| /* |
| * 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. |
| */ |
| |
| #include "includes.h" |
| RCSID("$OpenBSD: kex.c,v 1.31 2001/04/04 22:04:34 markus Exp $"); |
| |
| #include <openssl/crypto.h> |
| |
| #include "ssh2.h" |
| #include "xmalloc.h" |
| #include "buffer.h" |
| #include "bufaux.h" |
| #include "packet.h" |
| #include "compat.h" |
| #include "cipher.h" |
| #include "kex.h" |
| #include "key.h" |
| #include "log.h" |
| #include "mac.h" |
| #include "match.h" |
| #include "dispatch.h" |
| |
| #define KEX_COOKIE_LEN 16 |
| |
| void kex_kexinit_finish(Kex *kex); |
| void kex_choose_conf(Kex *k); |
| |
| /* put algorithm proposal into buffer */ |
| void |
| kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX]) |
| { |
| u_int32_t rand = 0; |
| int i; |
| |
| buffer_clear(b); |
| for (i = 0; i < KEX_COOKIE_LEN; i++) { |
| if (i % 4 == 0) |
| rand = arc4random(); |
| buffer_put_char(b, rand & 0xff); |
| rand >>= 8; |
| } |
| for (i = 0; i < PROPOSAL_MAX; i++) |
| buffer_put_cstring(b, proposal[i]); |
| buffer_put_char(b, 0); /* first_kex_packet_follows */ |
| buffer_put_int(b, 0); /* uint32 reserved */ |
| } |
| |
| /* parse buffer and return algorithm proposal */ |
| char ** |
| kex_buf2prop(Buffer *raw) |
| { |
| Buffer b; |
| int i; |
| char **proposal; |
| |
| proposal = xmalloc(PROPOSAL_MAX * sizeof(char *)); |
| |
| buffer_init(&b); |
| buffer_append(&b, buffer_ptr(raw), buffer_len(raw)); |
| /* skip cookie */ |
| for (i = 0; i < KEX_COOKIE_LEN; i++) |
| buffer_get_char(&b); |
| /* extract kex init proposal strings */ |
| for (i = 0; i < PROPOSAL_MAX; i++) { |
| proposal[i] = buffer_get_string(&b,NULL); |
| debug2("kex_parse_kexinit: %s", proposal[i]); |
| } |
| /* first kex follows / reserved */ |
| i = buffer_get_char(&b); |
| debug2("kex_parse_kexinit: first_kex_follows %d ", i); |
| i = buffer_get_int(&b); |
| debug2("kex_parse_kexinit: reserved %d ", i); |
| buffer_free(&b); |
| return proposal; |
| } |
| |
| void |
| kex_prop_free(char **proposal) |
| { |
| int i; |
| |
| for (i = 0; i < PROPOSAL_MAX; i++) |
| xfree(proposal[i]); |
| xfree(proposal); |
| } |
| |
| void |
| kex_protocol_error(int type, int plen, void *ctxt) |
| { |
| error("Hm, kex protocol error: type %d plen %d", type, plen); |
| } |
| |
| void |
| kex_clear_dispatch(void) |
| { |
| int i; |
| |
| /* Numbers 30-49 are used for kex packets */ |
| for (i = 30; i <= 49; i++) |
| dispatch_set(i, &kex_protocol_error); |
| } |
| |
| void |
| kex_finish(Kex *kex) |
| { |
| int plen; |
| |
| kex_clear_dispatch(); |
| |
| packet_start(SSH2_MSG_NEWKEYS); |
| packet_send(); |
| /* packet_write_wait(); */ |
| debug("SSH2_MSG_NEWKEYS sent"); |
| |
| debug("waiting for SSH2_MSG_NEWKEYS"); |
| packet_read_expect(&plen, SSH2_MSG_NEWKEYS); |
| debug("SSH2_MSG_NEWKEYS received"); |
| kex->done = 1; |
| buffer_clear(&kex->peer); |
| /* buffer_clear(&kex->my); */ |
| kex->flags &= ~KEX_INIT_SENT; |
| } |
| |
| void |
| kex_send_kexinit(Kex *kex) |
| { |
| if (kex == NULL) { |
| error("kex_send_kexinit: no kex, cannot rekey"); |
| return; |
| } |
| if (kex->flags & KEX_INIT_SENT) { |
| debug("KEX_INIT_SENT"); |
| return; |
| } |
| kex->done = 0; |
| packet_start(SSH2_MSG_KEXINIT); |
| packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my)); |
| packet_send(); |
| debug("SSH2_MSG_KEXINIT sent"); |
| kex->flags |= KEX_INIT_SENT; |
| } |
| |
| void |
| kex_input_kexinit(int type, int plen, void *ctxt) |
| { |
| char *ptr; |
| int dlen; |
| int i; |
| Kex *kex = (Kex *)ctxt; |
| |
| debug("SSH2_MSG_KEXINIT received"); |
| if (kex == NULL) |
| fatal("kex_input_kexinit: no kex, cannot rekey"); |
| |
| ptr = packet_get_raw(&dlen); |
| buffer_append(&kex->peer, ptr, dlen); |
| |
| /* discard packet */ |
| for (i = 0; i < KEX_COOKIE_LEN; i++) |
| packet_get_char(); |
| for (i = 0; i < PROPOSAL_MAX; i++) |
| xfree(packet_get_string(NULL)); |
| packet_get_char(); |
| packet_get_int(); |
| packet_done(); |
| |
| kex_kexinit_finish(kex); |
| } |
| |
| Kex * |
| kex_setup(char *proposal[PROPOSAL_MAX]) |
| { |
| Kex *kex; |
| |
| kex = xmalloc(sizeof(*kex)); |
| memset(kex, 0, sizeof(*kex)); |
| buffer_init(&kex->peer); |
| buffer_init(&kex->my); |
| kex_prop2buf(&kex->my, proposal); |
| kex->done = 0; |
| |
| kex_send_kexinit(kex); /* we start */ |
| kex_clear_dispatch(); |
| dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit); |
| |
| return kex; |
| } |
| |
| void |
| kex_kexinit_finish(Kex *kex) |
| { |
| if (!(kex->flags & KEX_INIT_SENT)) |
| kex_send_kexinit(kex); |
| |
| kex_choose_conf(kex); |
| |
| switch(kex->kex_type) { |
| case DH_GRP1_SHA1: |
| kexdh(kex); |
| break; |
| case DH_GEX_SHA1: |
| kexgex(kex); |
| break; |
| default: |
| fatal("Unsupported key exchange %d", kex->kex_type); |
| } |
| } |
| |
| void |
| choose_enc(Enc *enc, char *client, char *server) |
| { |
| char *name = match_list(client, server, NULL); |
| 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; |
| } |
| void |
| choose_mac(Mac *mac, char *client, char *server) |
| { |
| char *name = match_list(client, server, NULL); |
| if (name == NULL) |
| fatal("no matching mac found: client %s server %s", client, server); |
| if (mac_init(mac, name) < 0) |
| fatal("unsupported mac %s", name); |
| /* truncate the key */ |
| if (datafellows & SSH_BUG_HMAC) |
| mac->key_len = 16; |
| mac->name = name; |
| mac->key = NULL; |
| mac->enabled = 0; |
| } |
| void |
| choose_comp(Comp *comp, char *client, char *server) |
| { |
| char *name = match_list(client, server, NULL); |
| 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; |
| } |
| void |
| choose_kex(Kex *k, char *client, char *server) |
| { |
| k->name = match_list(client, server, NULL); |
| 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); |
| } |
| void |
| choose_hostkeyalg(Kex *k, char *client, char *server) |
| { |
| char *hostkeyalg = match_list(client, server, NULL); |
| 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); |
| xfree(hostkeyalg); |
| } |
| |
| void |
| kex_choose_conf(Kex *kex) |
| { |
| Newkeys *newkeys; |
| char **my, **peer; |
| char **cprop, **sprop; |
| int nenc, nmac, ncomp; |
| int mode; |
| int ctos; /* direction: if true client-to-server */ |
| int need; |
| |
| my = kex_buf2prop(&kex->my); |
| peer = kex_buf2prop(&kex->peer); |
| |
| if (kex->server) { |
| cprop=peer; |
| sprop=my; |
| } else { |
| cprop=my; |
| sprop=peer; |
| } |
| |
| /* Algorithm Negotiation */ |
| for (mode = 0; mode < MODE_MAX; mode++) { |
| newkeys = xmalloc(sizeof(*newkeys)); |
| memset(newkeys, 0, sizeof(*newkeys)); |
| kex->newkeys[mode] = newkeys; |
| ctos = (!kex->server && mode == MODE_OUT) || (kex->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 (&newkeys->enc, cprop[nenc], sprop[nenc]); |
| choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]); |
| choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]); |
| debug("kex: %s %s %s %s", |
| ctos ? "client->server" : "server->client", |
| newkeys->enc.name, |
| newkeys->mac.name, |
| newkeys->comp.name); |
| } |
| choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]); |
| choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS], |
| sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]); |
| need = 0; |
| for (mode = 0; mode < MODE_MAX; mode++) { |
| newkeys = kex->newkeys[mode]; |
| if (need < newkeys->enc.cipher->key_len) |
| need = newkeys->enc.cipher->key_len; |
| if (need < newkeys->enc.cipher->block_size) |
| need = newkeys->enc.cipher->block_size; |
| if (need < newkeys->mac.key_len) |
| need = newkeys->mac.key_len; |
| } |
| /* XXX need runden? */ |
| kex->we_need = need; |
| |
| kex_prop_free(my); |
| kex_prop_free(peer); |
| } |
| |
| u_char * |
| derive_key(Kex *kex, 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(roundup(need, mdsz)); |
| |
| buffer_init(&b); |
| buffer_put_bignum2(&b, shared_secret); |
| |
| /* K1 = HASH(K || H || "A" || session_id) */ |
| EVP_DigestInit(&md, evp_md); |
| EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b)); |
| EVP_DigestUpdate(&md, hash, mdsz); |
| EVP_DigestUpdate(&md, &c, 1); |
| EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len); |
| EVP_DigestFinal(&md, digest, NULL); |
| |
| /* |
| * expand key: |
| * Kn = HASH(K || H || K1 || K2 || ... || Kn-1) |
| * Key = K1 || K2 || ... || Kn |
| */ |
| 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, "key '%c'== ", c); |
| dump_digest("key", digest, need); |
| #endif |
| return digest; |
| } |
| |
| Newkeys *current_keys[MODE_MAX]; |
| |
| #define NKEYS 6 |
| void |
| kex_derive_keys(Kex *kex, u_char *hash, BIGNUM *shared_secret) |
| { |
| u_char *keys[NKEYS]; |
| int i, mode, ctos; |
| |
| for (i = 0; i < NKEYS; i++) |
| keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, shared_secret); |
| |
| debug("kex_derive_keys"); |
| for (mode = 0; mode < MODE_MAX; mode++) { |
| current_keys[mode] = kex->newkeys[mode]; |
| kex->newkeys[mode] = NULL; |
| ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN); |
| current_keys[mode]->enc.iv = keys[ctos ? 0 : 1]; |
| current_keys[mode]->enc.key = keys[ctos ? 2 : 3]; |
| current_keys[mode]->mac.key = keys[ctos ? 4 : 5]; |
| } |
| } |
| |
| Newkeys * |
| kex_get_newkeys(int mode) |
| { |
| Newkeys *ret; |
| |
| ret = current_keys[mode]; |
| current_keys[mode] = NULL; |
| return ret; |
| } |
| |
| #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) |
| void |
| dump_digest(char *msg, u_char *digest, int len) |
| { |
| int i; |
| |
| fprintf(stderr, "%s\n", msg); |
| for (i = 0; i< len; i++){ |
| fprintf(stderr, "%02x", digest[i]); |
| if (i%32 == 31) |
| fprintf(stderr, "\n"); |
| else if (i%8 == 7) |
| fprintf(stderr, " "); |
| } |
| fprintf(stderr, "\n"); |
| } |
| #endif |