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Diffstat (limited to 'kexgssc.c')
| -rw-r--r-- | kexgssc.c | 606 |
1 files changed, 606 insertions, 0 deletions
diff --git a/kexgssc.c b/kexgssc.c new file mode 100644 index 000000000..f6e1405eb --- /dev/null +++ b/kexgssc.c @@ -0,0 +1,606 @@ +/* + * Copyright (c) 2001-2009 Simon Wilkinson. 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" + +#if defined(GSSAPI) && defined(WITH_OPENSSL) + +#include "includes.h" + +#include <openssl/crypto.h> +#include <openssl/bn.h> + +#include <string.h> + +#include "xmalloc.h" +#include "sshbuf.h" +#include "ssh2.h" +#include "sshkey.h" +#include "cipher.h" +#include "kex.h" +#include "log.h" +#include "packet.h" +#include "dh.h" +#include "digest.h" +#include "ssherr.h" + +#include "ssh-gss.h" + +int +kexgss_client(struct ssh *ssh) +{ + struct kex *kex = ssh->kex; + gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER, + recv_tok = GSS_C_EMPTY_BUFFER, + gssbuf, msg_tok = GSS_C_EMPTY_BUFFER, *token_ptr; + Gssctxt *ctxt; + OM_uint32 maj_status, min_status, ret_flags; + struct sshbuf *server_blob = NULL; + struct sshbuf *shared_secret = NULL; + struct sshbuf *server_host_key_blob = NULL; + struct sshbuf *empty = NULL; + u_char *msg; + int type = 0; + int first = 1; + u_char hash[SSH_DIGEST_MAX_LENGTH]; + size_t hashlen; + u_char c; + int r; + + /* Initialise our GSSAPI world */ + ssh_gssapi_build_ctx(&ctxt); + if (ssh_gssapi_id_kex(ctxt, kex->name, kex->kex_type) + == GSS_C_NO_OID) + fatal("Couldn't identify host exchange"); + + if (ssh_gssapi_import_name(ctxt, kex->gss_host)) + fatal("Couldn't import hostname"); + + if (kex->gss_client && + ssh_gssapi_client_identity(ctxt, kex->gss_client)) + fatal("Couldn't acquire client credentials"); + + /* Step 1 */ + switch (kex->kex_type) { + case KEX_GSS_GRP1_SHA1: + case KEX_GSS_GRP14_SHA1: + case KEX_GSS_GRP14_SHA256: + case KEX_GSS_GRP16_SHA512: + r = kex_dh_keypair(kex); + break; + case KEX_GSS_NISTP256_SHA256: + r = kex_ecdh_keypair(kex); + break; + case KEX_GSS_C25519_SHA256: + r = kex_c25519_keypair(kex); + break; + default: + fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type); + } + if (r != 0) + return r; + + token_ptr = GSS_C_NO_BUFFER; + + do { + debug("Calling gss_init_sec_context"); + + maj_status = ssh_gssapi_init_ctx(ctxt, + kex->gss_deleg_creds, token_ptr, &send_tok, + &ret_flags); + + if (GSS_ERROR(maj_status)) { + /* XXX Useles code: Missing send? */ + if (send_tok.length != 0) { + if ((r = sshpkt_start(ssh, + SSH2_MSG_KEXGSS_CONTINUE)) != 0 || + (r = sshpkt_put_string(ssh, send_tok.value, + send_tok.length)) != 0) + fatal("sshpkt failed: %s", ssh_err(r)); + } + fatal("gss_init_context failed"); + } + + /* If we've got an old receive buffer get rid of it */ + if (token_ptr != GSS_C_NO_BUFFER) + gss_release_buffer(&min_status, &recv_tok); + + if (maj_status == GSS_S_COMPLETE) { + /* If mutual state flag is not true, kex fails */ + if (!(ret_flags & GSS_C_MUTUAL_FLAG)) + fatal("Mutual authentication failed"); + + /* If integ avail flag is not true kex fails */ + if (!(ret_flags & GSS_C_INTEG_FLAG)) + fatal("Integrity check failed"); + } + + /* + * If we have data to send, then the last message that we + * received cannot have been a 'complete'. + */ + if (send_tok.length != 0) { + if (first) { + if ((r = sshpkt_start(ssh, SSH2_MSG_KEXGSS_INIT)) != 0 || + (r = sshpkt_put_string(ssh, send_tok.value, + send_tok.length)) != 0 || + (r = sshpkt_put_stringb(ssh, kex->client_pub)) != 0) + fatal("failed to construct packet: %s", ssh_err(r)); + first = 0; + } else { + if ((r = sshpkt_start(ssh, SSH2_MSG_KEXGSS_CONTINUE)) != 0 || + (r = sshpkt_put_string(ssh, send_tok.value, + send_tok.length)) != 0) + fatal("failed to construct packet: %s", ssh_err(r)); + } + if ((r = sshpkt_send(ssh)) != 0) + fatal("failed to send packet: %s", ssh_err(r)); + gss_release_buffer(&min_status, &send_tok); + + /* If we've sent them data, they should reply */ + do { + type = ssh_packet_read(ssh); + if (type == SSH2_MSG_KEXGSS_HOSTKEY) { + debug("Received KEXGSS_HOSTKEY"); + if (server_host_key_blob) + fatal("Server host key received more than once"); + if ((r = sshpkt_getb_froms(ssh, &server_host_key_blob)) != 0) + fatal("Failed to read server host key: %s", ssh_err(r)); + } + } while (type == SSH2_MSG_KEXGSS_HOSTKEY); + + switch (type) { + case SSH2_MSG_KEXGSS_CONTINUE: + debug("Received GSSAPI_CONTINUE"); + if (maj_status == GSS_S_COMPLETE) + fatal("GSSAPI Continue received from server when complete"); + if ((r = ssh_gssapi_sshpkt_get_buffer_desc(ssh, + &recv_tok)) != 0 || + (r = sshpkt_get_end(ssh)) != 0) + fatal("Failed to read token: %s", ssh_err(r)); + break; + case SSH2_MSG_KEXGSS_COMPLETE: + debug("Received GSSAPI_COMPLETE"); + if (msg_tok.value != NULL) + fatal("Received GSSAPI_COMPLETE twice?"); + if ((r = sshpkt_getb_froms(ssh, &server_blob)) != 0 || + (r = ssh_gssapi_sshpkt_get_buffer_desc(ssh, + &msg_tok)) != 0) + fatal("Failed to read message: %s", ssh_err(r)); + + /* Is there a token included? */ + if ((r = sshpkt_get_u8(ssh, &c)) != 0) + fatal("sshpkt failed: %s", ssh_err(r)); + if (c) { + if ((r = ssh_gssapi_sshpkt_get_buffer_desc( + ssh, &recv_tok)) != 0) + fatal("Failed to read token: %s", ssh_err(r)); + /* If we're already complete - protocol error */ + if (maj_status == GSS_S_COMPLETE) + sshpkt_disconnect(ssh, "Protocol error: received token when complete"); + } else { + /* No token included */ + if (maj_status != GSS_S_COMPLETE) + sshpkt_disconnect(ssh, "Protocol error: did not receive final token"); + } + if ((r = sshpkt_get_end(ssh)) != 0) { + fatal("Expecting end of packet."); + } + break; + case SSH2_MSG_KEXGSS_ERROR: + debug("Received Error"); + if ((r = sshpkt_get_u32(ssh, &maj_status)) != 0 || + (r = sshpkt_get_u32(ssh, &min_status)) != 0 || + (r = sshpkt_get_string(ssh, &msg, NULL)) != 0 || + (r = sshpkt_get_string(ssh, NULL, NULL)) != 0 || /* lang tag */ + (r = sshpkt_get_end(ssh)) != 0) + fatal("sshpkt_get failed: %s", ssh_err(r)); + fatal("GSSAPI Error: \n%.400s", msg); + default: + sshpkt_disconnect(ssh, "Protocol error: didn't expect packet type %d", + type); + } + token_ptr = &recv_tok; + } else { + /* No data, and not complete */ + if (maj_status != GSS_S_COMPLETE) + fatal("Not complete, and no token output"); + } + } while (maj_status & GSS_S_CONTINUE_NEEDED); + + /* + * We _must_ have received a COMPLETE message in reply from the + * server, which will have set server_blob and msg_tok + */ + + if (type != SSH2_MSG_KEXGSS_COMPLETE) + fatal("Didn't receive a SSH2_MSG_KEXGSS_COMPLETE when I expected it"); + + /* compute shared secret */ + switch (kex->kex_type) { + case KEX_GSS_GRP1_SHA1: + case KEX_GSS_GRP14_SHA1: + case KEX_GSS_GRP14_SHA256: + case KEX_GSS_GRP16_SHA512: + r = kex_dh_dec(kex, server_blob, &shared_secret); + break; + case KEX_GSS_C25519_SHA256: + if (sshbuf_ptr(server_blob)[sshbuf_len(server_blob)] & 0x80) + fatal("The received key has MSB of last octet set!"); + r = kex_c25519_dec(kex, server_blob, &shared_secret); + break; + case KEX_GSS_NISTP256_SHA256: + if (sshbuf_len(server_blob) != 65) + fatal("The received NIST-P256 key did not match" + "expected length (expected 65, got %zu)", sshbuf_len(server_blob)); + + if (sshbuf_ptr(server_blob)[0] != POINT_CONVERSION_UNCOMPRESSED) + fatal("The received NIST-P256 key does not have first octet 0x04"); + + r = kex_ecdh_dec(kex, server_blob, &shared_secret); + break; + default: + r = SSH_ERR_INVALID_ARGUMENT; + break; + } + if (r != 0) + goto out; + + if ((empty = sshbuf_new()) == NULL) { + r = SSH_ERR_ALLOC_FAIL; + goto out; + } + + hashlen = sizeof(hash); + if ((r = kex_gen_hash( + kex->hash_alg, + kex->client_version, + kex->server_version, + kex->my, + kex->peer, + (server_host_key_blob ? server_host_key_blob : empty), + kex->client_pub, + server_blob, + shared_secret, + hash, &hashlen)) != 0) + fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type); + + gssbuf.value = hash; + gssbuf.length = hashlen; + + /* Verify that the hash matches the MIC we just got. */ + if (GSS_ERROR(ssh_gssapi_checkmic(ctxt, &gssbuf, &msg_tok))) + sshpkt_disconnect(ssh, "Hash's MIC didn't verify"); + + gss_release_buffer(&min_status, &msg_tok); + + if (kex->gss_deleg_creds) + ssh_gssapi_credentials_updated(ctxt); + + if (gss_kex_context == NULL) + gss_kex_context = ctxt; + else + ssh_gssapi_delete_ctx(&ctxt); + + if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0) + r = kex_send_newkeys(ssh); + +out: + explicit_bzero(hash, sizeof(hash)); + explicit_bzero(kex->c25519_client_key, sizeof(kex->c25519_client_key)); + sshbuf_free(empty); + sshbuf_free(server_host_key_blob); + sshbuf_free(server_blob); + sshbuf_free(shared_secret); + sshbuf_free(kex->client_pub); + kex->client_pub = NULL; + return r; +} + +int +kexgssgex_client(struct ssh *ssh) +{ + struct kex *kex = ssh->kex; + gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER, + recv_tok = GSS_C_EMPTY_BUFFER, gssbuf, + msg_tok = GSS_C_EMPTY_BUFFER, *token_ptr; + Gssctxt *ctxt; + OM_uint32 maj_status, min_status, ret_flags; + struct sshbuf *shared_secret = NULL; + BIGNUM *p = NULL; + BIGNUM *g = NULL; + struct sshbuf *buf = NULL; + struct sshbuf *server_host_key_blob = NULL; + struct sshbuf *server_blob = NULL; + BIGNUM *dh_server_pub = NULL; + u_char *msg; + int type = 0; + int first = 1; + u_char hash[SSH_DIGEST_MAX_LENGTH]; + size_t hashlen; + const BIGNUM *pub_key, *dh_p, *dh_g; + int nbits = 0, min = DH_GRP_MIN, max = DH_GRP_MAX; + struct sshbuf *empty = NULL; + u_char c; + int r; + + /* Initialise our GSSAPI world */ + ssh_gssapi_build_ctx(&ctxt); + if (ssh_gssapi_id_kex(ctxt, kex->name, kex->kex_type) + == GSS_C_NO_OID) + fatal("Couldn't identify host exchange"); + + if (ssh_gssapi_import_name(ctxt, kex->gss_host)) + fatal("Couldn't import hostname"); + + if (kex->gss_client && + ssh_gssapi_client_identity(ctxt, kex->gss_client)) + fatal("Couldn't acquire client credentials"); + + debug("Doing group exchange"); + nbits = dh_estimate(kex->dh_need * 8); + + kex->min = DH_GRP_MIN; + kex->max = DH_GRP_MAX; + kex->nbits = nbits; + if ((r = sshpkt_start(ssh, SSH2_MSG_KEXGSS_GROUPREQ)) != 0 || + (r = sshpkt_put_u32(ssh, min)) != 0 || + (r = sshpkt_put_u32(ssh, nbits)) != 0 || + (r = sshpkt_put_u32(ssh, max)) != 0 || + (r = sshpkt_send(ssh)) != 0) + fatal("Failed to construct a packet: %s", ssh_err(r)); + + if ((r = ssh_packet_read_expect(ssh, SSH2_MSG_KEXGSS_GROUP)) != 0) + fatal("Error: %s", ssh_err(r)); + + if ((r = sshpkt_get_bignum2(ssh, &p)) != 0 || + (r = sshpkt_get_bignum2(ssh, &g)) != 0 || + (r = sshpkt_get_end(ssh)) != 0) + fatal("shpkt_get_bignum2 failed: %s", ssh_err(r)); + + if (BN_num_bits(p) < min || BN_num_bits(p) > max) + fatal("GSSGRP_GEX group out of range: %d !< %d !< %d", + min, BN_num_bits(p), max); + + if ((kex->dh = dh_new_group(g, p)) == NULL) + fatal("dn_new_group() failed"); + p = g = NULL; /* belong to kex->dh now */ + + if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0) + goto out; + DH_get0_key(kex->dh, &pub_key, NULL); + + token_ptr = GSS_C_NO_BUFFER; + + do { + /* Step 2 - call GSS_Init_sec_context() */ + debug("Calling gss_init_sec_context"); + + maj_status = ssh_gssapi_init_ctx(ctxt, + kex->gss_deleg_creds, token_ptr, &send_tok, + &ret_flags); + + if (GSS_ERROR(maj_status)) { + /* XXX Useles code: Missing send? */ + if (send_tok.length != 0) { + if ((r = sshpkt_start(ssh, + SSH2_MSG_KEXGSS_CONTINUE)) != 0 || + (r = sshpkt_put_string(ssh, send_tok.value, + send_tok.length)) != 0) + fatal("sshpkt failed: %s", ssh_err(r)); + } + fatal("gss_init_context failed"); + } + + /* If we've got an old receive buffer get rid of it */ + if (token_ptr != GSS_C_NO_BUFFER) + gss_release_buffer(&min_status, &recv_tok); + + if (maj_status == GSS_S_COMPLETE) { + /* If mutual state flag is not true, kex fails */ + if (!(ret_flags & GSS_C_MUTUAL_FLAG)) + fatal("Mutual authentication failed"); + + /* If integ avail flag is not true kex fails */ + if (!(ret_flags & GSS_C_INTEG_FLAG)) + fatal("Integrity check failed"); + } + + /* + * If we have data to send, then the last message that we + * received cannot have been a 'complete'. + */ + if (send_tok.length != 0) { + if (first) { + if ((r = sshpkt_start(ssh, SSH2_MSG_KEXGSS_INIT)) != 0 || + (r = sshpkt_put_string(ssh, send_tok.value, + send_tok.length)) != 0 || + (r = sshpkt_put_bignum2(ssh, pub_key)) != 0) + fatal("sshpkt failed: %s", ssh_err(r)); + first = 0; + } else { + if ((r = sshpkt_start(ssh, SSH2_MSG_KEXGSS_CONTINUE)) != 0 || + (r = sshpkt_put_string(ssh,send_tok.value, + send_tok.length)) != 0) + fatal("sshpkt failed: %s", ssh_err(r)); + } + if ((r = sshpkt_send(ssh)) != 0) + fatal("sshpkt_send failed: %s", ssh_err(r)); + gss_release_buffer(&min_status, &send_tok); + + /* If we've sent them data, they should reply */ + do { + type = ssh_packet_read(ssh); + if (type == SSH2_MSG_KEXGSS_HOSTKEY) { + debug("Received KEXGSS_HOSTKEY"); + if (server_host_key_blob) + fatal("Server host key received more than once"); + if ((r = sshpkt_getb_froms(ssh, &server_host_key_blob)) != 0) + fatal("sshpkt failed: %s", ssh_err(r)); + } + } while (type == SSH2_MSG_KEXGSS_HOSTKEY); + + switch (type) { + case SSH2_MSG_KEXGSS_CONTINUE: + debug("Received GSSAPI_CONTINUE"); + if (maj_status == GSS_S_COMPLETE) + fatal("GSSAPI Continue received from server when complete"); + if ((r = ssh_gssapi_sshpkt_get_buffer_desc(ssh, + &recv_tok)) != 0 || + (r = sshpkt_get_end(ssh)) != 0) + fatal("sshpkt failed: %s", ssh_err(r)); + break; + case SSH2_MSG_KEXGSS_COMPLETE: + debug("Received GSSAPI_COMPLETE"); + if (msg_tok.value != NULL) + fatal("Received GSSAPI_COMPLETE twice?"); + if ((r = sshpkt_getb_froms(ssh, &server_blob)) != 0 || + (r = ssh_gssapi_sshpkt_get_buffer_desc(ssh, + &msg_tok)) != 0) + fatal("sshpkt failed: %s", ssh_err(r)); + + /* Is there a token included? */ + if ((r = sshpkt_get_u8(ssh, &c)) != 0) + fatal("sshpkt failed: %s", ssh_err(r)); + if (c) { + if ((r = ssh_gssapi_sshpkt_get_buffer_desc( + ssh, &recv_tok)) != 0 || + (r = sshpkt_get_end(ssh)) != 0) + fatal("sshpkt failed: %s", ssh_err(r)); + /* If we're already complete - protocol error */ + if (maj_status == GSS_S_COMPLETE) + sshpkt_disconnect(ssh, "Protocol error: received token when complete"); + } else { + /* No token included */ + if (maj_status != GSS_S_COMPLETE) + sshpkt_disconnect(ssh, "Protocol error: did not receive final token"); + } + break; + case SSH2_MSG_KEXGSS_ERROR: + debug("Received Error"); + if ((r = sshpkt_get_u32(ssh, &maj_status)) != 0 || + (r = sshpkt_get_u32(ssh, &min_status)) != 0 || + (r = sshpkt_get_string(ssh, &msg, NULL)) != 0 || + (r = sshpkt_get_string(ssh, NULL, NULL)) != 0 || /* lang tag */ + (r = sshpkt_get_end(ssh)) != 0) + fatal("sshpkt failed: %s", ssh_err(r)); + fatal("GSSAPI Error: \n%.400s", msg); + default: + sshpkt_disconnect(ssh, "Protocol error: didn't expect packet type %d", + type); + } + token_ptr = &recv_tok; + } else { + /* No data, and not complete */ + if (maj_status != GSS_S_COMPLETE) + fatal("Not complete, and no token output"); + } + } while (maj_status & GSS_S_CONTINUE_NEEDED); + + /* + * We _must_ have received a COMPLETE message in reply from the + * server, which will have set dh_server_pub and msg_tok + */ + + if (type != SSH2_MSG_KEXGSS_COMPLETE) + fatal("Didn't receive a SSH2_MSG_KEXGSS_COMPLETE when I expected it"); + + /* 7. C verifies that the key Q_S is valid */ + /* 8. C computes shared secret */ + if ((buf = sshbuf_new()) == NULL || + (r = sshbuf_put_stringb(buf, server_blob)) != 0 || + (r = sshbuf_get_bignum2(buf, &dh_server_pub)) != 0) + goto out; + sshbuf_free(buf); + buf = NULL; + + if ((shared_secret = sshbuf_new()) == NULL) { + r = SSH_ERR_ALLOC_FAIL; + goto out; + } + + if ((r = kex_dh_compute_key(kex, dh_server_pub, shared_secret)) != 0) + goto out; + if ((empty = sshbuf_new()) == NULL) { + r = SSH_ERR_ALLOC_FAIL; + goto out; + } + + DH_get0_pqg(kex->dh, &dh_p, NULL, &dh_g); + hashlen = sizeof(hash); + if ((r = kexgex_hash( + kex->hash_alg, + kex->client_version, + kex->server_version, + kex->my, + kex->peer, + (server_host_key_blob ? server_host_key_blob : empty), + kex->min, kex->nbits, kex->max, + dh_p, dh_g, + pub_key, + dh_server_pub, + sshbuf_ptr(shared_secret), sshbuf_len(shared_secret), + hash, &hashlen)) != 0) + fatal("Failed to calculate hash: %s", ssh_err(r)); + + gssbuf.value = hash; + gssbuf.length = hashlen; + + /* Verify that the hash matches the MIC we just got. */ + if (GSS_ERROR(ssh_gssapi_checkmic(ctxt, &gssbuf, &msg_tok))) + sshpkt_disconnect(ssh, "Hash's MIC didn't verify"); + + gss_release_buffer(&min_status, &msg_tok); + + /* save session id */ + if (kex->session_id == NULL) { + kex->session_id_len = hashlen; + kex->session_id = xmalloc(kex->session_id_len); + memcpy(kex->session_id, hash, kex->session_id_len); + } + + if (kex->gss_deleg_creds) + ssh_gssapi_credentials_updated(ctxt); + + if (gss_kex_context == NULL) + gss_kex_context = ctxt; + else + ssh_gssapi_delete_ctx(&ctxt); + + /* Finally derive the keys and send them */ + if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0) + r = kex_send_newkeys(ssh); +out: + sshbuf_free(buf); + sshbuf_free(server_blob); + sshbuf_free(empty); + explicit_bzero(hash, sizeof(hash)); + DH_free(kex->dh); + kex->dh = NULL; + BN_clear_free(dh_server_pub); + sshbuf_free(shared_secret); + sshbuf_free(server_host_key_blob); + return r; +} +#endif /* defined(GSSAPI) && defined(WITH_OPENSSL) */ |