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kex.c
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kex.c
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/* Copyright (c) 2004-2007, Sara Golemon <[email protected]>
* Copyright (c) 2010-2019, Daniel Stenberg <[email protected]>
* All rights reserved.
*
* Redistribution and use in source and binary forms,
* with or without modification, are permitted provided
* that the following conditions are met:
*
* Redistributions of source code must retain the above
* copyright notice, this list of conditions and the
* following disclaimer.
*
* 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.
*
* Neither the name of the copyright holder nor the names
* of any other contributors may be used to endorse or
* promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
* CONTRIBUTORS "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 COPYRIGHT OWNER OR
* CONTRIBUTORS 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 "libssh2_priv.h"
#include "transport.h"
#include "comp.h"
#include "mac.h"
/* TODO: Switch this to an inline and handle alloc() failures */
/* Helper macro called from
kex_method_diffie_hellman_group1_sha1_key_exchange */
#define LIBSSH2_KEX_METHOD_DIFFIE_HELLMAN_SHA1_HASH(value, reqlen, version) \
{ \
libssh2_sha1_ctx hash; \
unsigned long len = 0; \
if(!(value)) { \
value = LIBSSH2_ALLOC(session, reqlen + SHA_DIGEST_LENGTH); \
} \
if(value) \
while(len < (unsigned long)reqlen) { \
libssh2_sha1_init(&hash); \
libssh2_sha1_update(hash, exchange_state->k_value, \
exchange_state->k_value_len); \
libssh2_sha1_update(hash, exchange_state->h_sig_comp, \
SHA_DIGEST_LENGTH); \
if(len > 0) { \
libssh2_sha1_update(hash, value, len); \
} \
else { \
libssh2_sha1_update(hash, (version), 1); \
libssh2_sha1_update(hash, session->session_id, \
session->session_id_len); \
} \
libssh2_sha1_final(hash, (value) + len); \
len += SHA_DIGEST_LENGTH; \
} \
} \
#define LIBSSH2_KEX_METHOD_EC_SHA_VALUE_HASH(value, reqlen, version) \
{ \
if(type == LIBSSH2_EC_CURVE_NISTP256) { \
LIBSSH2_KEX_METHOD_SHA_VALUE_HASH(256, value, reqlen, version); \
} \
else if(type == LIBSSH2_EC_CURVE_NISTP384) { \
LIBSSH2_KEX_METHOD_SHA_VALUE_HASH(384, value, reqlen, version); \
} \
else if(type == LIBSSH2_EC_CURVE_NISTP521) { \
LIBSSH2_KEX_METHOD_SHA_VALUE_HASH(512, value, reqlen, version); \
} \
} \
#define LIBSSH2_KEX_METHOD_SHA_VALUE_HASH(digest_type, value, \
reqlen, version) \
{ \
libssh2_sha##digest_type##_ctx hash; \
unsigned long len = 0; \
if(!(value)) { \
value = LIBSSH2_ALLOC(session, \
reqlen + SHA##digest_type##_DIGEST_LENGTH); \
} \
if(value) \
while(len < (unsigned long)reqlen) { \
libssh2_sha##digest_type##_init(&hash); \
libssh2_sha##digest_type##_update(hash, \
exchange_state->k_value, \
exchange_state->k_value_len); \
libssh2_sha##digest_type##_update(hash, \
exchange_state->h_sig_comp, \
SHA##digest_type##_DIGEST_LENGTH); \
if(len > 0) { \
libssh2_sha##digest_type##_update(hash, value, len); \
} \
else { \
libssh2_sha##digest_type##_update(hash, (version), 1); \
libssh2_sha##digest_type##_update(hash, session->session_id, \
session->session_id_len); \
} \
libssh2_sha##digest_type##_final(hash, (value) + len); \
len += SHA##digest_type##_DIGEST_LENGTH; \
} \
}
/*
* diffie_hellman_sha1
*
* Diffie Hellman Key Exchange, Group Agnostic
*/
static int diffie_hellman_sha1(LIBSSH2_SESSION *session,
_libssh2_bn *g,
_libssh2_bn *p,
int group_order,
unsigned char packet_type_init,
unsigned char packet_type_reply,
unsigned char *midhash,
unsigned long midhash_len,
kmdhgGPshakex_state_t *exchange_state)
{
int ret = 0;
int rc;
libssh2_sha1_ctx exchange_hash_ctx;
if(exchange_state->state == libssh2_NB_state_idle) {
/* Setup initial values */
exchange_state->e_packet = NULL;
exchange_state->s_packet = NULL;
exchange_state->k_value = NULL;
exchange_state->ctx = _libssh2_bn_ctx_new();
libssh2_dh_init(&exchange_state->x);
exchange_state->e = _libssh2_bn_init(); /* g^x mod p */
exchange_state->f = _libssh2_bn_init_from_bin(); /* g^(Random from
server) mod p */
exchange_state->k = _libssh2_bn_init(); /* The shared secret: f^x mod
p */
/* Zero the whole thing out */
memset(&exchange_state->req_state, 0, sizeof(packet_require_state_t));
/* Generate x and e */
rc = libssh2_dh_key_pair(&exchange_state->x, exchange_state->e, g, p,
group_order, exchange_state->ctx);
if(rc)
goto clean_exit;
/* Send KEX init */
/* packet_type(1) + String Length(4) + leading 0(1) */
exchange_state->e_packet_len =
_libssh2_bn_bytes(exchange_state->e) + 6;
if(_libssh2_bn_bits(exchange_state->e) % 8) {
/* Leading 00 not needed */
exchange_state->e_packet_len--;
}
exchange_state->e_packet =
LIBSSH2_ALLOC(session, exchange_state->e_packet_len);
if(!exchange_state->e_packet) {
ret = _libssh2_error(session, LIBSSH2_ERROR_ALLOC,
"Out of memory error");
goto clean_exit;
}
exchange_state->e_packet[0] = packet_type_init;
_libssh2_htonu32(exchange_state->e_packet + 1,
exchange_state->e_packet_len - 5);
if(_libssh2_bn_bits(exchange_state->e) % 8) {
_libssh2_bn_to_bin(exchange_state->e,
exchange_state->e_packet + 5);
}
else {
exchange_state->e_packet[5] = 0;
_libssh2_bn_to_bin(exchange_state->e,
exchange_state->e_packet + 6);
}
_libssh2_debug(session, LIBSSH2_TRACE_KEX, "Sending KEX packet %d",
(int) packet_type_init);
exchange_state->state = libssh2_NB_state_created;
}
if(exchange_state->state == libssh2_NB_state_created) {
rc = _libssh2_transport_send(session, exchange_state->e_packet,
exchange_state->e_packet_len,
NULL, 0);
if(rc == LIBSSH2_ERROR_EAGAIN) {
return rc;
}
else if(rc) {
ret = _libssh2_error(session, rc,
"Unable to send KEX init message");
goto clean_exit;
}
exchange_state->state = libssh2_NB_state_sent;
}
if(exchange_state->state == libssh2_NB_state_sent) {
if(session->burn_optimistic_kexinit) {
/* The first KEX packet to come along will be the guess initially
* sent by the server. That guess turned out to be wrong so we
* need to silently ignore it */
int burn_type;
_libssh2_debug(session, LIBSSH2_TRACE_KEX,
"Waiting for badly guessed KEX packet "
"(to be ignored)");
burn_type =
_libssh2_packet_burn(session, &exchange_state->burn_state);
if(burn_type == LIBSSH2_ERROR_EAGAIN) {
return burn_type;
}
else if(burn_type <= 0) {
/* Failed to receive a packet */
ret = burn_type;
goto clean_exit;
}
session->burn_optimistic_kexinit = 0;
_libssh2_debug(session, LIBSSH2_TRACE_KEX,
"Burnt packet of type: %02x",
(unsigned int) burn_type);
}
exchange_state->state = libssh2_NB_state_sent1;
}
if(exchange_state->state == libssh2_NB_state_sent1) {
/* Wait for KEX reply */
struct string_buf buf;
size_t host_key_len;
rc = _libssh2_packet_require(session, packet_type_reply,
&exchange_state->s_packet,
&exchange_state->s_packet_len, 0, NULL,
0, &exchange_state->req_state);
if(rc == LIBSSH2_ERROR_EAGAIN) {
return rc;
}
if(rc) {
ret = _libssh2_error(session, LIBSSH2_ERROR_TIMEOUT,
"Timed out waiting for KEX reply");
goto clean_exit;
}
/* Parse KEXDH_REPLY */
if(exchange_state->s_packet_len < 5) {
ret = _libssh2_error(session, LIBSSH2_ERROR_PROTO,
"Unexpected packet length");
goto clean_exit;
}
buf.data = exchange_state->s_packet;
buf.len = exchange_state->s_packet_len;
buf.dataptr = buf.data;
buf.dataptr++; /* advance past type */
if(session->server_hostkey)
LIBSSH2_FREE(session, session->server_hostkey);
if(_libssh2_copy_string(session, &buf, &(session->server_hostkey),
&host_key_len)) {
ret = _libssh2_error(session, LIBSSH2_ERROR_ALLOC,
"Could not copy host key");
goto clean_exit;
}
session->server_hostkey_len = (uint32_t)host_key_len;
#if LIBSSH2_MD5
{
libssh2_md5_ctx fingerprint_ctx;
if(libssh2_md5_init(&fingerprint_ctx)) {
libssh2_md5_update(fingerprint_ctx, session->server_hostkey,
session->server_hostkey_len);
libssh2_md5_final(fingerprint_ctx,
session->server_hostkey_md5);
session->server_hostkey_md5_valid = TRUE;
}
else {
session->server_hostkey_md5_valid = FALSE;
}
}
#ifdef LIBSSH2DEBUG
{
char fingerprint[50], *fprint = fingerprint;
int i;
for(i = 0; i < 16; i++, fprint += 3) {
snprintf(fprint, 4, "%02x:", session->server_hostkey_md5[i]);
}
*(--fprint) = '\0';
_libssh2_debug(session, LIBSSH2_TRACE_KEX,
"Server's MD5 Fingerprint: %s", fingerprint);
}
#endif /* LIBSSH2DEBUG */
#endif /* ! LIBSSH2_MD5 */
{
libssh2_sha1_ctx fingerprint_ctx;
if(libssh2_sha1_init(&fingerprint_ctx)) {
libssh2_sha1_update(fingerprint_ctx, session->server_hostkey,
session->server_hostkey_len);
libssh2_sha1_final(fingerprint_ctx,
session->server_hostkey_sha1);
session->server_hostkey_sha1_valid = TRUE;
}
else {
session->server_hostkey_sha1_valid = FALSE;
}
}
#ifdef LIBSSH2DEBUG
{
char fingerprint[64], *fprint = fingerprint;
int i;
for(i = 0; i < 20; i++, fprint += 3) {
snprintf(fprint, 4, "%02x:", session->server_hostkey_sha1[i]);
}
*(--fprint) = '\0';
_libssh2_debug(session, LIBSSH2_TRACE_KEX,
"Server's SHA1 Fingerprint: %s", fingerprint);
}
#endif /* LIBSSH2DEBUG */
{
libssh2_sha256_ctx fingerprint_ctx;
if(libssh2_sha256_init(&fingerprint_ctx)) {
libssh2_sha256_update(fingerprint_ctx, session->server_hostkey,
session->server_hostkey_len);
libssh2_sha256_final(fingerprint_ctx,
session->server_hostkey_sha256);
session->server_hostkey_sha256_valid = TRUE;
}
else {
session->server_hostkey_sha256_valid = FALSE;
}
}
#ifdef LIBSSH2DEBUG
{
char *base64Fingerprint = NULL;
_libssh2_base64_encode(session,
(const char *)
session->server_hostkey_sha256,
SHA256_DIGEST_LENGTH, &base64Fingerprint);
if(base64Fingerprint != NULL) {
_libssh2_debug(session, LIBSSH2_TRACE_KEX,
"Server's SHA256 Fingerprint: %s",
base64Fingerprint);
LIBSSH2_FREE(session, base64Fingerprint);
}
}
#endif /* LIBSSH2DEBUG */
if(session->hostkey->init(session, session->server_hostkey,
session->server_hostkey_len,
&session->server_hostkey_abstract)) {
ret = _libssh2_error(session, LIBSSH2_ERROR_HOSTKEY_INIT,
"Unable to initialize hostkey importer");
goto clean_exit;
}
if(_libssh2_get_string(&buf, &(exchange_state->f_value),
&(exchange_state->f_value_len))) {
ret = _libssh2_error(session, LIBSSH2_ERROR_HOSTKEY_INIT,
"Unable to get f value");
goto clean_exit;
}
_libssh2_bn_from_bin(exchange_state->f, exchange_state->f_value_len,
exchange_state->f_value);
if(_libssh2_get_string(&buf, &(exchange_state->h_sig),
&(exchange_state->h_sig_len))) {
ret = _libssh2_error(session, LIBSSH2_ERROR_HOSTKEY_INIT,
"Unable to get h sig");
goto clean_exit;
}
/* Compute the shared secret */
libssh2_dh_secret(&exchange_state->x, exchange_state->k,
exchange_state->f, p, exchange_state->ctx);
exchange_state->k_value_len = _libssh2_bn_bytes(exchange_state->k) + 5;
if(_libssh2_bn_bits(exchange_state->k) % 8) {
/* don't need leading 00 */
exchange_state->k_value_len--;
}
exchange_state->k_value =
LIBSSH2_ALLOC(session, exchange_state->k_value_len);
if(!exchange_state->k_value) {
ret = _libssh2_error(session, LIBSSH2_ERROR_ALLOC,
"Unable to allocate buffer for K");
goto clean_exit;
}
_libssh2_htonu32(exchange_state->k_value,
exchange_state->k_value_len - 4);
if(_libssh2_bn_bits(exchange_state->k) % 8) {
_libssh2_bn_to_bin(exchange_state->k, exchange_state->k_value + 4);
}
else {
exchange_state->k_value[4] = 0;
_libssh2_bn_to_bin(exchange_state->k, exchange_state->k_value + 5);
}
exchange_state->exchange_hash = (void *)&exchange_hash_ctx;
libssh2_sha1_init(&exchange_hash_ctx);
if(session->local.banner) {
_libssh2_htonu32(exchange_state->h_sig_comp,
strlen((char *) session->local.banner) - 2);
libssh2_sha1_update(exchange_hash_ctx,
exchange_state->h_sig_comp, 4);
libssh2_sha1_update(exchange_hash_ctx,
session->local.banner,
strlen((char *) session->local.banner) - 2);
}
else {
_libssh2_htonu32(exchange_state->h_sig_comp,
sizeof(LIBSSH2_SSH_DEFAULT_BANNER) - 1);
libssh2_sha1_update(exchange_hash_ctx,
exchange_state->h_sig_comp, 4);
libssh2_sha1_update(exchange_hash_ctx,
(const unsigned char *)
LIBSSH2_SSH_DEFAULT_BANNER,
sizeof(LIBSSH2_SSH_DEFAULT_BANNER) - 1);
}
_libssh2_htonu32(exchange_state->h_sig_comp,
strlen((char *) session->remote.banner));
libssh2_sha1_update(exchange_hash_ctx,
exchange_state->h_sig_comp, 4);
libssh2_sha1_update(exchange_hash_ctx,
session->remote.banner,
strlen((char *) session->remote.banner));
_libssh2_htonu32(exchange_state->h_sig_comp,
session->local.kexinit_len);
libssh2_sha1_update(exchange_hash_ctx,
exchange_state->h_sig_comp, 4);
libssh2_sha1_update(exchange_hash_ctx,
session->local.kexinit,
session->local.kexinit_len);
_libssh2_htonu32(exchange_state->h_sig_comp,
session->remote.kexinit_len);
libssh2_sha1_update(exchange_hash_ctx,
exchange_state->h_sig_comp, 4);
libssh2_sha1_update(exchange_hash_ctx,
session->remote.kexinit,
session->remote.kexinit_len);
_libssh2_htonu32(exchange_state->h_sig_comp,
session->server_hostkey_len);
libssh2_sha1_update(exchange_hash_ctx,
exchange_state->h_sig_comp, 4);
libssh2_sha1_update(exchange_hash_ctx,
session->server_hostkey,
session->server_hostkey_len);
if(packet_type_init == SSH_MSG_KEX_DH_GEX_INIT) {
/* diffie-hellman-group-exchange hashes additional fields */
#ifdef LIBSSH2_DH_GEX_NEW
_libssh2_htonu32(exchange_state->h_sig_comp,
LIBSSH2_DH_GEX_MINGROUP);
_libssh2_htonu32(exchange_state->h_sig_comp + 4,
LIBSSH2_DH_GEX_OPTGROUP);
_libssh2_htonu32(exchange_state->h_sig_comp + 8,
LIBSSH2_DH_GEX_MAXGROUP);
libssh2_sha1_update(exchange_hash_ctx,
exchange_state->h_sig_comp, 12);
#else
_libssh2_htonu32(exchange_state->h_sig_comp,
LIBSSH2_DH_GEX_OPTGROUP);
libssh2_sha1_update(exchange_hash_ctx,
exchange_state->h_sig_comp, 4);
#endif
}
if(midhash) {
libssh2_sha1_update(exchange_hash_ctx, midhash,
midhash_len);
}
libssh2_sha1_update(exchange_hash_ctx,
exchange_state->e_packet + 1,
exchange_state->e_packet_len - 1);
_libssh2_htonu32(exchange_state->h_sig_comp,
exchange_state->f_value_len);
libssh2_sha1_update(exchange_hash_ctx,
exchange_state->h_sig_comp, 4);
libssh2_sha1_update(exchange_hash_ctx,
exchange_state->f_value,
exchange_state->f_value_len);
libssh2_sha1_update(exchange_hash_ctx,
exchange_state->k_value,
exchange_state->k_value_len);
libssh2_sha1_final(exchange_hash_ctx,
exchange_state->h_sig_comp);
if(session->hostkey->
sig_verify(session, exchange_state->h_sig,
exchange_state->h_sig_len, exchange_state->h_sig_comp,
20, &session->server_hostkey_abstract)) {
ret = _libssh2_error(session, LIBSSH2_ERROR_HOSTKEY_SIGN,
"Unable to verify hostkey signature");
goto clean_exit;
}
_libssh2_debug(session, LIBSSH2_TRACE_KEX, "Sending NEWKEYS message");
exchange_state->c = SSH_MSG_NEWKEYS;
exchange_state->state = libssh2_NB_state_sent2;
}
if(exchange_state->state == libssh2_NB_state_sent2) {
rc = _libssh2_transport_send(session, &exchange_state->c, 1, NULL, 0);
if(rc == LIBSSH2_ERROR_EAGAIN) {
return rc;
}
else if(rc) {
ret = _libssh2_error(session, rc,
"Unable to send NEWKEYS message");
goto clean_exit;
}
exchange_state->state = libssh2_NB_state_sent3;
}
if(exchange_state->state == libssh2_NB_state_sent3) {
rc = _libssh2_packet_require(session, SSH_MSG_NEWKEYS,
&exchange_state->tmp,
&exchange_state->tmp_len, 0, NULL, 0,
&exchange_state->req_state);
if(rc == LIBSSH2_ERROR_EAGAIN) {
return rc;
}
else if(rc) {
ret = _libssh2_error(session, rc, "Timed out waiting for NEWKEYS");
goto clean_exit;
}
/* The first key exchange has been performed,
switch to active crypt/comp/mac mode */
session->state |= LIBSSH2_STATE_NEWKEYS;
_libssh2_debug(session, LIBSSH2_TRACE_KEX, "Received NEWKEYS message");
/* This will actually end up being just packet_type(1)
for this packet type anyway */
LIBSSH2_FREE(session, exchange_state->tmp);
if(!session->session_id) {
session->session_id = LIBSSH2_ALLOC(session, SHA_DIGEST_LENGTH);
if(!session->session_id) {
ret = _libssh2_error(session, LIBSSH2_ERROR_ALLOC,
"Unable to allocate buffer for "
"SHA digest");
goto clean_exit;
}
memcpy(session->session_id, exchange_state->h_sig_comp,
SHA_DIGEST_LENGTH);
session->session_id_len = SHA_DIGEST_LENGTH;
_libssh2_debug(session, LIBSSH2_TRACE_KEX,
"session_id calculated");
}
/* Cleanup any existing cipher */
if(session->local.crypt->dtor) {
session->local.crypt->dtor(session,
&session->local.crypt_abstract);
}
/* Calculate IV/Secret/Key for each direction */
if(session->local.crypt->init) {
unsigned char *iv = NULL, *secret = NULL;
int free_iv = 0, free_secret = 0;
LIBSSH2_KEX_METHOD_DIFFIE_HELLMAN_SHA1_HASH(iv,
session->local.crypt->
iv_len,
(const unsigned char *)
"A");
if(!iv) {
ret = -1;
goto clean_exit;
}
LIBSSH2_KEX_METHOD_DIFFIE_HELLMAN_SHA1_HASH(secret,
session->local.crypt->
secret_len,
(const unsigned char *)
"C");
if(!secret) {
LIBSSH2_FREE(session, iv);
ret = LIBSSH2_ERROR_KEX_FAILURE;
goto clean_exit;
}
if(session->local.crypt->
init(session, session->local.crypt, iv, &free_iv, secret,
&free_secret, 1, &session->local.crypt_abstract)) {
LIBSSH2_FREE(session, iv);
LIBSSH2_FREE(session, secret);
ret = LIBSSH2_ERROR_KEX_FAILURE;
goto clean_exit;
}
if(free_iv) {
_libssh2_explicit_zero(iv, session->local.crypt->iv_len);
LIBSSH2_FREE(session, iv);
}
if(free_secret) {
_libssh2_explicit_zero(secret,
session->local.crypt->secret_len);
LIBSSH2_FREE(session, secret);
}
}
_libssh2_debug(session, LIBSSH2_TRACE_KEX,
"Client to Server IV and Key calculated");
if(session->remote.crypt->dtor) {
/* Cleanup any existing cipher */
session->remote.crypt->dtor(session,
&session->remote.crypt_abstract);
}
if(session->remote.crypt->init) {
unsigned char *iv = NULL, *secret = NULL;
int free_iv = 0, free_secret = 0;
LIBSSH2_KEX_METHOD_DIFFIE_HELLMAN_SHA1_HASH(iv,
session->remote.crypt->
iv_len,
(const unsigned char *)
"B");
if(!iv) {
ret = LIBSSH2_ERROR_KEX_FAILURE;
goto clean_exit;
}
LIBSSH2_KEX_METHOD_DIFFIE_HELLMAN_SHA1_HASH(secret,
session->remote.crypt->
secret_len,
(const unsigned char *)
"D");
if(!secret) {
LIBSSH2_FREE(session, iv);
ret = LIBSSH2_ERROR_KEX_FAILURE;
goto clean_exit;
}
if(session->remote.crypt->
init(session, session->remote.crypt, iv, &free_iv, secret,
&free_secret, 0, &session->remote.crypt_abstract)) {
LIBSSH2_FREE(session, iv);
LIBSSH2_FREE(session, secret);
ret = LIBSSH2_ERROR_KEX_FAILURE;
goto clean_exit;
}
if(free_iv) {
_libssh2_explicit_zero(iv, session->remote.crypt->iv_len);
LIBSSH2_FREE(session, iv);
}
if(free_secret) {
_libssh2_explicit_zero(secret,
session->remote.crypt->secret_len);
LIBSSH2_FREE(session, secret);
}
}
_libssh2_debug(session, LIBSSH2_TRACE_KEX,
"Server to Client IV and Key calculated");
if(session->local.mac->dtor) {
session->local.mac->dtor(session, &session->local.mac_abstract);
}
if(session->local.mac->init) {
unsigned char *key = NULL;
int free_key = 0;
LIBSSH2_KEX_METHOD_DIFFIE_HELLMAN_SHA1_HASH(key,
session->local.mac->
key_len,
(const unsigned char *)
"E");
if(!key) {
ret = LIBSSH2_ERROR_KEX_FAILURE;
goto clean_exit;
}
session->local.mac->init(session, key, &free_key,
&session->local.mac_abstract);
if(free_key) {
_libssh2_explicit_zero(key, session->local.mac->key_len);
LIBSSH2_FREE(session, key);
}
}
_libssh2_debug(session, LIBSSH2_TRACE_KEX,
"Client to Server HMAC Key calculated");
if(session->remote.mac->dtor) {
session->remote.mac->dtor(session, &session->remote.mac_abstract);
}
if(session->remote.mac->init) {
unsigned char *key = NULL;
int free_key = 0;
LIBSSH2_KEX_METHOD_DIFFIE_HELLMAN_SHA1_HASH(key,
session->remote.mac->
key_len,
(const unsigned char *)
"F");
if(!key) {
ret = LIBSSH2_ERROR_KEX_FAILURE;
goto clean_exit;
}
session->remote.mac->init(session, key, &free_key,
&session->remote.mac_abstract);
if(free_key) {
_libssh2_explicit_zero(key, session->remote.mac->key_len);
LIBSSH2_FREE(session, key);
}
}
_libssh2_debug(session, LIBSSH2_TRACE_KEX,
"Server to Client HMAC Key calculated");
/* Initialize compression for each direction */
/* Cleanup any existing compression */
if(session->local.comp && session->local.comp->dtor) {
session->local.comp->dtor(session, 1,
&session->local.comp_abstract);
}
if(session->local.comp && session->local.comp->init) {
if(session->local.comp->init(session, 1,
&session->local.comp_abstract)) {
ret = LIBSSH2_ERROR_KEX_FAILURE;
goto clean_exit;
}
}
_libssh2_debug(session, LIBSSH2_TRACE_KEX,
"Client to Server compression initialized");
if(session->remote.comp && session->remote.comp->dtor) {
session->remote.comp->dtor(session, 0,
&session->remote.comp_abstract);
}
if(session->remote.comp && session->remote.comp->init) {
if(session->remote.comp->init(session, 0,
&session->remote.comp_abstract)) {
ret = LIBSSH2_ERROR_KEX_FAILURE;
goto clean_exit;
}
}
_libssh2_debug(session, LIBSSH2_TRACE_KEX,
"Server to Client compression initialized");
}
clean_exit:
libssh2_dh_dtor(&exchange_state->x);
_libssh2_bn_free(exchange_state->e);
exchange_state->e = NULL;
_libssh2_bn_free(exchange_state->f);
exchange_state->f = NULL;
_libssh2_bn_free(exchange_state->k);
exchange_state->k = NULL;
_libssh2_bn_ctx_free(exchange_state->ctx);
exchange_state->ctx = NULL;
if(exchange_state->e_packet) {
LIBSSH2_FREE(session, exchange_state->e_packet);
exchange_state->e_packet = NULL;
}
if(exchange_state->s_packet) {
LIBSSH2_FREE(session, exchange_state->s_packet);
exchange_state->s_packet = NULL;
}
if(exchange_state->k_value) {
LIBSSH2_FREE(session, exchange_state->k_value);
exchange_state->k_value = NULL;
}
exchange_state->state = libssh2_NB_state_idle;
return ret;
}
/*
* diffie_hellman_sha256
*
* Diffie Hellman Key Exchange, Group Agnostic
*/
static int diffie_hellman_sha256(LIBSSH2_SESSION *session,
_libssh2_bn *g,
_libssh2_bn *p,
int group_order,
unsigned char packet_type_init,
unsigned char packet_type_reply,
unsigned char *midhash,
unsigned long midhash_len,
kmdhgGPshakex_state_t *exchange_state)
{
int ret = 0;
int rc;
libssh2_sha256_ctx exchange_hash_ctx;
if(exchange_state->state == libssh2_NB_state_idle) {
/* Setup initial values */
exchange_state->e_packet = NULL;
exchange_state->s_packet = NULL;
exchange_state->k_value = NULL;
exchange_state->ctx = _libssh2_bn_ctx_new();
libssh2_dh_init(&exchange_state->x);
exchange_state->e = _libssh2_bn_init(); /* g^x mod p */
exchange_state->f = _libssh2_bn_init_from_bin(); /* g^(Random from
server) mod p */
exchange_state->k = _libssh2_bn_init(); /* The shared secret: f^x mod
p */
/* Zero the whole thing out */
memset(&exchange_state->req_state, 0, sizeof(packet_require_state_t));
/* Generate x and e */
rc = libssh2_dh_key_pair(&exchange_state->x, exchange_state->e, g, p,
group_order, exchange_state->ctx);
if(rc)
goto clean_exit;
/* Send KEX init */
/* packet_type(1) + String Length(4) + leading 0(1) */
exchange_state->e_packet_len =
_libssh2_bn_bytes(exchange_state->e) + 6;
if(_libssh2_bn_bits(exchange_state->e) % 8) {
/* Leading 00 not needed */
exchange_state->e_packet_len--;
}
exchange_state->e_packet =
LIBSSH2_ALLOC(session, exchange_state->e_packet_len);
if(!exchange_state->e_packet) {
ret = _libssh2_error(session, LIBSSH2_ERROR_ALLOC,
"Out of memory error");
goto clean_exit;
}
exchange_state->e_packet[0] = packet_type_init;
_libssh2_htonu32(exchange_state->e_packet + 1,
exchange_state->e_packet_len - 5);
if(_libssh2_bn_bits(exchange_state->e) % 8) {
_libssh2_bn_to_bin(exchange_state->e,
exchange_state->e_packet + 5);
}
else {
exchange_state->e_packet[5] = 0;
_libssh2_bn_to_bin(exchange_state->e,
exchange_state->e_packet + 6);
}
_libssh2_debug(session, LIBSSH2_TRACE_KEX, "Sending KEX packet %d",
(int) packet_type_init);
exchange_state->state = libssh2_NB_state_created;
}
if(exchange_state->state == libssh2_NB_state_created) {
rc = _libssh2_transport_send(session, exchange_state->e_packet,
exchange_state->e_packet_len,
NULL, 0);
if(rc == LIBSSH2_ERROR_EAGAIN) {
return rc;
}
else if(rc) {
ret = _libssh2_error(session, rc,
"Unable to send KEX init message");
goto clean_exit;
}
exchange_state->state = libssh2_NB_state_sent;
}
if(exchange_state->state == libssh2_NB_state_sent) {
if(session->burn_optimistic_kexinit) {
/* The first KEX packet to come along will be the guess initially
* sent by the server. That guess turned out to be wrong so we
* need to silently ignore it */
int burn_type;
_libssh2_debug(session, LIBSSH2_TRACE_KEX,
"Waiting for badly guessed KEX packet "
"(to be ignored)");
burn_type =
_libssh2_packet_burn(session, &exchange_state->burn_state);
if(burn_type == LIBSSH2_ERROR_EAGAIN) {
return burn_type;
}
else if(burn_type <= 0) {
/* Failed to receive a packet */
ret = burn_type;
goto clean_exit;
}
session->burn_optimistic_kexinit = 0;
_libssh2_debug(session, LIBSSH2_TRACE_KEX,
"Burnt packet of type: %02x",
(unsigned int) burn_type);
}
exchange_state->state = libssh2_NB_state_sent1;
}
if(exchange_state->state == libssh2_NB_state_sent1) {
/* Wait for KEX reply */
struct string_buf buf;
size_t host_key_len;
rc = _libssh2_packet_require(session, packet_type_reply,
&exchange_state->s_packet,
&exchange_state->s_packet_len, 0, NULL,
0, &exchange_state->req_state);
if(rc == LIBSSH2_ERROR_EAGAIN) {
return rc;
}
if(rc) {
ret = _libssh2_error(session, LIBSSH2_ERROR_TIMEOUT,
"Timed out waiting for KEX reply");
goto clean_exit;
}
/* Parse KEXDH_REPLY */
if(exchange_state->s_packet_len < 5) {
ret = _libssh2_error(session, LIBSSH2_ERROR_PROTO,
"Unexpected packet length");
goto clean_exit;
}
buf.data = exchange_state->s_packet;
buf.len = exchange_state->s_packet_len;
buf.dataptr = buf.data;
buf.dataptr++; /* advance past type */
if(session->server_hostkey)
LIBSSH2_FREE(session, session->server_hostkey);
if(_libssh2_copy_string(session, &buf, &(session->server_hostkey),
&host_key_len)) {
ret = _libssh2_error(session, LIBSSH2_ERROR_ALLOC,
"Could not copy host key");
goto clean_exit;
}
session->server_hostkey_len = (uint32_t)host_key_len;
#if LIBSSH2_MD5
{
libssh2_md5_ctx fingerprint_ctx;
if(libssh2_md5_init(&fingerprint_ctx)) {
libssh2_md5_update(fingerprint_ctx, session->server_hostkey,
session->server_hostkey_len);
libssh2_md5_final(fingerprint_ctx,
session->server_hostkey_md5);
session->server_hostkey_md5_valid = TRUE;
}
else {
session->server_hostkey_md5_valid = FALSE;
}
}
#ifdef LIBSSH2DEBUG
{
char fingerprint[50], *fprint = fingerprint;
int i;
for(i = 0; i < 16; i++, fprint += 3) {
snprintf(fprint, 4, "%02x:", session->server_hostkey_md5[i]);
}
*(--fprint) = '\0';
_libssh2_debug(session, LIBSSH2_TRACE_KEX,
"Server's MD5 Fingerprint: %s", fingerprint);
}