From b9bf0f52e3f48ce963057fcf62b9f1fe4a0ec921 Mon Sep 17 00:00:00 2001 From: markus Date: Mon, 3 Apr 2000 20:12:55 +0000 Subject: [PATCH] ssh2 packet format --- usr.bin/ssh/packet.c | 482 +++++++++++++++++++++++++++++++++++++++---- usr.bin/ssh/packet.h | 7 +- 2 files changed, 443 insertions(+), 46 deletions(-) diff --git a/usr.bin/ssh/packet.c b/usr.bin/ssh/packet.c index 901b2ed606e..9925f7595dd 100644 --- a/usr.bin/ssh/packet.c +++ b/usr.bin/ssh/packet.c @@ -11,11 +11,13 @@ * * 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. - * + * + * SSH2 packet format added by Markus Friedl. + * */ #include "includes.h" -RCSID("$Id: packet.c,v 1.24 2000/04/03 07:07:15 markus Exp $"); +RCSID("$Id: packet.c,v 1.25 2000/04/03 20:12:55 markus Exp $"); #include "xmalloc.h" #include "buffer.h" @@ -30,6 +32,22 @@ RCSID("$Id: packet.c,v 1.24 2000/04/03 07:07:15 markus Exp $"); #include "deattack.h" #include "channels.h" +#include "compat.h" +#include "ssh2.h" + +#include +#include +#include +#include "buffer.h" +#include "kex.h" +#include "hmac.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 @@ -81,11 +99,45 @@ static int initialized = 0; /* Set to true if the connection is interactive. */ static int interactive_mode = 0; +/* True if SSH2 packet format is used */ +int use_ssh2_packet_format = 0; + +/* Session key information for Encryption and MAC */ +Kex *kex = NULL; + +void +packet_set_kex(Kex *k) +{ + if( k->mac[MODE_IN ].key == NULL || + k->enc[MODE_IN ].key == NULL || + k->enc[MODE_IN ].iv == NULL || + k->mac[MODE_OUT].key == NULL || + k->enc[MODE_OUT].key == NULL || + k->enc[MODE_OUT].iv == NULL) + fatal("bad KEX"); + kex = k; +} +void +clear_enc_keys(Enc *enc, int len) +{ + memset(enc->iv, 0, len); + memset(enc->key, 0, len); + xfree(enc->iv); + xfree(enc->key); + enc->iv = NULL; + enc->key = NULL; +} +void +packet_set_ssh2_format(void) +{ + debug("use_ssh2_packet_format"); + use_ssh2_packet_format = 1; +} + /* * 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) { @@ -225,6 +277,7 @@ packet_get_protocol_flags() * Level is compression level 1 (fastest) - 9 (slow, best) as in gzip. */ +/*** XXXXX todo: kex means re-init */ void packet_start_compression(int level) { @@ -242,7 +295,7 @@ packet_start_compression(int level) void packet_encrypt(CipherContext * cc, void *dest, void *src, - unsigned int bytes) + unsigned int bytes) { cipher_encrypt(cc, dest, src, bytes); } @@ -254,7 +307,7 @@ packet_encrypt(CipherContext * cc, void *dest, void *src, void packet_decrypt(CipherContext * cc, void *dest, void *src, - unsigned int bytes) + unsigned int bytes) { int i; @@ -266,15 +319,11 @@ packet_decrypt(CipherContext * cc, void *dest, void *src, * (C)1998 CORE-SDI, Buenos Aires Argentina Ariel Futoransky(futo@core-sdi.com) */ - switch (cc->type) { - case SSH_CIPHER_NONE: + if (cc->type == SSH_CIPHER_NONE || compat20) { i = DEATTACK_OK; - break; - default: + } else { i = detect_attack(src, bytes, NULL); - break; } - if (i == DEATTACK_DETECTED) packet_disconnect("crc32 compensation attack: network attack detected"); @@ -289,8 +338,11 @@ packet_decrypt(CipherContext * cc, void *dest, void *src, void packet_set_encryption_key(const unsigned char *key, unsigned int keylen, - int cipher) + int cipher) { + if (keylen < 20) + fatal("keylen too small: %d", keylen); + /* All other ciphers use the same key in both directions for now. */ cipher_set_key(&receive_context, cipher, key, keylen, 0); cipher_set_key(&send_context, cipher, key, keylen, 1); @@ -299,7 +351,7 @@ packet_set_encryption_key(const unsigned char *key, unsigned int keylen, /* Starts constructing a packet to send. */ void -packet_start(int type) +packet_start1(int type) { char buf[9]; @@ -309,6 +361,29 @@ packet_start(int type) buffer_append(&outgoing_packet, buf, 9); } +void +packet_start2(int type) +{ + char buf[4+1+1]; + + buffer_clear(&outgoing_packet); + memset(buf, 0, sizeof buf); + /* buf[0..3] = payload_len; */ + /* buf[4] = pad_len; */ + buf[5] = type & 0xff; + buffer_append(&outgoing_packet, buf, sizeof buf); +} + +void +packet_start(int type) +{ + DBG(debug("packet_start[%d]",type)); + if (use_ssh2_packet_format) + packet_start2(type); + else + packet_start1(type); +} + /* Appends a character to the packet data. */ void @@ -365,7 +440,7 @@ packet_put_bignum2(BIGNUM * value) */ void -packet_send() +packet_send1() { char buf[8], *cp; int i, padding, len; @@ -435,6 +510,139 @@ packet_send() */ } +/* + * Finalize packet in SSH2 format (compress, mac, encrypt, enqueue) + */ +void +packet_send2() +{ + unsigned char *macbuf = NULL; + char *cp; + unsigned int packet_length = 0; + unsigned int i, padlen, len; + u_int32_t rand = 0; + static unsigned int seqnr = 0; + int type; + Enc *enc = NULL; + Mac *mac = NULL; + Comp *comp = NULL; + int block_size; + + if (kex != NULL) { + enc = &kex->enc[MODE_OUT]; + mac = &kex->mac[MODE_OUT]; + comp = &kex->comp[MODE_OUT]; + } + block_size = enc ? enc->block_size : 8; + + cp = buffer_ptr(&outgoing_packet); + type = cp[5] & 0xff; + +#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; + buffer_append_space(&outgoing_packet, &cp, padlen); + if (enc && enc->type != SSH_CIPHER_NONE) { + for (i = 0; i < padlen; i++) { + if (i % 4 == 0) + rand = arc4random(); + cp[i] = rand & 0xff; + rand <<= 8; + } + } + /* 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 & 0xff; + 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 = hmac( mac->md, seqnr, + (unsigned char *) buffer_ptr(&outgoing_packet), + buffer_len(&outgoing_packet), + mac->key, mac->key_len + ); + DBG(debug("done calc HMAC out #%d", seqnr)); + } + /* encrypt packet and append to output buffer. */ + buffer_append_space(&output, &cp, buffer_len(&outgoing_packet)); + packet_encrypt(&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 (++seqnr == 0) + log("outgoing seqnr wraps around"); + buffer_clear(&outgoing_packet); + + if (type == SSH2_MSG_NEWKEYS) { + if (kex==NULL || mac==NULL || enc==NULL || comp==NULL) + fatal("packet_send2: no KEX"); + if (mac->md != NULL) + mac->enabled = 1; + debug("cipher_set_key_iv send_context"); + cipher_set_key_iv(&send_context, enc->type, + enc->key, enc->key_len, + enc->iv, enc->iv_len); + clear_enc_keys(enc, kex->we_need); + if (comp->type != 0 && comp->enabled == 0) { + comp->enabled = 1; + if (! packet_compression) + packet_start_compression(6); + } + } +} + +void +packet_send() +{ + if (use_ssh2_packet_format) + packet_send2(); + else + packet_send1(); + DBG(debug("packet_send done")); +} + +void +packet_send_and_wait() +{ + packet_send(); + packet_write_wait(); +} + /* * 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 @@ -447,6 +655,7 @@ packet_read(int *payload_len_ptr) int type, len; fd_set set; char buf[8192]; + DBG(debug("packet_read()")); /* Since we are blocking, ensure that all written packets have been sent. */ packet_write_wait(); @@ -500,7 +709,7 @@ packet_read_expect(int *payload_len_ptr, int expected_type) type = packet_read(payload_len_ptr); if (type != expected_type) packet_disconnect("Protocol error: expected packet type %d, got %d", - expected_type, type); + expected_type, type); } /* Checks if a full packet is available in the data received so far via @@ -519,15 +728,13 @@ packet_read_expect(int *payload_len_ptr, int expected_type) */ int -packet_read_poll(int *payload_len_ptr) +packet_read_poll1(int *payload_len_ptr) { unsigned int len, padded_len; unsigned char *ucp; - char buf[8], *cp, *msg; + char buf[8], *cp; unsigned int checksum, stored_checksum; -restart: - /* Check if input size is less than minimum packet size. */ if (buffer_len(&input) < 4 + 8) return SSH_MSG_NONE; @@ -560,7 +767,7 @@ restart: /* Compute packet checksum. */ checksum = crc32((unsigned char *) buffer_ptr(&incoming_packet), - buffer_len(&incoming_packet) - 4); + buffer_len(&incoming_packet) - 4); /* Skip padding. */ buffer_consume(&incoming_packet, 8 - len % 8); @@ -569,7 +776,7 @@ restart: if (len != buffer_len(&incoming_packet)) packet_disconnect("packet_read_poll: len %d != buffer_len %d.", - len, buffer_len(&incoming_packet)); + len, buffer_len(&incoming_packet)); ucp = (unsigned char *) buffer_ptr(&incoming_packet) + len - 4; stored_checksum = GET_32BIT(ucp); @@ -583,7 +790,7 @@ restart: buffer_uncompress(&incoming_packet, &compression_buffer); buffer_clear(&incoming_packet); buffer_append(&incoming_packet, buffer_ptr(&compression_buffer), - buffer_len(&compression_buffer)); + buffer_len(&compression_buffer)); } /* Get packet type. */ buffer_get(&incoming_packet, &buf[0], 1); @@ -591,29 +798,208 @@ restart: /* Return length of payload (without type field). */ *payload_len_ptr = buffer_len(&incoming_packet); - /* Handle disconnect message. */ - if ((unsigned char) buf[0] == SSH_MSG_DISCONNECT) { - msg = packet_get_string(NULL); - log("Received disconnect: %.900s", msg); - xfree(msg); - fatal_cleanup(); - } - - /* Ignore ignore messages. */ - if ((unsigned char) buf[0] == SSH_MSG_IGNORE) - goto restart; - - /* Send debug messages as debugging output. */ - if ((unsigned char) buf[0] == SSH_MSG_DEBUG) { - msg = packet_get_string(NULL); - debug("Remote: %.900s", msg); - xfree(msg); - goto restart; - } /* Return type. */ return (unsigned char) buf[0]; } +int +packet_read_poll2(int *payload_len_ptr) +{ + unsigned int padlen, need; + unsigned char buf[8], *macbuf; + unsigned char *ucp; + char *cp; + static unsigned int packet_length = 0; + static unsigned int seqnr = 0; + int type; + int maclen, block_size; + Enc *enc = NULL; + Mac *mac = NULL; + Comp *comp = NULL; + + if (kex != NULL) { + enc = &kex->enc[MODE_IN]; + mac = &kex->mac[MODE_IN]; + comp = &kex->comp[MODE_IN]; + } + 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); + buffer_append_space(&incoming_packet, &cp, block_size); + packet_decrypt(&receive_context, cp, buffer_ptr(&input), + block_size); + ucp = (unsigned char *) buffer_ptr(&incoming_packet); + packet_length = GET_32BIT(ucp); + if (packet_length < 1 + 4 || packet_length > 256 * 1024) { + buffer_dump(&incoming_packet); + packet_disconnect("Bad packet length %d.", packet_length); + } + DBG(debug("input: packet len %d", 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 + buffer_append_space(&incoming_packet, &cp, need); + packet_decrypt(&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 = hmac( mac->md, seqnr, + (unsigned char *) buffer_ptr(&incoming_packet), + buffer_len(&incoming_packet), + mac->key, mac->key_len + ); + if (memcmp(macbuf, buffer_ptr(&input), mac->mac_len) != 0) + packet_disconnect("Corrupted HMAC on input."); + DBG(debug("HMAC #%d ok", seqnr)); + buffer_consume(&input, mac->mac_len); + } + if (++seqnr == 0) + log("incoming seqnr wraps around"); + + /* get padlen */ + cp = buffer_ptr(&incoming_packet) + 4; + padlen = *cp & 0xff; + 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) + */ + buffer_get(&incoming_packet, (char *)&buf[0], 1); + *payload_len_ptr = buffer_len(&incoming_packet); + + /* reset for next packet */ + packet_length = 0; + + /* extract packet type */ + type = (unsigned char)buf[0]; + + if (type == SSH2_MSG_NEWKEYS) { + if (kex==NULL || mac==NULL || enc==NULL || comp==NULL) + fatal("packet_read_poll2: no KEX"); + if (mac->md != NULL) + mac->enabled = 1; + debug("cipher_set_key_iv receive_context"); + cipher_set_key_iv(&receive_context, enc->type, + enc->key, enc->key_len, + enc->iv, enc->iv_len); + clear_enc_keys(enc, kex->we_need); + if (comp->type != 0 && comp->enabled == 0) { + comp->enabled = 1; + if (! packet_compression) + packet_start_compression(6); + } + } + +#ifdef PACKET_DEBUG + fprintf(stderr, "read/plain[%d]:\r\n",type); + buffer_dump(&incoming_packet); +#endif + return (unsigned char)type; +} + +int +packet_read_poll(int *payload_len_ptr) +{ + char *msg; + for (;;) { + int type = use_ssh2_packet_format ? + packet_read_poll2(payload_len_ptr): + packet_read_poll1(payload_len_ptr); + + if(compat20) { + int reason; + if (type != 0) + 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); + log("Received disconnect: %d: %.900s", reason, msg); + xfree(msg); + fatal_cleanup(); + break; + default: + return type; + break; + } + } else { + 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); + log("Received disconnect: %.900s", msg); + fatal_cleanup(); + xfree(msg); + break; + default: + if (type != 0) + DBG(debug("received packet type %d", type)); + return type; + break; + } + } + } +} + /* * Buffers the given amount of input characters. This is intended to be used * together with packet_read_poll. @@ -733,8 +1119,15 @@ packet_disconnect(const char *fmt,...) va_end(args); /* Send the disconnect message to the other side, and wait for it to get sent. */ - packet_start(SSH_MSG_DISCONNECT); - packet_put_string(buf, strlen(buf)); + 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_string(buf, strlen(buf)); + } packet_send(); packet_write_wait(); @@ -865,7 +1258,8 @@ packet_set_maxsize(int s) { static int called = 0; if (called) { - log("packet_set_maxsize: called twice: old %d new %d", max_packet_size, s); + log("packet_set_maxsize: called twice: old %d new %d", + max_packet_size, s); return -1; } if (s < 4 * 1024 || s > 1024 * 1024) { diff --git a/usr.bin/ssh/packet.h b/usr.bin/ssh/packet.h index 45390916f8f..6d936a7442c 100644 --- a/usr.bin/ssh/packet.h +++ b/usr.bin/ssh/packet.h @@ -13,7 +13,7 @@ * */ -/* RCSID("$Id: packet.h,v 1.11 2000/04/03 07:07:15 markus Exp $"); */ +/* RCSID("$Id: packet.h,v 1.12 2000/04/03 20:12:55 markus Exp $"); */ #ifndef PACKET_H #define PACKET_H @@ -132,7 +132,7 @@ unsigned int packet_get_int(void); * must have been initialized before this call. */ void packet_get_bignum(BIGNUM * value, int *length_ptr); -void packet_get_bignum2(BIGNUM * value, int *length_ptr); +void packet_get_bignum2(BIGNUM * value, int *length_ptr); char *packet_get_raw(int *length_ptr); /* @@ -200,4 +200,7 @@ do { \ int packet_connection_is_on_socket(void); int packet_connection_is_ipv4(void); +/* enable SSH2 packet format */ +void packet_set_ssh2_format(void); + #endif /* PACKET_H */ -- 2.20.1