-/* $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 1.9 2001/09/17 19:27:15 stevesk Exp $");
-#include <sys/types.h>
-
-#include <openssl/evp.h>
-#include <signal.h>
+#include <openssl/bn.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"
-void
+static u_char *
kexgex_hash(
- const EVP_MD *evp_md,
char *client_version_string,
char *server_version_string,
char *ckexinit, int ckexinitlen,
int min, int wantbits, int max, BIGNUM *prime, BIGNUM *gen,
BIGNUM *client_dh_pub,
BIGNUM *server_dh_pub,
- BIGNUM *shared_secret,
- u_char **hash, u_int *hashlen)
+ 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);
#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);
- *hash = digest;
- *hashlen = EVP_MD_size(evp_md);
+
+#ifdef DEBUG_KEXDH
+ dump_digest("hash", digest, evp_md->md_size);
+#endif
+ return digest;
+}
+
+/* client */
+
+static 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);
+
+#ifdef DEBUG_KEXDH
+ DHparams_print_fp(stderr, dh);
+ fprintf(stderr, "pub= ");
+ BN_print_fp(stderr, dh->pub_key);
+ fprintf(stderr, "\n");
+#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->verify_host_key == NULL)
+ fatal("cannot verify server_host_key");
+ if (kex->verify_host_key(server_host_key) == -1)
+ fatal("server_host_key verification failed");
+
+ /* 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
+ );
+ /* have keys, free DH */
+ DH_free(dh);
+ xfree(server_host_key_blob);
+ BN_free(dh_server_pub);
+
+ if (key_verify(server_host_key, 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_finish(kex);
+}
+
+/* server */
+
+static 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: %d", type);
+ }
+ 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
- dump_digest("hash", digest, *hashlen);
+ 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),
+ 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(server_host_key_blob, sbloblen);
+ packet_put_bignum2(dh->pub_key); /* f */
+ packet_put_string(signature, slen);
+ packet_send();
+ xfree(signature);
+ xfree(server_host_key_blob);
+ /* have keys, free DH */
+ DH_free(dh);
+
+ kex_derive_keys(kex, hash, shared_secret);
+ BN_clear_free(shared_secret);
+
+ kex_finish(kex);
+}
+
+void
+kexgex(Kex *kex)
+{
+ if (kex->server)
+ kexgex_server(kex);
+ else
+ kexgex_client(kex);
}
andersk / gssapi-openssh.git / blobdiff