
+ fake.pw_gid = privsep_pw == NULL ? (gid_t)-1 : privsep_pw->pw_gid;
+#ifdef HAVE_STRUCT_PASSWD_PW_CLASS
+ fake.pw_class = "";
+#endif
+ fake.pw_dir = "/nonexist";
+ fake.pw_shell = "/nonexist";
+
+ 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 legacy rhosts-style authentication.
+ * XXX is RhostsRSAAuthentication vulnerable to these?
+ * XXX Can we remove these checks? (or if not, remove RhostsRSAAuthentication?)
+ */
+
+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
+ * several times.
+ */
+
+const char *
+auth_get_canonical_hostname(struct ssh *ssh, int use_dns)
+{
+ static char *dnsname;
+
+ if (!use_dns)
+ return ssh_remote_ipaddr(ssh);
+ else if (dnsname != NULL)
+ return dnsname;
+ else {
+ dnsname = remote_hostname(ssh);
+ return dnsname;
+ }
+}
+
+/*
+ * Runs command in a subprocess with a minimal environment.
+ * Returns pid on success, 0 on failure.
+ * The child stdout and stderr maybe captured, left attached or sent to
+ * /dev/null depending on the contents of flags.
+ * "tag" is prepended to log messages.
+ * NB. "command" is only used for logging; the actual command executed is
+ * av[0].
+ */
+pid_t
+subprocess(const char *tag, struct passwd *pw, const char *command,
+ int ac, char **av, FILE **child, u_int flags)
+{
+ FILE *f = NULL;
+ struct stat st;
+ int fd, devnull, p[2], i;
+ pid_t pid;
+ char *cp, errmsg[512];
+ u_int envsize;
+ char **child_env;
+
+ if (child != NULL)
+ *child = NULL;
+
+ debug3("%s: %s command \"%s\" running as %s (flags 0x%x)", __func__,
+ tag, command, pw->pw_name, flags);
+
+ /* Check consistency */
+ if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 &&
+ (flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0) {
+ error("%s: inconsistent flags", __func__);
+ return 0;
+ }
+ if (((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0) != (child == NULL)) {
+ error("%s: inconsistent flags/output", __func__);
+ return 0;
+ }
+
+ /*
+ * If executing an explicit binary, then verify the it exists
+ * and appears safe-ish to execute
+ */
+ if (!path_absolute(av[0])) {
+ error("%s path is not absolute", tag);
+ return 0;
+ }
+ temporarily_use_uid(pw);
+ if (stat(av[0], &st) == -1) {
+ error("Could not stat %s \"%s\": %s", tag,
+ av[0], strerror(errno));
+ restore_uid();
+ return 0;
+ }
+ if (safe_path(av[0], &st, NULL, 0, errmsg, sizeof(errmsg)) != 0) {
+ error("Unsafe %s \"%s\": %s", tag, av[0], errmsg);
+ restore_uid();
+ return 0;
+ }
+ /* Prepare to keep the child's stdout if requested */
+ if (pipe(p) == -1) {
+ error("%s: pipe: %s", tag, strerror(errno));
+ restore_uid();
+ return 0;
+ }
+ restore_uid();
+
+ switch ((pid = fork())) {
+ case -1: /* error */
+ error("%s: fork: %s", tag, strerror(errno));
+ close(p[0]);
+ close(p[1]);
+ return 0;
+ case 0: /* child */
+ /* Prepare a minimal environment for the child. */
+ envsize = 5;
+ child_env = xcalloc(sizeof(*child_env), envsize);
+ child_set_env(&child_env, &envsize, "PATH", _PATH_STDPATH);
+ child_set_env(&child_env, &envsize, "USER", pw->pw_name);
+ child_set_env(&child_env, &envsize, "LOGNAME", pw->pw_name);
+ child_set_env(&child_env, &envsize, "HOME", pw->pw_dir);
+ if ((cp = getenv("LANG")) != NULL)
+ child_set_env(&child_env, &envsize, "LANG", cp);
+
+ for (i = 0; i < NSIG; i++)
+ ssh_signal(i, SIG_DFL);
+
+ if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) {
+ error("%s: open %s: %s", tag, _PATH_DEVNULL,
+ strerror(errno));
+ _exit(1);
+ }
+ if (dup2(devnull, STDIN_FILENO) == -1) {
+ error("%s: dup2: %s", tag, strerror(errno));
+ _exit(1);
+ }
+
+ /* Set up stdout as requested; leave stderr in place for now. */
+ fd = -1;
+ if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0)
+ fd = p[1];
+ else if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0)
+ fd = devnull;
+ if (fd != -1 && dup2(fd, STDOUT_FILENO) == -1) {
+ error("%s: dup2: %s", tag, strerror(errno));
+ _exit(1);
+ }
+ closefrom(STDERR_FILENO + 1);
+
+ /* Don't use permanently_set_uid() here to avoid fatal() */
+ if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) == -1) {
+ error("%s: setresgid %u: %s", tag, (u_int)pw->pw_gid,
+ strerror(errno));
+ _exit(1);
+ }
+ if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) == -1) {
+ error("%s: setresuid %u: %s", tag, (u_int)pw->pw_uid,
+ strerror(errno));
+ _exit(1);
+ }
+ /* stdin is pointed to /dev/null at this point */
+ if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 &&
+ dup2(STDIN_FILENO, STDERR_FILENO) == -1) {
+ error("%s: dup2: %s", tag, strerror(errno));
+ _exit(1);
+ }
+
+ execve(av[0], av, child_env);
+ error("%s exec \"%s\": %s", tag, command, strerror(errno));
+ _exit(127);
+ default: /* parent */
+ break;
+ }
+
+ close(p[1]);
+ if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0)
+ close(p[0]);
+ else if ((f = fdopen(p[0], "r")) == NULL) {
+ error("%s: fdopen: %s", tag, strerror(errno));
+ close(p[0]);
+ /* Don't leave zombie child */
+ kill(pid, SIGTERM);
+ while (waitpid(pid, NULL, 0) == -1 && errno == EINTR)
+ ;
+ return 0;
+ }
+ /* Success */
+ debug3("%s: %s pid %ld", __func__, tag, (long)pid);
+ if (child != NULL)
+ *child = f;
+ return pid;
+}
+
+/* These functions link key/cert options to the auth framework */
+
+/* Log sshauthopt options locally and (optionally) for remote transmission */
+void
+auth_log_authopts(const char *loc, const struct sshauthopt *opts, int do_remote)
+{
+ int do_env = options.permit_user_env && opts->nenv > 0;
+ int do_permitopen = opts->npermitopen > 0 &&
+ (options.allow_tcp_forwarding & FORWARD_LOCAL) != 0;
+ int do_permitlisten = opts->npermitlisten > 0 &&
+ (options.allow_tcp_forwarding & FORWARD_REMOTE) != 0;
+ size_t i;
+ char msg[1024], buf[64];
+
+ snprintf(buf, sizeof(buf), "%d", opts->force_tun_device);
+ /* Try to keep this alphabetically sorted */
+ snprintf(msg, sizeof(msg), "key options:%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s",
+ opts->permit_agent_forwarding_flag ? " agent-forwarding" : "",
+ opts->force_command == NULL ? "" : " command",
+ do_env ? " environment" : "",
+ opts->valid_before == 0 ? "" : "expires",
+ opts->no_require_user_presence ? " no-touch-required" : "",
+ do_permitopen ? " permitopen" : "",
+ do_permitlisten ? " permitlisten" : "",
+ opts->permit_port_forwarding_flag ? " port-forwarding" : "",
+ opts->cert_principals == NULL ? "" : " principals",
+ opts->permit_pty_flag ? " pty" : "",
+ opts->require_verify ? " uv" : "",
+ opts->force_tun_device == -1 ? "" : " tun=",
+ opts->force_tun_device == -1 ? "" : buf,
+ opts->permit_user_rc ? " user-rc" : "",
+ opts->permit_x11_forwarding_flag ? " x11-forwarding" : "");
+
+ debug("%s: %s", loc, msg);
+ if (do_remote)
+ auth_debug_add("%s: %s", loc, msg);
+
+ if (options.permit_user_env) {
+ for (i = 0; i < opts->nenv; i++) {
+ debug("%s: environment: %s", loc, opts->env[i]);
+ if (do_remote) {
+ auth_debug_add("%s: environment: %s",
+ loc, opts->env[i]);
+ }
+ }
+ }
+
+ /* Go into a little more details for the local logs. */
+ if (opts->valid_before != 0) {
+ format_absolute_time(opts->valid_before, buf, sizeof(buf));
+ debug("%s: expires at %s", loc, buf);
+ }
+ if (opts->cert_principals != NULL) {
+ debug("%s: authorized principals: \"%s\"",
+ loc, opts->cert_principals);
+ }
+ if (opts->force_command != NULL)
+ debug("%s: forced command: \"%s\"", loc, opts->force_command);
+ if (do_permitopen) {
+ for (i = 0; i < opts->npermitopen; i++) {
+ debug("%s: permitted open: %s",
+ loc, opts->permitopen[i]);
+ }
+ }
+ if (do_permitlisten) {
+ for (i = 0; i < opts->npermitlisten; i++) {
+ debug("%s: permitted listen: %s",
+ loc, opts->permitlisten[i]);
+ }
+ }
+}
+
+/* Activate a new set of key/cert options; merging with what is there. */
+int
+auth_activate_options(struct ssh *ssh, struct sshauthopt *opts)
+{
+ struct sshauthopt *old = auth_opts;
+ const char *emsg = NULL;
+
+ debug("%s: setting new authentication options", __func__);
+ if ((auth_opts = sshauthopt_merge(old, opts, &emsg)) == NULL) {
+ error("Inconsistent authentication options: %s", emsg);
+ return -1;
+ }
+ return 0;
+}
+
+/* Disable forwarding, etc for the session */
+void
+auth_restrict_session(struct ssh *ssh)
+{
+ struct sshauthopt *restricted;
+
+ debug("%s: restricting session", __func__);
+
+ /* A blank sshauthopt defaults to permitting nothing */
+ restricted = sshauthopt_new();
+ restricted->permit_pty_flag = 1;
+ restricted->restricted = 1;
+
+ if (auth_activate_options(ssh, restricted) != 0)
+ fatal("%s: failed to restrict session", __func__);
+ sshauthopt_free(restricted);
+}
+
+int
+auth_authorise_keyopts(struct ssh *ssh, struct passwd *pw,
+ struct sshauthopt *opts, int allow_cert_authority, const char *loc)
+{
+ const char *remote_ip = ssh_remote_ipaddr(ssh);
+ const char *remote_host = auth_get_canonical_hostname(ssh,
+ options.use_dns);
+ time_t now = time(NULL);
+ char buf[64];
+
+ /*
+ * Check keys/principals file expiry time.
+ * NB. validity interval in certificate is handled elsewhere.
+ */
+ if (opts->valid_before && now > 0 &&
+ opts->valid_before < (uint64_t)now) {
+ format_absolute_time(opts->valid_before, buf, sizeof(buf));
+ debug("%s: entry expired at %s", loc, buf);
+ auth_debug_add("%s: entry expired at %s", loc, buf);
+ return -1;
+ }
+ /* Consistency checks */
+ if (opts->cert_principals != NULL && !opts->cert_authority) {
+ debug("%s: principals on non-CA key", loc);
+ auth_debug_add("%s: principals on non-CA key", loc);
+ /* deny access */
+ return -1;
+ }
+ /* cert-authority flag isn't valid in authorized_principals files */
+ if (!allow_cert_authority && opts->cert_authority) {
+ debug("%s: cert-authority flag invalid here", loc);
+ auth_debug_add("%s: cert-authority flag invalid here", loc);
+ /* deny access */
+ return -1;
+ }
+
+ /* Perform from= checks */
+ if (opts->required_from_host_keys != NULL) {
+ switch (match_host_and_ip(remote_host, remote_ip,
+ opts->required_from_host_keys )) {
+ case 1:
+ /* Host name matches. */
+ break;
+ case -1:
+ default:
+ debug("%s: invalid from criteria", loc);
+ auth_debug_add("%s: invalid from criteria", loc);
+ /* FALLTHROUGH */
+ case 0:
+ logit("%s: Authentication tried for %.100s with "
+ "correct key but not from a permitted "
+ "host (host=%.200s, ip=%.200s, required=%.200s).",
+ loc, pw->pw_name, remote_host, remote_ip,
+ opts->required_from_host_keys);
+ auth_debug_add("%s: Your host '%.200s' is not "
+ "permitted to use this key for login.",
+ loc, remote_host);
+ /* deny access */
+ return -1;
+ }
+ }
+ /* Check source-address restriction from certificate */
+ if (opts->required_from_host_cert != NULL) {
+ switch (addr_match_cidr_list(remote_ip,
+ opts->required_from_host_cert)) {
+ case 1:
+ /* accepted */
+ break;
+ case -1:
+ default:
+ /* invalid */
+ error("%s: Certificate source-address invalid",
+ loc);
+ /* FALLTHROUGH */
+ case 0:
+ logit("%s: Authentication tried for %.100s with valid "
+ "certificate but not from a permitted source "
+ "address (%.200s).", loc, pw->pw_name, remote_ip);
+ auth_debug_add("%s: Your address '%.200s' is not "
+ "permitted to use this certificate for login.",
+ loc, remote_ip);
+ return -1;
+ }
+ }
+ /*
+ *
+ * XXX this is spammy. We should report remotely only for keys
+ * that are successful in actual auth attempts, and not PK_OK
+ * tests.
+ */
+ auth_log_authopts(loc, opts, 1);
+
+ return 0;
+}