/* $OpenBSD: kex.c,v 1.136 2018/02/07 02:06:50 jsing Exp $ */ /* * 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" #include <signal.h> #include <stdarg.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #ifdef WITH_OPENSSL #include <openssl/crypto.h> #include <openssl/dh.h> #endif #include "ssh2.h" #include "packet.h" #include "compat.h" #include "cipher.h" #include "sshkey.h" #include "kex.h" #include "log.h" #include "mac.h" #include "match.h" #include "misc.h" #include "dispatch.h" #include "monitor.h" #include "ssherr.h" #include "sshbuf.h" #include "digest.h" /* prototype */ static int kex_choose_conf(struct ssh *); static int kex_input_newkeys(int, u_int32_t, struct ssh *); static const char *proposal_names[PROPOSAL_MAX] = { "KEX algorithms", "host key algorithms", "ciphers ctos", "ciphers stoc", "MACs ctos", "MACs stoc", "compression ctos", "compression stoc", "languages ctos", "languages stoc", }; struct kexalg { char *name; u_int type; int ec_nid; int hash_alg; }; static const struct kexalg kexalgs[] = { #ifdef WITH_OPENSSL { KEX_DH1, KEX_DH_GRP1_SHA1, 0, SSH_DIGEST_SHA1 }, { KEX_DH14_SHA1, KEX_DH_GRP14_SHA1, 0, SSH_DIGEST_SHA1 }, { KEX_DH14_SHA256, KEX_DH_GRP14_SHA256, 0, SSH_DIGEST_SHA256 }, { KEX_DH16_SHA512, KEX_DH_GRP16_SHA512, 0, SSH_DIGEST_SHA512 }, { KEX_DH18_SHA512, KEX_DH_GRP18_SHA512, 0, SSH_DIGEST_SHA512 }, { KEX_DHGEX_SHA1, KEX_DH_GEX_SHA1, 0, SSH_DIGEST_SHA1 }, #ifdef HAVE_EVP_SHA256 { KEX_DHGEX_SHA256, KEX_DH_GEX_SHA256, 0, SSH_DIGEST_SHA256 }, #endif /* HAVE_EVP_SHA256 */ #ifdef OPENSSL_HAS_ECC { KEX_ECDH_SHA2_NISTP256, KEX_ECDH_SHA2, NID_X9_62_prime256v1, SSH_DIGEST_SHA256 }, { KEX_ECDH_SHA2_NISTP384, KEX_ECDH_SHA2, NID_secp384r1, SSH_DIGEST_SHA384 }, # ifdef OPENSSL_HAS_NISTP521 { KEX_ECDH_SHA2_NISTP521, KEX_ECDH_SHA2, NID_secp521r1, SSH_DIGEST_SHA512 }, # endif /* OPENSSL_HAS_NISTP521 */ #endif /* OPENSSL_HAS_ECC */ #endif /* WITH_OPENSSL */ #if defined(HAVE_EVP_SHA256) || !defined(WITH_OPENSSL) { KEX_CURVE25519_SHA256, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 }, { KEX_CURVE25519_SHA256_OLD, KEX_C25519_SHA256, 0, SSH_DIGEST_SHA256 }, #endif /* HAVE_EVP_SHA256 || !WITH_OPENSSL */ { NULL, -1, -1, -1}, }; char * kex_alg_list(char sep) { char *ret = NULL, *tmp; size_t nlen, rlen = 0; const struct kexalg *k; for (k = kexalgs; k->name != NULL; k++) { if (ret != NULL) ret[rlen++] = sep; nlen = strlen(k->name); if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) { free(ret); return NULL; } ret = tmp; memcpy(ret + rlen, k->name, nlen + 1); rlen += nlen; } return ret; } static const struct kexalg * kex_alg_by_name(const char *name) { const struct kexalg *k; for (k = kexalgs; k->name != NULL; k++) { if (strcmp(k->name, name) == 0) return k; } return NULL; } /* Validate KEX method name list */ int kex_names_valid(const char *names) { char *s, *cp, *p; if (names == NULL || strcmp(names, "") == 0) return 0; if ((s = cp = strdup(names)) == NULL) return 0; for ((p = strsep(&cp, ",")); p && *p != '\0'; (p = strsep(&cp, ","))) { if (kex_alg_by_name(p) == NULL) { error("Unsupported KEX algorithm \"%.100s\"", p); free(s); return 0; } } debug3("kex names ok: [%s]", names); free(s); return 1; } /* * Concatenate algorithm names, avoiding duplicates in the process. * Caller must free returned string. */ char * kex_names_cat(const char *a, const char *b) { char *ret = NULL, *tmp = NULL, *cp, *p, *m; size_t len; if (a == NULL || *a == '\0') return NULL; if (b == NULL || *b == '\0') return strdup(a); if (strlen(b) > 1024*1024) return NULL; len = strlen(a) + strlen(b) + 2; if ((tmp = cp = strdup(b)) == NULL || (ret = calloc(1, len)) == NULL) { free(tmp); return NULL; } strlcpy(ret, a, len); for ((p = strsep(&cp, ",")); p && *p != '\0'; (p = strsep(&cp, ","))) { if ((m = match_list(ret, p, NULL)) != NULL) { free(m); continue; /* Algorithm already present */ } if (strlcat(ret, ",", len) >= len || strlcat(ret, p, len) >= len) { free(tmp); free(ret); return NULL; /* Shouldn't happen */ } } free(tmp); return ret; } /* * Assemble a list of algorithms from a default list and a string from a * configuration file. The user-provided string may begin with '+' to * indicate that it should be appended to the default or '-' that the * specified names should be removed. */ int kex_assemble_names(const char *def, char **list) { char *ret; if (list == NULL || *list == NULL || **list == '\0') { *list = strdup(def); return 0; } if (**list == '+') { if ((ret = kex_names_cat(def, *list + 1)) == NULL) return SSH_ERR_ALLOC_FAIL; free(*list); *list = ret; } else if (**list == '-') { if ((ret = match_filter_list(def, *list + 1)) == NULL) return SSH_ERR_ALLOC_FAIL; free(*list); *list = ret; } return 0; } /* put algorithm proposal into buffer */ int kex_prop2buf(struct sshbuf *b, char *proposal[PROPOSAL_MAX]) { u_int i; int r; sshbuf_reset(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++) { if ((r = sshbuf_put_u8(b, 0)) != 0) return r; } for (i = 0; i < PROPOSAL_MAX; i++) { if ((r = sshbuf_put_cstring(b, proposal[i])) != 0) return r; } if ((r = sshbuf_put_u8(b, 0)) != 0 || /* first_kex_packet_follows */ (r = sshbuf_put_u32(b, 0)) != 0) /* uint32 reserved */ return r; return 0; } /* parse buffer and return algorithm proposal */ int kex_buf2prop(struct sshbuf *raw, int *first_kex_follows, char ***propp) { struct sshbuf *b = NULL; u_char v; u_int i; char **proposal = NULL; int r; *propp = NULL; if ((proposal = calloc(PROPOSAL_MAX, sizeof(char *))) == NULL) return SSH_ERR_ALLOC_FAIL; if ((b = sshbuf_fromb(raw)) == NULL) { r = SSH_ERR_ALLOC_FAIL; goto out; } if ((r = sshbuf_consume(b, KEX_COOKIE_LEN)) != 0) /* skip cookie */ goto out; /* extract kex init proposal strings */ for (i = 0; i < PROPOSAL_MAX; i++) { if ((r = sshbuf_get_cstring(b, &(proposal[i]), NULL)) != 0) goto out; debug2("%s: %s", proposal_names[i], proposal[i]); } /* first kex follows / reserved */ if ((r = sshbuf_get_u8(b, &v)) != 0 || /* first_kex_follows */ (r = sshbuf_get_u32(b, &i)) != 0) /* reserved */ goto out; if (first_kex_follows != NULL) *first_kex_follows = v; debug2("first_kex_follows %d ", v); debug2("reserved %u ", i); r = 0; *propp = proposal; out: if (r != 0 && proposal != NULL) kex_prop_free(proposal); sshbuf_free(b); return r; } void kex_prop_free(char **proposal) { u_int i; if (proposal == NULL) return; for (i = 0; i < PROPOSAL_MAX; i++) free(proposal[i]); free(proposal); } /* ARGSUSED */ static int kex_protocol_error(int type, u_int32_t seq, struct ssh *ssh) { int r; error("kex protocol error: type %d seq %u", type, seq); if ((r = sshpkt_start(ssh, SSH2_MSG_UNIMPLEMENTED)) != 0 || (r = sshpkt_put_u32(ssh, seq)) != 0 || (r = sshpkt_send(ssh)) != 0) return r; return 0; } static void kex_reset_dispatch(struct ssh *ssh) { ssh_dispatch_range(ssh, SSH2_MSG_TRANSPORT_MIN, SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error); } static int kex_send_ext_info(struct ssh *ssh) { int r; char *algs; if ((algs = sshkey_alg_list(0, 1, 1, ',')) == NULL) return SSH_ERR_ALLOC_FAIL; if ((r = sshpkt_start(ssh, SSH2_MSG_EXT_INFO)) != 0 || (r = sshpkt_put_u32(ssh, 1)) != 0 || (r = sshpkt_put_cstring(ssh, "server-sig-algs")) != 0 || (r = sshpkt_put_cstring(ssh, algs)) != 0 || (r = sshpkt_send(ssh)) != 0) goto out; /* success */ r = 0; out: free(algs); return r; } int kex_send_newkeys(struct ssh *ssh) { int r; kex_reset_dispatch(ssh); if ((r = sshpkt_start(ssh, SSH2_MSG_NEWKEYS)) != 0 || (r = sshpkt_send(ssh)) != 0) return r; debug("SSH2_MSG_NEWKEYS sent"); debug("expecting SSH2_MSG_NEWKEYS"); ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_input_newkeys); if (ssh->kex->ext_info_c) if ((r = kex_send_ext_info(ssh)) != 0) return r; return 0; } int kex_input_ext_info(int type, u_int32_t seq, struct ssh *ssh) { struct kex *kex = ssh->kex; u_int32_t i, ninfo; char *name, *found; u_char *val; size_t vlen; int r; debug("SSH2_MSG_EXT_INFO received"); ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &kex_protocol_error); if ((r = sshpkt_get_u32(ssh, &ninfo)) != 0) return r; for (i = 0; i < ninfo; i++) { if ((r = sshpkt_get_cstring(ssh, &name, NULL)) != 0) return r; if ((r = sshpkt_get_string(ssh, &val, &vlen)) != 0) { free(name); return r; } if (strcmp(name, "server-sig-algs") == 0) { /* Ensure no \0 lurking in value */ if (memchr(val, '\0', vlen) != NULL) { error("%s: nul byte in %s", __func__, name); return SSH_ERR_INVALID_FORMAT; } debug("%s: %s=<%s>", __func__, name, val); found = match_list("rsa-sha2-256", val, NULL); if (found) { kex->rsa_sha2 = 256; free(found); } found = match_list("rsa-sha2-512", val, NULL); if (found) { kex->rsa_sha2 = 512; free(found); } } else debug("%s: %s (unrecognised)", __func__, name); free(name); free(val); } return sshpkt_get_end(ssh); } static int kex_input_newkeys(int type, u_int32_t seq, struct ssh *ssh) { struct kex *kex = ssh->kex; int r; debug("SSH2_MSG_NEWKEYS received"); ssh_dispatch_set(ssh, SSH2_MSG_NEWKEYS, &kex_protocol_error); ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit); if ((r = sshpkt_get_end(ssh)) != 0) return r; if ((r = ssh_set_newkeys(ssh, MODE_IN)) != 0) return r; kex->done = 1; sshbuf_reset(kex->peer); /* sshbuf_reset(kex->my); */ kex->flags &= ~KEX_INIT_SENT; free(kex->name); kex->name = NULL; return 0; } int kex_send_kexinit(struct ssh *ssh) { u_char *cookie; struct kex *kex = ssh->kex; int r; if (kex == NULL) return SSH_ERR_INTERNAL_ERROR; if (kex->flags & KEX_INIT_SENT) return 0; kex->done = 0; /* generate a random cookie */ if (sshbuf_len(kex->my) < KEX_COOKIE_LEN) return SSH_ERR_INVALID_FORMAT; if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL) return SSH_ERR_INTERNAL_ERROR; arc4random_buf(cookie, KEX_COOKIE_LEN); if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0 || (r = sshpkt_putb(ssh, kex->my)) != 0 || (r = sshpkt_send(ssh)) != 0) return r; debug("SSH2_MSG_KEXINIT sent"); kex->flags |= KEX_INIT_SENT; return 0; } /* ARGSUSED */ int kex_input_kexinit(int type, u_int32_t seq, struct ssh *ssh) { struct kex *kex = ssh->kex; const u_char *ptr; u_int i; size_t dlen; int r; debug("SSH2_MSG_KEXINIT received"); if (kex == NULL) return SSH_ERR_INVALID_ARGUMENT; ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, NULL); ptr = sshpkt_ptr(ssh, &dlen); if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0) return r; /* discard packet */ for (i = 0; i < KEX_COOKIE_LEN; i++) if ((r = sshpkt_get_u8(ssh, NULL)) != 0) return r; for (i = 0; i < PROPOSAL_MAX; i++) if ((r = sshpkt_get_string(ssh, NULL, NULL)) != 0) return r; /* * XXX RFC4253 sec 7: "each side MAY guess" - currently no supported * KEX method has the server move first, but a server might be using * a custom method or one that we otherwise don't support. We should * be prepared to remember first_kex_follows here so we can eat a * packet later. * XXX2 - RFC4253 is kind of ambiguous on what first_kex_follows means * for cases where the server *doesn't* go first. I guess we should * ignore it when it is set for these cases, which is what we do now. */ if ((r = sshpkt_get_u8(ssh, NULL)) != 0 || /* first_kex_follows */ (r = sshpkt_get_u32(ssh, NULL)) != 0 || /* reserved */ (r = sshpkt_get_end(ssh)) != 0) return r; if (!(kex->flags & KEX_INIT_SENT)) if ((r = kex_send_kexinit(ssh)) != 0) return r; if ((r = kex_choose_conf(ssh)) != 0) return r; if (kex->kex_type < KEX_MAX && kex->kex[kex->kex_type] != NULL) return (kex->kex[kex->kex_type])(ssh); return SSH_ERR_INTERNAL_ERROR; } int kex_new(struct ssh *ssh, char *proposal[PROPOSAL_MAX], struct kex **kexp) { struct kex *kex; int r; *kexp = NULL; if ((kex = calloc(1, sizeof(*kex))) == NULL) return SSH_ERR_ALLOC_FAIL; if ((kex->peer = sshbuf_new()) == NULL || (kex->my = sshbuf_new()) == NULL) { r = SSH_ERR_ALLOC_FAIL; goto out; } if ((r = kex_prop2buf(kex->my, proposal)) != 0) goto out; kex->done = 0; kex_reset_dispatch(ssh); ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit); r = 0; *kexp = kex; out: if (r != 0) kex_free(kex); return r; } void kex_free_newkeys(struct newkeys *newkeys) { if (newkeys == NULL) return; if (newkeys->enc.key) { explicit_bzero(newkeys->enc.key, newkeys->enc.key_len); free(newkeys->enc.key); newkeys->enc.key = NULL; } if (newkeys->enc.iv) { explicit_bzero(newkeys->enc.iv, newkeys->enc.iv_len); free(newkeys->enc.iv); newkeys->enc.iv = NULL; } free(newkeys->enc.name); explicit_bzero(&newkeys->enc, sizeof(newkeys->enc)); free(newkeys->comp.name); explicit_bzero(&newkeys->comp, sizeof(newkeys->comp)); mac_clear(&newkeys->mac); if (newkeys->mac.key) { explicit_bzero(newkeys->mac.key, newkeys->mac.key_len); free(newkeys->mac.key); newkeys->mac.key = NULL; } free(newkeys->mac.name); explicit_bzero(&newkeys->mac, sizeof(newkeys->mac)); explicit_bzero(newkeys, sizeof(*newkeys)); free(newkeys); } void kex_free(struct kex *kex) { u_int mode; #ifdef WITH_OPENSSL DH_free(kex->dh); #ifdef OPENSSL_HAS_ECC EC_KEY_free(kex->ec_client_key); #endif /* OPENSSL_HAS_ECC */ #endif /* WITH_OPENSSL */ for (mode = 0; mode < MODE_MAX; mode++) { kex_free_newkeys(kex->newkeys[mode]); kex->newkeys[mode] = NULL; } sshbuf_free(kex->peer); sshbuf_free(kex->my); free(kex->session_id); free(kex->client_version_string); free(kex->server_version_string); free(kex->failed_choice); free(kex->hostkey_alg); free(kex->name); free(kex); } int kex_setup(struct ssh *ssh, char *proposal[PROPOSAL_MAX]) { int r; if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0) return r; if ((r = kex_send_kexinit(ssh)) != 0) { /* we start */ kex_free(ssh->kex); ssh->kex = NULL; return r; } return 0; } /* * Request key re-exchange, returns 0 on success or a ssherr.h error * code otherwise. Must not be called if KEX is incomplete or in-progress. */ int kex_start_rekex(struct ssh *ssh) { if (ssh->kex == NULL) { error("%s: no kex", __func__); return SSH_ERR_INTERNAL_ERROR; } if (ssh->kex->done == 0) { error("%s: requested twice", __func__); return SSH_ERR_INTERNAL_ERROR; } ssh->kex->done = 0; return kex_send_kexinit(ssh); } static int choose_enc(struct sshenc *enc, char *client, char *server) { char *name = match_list(client, server, NULL); if (name == NULL) return SSH_ERR_NO_CIPHER_ALG_MATCH; if ((enc->cipher = cipher_by_name(name)) == NULL) { free(name); return SSH_ERR_INTERNAL_ERROR; } enc->name = name; enc->enabled = 0; enc->iv = NULL; enc->iv_len = cipher_ivlen(enc->cipher); enc->key = NULL; enc->key_len = cipher_keylen(enc->cipher); enc->block_size = cipher_blocksize(enc->cipher); return 0; } static int choose_mac(struct ssh *ssh, struct sshmac *mac, char *client, char *server) { char *name = match_list(client, server, NULL); if (name == NULL) return SSH_ERR_NO_MAC_ALG_MATCH; if (mac_setup(mac, name) < 0) { free(name); return SSH_ERR_INTERNAL_ERROR; } mac->name = name; mac->key = NULL; mac->enabled = 0; return 0; } static int choose_comp(struct sshcomp *comp, char *client, char *server) { char *name = match_list(client, server, NULL); if (name == NULL) return SSH_ERR_NO_COMPRESS_ALG_MATCH; 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 = COMP_NONE; } else { free(name); return SSH_ERR_INTERNAL_ERROR; } comp->name = name; return 0; } static int choose_kex(struct kex *k, char *client, char *server) { const struct kexalg *kexalg; k->name = match_list(client, server, NULL); debug("kex: algorithm: %s", k->name ? k->name : "(no match)"); if (k->name == NULL) return SSH_ERR_NO_KEX_ALG_MATCH; if ((kexalg = kex_alg_by_name(k->name)) == NULL) return SSH_ERR_INTERNAL_ERROR; k->kex_type = kexalg->type; k->hash_alg = kexalg->hash_alg; k->ec_nid = kexalg->ec_nid; return 0; } static int choose_hostkeyalg(struct kex *k, char *client, char *server) { k->hostkey_alg = match_list(client, server, NULL); debug("kex: host key algorithm: %s", k->hostkey_alg ? k->hostkey_alg : "(no match)"); if (k->hostkey_alg == NULL) return SSH_ERR_NO_HOSTKEY_ALG_MATCH; k->hostkey_type = sshkey_type_from_name(k->hostkey_alg); if (k->hostkey_type == KEY_UNSPEC) return SSH_ERR_INTERNAL_ERROR; k->hostkey_nid = sshkey_ecdsa_nid_from_name(k->hostkey_alg); return 0; } 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 int kex_choose_conf(struct ssh *ssh) { struct kex *kex = ssh->kex; struct newkeys *newkeys; char **my = NULL, **peer = NULL; char **cprop, **sprop; int nenc, nmac, ncomp; u_int mode, ctos, need, dh_need, authlen; int r, first_kex_follows; debug2("local %s KEXINIT proposal", kex->server ? "server" : "client"); if ((r = kex_buf2prop(kex->my, NULL, &my)) != 0) goto out; debug2("peer %s KEXINIT proposal", kex->server ? "client" : "server"); if ((r = kex_buf2prop(kex->peer, &first_kex_follows, &peer)) != 0) goto out; if (kex->server) { cprop=peer; sprop=my; } else { cprop=my; sprop=peer; } /* Check whether client supports ext_info_c */ if (kex->server) { char *ext; ext = match_list("ext-info-c", peer[PROPOSAL_KEX_ALGS], NULL); kex->ext_info_c = (ext != NULL); free(ext); } /* Algorithm Negotiation */ if ((r = choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS])) != 0) { kex->failed_choice = peer[PROPOSAL_KEX_ALGS]; peer[PROPOSAL_KEX_ALGS] = NULL; goto out; } if ((r = choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS], sprop[PROPOSAL_SERVER_HOST_KEY_ALGS])) != 0) { kex->failed_choice = peer[PROPOSAL_SERVER_HOST_KEY_ALGS]; peer[PROPOSAL_SERVER_HOST_KEY_ALGS] = NULL; goto out; } for (mode = 0; mode < MODE_MAX; mode++) { if ((newkeys = calloc(1, sizeof(*newkeys))) == NULL) { r = SSH_ERR_ALLOC_FAIL; goto out; } 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; if ((r = choose_enc(&newkeys->enc, cprop[nenc], sprop[nenc])) != 0) { kex->failed_choice = peer[nenc]; peer[nenc] = NULL; goto out; } authlen = cipher_authlen(newkeys->enc.cipher); /* ignore mac for authenticated encryption */ if (authlen == 0 && (r = choose_mac(ssh, &newkeys->mac, cprop[nmac], sprop[nmac])) != 0) { kex->failed_choice = peer[nmac]; peer[nmac] = NULL; goto out; } if ((r = choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp])) != 0) { kex->failed_choice = peer[ncomp]; peer[ncomp] = NULL; goto out; } debug("kex: %s cipher: %s MAC: %s compression: %s", ctos ? "client->server" : "server->client", newkeys->enc.name, authlen == 0 ? newkeys->mac.name : "<implicit>", newkeys->comp.name); } need = dh_need = 0; for (mode = 0; mode < MODE_MAX; mode++) { newkeys = kex->newkeys[mode]; need = MAXIMUM(need, newkeys->enc.key_len); need = MAXIMUM(need, newkeys->enc.block_size); need = MAXIMUM(need, newkeys->enc.iv_len); need = MAXIMUM(need, newkeys->mac.key_len); dh_need = MAXIMUM(dh_need, cipher_seclen(newkeys->enc.cipher)); dh_need = MAXIMUM(dh_need, newkeys->enc.block_size); dh_need = MAXIMUM(dh_need, newkeys->enc.iv_len); dh_need = MAXIMUM(dh_need, newkeys->mac.key_len); } /* XXX need runden? */ kex->we_need = need; kex->dh_need = dh_need; /* ignore the next message if the proposals do not match */ if (first_kex_follows && !proposals_match(my, peer)) ssh->dispatch_skip_packets = 1; r = 0; out: kex_prop_free(my); kex_prop_free(peer); return r; } static int derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen, const struct sshbuf *shared_secret, u_char **keyp) { struct kex *kex = ssh->kex; struct ssh_digest_ctx *hashctx = NULL; char c = id; u_int have; size_t mdsz; u_char *digest; int r; if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0) return SSH_ERR_INVALID_ARGUMENT; if ((digest = calloc(1, ROUNDUP(need, mdsz))) == NULL) { r = SSH_ERR_ALLOC_FAIL; goto out; } /* K1 = HASH(K || H || "A" || session_id) */ if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL || ssh_digest_update_buffer(hashctx, shared_secret) != 0 || ssh_digest_update(hashctx, hash, hashlen) != 0 || ssh_digest_update(hashctx, &c, 1) != 0 || ssh_digest_update(hashctx, kex->session_id, kex->session_id_len) != 0 || ssh_digest_final(hashctx, digest, mdsz) != 0) { r = SSH_ERR_LIBCRYPTO_ERROR; goto out; } ssh_digest_free(hashctx); hashctx = NULL; /* * expand key: * Kn = HASH(K || H || K1 || K2 || ... || Kn-1) * Key = K1 || K2 || ... || Kn */ for (have = mdsz; need > have; have += mdsz) { if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL || ssh_digest_update_buffer(hashctx, shared_secret) != 0 || ssh_digest_update(hashctx, hash, hashlen) != 0 || ssh_digest_update(hashctx, digest, have) != 0 || ssh_digest_final(hashctx, digest + have, mdsz) != 0) { r = SSH_ERR_LIBCRYPTO_ERROR; goto out; } ssh_digest_free(hashctx); hashctx = NULL; } #ifdef DEBUG_KEX fprintf(stderr, "key '%c'== ", c); dump_digest("key", digest, need); #endif *keyp = digest; digest = NULL; r = 0; out: free(digest); ssh_digest_free(hashctx); return r; } #define NKEYS 6 int kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen, const struct sshbuf *shared_secret) { struct kex *kex = ssh->kex; u_char *keys[NKEYS]; u_int i, j, mode, ctos; int r; for (i = 0; i < NKEYS; i++) { if ((r = derive_key(ssh, 'A'+i, kex->we_need, hash, hashlen, shared_secret, &keys[i])) != 0) { for (j = 0; j < i; j++) free(keys[j]); return r; } } for (mode = 0; mode < MODE_MAX; mode++) { ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN); kex->newkeys[mode]->enc.iv = keys[ctos ? 0 : 1]; kex->newkeys[mode]->enc.key = keys[ctos ? 2 : 3]; kex->newkeys[mode]->mac.key = keys[ctos ? 4 : 5]; } return 0; } #ifdef WITH_OPENSSL int kex_derive_keys_bn(struct ssh *ssh, u_char *hash, u_int hashlen, const BIGNUM *secret) { struct sshbuf *shared_secret; int r; if ((shared_secret = sshbuf_new()) == NULL) return SSH_ERR_ALLOC_FAIL; if ((r = sshbuf_put_bignum2(shared_secret, secret)) == 0) r = kex_derive_keys(ssh, hash, hashlen, shared_secret); sshbuf_free(shared_secret); return r; } #endif #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH) void dump_digest(char *msg, u_char *digest, int len) { fprintf(stderr, "%s\n", msg); sshbuf_dump_data(digest, len, stderr); } #endif