auth2.c - security/openssh-library - Rivoreo Source Code Repositories

 /*
  * 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 1.45 2001/03/04 01:46:29 djm Exp $");

 #include <openssl/evp.h>

 #include "ssh2.h"
 #include "xmalloc.h"
 #include "rsa.h"
 #include "sshpty.h"
 #include "packet.h"
 #include "buffer.h"
 #include "log.h"
 #include "servconf.h"
 #include "compat.h"
 #include "channels.h"
 #include "bufaux.h"
 #include "auth.h"
 #include "session.h"
 #include "dispatch.h"
 #include "key.h"
 #include "cipher.h"
 #include "kex.h"
 #include "pathnames.h"
 #include "uidswap.h"
 #include "auth-options.h"
 #include "misc.h"

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

 #ifdef WITH_AIXAUTHENTICATE
 extern char *aixloginmsg;
 #endif

 static Authctxt	*x_authctxt = NULL;
 static int one = 1;

 typedef struct Authmethod Authmethod;
 struct Authmethod {
 	char	*name;
 	int	(*userauth)(Authctxt *authctxt);
 	int	*enabled;
 };

 /* protocol */

 void	input_service_request(int type, int plen, void *ctxt);
 void	input_userauth_request(int type, int plen, void *ctxt);
 void	protocol_error(int type, int plen, void *ctxt);

 /* helper */
 Authmethod	*authmethod_lookup(const char *name);
 int	user_key_allowed(struct passwd *pw, Key *key);
 char	*authmethods_get(void);

 /* auth */
 void	userauth_banner(void);
 int	userauth_none(Authctxt *authctxt);
 int	userauth_passwd(Authctxt *authctxt);
 int	userauth_pubkey(Authctxt *authctxt);
 int	userauth_kbdint(Authctxt *authctxt);

 Authmethod authmethods[] = {
 	{"none",
 		userauth_none,
 		&one},
 	{"publickey",
 		userauth_pubkey,
 		&options.pubkey_authentication},
 	{"password",
 		userauth_passwd,
 		&options.password_authentication},
 	{"keyboard-interactive",
 		userauth_kbdint,
 		&options.kbd_interactive_authentication},
 	{NULL, NULL, NULL}
 };

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

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

 	x_authctxt = authctxt;		/*XXX*/

 	/* challenge-reponse is implemented via keyboard interactive */
 	if (options.challenge_reponse_authentication)
 		options.kbd_interactive_authentication = 1;

 	dispatch_init(&protocol_error);
 	dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
 	dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);
 	do_authenticated2(authctxt);
 }

 void
 protocol_error(int type, int plen, void *ctxt)
 {
 	log("auth: protocol error: type %d plen %d", type, plen);
 	packet_start(SSH2_MSG_UNIMPLEMENTED);
 	packet_put_int(0);
 	packet_send();
 	packet_write_wait();
 }

 void
 input_service_request(int type, int plen, void *ctxt)
 {
 	Authctxt *authctxt = ctxt;
 	u_int len;
 	int accept = 0;
 	char *service = packet_get_string(&len);
 	packet_done();

 	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);
 }

 void
 input_userauth_request(int type, int plen, 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 */
 		struct passwd *pw = NULL;
 		pw = getpwnam(user);
 		if (pw && allowed_user(pw) && strcmp(service, "ssh-connection")==0) {
 			authctxt->pw = pwcopy(pw);
 			authctxt->valid = 1;
 			debug2("input_userauth_request: setting up authctxt for %s", user);
 #ifdef USE_PAM
 			start_pam(pw->pw_name);
 #endif
 		} else {
 			log("input_userauth_request: illegal user %s", user);
 #ifdef USE_PAM
 			start_pam("NOUSER");
 #endif
 		}
 		setproctitle("%s", pw ? user : "unknown");
 		authctxt->user = xstrdup(user);
 		authctxt->service = xstrdup(service);
 		authctxt->style = style ? xstrdup(style) : NULL; /* currently unused */
 	} else if (authctxt->valid) {
 		if (strcmp(user, authctxt->user) != 0 ||
 		    strcmp(service, authctxt->service) != 0) {
 			log("input_userauth_request: missmatch: (%s,%s)!=(%s,%s)",
 			    user, service, authctxt->user, authctxt->service);
 			authctxt->valid = 0;
 		}
 	}
 	/* reset state */
 	dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, &protocol_error);
 	authctxt->postponed = 0;
 #ifdef BSD_AUTH
 	if (authctxt->as) {
 		auth_close(authctxt->as);
 		authctxt->as = NULL;
 	}
 #endif

 	/* try to authenticate user */
 	m = authmethod_lookup(method);
 	if (m != NULL) {
 		debug2("input_userauth_request: try method %s", method);
 		authenticated =	m->userauth(authctxt);
 	}
 	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 (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)
 		userauth_reply(authctxt, authenticated);

 	xfree(service);
 	xfree(user);
 	xfree(method);
 }

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

 	if (options.banner == NULL || (datafellows & SSH_BUG_BANNER))
 		return;
 	if ((fd = open(options.banner, O_RDONLY)) < 0) {
 		error("userauth_banner: open %s failed: %s",
 		    options.banner, strerror(errno));
 		return;
 	}
 	if (fstat(fd, &st) < 0)
 		goto done;
 	len = st.st_size;
 	banner = xmalloc(len + 1);
 	if ((n = read(fd, banner, len)) < 0)
 		goto done;
 	banner[n] = '\0';
 	packet_start(SSH2_MSG_USERAUTH_BANNER);
 	packet_put_cstring(banner);
 	packet_put_cstring("");		/* language, unused */
 	packet_send();
 	debug("userauth_banner: sent");
 done:
 	if (banner)
 		xfree(banner);
 	close(fd);
 	return;
 }

 void
 userauth_reply(Authctxt *authctxt, int authenticated)
 {
 	char *methods;

 	/* XXX todo: check if multiple auth methods are needed */
 	if (authenticated == 1) {
 #ifdef WITH_AIXAUTHENTICATE
 		/* We don't have a pty yet, so just label the line as "ssh" */
 		if (loginsuccess(authctxt->user?authctxt->user:"NOUSER",
 		    get_canonical_hostname(options.reverse_mapping_check),
 		    "ssh", &aixloginmsg) < 0)
 			aixloginmsg = NULL;
 #endif /* WITH_AIXAUTHENTICATE */
 		/* turn off userauth */
 		dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &protocol_error);
 		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)
 			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);
 	}
 }

 int
 userauth_none(Authctxt *authctxt)
 {
 	/* disable method "none", only allowed one time */
 	Authmethod *m = authmethod_lookup("none");
 	if (m != NULL)
 		m->enabled = NULL;
 	packet_done();
 	userauth_banner();

 	if (authctxt->valid == 0)
 		return(0);

 #ifdef HAVE_CYGWIN
 	if (check_nt_auth(1, authctxt->pw->pw_uid) == 0)
 		return(0);
 #endif
 #ifdef USE_PAM
 	return auth_pam_password(authctxt->pw, "");
 #elif defined(HAVE_OSF_SIA)
 	return 0;
 #else /* !HAVE_OSF_SIA && !USE_PAM */
 	return auth_password(authctxt, "");
 #endif /* USE_PAM */
 }

 int
 userauth_passwd(Authctxt *authctxt)
 {
 	char *password;
 	int authenticated = 0;
 	int change;
 	u_int len;
 	change = packet_get_char();
 	if (change)
 		log("password change not supported");
 	password = packet_get_string(&len);
 	packet_done();
 	if (authctxt->valid &&
 #ifdef HAVE_CYGWIN
 		check_nt_auth(1, authctxt->pw->pw_uid) &&
 #endif
 #ifdef USE_PAM
 	    auth_pam_password(authctxt->pw, password) == 1)
 #elif defined(HAVE_OSF_SIA)
 	    auth_sia_password(authctxt->user, password) == 1)
 #else /* !USE_PAM && !HAVE_OSF_SIA */
 	    auth_password(authctxt, password) == 1)
 #endif /* USE_PAM */
 		authenticated = 1;
 	memset(password, 0, len);
 	xfree(password);
 	return authenticated;
 }

 int
 userauth_kbdint(Authctxt *authctxt)
 {
 	int authenticated = 0;
 	char *lang = NULL;
 	char *devs = NULL;

 	lang = packet_get_string(NULL);
 	devs = packet_get_string(NULL);
 	packet_done();

 	debug("keyboard-interactive language %s devs %s", lang, devs);

 	if (options.challenge_reponse_authentication)
 		authenticated = auth2_challenge(authctxt, devs);

 #ifdef USE_PAM
 	if (authenticated == 0)
 		authenticated = auth2_pam(authctxt);
 #endif
 	xfree(lang);
 	xfree(devs);
 #ifdef HAVE_CYGWIN
 	if (check_nt_auth(0, authctxt->pw->pw_uid) == 0)
 		return(0);
 #endif
 	return authenticated;
 }

 int
 userauth_pubkey(Authctxt *authctxt)
 {
 	Buffer b;
 	Key *key;
 	char *pkalg, *pkblob, *sig;
 	u_int alen, blen, slen;
 	int have_sig, pktype;
 	int authenticated = 0;

 	if (!authctxt->valid) {
 		debug2("userauth_pubkey: disabled because of invalid user");
 		return 0;
 	}
 	have_sig = packet_get_char();
 	if (datafellows & SSH_BUG_PKAUTH) {
 		debug2("userauth_pubkey: SSH_BUG_PKAUTH");
 		/* no explicit pkalg given */
 		pkblob = packet_get_string(&blen);
 		buffer_init(&b);
 		buffer_append(&b, pkblob, blen);
 		/* so we have to extract the pkalg from the pkblob */
 		pkalg = buffer_get_string(&b, &alen);
 		buffer_free(&b);
 	} else {
 		pkalg = packet_get_string(&alen);
 		pkblob = packet_get_string(&blen);
 	}
 	pktype = key_type_from_name(pkalg);
 	if (pktype == KEY_UNSPEC) {
 		/* this is perfectly legal */
 		log("userauth_pubkey: unsupported public key algorithm: %s", pkalg);
 		xfree(pkalg);
 		xfree(pkblob);
 		return 0;
 	}
 	key = key_from_blob(pkblob, blen);
 	if (key != NULL) {
 		if (have_sig) {
 			sig = packet_get_string(&slen);
 			packet_done();
 			buffer_init(&b);
 			if (datafellows & SSH_OLD_SESSIONID) {
 				buffer_append(&b, session_id2, session_id2_len);
 			} else {
 				buffer_put_string(&b, session_id2, session_id2_len);
 			}
 			/* reconstruct packet */
 			buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
 			buffer_put_cstring(&b, authctxt->user);
 			buffer_put_cstring(&b,
 			    datafellows & SSH_BUG_PKSERVICE ?
 			    "ssh-userauth" :
 			    authctxt->service);
 			if (datafellows & SSH_BUG_PKAUTH) {
 				buffer_put_char(&b, have_sig);
 			} else {
 				buffer_put_cstring(&b, "publickey");
 				buffer_put_char(&b, have_sig);
 				buffer_put_cstring(&b, key_ssh_name(key));
 			}
 			buffer_put_string(&b, pkblob, blen);
 #ifdef DEBUG_PK
 			buffer_dump(&b);
 #endif
 			/* test for correct signature */
 			if (user_key_allowed(authctxt->pw, key) &&
 			    key_verify(key, sig, slen, buffer_ptr(&b), buffer_len(&b)) == 1)
 				authenticated = 1;
 			buffer_clear(&b);
 			xfree(sig);
 		} else {
 			debug("test whether pkalg/pkblob are acceptable");
 			packet_done();

 			/* XXX fake reply and always send PK_OK ? */
 			/*
 			 * XXX this allows testing whether a user is allowed
 			 * to login: if you happen to have a valid pubkey this
 			 * message is sent. the message is NEVER sent at all
 			 * if a user is not allowed to login. is this an
 			 * issue? -markus
 			 */
 			if (user_key_allowed(authctxt->pw, key)) {
 				packet_start(SSH2_MSG_USERAUTH_PK_OK);
 				packet_put_string(pkalg, alen);
 				packet_put_string(pkblob, blen);
 				packet_send();
 				packet_write_wait();
 				authctxt->postponed = 1;
 			}
 		}
 		if (authenticated != 1)
 			auth_clear_options();
 		key_free(key);
 	}
 	debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
 	xfree(pkalg);
 	xfree(pkblob);
 #ifdef HAVE_CYGWIN
 	if (check_nt_auth(0, authctxt->pw->pw_uid) == 0)
 		return(0);
 #endif
 	return authenticated;
 }

 /* get current user */

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

 #define	DELIM	","

 char *
 authmethods_get(void)
 {
 	Authmethod *method = NULL;
 	u_int size = 0;
 	char *list;

 	for (method = authmethods; method->name != NULL; method++) {
 		if (strcmp(method->name, "none") == 0)
 			continue;
 		if (method->enabled != NULL && *(method->enabled) != 0) {
 			if (size != 0)
 				size += strlen(DELIM);
 			size += strlen(method->name);
 		}
 	}
 	size++;			/* trailing '\0' */
 	list = xmalloc(size);
 	list[0] = '\0';

 	for (method = authmethods; method->name != NULL; method++) {
 		if (strcmp(method->name, "none") == 0)
 			continue;
 		if (method->enabled != NULL && *(method->enabled) != 0) {
 			if (list[0] != '\0')
 				strlcat(list, DELIM, size);
 			strlcat(list, method->name, size);
 		}
 	}
 	return list;
 }

 Authmethod *
 authmethod_lookup(const char *name)
 {
 	Authmethod *method = NULL;
 	if (name != NULL)
 		for (method = authmethods; method->name != NULL; method++)
 			if (method->enabled != NULL &&
 			    *(method->enabled) != 0 &&
 			    strcmp(name, method->name) == 0)
 				return method;
 	debug2("Unrecognized authentication method name: %s", name ? name : "NULL");
 	return NULL;
 }

 /* return 1 if user allows given key */
 int
 user_key_allowed(struct passwd *pw, Key *key)
 {
 	char line[8192], file[MAXPATHLEN];
 	int found_key = 0;
 	FILE *f;
 	u_long linenum = 0;
 	struct stat st;
 	Key *found;

 	if (pw == NULL)
 		return 0;

 	/* Temporarily use the user's uid. */
 	temporarily_use_uid(pw->pw_uid);

 	/* The authorized keys. */
 	snprintf(file, sizeof file, "%.500s/%.100s", pw->pw_dir,
 	    _PATH_SSH_USER_PERMITTED_KEYS2);

 	/* Fail quietly if file does not exist */
 	if (stat(file, &st) < 0) {
 		/* Restore the privileged uid. */
 		restore_uid();
 		return 0;
 	}
 	/* Open the file containing the authorized keys. */
 	f = fopen(file, "r");
 	if (!f) {
 		/* Restore the privileged uid. */
 		restore_uid();
 		return 0;
 	}
 	if (options.strict_modes) {
 		int fail = 0;
 		char buf[1024];
 		/* Check open file in order to avoid open/stat races */
 		if (fstat(fileno(f), &st) < 0 ||
 		    (st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
 		    (st.st_mode & 022) != 0) {
 			snprintf(buf, sizeof buf,
 			    "%s authentication refused for %.100s: "
 			    "bad ownership or modes for '%s'.",
 			    key_type(key), pw->pw_name, file);
 			fail = 1;
 		} else {
 			/* Check path to _PATH_SSH_USER_PERMITTED_KEYS */
 			int i;
 			static const char *check[] = {
 				"", _PATH_SSH_USER_DIR, NULL
 			};
 			for (i = 0; check[i]; i++) {
 				snprintf(line, sizeof line, "%.500s/%.100s",
 				    pw->pw_dir, check[i]);
 				if (stat(line, &st) < 0 ||
 				    (st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
 				    (st.st_mode & 022) != 0) {
 					snprintf(buf, sizeof buf,
 					    "%s authentication refused for %.100s: "
 					    "bad ownership or modes for '%s'.",
 					    key_type(key), pw->pw_name, line);
 					fail = 1;
 					break;
 				}
 			}
 		}
 		if (fail) {
 			fclose(f);
 			log("%s", buf);
 			restore_uid();
 			return 0;
 		}
 	}
 	found_key = 0;
 	found = key_new(key->type);

 	while (fgets(line, sizeof(line), f)) {
 		char *cp, *options = NULL;
 		linenum++;
 		/* Skip leading whitespace, empty and comment lines. */
 		for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
 			;
 		if (!*cp || *cp == '\n' || *cp == '#')
 			continue;

 		if (key_read(found, &cp) == -1) {
 			/* no key?  check if there are options for this key */
 			int quoted = 0;
 			debug2("user_key_allowed: check options: '%s'", cp);
 			options = cp;
 			for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
 				if (*cp == '\\' && cp[1] == '"')
 					cp++;	/* Skip both */
 				else if (*cp == '"')
 					quoted = !quoted;
 			}
 			/* Skip remaining whitespace. */
 			for (; *cp == ' ' || *cp == '\t'; cp++)
 				;
 			if (key_read(found, &cp) == -1) {
 				debug2("user_key_allowed: advance: '%s'", cp);
 				/* still no key?  advance to next line*/
 				continue;
 			}
 		}
 		if (key_equal(found, key) &&
 		    auth_parse_options(pw, options, file, linenum) == 1) {
 			found_key = 1;
 			debug("matching key found: file %s, line %ld",
 			    file, linenum);
 			break;
 		}
 	}
 	restore_uid();
 	fclose(f);
 	key_free(found);
 	return found_key;
 }
	/*
	* 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 1.45 2001/03/04 01:46:29 djm Exp $");

	#include <openssl/evp.h>

	#include "ssh2.h"
	#include "xmalloc.h"
	#include "rsa.h"
	#include "sshpty.h"
	#include "packet.h"
	#include "buffer.h"
	#include "log.h"
	#include "servconf.h"
	#include "compat.h"
	#include "channels.h"
	#include "bufaux.h"
	#include "auth.h"
	#include "session.h"
	#include "dispatch.h"
	#include "key.h"
	#include "cipher.h"
	#include "kex.h"
	#include "pathnames.h"
	#include "uidswap.h"
	#include "auth-options.h"
	#include "misc.h"

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

	#ifdef WITH_AIXAUTHENTICATE
	extern char *aixloginmsg;
	#endif

	static Authctxt *x_authctxt = NULL;
	static int one = 1;

	typedef struct Authmethod Authmethod;
	struct Authmethod {
	char *name;
	int (userauth)(Authctxt authctxt);
	int *enabled;
	};

	/* protocol */

	void input_service_request(int type, int plen, void *ctxt);
	void input_userauth_request(int type, int plen, void *ctxt);
	void protocol_error(int type, int plen, void *ctxt);

	/* helper */
	Authmethod authmethod_lookup(const char name);
	int user_key_allowed(struct passwd pw, Key key);
	char *authmethods_get(void);

	/* auth */
	void userauth_banner(void);
	int userauth_none(Authctxt *authctxt);
	int userauth_passwd(Authctxt *authctxt);
	int userauth_pubkey(Authctxt *authctxt);
	int userauth_kbdint(Authctxt *authctxt);

	Authmethod authmethods[] = {
	{"none",
	userauth_none,
	&one},
	{"publickey",
	userauth_pubkey,
	&options.pubkey_authentication},
	{"password",
	userauth_passwd,
	&options.password_authentication},
	{"keyboard-interactive",
	userauth_kbdint,
	&options.kbd_interactive_authentication},
	{NULL, NULL, NULL}
	};

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

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

	x_authctxt = authctxt; /XXX/

	/* challenge-reponse is implemented via keyboard interactive */
	if (options.challenge_reponse_authentication)
	options.kbd_interactive_authentication = 1;

	dispatch_init(&protocol_error);
	dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
	dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);
	do_authenticated2(authctxt);
	}

	void
	protocol_error(int type, int plen, void *ctxt)
	{
	log("auth: protocol error: type %d plen %d", type, plen);
	packet_start(SSH2_MSG_UNIMPLEMENTED);
	packet_put_int(0);
	packet_send();
	packet_write_wait();
	}

	void
	input_service_request(int type, int plen, void *ctxt)
	{
	Authctxt *authctxt = ctxt;
	u_int len;
	int accept = 0;
	char *service = packet_get_string(&len);
	packet_done();

	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);
	}

	void
	input_userauth_request(int type, int plen, 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 */
	struct passwd *pw = NULL;
	pw = getpwnam(user);
	if (pw && allowed_user(pw) && strcmp(service, "ssh-connection")==0) {
	authctxt->pw = pwcopy(pw);
	authctxt->valid = 1;
	debug2("input_userauth_request: setting up authctxt for %s", user);
	#ifdef USE_PAM
	start_pam(pw->pw_name);
	#endif
	} else {
	log("input_userauth_request: illegal user %s", user);
	#ifdef USE_PAM
	start_pam("NOUSER");
	#endif
	}
	setproctitle("%s", pw ? user : "unknown");
	authctxt->user = xstrdup(user);
	authctxt->service = xstrdup(service);
	authctxt->style = style ? xstrdup(style) : NULL; /* currently unused */
	} else if (authctxt->valid) {
	if (strcmp(user, authctxt->user) != 0 \|\|
	strcmp(service, authctxt->service) != 0) {
	log("input_userauth_request: missmatch: (%s,%s)!=(%s,%s)",
	user, service, authctxt->user, authctxt->service);
	authctxt->valid = 0;
	}
	}
	/* reset state */
	dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, &protocol_error);
	authctxt->postponed = 0;
	#ifdef BSD_AUTH
	if (authctxt->as) {
	auth_close(authctxt->as);
	authctxt->as = NULL;
	}
	#endif

	/* try to authenticate user */
	m = authmethod_lookup(method);
	if (m != NULL) {
	debug2("input_userauth_request: try method %s", method);
	authenticated = m->userauth(authctxt);
	}
	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 (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)
	userauth_reply(authctxt, authenticated);

	xfree(service);
	xfree(user);
	xfree(method);
	}

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

	if (options.banner == NULL \|\| (datafellows & SSH_BUG_BANNER))
	return;
	if ((fd = open(options.banner, O_RDONLY)) < 0) {
	error("userauth_banner: open %s failed: %s",
	options.banner, strerror(errno));
	return;
	}
	if (fstat(fd, &st) < 0)
	goto done;
	len = st.st_size;
	banner = xmalloc(len + 1);
	if ((n = read(fd, banner, len)) < 0)
	goto done;
	banner[n] = '\0';
	packet_start(SSH2_MSG_USERAUTH_BANNER);
	packet_put_cstring(banner);
	packet_put_cstring(""); /* language, unused */
	packet_send();
	debug("userauth_banner: sent");
	done:
	if (banner)
	xfree(banner);
	close(fd);
	return;
	}

	void
	userauth_reply(Authctxt *authctxt, int authenticated)
	{
	char *methods;

	/* XXX todo: check if multiple auth methods are needed */
	if (authenticated == 1) {
	#ifdef WITH_AIXAUTHENTICATE
	/* We don't have a pty yet, so just label the line as "ssh" */
	if (loginsuccess(authctxt->user?authctxt->user:"NOUSER",
	get_canonical_hostname(options.reverse_mapping_check),
	"ssh", &aixloginmsg) < 0)
	aixloginmsg = NULL;
	#endif /* WITH_AIXAUTHENTICATE */
	/* turn off userauth */
	dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &protocol_error);
	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)
	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);
	}
	}

	int
	userauth_none(Authctxt *authctxt)
	{
	/* disable method "none", only allowed one time */
	Authmethod *m = authmethod_lookup("none");
	if (m != NULL)
	m->enabled = NULL;
	packet_done();
	userauth_banner();

	if (authctxt->valid == 0)
	return(0);

	#ifdef HAVE_CYGWIN
	if (check_nt_auth(1, authctxt->pw->pw_uid) == 0)
	return(0);
	#endif
	#ifdef USE_PAM
	return auth_pam_password(authctxt->pw, "");
	#elif defined(HAVE_OSF_SIA)
	return 0;
	#else /* !HAVE_OSF_SIA && !USE_PAM */
	return auth_password(authctxt, "");
	#endif /* USE_PAM */
	}

	int
	userauth_passwd(Authctxt *authctxt)
	{
	char *password;
	int authenticated = 0;
	int change;
	u_int len;
	change = packet_get_char();
	if (change)
	log("password change not supported");
	password = packet_get_string(&len);
	packet_done();
	if (authctxt->valid &&
	#ifdef HAVE_CYGWIN
	check_nt_auth(1, authctxt->pw->pw_uid) &&
	#endif
	#ifdef USE_PAM
	auth_pam_password(authctxt->pw, password) == 1)
	#elif defined(HAVE_OSF_SIA)
	auth_sia_password(authctxt->user, password) == 1)
	#else /* !USE_PAM && !HAVE_OSF_SIA */
	auth_password(authctxt, password) == 1)
	#endif /* USE_PAM */
	authenticated = 1;
	memset(password, 0, len);
	xfree(password);
	return authenticated;
	}

	int
	userauth_kbdint(Authctxt *authctxt)
	{
	int authenticated = 0;
	char *lang = NULL;
	char *devs = NULL;

	lang = packet_get_string(NULL);
	devs = packet_get_string(NULL);
	packet_done();

	debug("keyboard-interactive language %s devs %s", lang, devs);

	if (options.challenge_reponse_authentication)
	authenticated = auth2_challenge(authctxt, devs);

	#ifdef USE_PAM
	if (authenticated == 0)
	authenticated = auth2_pam(authctxt);
	#endif
	xfree(lang);
	xfree(devs);
	#ifdef HAVE_CYGWIN
	if (check_nt_auth(0, authctxt->pw->pw_uid) == 0)
	return(0);
	#endif
	return authenticated;
	}

	int
	userauth_pubkey(Authctxt *authctxt)
	{
	Buffer b;
	Key *key;
	char pkalg, pkblob, *sig;
	u_int alen, blen, slen;
	int have_sig, pktype;
	int authenticated = 0;

	if (!authctxt->valid) {
	debug2("userauth_pubkey: disabled because of invalid user");
	return 0;
	}
	have_sig = packet_get_char();
	if (datafellows & SSH_BUG_PKAUTH) {
	debug2("userauth_pubkey: SSH_BUG_PKAUTH");
	/* no explicit pkalg given */
	pkblob = packet_get_string(&blen);
	buffer_init(&b);
	buffer_append(&b, pkblob, blen);
	/* so we have to extract the pkalg from the pkblob */
	pkalg = buffer_get_string(&b, &alen);
	buffer_free(&b);
	} else {
	pkalg = packet_get_string(&alen);
	pkblob = packet_get_string(&blen);
	}
	pktype = key_type_from_name(pkalg);
	if (pktype == KEY_UNSPEC) {
	/* this is perfectly legal */
	log("userauth_pubkey: unsupported public key algorithm: %s", pkalg);
	xfree(pkalg);
	xfree(pkblob);
	return 0;
	}
	key = key_from_blob(pkblob, blen);
	if (key != NULL) {
	if (have_sig) {
	sig = packet_get_string(&slen);
	packet_done();
	buffer_init(&b);
	if (datafellows & SSH_OLD_SESSIONID) {
	buffer_append(&b, session_id2, session_id2_len);
	} else {
	buffer_put_string(&b, session_id2, session_id2_len);
	}
	/* reconstruct packet */
	buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
	buffer_put_cstring(&b, authctxt->user);
	buffer_put_cstring(&b,
	datafellows & SSH_BUG_PKSERVICE ?
	"ssh-userauth" :
	authctxt->service);
	if (datafellows & SSH_BUG_PKAUTH) {
	buffer_put_char(&b, have_sig);
	} else {
	buffer_put_cstring(&b, "publickey");
	buffer_put_char(&b, have_sig);
	buffer_put_cstring(&b, key_ssh_name(key));
	}
	buffer_put_string(&b, pkblob, blen);
	#ifdef DEBUG_PK
	buffer_dump(&b);
	#endif
	/* test for correct signature */
	if (user_key_allowed(authctxt->pw, key) &&
	key_verify(key, sig, slen, buffer_ptr(&b), buffer_len(&b)) == 1)
	authenticated = 1;
	buffer_clear(&b);
	xfree(sig);
	} else {
	debug("test whether pkalg/pkblob are acceptable");
	packet_done();

	/* XXX fake reply and always send PK_OK ? */
	/*
	* XXX this allows testing whether a user is allowed
	* to login: if you happen to have a valid pubkey this
	* message is sent. the message is NEVER sent at all
	* if a user is not allowed to login. is this an
	* issue? -markus
	*/
	if (user_key_allowed(authctxt->pw, key)) {
	packet_start(SSH2_MSG_USERAUTH_PK_OK);
	packet_put_string(pkalg, alen);
	packet_put_string(pkblob, blen);
	packet_send();
	packet_write_wait();
	authctxt->postponed = 1;
	}
	}
	if (authenticated != 1)
	auth_clear_options();
	key_free(key);
	}
	debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
	xfree(pkalg);
	xfree(pkblob);
	#ifdef HAVE_CYGWIN
	if (check_nt_auth(0, authctxt->pw->pw_uid) == 0)
	return(0);
	#endif
	return authenticated;
	}

	/* get current user */

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

	#define DELIM ","

	char *
	authmethods_get(void)
	{
	Authmethod *method = NULL;
	u_int size = 0;
	char *list;

	for (method = authmethods; method->name != NULL; method++) {
	if (strcmp(method->name, "none") == 0)
	continue;
	if (method->enabled != NULL && *(method->enabled) != 0) {
	if (size != 0)
	size += strlen(DELIM);
	size += strlen(method->name);
	}
	}
	size++; /* trailing '\0' */
	list = xmalloc(size);
	list[0] = '\0';

	for (method = authmethods; method->name != NULL; method++) {
	if (strcmp(method->name, "none") == 0)
	continue;
	if (method->enabled != NULL && *(method->enabled) != 0) {
	if (list[0] != '\0')
	strlcat(list, DELIM, size);
	strlcat(list, method->name, size);
	}
	}
	return list;
	}

	Authmethod *
	authmethod_lookup(const char *name)
	{
	Authmethod *method = NULL;
	if (name != NULL)
	for (method = authmethods; method->name != NULL; method++)
	if (method->enabled != NULL &&
	*(method->enabled) != 0 &&
	strcmp(name, method->name) == 0)
	return method;
	debug2("Unrecognized authentication method name: %s", name ? name : "NULL");
	return NULL;
	}

	/* return 1 if user allows given key */
	int
	user_key_allowed(struct passwd pw, Key key)
	{
	char line[8192], file[MAXPATHLEN];
	int found_key = 0;
	FILE *f;
	u_long linenum = 0;
	struct stat st;
	Key *found;

	if (pw == NULL)
	return 0;

	/* Temporarily use the user's uid. */
	temporarily_use_uid(pw->pw_uid);

	/* The authorized keys. */
	snprintf(file, sizeof file, "%.500s/%.100s", pw->pw_dir,
	_PATH_SSH_USER_PERMITTED_KEYS2);

	/* Fail quietly if file does not exist */
	if (stat(file, &st) < 0) {
	/* Restore the privileged uid. */
	restore_uid();
	return 0;
	}
	/* Open the file containing the authorized keys. */
	f = fopen(file, "r");
	if (!f) {
	/* Restore the privileged uid. */
	restore_uid();
	return 0;
	}
	if (options.strict_modes) {
	int fail = 0;
	char buf[1024];
	/* Check open file in order to avoid open/stat races */
	if (fstat(fileno(f), &st) < 0 \|\|
	(st.st_uid != 0 && st.st_uid != pw->pw_uid) \|\|
	(st.st_mode & 022) != 0) {
	snprintf(buf, sizeof buf,
	"%s authentication refused for %.100s: "
	"bad ownership or modes for '%s'.",
	key_type(key), pw->pw_name, file);
	fail = 1;
	} else {
	/* Check path to _PATH_SSH_USER_PERMITTED_KEYS */
	int i;
	static const char *check[] = {
	"", _PATH_SSH_USER_DIR, NULL
	};
	for (i = 0; check[i]; i++) {
	snprintf(line, sizeof line, "%.500s/%.100s",
	pw->pw_dir, check[i]);
	if (stat(line, &st) < 0 \|\|
	(st.st_uid != 0 && st.st_uid != pw->pw_uid) \|\|
	(st.st_mode & 022) != 0) {
	snprintf(buf, sizeof buf,
	"%s authentication refused for %.100s: "
	"bad ownership or modes for '%s'.",
	key_type(key), pw->pw_name, line);
	fail = 1;
	break;
	}
	}
	}
	if (fail) {
	fclose(f);
	log("%s", buf);
	restore_uid();
	return 0;
	}
	}
	found_key = 0;
	found = key_new(key->type);

	while (fgets(line, sizeof(line), f)) {
	char cp, options = NULL;
	linenum++;
	/* Skip leading whitespace, empty and comment lines. */
	for (cp = line; cp == ' ' \|\| cp == '\t'; cp++)
	;
	if (!cp \|\| cp == '\n' \|\| *cp == '#')
	continue;

	if (key_read(found, &cp) == -1) {
	/* no key? check if there are options for this key */
	int quoted = 0;
	debug2("user_key_allowed: check options: '%s'", cp);
	options = cp;
	for (; cp && (quoted \|\| (cp != ' ' && *cp != '\t')); cp++) {
	if (*cp == '\\' && cp[1] == '"')
	cp++; /* Skip both */
	else if (*cp == '"')
	quoted = !quoted;
	}
	/* Skip remaining whitespace. */
	for (; cp == ' ' \|\| cp == '\t'; cp++)
	;
	if (key_read(found, &cp) == -1) {
	debug2("user_key_allowed: advance: '%s'", cp);
	/* still no key? advance to next line*/
	continue;
	}
	}
	if (key_equal(found, key) &&
	auth_parse_options(pw, options, file, linenum) == 1) {
	found_key = 1;
	debug("matching key found: file %s, line %ld",
	file, linenum);
	break;
	}
	}
	restore_uid();
	fclose(f);
	key_free(found);
	return found_key;
	}