diff options
Diffstat (limited to 'crypto/openssh/kex.c')
| -rw-r--r-- | crypto/openssh/kex.c | 473 |
1 files changed, 473 insertions, 0 deletions
diff --git a/crypto/openssh/kex.c b/crypto/openssh/kex.c new file mode 100644 index 0000000..bdbf388 --- /dev/null +++ b/crypto/openssh/kex.c @@ -0,0 +1,473 @@ +/* + * Copyright (c) 2000, 2001 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 1.51 2002/06/24 14:55:38 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" +#include "monitor.h" + +#define KEX_COOKIE_LEN 16 + +/* Use privilege separation for sshd */ +int use_privsep; +struct monitor *pmonitor; + + +/* prototype */ +static void kex_kexinit_finish(Kex *); +static void kex_choose_conf(Kex *); + +/* put algorithm proposal into buffer */ +static void +kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX]) +{ + int i; + + buffer_clear(b); + /* + * add a dummy cookie, the cookie will be overwritten by + * kex_send_kexinit(), each time a kexinit is set + */ + for (i = 0; i < KEX_COOKIE_LEN; i++) + buffer_put_char(b, 0); + 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 */ +static 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; +} + +static void +kex_prop_free(char **proposal) +{ + int i; + + for (i = 0; i < PROPOSAL_MAX; i++) + xfree(proposal[i]); + xfree(proposal); +} + +static void +kex_protocol_error(int type, u_int32_t seq, void *ctxt) +{ + error("Hm, kex protocol error: type %d seq %u", type, seq); +} + +static void +kex_reset_dispatch(void) +{ + dispatch_range(SSH2_MSG_TRANSPORT_MIN, + SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error); + dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit); +} + +void +kex_finish(Kex *kex) +{ + kex_reset_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(SSH2_MSG_NEWKEYS); + packet_check_eom(); + debug("SSH2_MSG_NEWKEYS received"); + + kex->done = 1; + buffer_clear(&kex->peer); + /* buffer_clear(&kex->my); */ + kex->flags &= ~KEX_INIT_SENT; + xfree(kex->name); + kex->name = NULL; +} + +void +kex_send_kexinit(Kex *kex) +{ + u_int32_t rand = 0; + u_char *cookie; + int i; + + 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; + + /* generate a random cookie */ + if (buffer_len(&kex->my) < KEX_COOKIE_LEN) + fatal("kex_send_kexinit: kex proposal too short"); + cookie = buffer_ptr(&kex->my); + for (i = 0; i < KEX_COOKIE_LEN; i++) { + if (i % 4 == 0) + rand = arc4random(); + cookie[i] = rand; + rand >>= 8; + } + 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, u_int32_t seq, 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)); + (void) packet_get_char(); + (void) packet_get_int(); + packet_check_eom(); + + 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_reset_dispatch(); + + return kex; +} + +static 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); + } +} + +static 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); + if ((enc->cipher = cipher_by_name(name)) == NULL) + fatal("matching cipher is not supported: %s", name); + enc->name = name; + enc->enabled = 0; + enc->iv = NULL; + enc->key = NULL; + enc->key_len = cipher_keylen(enc->cipher); + enc->block_size = cipher_blocksize(enc->cipher); +} +static 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; +} +static 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; +} +static 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); +} +static 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); +} + +static 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.key_len) + need = newkeys->enc.key_len; + if (need < newkeys->enc.block_size) + need = newkeys->enc.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); +} + +static u_char * +derive_key(Kex *kex, int id, int need, u_char *hash, BIGNUM *shared_secret) +{ + Buffer b; + const EVP_MD *evp_md = EVP_sha1(); + EVP_MD_CTX md; + char c = id; + int have; + int mdsz = EVP_MD_size(evp_md); + 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); + if (!(datafellows & SSH_BUG_DERIVEKEY)) + 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); + if (!(datafellows & SSH_BUG_DERIVEKEY)) + 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 |
