~ubuntu-branches/ubuntu/dapper/openssh/dapper-security

/*

 * 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"

RCSID("$OpenBSD: auth2.c,v 1.107 2004/07/28 09:40:29 markus Exp $");

#include "ssh2.h"

#include "xmalloc.h"

#include "packet.h"

#include "log.h"

#include "servconf.h"

#include "compat.h"

#include "auth.h"

#include "dispatch.h"

#include "pathnames.h"

#include "monitor_wrap.h"

#include "buffer.h"

#ifdef GSSAPI

#include "ssh-gss.h"

#endif

/* import */

extern ServerOptions options;

extern u_char *session_id2;

extern u_int session_id2_len;

extern Buffer loginmsg;

/* 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_gsskeyex;

extern Authmethod method_gssapi;

#endif

Authmethod *authmethods[] = {

	&method_none,

	&method_pubkey,

#ifdef GSSAPI

	&method_gsskeyex,

	&method_gssapi,

#endif

	&method_passwd,

	&method_kbdint,

	&method_hostbased,

	NULL

};

/* protocol */

static void input_service_request(int, u_int32_t, void *);

static void input_userauth_request(int, u_int32_t, void *);

/* helper */

static Authmethod *authmethod_lookup(const char *);

static char *authmethods_get(void);

int user_key_allowed(struct passwd *, Key *);

/*

 * loop until authctxt->success == TRUE

 */

void

do_authentication2(Authctxt *authctxt)

{

	/* challenge-response is implemented via keyboard interactive */

	if (options.challenge_response_authentication)

		options.kbd_interactive_authentication = 1;

	dispatch_init(&dispatch_protocol_error);

	dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);

	dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);

}

static void

input_service_request(int type, u_int32_t seq, void *ctxt)

{

	Authctxt *authctxt = ctxt;

	u_int len;

	int acceptit = 0;

	char *service = packet_get_string(&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 */

			dispatch_set(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);

	}

	xfree(service);

}

static void

input_userauth_request(int type, u_int32_t seq, void *ctxt)

{

	Authctxt *authctxt = ctxt;

	Authmethod *m = NULL;

	char *user, *service, *method, *style = NULL, *role = NULL;

	int authenticated = 0;

	if (authctxt == NULL)

		fatal("input_userauth_request: no authctxt");

	user = packet_get_string(NULL);

	service = packet_get_string(NULL);

	method = packet_get_string(NULL);

	debug("userauth-request for user %s service %s method %s", user, service, method);

	debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);

	if ((role = strchr(user, '/')) != NULL)

		*role++ = 0;

	if ((style = strchr(user, ':')) != NULL)

		*style++ = 0;

	else if (role && (style = strchr(role, ':')) != NULL)

		*style++ = '\0';

	if (authctxt->attempt++ == 0) {

		/* setup auth context */

		authctxt->pw = PRIVSEP(getpwnamallow(user));

		authctxt->user = xstrdup(user);

		if (authctxt->pw && strcmp(service, "ssh-connection")==0) {

			authctxt->valid = 1;

			debug2("input_userauth_request: setting up authctxt for %s", user);

#ifdef USE_PAM

			if (options.use_pam)

				PRIVSEP(start_pam(authctxt));

#endif

		} else {

			logit("input_userauth_request: invalid user %s", user);

			authctxt->pw = fakepw();

#ifdef USE_PAM

			if (options.use_pam)

				PRIVSEP(start_pam(authctxt));

#endif

#ifdef SSH_AUDIT_EVENTS

			PRIVSEP(audit_event(SSH_INVALID_USER));

#endif

		}

		setproctitle("%s%s", authctxt->valid ? user : "unknown",

		    use_privsep ? " [net]" : "");

		authctxt->service = xstrdup(service);

		authctxt->style = style ? xstrdup(style) : NULL;

		authctxt->role = role ? xstrdup(role) : NULL;

		if (use_privsep)

			mm_inform_authserv(service, style, role);

	} 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(authctxt);

#ifdef GSSAPI

	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);

	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);

#endif

	authctxt->postponed = 0;

	/* try to authenticate user */

	m = authmethod_lookup(method);

	if (m != NULL) {

		debug2("input_userauth_request: try method %s", method);

		authenticated =	m->userauth(authctxt);

	}

	userauth_finish(authctxt, authenticated, method);

	xfree(service);

	xfree(user);

	xfree(method);

}

void

userauth_finish(Authctxt *authctxt, int authenticated, char *method)

{

	char *methods;

	if (!authctxt->valid && authenticated)

		fatal("INTERNAL ERROR: authenticated invalid user %s",

		    authctxt->user);

	/* Special handling for root */

	if (authenticated && authctxt->pw->pw_uid == 0 &&

	    !auth_root_allowed(method)) {

		authenticated = 0;

#ifdef SSH_AUDIT_EVENTS

		PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));

#endif

	}

#ifdef USE_PAM

	if (options.use_pam && authenticated) {

		if (!PRIVSEP(do_pam_account())) {

			/* if PAM returned a message, send it to the user */

			if (buffer_len(&loginmsg) > 0) {

				buffer_append(&loginmsg, "\0", 1);

				userauth_send_banner(buffer_ptr(&loginmsg));

				packet_write_wait();

			}

			fatal("Access denied for user %s by PAM account "

			    "configuration", authctxt->user);

		}

	}

#endif

#ifdef _UNICOS

	if (authenticated && cray_access_denied(authctxt->user)) {

		authenticated = 0;

		fatal("Access denied for user %s.",authctxt->user);

	}

#endif /* _UNICOS */

	/* Log before sending the reply */

	auth_log(authctxt, authenticated, method, " ssh2");

	if (authctxt->postponed)

		return;

	/* XXX todo: check if multiple auth methods are needed */

	if (authenticated == 1) {

		/* turn off userauth */

		dispatch_set(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;

	} else {

		if (authctxt->failures++ > options.max_authtries) {

#ifdef SSH_AUDIT_EVENTS

			PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));

#endif

			packet_disconnect(AUTH_FAIL_MSG, authctxt->user);

		}

		methods = authmethods_get();

		packet_start(SSH2_MSG_USERAUTH_FAILURE);

		packet_put_cstring(methods);

		packet_put_char(0);	/* XXX partial success, unused */

		packet_send();

		packet_write_wait();

		xfree(methods);

	}

}

#define	DELIM	","

static char *

authmethods_get(void)

{

	Buffer b;

	char *list;

	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) {

			if (buffer_len(&b) > 0)

				buffer_append(&b, ",", 1);

			buffer_append(&b, authmethods[i]->name,

			    strlen(authmethods[i]->name));

		}

	}

	buffer_append(&b, "\0", 1);

	list = xstrdup(buffer_ptr(&b));

	buffer_free(&b);

	return list;

}

static Authmethod *

authmethod_lookup(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)

				return authmethods[i];

	debug2("Unrecognized authentication method name: %s",

	    name ? name : "NULL");

	return NULL;

}