*
* 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"
#include "deattack.h"
#include "channels.h"
+#include "compat.h"
+#include "ssh2.h"
+
+#include <ssl/bn.h>
+#include <ssl/dh.h>
+#include <ssl/hmac.h>
+#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
/* 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)
{
* Level is compression level 1 (fastest) - 9 (slow, best) as in gzip.
*/
+/*** XXXXX todo: kex means re-init */
void
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);
}
void
packet_decrypt(CipherContext * cc, void *dest, void *src,
- unsigned int bytes)
+ unsigned int bytes)
{
int i;
* (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");
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);
/* Starts constructing a packet to send. */
void
-packet_start(int type)
+packet_start1(int type)
{
char buf[9];
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
*/
void
-packet_send()
+packet_send1()
{
char buf[8], *cp;
int i, padding, len;
*/
}
+/*
+ * 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
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();
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
*/
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;
/* 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);
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);
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);
/* 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.
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();
{
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) {
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