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openssh/packet.c

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/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, 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"
#include "openbsd-compat/sys-queue.h"
#include <netinet/in_systm.h>
#include <netinet/ip.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;
/* Set to true if we are the server side. */
static int server_side = 0;
/* Set to true if we are authenticated. */
static int after_authentication = 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 == COMP_ZLIB ||
(comp->type == COMP_DELAYED && after_authentication)) &&
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);
}
/*
* Delayed compression for SSH2 is enabled after authentication:
* This happans on the server side after a SSH2_MSG_USERAUTH_SUCCESS is sent,
* and on the client side after a SSH2_MSG_USERAUTH_SUCCESS is received.
*/
static void
packet_enable_delayed_compress(void)
{
Comp *comp = NULL;
int mode;
/*
* Remember that we are past the authentication step, so rekeying
* with COMP_DELAYED will turn on compression immediately.
*/
after_authentication = 1;
for (mode = 0; mode < MODE_MAX; mode++) {
comp = &newkeys[mode]->comp;
if (comp && !comp->enabled && comp->type == COMP_DELAYED) {
packet_init_compression();
if (mode == MODE_OUT)
buffer_compress_init_send(6);
else
buffer_compress_init_recv();
comp->enabled = 1;
}
}
}
/*
* 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);
else if (type == SSH2_MSG_USERAUTH_SUCCESS && server_side)
packet_enable_delayed_compress();
}
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);
if (type < SSH_MSG_MIN || type > SSH_MSG_MAX)
packet_disconnect("Invalid ssh1 packet type: %d", type);
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;
u_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_MIN || type >= SSH2_MSG_LOCAL_MIN)
packet_disconnect("Invalid ssh2 packet type: %d", type);
if (type == SSH2_MSG_NEWKEYS)
set_newkeys(MODE_IN);
else if (type == SSH2_MSG_USERAUTH_SUCCESS && !server_side)
packet_enable_delayed_compress();
#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;
}
} 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;
}
}
}
}
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(u_int *length_ptr)
{
u_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;
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;
}
void
packet_set_server(void)
{
server_side = 1;
}
void
packet_set_authenticated(void)
{
after_authentication = 1;
}
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