/* * Author: Tatu Ylonen * Copyright (c) 1995 Tatu Ylonen , Espoo, Finland * All rights reserved * This file contains code implementing the packet protocol and communication * with the other side. This same code is used both on client and server side. * * As far as I am concerned, the code I have written for this software * can be used freely for any purpose. Any derived versions of this * software must be clearly marked as such, and if the derived work is * incompatible with the protocol description in the RFC file, it must be * called by a name other than "ssh" or "Secure Shell". * * * SSH2 packet format added by Markus Friedl. * Copyright (c) 2000, 2001 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: packet.c,v 1.115 2004/06/21 17:36:31 avsm Exp $"); #include "openbsd-compat/sys-queue.h" #include "xmalloc.h" #include "buffer.h" #include "packet.h" #include "bufaux.h" #include "crc32.h" #include "getput.h" #include "compress.h" #include "deattack.h" #include "channels.h" #include "compat.h" #include "ssh1.h" #include "ssh2.h" #include "cipher.h" #include "kex.h" #include "mac.h" #include "log.h" #include "canohost.h" #include "misc.h" #include "ssh.h" #ifdef PACKET_DEBUG #define DBG(x) x #else #define DBG(x) #endif /* * This variable contains the file descriptors used for communicating with * the other side. connection_in is used for reading; connection_out for * writing. These can be the same descriptor, in which case it is assumed to * be a socket. */ static int connection_in = -1; static int connection_out = -1; /* Protocol flags for the remote side. */ static u_int remote_protocol_flags = 0; /* Encryption context for receiving data. This is only used for decryption. */ static CipherContext receive_context; /* Encryption context for sending data. This is only used for encryption. */ static CipherContext send_context; /* Buffer for raw input data from the socket. */ Buffer input; /* Buffer for raw output data going to the socket. */ Buffer output; /* Buffer for the partial outgoing packet being constructed. */ static Buffer outgoing_packet; /* Buffer for the incoming packet currently being processed. */ static Buffer incoming_packet; /* Scratch buffer for packet compression/decompression. */ static Buffer compression_buffer; static int compression_buffer_ready = 0; /* Flag indicating whether packet compression/decompression is enabled. */ static int packet_compression = 0; /* default maximum packet size */ u_int max_packet_size = 32768; /* Flag indicating whether this module has been initialized. */ static int initialized = 0; /* Set to true if the connection is interactive. */ static int interactive_mode = 0; /* Session key information for Encryption and MAC */ Newkeys *newkeys[MODE_MAX]; static struct packet_state { u_int32_t seqnr; u_int32_t packets; u_int64_t blocks; } p_read, p_send; static u_int64_t max_blocks_in, max_blocks_out; static u_int32_t rekey_limit; /* Session key for protocol v1 */ static u_char ssh1_key[SSH_SESSION_KEY_LENGTH]; static u_int ssh1_keylen; /* roundup current message to extra_pad bytes */ static u_char extra_pad = 0; struct packet { TAILQ_ENTRY(packet) next; u_char type; Buffer payload; }; TAILQ_HEAD(, packet) outgoing; /* * Sets the descriptors used for communication. Disables encryption until * packet_set_encryption_key is called. */ void packet_set_connection(int fd_in, int fd_out) { Cipher *none = cipher_by_name("none"); if (none == NULL) fatal("packet_set_connection: cannot load cipher 'none'"); connection_in = fd_in; connection_out = fd_out; cipher_init(&send_context, none, (const u_char *)"", 0, NULL, 0, CIPHER_ENCRYPT); cipher_init(&receive_context, none, (const u_char *)"", 0, NULL, 0, CIPHER_DECRYPT); newkeys[MODE_IN] = newkeys[MODE_OUT] = NULL; if (!initialized) { initialized = 1; buffer_init(&input); buffer_init(&output); buffer_init(&outgoing_packet); buffer_init(&incoming_packet); TAILQ_INIT(&outgoing); } } /* Returns 1 if remote host is connected via socket, 0 if not. */ int packet_connection_is_on_socket(void) { struct sockaddr_storage from, to; socklen_t fromlen, tolen; /* filedescriptors in and out are the same, so it's a socket */ if (connection_in == connection_out) return 1; fromlen = sizeof(from); memset(&from, 0, sizeof(from)); if (getpeername(connection_in, (struct sockaddr *)&from, &fromlen) < 0) return 0; tolen = sizeof(to); memset(&to, 0, sizeof(to)); if (getpeername(connection_out, (struct sockaddr *)&to, &tolen) < 0) return 0; if (fromlen != tolen || memcmp(&from, &to, fromlen) != 0) return 0; if (from.ss_family != AF_INET && from.ss_family != AF_INET6) return 0; return 1; } /* * Exports an IV from the CipherContext required to export the key * state back from the unprivileged child to the privileged parent * process. */ void packet_get_keyiv(int mode, u_char *iv, u_int len) { CipherContext *cc; if (mode == MODE_OUT) cc = &send_context; else cc = &receive_context; cipher_get_keyiv(cc, iv, len); } int packet_get_keycontext(int mode, u_char *dat) { CipherContext *cc; if (mode == MODE_OUT) cc = &send_context; else cc = &receive_context; return (cipher_get_keycontext(cc, dat)); } void packet_set_keycontext(int mode, u_char *dat) { CipherContext *cc; if (mode == MODE_OUT) cc = &send_context; else cc = &receive_context; cipher_set_keycontext(cc, dat); } int packet_get_keyiv_len(int mode) { CipherContext *cc; if (mode == MODE_OUT) cc = &send_context; else cc = &receive_context; return (cipher_get_keyiv_len(cc)); } void packet_set_iv(int mode, u_char *dat) { CipherContext *cc; if (mode == MODE_OUT) cc = &send_context; else cc = &receive_context; cipher_set_keyiv(cc, dat); } int packet_get_ssh1_cipher(void) { return (cipher_get_number(receive_context.cipher)); } void packet_get_state(int mode, u_int32_t *seqnr, u_int64_t *blocks, u_int32_t *packets) { struct packet_state *state; state = (mode == MODE_IN) ? &p_read : &p_send; *seqnr = state->seqnr; *blocks = state->blocks; *packets = state->packets; } void packet_set_state(int mode, u_int32_t seqnr, u_int64_t blocks, u_int32_t packets) { struct packet_state *state; state = (mode == MODE_IN) ? &p_read : &p_send; state->seqnr = seqnr; state->blocks = blocks; state->packets = packets; } /* returns 1 if connection is via ipv4 */ int packet_connection_is_ipv4(void) { struct sockaddr_storage to; socklen_t tolen = sizeof(to); memset(&to, 0, sizeof(to)); if (getsockname(connection_out, (struct sockaddr *)&to, &tolen) < 0) return 0; if (to.ss_family == AF_INET) return 1; #ifdef IPV4_IN_IPV6 if (to.ss_family == AF_INET6 && IN6_IS_ADDR_V4MAPPED(&((struct sockaddr_in6 *)&to)->sin6_addr)) return 1; #endif return 0; } /* Sets the connection into non-blocking mode. */ void packet_set_nonblocking(void) { /* Set the socket into non-blocking mode. */ set_nonblock(connection_in); if (connection_out != connection_in) set_nonblock(connection_out); } /* Returns the socket used for reading. */ int packet_get_connection_in(void) { return connection_in; } /* Returns the descriptor used for writing. */ int packet_get_connection_out(void) { return connection_out; } /* Closes the connection and clears and frees internal data structures. */ void packet_close(void) { if (!initialized) return; initialized = 0; if (connection_in == connection_out) { shutdown(connection_out, SHUT_RDWR); close(connection_out); } else { close(connection_in); close(connection_out); } buffer_free(&input); buffer_free(&output); buffer_free(&outgoing_packet); buffer_free(&incoming_packet); if (compression_buffer_ready) { buffer_free(&compression_buffer); buffer_compress_uninit(); } cipher_cleanup(&send_context); cipher_cleanup(&receive_context); } /* Sets remote side protocol flags. */ void packet_set_protocol_flags(u_int protocol_flags) { remote_protocol_flags = protocol_flags; } /* Returns the remote protocol flags set earlier by the above function. */ u_int packet_get_protocol_flags(void) { return remote_protocol_flags; } /* * Starts packet compression from the next packet on in both directions. * Level is compression level 1 (fastest) - 9 (slow, best) as in gzip. */ static void packet_init_compression(void) { if (compression_buffer_ready == 1) return; compression_buffer_ready = 1; buffer_init(&compression_buffer); } void packet_start_compression(int level) { if (packet_compression && !compat20) fatal("Compression already enabled."); packet_compression = 1; packet_init_compression(); buffer_compress_init_send(level); buffer_compress_init_recv(); } /* * Causes any further packets to be encrypted using the given key. The same * key is used for both sending and reception. However, both directions are * encrypted independently of each other. */ void packet_set_encryption_key(const u_char *key, u_int keylen, int number) { Cipher *cipher = cipher_by_number(number); if (cipher == NULL) fatal("packet_set_encryption_key: unknown cipher number %d", number); if (keylen < 20) fatal("packet_set_encryption_key: keylen too small: %d", keylen); if (keylen > SSH_SESSION_KEY_LENGTH) fatal("packet_set_encryption_key: keylen too big: %d", keylen); memcpy(ssh1_key, key, keylen); ssh1_keylen = keylen; cipher_init(&send_context, cipher, key, keylen, NULL, 0, CIPHER_ENCRYPT); cipher_init(&receive_context, cipher, key, keylen, NULL, 0, CIPHER_DECRYPT); } u_int packet_get_encryption_key(u_char *key) { if (key == NULL) return (ssh1_keylen); memcpy(key, ssh1_key, ssh1_keylen); return (ssh1_keylen); } /* Start constructing a packet to send. */ void packet_start(u_char type) { u_char buf[9]; int len; DBG(debug("packet_start[%d]", type)); len = compat20 ? 6 : 9; memset(buf, 0, len - 1); buf[len - 1] = type; buffer_clear(&outgoing_packet); buffer_append(&outgoing_packet, buf, len); } /* Append payload. */ void packet_put_char(int value) { char ch = value; buffer_append(&outgoing_packet, &ch, 1); } void packet_put_int(u_int value) { buffer_put_int(&outgoing_packet, value); } void packet_put_string(const void *buf, u_int len) { buffer_put_string(&outgoing_packet, buf, len); } void packet_put_cstring(const char *str) { buffer_put_cstring(&outgoing_packet, str); } void packet_put_raw(const void *buf, u_int len) { buffer_append(&outgoing_packet, buf, len); } void packet_put_bignum(BIGNUM * value) { buffer_put_bignum(&outgoing_packet, value); } void packet_put_bignum2(BIGNUM * value) { buffer_put_bignum2(&outgoing_packet, value); } /* * Finalizes and sends the packet. If the encryption key has been set, * encrypts the packet before sending. */ static void packet_send1(void) { u_char buf[8], *cp; int i, padding, len; u_int checksum; u_int32_t rnd = 0; /* * If using packet compression, compress the payload of the outgoing * packet. */ if (packet_compression) { buffer_clear(&compression_buffer); /* Skip padding. */ buffer_consume(&outgoing_packet, 8); /* padding */ buffer_append(&compression_buffer, "\0\0\0\0\0\0\0\0", 8); buffer_compress(&outgoing_packet, &compression_buffer); buffer_clear(&outgoing_packet); buffer_append(&outgoing_packet, buffer_ptr(&compression_buffer), buffer_len(&compression_buffer)); } /* Compute packet length without padding (add checksum, remove padding). */ len = buffer_len(&outgoing_packet) + 4 - 8; /* Insert padding. Initialized to zero in packet_start1() */ padding = 8 - len % 8; if (!send_context.plaintext) { cp = buffer_ptr(&outgoing_packet); for (i = 0; i < padding; i++) { if (i % 4 == 0) rnd = arc4random(); cp[7 - i] = rnd & 0xff; rnd >>= 8; } } buffer_consume(&outgoing_packet, 8 - padding); /* Add check bytes. */ checksum = ssh_crc32(buffer_ptr(&outgoing_packet), buffer_len(&outgoing_packet)); PUT_32BIT(buf, checksum); buffer_append(&outgoing_packet, buf, 4); #ifdef PACKET_DEBUG fprintf(stderr, "packet_send plain: "); buffer_dump(&outgoing_packet); #endif /* Append to output. */ PUT_32BIT(buf, len); buffer_append(&output, buf, 4); cp = buffer_append_space(&output, buffer_len(&outgoing_packet)); cipher_crypt(&send_context, cp, buffer_ptr(&outgoing_packet), buffer_len(&outgoing_packet)); #ifdef PACKET_DEBUG fprintf(stderr, "encrypted: "); buffer_dump(&output); #endif buffer_clear(&outgoing_packet); /* * Note that the packet is now only buffered in output. It won\'t be * actually sent until packet_write_wait or packet_write_poll is * called. */ } void set_newkeys(int mode) { Enc *enc; Mac *mac; Comp *comp; CipherContext *cc; u_int64_t *max_blocks; int crypt_type; debug2("set_newkeys: mode %d", mode); if (mode == MODE_OUT) { cc = &send_context; crypt_type = CIPHER_ENCRYPT; p_send.packets = p_send.blocks = 0; max_blocks = &max_blocks_out; } else { cc = &receive_context; crypt_type = CIPHER_DECRYPT; p_read.packets = p_read.blocks = 0; max_blocks = &max_blocks_in; } if (newkeys[mode] != NULL) { debug("set_newkeys: rekeying"); cipher_cleanup(cc); enc = &newkeys[mode]->enc; mac = &newkeys[mode]->mac; comp = &newkeys[mode]->comp; memset(mac->key, 0, mac->key_len); xfree(enc->name); xfree(enc->iv); xfree(enc->key); xfree(mac->name); xfree(mac->key); xfree(comp->name); xfree(newkeys[mode]); } newkeys[mode] = kex_get_newkeys(mode); if (newkeys[mode] == NULL) fatal("newkeys: no keys for mode %d", mode); enc = &newkeys[mode]->enc; mac = &newkeys[mode]->mac; comp = &newkeys[mode]->comp; if (mac->md != NULL) mac->enabled = 1; DBG(debug("cipher_init_context: %d", mode)); cipher_init(cc, enc->cipher, enc->key, enc->key_len, enc->iv, enc->block_size, crypt_type); /* Deleting the keys does not gain extra security */ /* memset(enc->iv, 0, enc->block_size); memset(enc->key, 0, enc->key_len); */ if (comp->type != 0 && comp->enabled == 0) { packet_init_compression(); if (mode == MODE_OUT) buffer_compress_init_send(6); else buffer_compress_init_recv(); comp->enabled = 1; } /* * The 2^(blocksize*2) limit is too expensive for 3DES, * blowfish, etc, so enforce a 1GB limit for small blocksizes. */ if (enc->block_size >= 16) *max_blocks = (u_int64_t)1 << (enc->block_size*2); else *max_blocks = ((u_int64_t)1 << 30) / enc->block_size; if (rekey_limit) *max_blocks = MIN(*max_blocks, rekey_limit / enc->block_size); } /* * Finalize packet in SSH2 format (compress, mac, encrypt, enqueue) */ static void packet_send2_wrapped(void) { u_char type, *cp, *macbuf = NULL; u_char padlen, pad; u_int packet_length = 0; u_int i, len; u_int32_t rnd = 0; Enc *enc = NULL; Mac *mac = NULL; Comp *comp = NULL; int block_size; if (newkeys[MODE_OUT] != NULL) { enc = &newkeys[MODE_OUT]->enc; mac = &newkeys[MODE_OUT]->mac; comp = &newkeys[MODE_OUT]->comp; } block_size = enc ? enc->block_size : 8; cp = buffer_ptr(&outgoing_packet); type = cp[5]; #ifdef PACKET_DEBUG fprintf(stderr, "plain: "); buffer_dump(&outgoing_packet); #endif if (comp && comp->enabled) { len = buffer_len(&outgoing_packet); /* skip header, compress only payload */ buffer_consume(&outgoing_packet, 5); buffer_clear(&compression_buffer); buffer_compress(&outgoing_packet, &compression_buffer); buffer_clear(&outgoing_packet); buffer_append(&outgoing_packet, "\0\0\0\0\0", 5); buffer_append(&outgoing_packet, buffer_ptr(&compression_buffer), buffer_len(&compression_buffer)); DBG(debug("compression: raw %d compressed %d", len, buffer_len(&outgoing_packet))); } /* sizeof (packet_len + pad_len + payload) */ len = buffer_len(&outgoing_packet); /* * calc size of padding, alloc space, get random data, * minimum padding is 4 bytes */ padlen = block_size - (len % block_size); if (padlen < 4) padlen += block_size; if (extra_pad) { /* will wrap if extra_pad+padlen > 255 */ extra_pad = roundup(extra_pad, block_size); pad = extra_pad - ((len + padlen) % extra_pad); debug3("packet_send2: adding %d (len %d padlen %d extra_pad %d)", pad, len, padlen, extra_pad); padlen += pad; extra_pad = 0; } cp = buffer_append_space(&outgoing_packet, padlen); if (enc && !send_context.plaintext) { /* random padding */ for (i = 0; i < padlen; i++) { if (i % 4 == 0) rnd = arc4random(); cp[i] = rnd & 0xff; rnd >>= 8; } } else { /* clear padding */ memset(cp, 0, padlen); } /* packet_length includes payload, padding and padding length field */ packet_length = buffer_len(&outgoing_packet) - 4; cp = buffer_ptr(&outgoing_packet); PUT_32BIT(cp, packet_length); cp[4] = padlen; DBG(debug("send: len %d (includes padlen %d)", packet_length+4, padlen)); /* compute MAC over seqnr and packet(length fields, payload, padding) */ if (mac && mac->enabled) { macbuf = mac_compute(mac, p_send.seqnr, buffer_ptr(&outgoing_packet), buffer_len(&outgoing_packet)); DBG(debug("done calc MAC out #%d", p_send.seqnr)); } /* encrypt packet and append to output buffer. */ cp = buffer_append_space(&output, buffer_len(&outgoing_packet)); cipher_crypt(&send_context, cp, buffer_ptr(&outgoing_packet), buffer_len(&outgoing_packet)); /* append unencrypted MAC */ if (mac && mac->enabled) buffer_append(&output, (char *)macbuf, mac->mac_len); #ifdef PACKET_DEBUG fprintf(stderr, "encrypted: "); buffer_dump(&output); #endif /* increment sequence number for outgoing packets */ if (++p_send.seqnr == 0) logit("outgoing seqnr wraps around"); if (++p_send.packets == 0) if (!(datafellows & SSH_BUG_NOREKEY)) fatal("XXX too many packets with same key"); p_send.blocks += (packet_length + 4) / block_size; buffer_clear(&outgoing_packet); if (type == SSH2_MSG_NEWKEYS) set_newkeys(MODE_OUT); } static void packet_send2(void) { static int rekeying = 0; struct packet *p; u_char type, *cp; cp = buffer_ptr(&outgoing_packet); type = cp[5]; /* during rekeying we can only send key exchange messages */ if (rekeying) { if (!((type >= SSH2_MSG_TRANSPORT_MIN) && (type <= SSH2_MSG_TRANSPORT_MAX))) { debug("enqueue packet: %u", type); p = xmalloc(sizeof(*p)); p->type = type; memcpy(&p->payload, &outgoing_packet, sizeof(Buffer)); buffer_init(&outgoing_packet); TAILQ_INSERT_TAIL(&outgoing, p, next); return; } } /* rekeying starts with sending KEXINIT */ if (type == SSH2_MSG_KEXINIT) rekeying = 1; packet_send2_wrapped(); /* after a NEWKEYS message we can send the complete queue */ if (type == SSH2_MSG_NEWKEYS) { rekeying = 0; while ((p = TAILQ_FIRST(&outgoing))) { type = p->type; debug("dequeue packet: %u", type); buffer_free(&outgoing_packet); memcpy(&outgoing_packet, &p->payload, sizeof(Buffer)); TAILQ_REMOVE(&outgoing, p, next); xfree(p); packet_send2_wrapped(); } } } void packet_send(void) { if (compat20) packet_send2(); else packet_send1(); DBG(debug("packet_send done")); } /* * Waits until a packet has been received, and returns its type. Note that * no other data is processed until this returns, so this function should not * be used during the interactive session. */ int packet_read_seqnr(u_int32_t *seqnr_p) { int type, len; fd_set *setp; char buf[8192]; DBG(debug("packet_read()")); setp = (fd_set *)xmalloc(howmany(connection_in+1, NFDBITS) * sizeof(fd_mask)); /* Since we are blocking, ensure that all written packets have been sent. */ packet_write_wait(); /* Stay in the loop until we have received a complete packet. */ for (;;) { /* Try to read a packet from the buffer. */ type = packet_read_poll_seqnr(seqnr_p); if (!compat20 && ( type == SSH_SMSG_SUCCESS || type == SSH_SMSG_FAILURE || type == SSH_CMSG_EOF || type == SSH_CMSG_EXIT_CONFIRMATION)) packet_check_eom(); /* If we got a packet, return it. */ if (type != SSH_MSG_NONE) { xfree(setp); return type; } /* * Otherwise, wait for some data to arrive, add it to the * buffer, and try again. */ memset(setp, 0, howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask)); FD_SET(connection_in, setp); /* Wait for some data to arrive. */ while (select(connection_in + 1, setp, NULL, NULL, NULL) == -1 && (errno == EAGAIN || errno == EINTR)) ; /* Read data from the socket. */ len = read(connection_in, buf, sizeof(buf)); if (len == 0) { logit("Connection closed by %.200s", get_remote_ipaddr()); cleanup_exit(255); } if (len < 0) fatal("Read from socket failed: %.100s", strerror(errno)); /* Append it to the buffer. */ packet_process_incoming(buf, len); } /* NOTREACHED */ } int packet_read(void) { return packet_read_seqnr(NULL); } /* * Waits until a packet has been received, verifies that its type matches * that given, and gives a fatal error and exits if there is a mismatch. */ void packet_read_expect(int expected_type) { int type; type = packet_read(); if (type != expected_type) packet_disconnect("Protocol error: expected packet type %d, got %d", expected_type, type); } /* Checks if a full packet is available in the data received so far via * packet_process_incoming. If so, reads the packet; otherwise returns * SSH_MSG_NONE. This does not wait for data from the connection. * * SSH_MSG_DISCONNECT is handled specially here. Also, * SSH_MSG_IGNORE messages are skipped by this function and are never returned * to higher levels. */ static int packet_read_poll1(void) { u_int len, padded_len; u_char *cp, type; u_int checksum, stored_checksum; /* Check if input size is less than minimum packet size. */ if (buffer_len(&input) < 4 + 8) return SSH_MSG_NONE; /* Get length of incoming packet. */ cp = buffer_ptr(&input); len = GET_32BIT(cp); if (len < 1 + 2 + 2 || len > 256 * 1024) packet_disconnect("Bad packet length %u.", len); padded_len = (len + 8) & ~7; /* Check if the packet has been entirely received. */ if (buffer_len(&input) < 4 + padded_len) return SSH_MSG_NONE; /* The entire packet is in buffer. */ /* Consume packet length. */ buffer_consume(&input, 4); /* * Cryptographic attack detector for ssh * (C)1998 CORE-SDI, Buenos Aires Argentina * Ariel Futoransky(futo@core-sdi.com) */ if (!receive_context.plaintext && detect_attack(buffer_ptr(&input), padded_len, NULL) == DEATTACK_DETECTED) packet_disconnect("crc32 compensation attack: network attack detected"); /* Decrypt data to incoming_packet. */ buffer_clear(&incoming_packet); cp = buffer_append_space(&incoming_packet, padded_len); cipher_crypt(&receive_context, cp, buffer_ptr(&input), padded_len); buffer_consume(&input, padded_len); #ifdef PACKET_DEBUG fprintf(stderr, "read_poll plain: "); buffer_dump(&incoming_packet); #endif /* Compute packet checksum. */ checksum = ssh_crc32(buffer_ptr(&incoming_packet), buffer_len(&incoming_packet) - 4); /* Skip padding. */ buffer_consume(&incoming_packet, 8 - len % 8); /* Test check bytes. */ if (len != buffer_len(&incoming_packet)) packet_disconnect("packet_read_poll1: len %d != buffer_len %d.", len, buffer_len(&incoming_packet)); cp = (u_char *)buffer_ptr(&incoming_packet) + len - 4; stored_checksum = GET_32BIT(cp); if (checksum != stored_checksum) packet_disconnect("Corrupted check bytes on input."); buffer_consume_end(&incoming_packet, 4); if (packet_compression) { buffer_clear(&compression_buffer); buffer_uncompress(&incoming_packet, &compression_buffer); buffer_clear(&incoming_packet); buffer_append(&incoming_packet, buffer_ptr(&compression_buffer), buffer_len(&compression_buffer)); } type = buffer_get_char(&incoming_packet); return type; } static int packet_read_poll2(u_int32_t *seqnr_p) { static u_int packet_length = 0; u_int padlen, need; u_char *macbuf, *cp, type; int maclen, block_size; Enc *enc = NULL; Mac *mac = NULL; Comp *comp = NULL; if (newkeys[MODE_IN] != NULL) { enc = &newkeys[MODE_IN]->enc; mac = &newkeys[MODE_IN]->mac; comp = &newkeys[MODE_IN]->comp; } maclen = mac && mac->enabled ? mac->mac_len : 0; block_size = enc ? enc->block_size : 8; if (packet_length == 0) { /* * check if input size is less than the cipher block size, * decrypt first block and extract length of incoming packet */ if (buffer_len(&input) < block_size) return SSH_MSG_NONE; buffer_clear(&incoming_packet); cp = buffer_append_space(&incoming_packet, block_size); cipher_crypt(&receive_context, cp, buffer_ptr(&input), block_size); cp = buffer_ptr(&incoming_packet); packet_length = GET_32BIT(cp); if (packet_length < 1 + 4 || packet_length > 256 * 1024) { #ifdef PACKET_DEBUG buffer_dump(&incoming_packet); #endif packet_disconnect("Bad packet length %u.", packet_length); } DBG(debug("input: packet len %u", packet_length+4)); buffer_consume(&input, block_size); } /* we have a partial packet of block_size bytes */ need = 4 + packet_length - block_size; DBG(debug("partial packet %d, need %d, maclen %d", block_size, need, maclen)); if (need % block_size != 0) fatal("padding error: need %d block %d mod %d", need, block_size, need % block_size); /* * check if the entire packet has been received and * decrypt into incoming_packet */ if (buffer_len(&input) < need + maclen) return SSH_MSG_NONE; #ifdef PACKET_DEBUG fprintf(stderr, "read_poll enc/full: "); buffer_dump(&input); #endif cp = buffer_append_space(&incoming_packet, need); cipher_crypt(&receive_context, cp, buffer_ptr(&input), need); buffer_consume(&input, need); /* * compute MAC over seqnr and packet, * increment sequence number for incoming packet */ if (mac && mac->enabled) { macbuf = mac_compute(mac, p_read.seqnr, buffer_ptr(&incoming_packet), buffer_len(&incoming_packet)); if (memcmp(macbuf, buffer_ptr(&input), mac->mac_len) != 0) packet_disconnect("Corrupted MAC on input."); DBG(debug("MAC #%d ok", p_read.seqnr)); buffer_consume(&input, mac->mac_len); } if (seqnr_p != NULL) *seqnr_p = p_read.seqnr; if (++p_read.seqnr == 0) logit("incoming seqnr wraps around"); if (++p_read.packets == 0) if (!(datafellows & SSH_BUG_NOREKEY)) fatal("XXX too many packets with same key"); p_read.blocks += (packet_length + 4) / block_size; /* get padlen */ cp = buffer_ptr(&incoming_packet); padlen = cp[4]; DBG(debug("input: padlen %d", padlen)); if (padlen < 4) packet_disconnect("Corrupted padlen %d on input.", padlen); /* skip packet size + padlen, discard padding */ buffer_consume(&incoming_packet, 4 + 1); buffer_consume_end(&incoming_packet, padlen); DBG(debug("input: len before de-compress %d", buffer_len(&incoming_packet))); if (comp && comp->enabled) { buffer_clear(&compression_buffer); buffer_uncompress(&incoming_packet, &compression_buffer); buffer_clear(&incoming_packet); buffer_append(&incoming_packet, buffer_ptr(&compression_buffer), buffer_len(&compression_buffer)); DBG(debug("input: len after de-compress %d", buffer_len(&incoming_packet))); } /* * get packet type, implies consume. * return length of payload (without type field) */ type = buffer_get_char(&incoming_packet); if (type == SSH2_MSG_NEWKEYS) set_newkeys(MODE_IN); #ifdef PACKET_DEBUG fprintf(stderr, "read/plain[%d]:\r\n", type); buffer_dump(&incoming_packet); #endif /* reset for next packet */ packet_length = 0; return type; } int packet_read_poll_seqnr(u_int32_t *seqnr_p) { u_int reason, seqnr; u_char type; char *msg; for (;;) { if (compat20) { type = packet_read_poll2(seqnr_p); if (type) DBG(debug("received packet type %d", type)); switch (type) { case SSH2_MSG_IGNORE: break; case SSH2_MSG_DEBUG: packet_get_char(); msg = packet_get_string(NULL); debug("Remote: %.900s", msg); xfree(msg); msg = packet_get_string(NULL); xfree(msg); break; case SSH2_MSG_DISCONNECT: reason = packet_get_int(); msg = packet_get_string(NULL); logit("Received disconnect from %s: %u: %.400s", get_remote_ipaddr(), reason, msg); xfree(msg); cleanup_exit(255); break; case SSH2_MSG_UNIMPLEMENTED: seqnr = packet_get_int(); debug("Received SSH2_MSG_UNIMPLEMENTED for %u", seqnr); break; default: return type; break; } } else { type = packet_read_poll1(); switch (type) { case SSH_MSG_IGNORE: break; case SSH_MSG_DEBUG: msg = packet_get_string(NULL); debug("Remote: %.900s", msg); xfree(msg); break; case SSH_MSG_DISCONNECT: msg = packet_get_string(NULL); logit("Received disconnect from %s: %.400s", get_remote_ipaddr(), msg); cleanup_exit(255); xfree(msg); break; default: if (type) DBG(debug("received packet type %d", type)); return type; break; } } } } int packet_read_poll(void) { return packet_read_poll_seqnr(NULL); } /* * Buffers the given amount of input characters. This is intended to be used * together with packet_read_poll. */ void packet_process_incoming(const char *buf, u_int len) { buffer_append(&input, buf, len); } /* Returns a character from the packet. */ u_int packet_get_char(void) { char ch; buffer_get(&incoming_packet, &ch, 1); return (u_char) ch; } /* Returns an integer from the packet data. */ u_int packet_get_int(void) { return buffer_get_int(&incoming_packet); } /* * Returns an arbitrary precision integer from the packet data. The integer * must have been initialized before this call. */ void packet_get_bignum(BIGNUM * value) { buffer_get_bignum(&incoming_packet, value); } void packet_get_bignum2(BIGNUM * value) { buffer_get_bignum2(&incoming_packet, value); } void * packet_get_raw(int *length_ptr) { int bytes = buffer_len(&incoming_packet); if (length_ptr != NULL) *length_ptr = bytes; return buffer_ptr(&incoming_packet); } int packet_remaining(void) { return buffer_len(&incoming_packet); } /* * Returns a string from the packet data. The string is allocated using * xmalloc; it is the responsibility of the calling program to free it when * no longer needed. The length_ptr argument may be NULL, or point to an * integer into which the length of the string is stored. */ void * packet_get_string(u_int *length_ptr) { return buffer_get_string(&incoming_packet, length_ptr); } /* * Sends a diagnostic message from the server to the client. This message * can be sent at any time (but not while constructing another message). The * message is printed immediately, but only if the client is being executed * in verbose mode. These messages are primarily intended to ease debugging * authentication problems. The length of the formatted message must not * exceed 1024 bytes. This will automatically call packet_write_wait. */ void packet_send_debug(const char *fmt,...) { char buf[1024]; va_list args; if (compat20 && (datafellows & SSH_BUG_DEBUG)) return; va_start(args, fmt); vsnprintf(buf, sizeof(buf), fmt, args); va_end(args); if (compat20) { packet_start(SSH2_MSG_DEBUG); packet_put_char(0); /* bool: always display */ packet_put_cstring(buf); packet_put_cstring(""); } else { packet_start(SSH_MSG_DEBUG); packet_put_cstring(buf); } packet_send(); packet_write_wait(); } /* * Logs the error plus constructs and sends a disconnect packet, closes the * connection, and exits. This function never returns. The error message * should not contain a newline. The length of the formatted message must * not exceed 1024 bytes. */ void packet_disconnect(const char *fmt,...) { char buf[1024]; va_list args; static int disconnecting = 0; if (disconnecting) /* Guard against recursive invocations. */ fatal("packet_disconnect called recursively."); disconnecting = 1; /* * Format the message. Note that the caller must make sure the * message is of limited size. */ va_start(args, fmt); vsnprintf(buf, sizeof(buf), fmt, args); va_end(args); /* Display the error locally */ logit("Disconnecting: %.100s", buf); /* Send the disconnect message to the other side, and wait for it to get sent. */ if (compat20) { packet_start(SSH2_MSG_DISCONNECT); packet_put_int(SSH2_DISCONNECT_PROTOCOL_ERROR); packet_put_cstring(buf); packet_put_cstring(""); } else { packet_start(SSH_MSG_DISCONNECT); packet_put_cstring(buf); } packet_send(); packet_write_wait(); /* Stop listening for connections. */ channel_close_all(); /* Close the connection. */ packet_close(); cleanup_exit(255); } /* Checks if there is any buffered output, and tries to write some of the output. */ void packet_write_poll(void) { int len = buffer_len(&output); if (len > 0) { len = write(connection_out, buffer_ptr(&output), len); if (len <= 0) { if (errno == EAGAIN) return; else fatal("Write failed: %.100s", strerror(errno)); } buffer_consume(&output, len); } } /* * Calls packet_write_poll repeatedly until all pending output data has been * written. */ void packet_write_wait(void) { fd_set *setp; setp = (fd_set *)xmalloc(howmany(connection_out + 1, NFDBITS) * sizeof(fd_mask)); packet_write_poll(); while (packet_have_data_to_write()) { memset(setp, 0, howmany(connection_out + 1, NFDBITS) * sizeof(fd_mask)); FD_SET(connection_out, setp); while (select(connection_out + 1, NULL, setp, NULL, NULL) == -1 && (errno == EAGAIN || errno == EINTR)) ; packet_write_poll(); } xfree(setp); } /* Returns true if there is buffered data to write to the connection. */ int packet_have_data_to_write(void) { return buffer_len(&output) != 0; } /* Returns true if there is not too much data to write to the connection. */ int packet_not_very_much_data_to_write(void) { if (interactive_mode) return buffer_len(&output) < 16384; else return buffer_len(&output) < 128 * 1024; } static void packet_set_tos(int interactive) { #if defined(IP_TOS) && !defined(IP_TOS_IS_BROKEN) int tos = interactive ? IPTOS_LOWDELAY : IPTOS_THROUGHPUT; if (!packet_connection_is_on_socket() || !packet_connection_is_ipv4()) return; if (setsockopt(connection_in, IPPROTO_IP, IP_TOS, &tos, sizeof(tos)) < 0) error("setsockopt IP_TOS %d: %.100s:", tos, strerror(errno)); #endif } /* Informs that the current session is interactive. Sets IP flags for that. */ void packet_set_interactive(int interactive) { static int called = 0; if (called) return; called = 1; /* Record that we are in interactive mode. */ interactive_mode = interactive; /* Only set socket options if using a socket. */ if (!packet_connection_is_on_socket()) return; if (interactive) set_nodelay(connection_in); packet_set_tos(interactive); } /* Returns true if the current connection is interactive. */ int packet_is_interactive(void) { return interactive_mode; } int packet_set_maxsize(u_int s) { static int called = 0; if (called) { logit("packet_set_maxsize: called twice: old %d new %d", max_packet_size, s); return -1; } if (s < 4 * 1024 || s > 1024 * 1024) { logit("packet_set_maxsize: bad size %d", s); return -1; } called = 1; debug("packet_set_maxsize: setting to %d", s); max_packet_size = s; return s; } /* roundup current message to pad bytes */ void packet_add_padding(u_char pad) { extra_pad = pad; } /* * 9.2. Ignored Data Message * * byte SSH_MSG_IGNORE * string data * * All implementations MUST understand (and ignore) this message at any * time (after receiving the protocol version). No implementation is * required to send them. This message can be used as an additional * protection measure against advanced traffic analysis techniques. */ void packet_send_ignore(int nbytes) { u_int32_t rnd = 0; int i; packet_start(compat20 ? SSH2_MSG_IGNORE : SSH_MSG_IGNORE); packet_put_int(nbytes); for (i = 0; i < nbytes; i++) { if (i % 4 == 0) rnd = arc4random(); packet_put_char(rnd & 0xff); rnd >>= 8; } } #define MAX_PACKETS (1U<<31) int packet_need_rekeying(void) { if (datafellows & SSH_BUG_NOREKEY) return 0; return (p_send.packets > MAX_PACKETS) || (p_read.packets > MAX_PACKETS) || (max_blocks_out && (p_send.blocks > max_blocks_out)) || (max_blocks_in && (p_read.blocks > max_blocks_in)); } void packet_set_rekey_limit(u_int32_t bytes) { rekey_limit = bytes; }