Merge upstream-master into master

Commit ecb2c02d994b3e21994f31a70ff911667c262f1f upstream

This nearly (but not quite) corresponds to V_8_3_P1; subsequent
cherry-picks will correct this.

Bug: 162492243
Change-Id: I3c079d86435b7c25aefff4538dc89a3002b1e25b

1 files changed, 613 insertions, 206 deletions

diff --git a/auth.c b/auth.c
index 0fefead0..7aabc8e8 100644
--- a/auth.c
+++ b/auth.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: auth.c,v 1.110 2015/02/25 17:29:38 djm Exp $ */
+/* $OpenBSD: auth.c,v 1.146 2020/01/31 22:42:45 djm Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  *
@@ -27,9 +27,12 @@
 
 #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
@@ -42,23 +45,22 @@
 #ifdef USE_SHADOW
 #include <shadow.h>
 #endif
-#ifdef HAVE_LIBGEN_H
-#include <libgen.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 "buffer.h"
+#include "sshbuf.h"
 #include "misc.h"
 #include "servconf.h"
-#include "key.h"
+#include "sshkey.h"
 #include "hostfile.h"
 #include "auth.h"
 #include "auth-options.h"
@@ -71,19 +73,20 @@
 #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 struct include_list includes;
 extern int use_privsep;
-extern Buffer loginmsg;
+extern struct sshbuf *loginmsg;
 extern struct passwd *privsep_pw;
+extern struct sshauthopt *auth_opts;
 
 /* Debugging messages */
-Buffer auth_debug;
-int auth_debug_init;
+static struct sshbuf *auth_debug;
 
 /*
  * Check if the user is allowed to log in via ssh. If user is listed
@@ -95,11 +98,12 @@ int auth_debug_init;
  * Otherwise true is returned.
  */
 int
-allowed_user(struct passwd * pw)
+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
@@ -164,7 +168,7 @@ allowed_user(struct passwd * pw)
 		char *shell = xstrdup((pw->pw_shell[0] == '\0') ?
 		    _PATH_BSHELL : pw->pw_shell); /* empty = /bin/sh */
 
-		if (stat(shell, &st) != 0) {
+		if (stat(shell, &st) == -1) {
 			logit("User %.100s not allowed because shell %.100s "
 			    "does not exist", pw->pw_name, shell);
 			free(shell);
@@ -182,27 +186,37 @@ allowed_user(struct passwd * pw)
 
 	if (options.num_deny_users > 0 || options.num_allow_users > 0 ||
 	    options.num_deny_groups > 0 || options.num_allow_groups > 0) {
-		hostname = get_canonical_hostname(options.use_dns);
-		ipaddr = get_remote_ipaddr();
+		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++)
-			if (match_user(pw->pw_name, hostname, ipaddr,
-			    options.deny_users[i])) {
+		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++)
-			if (match_user(pw->pw_name, hostname, ipaddr,
-			    options.allow_users[i]))
+		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 "
@@ -245,7 +259,7 @@ allowed_user(struct passwd * pw)
 	}
 
 #ifdef CUSTOM_SYS_AUTH_ALLOWED_USER
-	if (!sys_auth_allowed_user(pw, &loginmsg))
+	if (!sys_auth_allowed_user(pw, loginmsg))
 		return 0;
 #endif
 
@@ -253,29 +267,55 @@ allowed_user(struct passwd * pw)
 	return 1;
 }
 
-void
-auth_info(Authctxt *authctxt, const char *fmt, ...)
+/*
+ * 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)
 {
-	va_list ap;
-        int i;
-
-	free(authctxt->info);
-	authctxt->info = NULL;
+	const struct sshkey *key = authctxt->auth_method_key;
+	const char *methinfo = authctxt->auth_method_info;
+	char *fp, *cafp, *ret = NULL;
 
-	va_start(ap, fmt);
-	i = vasprintf(&authctxt->info, fmt, ap);
-	va_end(ap);
+	if (key == NULL)
+		return NULL;
 
-	if (i < 0 || authctxt->info == NULL)
-		fatal("vasprintf failed");
+	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,
+auth_log(struct ssh *ssh, int authenticated, int partial,
     const char *method, const char *submethod)
 {
-	void (*authlog) (const char *fmt,...) = verbose;
-	char *authmsg;
+	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;
@@ -285,7 +325,7 @@ auth_log(Authctxt *authctxt, int authenticated, int partial,
 	    !authctxt->valid ||
 	    authctxt->failures >= options.max_authtries / 2 ||
 	    strcmp(method, "password") == 0)
-		authlog = logit;
+		level = SYSLOG_LEVEL_INFO;
 
 	if (authctxt->postponed)
 		authmsg = "Postponed";
@@ -294,51 +334,57 @@ auth_log(Authctxt *authctxt, int authenticated, int partial,
 	else
 		authmsg = authenticated ? "Accepted" : "Failed";
 
-	authlog("%s %s%s%s for %s%.100s from %.200s port %d %s%s%s",
+	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,
-	    get_remote_ipaddr(),
-	    get_remote_port(),
-	    compat20 ? "ssh2" : "ssh1",
-	    authctxt->info != NULL ? ": " : "",
-	    authctxt->info != NULL ? authctxt->info : "");
-	free(authctxt->info);
-	authctxt->info = NULL;
+	    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,
-		    get_canonical_hostname(options.use_dns), "ssh");
+		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,
-		    get_canonical_hostname(options.use_dns), "ssh", &loginmsg);
+		    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));
+		audit_event(ssh, audit_classify_auth(method));
 #endif
 }
 
 
 void
-auth_maxtries_exceeded(Authctxt *authctxt)
+auth_maxtries_exceeded(struct ssh *ssh)
 {
+	Authctxt *authctxt = (Authctxt *)ssh->authctxt;
+
 	error("maximum authentication attempts exceeded for "
-	    "%s%.100s from %.200s port %d %s",
+	    "%s%.100s from %.200s port %d ssh2",
 	    authctxt->valid ? "" : "invalid user ",
 	    authctxt->user,
-	    get_remote_ipaddr(),
-	    get_remote_port(),
-	    compat20 ? "ssh2" : "ssh1");
-	packet_disconnect("Too many authentication failures");
+	    ssh_remote_ipaddr(ssh),
+	    ssh_remote_port(ssh));
+	ssh_packet_disconnect(ssh, "Too many authentication failures");
 	/* NOTREACHED */
 }
 
@@ -346,23 +392,26 @@ auth_maxtries_exceeded(Authctxt *authctxt)
  * Check whether root logins are disallowed.
  */
 int
-auth_root_allowed(const char *method)
+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, "password") != 0)
+		if (strcmp(method, "publickey") == 0 ||
+		    strcmp(method, "hostbased") == 0 ||
+		    strcmp(method, "gssapi-with-mic") == 0)
 			return 1;
 		break;
 	case PERMIT_FORCED_ONLY:
-		if (forced_command) {
+		if (auth_opts->force_command != NULL) {
 			logit("Root login accepted for forced command.");
 			return 1;
 		}
 		break;
 	}
-	logit("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr());
+	logit("ROOT LOGIN REFUSED FROM %.200s port %d",
+	    ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
 	return 0;
 }
 
@@ -377,17 +426,19 @@ auth_root_allowed(const char *method)
 char *
 expand_authorized_keys(const char *filename, struct passwd *pw)
 {
-	char *file, ret[PATH_MAX];
+	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, (char *)NULL);
+	    "u", pw->pw_name, "U", uidstr, (char *)NULL);
 
 	/*
 	 * Ensure that filename starts anchored. If not, be backward
 	 * compatible and prepend the '%h/'
 	 */
-	if (*file == '/')
+	if (path_absolute(file))
 		return (file);
 
 	i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file);
@@ -400,15 +451,14 @@ expand_authorized_keys(const char *filename, struct passwd *pw)
 char *
 authorized_principals_file(struct passwd *pw)
 {
-	if (options.authorized_principals_file == NULL ||
-	    strcasecmp(options.authorized_principals_file, "none") == 0)
+	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, Key *key, const char *host,
+check_key_in_hostfiles(struct passwd *pw, struct sshkey *key, const char *host,
     const char *sysfile, const char *userfile)
 {
 	char *user_hostfile;
@@ -440,7 +490,7 @@ check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host,
 	host_status = check_key_in_hostkeys(hostkeys, key, &found);
 	if (host_status == HOST_REVOKED)
 		error("WARNING: revoked key for %s attempted authentication",
-		    found->host);
+		    host);
 	else if (host_status == HOST_OK)
 		debug("%s: key for %s found at %s:%ld", __func__,
 		    found->host, found->file, found->line);
@@ -452,107 +502,6 @@ check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host,
 	return host_status;
 }
 
-/*
- * Check a given path for security. This is defined as all components
- * of the path to the file must be owned by either the owner of
- * of the file or root and no directories must be group or world writable.
- *
- * XXX Should any specific check be done for sym links ?
- *
- * Takes a file name, its stat information (preferably from fstat() to
- * avoid races), the uid of the expected owner, their home directory and an
- * error buffer plus max size as arguments.
- *
- * Returns 0 on success and -1 on failure
- */
-int
-auth_secure_path(const char *name, struct stat *stp, const char *pw_dir,
-    uid_t uid, char *err, size_t errlen)
-{
-	char buf[PATH_MAX], homedir[PATH_MAX];
-	char *cp;
-	int comparehome = 0;
-	struct stat st;
-
-	if (realpath(name, buf) == NULL) {
-		snprintf(err, errlen, "realpath %s failed: %s", name,
-		    strerror(errno));
-		return -1;
-	}
-	if (pw_dir != NULL && realpath(pw_dir, homedir) != NULL)
-		comparehome = 1;
-
-	if (!S_ISREG(stp->st_mode)) {
-		snprintf(err, errlen, "%s is not a regular file", buf);
-		return -1;
-	}
-	if ((!platform_sys_dir_uid(stp->st_uid) && stp->st_uid != uid) ||
-	    (stp->st_mode & 022) != 0) {
-#if defined(ANDROID)
-		/* needed to allow root login on Android. */
-		if (getuid() != 0)
-#endif
-		{
-		snprintf(err, errlen, "bad ownership or modes for file %s",
-		    buf);
-		return -1;
-		}
-	}
-
-	/* for each component of the canonical path, walking upwards */
-	for (;;) {
-		if ((cp = dirname(buf)) == NULL) {
-			snprintf(err, errlen, "dirname() failed");
-			return -1;
-		}
-		strlcpy(buf, cp, sizeof(buf));
-
-#if !defined(ANDROID)
-		/* /data is owned by system user, which causes this check to fail */
-		if (stat(buf, &st) < 0 ||
-		    (!platform_sys_dir_uid(st.st_uid) && st.st_uid != uid) ||
-		    (st.st_mode & 022) != 0) {
-			snprintf(err, errlen,
-			    "bad ownership or modes for directory %s", buf);
-			return -1;
-		}
-#endif
-
-		/* If are past the homedir then we can stop */
-		if (comparehome && strcmp(homedir, buf) == 0)
-			break;
-
-		/*
-		 * dirname should always complete with a "/" path,
-		 * but we can be paranoid and check for "." too
-		 */
-		if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0))
-			break;
-	}
-	return 0;
-}
-
-/*
- * Version of secure_path() that accepts an open file descriptor to
- * avoid races.
- *
- * Returns 0 on success and -1 on failure
- */
-static int
-secure_filename(FILE *f, const char *file, struct passwd *pw,
-    char *err, size_t errlen)
-{
-	struct stat st;
-
-	/* check the open file to avoid races */
-	if (fstat(fileno(f), &st) < 0) {
-		snprintf(err, errlen, "cannot stat file %s: %s",
-		    file, strerror(errno));
-		return -1;
-	}
-	return auth_secure_path(file, &st, pw->pw_dir, pw->pw_uid, err, errlen);
-}
-
 static FILE *
 auth_openfile(const char *file, struct passwd *pw, int strict_modes,
     int log_missing, char *file_type)
@@ -569,7 +518,7 @@ auth_openfile(const char *file, struct passwd *pw, int strict_modes,
 		return NULL;
 	}
 
-	if (fstat(fd, &st) < 0) {
+	if (fstat(fd, &st) == -1) {
 		close(fd);
 		return NULL;
 	}
@@ -585,7 +534,7 @@ auth_openfile(const char *file, struct passwd *pw, int strict_modes,
 		return NULL;
 	}
 	if (strict_modes &&
-	    secure_filename(f, file, pw, line, sizeof(line)) != 0) {
+	    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);
@@ -610,7 +559,7 @@ auth_openprincipals(const char *file, struct passwd *pw, int strict_modes)
 }
 
 struct passwd *
-getpwnamallow(const char *user)
+getpwnamallow(struct ssh *ssh, const char *user)
 {
 #ifdef HAVE_LOGIN_CAP
 	extern login_cap_t *lc;
@@ -619,16 +568,19 @@ getpwnamallow(const char *user)
 #endif
 #endif
 	struct passwd *pw;
-	struct connection_info *ci = get_connection_info(1, options.use_dns);
+	struct connection_info *ci;
 
+	ci = get_connection_info(ssh, 1, options.use_dns);
 	ci->user = user;
-	parse_server_match_config(&options, ci);
+	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
 
-#ifdef ANDROID_GCE
+#if defined(ANDROID)
 	// Android has a fixed set of users. Any incoming user that we can't
 	// identify should be authenticated as the shell user.
 	if (strcmp(user, "root") && strcmp(user, "shell")) {
@@ -641,32 +593,19 @@ getpwnamallow(const char *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",
-		    user, get_remote_ipaddr());
+		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,
-		    get_canonical_hostname(options.use_dns), "ssh");
+		record_failed_login(ssh, user,
+		    auth_get_canonical_hostname(ssh, options.use_dns), "ssh");
 #endif
 #ifdef SSH_AUDIT_EVENTS
-		audit_event(SSH_INVALID_USER);
+		audit_event(ssh, SSH_INVALID_USER);
 #endif /* SSH_AUDIT_EVENTS */
 		return (NULL);
 	}
-	if (!allowed_user(pw))
+	if (!allowed_user(ssh, pw))
 		return (NULL);
 #ifdef HAVE_LOGIN_CAP
 	if ((lc = login_getclass(pw->pw_class)) == NULL) {
@@ -690,7 +629,7 @@ getpwnamallow(const char *user)
 
 /* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */
 int
-auth_key_is_revoked(Key *key)
+auth_key_is_revoked(struct sshkey *key)
 {
 	char *fp = NULL;
 	int r;
@@ -732,26 +671,31 @@ auth_debug_add(const char *fmt,...)
 {
 	char buf[1024];
 	va_list args;
+	int r;
 
-	if (!auth_debug_init)
+	if (auth_debug == NULL)
 		return;
 
 	va_start(args, fmt);
 	vsnprintf(buf, sizeof(buf), fmt, args);
 	va_end(args);
-	buffer_put_cstring(&auth_debug, buf);
+	if ((r = sshbuf_put_cstring(auth_debug, buf)) != 0)
+		fatal("%s: sshbuf_put_cstring: %s", __func__, ssh_err(r));
 }
 
 void
-auth_debug_send(void)
+auth_debug_send(struct ssh *ssh)
 {
 	char *msg;
+	int r;
 
-	if (!auth_debug_init)
+	if (auth_debug == NULL)
 		return;
-	while (buffer_len(&auth_debug)) {
-		msg = buffer_get_string(&auth_debug, NULL);
-		packet_send_debug("%s", msg);
+	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);
 	}
 }
@@ -759,12 +703,10 @@ auth_debug_send(void)
 void
 auth_debug_reset(void)
 {
-	if (auth_debug_init)
-		buffer_clear(&auth_debug);
-	else {
-		buffer_init(&auth_debug);
-		auth_debug_init = 1;
-	}
+	if (auth_debug != NULL)
+		sshbuf_reset(auth_debug);
+	else if ((auth_debug = sshbuf_new()) == NULL)
+		fatal("%s: sshbuf_new failed", __func__);
 }
 
 struct passwd *
@@ -789,3 +731,468 @@ fakepw(void)
 
 	return (&fake);
 }
+
+/*
+ * Returns the remote DNS hostname as a string. The returned string must not
+ * be freed. NB. this will usually trigger a DNS query the first time it is
+ * called.
+ * This function does additional checks on the hostname to mitigate some
+ * attacks on 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",
+	    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" : "",
+	    opts->no_require_user_presence ? " no-touch-required" : "");
+
+	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;
+}