Head

GCC Code Coverage Report

Directory:	./		Exec	Total	Coverage
File:	usr.bin/ssh/sshd/../auth.c	Lines:	0	317	0.0 %
Date:	2017-11-07	Branches:	0	181	0.0 %


/* $OpenBSD: auth.c,v 1.124 2017/09/12 06:32:07 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 <sys/types.h>
#include <sys/stat.h>
#include <sys/socket.h>

#include <errno.h>
#include <fcntl.h>
#include <login_cap.h>
#include <paths.h>
#include <pwd.h>
#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 "buffer.h"
#include "misc.h"
#include "servconf.h"
#include "key.h"
#include "hostfile.h"
#include "auth.h"
#include "auth-options.h"
#include "canohost.h"
#include "uidswap.h"
#include "packet.h"
#ifdef GSSAPI
#include "ssh-gss.h"
#endif
#include "authfile.h"
#include "monitor_wrap.h"
#include "authfile.h"
#include "ssherr.h"
#include "compat.h"

/* import */
extern ServerOptions options;
extern int use_privsep;

/* 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 ssh *ssh = active_state; /* XXX */
	struct stat st;
	const char *hostname = NULL, *ipaddr = NULL;
	int r;
	u_int i;

	/* Shouldn't be called if pw is NULL, but better safe than sorry... */
	if (!pw || !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();
	}
	/* 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, *ret = NULL;

	if (key == NULL)
		return NULL;

	if (key_is_cert(key)) {
		fp = sshkey_fingerprint(key->cert->signature_key,
		    options.fingerprint_hash, SSH_FP_DEFAULT);
		xasprintf(&ret, "%s ID %s (serial %llu) CA %s %s%s%s",
		    sshkey_type(key), key->cert->key_id,
		    (unsigned long long)key->cert->serial,
		    sshkey_type(key->cert->signature_key),
		    fp == NULL ? "(null)" : fp,
		    methinfo == NULL ? "" : ", ",
		    methinfo == NULL ? "" : methinfo);
		free(fp);
	} 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 */
	void (*authlog) (const char *fmt,...) = 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)
		authlog = logit;

	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);
	}

	authlog("%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);
}

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(const char *method)
{
	struct ssh *ssh = active_state; /* XXX */

	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 (forced_command) {
			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, ret[PATH_MAX];
	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");
	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 */
	extern login_cap_t *lc;
	auth_session_t *as;
	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);

	pw = getpwnam(user);
	if (pw == NULL) {
		logit("Invalid user %.100s from %.100s port %d",
		    user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
		return (NULL);
	}
	if (!allowed_user(pw))
		return (NULL);
	if ((lc = login_getclass(pw->pw_class)) == NULL) {
		debug("unable to get login class: %s", user);
		return (NULL);
	}
	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);
	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;

	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);
		free(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 = (uid_t)-1;
	fake.pw_gid = (gid_t)-1;
	fake.pw_class = "";
	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);
	}

	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;
	}
}


Generated by: GCOVR (Version 3.3)

Line	Branch	Exec	Source
1			/* $OpenBSD: auth.c,v 1.124 2017/09/12 06:32:07 djm Exp $ */
2			/*
3			* Copyright (c) 2000 Markus Friedl. All rights reserved.
4			*
5			* Redistribution and use in source and binary forms, with or without
6			* modification, are permitted provided that the following conditions
7			* are met:
8			* 1. Redistributions of source code must retain the above copyright
9			* notice, this list of conditions and the following disclaimer.
10			* 2. Redistributions in binary form must reproduce the above copyright
11			* notice, this list of conditions and the following disclaimer in the
12			* documentation and/or other materials provided with the distribution.
13			*
14			* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15			* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16			* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17			* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18			* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19			* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20			* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21			* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22			* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23			* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24			*/
25
26			#include <sys/types.h>
27			#include <sys/stat.h>
28			#include <sys/socket.h>
29
30			#include <errno.h>
31			#include <fcntl.h>
32			#include <login_cap.h>
33			#include <paths.h>
34			#include <pwd.h>
35			#include <stdarg.h>
36			#include <stdio.h>
37			#include <string.h>
38			#include <unistd.h>
39			#include <limits.h>
40			#include <netdb.h>
41
42			#include "xmalloc.h"
43			#include "match.h"
44			#include "groupaccess.h"
45			#include "log.h"
46			#include "buffer.h"
47			#include "misc.h"
48			#include "servconf.h"
49			#include "key.h"
50			#include "hostfile.h"
51			#include "auth.h"
52			#include "auth-options.h"
53			#include "canohost.h"
54			#include "uidswap.h"
55			#include "packet.h"
56			#ifdef GSSAPI
57			#include "ssh-gss.h"
58			#endif
59			#include "authfile.h"
60			#include "monitor_wrap.h"
61			#include "authfile.h"
62			#include "ssherr.h"
63			#include "compat.h"
64
65			/* import */
66			extern ServerOptions options;
67			extern int use_privsep;
68
69			/* Debugging messages */
70			Buffer auth_debug;
71			int auth_debug_init;
72
73			/*
74			* Check if the user is allowed to log in via ssh. If user is listed
75			* in DenyUsers or one of user's groups is listed in DenyGroups, false
76			* will be returned. If AllowUsers isn't empty and user isn't listed
77			* there, or if AllowGroups isn't empty and one of user's groups isn't
78			* listed there, false will be returned.
79			* If the user's shell is not executable, false will be returned.
80			* Otherwise true is returned.
81			*/
82			int
83			allowed_user(struct passwd * pw)
84			{
85			struct ssh ssh = active_state; / XXX */
86			struct stat st;
87			const char hostname = NULL, ipaddr = NULL;
88			int r;
89			u_int i;
90
91			/* Shouldn't be called if pw is NULL, but better safe than sorry... */
92			if (!pw \|\| !pw->pw_name)
93			return 0;
94
95			/*
96			* Deny if shell does not exist or is not executable unless we
97			* are chrooting.
98			*/
99			if (options.chroot_directory == NULL \|\|
100			strcasecmp(options.chroot_directory, "none") == 0) {
101			char *shell = xstrdup((pw->pw_shell[0] == '\0') ?
102			_PATH_BSHELL : pw->pw_shell); /* empty = /bin/sh */
103
104			if (stat(shell, &st) != 0) {
105			logit("User %.100s not allowed because shell %.100s "
106			"does not exist", pw->pw_name, shell);
107			free(shell);
108			return 0;
109			}
110			if (S_ISREG(st.st_mode) == 0 \|\|
111			(st.st_mode & (S_IXOTH\|S_IXUSR\|S_IXGRP)) == 0) {
112			logit("User %.100s not allowed because shell %.100s "
113			"is not executable", pw->pw_name, shell);
114			free(shell);
115			return 0;
116			}
117			free(shell);
118			}
119
120			if (options.num_deny_users > 0 \|\| options.num_allow_users > 0 \|\|
121			options.num_deny_groups > 0 \|\| options.num_allow_groups > 0) {
122			hostname = auth_get_canonical_hostname(ssh, options.use_dns);
123			ipaddr = ssh_remote_ipaddr(ssh);
124			}
125
126			/* Return false if user is listed in DenyUsers */
127			if (options.num_deny_users > 0) {
128			for (i = 0; i < options.num_deny_users; i++) {
129			r = match_user(pw->pw_name, hostname, ipaddr,
130			options.deny_users[i]);
131			if (r < 0) {
132			fatal("Invalid DenyUsers pattern \"%.100s\"",
133			options.deny_users[i]);
134			} else if (r != 0) {
135			logit("User %.100s from %.100s not allowed "
136			"because listed in DenyUsers",
137			pw->pw_name, hostname);
138			return 0;
139			}
140			}
141			}
142			/* Return false if AllowUsers isn't empty and user isn't listed there */
143			if (options.num_allow_users > 0) {
144			for (i = 0; i < options.num_allow_users; i++) {
145			r = match_user(pw->pw_name, hostname, ipaddr,
146			options.allow_users[i]);
147			if (r < 0) {
148			fatal("Invalid AllowUsers pattern \"%.100s\"",
149			options.allow_users[i]);
150			} else if (r == 1)
151			break;
152			}
153			/* i < options.num_allow_users iff we break for loop */
154			if (i >= options.num_allow_users) {
155			logit("User %.100s from %.100s not allowed because "
156			"not listed in AllowUsers", pw->pw_name, hostname);
157			return 0;
158			}
159			}
160			if (options.num_deny_groups > 0 \|\| options.num_allow_groups > 0) {
161			/* Get the user's group access list (primary and supplementary) */
162			if (ga_init(pw->pw_name, pw->pw_gid) == 0) {
163			logit("User %.100s from %.100s not allowed because "
164			"not in any group", pw->pw_name, hostname);
165			return 0;
166			}
167
168			/* Return false if one of user's groups is listed in DenyGroups */
169			if (options.num_deny_groups > 0)
170			if (ga_match(options.deny_groups,
171			options.num_deny_groups)) {
172			ga_free();
173			logit("User %.100s from %.100s not allowed "
174			"because a group is listed in DenyGroups",
175			pw->pw_name, hostname);
176			return 0;
177			}
178			/*
179			* Return false if AllowGroups isn't empty and one of user's groups
180			* isn't listed there
181			*/
182			if (options.num_allow_groups > 0)
183			if (!ga_match(options.allow_groups,
184			options.num_allow_groups)) {
185			ga_free();
186			logit("User %.100s from %.100s not allowed "
187			"because none of user's groups are listed "
188			"in AllowGroups", pw->pw_name, hostname);
189			return 0;
190			}
191			ga_free();
192			}
193			/* We found no reason not to let this user try to log on... */
194			return 1;
195			}
196
197			/*
198			* Formats any key left in authctxt->auth_method_key for inclusion in
199			* auth_log()'s message. Also includes authxtct->auth_method_info if present.
200			*/
201			static char *
202			format_method_key(Authctxt *authctxt)
203			{
204			const struct sshkey *key = authctxt->auth_method_key;
205			const char *methinfo = authctxt->auth_method_info;
206			char fp, ret = NULL;
207
208			if (key == NULL)
209			return NULL;
210
211			if (key_is_cert(key)) {
212			fp = sshkey_fingerprint(key->cert->signature_key,
213			options.fingerprint_hash, SSH_FP_DEFAULT);
214			xasprintf(&ret, "%s ID %s (serial %llu) CA %s %s%s%s",
215			sshkey_type(key), key->cert->key_id,
216			(unsigned long long)key->cert->serial,
217			sshkey_type(key->cert->signature_key),
218			fp == NULL ? "(null)" : fp,
219			methinfo == NULL ? "" : ", ",
220			methinfo == NULL ? "" : methinfo);
221			free(fp);
222			} else {
223			fp = sshkey_fingerprint(key, options.fingerprint_hash,
224			SSH_FP_DEFAULT);
225			xasprintf(&ret, "%s %s%s%s", sshkey_type(key),
226			fp == NULL ? "(null)" : fp,
227			methinfo == NULL ? "" : ", ",
228			methinfo == NULL ? "" : methinfo);
229			free(fp);
230			}
231			return ret;
232			}
233
234			void
235			auth_log(Authctxt *authctxt, int authenticated, int partial,
236			const char method, const char submethod)
237			{
238			struct ssh ssh = active_state; / XXX */
239			void (authlog) (const char fmt,...) = verbose;
240			const char *authmsg;
241			char *extra = NULL;
242
243			if (use_privsep && !mm_is_monitor() && !authctxt->postponed)
244			return;
245
246			/* Raise logging level */
247			if (authenticated == 1 \|\|
248			!authctxt->valid \|\|
249			authctxt->failures >= options.max_authtries / 2 \|\|
250			strcmp(method, "password") == 0)
251			authlog = logit;
252
253			if (authctxt->postponed)
254			authmsg = "Postponed";
255			else if (partial)
256			authmsg = "Partial";
257			else
258			authmsg = authenticated ? "Accepted" : "Failed";
259
260			if ((extra = format_method_key(authctxt)) == NULL) {
261			if (authctxt->auth_method_info != NULL)
262			extra = xstrdup(authctxt->auth_method_info);
263			}
264
265			authlog("%s %s%s%s for %s%.100s from %.200s port %d ssh2%s%s",
266			authmsg,
267			method,
268			submethod != NULL ? "/" : "", submethod == NULL ? "" : submethod,
269			authctxt->valid ? "" : "invalid user ",
270			authctxt->user,
271			ssh_remote_ipaddr(ssh),
272			ssh_remote_port(ssh),
273			extra != NULL ? ": " : "",
274			extra != NULL ? extra : "");
275
276			free(extra);
277			}
278
279			void
280			auth_maxtries_exceeded(Authctxt *authctxt)
281			{
282			struct ssh ssh = active_state; / XXX */
283
284			error("maximum authentication attempts exceeded for "
285			"%s%.100s from %.200s port %d ssh2",
286			authctxt->valid ? "" : "invalid user ",
287			authctxt->user,
288			ssh_remote_ipaddr(ssh),
289			ssh_remote_port(ssh));
290			packet_disconnect("Too many authentication failures");
291			/* NOTREACHED */
292			}
293
294			/*
295			* Check whether root logins are disallowed.
296			*/
297			int
298			auth_root_allowed(const char *method)
299			{
300			struct ssh ssh = active_state; / XXX */
301
302			switch (options.permit_root_login) {
303			case PERMIT_YES:
304			return 1;
305			case PERMIT_NO_PASSWD:
306			if (strcmp(method, "publickey") == 0 \|\|
307			strcmp(method, "hostbased") == 0 \|\|
308			strcmp(method, "gssapi-with-mic") == 0)
309			return 1;
310			break;
311			case PERMIT_FORCED_ONLY:
312			if (forced_command) {
313			logit("Root login accepted for forced command.");
314			return 1;
315			}
316			break;
317			}
318			logit("ROOT LOGIN REFUSED FROM %.200s port %d",
319			ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
320			return 0;
321			}
322
323
324			/*
325			* Given a template and a passwd structure, build a filename
326			* by substituting % tokenised options. Currently, %% becomes '%',
327			* %h becomes the home directory and %u the username.
328			*
329			* This returns a buffer allocated by xmalloc.
330			*/
331			char *
332			expand_authorized_keys(const char filename, struct passwd pw)
333			{
334			char *file, ret[PATH_MAX];
335			int i;
336
337			file = percent_expand(filename, "h", pw->pw_dir,
338			"u", pw->pw_name, (char *)NULL);
339
340			/*
341			* Ensure that filename starts anchored. If not, be backward
342			* compatible and prepend the '%h/'
343			*/
344			if (*file == '/')
345			return (file);
346
347			i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file);
348			if (i < 0 \|\| (size_t)i >= sizeof(ret))
349			fatal("expand_authorized_keys: path too long");
350			free(file);
351			return (xstrdup(ret));
352			}
353
354			char *
355			authorized_principals_file(struct passwd *pw)
356			{
357			if (options.authorized_principals_file == NULL)
358			return NULL;
359			return expand_authorized_keys(options.authorized_principals_file, pw);
360			}
361
362			/* return ok if key exists in sysfile or userfile */
363			HostStatus
364			check_key_in_hostfiles(struct passwd pw, struct sshkey key, const char *host,
365			const char sysfile, const char userfile)
366			{
367			char *user_hostfile;
368			struct stat st;
369			HostStatus host_status;
370			struct hostkeys *hostkeys;
371			const struct hostkey_entry *found;
372
373			hostkeys = init_hostkeys();
374			load_hostkeys(hostkeys, host, sysfile);
375			if (userfile != NULL) {
376			user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
377			if (options.strict_modes &&
378			(stat(user_hostfile, &st) == 0) &&
379			((st.st_uid != 0 && st.st_uid != pw->pw_uid) \|\|
380			(st.st_mode & 022) != 0)) {
381			logit("Authentication refused for %.100s: "
382			"bad owner or modes for %.200s",
383			pw->pw_name, user_hostfile);
384			auth_debug_add("Ignored %.200s: bad ownership or modes",
385			user_hostfile);
386			} else {
387			temporarily_use_uid(pw);
388			load_hostkeys(hostkeys, host, user_hostfile);
389			restore_uid();
390			}
391			free(user_hostfile);
392			}
393			host_status = check_key_in_hostkeys(hostkeys, key, &found);
394			if (host_status == HOST_REVOKED)
395			error("WARNING: revoked key for %s attempted authentication",
396			found->host);
397			else if (host_status == HOST_OK)
398			debug("%s: key for %s found at %s:%ld", __func__,
399			found->host, found->file, found->line);
400			else
401			debug("%s: key for host %s not found", __func__, host);
402
403			free_hostkeys(hostkeys);
404
405			return host_status;
406			}
407
408			static FILE *
409			auth_openfile(const char file, struct passwd pw, int strict_modes,
410			int log_missing, char *file_type)
411			{
412			char line[1024];
413			struct stat st;
414			int fd;
415			FILE *f;
416
417			if ((fd = open(file, O_RDONLY\|O_NONBLOCK)) == -1) {
418			if (log_missing \|\| errno != ENOENT)
419			debug("Could not open %s '%s': %s", file_type, file,
420			strerror(errno));
421			return NULL;
422			}
423
424			if (fstat(fd, &st) < 0) {
425			close(fd);
426			return NULL;
427			}
428			if (!S_ISREG(st.st_mode)) {
429			logit("User %s %s %s is not a regular file",
430			pw->pw_name, file_type, file);
431			close(fd);
432			return NULL;
433			}
434			unset_nonblock(fd);
435			if ((f = fdopen(fd, "r")) == NULL) {
436			close(fd);
437			return NULL;
438			}
439			if (strict_modes &&
440			safe_path_fd(fileno(f), file, pw, line, sizeof(line)) != 0) {
441			fclose(f);
442			logit("Authentication refused: %s", line);
443			auth_debug_add("Ignored %s: %s", file_type, line);
444			return NULL;
445			}
446
447			return f;
448			}
449
450
451			FILE *
452			auth_openkeyfile(const char file, struct passwd pw, int strict_modes)
453			{
454			return auth_openfile(file, pw, strict_modes, 1, "authorized keys");
455			}
456
457			FILE *
458			auth_openprincipals(const char file, struct passwd pw, int strict_modes)
459			{
460			return auth_openfile(file, pw, strict_modes, 0,
461			"authorized principals");
462			}
463
464			struct passwd *
465			getpwnamallow(const char *user)
466			{
467			struct ssh ssh = active_state; / XXX */
468			extern login_cap_t *lc;
469			auth_session_t *as;
470			struct passwd *pw;
471			struct connection_info *ci = get_connection_info(1, options.use_dns);
472
473			ci->user = user;
474			parse_server_match_config(&options, ci);
475			log_change_level(options.log_level);
476			process_permitopen(ssh, &options);
477
478			pw = getpwnam(user);
479			if (pw == NULL) {
480			logit("Invalid user %.100s from %.100s port %d",
481			user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
482			return (NULL);
483			}
484			if (!allowed_user(pw))
485			return (NULL);
486			if ((lc = login_getclass(pw->pw_class)) == NULL) {
487			debug("unable to get login class: %s", user);
488			return (NULL);
489			}
490			if ((as = auth_open()) == NULL \|\| auth_setpwd(as, pw) != 0 \|\|
491			auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
492			debug("Approval failure for %s", user);
493			pw = NULL;
494			}
495			if (as != NULL)
496			auth_close(as);
497			if (pw != NULL)
498			return (pwcopy(pw));
499			return (NULL);
500			}
501
502			/* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */
503			int
504			auth_key_is_revoked(struct sshkey *key)
505			{
506			char *fp = NULL;
507			int r;
508
509			if (options.revoked_keys_file == NULL)
510			return 0;
511			if ((fp = sshkey_fingerprint(key, options.fingerprint_hash,
512			SSH_FP_DEFAULT)) == NULL) {
513			r = SSH_ERR_ALLOC_FAIL;
514			error("%s: fingerprint key: %s", __func__, ssh_err(r));
515			goto out;
516			}
517
518			r = sshkey_check_revoked(key, options.revoked_keys_file);
519			switch (r) {
520			case 0:
521			break; /* not revoked */
522			case SSH_ERR_KEY_REVOKED:
523			error("Authentication key %s %s revoked by file %s",
524			sshkey_type(key), fp, options.revoked_keys_file);
525			goto out;
526			default:
527			error("Error checking authentication key %s %s in "
528			"revoked keys file %s: %s", sshkey_type(key), fp,
529			options.revoked_keys_file, ssh_err(r));
530			goto out;
531			}
532
533			/* Success */
534			r = 0;
535
536			out:
537			free(fp);
538			return r == 0 ? 0 : 1;
539			}
540
541			void
542			auth_debug_add(const char *fmt,...)
543			{
544			char buf[1024];
545			va_list args;
546
547			if (!auth_debug_init)
548			return;
549
550			va_start(args, fmt);
551			vsnprintf(buf, sizeof(buf), fmt, args);
552			va_end(args);
553			buffer_put_cstring(&auth_debug, buf);
554			}
555
556			void
557			auth_debug_send(void)
558			{
559			char *msg;
560
561			if (!auth_debug_init)
562			return;
563			while (buffer_len(&auth_debug)) {
564			msg = buffer_get_string(&auth_debug, NULL);
565			packet_send_debug("%s", msg);
566			free(msg);
567			}
568			}
569
570			void
571			auth_debug_reset(void)
572			{
573			if (auth_debug_init)
574			buffer_clear(&auth_debug);
575			else {
576			buffer_init(&auth_debug);
577			auth_debug_init = 1;
578			}
579			}
580
581			struct passwd *
582			fakepw(void)
583			{
584			static struct passwd fake;
585
586			memset(&fake, 0, sizeof(fake));
587			fake.pw_name = "NOUSER";
588			fake.pw_passwd =
589			"$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK";
590			fake.pw_gecos = "NOUSER";
591			fake.pw_uid = (uid_t)-1;
592			fake.pw_gid = (gid_t)-1;
593			fake.pw_class = "";
594			fake.pw_dir = "/nonexist";
595			fake.pw_shell = "/nonexist";
596
597			return (&fake);
598			}
599
600			/*
601			* Returns the remote DNS hostname as a string. The returned string must not
602			* be freed. NB. this will usually trigger a DNS query the first time it is
603			* called.
604			* This function does additional checks on the hostname to mitigate some
605			* attacks on legacy rhosts-style authentication.
606			* XXX is RhostsRSAAuthentication vulnerable to these?
607			* XXX Can we remove these checks? (or if not, remove RhostsRSAAuthentication?)
608			*/
609
610			static char *
611			remote_hostname(struct ssh *ssh)
612			{
613			struct sockaddr_storage from;
614			socklen_t fromlen;
615			struct addrinfo hints, ai, aitop;
616			char name[NI_MAXHOST], ntop2[NI_MAXHOST];
617			const char *ntop = ssh_remote_ipaddr(ssh);
618
619			/* Get IP address of client. */
620			fromlen = sizeof(from);
621			memset(&from, 0, sizeof(from));
622			if (getpeername(ssh_packet_get_connection_in(ssh),
623			(struct sockaddr *)&from, &fromlen) < 0) {
624			debug("getpeername failed: %.100s", strerror(errno));
625			return strdup(ntop);
626			}
627
628			debug3("Trying to reverse map address %.100s.", ntop);
629			/* Map the IP address to a host name. */
630			if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
631			NULL, 0, NI_NAMEREQD) != 0) {
632			/* Host name not found. Use ip address. */
633			return strdup(ntop);
634			}
635
636			/*
637			* if reverse lookup result looks like a numeric hostname,
638			* someone is trying to trick us by PTR record like following:
639			* 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5
640			*/
641			memset(&hints, 0, sizeof(hints));
642			hints.ai_socktype = SOCK_DGRAM; /dummy/
643			hints.ai_flags = AI_NUMERICHOST;
644			if (getaddrinfo(name, NULL, &hints, &ai) == 0) {
645			logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
646			name, ntop);
647			freeaddrinfo(ai);
648			return strdup(ntop);
649			}
650
651			/* Names are stored in lowercase. */
652			lowercase(name);
653
654			/*
655			* Map it back to an IP address and check that the given
656			* address actually is an address of this host. This is
657			* necessary because anyone with access to a name server can
658			* define arbitrary names for an IP address. Mapping from
659			* name to IP address can be trusted better (but can still be
660			* fooled if the intruder has access to the name server of
661			* the domain).
662			*/
663			memset(&hints, 0, sizeof(hints));
664			hints.ai_family = from.ss_family;
665			hints.ai_socktype = SOCK_STREAM;
666			if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
667			logit("reverse mapping checking getaddrinfo for %.700s "
668			"[%s] failed.", name, ntop);
669			return strdup(ntop);
670			}
671			/* Look for the address from the list of addresses. */
672			for (ai = aitop; ai; ai = ai->ai_next) {
673			if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
674			sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
675			(strcmp(ntop, ntop2) == 0))
676			break;
677			}
678			freeaddrinfo(aitop);
679			/* If we reached the end of the list, the address was not there. */
680			if (ai == NULL) {
681			/* Address not found for the host name. */
682			logit("Address %.100s maps to %.600s, but this does not "
683			"map back to the address.", ntop, name);
684			return strdup(ntop);
685			}
686			return strdup(name);
687			}
688
689			/*
690			* Return the canonical name of the host in the other side of the current
691			* connection. The host name is cached, so it is efficient to call this
692			* several times.
693			*/
694
695			const char *
696			auth_get_canonical_hostname(struct ssh *ssh, int use_dns)
697			{
698			static char *dnsname;
699
700			if (!use_dns)
701			return ssh_remote_ipaddr(ssh);
702			else if (dnsname != NULL)
703			return dnsname;
704			else {
705			dnsname = remote_hostname(ssh);
706			return dnsname;
707			}
708			}