ssh-agent.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

			id->confirm = confirm;
			TAILQ_INSERT_TAIL(&tab->idlist, id, next);
			tab->nentries++;
			success = 1;
		} else {
			key_free(k);
		}
		keys[i] = NULL;
	}
	xfree(keys);
send:
	buffer_put_int(&e->output, 1);
	buffer_put_char(&e->output,
	    success ? SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE);
}

static void
process_remove_smartcard_key(SocketEntry *e)
{
	char *sc_reader_id = NULL, *pin;
	int i, version, success = 0;
	Key **keys, *k = NULL;
	Identity *id;
	Idtab *tab;

	sc_reader_id = buffer_get_string(&e->request, NULL);
	pin = buffer_get_string(&e->request, NULL);
	keys = sc_get_keys(sc_reader_id, pin);
	xfree(sc_reader_id);
	xfree(pin);

	if (keys == NULL || keys[0] == NULL) {
		error("sc_get_keys failed");
		goto send;
	}
	for (i = 0; keys[i] != NULL; i++) {
		k = keys[i];
		version = k->type == KEY_RSA1 ? 1 : 2;
		if ((id = lookup_identity(k, version)) != NULL) {
			tab = idtab_lookup(version);
			TAILQ_REMOVE(&tab->idlist, id, next);
			tab->nentries--;
			free_identity(id);
			success = 1;
		}
		key_free(k);
		keys[i] = NULL;
	}
	xfree(keys);
send:
	buffer_put_int(&e->output, 1);
	buffer_put_char(&e->output,
	    success ? SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE);
}
#endif /* SMARTCARD */

/* dispatch incoming messages */

static void
process_message(SocketEntry *e)
{
	u_int msg_len, type;
	u_char *cp;

	/* kill dead keys */
	reaper();

	if (buffer_len(&e->input) < 5)
		return;		/* Incomplete message. */
	cp = buffer_ptr(&e->input);
	msg_len = GET_32BIT(cp);
	if (msg_len > 256 * 1024) {
		close_socket(e);
		return;
	}
	if (buffer_len(&e->input) < msg_len + 4)
		return;

	/* move the current input to e->request */
	buffer_consume(&e->input, 4);
	buffer_clear(&e->request);
	buffer_append(&e->request, buffer_ptr(&e->input), msg_len);
	buffer_consume(&e->input, msg_len);
	type = buffer_get_char(&e->request);

	/* check wheter agent is locked */
	if (locked && type != SSH_AGENTC_UNLOCK) {
		buffer_clear(&e->request);
		switch (type) {
		case SSH_AGENTC_REQUEST_RSA_IDENTITIES:
		case SSH2_AGENTC_REQUEST_IDENTITIES:
			/* send empty lists */
			no_identities(e, type);
			break;
		default:
			/* send a fail message for all other request types */
			buffer_put_int(&e->output, 1);
			buffer_put_char(&e->output, SSH_AGENT_FAILURE);
		}
		return;
	}

	debug("type %d", type);
	switch (type) {
	case SSH_AGENTC_LOCK:
	case SSH_AGENTC_UNLOCK:
		process_lock_agent(e, type == SSH_AGENTC_LOCK);
		break;
	/* ssh1 */
	case SSH_AGENTC_RSA_CHALLENGE:
		process_authentication_challenge1(e);
		break;
	case SSH_AGENTC_REQUEST_RSA_IDENTITIES:
		process_request_identities(e, 1);
		break;
	case SSH_AGENTC_ADD_RSA_IDENTITY:
	case SSH_AGENTC_ADD_RSA_ID_CONSTRAINED:
		process_add_identity(e, 1);
		break;
	case SSH_AGENTC_REMOVE_RSA_IDENTITY:
		process_remove_identity(e, 1);
		break;
	case SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES:
		process_remove_all_identities(e, 1);
		break;
	/* ssh2 */
	case SSH2_AGENTC_SIGN_REQUEST:
		process_sign_request2(e);
		break;
	case SSH2_AGENTC_REQUEST_IDENTITIES:
		process_request_identities(e, 2);
		break;
	case SSH2_AGENTC_ADD_IDENTITY:
	case SSH2_AGENTC_ADD_ID_CONSTRAINED:
		process_add_identity(e, 2);
		break;
	case SSH2_AGENTC_REMOVE_IDENTITY:
		process_remove_identity(e, 2);
		break;
	case SSH2_AGENTC_REMOVE_ALL_IDENTITIES:
		process_remove_all_identities(e, 2);
		break;
#ifdef SMARTCARD
	case SSH_AGENTC_ADD_SMARTCARD_KEY:
	case SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED:
		process_add_smartcard_key(e);
		break;
	case SSH_AGENTC_REMOVE_SMARTCARD_KEY:
		process_remove_smartcard_key(e);
		break;
#endif /* SMARTCARD */
	default:
		/* Unknown message.  Respond with failure. */
		error("Unknown message %d", type);
		buffer_clear(&e->request);
		buffer_put_int(&e->output, 1);
		buffer_put_char(&e->output, SSH_AGENT_FAILURE);
		break;
	}
}

static void
new_socket(sock_type type, int fd)
{
	u_int i, old_alloc, new_alloc;

	set_nonblock(fd);

	if (fd > max_fd)
		max_fd = fd;

	for (i = 0; i < sockets_alloc; i++)
		if (sockets[i].type == AUTH_UNUSED) {
			sockets[i].fd = fd;
			buffer_init(&sockets[i].input);
			buffer_init(&sockets[i].output);
			buffer_init(&sockets[i].request);
			sockets[i].type = type;
			return;
		}
	old_alloc = sockets_alloc;
	new_alloc = sockets_alloc + 10;
	if (sockets)
		sockets = xrealloc(sockets, new_alloc * sizeof(sockets[0]));
	else
		sockets = xmalloc(new_alloc * sizeof(sockets[0]));
	for (i = old_alloc; i < new_alloc; i++)
		sockets[i].type = AUTH_UNUSED;
	sockets_alloc = new_alloc;
	sockets[old_alloc].fd = fd;
	buffer_init(&sockets[old_alloc].input);
	buffer_init(&sockets[old_alloc].output);
	buffer_init(&sockets[old_alloc].request);
	sockets[old_alloc].type = type;
}

static int
prepare_select(fd_set **fdrp, fd_set **fdwp, int *fdl, u_int *nallocp)
{
	u_int i, sz;
	int n = 0;

	for (i = 0; i < sockets_alloc; i++) {
		switch (sockets[i].type) {
		case AUTH_SOCKET:
		case AUTH_CONNECTION:
			n = MAX(n, sockets[i].fd);
			break;
		case AUTH_UNUSED:
			break;
		default:
			fatal("Unknown socket type %d", sockets[i].type);
			break;
		}
	}

	sz = howmany(n+1, NFDBITS) * sizeof(fd_mask);
	if (*fdrp == NULL || sz > *nallocp) {
		if (*fdrp)
			xfree(*fdrp);
		if (*fdwp)
			xfree(*fdwp);
		*fdrp = xmalloc(sz);
		*fdwp = xmalloc(sz);
		*nallocp = sz;
	}
	if (n < *fdl)
		debug("XXX shrink: %d < %d", n, *fdl);
	*fdl = n;
	memset(*fdrp, 0, sz);
	memset(*fdwp, 0, sz);

	for (i = 0; i < sockets_alloc; i++) {
		switch (sockets[i].type) {
		case AUTH_SOCKET:
		case AUTH_CONNECTION:
			FD_SET(sockets[i].fd, *fdrp);
			if (buffer_len(&sockets[i].output) > 0)
				FD_SET(sockets[i].fd, *fdwp);
			break;
		default:
			break;
		}
	}
	return (1);
}

static void
after_select(fd_set *readset, fd_set *writeset)
{
	struct sockaddr_un sunaddr;
	socklen_t slen;
	char buf[1024];
	int len, sock;
	u_int i;
	uid_t euid;
	gid_t egid;

	for (i = 0; i < sockets_alloc; i++)
		switch (sockets[i].type) {
		case AUTH_UNUSED:
			break;
		case AUTH_SOCKET:
			if (FD_ISSET(sockets[i].fd, readset)) {
				slen = sizeof(sunaddr);
				sock = accept(sockets[i].fd,
				    (struct sockaddr *) &sunaddr, &slen);
				if (sock < 0) {
					error("accept from AUTH_SOCKET: %s",
					    strerror(errno));
					break;
				}
				if (getpeereid(sock, &euid, &egid) < 0) {
					error("getpeereid %d failed: %s",
					    sock, strerror(errno));
					close(sock);
					break;
				}
				if ((euid != 0) && (getuid() != euid)) {
					error("uid mismatch: "
					    "peer euid %u != uid %u",
					    (u_int) euid, (u_int) getuid());
					close(sock);
					break;
				}
				new_socket(AUTH_CONNECTION, sock);
			}
			break;
		case AUTH_CONNECTION:
			if (buffer_len(&sockets[i].output) > 0 &&
			    FD_ISSET(sockets[i].fd, writeset)) {
				do {
					len = write(sockets[i].fd,
					    buffer_ptr(&sockets[i].output),
					    buffer_len(&sockets[i].output));
					if (len == -1 && (errno == EAGAIN ||
					    errno == EINTR))
						continue;
					break;
				} while (1);
				if (len <= 0) {
					close_socket(&sockets[i]);
					break;
				}
				buffer_consume(&sockets[i].output, len);
			}
			if (FD_ISSET(sockets[i].fd, readset)) {
				do {
					len = read(sockets[i].fd, buf, sizeof(buf));
					if (len == -1 && (errno == EAGAIN ||
					    errno == EINTR))
						continue;
					break;
				} while (1);
				if (len <= 0) {
					close_socket(&sockets[i]);
					break;
				}
				buffer_append(&sockets[i].input, buf, len);
				process_message(&sockets[i]);
			}
			break;
		default:
			fatal("Unknown type %d", sockets[i].type);
		}
}

static void
cleanup_socket(void)
{
	if (socket_name[0])
		unlink(socket_name);
	if (socket_dir[0])
		rmdir(socket_dir);
}

void
cleanup_exit(int i)
{
	cleanup_socket();
	_exit(i);
}

static void
cleanup_handler(int sig)
{
	cleanup_socket();
	_exit(2);
}

static void
check_parent_exists(int sig)
{
	int save_errno = errno;

	if (parent_pid != -1 && kill(parent_pid, 0) < 0) {
		/* printf("Parent has died - Authentication agent exiting.\n"); */
		cleanup_handler(sig); /* safe */
	}
	mysignal(SIGALRM, check_parent_exists);
	alarm(10);
	errno = save_errno;
}

static void
usage(void)
{
	fprintf(stderr, "Usage: %s [options] [command [args ...]]\n",
	    __progname);
	fprintf(stderr, "Options:\n");
	fprintf(stderr, "  -c          Generate C-shell commands on stdout.\n");
	fprintf(stderr, "  -s          Generate Bourne shell commands on stdout.\n");
	fprintf(stderr, "  -k          Kill the current agent.\n");
	fprintf(stderr, "  -d          Debug mode.\n");
	fprintf(stderr, "  -a socket   Bind agent socket to given name.\n");
	fprintf(stderr, "  -t life     Default identity lifetime (seconds).\n");
	exit(1);
}

int
main(int ac, char **av)
{
	int c_flag = 0, d_flag = 0, k_flag = 0, s_flag = 0;
	int sock, fd,  ch;
	u_int nalloc;
	char *shell, *format, *pidstr, *agentsocket = NULL;
	fd_set *readsetp = NULL, *writesetp = NULL;
	struct sockaddr_un sunaddr;
#ifdef HAVE_SETRLIMIT
	struct rlimit rlim;
#endif
	int prev_mask;
	extern int optind;
	extern char *optarg;
	pid_t pid;
	char pidstrbuf[1 + 3 * sizeof pid];

	/* drop */
	setegid(getgid());
	setgid(getgid());

#if defined(HAVE_PRCTL) && defined(PR_SET_DUMPABLE)
	/* Disable ptrace on Linux without sgid bit */
	prctl(PR_SET_DUMPABLE, 0);
#endif

	SSLeay_add_all_algorithms();

	__progname = ssh_get_progname(av[0]);
	init_rng();
	seed_rng();

	while ((ch = getopt(ac, av, "cdksa:t:")) != -1) {
		switch (ch) {
		case 'c':
			if (s_flag)
				usage();
			c_flag++;
			break;
		case 'k':
			k_flag++;
			break;
		case 's':
			if (c_flag)
				usage();
			s_flag++;
			break;
		case 'd':
			if (d_flag)
				usage();
			d_flag++;
			break;
		case 'a':
			agentsocket = optarg;
			break;
		case 't':
			if ((lifetime = convtime(optarg)) == -1) {
				fprintf(stderr, "Invalid lifetime\n");
				usage();
			}
			break;
		default:
			usage();
		}
	}
	ac -= optind;
	av += optind;

	if (ac > 0 && (c_flag || k_flag || s_flag || d_flag))
		usage();

	if (ac == 0 && !c_flag && !s_flag) {
		shell = getenv("SHELL");
		if (shell != NULL && strncmp(shell + strlen(shell) - 3, "csh", 3) == 0)
			c_flag = 1;
	}
	if (k_flag) {
		pidstr = getenv(SSH_AGENTPID_ENV_NAME);
		if (pidstr == NULL) {
			fprintf(stderr, "%s not set, cannot kill agent\n",
			    SSH_AGENTPID_ENV_NAME);
			exit(1);
		}
		pid = atoi(pidstr);
		if (pid < 1) {
			fprintf(stderr, "%s=\"%s\", which is not a good PID\n",
			    SSH_AGENTPID_ENV_NAME, pidstr);
			exit(1);
		}
		if (kill(pid, SIGTERM) == -1) {
			perror("kill");
			exit(1);
		}
		format = c_flag ? "unsetenv %s;\n" : "unset %s;\n";
		printf(format, SSH_AUTHSOCKET_ENV_NAME);
		printf(format, SSH_AGENTPID_ENV_NAME);
		printf("echo Agent pid %ld killed;\n", (long)pid);
		exit(0);
	}
	parent_pid = getpid();

	if (agentsocket == NULL) {
		/* Create private directory for agent socket */
		strlcpy(socket_dir, "/tmp/ssh-XXXXXXXXXX", sizeof socket_dir);
		if (mkdtemp(socket_dir) == NULL) {
			perror("mkdtemp: private socket dir");
			exit(1);
		}
		snprintf(socket_name, sizeof socket_name, "%s/agent.%ld", socket_dir,
		    (long)parent_pid);
	} else {
		/* Try to use specified agent socket */
		socket_dir[0] = '\0';
		strlcpy(socket_name, agentsocket, sizeof socket_name);
	}

	/*
	 * Create socket early so it will exist before command gets run from
	 * the parent.
	 */
	sock = socket(AF_UNIX, SOCK_STREAM, 0);
	if (sock < 0) {
		perror("socket");
		*socket_name = '\0'; /* Don't unlink any existing file */
		cleanup_exit(1);
	}
	memset(&sunaddr, 0, sizeof(sunaddr));
	sunaddr.sun_family = AF_UNIX;
	strlcpy(sunaddr.sun_path, socket_name, sizeof(sunaddr.sun_path));
	prev_mask = umask(0177);
	if (bind(sock, (struct sockaddr *) & sunaddr, sizeof(sunaddr)) < 0) {
		perror("bind");
		*socket_name = '\0'; /* Don't unlink any existing file */
		umask(prev_mask);
		cleanup_exit(1);
	}
	umask(prev_mask);
	if (listen(sock, SSH_LISTEN_BACKLOG) < 0) {
		perror("listen");
		cleanup_exit(1);
	}

	/*
	 * Fork, and have the parent execute the command, if any, or present
	 * the socket data.  The child continues as the authentication agent.
	 */
	if (d_flag) {
		log_init(__progname, SYSLOG_LEVEL_DEBUG1, SYSLOG_FACILITY_AUTH, 1);
		format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n";
		printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name,
		    SSH_AUTHSOCKET_ENV_NAME);
		printf("echo Agent pid %ld;\n", (long)parent_pid);
		goto skip;
	}
	pid = fork();
	if (pid == -1) {
		perror("fork");
		cleanup_exit(1);
	}
	if (pid != 0) {		/* Parent - execute the given command. */
		close(sock);
		snprintf(pidstrbuf, sizeof pidstrbuf, "%ld", (long)pid);
		if (ac == 0) {
			format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n";
			printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name,
			    SSH_AUTHSOCKET_ENV_NAME);
			printf(format, SSH_AGENTPID_ENV_NAME, pidstrbuf,
			    SSH_AGENTPID_ENV_NAME);
			printf("echo Agent pid %ld;\n", (long)pid);
			exit(0);
		}
		if (setenv(SSH_AUTHSOCKET_ENV_NAME, socket_name, 1) == -1 ||
		    setenv(SSH_AGENTPID_ENV_NAME, pidstrbuf, 1) == -1) {
			perror("setenv");
			exit(1);
		}
		execvp(av[0], av);
		perror(av[0]);
		exit(1);
	}
	/* child */
	log_init(__progname, SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_AUTH, 0);

	if (setsid() == -1) {
		error("setsid: %s", strerror(errno));
		cleanup_exit(1);
	}

	(void)chdir("/");
	if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
		/* XXX might close listen socket */
		(void)dup2(fd, STDIN_FILENO);
		(void)dup2(fd, STDOUT_FILENO);
		(void)dup2(fd, STDERR_FILENO);
		if (fd > 2)
			close(fd);
	}

#ifdef HAVE_SETRLIMIT
	/* deny core dumps, since memory contains unencrypted private keys */
	rlim.rlim_cur = rlim.rlim_max = 0;
	if (setrlimit(RLIMIT_CORE, &rlim) < 0) {
		error("setrlimit RLIMIT_CORE: %s", strerror(errno));
		cleanup_exit(1);
	}
#endif

skip:
	new_socket(AUTH_SOCKET, sock);
	if (ac > 0) {
		mysignal(SIGALRM, check_parent_exists);
		alarm(10);
	}
	idtab_init();
	if (!d_flag)
		signal(SIGINT, SIG_IGN);
	signal(SIGPIPE, SIG_IGN);
	signal(SIGHUP, cleanup_handler);
	signal(SIGTERM, cleanup_handler);
	nalloc = 0;

	while (1) {
		prepare_select(&readsetp, &writesetp, &max_fd, &nalloc);
		if (select(max_fd + 1, readsetp, writesetp, NULL, NULL) < 0) {
			if (errno == EINTR)
				continue;
			fatal("select: %s", strerror(errno));
		}
		after_select(readsetp, writesetp);
	}
	/* NOTREACHED */
}