X-Git-Url: http://andersk.mit.edu/gitweb/openssh.git/blobdiff_plain/63284fbbb88cc0de8c33b78a2faa747f63783baa..HEAD:/kex.c diff --git a/kex.c b/kex.c index bf8fd95b..148cfee8 100644 --- a/kex.c +++ b/kex.c @@ -1,3 +1,4 @@ +/* $OpenBSD: kex.c,v 1.82 2009/10/24 11:13:54 andreas Exp $ */ /* * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved. * @@ -23,25 +24,39 @@ */ #include "includes.h" -RCSID("$OpenBSD: kex.c,v 1.47 2002/02/28 15:46:33 markus Exp $"); + +#include + +#include +#include +#include +#include +#include #include -#include "ssh2.h" #include "xmalloc.h" +#include "ssh2.h" #include "buffer.h" -#include "bufaux.h" #include "packet.h" #include "compat.h" #include "cipher.h" -#include "kex.h" #include "key.h" +#include "kex.h" #include "log.h" #include "mac.h" #include "match.h" #include "dispatch.h" - -#define KEX_COOKIE_LEN 16 +#include "monitor.h" +#include "roaming.h" + +#if OPENSSL_VERSION_NUMBER >= 0x00907000L +# if defined(HAVE_EVP_SHA256) +# define evp_ssh_sha256 EVP_sha256 +# else +extern const EVP_MD *evp_ssh_sha256(void); +# endif +#endif /* prototype */ static void kex_kexinit_finish(Kex *); @@ -51,16 +66,15 @@ static void kex_choose_conf(Kex *); static void kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX]) { - u_int32_t rand = 0; - int i; + u_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; - } + /* + * 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 */ @@ -69,13 +83,13 @@ kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX]) /* parse buffer and return algorithm proposal */ static char ** -kex_buf2prop(Buffer *raw) +kex_buf2prop(Buffer *raw, int *first_kex_follows) { Buffer b; - int i; + u_int i; char **proposal; - proposal = xmalloc(PROPOSAL_MAX * sizeof(char *)); + proposal = xcalloc(PROPOSAL_MAX, sizeof(char *)); buffer_init(&b); buffer_append(&b, buffer_ptr(raw), buffer_len(raw)); @@ -89,9 +103,11 @@ kex_buf2prop(Buffer *raw) } /* first kex follows / reserved */ i = buffer_get_char(&b); + if (first_kex_follows != NULL) + *first_kex_follows = i; debug2("kex_parse_kexinit: first_kex_follows %d ", i); i = buffer_get_int(&b); - debug2("kex_parse_kexinit: reserved %d ", i); + debug2("kex_parse_kexinit: reserved %u ", i); buffer_free(&b); return proposal; } @@ -99,13 +115,14 @@ kex_buf2prop(Buffer *raw) static void kex_prop_free(char **proposal) { - int i; + u_int i; for (i = 0; i < PROPOSAL_MAX; i++) xfree(proposal[i]); xfree(proposal); } +/* ARGSUSED */ static void kex_protocol_error(int type, u_int32_t seq, void *ctxt) { @@ -130,7 +147,7 @@ kex_finish(Kex *kex) /* packet_write_wait(); */ debug("SSH2_MSG_NEWKEYS sent"); - debug("waiting for SSH2_MSG_NEWKEYS"); + debug("expecting SSH2_MSG_NEWKEYS"); packet_read_expect(SSH2_MSG_NEWKEYS); packet_check_eom(); debug("SSH2_MSG_NEWKEYS received"); @@ -146,6 +163,10 @@ kex_finish(Kex *kex) void kex_send_kexinit(Kex *kex) { + u_int32_t rnd = 0; + u_char *cookie; + u_int i; + if (kex == NULL) { error("kex_send_kexinit: no kex, cannot rekey"); return; @@ -155,6 +176,17 @@ kex_send_kexinit(Kex *kex) 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) + rnd = arc4random(); + cookie[i] = rnd; + rnd >>= 8; + } packet_start(SSH2_MSG_KEXINIT); packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my)); packet_send(); @@ -162,12 +194,12 @@ kex_send_kexinit(Kex *kex) kex->flags |= KEX_INIT_SENT; } +/* ARGSUSED */ void kex_input_kexinit(int type, u_int32_t seq, void *ctxt) { char *ptr; - int dlen; - int i; + u_int i, dlen; Kex *kex = (Kex *)ctxt; debug("SSH2_MSG_KEXINIT received"); @@ -182,8 +214,8 @@ kex_input_kexinit(int type, u_int32_t seq, void *ctxt) packet_get_char(); for (i = 0; i < PROPOSAL_MAX; i++) xfree(packet_get_string(NULL)); - packet_get_char(); - packet_get_int(); + (void) packet_get_char(); + (void) packet_get_int(); packet_check_eom(); kex_kexinit_finish(kex); @@ -194,8 +226,7 @@ kex_setup(char *proposal[PROPOSAL_MAX]) { Kex *kex; - kex = xmalloc(sizeof(*kex)); - memset(kex, 0, sizeof(*kex)); + kex = xcalloc(1, sizeof(*kex)); buffer_init(&kex->peer); buffer_init(&kex->my); kex_prop2buf(&kex->my, proposal); @@ -215,14 +246,10 @@ kex_kexinit_finish(Kex *kex) kex_choose_conf(kex); - switch (kex->kex_type) { - case DH_GRP1_SHA1: - kexdh(kex); - break; - case DH_GEX_SHA1: - kexgex(kex); - break; - default: + if (kex->kex_type >= 0 && kex->kex_type < KEX_MAX && + kex->kex[kex->kex_type] != NULL) { + (kex->kex[kex->kex_type])(kex); + } else { fatal("Unsupported key exchange %d", kex->kex_type); } } @@ -232,7 +259,8 @@ 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); + 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; @@ -242,13 +270,15 @@ choose_enc(Enc *enc, char *client, char *server) 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("no matching mac found: client %s server %s", + client, server); + if (mac_setup(mac, name) < 0) fatal("unsupported mac %s", name); /* truncate the key */ if (datafellows & SSH_BUG_HMAC) @@ -257,34 +287,49 @@ choose_mac(Mac *mac, char *client, char *server) 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; + if (strcmp(name, "zlib@openssh.com") == 0) { + comp->type = COMP_DELAYED; + } else if (strcmp(name, "zlib") == 0) { + comp->type = COMP_ZLIB; } else if (strcmp(name, "none") == 0) { - comp->type = 0; + comp->type = COMP_NONE; } 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"); + fatal("Unable to negotiate a key exchange method"); 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; + k->kex_type = KEX_DH_GRP1_SHA1; + k->evp_md = EVP_sha1(); + } else if (strcmp(k->name, KEX_DH14) == 0) { + k->kex_type = KEX_DH_GRP14_SHA1; + k->evp_md = EVP_sha1(); + } else if (strcmp(k->name, KEX_DHGEX_SHA1) == 0) { + k->kex_type = KEX_DH_GEX_SHA1; + k->evp_md = EVP_sha1(); +#if OPENSSL_VERSION_NUMBER >= 0x00907000L + } else if (strcmp(k->name, KEX_DHGEX_SHA256) == 0) { + k->kex_type = KEX_DH_GEX_SHA256; + k->evp_md = evp_ssh_sha256(); +#endif } else fatal("bad kex alg %s", k->name); } + static void choose_hostkeyalg(Kex *k, char *client, char *server) { @@ -297,6 +342,30 @@ choose_hostkeyalg(Kex *k, char *client, char *server) xfree(hostkeyalg); } +static int +proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX]) +{ + static int check[] = { + PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1 + }; + int *idx; + char *p; + + for (idx = &check[0]; *idx != -1; idx++) { + if ((p = strchr(my[*idx], ',')) != NULL) + *p = '\0'; + if ((p = strchr(peer[*idx], ',')) != NULL) + *p = '\0'; + if (strcmp(my[*idx], peer[*idx]) != 0) { + debug2("proposal mismatch: my %s peer %s", + my[*idx], peer[*idx]); + return (0); + } + } + debug2("proposals match"); + return (1); +} + static void kex_choose_conf(Kex *kex) { @@ -304,12 +373,11 @@ kex_choose_conf(Kex *kex) char **my, **peer; char **cprop, **sprop; int nenc, nmac, ncomp; - int mode; - int ctos; /* direction: if true client-to-server */ - int need; + u_int mode, ctos, need; + int first_kex_follows, type; - my = kex_buf2prop(&kex->my); - peer = kex_buf2prop(&kex->peer); + my = kex_buf2prop(&kex->my, NULL); + peer = kex_buf2prop(&kex->peer, &first_kex_follows); if (kex->server) { cprop=peer; @@ -319,12 +387,22 @@ kex_choose_conf(Kex *kex) sprop=peer; } + /* Check whether server offers roaming */ + if (!kex->server) { + char *roaming; + roaming = match_list(KEX_RESUME, peer[PROPOSAL_KEX_ALGS], NULL); + if (roaming) { + kex->roaming = 1; + xfree(roaming); + } + } + /* Algorithm Negotiation */ for (mode = 0; mode < MODE_MAX; mode++) { - newkeys = xmalloc(sizeof(*newkeys)); - memset(newkeys, 0, sizeof(*newkeys)); + newkeys = xcalloc(1, sizeof(*newkeys)); kex->newkeys[mode] = newkeys; - ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN); + 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; @@ -353,29 +431,40 @@ kex_choose_conf(Kex *kex) /* XXX need runden? */ kex->we_need = need; + /* ignore the next message if the proposals do not match */ + if (first_kex_follows && !proposals_match(my, peer) && + !(datafellows & SSH_BUG_FIRSTKEX)) { + type = packet_read(); + debug2("skipping next packet (type %u)", type); + } + 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) +derive_key(Kex *kex, int id, u_int need, u_char *hash, u_int hashlen, + 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)); + u_int have; + int mdsz; + u_char *digest; + + if ((mdsz = EVP_MD_size(kex->evp_md)) <= 0) + fatal("bad kex md size %d", mdsz); + 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_DigestInit(&md, kex->evp_md); if (!(datafellows & SSH_BUG_DERIVEKEY)) EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b)); - EVP_DigestUpdate(&md, hash, mdsz); + EVP_DigestUpdate(&md, hash, hashlen); EVP_DigestUpdate(&md, &c, 1); EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len); EVP_DigestFinal(&md, digest, NULL); @@ -386,10 +475,10 @@ derive_key(Kex *kex, int id, int need, u_char *hash, BIGNUM *shared_secret) * Key = K1 || K2 || ... || Kn */ for (have = mdsz; need > have; have += mdsz) { - EVP_DigestInit(&md, evp_md); + EVP_DigestInit(&md, kex->evp_md); if (!(datafellows & SSH_BUG_DERIVEKEY)) EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b)); - EVP_DigestUpdate(&md, hash, mdsz); + EVP_DigestUpdate(&md, hash, hashlen); EVP_DigestUpdate(&md, digest, have); EVP_DigestFinal(&md, digest + have, NULL); } @@ -405,19 +494,22 @@ Newkeys *current_keys[MODE_MAX]; #define NKEYS 6 void -kex_derive_keys(Kex *kex, u_char *hash, BIGNUM *shared_secret) +kex_derive_keys(Kex *kex, u_char *hash, u_int hashlen, BIGNUM *shared_secret) { u_char *keys[NKEYS]; - int i, mode, ctos; + u_int i, mode, ctos; - for (i = 0; i < NKEYS; i++) - keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, shared_secret); + for (i = 0; i < NKEYS; i++) { + keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, hashlen, + shared_secret); + } - debug("kex_derive_keys"); + debug2("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); + 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]; @@ -434,14 +526,47 @@ kex_get_newkeys(int mode) return ret; } +void +derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus, + u_int8_t cookie[8], u_int8_t id[16]) +{ + const EVP_MD *evp_md = EVP_md5(); + EVP_MD_CTX md; + u_int8_t nbuf[2048], obuf[EVP_MAX_MD_SIZE]; + int len; + + EVP_DigestInit(&md, evp_md); + + len = BN_num_bytes(host_modulus); + if (len < (512 / 8) || (u_int)len > sizeof(nbuf)) + fatal("%s: bad host modulus (len %d)", __func__, len); + BN_bn2bin(host_modulus, nbuf); + EVP_DigestUpdate(&md, nbuf, len); + + len = BN_num_bytes(server_modulus); + if (len < (512 / 8) || (u_int)len > sizeof(nbuf)) + fatal("%s: bad server modulus (len %d)", __func__, len); + BN_bn2bin(server_modulus, nbuf); + EVP_DigestUpdate(&md, nbuf, len); + + EVP_DigestUpdate(&md, cookie, 8); + + EVP_DigestFinal(&md, obuf, NULL); + memcpy(id, obuf, 16); + + memset(nbuf, 0, sizeof(nbuf)); + memset(obuf, 0, sizeof(obuf)); + memset(&md, 0, sizeof(md)); +} + #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) void dump_digest(char *msg, u_char *digest, int len) { - int i; + u_int i; fprintf(stderr, "%s\n", msg); - for (i = 0; i< len; i++) { + for (i = 0; i < len; i++) { fprintf(stderr, "%02x", digest[i]); if (i%32 == 31) fprintf(stderr, "\n");