+/* $OpenBSD: kexgex.c,v 1.27 2006/08/03 03:34:42 deraadt Exp $ */
/*
* Copyright (c) 2000 Niels Provos. All rights reserved.
* Copyright (c) 2001 Markus Friedl. All rights reserved.
*/
#include "includes.h"
-RCSID("$OpenBSD: kexgex.c,v 1.2 2001/04/03 23:32:12 markus Exp $");
-#include <openssl/bn.h>
+#include <sys/types.h>
+
+#include <openssl/evp.h>
+#include <signal.h>
-#include "xmalloc.h"
#include "buffer.h"
-#include "bufaux.h"
#include "key.h"
+#include "cipher.h"
#include "kex.h"
-#include "log.h"
-#include "packet.h"
-#include "dh.h"
#include "ssh2.h"
-#include "compat.h"
-u_char *
+void
kexgex_hash(
+ const EVP_MD *evp_md,
char *client_version_string,
char *server_version_string,
char *ckexinit, int ckexinitlen,
char *skexinit, int skexinitlen,
- char *serverhostkeyblob, int sbloblen,
+ u_char *serverhostkeyblob, int sbloblen,
int min, int wantbits, int max, BIGNUM *prime, BIGNUM *gen,
BIGNUM *client_dh_pub,
BIGNUM *server_dh_pub,
- BIGNUM *shared_secret)
+ BIGNUM *shared_secret,
+ u_char **hash, u_int *hashlen)
{
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));
+ buffer_put_cstring(&b, client_version_string);
+ buffer_put_cstring(&b, server_version_string);
/* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
buffer_put_int(&b, ckexinitlen+1);
buffer_append(&b, skexinit, skexinitlen);
buffer_put_string(&b, serverhostkeyblob, sbloblen);
- if (min == -1 || max == -1)
+ if (min == -1 || max == -1)
buffer_put_int(&b, wantbits);
else {
buffer_put_int(&b, min);
#ifdef DEBUG_KEXDH
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_KEXDH
- dump_digest("hash", digest, evp_md->md_size);
-#endif
- return digest;
-}
-
-/* client */
-
-void
-kexgex_client(Kex *kex)
-{
- BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
- BIGNUM *p = NULL, *g = NULL;
- Key *server_host_key;
- u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
- u_int klen, kout, slen, sbloblen;
- int dlen, plen, min, max, nbits;
- DH *dh;
-
- nbits = dh_estimate(kex->we_need * 8);
-
- if (datafellows & SSH_OLD_DHGEX) {
- debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD sent");
-
- /* Old GEX request */
- packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD);
- packet_put_int(nbits);
- min = DH_GRP_MIN;
- max = DH_GRP_MAX;
- } else {
- debug("SSH2_MSG_KEX_DH_GEX_REQUEST sent");
-
- /* New GEX request */
- min = DH_GRP_MIN;
- max = DH_GRP_MAX;
- packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST);
- packet_put_int(min);
- packet_put_int(nbits);
- packet_put_int(max);
- }
-#ifdef DEBUG_KEXDH
- fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n",
- min, nbits, max);
-#endif
- packet_send();
-
- debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP");
- packet_read_expect(&plen, SSH2_MSG_KEX_DH_GEX_GROUP);
-
- if ((p = BN_new()) == NULL)
- fatal("BN_new");
- packet_get_bignum2(p, &dlen);
- if ((g = BN_new()) == NULL)
- fatal("BN_new");
- packet_get_bignum2(g, &dlen);
- packet_done();
-
- if (BN_num_bits(p) < min || BN_num_bits(p) > max)
- fatal("DH_GEX group out of range: %d !< %d !< %d",
- min, BN_num_bits(p), max);
-
- dh = dh_new_group(g, p);
- dh_gen_key(dh, kex->we_need * 8);
-
+ *hash = digest;
+ *hashlen = EVP_MD_size(evp_md);
#ifdef DEBUG_KEXDH
- DHparams_print_fp(stderr, dh);
- fprintf(stderr, "pub= ");
- BN_print_fp(stderr, dh->pub_key);
- fprintf(stderr, "\n");
+ dump_digest("hash", digest, *hashlen);
#endif
-
- debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
- /* generate and send 'e', client DH public key */
- packet_start(SSH2_MSG_KEX_DH_GEX_INIT);
- packet_put_bignum2(dh->pub_key);
- packet_send();
-
- debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY");
- packet_read_expect(&plen, SSH2_MSG_KEX_DH_GEX_REPLY);
-
- /* key, cert */
- server_host_key_blob = packet_get_string(&sbloblen);
- server_host_key = key_from_blob(server_host_key_blob, sbloblen);
- if (server_host_key == NULL)
- fatal("cannot decode server_host_key_blob");
-
- if (kex->check_host_key == NULL)
- fatal("cannot check server_host_key");
- kex->check_host_key(server_host_key);
-
- /* DH paramter f, server public DH key */
- dh_server_pub = BN_new();
- if (dh_server_pub == NULL)
- fatal("dh_server_pub == NULL");
- packet_get_bignum2(dh_server_pub, &dlen);
-
-#ifdef DEBUG_KEXDH
- fprintf(stderr, "dh_server_pub= ");
- BN_print_fp(stderr, dh_server_pub);
- fprintf(stderr, "\n");
- debug("bits %d", BN_num_bits(dh_server_pub));
-#endif
-
- /* signed H */
- signature = packet_get_string(&slen);
- packet_done();
-
- if (!dh_pub_is_valid(dh, dh_server_pub))
- packet_disconnect("bad server public DH value");
-
- klen = DH_size(dh);
- kbuf = xmalloc(klen);
- kout = DH_compute_key(kbuf, dh_server_pub, dh);
-#ifdef DEBUG_KEXDH
- dump_digest("shared secret", kbuf, kout);
-#endif
- shared_secret = BN_new();
- BN_bin2bn(kbuf, kout, shared_secret);
- memset(kbuf, 0, klen);
- xfree(kbuf);
-
- if (datafellows & SSH_OLD_DHGEX)
- min = max = -1;
-
- /* calc and verify H */
- hash = kexgex_hash(
- kex->client_version_string,
- kex->server_version_string,
- buffer_ptr(&kex->my), buffer_len(&kex->my),
- buffer_ptr(&kex->peer), buffer_len(&kex->peer),
- server_host_key_blob, sbloblen,
- min, nbits, max,
- dh->p, dh->g,
- dh->pub_key,
- dh_server_pub,
- shared_secret
- );
- xfree(server_host_key_blob);
- BN_free(dh_server_pub);
-
- if (key_verify(server_host_key, (u_char *)signature, slen, hash, 20) != 1)
- fatal("key_verify failed for server_host_key");
- key_free(server_host_key);
- xfree(signature);
-
- /* save session id */
- if (kex->session_id == NULL) {
- kex->session_id_len = 20;
- kex->session_id = xmalloc(kex->session_id_len);
- memcpy(kex->session_id, hash, kex->session_id_len);
- }
-
- kex_derive_keys(kex, hash, shared_secret);
- BN_clear_free(shared_secret);
-
- kex_send_newkeys();
-
- /* have keys, free DH */
- DH_free(dh);
-}
-
-/* server */
-
-void
-kexgex_server(Kex *kex)
-{
- BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
- Key *server_host_key;
- DH *dh = dh;
- u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
- u_int sbloblen, klen, kout;
- int min = -1, max = -1, nbits = -1, type, plen, dlen, slen;
-
- if (kex->load_host_key == NULL)
- fatal("Cannot load hostkey");
- server_host_key = kex->load_host_key(kex->hostkey_type);
- if (server_host_key == NULL)
- fatal("Unsupported hostkey type %d", kex->hostkey_type);
-
- type = packet_read(&plen);
- switch(type){
- case SSH2_MSG_KEX_DH_GEX_REQUEST:
- debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
- min = packet_get_int();
- nbits = packet_get_int();
- max = packet_get_int();
- min = MAX(DH_GRP_MIN, min);
- max = MIN(DH_GRP_MAX, max);
- break;
- case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD:
- debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received");
- nbits = packet_get_int();
- min = DH_GRP_MIN;
- max = DH_GRP_MAX;
- /* unused for old GEX */
- break;
- default:
- fatal("protocol error during kex, no DH_GEX_REQUEST");
- }
- packet_done();
-
- if (max < min || nbits < min || max < nbits)
- fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d",
- min, nbits, max);
-
- dh = choose_dh(min, nbits, max);
- if (dh == NULL)
- packet_disconnect("Protocol error: no matching DH grp found");
-
- debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
- packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
- packet_put_bignum2(dh->p);
- packet_put_bignum2(dh->g);
- packet_send();
-
- /* flush */
- packet_write_wait();
-
- /* Compute our exchange value in parallel with the client */
- dh_gen_key(dh, kex->we_need * 8);
-
- debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
- packet_read_expect(&plen, SSH2_MSG_KEX_DH_GEX_INIT);
-
- /* key, cert */
- dh_client_pub = BN_new();
- if (dh_client_pub == NULL)
- fatal("dh_client_pub == NULL");
- packet_get_bignum2(dh_client_pub, &dlen);
-
-#ifdef DEBUG_KEXDH
- fprintf(stderr, "dh_client_pub= ");
- BN_print_fp(stderr, dh_client_pub);
- fprintf(stderr, "\n");
- debug("bits %d", BN_num_bits(dh_client_pub));
-#endif
-
-#ifdef DEBUG_KEXDH
- DHparams_print_fp(stderr, dh);
- fprintf(stderr, "pub= ");
- BN_print_fp(stderr, dh->pub_key);
- fprintf(stderr, "\n");
-#endif
- if (!dh_pub_is_valid(dh, dh_client_pub))
- packet_disconnect("bad client public DH value");
-
- klen = DH_size(dh);
- kbuf = xmalloc(klen);
- kout = DH_compute_key(kbuf, dh_client_pub, dh);
-#ifdef DEBUG_KEXDH
- dump_digest("shared secret", kbuf, kout);
-#endif
- shared_secret = BN_new();
- BN_bin2bn(kbuf, kout, shared_secret);
- memset(kbuf, 0, klen);
- xfree(kbuf);
-
- key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
-
- if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD)
- min = max = -1;
-
- /* calc H */ /* XXX depends on 'kex' */
- hash = kexgex_hash(
- kex->client_version_string,
- kex->server_version_string,
- buffer_ptr(&kex->peer), buffer_len(&kex->peer),
- buffer_ptr(&kex->my), buffer_len(&kex->my),
- (char *)server_host_key_blob, sbloblen,
- min, nbits, max,
- dh->p, dh->g,
- dh_client_pub,
- dh->pub_key,
- shared_secret
- );
- BN_free(dh_client_pub);
-
- /* save session id := H */
- /* XXX hashlen depends on KEX */
- if (kex->session_id == NULL) {
- kex->session_id_len = 20;
- kex->session_id = xmalloc(kex->session_id_len);
- memcpy(kex->session_id, hash, kex->session_id_len);
- }
-
- /* sign H */
- /* XXX hashlen depends on KEX */
- key_sign(server_host_key, &signature, &slen, hash, 20);
-
- /* destroy_sensitive_data(); */
-
- /* send server hostkey, DH pubkey 'f' and singed H */
- debug("SSH2_MSG_KEX_DH_GEX_REPLY sent");
- packet_start(SSH2_MSG_KEX_DH_GEX_REPLY);
- packet_put_string((char *)server_host_key_blob, sbloblen);
- packet_put_bignum2(dh->pub_key); /* f */
- packet_put_string((char *)signature, slen);
- packet_send();
- xfree(signature);
- xfree(server_host_key_blob);
-
- kex_derive_keys(kex, hash, shared_secret);
- BN_clear_free(shared_secret);
-
- kex_send_newkeys();
-
- /* have keys, free DH */
- DH_free(dh);
-}
-
-void
-kexgex(Kex *kex)
-{
- if (kex->server)
- kexgex_server(kex);
- else
- kexgex_client(kex);
}
andersk / openssh.git / blobdiff