1 files changed, 581 insertions, 0 deletions

diff --git a/auth.c b/auth.c
new file mode 100644
index 000000000000..5d23343b9278
--- /dev/null
+++ b/auth.c
@@ -0,0 +1,581 @@
+/* $OpenBSD: auth.c,v 1.75 2006/08/03 03:34:41 deraadt 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/param.h>
+
+#include <netinet/in.h>
+
+#include <errno.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
+#ifdef HAVE_LIBGEN_H
+#include <libgen.h>
+#endif
+#include <stdarg.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "xmalloc.h"
+#include "match.h"
+#include "groupaccess.h"
+#include "log.h"
+#include "buffer.h"
+#include "servconf.h"
+#include "key.h"
+#include "hostfile.h"
+#include "auth.h"
+#include "auth-options.h"
+#include "canohost.h"
+#include "uidswap.h"
+#include "misc.h"
+#include "packet.h"
+#include "loginrec.h"
+#ifdef GSSAPI
+#include "ssh-gss.h"
+#endif
+#include "monitor_wrap.h"
+
+/* import */
+extern ServerOptions options;
+extern int use_privsep;
+extern Buffer loginmsg;
+extern struct passwd *privsep_pw;
+
+/* Debugging messages */
+Buffer auth_debug;
+int auth_debug_init;
+
+/*
+ * 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 stat st;
+	const char *hostname = NULL, *ipaddr = NULL, *passwd = NULL;
+	char *shell;
+	u_int i;
+#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 */
+#ifdef USE_SHADOW
+	if (spw != NULL)
+#if defined(HAVE_LIBIAF)  &&  !defined(BROKEN_LIBIAF)
+		passwd = get_iaf_password(pw);
+#else
+		passwd = spw->sp_pwdp;
+#endif /* HAVE_LIBIAF  && !BROKEN_LIBIAF */
+#else
+	passwd = pw->pw_passwd;
+#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
+#if defined(HAVE_LIBIAF)  &&  !defined(BROKEN_LIBIAF)
+		free(passwd);
+#endif /* HAVE_LIBIAF  && !BROKEN_LIBIAF */
+		if (locked) {
+			logit("User %.100s not allowed because account is locked",
+			    pw->pw_name);
+			return 0;
+		}
+	}
+
+	/*
+	 * Get the shell from the password data.  An empty shell field is
+	 * legal, and means /bin/sh.
+	 */
+	shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell;
+
+	/* deny if shell does not exists or is not executable */
+	if (stat(shell, &st) != 0) {
+		logit("User %.100s not allowed because shell %.100s does not exist",
+		    pw->pw_name, 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);
+		return 0;
+	}
+
+	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();
+	}
+
+	/* 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])) {
+				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]))
+				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;
+}
+
+void
+auth_log(Authctxt *authctxt, int authenticated, char *method, char *info)
+{
+	void (*authlog) (const char *fmt,...) = verbose;
+	char *authmsg;
+
+	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)
+		authlog = logit;
+
+	if (authctxt->postponed)
+		authmsg = "Postponed";
+	else
+		authmsg = authenticated ? "Accepted" : "Failed";
+
+	authlog("%s %s for %s%.100s from %.200s port %d%s",
+	    authmsg,
+	    method,
+	    authctxt->valid ? "" : "invalid user ",
+	    authctxt->user,
+	    get_remote_ipaddr(),
+	    get_remote_port(),
+	    info);
+
+#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");
+# ifdef WITH_AIXAUTHENTICATE
+	if (authenticated)
+		sys_auth_record_login(authctxt->user,
+		    get_canonical_hostname(options.use_dns), "ssh", &loginmsg);
+# endif
+#endif
+#ifdef SSH_AUDIT_EVENTS
+	if (authenticated == 0 && !authctxt->postponed)
+		audit_event(audit_classify_auth(method));
+#endif
+}
+
+/*
+ * Check whether root logins are disallowed.
+ */
+int
+auth_root_allowed(char *method)
+{
+	switch (options.permit_root_login) {
+	case PERMIT_YES:
+		return 1;
+	case PERMIT_NO_PASSWD:
+		if (strcmp(method, "password") != 0)
+			return 1;
+		break;
+	case PERMIT_FORCED_ONLY:
+		if (forced_command) {
+			logit("Root login accepted for forced command.");
+			return 1;
+		}
+		break;
+	}
+	logit("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr());
+	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.
+ */
+static char *
+expand_authorized_keys(const char *filename, struct passwd *pw)
+{
+	char *file, ret[MAXPATHLEN];
+	int i;
+
+	file = percent_expand(filename, "h", pw->pw_dir,
+	    "u", pw->pw_name, (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");
+	xfree(file);
+	return (xstrdup(ret));
+}
+
+char *
+authorized_keys_file(struct passwd *pw)
+{
+	return expand_authorized_keys(options.authorized_keys_file, pw);
+}
+
+char *
+authorized_keys_file2(struct passwd *pw)
+{
+	return expand_authorized_keys(options.authorized_keys_file2, pw);
+}
+
+/* return ok if key exists in sysfile or userfile */
+HostStatus
+check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host,
+    const char *sysfile, const char *userfile)
+{
+	Key *found;
+	char *user_hostfile;
+	struct stat st;
+	HostStatus host_status;
+
+	/* Check if we know the host and its host key. */
+	found = key_new(key->type);
+	host_status = check_host_in_hostfile(sysfile, host, key, found, NULL);
+
+	if (host_status != HOST_OK && 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);
+		} else {
+			temporarily_use_uid(pw);
+			host_status = check_host_in_hostfile(user_hostfile,
+			    host, key, found, NULL);
+			restore_uid();
+		}
+		xfree(user_hostfile);
+	}
+	key_free(found);
+
+	debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ?
+	    "ok" : "not found", host);
+	return host_status;
+}
+
+
+/*
+ * Check a given file 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 an open file descriptor, the file name, a uid and and
+ * error buffer plus max size as arguments.
+ *
+ * Returns 0 on success and -1 on failure
+ */
+int
+secure_filename(FILE *f, const char *file, struct passwd *pw,
+    char *err, size_t errlen)
+{
+	uid_t uid = pw->pw_uid;
+	char buf[MAXPATHLEN], homedir[MAXPATHLEN];
+	char *cp;
+	int comparehome = 0;
+	struct stat st;
+
+	if (realpath(file, buf) == NULL) {
+		snprintf(err, errlen, "realpath %s failed: %s", file,
+		    strerror(errno));
+		return -1;
+	}
+	if (realpath(pw->pw_dir, homedir) != NULL)
+		comparehome = 1;
+
+	/* check the open file to avoid races */
+	if (fstat(fileno(f), &st) < 0 ||
+	    (st.st_uid != 0 && st.st_uid != uid) ||
+	    (st.st_mode & 022) != 0) {
+		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));
+
+		debug3("secure_filename: checking '%s'", buf);
+		if (stat(buf, &st) < 0 ||
+		    (st.st_uid != 0 && st.st_uid != uid) ||
+		    (st.st_mode & 022) != 0) {
+			snprintf(err, errlen,
+			    "bad ownership or modes for directory %s", buf);
+			return -1;
+		}
+
+		/* If are passed the homedir then we can stop */
+		if (comparehome && strcmp(homedir, buf) == 0) {
+			debug3("secure_filename: terminating check at '%s'",
+			    buf);
+			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;
+}
+
+struct passwd *
+getpwnamallow(const char *user)
+{
+#ifdef HAVE_LOGIN_CAP
+	extern login_cap_t *lc;
+#ifdef BSD_AUTH
+	auth_session_t *as;
+#endif
+#endif
+	struct passwd *pw;
+
+	parse_server_match_config(&options, user,
+	    get_canonical_hostname(options.use_dns), get_remote_ipaddr());
+
+	pw = getpwnam(user);
+	if (pw == NULL) {
+		logit("Invalid user %.100s from %.100s",
+		    user, get_remote_ipaddr());
+#ifdef CUSTOM_FAILED_LOGIN
+		record_failed_login(user,
+		    get_canonical_hostname(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);
+}
+
+void
+auth_debug_add(const char *fmt,...)
+{
+	char buf[1024];
+	va_list args;
+
+	if (!auth_debug_init)
+		return;
+
+	va_start(args, fmt);
+	vsnprintf(buf, sizeof(buf), fmt, args);
+	va_end(args);
+	buffer_put_cstring(&auth_debug, buf);
+}
+
+void
+auth_debug_send(void)
+{
+	char *msg;
+
+	if (!auth_debug_init)
+		return;
+	while (buffer_len(&auth_debug)) {
+		msg = buffer_get_string(&auth_debug, NULL);
+		packet_send_debug("%s", msg);
+		xfree(msg);
+	}
+}
+
+void
+auth_debug_reset(void)
+{
+	if (auth_debug_init)
+		buffer_clear(&auth_debug);
+	else {
+		buffer_init(&auth_debug);
+		auth_debug_init = 1;
+	}
+}
+
+struct passwd *
+fakepw(void)
+{
+	static struct passwd fake;
+
+	memset(&fake, 0, sizeof(fake));
+	fake.pw_name = "NOUSER";
+	fake.pw_passwd =
+	    "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK";
+	fake.pw_gecos = "NOUSER";
+	fake.pw_uid = privsep_pw->pw_uid;
+	fake.pw_gid = privsep_pw->pw_gid;
+#ifdef HAVE_PW_CLASS_IN_PASSWD
+	fake.pw_class = "";
+#endif
+	fake.pw_dir = "/nonexist";
+	fake.pw_shell = "/nonexist";
+
+	return (&fake);
+}