sshconnect2.c

OpenSSH 是 SSH （Secure SHell） 协议的免费开源实现。它用安全、加密的网络连接工具代替了 telnet、ftp、 rlogin、rsh 和 rcp 工具。OpenSSH 支持

	}
	return private;
}

/*
 * try keys in the following order:
 *	1. agent keys that are found in the config file
 *	2. other agent keys
 *	3. keys that are only listed in the config file
 */
static void
pubkey_prepare(Authctxt *authctxt)
{
	Identity *id;
	Idlist agent, files, *preferred;
	Key *key;
	AuthenticationConnection *ac;
	char *comment;
	int i, found;

	TAILQ_INIT(&agent);	/* keys from the agent */
	TAILQ_INIT(&files);	/* keys from the config file */
	preferred = &authctxt->keys;
	TAILQ_INIT(preferred);	/* preferred order of keys */

	/* list of keys stored in the filesystem */
	for (i = 0; i < options.num_identity_files; i++) {
		key = options.identity_keys[i];
		if (key && key->type == KEY_RSA1)
			continue;
		options.identity_keys[i] = NULL;
		id = xmalloc(sizeof(*id));
		memset(id, 0, sizeof(*id));
		id->key = key;
		id->filename = xstrdup(options.identity_files[i]);
		TAILQ_INSERT_TAIL(&files, id, next);
	}
	/* list of keys supported by the agent */
	if ((ac = ssh_get_authentication_connection())) {
		for (key = ssh_get_first_identity(ac, &comment, 2);
		    key != NULL;
		    key = ssh_get_next_identity(ac, &comment, 2)) {
			found = 0;
			TAILQ_FOREACH(id, &files, next) {
				/* agent keys from the config file are preferred */
				if (key_equal(key, id->key)) {
					key_free(key);
					xfree(comment);
					TAILQ_REMOVE(&files, id, next);
					TAILQ_INSERT_TAIL(preferred, id, next);
					id->ac = ac;
					found = 1;
					break;
				}
			}
			if (!found && !options.identities_only) {
				id = xmalloc(sizeof(*id));
				memset(id, 0, sizeof(*id));
				id->key = key;
				id->filename = comment;
				id->ac = ac;
				TAILQ_INSERT_TAIL(&agent, id, next);
			}
		}
		/* append remaining agent keys */
		for (id = TAILQ_FIRST(&agent); id; id = TAILQ_FIRST(&agent)) {
			TAILQ_REMOVE(&agent, id, next);
			TAILQ_INSERT_TAIL(preferred, id, next);
		}
		authctxt->agent = ac;
	}
	/* append remaining keys from the config file */
	for (id = TAILQ_FIRST(&files); id; id = TAILQ_FIRST(&files)) {
		TAILQ_REMOVE(&files, id, next);
		TAILQ_INSERT_TAIL(preferred, id, next);
	}
	TAILQ_FOREACH(id, preferred, next) {
		debug2("key: %s (%p)", id->filename, id->key);
	}
}

static void
pubkey_cleanup(Authctxt *authctxt)
{
	Identity *id;

	if (authctxt->agent != NULL)
		ssh_close_authentication_connection(authctxt->agent);
	for (id = TAILQ_FIRST(&authctxt->keys); id;
	    id = TAILQ_FIRST(&authctxt->keys)) {
		TAILQ_REMOVE(&authctxt->keys, id, next);
		if (id->key)
			key_free(id->key);
		if (id->filename)
			xfree(id->filename);
		xfree(id);
	}
}

int
userauth_pubkey(Authctxt *authctxt)
{
	Identity *id;
	int sent = 0;

	while ((id = TAILQ_FIRST(&authctxt->keys))) {
		if (id->tried++)
			return (0);
		/* move key to the end of the queue */
		TAILQ_REMOVE(&authctxt->keys, id, next);
		TAILQ_INSERT_TAIL(&authctxt->keys, id, next);
		/*
		 * send a test message if we have the public key. for
		 * encrypted keys we cannot do this and have to load the
		 * private key instead
		 */
		if (id->key && id->key->type != KEY_RSA1) {
			debug("Offering public key: %s", id->filename);
			sent = send_pubkey_test(authctxt, id);
		} else if (id->key == NULL) {
			debug("Trying private key: %s", id->filename);
			id->key = load_identity_file(id->filename);
			if (id->key != NULL) {
				id->isprivate = 1;
				sent = sign_and_send_pubkey(authctxt, id);
				key_free(id->key);
				id->key = NULL;
			}
		}
		if (sent)
			return (sent);
	}
	return (0);
}

/*
 * Send userauth request message specifying keyboard-interactive method.
 */
int
userauth_kbdint(Authctxt *authctxt)
{
	static int attempt = 0;

	if (attempt++ >= options.number_of_password_prompts)
		return 0;
	/* disable if no SSH2_MSG_USERAUTH_INFO_REQUEST has been seen */
	if (attempt > 1 && !authctxt->info_req_seen) {
		debug3("userauth_kbdint: disable: no info_req_seen");
		dispatch_set(SSH2_MSG_USERAUTH_INFO_REQUEST, NULL);
		return 0;
	}

	debug2("userauth_kbdint");
	packet_start(SSH2_MSG_USERAUTH_REQUEST);
	packet_put_cstring(authctxt->server_user);
	packet_put_cstring(authctxt->service);
	packet_put_cstring(authctxt->method->name);
	packet_put_cstring("");					/* lang */
	packet_put_cstring(options.kbd_interactive_devices ?
	    options.kbd_interactive_devices : "");
	packet_send();

	dispatch_set(SSH2_MSG_USERAUTH_INFO_REQUEST, &input_userauth_info_req);
	return 1;
}

/*
 * parse INFO_REQUEST, prompt user and send INFO_RESPONSE
 */
void
input_userauth_info_req(int type, u_int32_t seq, void *ctxt)
{
	Authctxt *authctxt = ctxt;
	char *name, *inst, *lang, *prompt, *response;
	u_int num_prompts, i;
	int echo = 0;

	debug2("input_userauth_info_req");

	if (authctxt == NULL)
		fatal("input_userauth_info_req: no authentication context");

	authctxt->info_req_seen = 1;

	name = packet_get_string(NULL);
	inst = packet_get_string(NULL);
	lang = packet_get_string(NULL);
	if (strlen(name) > 0)
		logit("%s", name);
	if (strlen(inst) > 0)
		logit("%s", inst);
	xfree(name);
	xfree(inst);
	xfree(lang);

	num_prompts = packet_get_int();
	/*
	 * Begin to build info response packet based on prompts requested.
	 * We commit to providing the correct number of responses, so if
	 * further on we run into a problem that prevents this, we have to
	 * be sure and clean this up and send a correct error response.
	 */
	packet_start(SSH2_MSG_USERAUTH_INFO_RESPONSE);
	packet_put_int(num_prompts);

	debug2("input_userauth_info_req: num_prompts %d", num_prompts);
	for (i = 0; i < num_prompts; i++) {
		prompt = packet_get_string(NULL);
		echo = packet_get_char();

		response = read_passphrase(prompt, echo ? RP_ECHO : 0);

		packet_put_cstring(response);
		memset(response, 0, strlen(response));
		xfree(response);
		xfree(prompt);
	}
	packet_check_eom(); /* done with parsing incoming message. */

	packet_add_padding(64);
	packet_send();
}

static int
ssh_keysign(Key *key, u_char **sigp, u_int *lenp,
    u_char *data, u_int datalen)
{
	Buffer b;
	struct stat st;
	pid_t pid;
	int to[2], from[2], status, version = 2;

	debug2("ssh_keysign called");

	if (stat(_PATH_SSH_KEY_SIGN, &st) < 0) {
		error("ssh_keysign: no installed: %s", strerror(errno));
		return -1;
	}
	if (fflush(stdout) != 0)
		error("ssh_keysign: fflush: %s", strerror(errno));
	if (pipe(to) < 0) {
		error("ssh_keysign: pipe: %s", strerror(errno));
		return -1;
	}
	if (pipe(from) < 0) {
		error("ssh_keysign: pipe: %s", strerror(errno));
		return -1;
	}
	if ((pid = fork()) < 0) {
		error("ssh_keysign: fork: %s", strerror(errno));
		return -1;
	}
	if (pid == 0) {
		seteuid(getuid());
		setuid(getuid());
		close(from[0]);
		if (dup2(from[1], STDOUT_FILENO) < 0)
			fatal("ssh_keysign: dup2: %s", strerror(errno));
		close(to[1]);
		if (dup2(to[0], STDIN_FILENO) < 0)
			fatal("ssh_keysign: dup2: %s", strerror(errno));
		close(from[1]);
		close(to[0]);
		execl(_PATH_SSH_KEY_SIGN, _PATH_SSH_KEY_SIGN, (char *) 0);
		fatal("ssh_keysign: exec(%s): %s", _PATH_SSH_KEY_SIGN,
		    strerror(errno));
	}
	close(from[1]);
	close(to[0]);

	buffer_init(&b);
	buffer_put_int(&b, packet_get_connection_in()); /* send # of socket */
	buffer_put_string(&b, data, datalen);
	if (ssh_msg_send(to[1], version, &b) == -1)
		fatal("ssh_keysign: couldn't send request");

	if (ssh_msg_recv(from[0], &b) < 0) {
		error("ssh_keysign: no reply");
		buffer_free(&b);
		return -1;
	}
	close(from[0]);
	close(to[1]);

	while (waitpid(pid, &status, 0) < 0)
		if (errno != EINTR)
			break;

	if (buffer_get_char(&b) != version) {
		error("ssh_keysign: bad version");
		buffer_free(&b);
		return -1;
	}
	*sigp = buffer_get_string(&b, lenp);
	buffer_free(&b);

	return 0;
}

int
userauth_hostbased(Authctxt *authctxt)
{
	Key *private = NULL;
	Sensitive *sensitive = authctxt->sensitive;
	Buffer b;
	u_char *signature, *blob;
	char *chost, *pkalg, *p;
	const char *service;
	u_int blen, slen;
	int ok, i, len, found = 0;

	/* check for a useful key */
	for (i = 0; i < sensitive->nkeys; i++) {
		private = sensitive->keys[i];
		if (private && private->type != KEY_RSA1) {
			found = 1;
			/* we take and free the key */
			sensitive->keys[i] = NULL;
			break;
		}
	}
	if (!found) {
		debug("No more client hostkeys for hostbased authentication.");
		return 0;
	}
	if (key_to_blob(private, &blob, &blen) == 0) {
		key_free(private);
		return 0;
	}
	/* figure out a name for the client host */
	p = get_local_name(packet_get_connection_in());
	if (p == NULL) {
		error("userauth_hostbased: cannot get local ipaddr/name");
		key_free(private);
		return 0;
	}
	len = strlen(p) + 2;
	chost = xmalloc(len);
	strlcpy(chost, p, len);
	strlcat(chost, ".", len);
	debug2("userauth_hostbased: chost %s", chost);
	xfree(p);

	service = datafellows & SSH_BUG_HBSERVICE ? "ssh-userauth" :
	    authctxt->service;
	pkalg = xstrdup(key_ssh_name(private));
	buffer_init(&b);
	/* construct data */
	buffer_put_string(&b, session_id2, session_id2_len);
	buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
	buffer_put_cstring(&b, authctxt->server_user);
	buffer_put_cstring(&b, service);
	buffer_put_cstring(&b, authctxt->method->name);
	buffer_put_cstring(&b, pkalg);
	buffer_put_string(&b, blob, blen);
	buffer_put_cstring(&b, chost);
	buffer_put_cstring(&b, authctxt->local_user);
#ifdef DEBUG_PK
	buffer_dump(&b);
#endif
	if (sensitive->external_keysign)
		ok = ssh_keysign(private, &signature, &slen,
		    buffer_ptr(&b), buffer_len(&b));
	else
		ok = key_sign(private, &signature, &slen,
		    buffer_ptr(&b), buffer_len(&b));
	key_free(private);
	buffer_free(&b);
	if (ok != 0) {
		error("key_sign failed");
		xfree(chost);
		xfree(pkalg);
		return 0;
	}
	packet_start(SSH2_MSG_USERAUTH_REQUEST);
	packet_put_cstring(authctxt->server_user);
	packet_put_cstring(authctxt->service);
	packet_put_cstring(authctxt->method->name);
	packet_put_cstring(pkalg);
	packet_put_string(blob, blen);
	packet_put_cstring(chost);
	packet_put_cstring(authctxt->local_user);
	packet_put_string(signature, slen);
	memset(signature, 's', slen);
	xfree(signature);
	xfree(chost);
	xfree(pkalg);

	packet_send();
	return 1;
}

/* find auth method */

/*
 * given auth method name, if configurable options permit this method fill
 * in auth_ident field and return true, otherwise return false.
 */
static int
authmethod_is_enabled(Authmethod *method)
{
	if (method == NULL)
		return 0;
	/* return false if options indicate this method is disabled */
	if  (method->enabled == NULL || *method->enabled == 0)
		return 0;
	/* return false if batch mode is enabled but method needs interactive mode */
	if  (method->batch_flag != NULL && *method->batch_flag != 0)
		return 0;
	return 1;
}

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

/* XXX internal state */
static Authmethod *current = NULL;
static char *supported = NULL;
static char *preferred = NULL;

/*
 * Given the authentication method list sent by the server, return the
 * next method we should try.  If the server initially sends a nil list,
 * use a built-in default list.
 */
static Authmethod *
authmethod_get(char *authlist)
{
	char *name = NULL;
	u_int next;

	/* Use a suitable default if we're passed a nil list.  */
	if (authlist == NULL || strlen(authlist) == 0)
		authlist = options.preferred_authentications;

	if (supported == NULL || strcmp(authlist, supported) != 0) {
		debug3("start over, passed a different list %s", authlist);
		if (supported != NULL)
			xfree(supported);
		supported = xstrdup(authlist);
		preferred = options.preferred_authentications;
		debug3("preferred %s", preferred);
		current = NULL;
	} else if (current != NULL && authmethod_is_enabled(current))
		return current;

	for (;;) {
		if ((name = match_list(preferred, supported, &next)) == NULL) {
			debug("No more authentication methods to try.");
			current = NULL;
			return NULL;
		}
		preferred += next;
		debug3("authmethod_lookup %s", name);
		debug3("remaining preferred: %s", preferred);
		if ((current = authmethod_lookup(name)) != NULL &&
		    authmethod_is_enabled(current)) {
			debug3("authmethod_is_enabled %s", name);
			debug("Next authentication method: %s", name);
			return current;
		}
	}
}

static char *
authmethods_get(void)
{
	Authmethod *method = NULL;
	Buffer b;
	char *list;

	buffer_init(&b);
	for (method = authmethods; method->name != NULL; method++) {
		if (authmethod_is_enabled(method)) {
			if (buffer_len(&b) > 0)
				buffer_append(&b, ",", 1);
			buffer_append(&b, method->name, strlen(method->name));
		}
	}
	buffer_append(&b, "\0", 1);
	list = xstrdup(buffer_ptr(&b));
	buffer_free(&b);
	return list;
}