546 lines
14 KiB
C
546 lines
14 KiB
C
/* $NetBSD: kex.c,v 1.3 2001/01/14 05:22:32 itojun Exp $ */
|
|
|
|
/*
|
|
* Copyright (c) 2000 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.
|
|
*/
|
|
|
|
/* from OpenBSD: kex.c,v 1.16 2000/12/20 19:37:22 markus Exp */
|
|
|
|
#include <sys/cdefs.h>
|
|
#ifndef lint
|
|
__RCSID("$NetBSD: kex.c,v 1.3 2001/01/14 05:22:32 itojun Exp $");
|
|
#endif
|
|
|
|
#include "includes.h"
|
|
|
|
#include "ssh.h"
|
|
#include "ssh2.h"
|
|
#include "xmalloc.h"
|
|
#include "buffer.h"
|
|
#include "bufaux.h"
|
|
#include "packet.h"
|
|
#include "compat.h"
|
|
|
|
#include <openssl/bn.h>
|
|
#include <openssl/dh.h>
|
|
|
|
#include <openssl/crypto.h>
|
|
#include <openssl/bio.h>
|
|
#include <openssl/bn.h>
|
|
#include <openssl/dh.h>
|
|
#include <openssl/pem.h>
|
|
#include <openssl/rand.h>
|
|
|
|
#include "kex.h"
|
|
#include "key.h"
|
|
|
|
#define KEX_COOKIE_LEN 16
|
|
|
|
Buffer *
|
|
kex_init(char *myproposal[PROPOSAL_MAX])
|
|
{
|
|
int first_kex_packet_follows = 0;
|
|
u_char cookie[KEX_COOKIE_LEN];
|
|
u_int32_t rand = 0;
|
|
int i;
|
|
Buffer *ki = xmalloc(sizeof(*ki));
|
|
for (i = 0; i < KEX_COOKIE_LEN; i++) {
|
|
if (i % 4 == 0) {
|
|
/* XXXthorpej */
|
|
RAND_pseudo_bytes((u_char *)&rand, sizeof(rand));
|
|
}
|
|
cookie[i] = rand & 0xff;
|
|
rand >>= 8;
|
|
}
|
|
buffer_init(ki);
|
|
buffer_append(ki, (char *)cookie, sizeof cookie);
|
|
for (i = 0; i < PROPOSAL_MAX; i++)
|
|
buffer_put_cstring(ki, myproposal[i]);
|
|
buffer_put_char(ki, first_kex_packet_follows);
|
|
buffer_put_int(ki, 0); /* uint32 reserved */
|
|
return ki;
|
|
}
|
|
|
|
/* send kexinit, parse and save reply */
|
|
void
|
|
kex_exchange_kexinit(
|
|
Buffer *my_kexinit, Buffer *peer_kexint,
|
|
char *peer_proposal[PROPOSAL_MAX])
|
|
{
|
|
int i;
|
|
char *ptr;
|
|
int plen;
|
|
|
|
debug("send KEXINIT");
|
|
packet_start(SSH2_MSG_KEXINIT);
|
|
packet_put_raw(buffer_ptr(my_kexinit), buffer_len(my_kexinit));
|
|
packet_send();
|
|
packet_write_wait();
|
|
debug("done");
|
|
|
|
/*
|
|
* read and save raw KEXINIT payload in buffer. this is used during
|
|
* computation of the session_id and the session keys.
|
|
*/
|
|
debug("wait KEXINIT");
|
|
packet_read_expect(&plen, SSH2_MSG_KEXINIT);
|
|
ptr = packet_get_raw(&plen);
|
|
buffer_append(peer_kexint, ptr, plen);
|
|
|
|
/* parse packet and save algorithm proposal */
|
|
/* skip cookie */
|
|
for (i = 0; i < KEX_COOKIE_LEN; i++)
|
|
packet_get_char();
|
|
/* extract kex init proposal strings */
|
|
for (i = 0; i < PROPOSAL_MAX; i++) {
|
|
peer_proposal[i] = packet_get_string(NULL);
|
|
debug("got kexinit: %s", peer_proposal[i]);
|
|
}
|
|
/* first kex follow / reserved */
|
|
i = packet_get_char();
|
|
debug("first kex follow: %d ", i);
|
|
i = packet_get_int();
|
|
debug("reserved: %d ", i);
|
|
packet_done();
|
|
debug("done");
|
|
}
|
|
|
|
/* diffie-hellman-group1-sha1 */
|
|
|
|
int
|
|
dh_pub_is_valid(DH *dh, BIGNUM *dh_pub)
|
|
{
|
|
int i;
|
|
int n = BN_num_bits(dh_pub);
|
|
int bits_set = 0;
|
|
|
|
if (dh_pub->neg) {
|
|
log("invalid public DH value: negativ");
|
|
return 0;
|
|
}
|
|
for (i = 0; i <= n; i++)
|
|
if (BN_is_bit_set(dh_pub, i))
|
|
bits_set++;
|
|
debug("bits set: %d/%d", bits_set, BN_num_bits(dh->p));
|
|
|
|
/* if g==2 and bits_set==1 then computing log_g(dh_pub) is trivial */
|
|
if (bits_set > 1 && (BN_cmp(dh_pub, dh->p) == -1))
|
|
return 1;
|
|
log("invalid public DH value (%d/%d)", bits_set, BN_num_bits(dh->p));
|
|
return 0;
|
|
}
|
|
|
|
void
|
|
dh_gen_key(DH *dh)
|
|
{
|
|
int tries = 0;
|
|
|
|
do {
|
|
if (DH_generate_key(dh) == 0)
|
|
fatal("failed to generate DH key: rnd(4) is mandatory.");
|
|
if (tries++ > 10)
|
|
fatal("dh_new_group1: too many bad keys: giving up");
|
|
} while (!dh_pub_is_valid(dh, dh->pub_key));
|
|
}
|
|
|
|
DH *
|
|
dh_new_group_asc(const char *gen, const char *modulus)
|
|
{
|
|
DH *dh;
|
|
int ret;
|
|
|
|
dh = DH_new();
|
|
if (dh == NULL)
|
|
fatal("DH_new");
|
|
|
|
if ((ret = BN_hex2bn(&dh->p, modulus)) < 0)
|
|
fatal("BN_hex2bn p");
|
|
if ((ret = BN_hex2bn(&dh->g, gen)) < 0)
|
|
fatal("BN_hex2bn g");
|
|
|
|
return (dh);
|
|
}
|
|
|
|
/*
|
|
* This just returns the group, we still need to generate the exchange
|
|
* value.
|
|
*/
|
|
|
|
DH *
|
|
dh_new_group(BIGNUM *gen, BIGNUM *modulus)
|
|
{
|
|
DH *dh;
|
|
|
|
dh = DH_new();
|
|
if (dh == NULL)
|
|
fatal("DH_new");
|
|
dh->p = modulus;
|
|
dh->g = gen;
|
|
|
|
return (dh);
|
|
}
|
|
|
|
DH *
|
|
dh_new_group1(void)
|
|
{
|
|
static char *gen = "2", *group1 =
|
|
"FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
|
|
"29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
|
|
"EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
|
|
"E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
|
|
"EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE65381"
|
|
"FFFFFFFF" "FFFFFFFF";
|
|
|
|
return (dh_new_group_asc(gen, group1));
|
|
}
|
|
|
|
#ifdef DEBUG_KEX
|
|
void
|
|
dump_digest(u_char *digest, int len)
|
|
{
|
|
int i;
|
|
for (i = 0; i< len; i++){
|
|
fprintf(stderr, "%02x", digest[i]);
|
|
if(i%2!=0)
|
|
fprintf(stderr, " ");
|
|
}
|
|
fprintf(stderr, "\n");
|
|
}
|
|
#endif
|
|
|
|
u_char *
|
|
kex_hash(
|
|
char *client_version_string,
|
|
char *server_version_string,
|
|
char *ckexinit, int ckexinitlen,
|
|
char *skexinit, int skexinitlen,
|
|
char *serverhostkeyblob, int sbloblen,
|
|
BIGNUM *client_dh_pub,
|
|
BIGNUM *server_dh_pub,
|
|
BIGNUM *shared_secret)
|
|
{
|
|
Buffer b;
|
|
static u_char digest[EVP_MAX_MD_SIZE];
|
|
EVP_MD *evp_md = EVP_sha1();
|
|
EVP_MD_CTX md;
|
|
|
|
buffer_init(&b);
|
|
buffer_put_string(&b, client_version_string, strlen(client_version_string));
|
|
buffer_put_string(&b, server_version_string, strlen(server_version_string));
|
|
|
|
/* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
|
|
buffer_put_int(&b, ckexinitlen+1);
|
|
buffer_put_char(&b, SSH2_MSG_KEXINIT);
|
|
buffer_append(&b, ckexinit, ckexinitlen);
|
|
buffer_put_int(&b, skexinitlen+1);
|
|
buffer_put_char(&b, SSH2_MSG_KEXINIT);
|
|
buffer_append(&b, skexinit, skexinitlen);
|
|
|
|
buffer_put_string(&b, serverhostkeyblob, sbloblen);
|
|
buffer_put_bignum2(&b, client_dh_pub);
|
|
buffer_put_bignum2(&b, server_dh_pub);
|
|
buffer_put_bignum2(&b, shared_secret);
|
|
|
|
#ifdef DEBUG_KEX
|
|
buffer_dump(&b);
|
|
#endif
|
|
|
|
EVP_DigestInit(&md, evp_md);
|
|
EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
|
|
EVP_DigestFinal(&md, digest, NULL);
|
|
|
|
buffer_free(&b);
|
|
|
|
#ifdef DEBUG_KEX
|
|
dump_digest(digest, evp_md->md_size);
|
|
#endif
|
|
return digest;
|
|
}
|
|
|
|
u_char *
|
|
kex_hash_gex(
|
|
char *client_version_string,
|
|
char *server_version_string,
|
|
char *ckexinit, int ckexinitlen,
|
|
char *skexinit, int skexinitlen,
|
|
char *serverhostkeyblob, int sbloblen,
|
|
int minbits, BIGNUM *prime, BIGNUM *gen,
|
|
BIGNUM *client_dh_pub,
|
|
BIGNUM *server_dh_pub,
|
|
BIGNUM *shared_secret)
|
|
{
|
|
Buffer b;
|
|
static u_char digest[EVP_MAX_MD_SIZE];
|
|
EVP_MD *evp_md = EVP_sha1();
|
|
EVP_MD_CTX md;
|
|
|
|
buffer_init(&b);
|
|
buffer_put_string(&b, client_version_string, strlen(client_version_string));
|
|
buffer_put_string(&b, server_version_string, strlen(server_version_string));
|
|
|
|
/* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
|
|
buffer_put_int(&b, ckexinitlen+1);
|
|
buffer_put_char(&b, SSH2_MSG_KEXINIT);
|
|
buffer_append(&b, ckexinit, ckexinitlen);
|
|
buffer_put_int(&b, skexinitlen+1);
|
|
buffer_put_char(&b, SSH2_MSG_KEXINIT);
|
|
buffer_append(&b, skexinit, skexinitlen);
|
|
|
|
buffer_put_string(&b, serverhostkeyblob, sbloblen);
|
|
buffer_put_int(&b, minbits);
|
|
buffer_put_bignum2(&b, prime);
|
|
buffer_put_bignum2(&b, gen);
|
|
buffer_put_bignum2(&b, client_dh_pub);
|
|
buffer_put_bignum2(&b, server_dh_pub);
|
|
buffer_put_bignum2(&b, shared_secret);
|
|
|
|
#ifdef DEBUG_KEX
|
|
buffer_dump(&b);
|
|
#endif
|
|
|
|
EVP_DigestInit(&md, evp_md);
|
|
EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
|
|
EVP_DigestFinal(&md, digest, NULL);
|
|
|
|
buffer_free(&b);
|
|
|
|
#ifdef DEBUG_KEX
|
|
dump_digest(digest, evp_md->md_size);
|
|
#endif
|
|
return digest;
|
|
}
|
|
|
|
static u_char *
|
|
derive_key(int id, int need, u_char *hash, BIGNUM *shared_secret)
|
|
{
|
|
Buffer b;
|
|
EVP_MD *evp_md = EVP_sha1();
|
|
EVP_MD_CTX md;
|
|
char c = id;
|
|
int have;
|
|
int mdsz = evp_md->md_size;
|
|
u_char *digest = xmalloc(((need+mdsz-1)/mdsz)*mdsz);
|
|
|
|
buffer_init(&b);
|
|
buffer_put_bignum2(&b, shared_secret);
|
|
|
|
EVP_DigestInit(&md, evp_md);
|
|
EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b)); /* shared_secret K */
|
|
EVP_DigestUpdate(&md, hash, mdsz); /* transport-06 */
|
|
EVP_DigestUpdate(&md, &c, 1); /* key id */
|
|
EVP_DigestUpdate(&md, hash, mdsz); /* session id */
|
|
EVP_DigestFinal(&md, digest, NULL);
|
|
|
|
/* expand */
|
|
for (have = mdsz; need > have; have += mdsz) {
|
|
EVP_DigestInit(&md, evp_md);
|
|
EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
|
|
EVP_DigestUpdate(&md, hash, mdsz);
|
|
EVP_DigestUpdate(&md, digest, have);
|
|
EVP_DigestFinal(&md, digest + have, NULL);
|
|
}
|
|
buffer_free(&b);
|
|
#ifdef DEBUG_KEX
|
|
fprintf(stderr, "Digest '%c'== ", c);
|
|
dump_digest(digest, need);
|
|
#endif
|
|
return digest;
|
|
}
|
|
|
|
#define NKEYS 6
|
|
|
|
#define MAX_PROP 20
|
|
#define SEP ","
|
|
|
|
static char *
|
|
get_match(char *client, char *server)
|
|
{
|
|
char *sproposals[MAX_PROP];
|
|
char *c, *s, *p, *ret, *cp, *sp;
|
|
int i, j, nproposals;
|
|
|
|
c = cp = xstrdup(client);
|
|
s = sp = xstrdup(server);
|
|
|
|
for ((p = strsep(&sp, SEP)), i=0; p && *p != '\0';
|
|
(p = strsep(&sp, SEP)), i++) {
|
|
if (i < MAX_PROP)
|
|
sproposals[i] = p;
|
|
else
|
|
break;
|
|
}
|
|
nproposals = i;
|
|
|
|
for ((p = strsep(&cp, SEP)), i=0; p && *p != '\0';
|
|
(p = strsep(&cp, SEP)), i++) {
|
|
for (j = 0; j < nproposals; j++) {
|
|
if (strcmp(p, sproposals[j]) == 0) {
|
|
ret = xstrdup(p);
|
|
xfree(c);
|
|
xfree(s);
|
|
return ret;
|
|
}
|
|
}
|
|
}
|
|
xfree(c);
|
|
xfree(s);
|
|
return NULL;
|
|
}
|
|
static void
|
|
choose_enc(Enc *enc, char *client, char *server)
|
|
{
|
|
char *name = get_match(client, server);
|
|
if (name == NULL)
|
|
fatal("no matching cipher found: client %s server %s", client, server);
|
|
enc->cipher = cipher_by_name(name);
|
|
if (enc->cipher == NULL)
|
|
fatal("matching cipher is not supported: %s", name);
|
|
enc->name = name;
|
|
enc->enabled = 0;
|
|
enc->iv = NULL;
|
|
enc->key = NULL;
|
|
}
|
|
static void
|
|
choose_mac(Mac *mac, char *client, char *server)
|
|
{
|
|
char *name = get_match(client, server);
|
|
if (name == NULL)
|
|
fatal("no matching mac found: client %s server %s", client, server);
|
|
if (strcmp(name, "hmac-md5") == 0) {
|
|
mac->md = EVP_md5();
|
|
} else if (strcmp(name, "hmac-sha1") == 0) {
|
|
mac->md = EVP_sha1();
|
|
} else if (strcmp(name, "hmac-ripemd160@openssh.com") == 0) {
|
|
mac->md = EVP_ripemd160();
|
|
} else {
|
|
fatal("unsupported mac %s", name);
|
|
}
|
|
mac->name = name;
|
|
mac->mac_len = mac->md->md_size;
|
|
mac->key_len = (datafellows & SSH_BUG_HMAC) ? 16 : mac->mac_len;
|
|
mac->key = NULL;
|
|
mac->enabled = 0;
|
|
}
|
|
static void
|
|
choose_comp(Comp *comp, char *client, char *server)
|
|
{
|
|
char *name = get_match(client, server);
|
|
if (name == NULL)
|
|
fatal("no matching comp found: client %s server %s", client, server);
|
|
if (strcmp(name, "zlib") == 0) {
|
|
comp->type = 1;
|
|
} else if (strcmp(name, "none") == 0) {
|
|
comp->type = 0;
|
|
} else {
|
|
fatal("unsupported comp %s", name);
|
|
}
|
|
comp->name = name;
|
|
}
|
|
static void
|
|
choose_kex(Kex *k, char *client, char *server)
|
|
{
|
|
k->name = get_match(client, server);
|
|
if (k->name == NULL)
|
|
fatal("no kex alg");
|
|
if (strcmp(k->name, KEX_DH1) == 0) {
|
|
k->kex_type = DH_GRP1_SHA1;
|
|
} else if (strcmp(k->name, KEX_DHGEX) == 0) {
|
|
k->kex_type = DH_GEX_SHA1;
|
|
} else
|
|
fatal("bad kex alg %s", k->name);
|
|
}
|
|
static void
|
|
choose_hostkeyalg(Kex *k, char *client, char *server)
|
|
{
|
|
char *hostkeyalg = get_match(client, server);
|
|
if (hostkeyalg == NULL)
|
|
fatal("no hostkey alg");
|
|
k->hostkey_type = key_type_from_name(hostkeyalg);
|
|
if (k->hostkey_type == KEY_UNSPEC)
|
|
fatal("bad hostkey alg '%s'", hostkeyalg);
|
|
}
|
|
|
|
Kex *
|
|
kex_choose_conf(char *cprop[PROPOSAL_MAX], char *sprop[PROPOSAL_MAX], int server)
|
|
{
|
|
int mode;
|
|
int ctos; /* direction: if true client-to-server */
|
|
int need;
|
|
Kex *k;
|
|
|
|
k = xmalloc(sizeof(*k));
|
|
memset(k, 0, sizeof(*k));
|
|
k->server = server;
|
|
|
|
for (mode = 0; mode < MODE_MAX; mode++) {
|
|
int nenc, nmac, ncomp;
|
|
ctos = (!k->server && mode == MODE_OUT) || (k->server && mode == MODE_IN);
|
|
nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
|
|
nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
|
|
ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
|
|
choose_enc (&k->enc [mode], cprop[nenc], sprop[nenc]);
|
|
choose_mac (&k->mac [mode], cprop[nmac], sprop[nmac]);
|
|
choose_comp(&k->comp[mode], cprop[ncomp], sprop[ncomp]);
|
|
debug("kex: %s %s %s %s",
|
|
ctos ? "client->server" : "server->client",
|
|
k->enc[mode].name,
|
|
k->mac[mode].name,
|
|
k->comp[mode].name);
|
|
}
|
|
choose_kex(k, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
|
|
choose_hostkeyalg(k, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
|
|
sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
|
|
need = 0;
|
|
for (mode = 0; mode < MODE_MAX; mode++) {
|
|
if (need < k->enc[mode].cipher->key_len)
|
|
need = k->enc[mode].cipher->key_len;
|
|
if (need < k->enc[mode].cipher->block_size)
|
|
need = k->enc[mode].cipher->block_size;
|
|
if (need < k->mac[mode].key_len)
|
|
need = k->mac[mode].key_len;
|
|
}
|
|
/* XXX need runden? */
|
|
k->we_need = need;
|
|
return k;
|
|
}
|
|
|
|
int
|
|
kex_derive_keys(Kex *k, u_char *hash, BIGNUM *shared_secret)
|
|
{
|
|
int i;
|
|
int mode;
|
|
int ctos;
|
|
u_char *keys[NKEYS];
|
|
|
|
for (i = 0; i < NKEYS; i++)
|
|
keys[i] = derive_key('A'+i, k->we_need, hash, shared_secret);
|
|
|
|
for (mode = 0; mode < MODE_MAX; mode++) {
|
|
ctos = (!k->server && mode == MODE_OUT) || (k->server && mode == MODE_IN);
|
|
k->enc[mode].iv = keys[ctos ? 0 : 1];
|
|
k->enc[mode].key = keys[ctos ? 2 : 3];
|
|
k->mac[mode].key = keys[ctos ? 4 : 5];
|
|
}
|
|
return 0;
|
|
}
|