auth2.c - third_party/openssh-portable - Git at Google

 /*
  * 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 1.93 2002/05/31 11:35:15 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"

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

 Authctxt *x_authctxt = NULL;

 /* methods */

 extern Authmethod method_none;
 extern Authmethod method_pubkey;
 extern Authmethod method_passwd;
 extern Authmethod method_kbdint;
 extern Authmethod method_hostbased;

 Authmethod *authmethods[] = {
 	&method_none,
 	&method_pubkey,
 	&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 *);
 int hostbased_key_allowed(struct passwd *, const char *, char *, Key *);

 /*
  * loop until authctxt->success == TRUE
  */

 Authctxt *
 do_authentication2(void)
 {
 	Authctxt *authctxt = authctxt_new();

 	x_authctxt = authctxt;		/*XXX*/

 	/* challenge-response is implemented via keyboard interactive */
 	if (options.challenge_response_authentication)
 		options.kbd_interactive_authentication = 1;
 	if (options.pam_authentication_via_kbd_int)
 		options.kbd_interactive_authentication = 1;
 	if (use_privsep)
 		options.pam_authentication_via_kbd_int = 0;

 	dispatch_init(&dispatch_protocol_error);
 	dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
 	dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);

 	return (authctxt);
 }

 static void
 input_service_request(int type, u_int32_t seq, void *ctxt)
 {
 	Authctxt *authctxt = ctxt;
 	u_int len;
 	int accept = 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) {
 			accept = 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 (accept) {
 		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;
 	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 ((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("input_userauth_request: setting up authctxt for %s", user);
 #ifdef USE_PAM
 			PRIVSEP(start_pam(authctxt->pw->pw_name));
 #endif
 		} else {
 			log("input_userauth_request: illegal user %s", user);
 #ifdef USE_PAM
 			PRIVSEP(start_pam("NOUSER"));
 #endif
 		}
 		setproctitle("%s%s", authctxt->pw ? 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);
 	} 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);
 	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 USE_PAM
 	if (!use_privsep && authenticated && authctxt->user &&
 	    !do_pam_account(authctxt->user, NULL))
 		authenticated = 0;
 #endif /* USE_PAM */

 	/* 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++ > AUTH_FAIL_MAX) {
 #ifdef WITH_AIXAUTHENTICATE
 			/* XXX: privsep */
 			loginfailed(authctxt->user,
 			    get_canonical_hostname(options.verify_reverse_mapping),
 			    "ssh");
 #endif /* WITH_AIXAUTHENTICATE */
 			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);
 	}
 }

 /* get current user */

 struct passwd*
 auth_get_user(void)
 {
 	return (x_authctxt != NULL && x_authctxt->valid) ? x_authctxt->pw : NULL;
 }

 #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;
 }
	/*
	* 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 1.93 2002/05/31 11:35:15 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"

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

	Authctxt *x_authctxt = NULL;

	/* methods */

	extern Authmethod method_none;
	extern Authmethod method_pubkey;
	extern Authmethod method_passwd;
	extern Authmethod method_kbdint;
	extern Authmethod method_hostbased;

	Authmethod *authmethods[] = {
	&method_none,
	&method_pubkey,
	&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 );
	int hostbased_key_allowed(struct passwd , const char , char , Key );

	/*
	* loop until authctxt->success == TRUE
	*/

	Authctxt *
	do_authentication2(void)
	{
	Authctxt *authctxt = authctxt_new();

	x_authctxt = authctxt; /XXX/

	/* challenge-response is implemented via keyboard interactive */
	if (options.challenge_response_authentication)
	options.kbd_interactive_authentication = 1;
	if (options.pam_authentication_via_kbd_int)
	options.kbd_interactive_authentication = 1;
	if (use_privsep)
	options.pam_authentication_via_kbd_int = 0;

	dispatch_init(&dispatch_protocol_error);
	dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
	dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);

	return (authctxt);
	}

	static void
	input_service_request(int type, u_int32_t seq, void *ctxt)
	{
	Authctxt *authctxt = ctxt;
	u_int len;
	int accept = 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) {
	accept = 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 (accept) {
	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;
	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 ((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("input_userauth_request: setting up authctxt for %s", user);
	#ifdef USE_PAM
	PRIVSEP(start_pam(authctxt->pw->pw_name));
	#endif
	} else {
	log("input_userauth_request: illegal user %s", user);
	#ifdef USE_PAM
	PRIVSEP(start_pam("NOUSER"));
	#endif
	}
	setproctitle("%s%s", authctxt->pw ? 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);
	} 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);
	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 USE_PAM
	if (!use_privsep && authenticated && authctxt->user &&
	!do_pam_account(authctxt->user, NULL))
	authenticated = 0;
	#endif /* USE_PAM */

	/* 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++ > AUTH_FAIL_MAX) {
	#ifdef WITH_AIXAUTHENTICATE
	/* XXX: privsep */
	loginfailed(authctxt->user,
	get_canonical_hostname(options.verify_reverse_mapping),
	"ssh");
	#endif /* WITH_AIXAUTHENTICATE */
	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);
	}
	}

	/* get current user */

	struct passwd*
	auth_get_user(void)
	{
	return (x_authctxt != NULL && x_authctxt->valid) ? x_authctxt->pw : NULL;
	}

	#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;
	}