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GCC Code Coverage Report

Directory:	./		Exec	Total	Coverage
File:	usr.bin/ssh/sshd/../auth2.c	Lines:	0	303	0.0 %
Date:	2017-11-07	Branches:	0	212	0.0 %


/* $OpenBSD: auth2.c,v 1.143 2017/06/24 06:34:38 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/uio.h>

#include <fcntl.h>
#include <limits.h>
#include <pwd.h>
#include <stdarg.h>
#include <string.h>
#include <unistd.h>

#include "atomicio.h"
#include "xmalloc.h"
#include "ssh2.h"
#include "packet.h"
#include "log.h"
#include "buffer.h"
#include "misc.h"
#include "servconf.h"
#include "compat.h"
#include "key.h"
#include "hostfile.h"
#include "auth.h"
#include "dispatch.h"
#include "pathnames.h"
#ifdef GSSAPI
#include "ssh-gss.h"
#endif
#include "monitor_wrap.h"
#include "ssherr.h"

/* import */
extern ServerOptions options;
extern u_char *session_id2;
extern u_int session_id2_len;

/* methods */

extern Authmethod method_none;
extern Authmethod method_pubkey;
extern Authmethod method_passwd;
extern Authmethod method_kbdint;
extern Authmethod method_hostbased;
#ifdef GSSAPI
extern Authmethod method_gssapi;
#endif

Authmethod *authmethods[] = {
	&method_none,
	&method_pubkey,
#ifdef GSSAPI
	&method_gssapi,
#endif
	&method_passwd,
	&method_kbdint,
	&method_hostbased,
	NULL
};

/* protocol */

static int input_service_request(int, u_int32_t, struct ssh *);
static int input_userauth_request(int, u_int32_t, struct ssh *);

/* helper */
static Authmethod *authmethod_lookup(Authctxt *, const char *);
static char *authmethods_get(Authctxt *authctxt);

#define MATCH_NONE	0	/* method or submethod mismatch */
#define MATCH_METHOD	1	/* method matches (no submethod specified) */
#define MATCH_BOTH	2	/* method and submethod match */
#define MATCH_PARTIAL	3	/* method matches, submethod can't be checked */
static int list_starts_with(const char *, const char *, const char *);

char *
auth2_read_banner(void)
{
	struct stat st;
	char *banner = NULL;
	size_t len, n;
	int fd;

	if ((fd = open(options.banner, O_RDONLY)) == -1)
		return (NULL);
	if (fstat(fd, &st) == -1) {
		close(fd);
		return (NULL);
	}
	if (st.st_size <= 0 || st.st_size > 1*1024*1024) {
		close(fd);
		return (NULL);
	}

	len = (size_t)st.st_size;		/* truncate */
	banner = xmalloc(len + 1);
	n = atomicio(read, fd, banner, len);
	close(fd);

	if (n != len) {
		free(banner);
		return (NULL);
	}
	banner[n] = '\0';

	return (banner);
}

static void
userauth_banner(void)
{
	char *banner = NULL;

	if (options.banner == NULL || (datafellows & SSH_BUG_BANNER) != 0)
		return;

	if ((banner = PRIVSEP(auth2_read_banner())) == NULL)
		goto done;

	packet_start(SSH2_MSG_USERAUTH_BANNER);
	packet_put_cstring(banner);
	packet_put_cstring("");		/* language, unused */
	packet_send();
	debug("userauth_banner: sent");
done:
	free(banner);
}

/*
 * loop until authctxt->success == TRUE
 */
void
do_authentication2(Authctxt *authctxt)
{
	struct ssh *ssh = active_state;		/* XXX */
	ssh->authctxt = authctxt;		/* XXX move to caller */
	ssh_dispatch_init(ssh, &dispatch_protocol_error);
	ssh_dispatch_set(ssh, SSH2_MSG_SERVICE_REQUEST, &input_service_request);
	ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &authctxt->success);
	ssh->authctxt = NULL;
}

/*ARGSUSED*/
static int
input_service_request(int type, u_int32_t seq, struct ssh *ssh)
{
	Authctxt *authctxt = ssh->authctxt;
	u_int len;
	int acceptit = 0;
	char *service = packet_get_cstring(&len);
	packet_check_eom();

	if (authctxt == NULL)
		fatal("input_service_request: no authctxt");

	if (strcmp(service, "ssh-userauth") == 0) {
		if (!authctxt->success) {
			acceptit = 1;
			/* now we can handle user-auth requests */
			ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
		}
	}
	/* XXX all other service requests are denied */

	if (acceptit) {
		packet_start(SSH2_MSG_SERVICE_ACCEPT);
		packet_put_cstring(service);
		packet_send();
		packet_write_wait();
	} else {
		debug("bad service request %s", service);
		packet_disconnect("bad service request %s", service);
	}
	free(service);
	return 0;
}

/*ARGSUSED*/
static int
input_userauth_request(int type, u_int32_t seq, struct ssh *ssh)
{
	Authctxt *authctxt = ssh->authctxt;
	Authmethod *m = NULL;
	char *user, *service, *method, *style = NULL;
	int authenticated = 0;

	if (authctxt == NULL)
		fatal("input_userauth_request: no authctxt");

	user = packet_get_cstring(NULL);
	service = packet_get_cstring(NULL);
	method = packet_get_cstring(NULL);
	debug("userauth-request for user %s service %s method %s", user, service, method);
	debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);

	if ((style = strchr(user, ':')) != NULL)
		*style++ = 0;

	if (authctxt->attempt++ == 0) {
		/* setup auth context */
		authctxt->pw = PRIVSEP(getpwnamallow(user));
		if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
			authctxt->valid = 1;
			debug2("%s: setting up authctxt for %s",
			    __func__, user);
		} else {
			/* Invalid user, fake password information */
			authctxt->pw = fakepw();
		}
		ssh_packet_set_log_preamble(ssh, "%suser %s",
		    authctxt->valid ? "authenticating " : "invalid ", user);
		setproctitle("%s%s", authctxt->valid ? user : "unknown",
		    use_privsep ? " [net]" : "");
		authctxt->user = xstrdup(user);
		authctxt->service = xstrdup(service);
		authctxt->style = style ? xstrdup(style) : NULL;
		if (use_privsep)
			mm_inform_authserv(service, style);
		userauth_banner();
		if (auth2_setup_methods_lists(authctxt) != 0)
			packet_disconnect("no authentication methods enabled");
	} else if (strcmp(user, authctxt->user) != 0 ||
	    strcmp(service, authctxt->service) != 0) {
		packet_disconnect("Change of username or service not allowed: "
		    "(%s,%s) -> (%s,%s)",
		    authctxt->user, authctxt->service, user, service);
	}
	/* reset state */
	auth2_challenge_stop(ssh);

#ifdef GSSAPI
	/* XXX move to auth2_gssapi_stop() */
	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
#endif

	auth2_authctxt_reset_info(authctxt);
	authctxt->postponed = 0;
	authctxt->server_caused_failure = 0;

	/* try to authenticate user */
	m = authmethod_lookup(authctxt, method);
	if (m != NULL && authctxt->failures < options.max_authtries) {
		debug2("input_userauth_request: try method %s", method);
		authenticated =	m->userauth(ssh);
	}
	userauth_finish(ssh, authenticated, method, NULL);

	free(service);
	free(user);
	free(method);
	return 0;
}

void
userauth_finish(struct ssh *ssh, int authenticated, const char *method,
    const char *submethod)
{
	Authctxt *authctxt = ssh->authctxt;
	char *methods;
	int partial = 0;

	if (!authctxt->valid && authenticated)
		fatal("INTERNAL ERROR: authenticated invalid user %s",
		    authctxt->user);
	if (authenticated && authctxt->postponed)
		fatal("INTERNAL ERROR: authenticated and postponed");

	/* Special handling for root */
	if (authenticated && authctxt->pw->pw_uid == 0 &&
	    !auth_root_allowed(method))
		authenticated = 0;

	if (authenticated && options.num_auth_methods != 0) {
		if (!auth2_update_methods_lists(authctxt, method, submethod)) {
			authenticated = 0;
			partial = 1;
		}
	}

	/* Log before sending the reply */
	auth_log(authctxt, authenticated, partial, method, submethod);

	/* Update information exposed to session */
	if (authenticated || partial)
		auth2_update_session_info(authctxt, method, submethod);

	if (authctxt->postponed)
		return;

	if (authenticated == 1) {
		/* turn off userauth */
		ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
		packet_start(SSH2_MSG_USERAUTH_SUCCESS);
		packet_send();
		packet_write_wait();
		/* now we can break out */
		authctxt->success = 1;
		ssh_packet_set_log_preamble(ssh, "user %s", authctxt->user);
	} else {
		/* Allow initial try of "none" auth without failure penalty */
		if (!partial && !authctxt->server_caused_failure &&
		    (authctxt->attempt > 1 || strcmp(method, "none") != 0))
			authctxt->failures++;
		if (authctxt->failures >= options.max_authtries)
			auth_maxtries_exceeded(authctxt);
		methods = authmethods_get(authctxt);
		debug3("%s: failure partial=%d next methods=\"%s\"", __func__,
		    partial, methods);
		packet_start(SSH2_MSG_USERAUTH_FAILURE);
		packet_put_cstring(methods);
		packet_put_char(partial);
		packet_send();
		packet_write_wait();
		free(methods);
	}
}

/*
 * Checks whether method is allowed by at least one AuthenticationMethods
 * methods list. Returns 1 if allowed, or no methods lists configured.
 * 0 otherwise.
 */
int
auth2_method_allowed(Authctxt *authctxt, const char *method,
    const char *submethod)
{
	u_int i;

	/*
	 * NB. authctxt->num_auth_methods might be zero as a result of
	 * auth2_setup_methods_lists(), so check the configuration.
	 */
	if (options.num_auth_methods == 0)
		return 1;
	for (i = 0; i < authctxt->num_auth_methods; i++) {
		if (list_starts_with(authctxt->auth_methods[i], method,
		    submethod) != MATCH_NONE)
			return 1;
	}
	return 0;
}

static char *
authmethods_get(Authctxt *authctxt)
{
	Buffer b;
	char *list;
	u_int i;

	buffer_init(&b);
	for (i = 0; authmethods[i] != NULL; i++) {
		if (strcmp(authmethods[i]->name, "none") == 0)
			continue;
		if (authmethods[i]->enabled == NULL ||
		    *(authmethods[i]->enabled) == 0)
			continue;
		if (!auth2_method_allowed(authctxt, authmethods[i]->name,
		    NULL))
			continue;
		if (buffer_len(&b) > 0)
			buffer_append(&b, ",", 1);
		buffer_append(&b, authmethods[i]->name,
		    strlen(authmethods[i]->name));
	}
	if ((list = sshbuf_dup_string(&b)) == NULL)
		fatal("%s: sshbuf_dup_string failed", __func__);
	buffer_free(&b);
	return list;
}

static Authmethod *
authmethod_lookup(Authctxt *authctxt, const char *name)
{
	int i;

	if (name != NULL)
		for (i = 0; authmethods[i] != NULL; i++)
			if (authmethods[i]->enabled != NULL &&
			    *(authmethods[i]->enabled) != 0 &&
			    strcmp(name, authmethods[i]->name) == 0 &&
			    auth2_method_allowed(authctxt,
			    authmethods[i]->name, NULL))
				return authmethods[i];
	debug2("Unrecognized authentication method name: %s",
	    name ? name : "NULL");
	return NULL;
}

/*
 * Check a comma-separated list of methods for validity. Is need_enable is
 * non-zero, then also require that the methods are enabled.
 * Returns 0 on success or -1 if the methods list is invalid.
 */
int
auth2_methods_valid(const char *_methods, int need_enable)
{
	char *methods, *omethods, *method, *p;
	u_int i, found;
	int ret = -1;

	if (*_methods == '\0') {
		error("empty authentication method list");
		return -1;
	}
	omethods = methods = xstrdup(_methods);
	while ((method = strsep(&methods, ",")) != NULL) {
		for (found = i = 0; !found && authmethods[i] != NULL; i++) {
			if ((p = strchr(method, ':')) != NULL)
				*p = '\0';
			if (strcmp(method, authmethods[i]->name) != 0)
				continue;
			if (need_enable) {
				if (authmethods[i]->enabled == NULL ||
				    *(authmethods[i]->enabled) == 0) {
					error("Disabled method \"%s\" in "
					    "AuthenticationMethods list \"%s\"",
					    method, _methods);
					goto out;
				}
			}
			found = 1;
			break;
		}
		if (!found) {
			error("Unknown authentication method \"%s\" in list",
			    method);
			goto out;
		}
	}
	ret = 0;
 out:
	free(omethods);
	return ret;
}

/*
 * Prune the AuthenticationMethods supplied in the configuration, removing
 * any methods lists that include disabled methods. Note that this might
 * leave authctxt->num_auth_methods == 0, even when multiple required auth
 * has been requested. For this reason, all tests for whether multiple is
 * enabled should consult options.num_auth_methods directly.
 */
int
auth2_setup_methods_lists(Authctxt *authctxt)
{
	u_int i;

	if (options.num_auth_methods == 0)
		return 0;
	debug3("%s: checking methods", __func__);
	authctxt->auth_methods = xcalloc(options.num_auth_methods,
	    sizeof(*authctxt->auth_methods));
	authctxt->num_auth_methods = 0;
	for (i = 0; i < options.num_auth_methods; i++) {
		if (auth2_methods_valid(options.auth_methods[i], 1) != 0) {
			logit("Authentication methods list \"%s\" contains "
			    "disabled method, skipping",
			    options.auth_methods[i]);
			continue;
		}
		debug("authentication methods list %d: %s",
		    authctxt->num_auth_methods, options.auth_methods[i]);
		authctxt->auth_methods[authctxt->num_auth_methods++] =
		    xstrdup(options.auth_methods[i]);
	}
	if (authctxt->num_auth_methods == 0) {
		error("No AuthenticationMethods left after eliminating "
		    "disabled methods");
		return -1;
	}
	return 0;
}

static int
list_starts_with(const char *methods, const char *method,
    const char *submethod)
{
	size_t l = strlen(method);
	int match;
	const char *p;

	if (strncmp(methods, method, l) != 0)
		return MATCH_NONE;
	p = methods + l;
	match = MATCH_METHOD;
	if (*p == ':') {
		if (!submethod)
			return MATCH_PARTIAL;
		l = strlen(submethod);
		p += 1;
		if (strncmp(submethod, p, l))
			return MATCH_NONE;
		p += l;
		match = MATCH_BOTH;
	}
	if (*p != ',' && *p != '\0')
		return MATCH_NONE;
	return match;
}

/*
 * Remove method from the start of a comma-separated list of methods.
 * Returns 0 if the list of methods did not start with that method or 1
 * if it did.
 */
static int
remove_method(char **methods, const char *method, const char *submethod)
{
	char *omethods = *methods, *p;
	size_t l = strlen(method);
	int match;

	match = list_starts_with(omethods, method, submethod);
	if (match != MATCH_METHOD && match != MATCH_BOTH)
		return 0;
	p = omethods + l;
	if (submethod && match == MATCH_BOTH)
		p += 1 + strlen(submethod); /* include colon */
	if (*p == ',')
		p++;
	*methods = xstrdup(p);
	free(omethods);
	return 1;
}

/*
 * Called after successful authentication. Will remove the successful method
 * from the start of each list in which it occurs. If it was the last method
 * in any list, then authentication is deemed successful.
 * Returns 1 if the method completed any authentication list or 0 otherwise.
 */
int
auth2_update_methods_lists(Authctxt *authctxt, const char *method,
    const char *submethod)
{
	u_int i, found = 0;

	debug3("%s: updating methods list after \"%s\"", __func__, method);
	for (i = 0; i < authctxt->num_auth_methods; i++) {
		if (!remove_method(&(authctxt->auth_methods[i]), method,
		    submethod))
			continue;
		found = 1;
		if (*authctxt->auth_methods[i] == '\0') {
			debug2("authentication methods list %d complete", i);
			return 1;
		}
		debug3("authentication methods list %d remaining: \"%s\"",
		    i, authctxt->auth_methods[i]);
	}
	/* This should not happen, but would be bad if it did */
	if (!found)
		fatal("%s: method not in AuthenticationMethods", __func__);
	return 0;
}

/* Reset method-specific information */
void auth2_authctxt_reset_info(Authctxt *authctxt)
{
	sshkey_free(authctxt->auth_method_key);
	free(authctxt->auth_method_info);
	authctxt->auth_method_key = NULL;
	authctxt->auth_method_info = NULL;
}

/* Record auth method-specific information for logs */
void
auth2_record_info(Authctxt *authctxt, const char *fmt, ...)
{
	va_list ap;
        int i;

	free(authctxt->auth_method_info);
	authctxt->auth_method_info = NULL;

	va_start(ap, fmt);
	i = vasprintf(&authctxt->auth_method_info, fmt, ap);
	va_end(ap);

	if (i < 0 || authctxt->auth_method_info == NULL)
		fatal("%s: vasprintf failed", __func__);
}

/*
 * Records a public key used in authentication. This is used for logging
 * and to ensure that the same key is not subsequently accepted again for
 * multiple authentication.
 */
void
auth2_record_key(Authctxt *authctxt, int authenticated,
    const struct sshkey *key)
{
	struct sshkey **tmp, *dup;
	int r;

	if ((r = sshkey_demote(key, &dup)) != 0)
		fatal("%s: copy key: %s", __func__, ssh_err(r));
	sshkey_free(authctxt->auth_method_key);
	authctxt->auth_method_key = dup;

	if (!authenticated)
		return;

	/* If authenticated, make sure we don't accept this key again */
	if ((r = sshkey_demote(key, &dup)) != 0)
		fatal("%s: copy key: %s", __func__, ssh_err(r));
	if (authctxt->nprev_keys >= INT_MAX ||
	    (tmp = recallocarray(authctxt->prev_keys, authctxt->nprev_keys,
	    authctxt->nprev_keys + 1, sizeof(*authctxt->prev_keys))) == NULL)
		fatal("%s: reallocarray failed", __func__);
	authctxt->prev_keys = tmp;
	authctxt->prev_keys[authctxt->nprev_keys] = dup;
	authctxt->nprev_keys++;

}

/* Checks whether a key has already been previously used for authentication */
int
auth2_key_already_used(Authctxt *authctxt, const struct sshkey *key)
{
	u_int i;
	char *fp;

	for (i = 0; i < authctxt->nprev_keys; i++) {
		if (sshkey_equal_public(key, authctxt->prev_keys[i])) {
			fp = sshkey_fingerprint(authctxt->prev_keys[i],
			    options.fingerprint_hash, SSH_FP_DEFAULT);
			debug3("%s: key already used: %s %s", __func__,
			    sshkey_type(authctxt->prev_keys[i]),
			    fp == NULL ? "UNKNOWN" : fp);
			free(fp);
			return 1;
		}
	}
	return 0;
}

/*
 * Updates authctxt->session_info with details of authentication. Should be
 * whenever an authentication method succeeds.
 */
void
auth2_update_session_info(Authctxt *authctxt, const char *method,
    const char *submethod)
{
	int r;

	if (authctxt->session_info == NULL) {
		if ((authctxt->session_info = sshbuf_new()) == NULL)
			fatal("%s: sshbuf_new", __func__);
	}

	/* Append method[/submethod] */
	if ((r = sshbuf_putf(authctxt->session_info, "%s%s%s",
	    method, submethod == NULL ? "" : "/",
	    submethod == NULL ? "" : submethod)) != 0)
		fatal("%s: append method: %s", __func__, ssh_err(r));

	/* Append key if present */
	if (authctxt->auth_method_key != NULL) {
		if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 ||
		    (r = sshkey_format_text(authctxt->auth_method_key,
		    authctxt->session_info)) != 0)
			fatal("%s: append key: %s", __func__, ssh_err(r));
	}

	if (authctxt->auth_method_info != NULL) {
		/* Ensure no ambiguity here */
		if (strchr(authctxt->auth_method_info, '\n') != NULL)
			fatal("%s: auth_method_info contains \\n", __func__);
		if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 ||
		    (r = sshbuf_putf(authctxt->session_info, "%s",
		    authctxt->auth_method_info)) != 0) {
			fatal("%s: append method info: %s",
			    __func__, ssh_err(r));
		}
	}
	if ((r = sshbuf_put_u8(authctxt->session_info, '\n')) != 0)
		fatal("%s: append: %s", __func__, ssh_err(r));
}



Generated by: GCOVR (Version 3.3)

Line	Branch	Exec	Source
1			/* $OpenBSD: auth2.c,v 1.143 2017/06/24 06:34:38 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
27			#include <sys/types.h>
28			#include <sys/stat.h>
29			#include <sys/uio.h>
30
31			#include <fcntl.h>
32			#include <limits.h>
33			#include <pwd.h>
34			#include <stdarg.h>
35			#include <string.h>
36			#include <unistd.h>
37
38			#include "atomicio.h"
39			#include "xmalloc.h"
40			#include "ssh2.h"
41			#include "packet.h"
42			#include "log.h"
43			#include "buffer.h"
44			#include "misc.h"
45			#include "servconf.h"
46			#include "compat.h"
47			#include "key.h"
48			#include "hostfile.h"
49			#include "auth.h"
50			#include "dispatch.h"
51			#include "pathnames.h"
52			#ifdef GSSAPI
53			#include "ssh-gss.h"
54			#endif
55			#include "monitor_wrap.h"
56			#include "ssherr.h"
57
58			/* import */
59			extern ServerOptions options;
60			extern u_char *session_id2;
61			extern u_int session_id2_len;
62
63			/* methods */
64
65			extern Authmethod method_none;
66			extern Authmethod method_pubkey;
67			extern Authmethod method_passwd;
68			extern Authmethod method_kbdint;
69			extern Authmethod method_hostbased;
70			#ifdef GSSAPI
71			extern Authmethod method_gssapi;
72			#endif
73
74			Authmethod *authmethods[] = {
75			&method_none,
76			&method_pubkey,
77			#ifdef GSSAPI
78			&method_gssapi,
79			#endif
80			&method_passwd,
81			&method_kbdint,
82			&method_hostbased,
83			NULL
84			};
85
86			/* protocol */
87
88			static int input_service_request(int, u_int32_t, struct ssh *);
89			static int input_userauth_request(int, u_int32_t, struct ssh *);
90
91			/* helper */
92			static Authmethod authmethod_lookup(Authctxt , const char *);
93			static char authmethods_get(Authctxt authctxt);
94
95			#define MATCH_NONE 0 /* method or submethod mismatch */
96			#define MATCH_METHOD 1 /* method matches (no submethod specified) */
97			#define MATCH_BOTH 2 /* method and submethod match */
98			#define MATCH_PARTIAL 3 /* method matches, submethod can't be checked */
99			static int list_starts_with(const char , const char , const char *);
100
101			char *
102			auth2_read_banner(void)
103			{
104			struct stat st;
105			char *banner = NULL;
106			size_t len, n;
107			int fd;
108
109			if ((fd = open(options.banner, O_RDONLY)) == -1)
110			return (NULL);
111			if (fstat(fd, &st) == -1) {
112			close(fd);
113			return (NULL);
114			}
115			if (st.st_size <= 0 \|\| st.st_size > 110241024) {
116			close(fd);
117			return (NULL);
118			}
119
120			len = (size_t)st.st_size; /* truncate */
121			banner = xmalloc(len + 1);
122			n = atomicio(read, fd, banner, len);
123			close(fd);
124
125			if (n != len) {
126			free(banner);
127			return (NULL);
128			}
129			banner[n] = '\0';
130
131			return (banner);
132			}
133
134			static void
135			userauth_banner(void)
136			{
137			char *banner = NULL;
138
139			if (options.banner == NULL \|\| (datafellows & SSH_BUG_BANNER) != 0)
140			return;
141
142			if ((banner = PRIVSEP(auth2_read_banner())) == NULL)
143			goto done;
144
145			packet_start(SSH2_MSG_USERAUTH_BANNER);
146			packet_put_cstring(banner);
147			packet_put_cstring(""); /* language, unused */
148			packet_send();
149			debug("userauth_banner: sent");
150			done:
151			free(banner);
152			}
153
154			/*
155			* loop until authctxt->success == TRUE
156			*/
157			void
158			do_authentication2(Authctxt *authctxt)
159			{
160			struct ssh ssh = active_state; / XXX */
161			ssh->authctxt = authctxt; /* XXX move to caller */
162			ssh_dispatch_init(ssh, &dispatch_protocol_error);
163			ssh_dispatch_set(ssh, SSH2_MSG_SERVICE_REQUEST, &input_service_request);
164			ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &authctxt->success);
165			ssh->authctxt = NULL;
166			}
167
168			/ARGSUSED/
169			static int
170			input_service_request(int type, u_int32_t seq, struct ssh *ssh)
171			{
172			Authctxt *authctxt = ssh->authctxt;
173			u_int len;
174			int acceptit = 0;
175			char *service = packet_get_cstring(&len);
176			packet_check_eom();
177
178			if (authctxt == NULL)
179			fatal("input_service_request: no authctxt");
180
181			if (strcmp(service, "ssh-userauth") == 0) {
182			if (!authctxt->success) {
183			acceptit = 1;
184			/* now we can handle user-auth requests */
185			ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
186			}
187			}
188			/* XXX all other service requests are denied */
189
190			if (acceptit) {
191			packet_start(SSH2_MSG_SERVICE_ACCEPT);
192			packet_put_cstring(service);
193			packet_send();
194			packet_write_wait();
195			} else {
196			debug("bad service request %s", service);
197			packet_disconnect("bad service request %s", service);
198			}
199			free(service);
200			return 0;
201			}
202
203			/ARGSUSED/
204			static int
205			input_userauth_request(int type, u_int32_t seq, struct ssh *ssh)
206			{
207			Authctxt *authctxt = ssh->authctxt;
208			Authmethod *m = NULL;
209			char user, service, method, style = NULL;
210			int authenticated = 0;
211
212			if (authctxt == NULL)
213			fatal("input_userauth_request: no authctxt");
214
215			user = packet_get_cstring(NULL);
216			service = packet_get_cstring(NULL);
217			method = packet_get_cstring(NULL);
218			debug("userauth-request for user %s service %s method %s", user, service, method);
219			debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
220
221			if ((style = strchr(user, ':')) != NULL)
222			*style++ = 0;
223
224			if (authctxt->attempt++ == 0) {
225			/* setup auth context */
226			authctxt->pw = PRIVSEP(getpwnamallow(user));
227			if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
228			authctxt->valid = 1;
229			debug2("%s: setting up authctxt for %s",
230			__func__, user);
231			} else {
232			/* Invalid user, fake password information */
233			authctxt->pw = fakepw();
234			}
235			ssh_packet_set_log_preamble(ssh, "%suser %s",
236			authctxt->valid ? "authenticating " : "invalid ", user);
237			setproctitle("%s%s", authctxt->valid ? user : "unknown",
238			use_privsep ? " [net]" : "");
239			authctxt->user = xstrdup(user);
240			authctxt->service = xstrdup(service);
241			authctxt->style = style ? xstrdup(style) : NULL;
242			if (use_privsep)
243			mm_inform_authserv(service, style);
244			userauth_banner();
245			if (auth2_setup_methods_lists(authctxt) != 0)
246			packet_disconnect("no authentication methods enabled");
247			} else if (strcmp(user, authctxt->user) != 0 \|\|
248			strcmp(service, authctxt->service) != 0) {
249			packet_disconnect("Change of username or service not allowed: "
250			"(%s,%s) -> (%s,%s)",
251			authctxt->user, authctxt->service, user, service);
252			}
253			/* reset state */
254			auth2_challenge_stop(ssh);
255
256			#ifdef GSSAPI
257			/* XXX move to auth2_gssapi_stop() */
258			ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
259			ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
260			#endif
261
262			auth2_authctxt_reset_info(authctxt);
263			authctxt->postponed = 0;
264			authctxt->server_caused_failure = 0;
265
266			/* try to authenticate user */
267			m = authmethod_lookup(authctxt, method);
268			if (m != NULL && authctxt->failures < options.max_authtries) {
269			debug2("input_userauth_request: try method %s", method);
270			authenticated = m->userauth(ssh);
271			}
272			userauth_finish(ssh, authenticated, method, NULL);
273
274			free(service);
275			free(user);
276			free(method);
277			return 0;
278			}
279
280			void
281			userauth_finish(struct ssh ssh, int authenticated, const char method,
282			const char *submethod)
283			{
284			Authctxt *authctxt = ssh->authctxt;
285			char *methods;
286			int partial = 0;
287
288			if (!authctxt->valid && authenticated)
289			fatal("INTERNAL ERROR: authenticated invalid user %s",
290			authctxt->user);
291			if (authenticated && authctxt->postponed)
292			fatal("INTERNAL ERROR: authenticated and postponed");
293
294			/* Special handling for root */
295			if (authenticated && authctxt->pw->pw_uid == 0 &&
296			!auth_root_allowed(method))
297			authenticated = 0;
298
299			if (authenticated && options.num_auth_methods != 0) {
300			if (!auth2_update_methods_lists(authctxt, method, submethod)) {
301			authenticated = 0;
302			partial = 1;
303			}
304			}
305
306			/* Log before sending the reply */
307			auth_log(authctxt, authenticated, partial, method, submethod);
308
309			/* Update information exposed to session */
310			if (authenticated \|\| partial)
311			auth2_update_session_info(authctxt, method, submethod);
312
313			if (authctxt->postponed)
314			return;
315
316			if (authenticated == 1) {
317			/* turn off userauth */
318			ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
319			packet_start(SSH2_MSG_USERAUTH_SUCCESS);
320			packet_send();
321			packet_write_wait();
322			/* now we can break out */
323			authctxt->success = 1;
324			ssh_packet_set_log_preamble(ssh, "user %s", authctxt->user);
325			} else {
326			/* Allow initial try of "none" auth without failure penalty */
327			if (!partial && !authctxt->server_caused_failure &&
328			(authctxt->attempt > 1 \|\| strcmp(method, "none") != 0))
329			authctxt->failures++;
330			if (authctxt->failures >= options.max_authtries)
331			auth_maxtries_exceeded(authctxt);
332			methods = authmethods_get(authctxt);
333			debug3("%s: failure partial=%d next methods=\"%s\"", __func__,
334			partial, methods);
335			packet_start(SSH2_MSG_USERAUTH_FAILURE);
336			packet_put_cstring(methods);
337			packet_put_char(partial);
338			packet_send();
339			packet_write_wait();
340			free(methods);
341			}
342			}
343
344			/*
345			* Checks whether method is allowed by at least one AuthenticationMethods
346			* methods list. Returns 1 if allowed, or no methods lists configured.
347			* 0 otherwise.
348			*/
349			int
350			auth2_method_allowed(Authctxt authctxt, const char method,
351			const char *submethod)
352			{
353			u_int i;
354
355			/*
356			* NB. authctxt->num_auth_methods might be zero as a result of
357			* auth2_setup_methods_lists(), so check the configuration.
358			*/
359			if (options.num_auth_methods == 0)
360			return 1;
361			for (i = 0; i < authctxt->num_auth_methods; i++) {
362			if (list_starts_with(authctxt->auth_methods[i], method,
363			submethod) != MATCH_NONE)
364			return 1;
365			}
366			return 0;
367			}
368
369			static char *
370			authmethods_get(Authctxt *authctxt)
371			{
372			Buffer b;
373			char *list;
374			u_int i;
375
376			buffer_init(&b);
377			for (i = 0; authmethods[i] != NULL; i++) {
378			if (strcmp(authmethods[i]->name, "none") == 0)
379			continue;
380			if (authmethods[i]->enabled == NULL \|\|
381			*(authmethods[i]->enabled) == 0)
382			continue;
383			if (!auth2_method_allowed(authctxt, authmethods[i]->name,
384			NULL))
385			continue;
386			if (buffer_len(&b) > 0)
387			buffer_append(&b, ",", 1);
388			buffer_append(&b, authmethods[i]->name,
389			strlen(authmethods[i]->name));
390			}
391			if ((list = sshbuf_dup_string(&b)) == NULL)
392			fatal("%s: sshbuf_dup_string failed", __func__);
393			buffer_free(&b);
394			return list;
395			}
396
397			static Authmethod *
398			authmethod_lookup(Authctxt authctxt, const char name)
399			{
400			int i;
401
402			if (name != NULL)
403			for (i = 0; authmethods[i] != NULL; i++)
404			if (authmethods[i]->enabled != NULL &&
405			*(authmethods[i]->enabled) != 0 &&
406			strcmp(name, authmethods[i]->name) == 0 &&
407			auth2_method_allowed(authctxt,
408			authmethods[i]->name, NULL))
409			return authmethods[i];
410			debug2("Unrecognized authentication method name: %s",
411			name ? name : "NULL");
412			return NULL;
413			}
414
415			/*
416			* Check a comma-separated list of methods for validity. Is need_enable is
417			* non-zero, then also require that the methods are enabled.
418			* Returns 0 on success or -1 if the methods list is invalid.
419			*/
420			int
421			auth2_methods_valid(const char *_methods, int need_enable)
422			{
423			char methods, omethods, method, p;
424			u_int i, found;
425			int ret = -1;
426
427			if (*_methods == '\0') {
428			error("empty authentication method list");
429			return -1;
430			}
431			omethods = methods = xstrdup(_methods);
432			while ((method = strsep(&methods, ",")) != NULL) {
433			for (found = i = 0; !found && authmethods[i] != NULL; i++) {
434			if ((p = strchr(method, ':')) != NULL)
435			*p = '\0';
436			if (strcmp(method, authmethods[i]->name) != 0)
437			continue;
438			if (need_enable) {
439			if (authmethods[i]->enabled == NULL \|\|
440			*(authmethods[i]->enabled) == 0) {
441			error("Disabled method \"%s\" in "
442			"AuthenticationMethods list \"%s\"",
443			method, _methods);
444			goto out;
445			}
446			}
447			found = 1;
448			break;
449			}
450			if (!found) {
451			error("Unknown authentication method \"%s\" in list",
452			method);
453			goto out;
454			}
455			}
456			ret = 0;
457			out:
458			free(omethods);
459			return ret;
460			}
461
462			/*
463			* Prune the AuthenticationMethods supplied in the configuration, removing
464			* any methods lists that include disabled methods. Note that this might
465			* leave authctxt->num_auth_methods == 0, even when multiple required auth
466			* has been requested. For this reason, all tests for whether multiple is
467			* enabled should consult options.num_auth_methods directly.
468			*/
469			int
470			auth2_setup_methods_lists(Authctxt *authctxt)
471			{
472			u_int i;
473
474			if (options.num_auth_methods == 0)
475			return 0;
476			debug3("%s: checking methods", __func__);
477			authctxt->auth_methods = xcalloc(options.num_auth_methods,
478			sizeof(*authctxt->auth_methods));
479			authctxt->num_auth_methods = 0;
480			for (i = 0; i < options.num_auth_methods; i++) {
481			if (auth2_methods_valid(options.auth_methods[i], 1) != 0) {
482			logit("Authentication methods list \"%s\" contains "
483			"disabled method, skipping",
484			options.auth_methods[i]);
485			continue;
486			}
487			debug("authentication methods list %d: %s",
488			authctxt->num_auth_methods, options.auth_methods[i]);
489			authctxt->auth_methods[authctxt->num_auth_methods++] =
490			xstrdup(options.auth_methods[i]);
491			}
492			if (authctxt->num_auth_methods == 0) {
493			error("No AuthenticationMethods left after eliminating "
494			"disabled methods");
495			return -1;
496			}
497			return 0;
498			}
499
500			static int
501			list_starts_with(const char methods, const char method,
502			const char *submethod)
503			{
504			size_t l = strlen(method);
505			int match;
506			const char *p;
507
508			if (strncmp(methods, method, l) != 0)
509			return MATCH_NONE;
510			p = methods + l;
511			match = MATCH_METHOD;
512			if (*p == ':') {
513			if (!submethod)
514			return MATCH_PARTIAL;
515			l = strlen(submethod);
516			p += 1;
517			if (strncmp(submethod, p, l))
518			return MATCH_NONE;
519			p += l;
520			match = MATCH_BOTH;
521			}
522			if (p != ',' && p != '\0')
523			return MATCH_NONE;
524			return match;
525			}
526
527			/*
528			* Remove method from the start of a comma-separated list of methods.
529			* Returns 0 if the list of methods did not start with that method or 1
530			* if it did.
531			*/
532			static int
533			remove_method(char *methods, const char method, const char *submethod)
534			{
535			char omethods = methods, *p;
536			size_t l = strlen(method);
537			int match;
538
539			match = list_starts_with(omethods, method, submethod);
540			if (match != MATCH_METHOD && match != MATCH_BOTH)
541			return 0;
542			p = omethods + l;
543			if (submethod && match == MATCH_BOTH)
544			p += 1 + strlen(submethod); /* include colon */
545			if (*p == ',')
546			p++;
547			*methods = xstrdup(p);
548			free(omethods);
549			return 1;
550			}
551
552			/*
553			* Called after successful authentication. Will remove the successful method
554			* from the start of each list in which it occurs. If it was the last method
555			* in any list, then authentication is deemed successful.
556			* Returns 1 if the method completed any authentication list or 0 otherwise.
557			*/
558			int
559			auth2_update_methods_lists(Authctxt authctxt, const char method,
560			const char *submethod)
561			{
562			u_int i, found = 0;
563
564			debug3("%s: updating methods list after \"%s\"", __func__, method);
565			for (i = 0; i < authctxt->num_auth_methods; i++) {
566			if (!remove_method(&(authctxt->auth_methods[i]), method,
567			submethod))
568			continue;
569			found = 1;
570			if (*authctxt->auth_methods[i] == '\0') {
571			debug2("authentication methods list %d complete", i);
572			return 1;
573			}
574			debug3("authentication methods list %d remaining: \"%s\"",
575			i, authctxt->auth_methods[i]);
576			}
577			/* This should not happen, but would be bad if it did */
578			if (!found)
579			fatal("%s: method not in AuthenticationMethods", __func__);
580			return 0;
581			}
582
583			/* Reset method-specific information */
584			void auth2_authctxt_reset_info(Authctxt *authctxt)
585			{
586			sshkey_free(authctxt->auth_method_key);
587			free(authctxt->auth_method_info);
588			authctxt->auth_method_key = NULL;
589			authctxt->auth_method_info = NULL;
590			}
591
592			/* Record auth method-specific information for logs */
593			void
594			auth2_record_info(Authctxt authctxt, const char fmt, ...)
595			{
596			va_list ap;
597			int i;
598
599			free(authctxt->auth_method_info);
600			authctxt->auth_method_info = NULL;
601
602			va_start(ap, fmt);
603			i = vasprintf(&authctxt->auth_method_info, fmt, ap);
604			va_end(ap);
605
606			if (i < 0 \|\| authctxt->auth_method_info == NULL)
607			fatal("%s: vasprintf failed", __func__);
608			}
609
610			/*
611			* Records a public key used in authentication. This is used for logging
612			* and to ensure that the same key is not subsequently accepted again for
613			* multiple authentication.
614			*/
615			void
616			auth2_record_key(Authctxt *authctxt, int authenticated,
617			const struct sshkey *key)
618			{
619			struct sshkey *tmp, dup;
620			int r;
621
622			if ((r = sshkey_demote(key, &dup)) != 0)
623			fatal("%s: copy key: %s", __func__, ssh_err(r));
624			sshkey_free(authctxt->auth_method_key);
625			authctxt->auth_method_key = dup;
626
627			if (!authenticated)
628			return;
629
630			/* If authenticated, make sure we don't accept this key again */
631			if ((r = sshkey_demote(key, &dup)) != 0)
632			fatal("%s: copy key: %s", __func__, ssh_err(r));
633			if (authctxt->nprev_keys >= INT_MAX \|\|
634			(tmp = recallocarray(authctxt->prev_keys, authctxt->nprev_keys,
635			authctxt->nprev_keys + 1, sizeof(*authctxt->prev_keys))) == NULL)
636			fatal("%s: reallocarray failed", __func__);
637			authctxt->prev_keys = tmp;
638			authctxt->prev_keys[authctxt->nprev_keys] = dup;
639			authctxt->nprev_keys++;
640
641			}
642
643			/* Checks whether a key has already been previously used for authentication */
644			int
645			auth2_key_already_used(Authctxt authctxt, const struct sshkey key)
646			{
647			u_int i;
648			char *fp;
649
650			for (i = 0; i < authctxt->nprev_keys; i++) {
651			if (sshkey_equal_public(key, authctxt->prev_keys[i])) {
652			fp = sshkey_fingerprint(authctxt->prev_keys[i],
653			options.fingerprint_hash, SSH_FP_DEFAULT);
654			debug3("%s: key already used: %s %s", __func__,
655			sshkey_type(authctxt->prev_keys[i]),
656			fp == NULL ? "UNKNOWN" : fp);
657			free(fp);
658			return 1;
659			}
660			}
661			return 0;
662			}
663
664			/*
665			* Updates authctxt->session_info with details of authentication. Should be
666			* whenever an authentication method succeeds.
667			*/
668			void
669			auth2_update_session_info(Authctxt authctxt, const char method,
670			const char *submethod)
671			{
672			int r;
673
674			if (authctxt->session_info == NULL) {
675			if ((authctxt->session_info = sshbuf_new()) == NULL)
676			fatal("%s: sshbuf_new", __func__);
677			}
678
679			/* Append method[/submethod] */
680			if ((r = sshbuf_putf(authctxt->session_info, "%s%s%s",
681			method, submethod == NULL ? "" : "/",
682			submethod == NULL ? "" : submethod)) != 0)
683			fatal("%s: append method: %s", __func__, ssh_err(r));
684
685			/* Append key if present */
686			if (authctxt->auth_method_key != NULL) {
687			if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 \|\|
688			(r = sshkey_format_text(authctxt->auth_method_key,
689			authctxt->session_info)) != 0)
690			fatal("%s: append key: %s", __func__, ssh_err(r));
691			}
692
693			if (authctxt->auth_method_info != NULL) {
694			/* Ensure no ambiguity here */
695			if (strchr(authctxt->auth_method_info, '\n') != NULL)
696			fatal("%s: auth_method_info contains \\n", __func__);
697			if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 \|\|
698			(r = sshbuf_putf(authctxt->session_info, "%s",
699			authctxt->auth_method_info)) != 0) {
700			fatal("%s: append method info: %s",
701			__func__, ssh_err(r));
702			}
703			}
704			if ((r = sshbuf_put_u8(authctxt->session_info, '\n')) != 0)
705			fatal("%s: append: %s", __func__, ssh_err(r));
706			}
707