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 /* Sets the connection into non-blocking mode. */
110 packet_set_nonblocking()
112 /* Set the socket into non-blocking mode. */
113 if (fcntl(connection_in, F_SETFL, O_NONBLOCK) < 0)
114 error("fcntl O_NONBLOCK: %.100s", strerror(errno));
116 if (connection_out != connection_in) {
117 if (fcntl(connection_out, F_SETFL, O_NONBLOCK) < 0)
118 error("fcntl O_NONBLOCK: %.100s", strerror(errno));
122 /* Returns the socket used for reading. */
125 packet_get_connection_in()
127 return connection_in;
130 /* Returns the descriptor used for writing. */
133 packet_get_connection_out()
135 return connection_out;
138 /* Closes the connection and clears and frees internal data structures. */
146 if (connection_in == connection_out) {
147 shutdown(connection_out, SHUT_RDWR);
148 close(connection_out);
150 close(connection_in);
151 close(connection_out);
154 buffer_free(&output);
155 buffer_free(&outgoing_packet);
156 buffer_free(&incoming_packet);
157 if (packet_compression) {
158 buffer_free(&compression_buffer);
159 buffer_compress_uninit();
163 /* Sets remote side protocol flags. */
166 packet_set_protocol_flags(unsigned int protocol_flags)
168 remote_protocol_flags = protocol_flags;
169 channel_set_options((protocol_flags & SSH_PROTOFLAG_HOST_IN_FWD_OPEN) != 0);
172 /* Returns the remote protocol flags set earlier by the above function. */
175 packet_get_protocol_flags()
177 return remote_protocol_flags;
181 * Starts packet compression from the next packet on in both directions.
182 * Level is compression level 1 (fastest) - 9 (slow, best) as in gzip.
186 packet_start_compression(int level)
188 if (packet_compression)
189 fatal("Compression already enabled.");
190 packet_compression = 1;
191 buffer_init(&compression_buffer);
192 buffer_compress_init(level);
196 * Encrypts the given number of bytes, copying from src to dest. bytes is
197 * known to be a multiple of 8.
201 packet_encrypt(CipherContext * cc, void *dest, void *src,
204 cipher_encrypt(cc, dest, src, bytes);
208 * Decrypts the given number of bytes, copying from src to dest. bytes is
209 * known to be a multiple of 8.
213 packet_decrypt(CipherContext * cc, void *dest, void *src,
218 if ((bytes % 8) != 0)
219 fatal("packet_decrypt: bad ciphertext length %d", bytes);
222 * Cryptographic attack detector for ssh - Modifications for packet.c
223 * (C)1998 CORE-SDI, Buenos Aires Argentina Ariel Futoransky(futo@core-sdi.com)
227 case SSH_CIPHER_NONE:
231 i = detect_attack(src, bytes, NULL);
235 if (i == DEATTACK_DETECTED)
236 packet_disconnect("crc32 compensation attack: network attack detected");
238 cipher_decrypt(cc, dest, src, bytes);
242 * Causes any further packets to be encrypted using the given key. The same
243 * key is used for both sending and reception. However, both directions are
244 * encrypted independently of each other.
248 packet_set_encryption_key(const unsigned char *key, unsigned int keylen,
251 /* All other ciphers use the same key in both directions for now. */
252 cipher_set_key(&receive_context, cipher, key, keylen, 0);
253 cipher_set_key(&send_context, cipher, key, keylen, 1);
256 /* Starts constructing a packet to send. */
259 packet_start(int type)
263 buffer_clear(&outgoing_packet);
266 buffer_append(&outgoing_packet, buf, 9);
269 /* Appends a character to the packet data. */
272 packet_put_char(int value)
275 buffer_append(&outgoing_packet, &ch, 1);
278 /* Appends an integer to the packet data. */
281 packet_put_int(unsigned int value)
283 buffer_put_int(&outgoing_packet, value);
286 /* Appends a string to packet data. */
289 packet_put_string(const char *buf, unsigned int len)
291 buffer_put_string(&outgoing_packet, buf, len);
294 /* Appends an arbitrary precision integer to packet data. */
297 packet_put_bignum(BIGNUM * value)
299 buffer_put_bignum(&outgoing_packet, value);
303 * Finalizes and sends the packet. If the encryption key has been set,
304 * encrypts the packet before sending.
312 unsigned int checksum;
316 * If using packet compression, compress the payload of the outgoing
319 if (packet_compression) {
320 buffer_clear(&compression_buffer);
322 buffer_consume(&outgoing_packet, 8);
324 buffer_append(&compression_buffer, "\0\0\0\0\0\0\0\0", 8);
325 buffer_compress(&outgoing_packet, &compression_buffer);
326 buffer_clear(&outgoing_packet);
327 buffer_append(&outgoing_packet, buffer_ptr(&compression_buffer),
328 buffer_len(&compression_buffer));
330 /* Compute packet length without padding (add checksum, remove padding). */
331 len = buffer_len(&outgoing_packet) + 4 - 8;
333 /* Insert padding. */
334 padding = 8 - len % 8;
335 if (cipher_type != SSH_CIPHER_NONE) {
336 cp = buffer_ptr(&outgoing_packet);
337 for (i = 0; i < padding; i++) {
340 cp[7 - i] = rand & 0xff;
344 buffer_consume(&outgoing_packet, 8 - padding);
346 /* Add check bytes. */
347 checksum = crc32((unsigned char *) buffer_ptr(&outgoing_packet),
348 buffer_len(&outgoing_packet));
349 PUT_32BIT(buf, checksum);
350 buffer_append(&outgoing_packet, buf, 4);
353 fprintf(stderr, "packet_send plain: ");
354 buffer_dump(&outgoing_packet);
357 /* Append to output. */
359 buffer_append(&output, buf, 4);
360 buffer_append_space(&output, &cp, buffer_len(&outgoing_packet));
361 packet_encrypt(&send_context, cp, buffer_ptr(&outgoing_packet),
362 buffer_len(&outgoing_packet));
365 fprintf(stderr, "encrypted: ");
366 buffer_dump(&output);
369 buffer_clear(&outgoing_packet);
372 * Note that the packet is now only buffered in output. It won\'t be
373 * actually sent until packet_write_wait or packet_write_poll is
379 * Waits until a packet has been received, and returns its type. Note that
380 * no other data is processed until this returns, so this function should not
381 * be used during the interactive session.
385 packet_read(int *payload_len_ptr)
391 /* Since we are blocking, ensure that all written packets have been sent. */
394 /* Stay in the loop until we have received a complete packet. */
396 /* Try to read a packet from the buffer. */
397 type = packet_read_poll(payload_len_ptr);
398 if (type == SSH_SMSG_SUCCESS
399 || type == SSH_SMSG_FAILURE
400 || type == SSH_CMSG_EOF
401 || type == SSH_CMSG_EXIT_CONFIRMATION)
402 packet_integrity_check(*payload_len_ptr, 0, type);
403 /* If we got a packet, return it. */
404 if (type != SSH_MSG_NONE)
407 * Otherwise, wait for some data to arrive, add it to the
408 * buffer, and try again.
411 FD_SET(connection_in, &set);
413 /* Wait for some data to arrive. */
414 select(connection_in + 1, &set, NULL, NULL, NULL);
416 /* Read data from the socket. */
417 len = read(connection_in, buf, sizeof(buf));
419 log("Connection closed by %.200s", get_remote_ipaddr());
423 fatal("Read from socket failed: %.100s", strerror(errno));
424 /* Append it to the buffer. */
425 packet_process_incoming(buf, len);
431 * Waits until a packet has been received, verifies that its type matches
432 * that given, and gives a fatal error and exits if there is a mismatch.
436 packet_read_expect(int *payload_len_ptr, int expected_type)
440 type = packet_read(payload_len_ptr);
441 if (type != expected_type)
442 packet_disconnect("Protocol error: expected packet type %d, got %d",
443 expected_type, type);
446 /* Checks if a full packet is available in the data received so far via
447 * packet_process_incoming. If so, reads the packet; otherwise returns
448 * SSH_MSG_NONE. This does not wait for data from the connection.
450 * SSH_MSG_DISCONNECT is handled specially here. Also,
451 * SSH_MSG_IGNORE messages are skipped by this function and are never returned
454 * The returned payload_len does include space consumed by:
462 packet_read_poll(int *payload_len_ptr)
464 unsigned int len, padded_len;
467 unsigned int checksum, stored_checksum;
471 /* Check if input size is less than minimum packet size. */
472 if (buffer_len(&input) < 4 + 8)
474 /* Get length of incoming packet. */
475 ucp = (unsigned char *) buffer_ptr(&input);
476 len = GET_32BIT(ucp);
477 if (len < 1 + 2 + 2 || len > 256 * 1024)
478 packet_disconnect("Bad packet length %d.", len);
479 padded_len = (len + 8) & ~7;
481 /* Check if the packet has been entirely received. */
482 if (buffer_len(&input) < 4 + padded_len)
485 /* The entire packet is in buffer. */
487 /* Consume packet length. */
488 buffer_consume(&input, 4);
490 /* Copy data to incoming_packet. */
491 buffer_clear(&incoming_packet);
492 buffer_append_space(&incoming_packet, &cp, padded_len);
493 packet_decrypt(&receive_context, cp, buffer_ptr(&input), padded_len);
494 buffer_consume(&input, padded_len);
497 fprintf(stderr, "read_poll plain: ");
498 buffer_dump(&incoming_packet);
501 /* Compute packet checksum. */
502 checksum = crc32((unsigned char *) buffer_ptr(&incoming_packet),
503 buffer_len(&incoming_packet) - 4);
506 buffer_consume(&incoming_packet, 8 - len % 8);
508 /* Test check bytes. */
510 if (len != buffer_len(&incoming_packet))
511 packet_disconnect("packet_read_poll: len %d != buffer_len %d.",
512 len, buffer_len(&incoming_packet));
514 ucp = (unsigned char *) buffer_ptr(&incoming_packet) + len - 4;
515 stored_checksum = GET_32BIT(ucp);
516 if (checksum != stored_checksum)
517 packet_disconnect("Corrupted check bytes on input.");
518 buffer_consume_end(&incoming_packet, 4);
520 /* If using packet compression, decompress the packet. */
521 if (packet_compression) {
522 buffer_clear(&compression_buffer);
523 buffer_uncompress(&incoming_packet, &compression_buffer);
524 buffer_clear(&incoming_packet);
525 buffer_append(&incoming_packet, buffer_ptr(&compression_buffer),
526 buffer_len(&compression_buffer));
528 /* Get packet type. */
529 buffer_get(&incoming_packet, &buf[0], 1);
531 /* Return length of payload (without type field). */
532 *payload_len_ptr = buffer_len(&incoming_packet);
534 /* Handle disconnect message. */
535 if ((unsigned char) buf[0] == SSH_MSG_DISCONNECT) {
536 log("Received disconnect: %.900s", packet_get_string(NULL));
540 /* Ignore ignore messages. */
541 if ((unsigned char) buf[0] == SSH_MSG_IGNORE)
544 /* Send debug messages as debugging output. */
545 if ((unsigned char) buf[0] == SSH_MSG_DEBUG) {
546 debug("Remote: %.900s", packet_get_string(NULL));
550 return (unsigned char) buf[0];
554 * Buffers the given amount of input characters. This is intended to be used
555 * together with packet_read_poll.
559 packet_process_incoming(const char *buf, unsigned int len)
561 buffer_append(&input, buf, len);
564 /* Returns a character from the packet. */
570 buffer_get(&incoming_packet, &ch, 1);
571 return (unsigned char) ch;
574 /* Returns an integer from the packet data. */
579 return buffer_get_int(&incoming_packet);
583 * Returns an arbitrary precision integer from the packet data. The integer
584 * must have been initialized before this call.
588 packet_get_bignum(BIGNUM * value, int *length_ptr)
590 *length_ptr = buffer_get_bignum(&incoming_packet, value);
594 * Returns a string from the packet data. The string is allocated using
595 * xmalloc; it is the responsibility of the calling program to free it when
596 * no longer needed. The length_ptr argument may be NULL, or point to an
597 * integer into which the length of the string is stored.
601 packet_get_string(unsigned int *length_ptr)
603 return buffer_get_string(&incoming_packet, length_ptr);
607 * Sends a diagnostic message from the server to the client. This message
608 * can be sent at any time (but not while constructing another message). The
609 * message is printed immediately, but only if the client is being executed
610 * in verbose mode. These messages are primarily intended to ease debugging
611 * authentication problems. The length of the formatted message must not
612 * exceed 1024 bytes. This will automatically call packet_write_wait.
616 packet_send_debug(const char *fmt,...)
622 vsnprintf(buf, sizeof(buf), fmt, args);
625 packet_start(SSH_MSG_DEBUG);
626 packet_put_string(buf, strlen(buf));
632 * Logs the error plus constructs and sends a disconnect packet, closes the
633 * connection, and exits. This function never returns. The error message
634 * should not contain a newline. The length of the formatted message must
635 * not exceed 1024 bytes.
639 packet_disconnect(const char *fmt,...)
643 static int disconnecting = 0;
644 if (disconnecting) /* Guard against recursive invocations. */
645 fatal("packet_disconnect called recursively.");
649 * Format the message. Note that the caller must make sure the
650 * message is of limited size.
653 vsnprintf(buf, sizeof(buf), fmt, args);
656 /* Send the disconnect message to the other side, and wait for it to get sent. */
657 packet_start(SSH_MSG_DISCONNECT);
658 packet_put_string(buf, strlen(buf));
662 /* Stop listening for connections. */
663 channel_stop_listening();
665 /* Close the connection. */
668 /* Display the error locally and exit. */
669 log("Disconnecting: %.100s", buf);
673 /* Checks if there is any buffered output, and tries to write some of the output. */
678 int len = buffer_len(&output);
680 len = write(connection_out, buffer_ptr(&output), len);
685 fatal("Write failed: %.100s", strerror(errno));
687 buffer_consume(&output, len);
692 * Calls packet_write_poll repeatedly until all pending output data has been
700 while (packet_have_data_to_write()) {
703 FD_SET(connection_out, &set);
704 select(connection_out + 1, NULL, &set, NULL, NULL);
709 /* Returns true if there is buffered data to write to the connection. */
712 packet_have_data_to_write()
714 return buffer_len(&output) != 0;
717 /* Returns true if there is not too much data to write to the connection. */
720 packet_not_very_much_data_to_write()
722 if (interactive_mode)
723 return buffer_len(&output) < 16384;
725 return buffer_len(&output) < 128 * 1024;
728 /* Informs that the current session is interactive. Sets IP flags for that. */
731 packet_set_interactive(int interactive, int keepalives)
735 /* Record that we are in interactive mode. */
736 interactive_mode = interactive;
739 * Only set socket options if using a socket (as indicated by the
740 * descriptors being the same).
742 if (connection_in != connection_out)
746 /* Set keepalives if requested. */
747 if (setsockopt(connection_in, SOL_SOCKET, SO_KEEPALIVE, (void *) &on,
749 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
753 * Set IP options for an interactive connection. Use
754 * IPTOS_LOWDELAY and TCP_NODELAY.
756 int lowdelay = IPTOS_LOWDELAY;
757 if (setsockopt(connection_in, IPPROTO_IP, IP_TOS, (void *) &lowdelay,
758 sizeof(lowdelay)) < 0)
759 error("setsockopt IPTOS_LOWDELAY: %.100s", strerror(errno));
760 if (setsockopt(connection_in, IPPROTO_TCP, TCP_NODELAY, (void *) &on,
762 error("setsockopt TCP_NODELAY: %.100s", strerror(errno));
765 * Set IP options for a non-interactive connection. Use
768 int throughput = IPTOS_THROUGHPUT;
769 if (setsockopt(connection_in, IPPROTO_IP, IP_TOS, (void *) &throughput,
770 sizeof(throughput)) < 0)
771 error("setsockopt IPTOS_THROUGHPUT: %.100s", strerror(errno));
775 /* Returns true if the current connection is interactive. */
778 packet_is_interactive()
780 return interactive_mode;
784 packet_set_maxsize(int s)
786 static int called = 0;
788 log("packet_set_maxsize: called twice: old %d new %d", max_packet_size, s);
791 if (s < 4 * 1024 || s > 1024 * 1024) {
792 log("packet_set_maxsize: bad size %d", s);
795 log("packet_set_maxsize: setting to %d", s);