5 * Author: Tatu Ylonen <ylo@cs.hut.fi>
7 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
10 * Created: Sat Mar 18 02:40:40 1995 ylo
12 * This file contains code implementing the packet protocol and communication
13 * with the other side. This same code is used both on client and server side.
33 * This variable contains the file descriptors used for communicating with
34 * the other side. connection_in is used for reading; connection_out for
35 * writing. These can be the same descriptor, in which case it is assumed to
38 static int connection_in = -1;
39 static int connection_out = -1;
42 * Cipher type. This value is only used to determine whether to pad the
43 * packets with zeroes or random data.
45 static int cipher_type = SSH_CIPHER_NONE;
47 /* Protocol flags for the remote side. */
48 static unsigned int remote_protocol_flags = 0;
50 /* Encryption context for receiving data. This is only used for decryption. */
51 static CipherContext receive_context;
53 /* Encryption context for sending data. This is only used for encryption. */
54 static CipherContext send_context;
56 /* Buffer for raw input data from the socket. */
59 /* Buffer for raw output data going to the socket. */
62 /* Buffer for the partial outgoing packet being constructed. */
63 static Buffer outgoing_packet;
65 /* Buffer for the incoming packet currently being processed. */
66 static Buffer incoming_packet;
68 /* Scratch buffer for packet compression/decompression. */
69 static Buffer compression_buffer;
71 /* Flag indicating whether packet compression/decompression is enabled. */
72 static int packet_compression = 0;
74 /* default maximum packet size */
75 int max_packet_size = 32768;
77 /* Flag indicating whether this module has been initialized. */
78 static int initialized = 0;
80 /* Set to true if the connection is interactive. */
81 static int interactive_mode = 0;
84 * Sets the descriptors used for communication. Disables encryption until
85 * packet_set_encryption_key is called.
89 packet_set_connection(int fd_in, int fd_out)
91 connection_in = fd_in;
92 connection_out = fd_out;
93 cipher_type = SSH_CIPHER_NONE;
94 cipher_set_key(&send_context, SSH_CIPHER_NONE, (unsigned char *) "", 0, 1);
95 cipher_set_key(&receive_context, SSH_CIPHER_NONE, (unsigned char *) "", 0, 0);
100 buffer_init(&outgoing_packet);
101 buffer_init(&incoming_packet);
103 /* Kludge: arrange the close function to be called from fatal(). */
104 fatal_add_cleanup((void (*) (void *)) packet_close, NULL);
107 /* Returns 1 if remote host is connected via socket, 0 if not. */
110 packet_connection_is_on_socket()
112 struct sockaddr_storage from, to;
113 socklen_t fromlen, tolen;
115 /* filedescriptors in and out are the same, so it's a socket */
116 if (connection_in == connection_out)
118 fromlen = sizeof(from);
119 memset(&from, 0, sizeof(from));
120 if (getpeername(connection_in, (struct sockaddr *) & from, &fromlen) < 0)
123 memset(&to, 0, sizeof(to));
124 if (getsockname(connection_out, (struct sockaddr *)&to, &tolen) < 0)
126 if (fromlen != tolen || memcmp(&from, &to, fromlen) != 0)
128 if (from.ss_family != AF_INET && from.ss_family != AF_INET6)
133 /* returns 1 if connection is via ipv4 */
136 packet_connection_is_ipv4()
138 struct sockaddr_storage to;
141 memset(&to, 0, sizeof(to));
142 if (getsockname(connection_out, (struct sockaddr *)&to, &tolen) < 0)
144 if (to.ss_family != AF_INET)
149 /* Sets the connection into non-blocking mode. */
152 packet_set_nonblocking()
154 /* Set the socket into non-blocking mode. */
155 if (fcntl(connection_in, F_SETFL, O_NONBLOCK) < 0)
156 error("fcntl O_NONBLOCK: %.100s", strerror(errno));
158 if (connection_out != connection_in) {
159 if (fcntl(connection_out, F_SETFL, O_NONBLOCK) < 0)
160 error("fcntl O_NONBLOCK: %.100s", strerror(errno));
164 /* Returns the socket used for reading. */
167 packet_get_connection_in()
169 return connection_in;
172 /* Returns the descriptor used for writing. */
175 packet_get_connection_out()
177 return connection_out;
180 /* Closes the connection and clears and frees internal data structures. */
188 if (connection_in == connection_out) {
189 shutdown(connection_out, SHUT_RDWR);
190 close(connection_out);
192 close(connection_in);
193 close(connection_out);
196 buffer_free(&output);
197 buffer_free(&outgoing_packet);
198 buffer_free(&incoming_packet);
199 if (packet_compression) {
200 buffer_free(&compression_buffer);
201 buffer_compress_uninit();
205 /* Sets remote side protocol flags. */
208 packet_set_protocol_flags(unsigned int protocol_flags)
210 remote_protocol_flags = protocol_flags;
211 channel_set_options((protocol_flags & SSH_PROTOFLAG_HOST_IN_FWD_OPEN) != 0);
214 /* Returns the remote protocol flags set earlier by the above function. */
217 packet_get_protocol_flags()
219 return remote_protocol_flags;
223 * Starts packet compression from the next packet on in both directions.
224 * Level is compression level 1 (fastest) - 9 (slow, best) as in gzip.
228 packet_start_compression(int level)
230 if (packet_compression)
231 fatal("Compression already enabled.");
232 packet_compression = 1;
233 buffer_init(&compression_buffer);
234 buffer_compress_init(level);
238 * Encrypts the given number of bytes, copying from src to dest. bytes is
239 * known to be a multiple of 8.
243 packet_encrypt(CipherContext * cc, void *dest, void *src,
246 cipher_encrypt(cc, dest, src, bytes);
250 * Decrypts the given number of bytes, copying from src to dest. bytes is
251 * known to be a multiple of 8.
255 packet_decrypt(CipherContext * cc, void *dest, void *src,
260 if ((bytes % 8) != 0)
261 fatal("packet_decrypt: bad ciphertext length %d", bytes);
264 * Cryptographic attack detector for ssh - Modifications for packet.c
265 * (C)1998 CORE-SDI, Buenos Aires Argentina Ariel Futoransky(futo@core-sdi.com)
269 case SSH_CIPHER_NONE:
273 i = detect_attack(src, bytes, NULL);
277 if (i == DEATTACK_DETECTED)
278 packet_disconnect("crc32 compensation attack: network attack detected");
280 cipher_decrypt(cc, dest, src, bytes);
284 * Causes any further packets to be encrypted using the given key. The same
285 * key is used for both sending and reception. However, both directions are
286 * encrypted independently of each other.
290 packet_set_encryption_key(const unsigned char *key, unsigned int keylen,
293 /* All other ciphers use the same key in both directions for now. */
294 cipher_set_key(&receive_context, cipher, key, keylen, 0);
295 cipher_set_key(&send_context, cipher, key, keylen, 1);
298 /* Starts constructing a packet to send. */
301 packet_start(int type)
305 buffer_clear(&outgoing_packet);
308 buffer_append(&outgoing_packet, buf, 9);
311 /* Appends a character to the packet data. */
314 packet_put_char(int value)
317 buffer_append(&outgoing_packet, &ch, 1);
320 /* Appends an integer to the packet data. */
323 packet_put_int(unsigned int value)
325 buffer_put_int(&outgoing_packet, value);
328 /* Appends a string to packet data. */
331 packet_put_string(const char *buf, unsigned int len)
333 buffer_put_string(&outgoing_packet, buf, len);
336 /* Appends an arbitrary precision integer to packet data. */
339 packet_put_bignum(BIGNUM * value)
341 buffer_put_bignum(&outgoing_packet, value);
345 * Finalizes and sends the packet. If the encryption key has been set,
346 * encrypts the packet before sending.
354 unsigned int checksum;
358 * If using packet compression, compress the payload of the outgoing
361 if (packet_compression) {
362 buffer_clear(&compression_buffer);
364 buffer_consume(&outgoing_packet, 8);
366 buffer_append(&compression_buffer, "\0\0\0\0\0\0\0\0", 8);
367 buffer_compress(&outgoing_packet, &compression_buffer);
368 buffer_clear(&outgoing_packet);
369 buffer_append(&outgoing_packet, buffer_ptr(&compression_buffer),
370 buffer_len(&compression_buffer));
372 /* Compute packet length without padding (add checksum, remove padding). */
373 len = buffer_len(&outgoing_packet) + 4 - 8;
375 /* Insert padding. */
376 padding = 8 - len % 8;
377 if (cipher_type != SSH_CIPHER_NONE) {
378 cp = buffer_ptr(&outgoing_packet);
379 for (i = 0; i < padding; i++) {
382 cp[7 - i] = rand & 0xff;
386 buffer_consume(&outgoing_packet, 8 - padding);
388 /* Add check bytes. */
389 checksum = crc32((unsigned char *) buffer_ptr(&outgoing_packet),
390 buffer_len(&outgoing_packet));
391 PUT_32BIT(buf, checksum);
392 buffer_append(&outgoing_packet, buf, 4);
395 fprintf(stderr, "packet_send plain: ");
396 buffer_dump(&outgoing_packet);
399 /* Append to output. */
401 buffer_append(&output, buf, 4);
402 buffer_append_space(&output, &cp, buffer_len(&outgoing_packet));
403 packet_encrypt(&send_context, cp, buffer_ptr(&outgoing_packet),
404 buffer_len(&outgoing_packet));
407 fprintf(stderr, "encrypted: ");
408 buffer_dump(&output);
411 buffer_clear(&outgoing_packet);
414 * Note that the packet is now only buffered in output. It won\'t be
415 * actually sent until packet_write_wait or packet_write_poll is
421 * Waits until a packet has been received, and returns its type. Note that
422 * no other data is processed until this returns, so this function should not
423 * be used during the interactive session.
427 packet_read(int *payload_len_ptr)
433 /* Since we are blocking, ensure that all written packets have been sent. */
436 /* Stay in the loop until we have received a complete packet. */
438 /* Try to read a packet from the buffer. */
439 type = packet_read_poll(payload_len_ptr);
440 if (type == SSH_SMSG_SUCCESS
441 || type == SSH_SMSG_FAILURE
442 || type == SSH_CMSG_EOF
443 || type == SSH_CMSG_EXIT_CONFIRMATION)
444 packet_integrity_check(*payload_len_ptr, 0, type);
445 /* If we got a packet, return it. */
446 if (type != SSH_MSG_NONE)
449 * Otherwise, wait for some data to arrive, add it to the
450 * buffer, and try again.
453 FD_SET(connection_in, &set);
455 /* Wait for some data to arrive. */
456 select(connection_in + 1, &set, NULL, NULL, NULL);
458 /* Read data from the socket. */
459 len = read(connection_in, buf, sizeof(buf));
461 log("Connection closed by %.200s", get_remote_ipaddr());
465 fatal("Read from socket failed: %.100s", strerror(errno));
466 /* Append it to the buffer. */
467 packet_process_incoming(buf, len);
473 * Waits until a packet has been received, verifies that its type matches
474 * that given, and gives a fatal error and exits if there is a mismatch.
478 packet_read_expect(int *payload_len_ptr, int expected_type)
482 type = packet_read(payload_len_ptr);
483 if (type != expected_type)
484 packet_disconnect("Protocol error: expected packet type %d, got %d",
485 expected_type, type);
488 /* Checks if a full packet is available in the data received so far via
489 * packet_process_incoming. If so, reads the packet; otherwise returns
490 * SSH_MSG_NONE. This does not wait for data from the connection.
492 * SSH_MSG_DISCONNECT is handled specially here. Also,
493 * SSH_MSG_IGNORE messages are skipped by this function and are never returned
496 * The returned payload_len does include space consumed by:
504 packet_read_poll(int *payload_len_ptr)
506 unsigned int len, padded_len;
509 unsigned int checksum, stored_checksum;
513 /* Check if input size is less than minimum packet size. */
514 if (buffer_len(&input) < 4 + 8)
516 /* Get length of incoming packet. */
517 ucp = (unsigned char *) buffer_ptr(&input);
518 len = GET_32BIT(ucp);
519 if (len < 1 + 2 + 2 || len > 256 * 1024)
520 packet_disconnect("Bad packet length %d.", len);
521 padded_len = (len + 8) & ~7;
523 /* Check if the packet has been entirely received. */
524 if (buffer_len(&input) < 4 + padded_len)
527 /* The entire packet is in buffer. */
529 /* Consume packet length. */
530 buffer_consume(&input, 4);
532 /* Copy data to incoming_packet. */
533 buffer_clear(&incoming_packet);
534 buffer_append_space(&incoming_packet, &cp, padded_len);
535 packet_decrypt(&receive_context, cp, buffer_ptr(&input), padded_len);
536 buffer_consume(&input, padded_len);
539 fprintf(stderr, "read_poll plain: ");
540 buffer_dump(&incoming_packet);
543 /* Compute packet checksum. */
544 checksum = crc32((unsigned char *) buffer_ptr(&incoming_packet),
545 buffer_len(&incoming_packet) - 4);
548 buffer_consume(&incoming_packet, 8 - len % 8);
550 /* Test check bytes. */
552 if (len != buffer_len(&incoming_packet))
553 packet_disconnect("packet_read_poll: len %d != buffer_len %d.",
554 len, buffer_len(&incoming_packet));
556 ucp = (unsigned char *) buffer_ptr(&incoming_packet) + len - 4;
557 stored_checksum = GET_32BIT(ucp);
558 if (checksum != stored_checksum)
559 packet_disconnect("Corrupted check bytes on input.");
560 buffer_consume_end(&incoming_packet, 4);
562 /* If using packet compression, decompress the packet. */
563 if (packet_compression) {
564 buffer_clear(&compression_buffer);
565 buffer_uncompress(&incoming_packet, &compression_buffer);
566 buffer_clear(&incoming_packet);
567 buffer_append(&incoming_packet, buffer_ptr(&compression_buffer),
568 buffer_len(&compression_buffer));
570 /* Get packet type. */
571 buffer_get(&incoming_packet, &buf[0], 1);
573 /* Return length of payload (without type field). */
574 *payload_len_ptr = buffer_len(&incoming_packet);
576 /* Handle disconnect message. */
577 if ((unsigned char) buf[0] == SSH_MSG_DISCONNECT) {
578 log("Received disconnect: %.900s", packet_get_string(NULL));
582 /* Ignore ignore messages. */
583 if ((unsigned char) buf[0] == SSH_MSG_IGNORE)
586 /* Send debug messages as debugging output. */
587 if ((unsigned char) buf[0] == SSH_MSG_DEBUG) {
588 debug("Remote: %.900s", packet_get_string(NULL));
592 return (unsigned char) buf[0];
596 * Buffers the given amount of input characters. This is intended to be used
597 * together with packet_read_poll.
601 packet_process_incoming(const char *buf, unsigned int len)
603 buffer_append(&input, buf, len);
606 /* Returns a character from the packet. */
612 buffer_get(&incoming_packet, &ch, 1);
613 return (unsigned char) ch;
616 /* Returns an integer from the packet data. */
621 return buffer_get_int(&incoming_packet);
625 * Returns an arbitrary precision integer from the packet data. The integer
626 * must have been initialized before this call.
630 packet_get_bignum(BIGNUM * value, int *length_ptr)
632 *length_ptr = buffer_get_bignum(&incoming_packet, value);
636 * Returns a string from the packet data. The string is allocated using
637 * xmalloc; it is the responsibility of the calling program to free it when
638 * no longer needed. The length_ptr argument may be NULL, or point to an
639 * integer into which the length of the string is stored.
643 packet_get_string(unsigned int *length_ptr)
645 return buffer_get_string(&incoming_packet, length_ptr);
649 * Sends a diagnostic message from the server to the client. This message
650 * can be sent at any time (but not while constructing another message). The
651 * message is printed immediately, but only if the client is being executed
652 * in verbose mode. These messages are primarily intended to ease debugging
653 * authentication problems. The length of the formatted message must not
654 * exceed 1024 bytes. This will automatically call packet_write_wait.
658 packet_send_debug(const char *fmt,...)
664 vsnprintf(buf, sizeof(buf), fmt, args);
667 packet_start(SSH_MSG_DEBUG);
668 packet_put_string(buf, strlen(buf));
674 * Logs the error plus constructs and sends a disconnect packet, closes the
675 * connection, and exits. This function never returns. The error message
676 * should not contain a newline. The length of the formatted message must
677 * not exceed 1024 bytes.
681 packet_disconnect(const char *fmt,...)
685 static int disconnecting = 0;
686 if (disconnecting) /* Guard against recursive invocations. */
687 fatal("packet_disconnect called recursively.");
691 * Format the message. Note that the caller must make sure the
692 * message is of limited size.
695 vsnprintf(buf, sizeof(buf), fmt, args);
698 /* Send the disconnect message to the other side, and wait for it to get sent. */
699 packet_start(SSH_MSG_DISCONNECT);
700 packet_put_string(buf, strlen(buf));
704 /* Stop listening for connections. */
705 channel_stop_listening();
707 /* Close the connection. */
710 /* Display the error locally and exit. */
711 log("Disconnecting: %.100s", buf);
715 /* Checks if there is any buffered output, and tries to write some of the output. */
720 int len = buffer_len(&output);
722 len = write(connection_out, buffer_ptr(&output), len);
727 fatal("Write failed: %.100s", strerror(errno));
729 buffer_consume(&output, len);
734 * Calls packet_write_poll repeatedly until all pending output data has been
742 while (packet_have_data_to_write()) {
745 FD_SET(connection_out, &set);
746 select(connection_out + 1, NULL, &set, NULL, NULL);
751 /* Returns true if there is buffered data to write to the connection. */
754 packet_have_data_to_write()
756 return buffer_len(&output) != 0;
759 /* Returns true if there is not too much data to write to the connection. */
762 packet_not_very_much_data_to_write()
764 if (interactive_mode)
765 return buffer_len(&output) < 16384;
767 return buffer_len(&output) < 128 * 1024;
770 /* Informs that the current session is interactive. Sets IP flags for that. */
773 packet_set_interactive(int interactive, int keepalives)
777 /* Record that we are in interactive mode. */
778 interactive_mode = interactive;
780 /* Only set socket options if using a socket. */
781 if (!packet_connection_is_on_socket())
784 /* Set keepalives if requested. */
785 if (setsockopt(connection_in, SOL_SOCKET, SO_KEEPALIVE, (void *) &on,
787 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
790 * IPTOS_LOWDELAY, TCP_NODELAY and IPTOS_THROUGHPUT are IPv4 only
792 if (!packet_connection_is_ipv4())
796 * Set IP options for an interactive connection. Use
797 * IPTOS_LOWDELAY and TCP_NODELAY.
799 int lowdelay = IPTOS_LOWDELAY;
800 if (setsockopt(connection_in, IPPROTO_IP, IP_TOS, (void *) &lowdelay,
801 sizeof(lowdelay)) < 0)
802 error("setsockopt IPTOS_LOWDELAY: %.100s", strerror(errno));
803 if (setsockopt(connection_in, IPPROTO_TCP, TCP_NODELAY, (void *) &on,
805 error("setsockopt TCP_NODELAY: %.100s", strerror(errno));
808 * Set IP options for a non-interactive connection. Use
811 int throughput = IPTOS_THROUGHPUT;
812 if (setsockopt(connection_in, IPPROTO_IP, IP_TOS, (void *) &throughput,
813 sizeof(throughput)) < 0)
814 error("setsockopt IPTOS_THROUGHPUT: %.100s", strerror(errno));
818 /* Returns true if the current connection is interactive. */
821 packet_is_interactive()
823 return interactive_mode;
827 packet_set_maxsize(int s)
829 static int called = 0;
831 log("packet_set_maxsize: called twice: old %d new %d", max_packet_size, s);
834 if (s < 4 * 1024 || s > 1024 * 1024) {
835 log("packet_set_maxsize: bad size %d", s);
838 log("packet_set_maxsize: setting to %d", s);