Adding upstream version 1:7.9p1.upstream/1%7.9p1upstream

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

1 files changed, 1202 insertions, 0 deletions

diff --git a/auth.c b/auth.c
new file mode 100644
index 0000000..3ca3762
--- /dev/null
+++ b/auth.c
@@ -0,0 +1,1202 @@
+/* $OpenBSD: auth.c,v 1.133 2018/09/12 01:19:12 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 <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 "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 "authfile.h"
+#include "ssherr.h"
+#include "compat.h"
+#include "channels.h"
+
+/* import */
+extern ServerOptions options;
+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 passwd * pw)
+{
+	struct ssh *ssh = active_state; /* XXX */
+	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) != 0) {
+			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(Authctxt *authctxt, int authenticated, int partial,
+    const char *method, const char *submethod)
+{
+	struct ssh *ssh = active_state; /* XXX */
+	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(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(audit_classify_auth(method));
+#endif
+}
+
+
+void
+auth_maxtries_exceeded(Authctxt *authctxt)
+{
+	struct ssh *ssh = active_state; /* XXX */
+
+	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));
+	packet_disconnect("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 (*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",
+		    found->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) < 0) {
+		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(const char *user)
+{
+	struct ssh *ssh = active_state; /* XXX */
+#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 = get_connection_info(1, options.use_dns);
+
+	ci->user = user;
+	parse_server_match_config(&options, 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
+#ifdef HAVE_CYGWIN
+	/*
+	 * Windows usernames are case-insensitive.  To avoid later problems
+	 * when trying to match the username, the user is only allowed to
+	 * login if the username is given in the same case as stored in the
+	 * user database.
+	 */
+	if (pw != NULL && strcmp(user, pw->pw_name) != 0) {
+		logit("Login name %.100s does not match stored username %.100s",
+		    user, pw->pw_name);
+		pw = NULL;
+	}
+#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(user,
+		    auth_get_canonical_hostname(ssh, options.use_dns), "ssh");
+#endif
+#ifdef SSH_AUDIT_EVENTS
+		audit_event(SSH_INVALID_USER);
+#endif /* SSH_AUDIT_EVENTS */
+		return (NULL);
+	}
+	if (!allowed_user(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(void)
+{
+	struct ssh *ssh = active_state;		/* XXX */
+	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) < 0) {
+		debug("getpeername failed: %.100s", strerror(errno));
+		return strdup(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 strdup(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 strdup(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 strdup(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 strdup(ntop);
+	}
+	return strdup(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 (*av[0] != '/') {
+		error("%s path is not absolute", tag);
+		return 0;
+	}
+	temporarily_use_uid(pw);
+	if (stat(av[0], &st) < 0) {
+		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) != 0) {
+		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++)
+			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) != 0) {
+			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) != 0) {
+			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",
+	    opts->permit_agent_forwarding_flag ? " agent-forwarding" : "",
+	    opts->force_command == NULL ? "" : " command",
+	    do_env ?  " environment" : "",
+	    opts->valid_before == 0 ? "" : "expires",
+	    do_permitopen ?  " permitopen" : "",
+	    do_permitlisten ?  " permitlisten" : "",
+	    opts->permit_port_forwarding_flag ? " port-forwarding" : "",
+	    opts->cert_principals == NULL ? "" : " principals",
+	    opts->permit_pty_flag ? " pty" : "",
+	    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;
+}