| /* $OpenBSD: ssh_api.c,v 1.14 2019/01/21 10:29:56 djm Exp $ */ |
| /* |
| * Copyright (c) 2012 Markus Friedl. All rights reserved. |
| * |
| * Permission to use, copy, modify, and distribute this software for any |
| * purpose with or without fee is hereby granted, provided that the above |
| * copyright notice and this permission notice appear in all copies. |
| * |
| * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES |
| * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF |
| * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR |
| * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES |
| * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN |
| * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF |
| * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. |
| */ |
| |
| #include "includes.h" |
| |
| #include "ssh_api.h" |
| #include "compat.h" |
| #include "log.h" |
| #include "authfile.h" |
| #include "sshkey.h" |
| #include "misc.h" |
| #include "ssh2.h" |
| #include "version.h" |
| #include "myproposal.h" |
| #include "ssherr.h" |
| #include "sshbuf.h" |
| |
| #include "openbsd-compat/openssl-compat.h" |
| |
| #include <string.h> |
| |
| int _ssh_exchange_banner(struct ssh *); |
| int _ssh_send_banner(struct ssh *, struct sshbuf *); |
| int _ssh_read_banner(struct ssh *, struct sshbuf *); |
| int _ssh_order_hostkeyalgs(struct ssh *); |
| int _ssh_verify_host_key(struct sshkey *, struct ssh *); |
| struct sshkey *_ssh_host_public_key(int, int, struct ssh *); |
| struct sshkey *_ssh_host_private_key(int, int, struct ssh *); |
| int _ssh_host_key_sign(struct ssh *, struct sshkey *, struct sshkey *, |
| u_char **, size_t *, const u_char *, size_t, const char *); |
| |
| /* |
| * stubs for the server side implementation of kex. |
| * disable privsep so our stubs will never be called. |
| */ |
| int use_privsep = 0; |
| int mm_sshkey_sign(struct sshkey *, u_char **, u_int *, |
| u_char *, u_int, char *, u_int); |
| DH *mm_choose_dh(int, int, int); |
| |
| /* Define these two variables here so that they are part of the library */ |
| u_char *session_id2 = NULL; |
| u_int session_id2_len = 0; |
| |
| int |
| mm_sshkey_sign(struct sshkey *key, u_char **sigp, u_int *lenp, |
| u_char *data, u_int datalen, char *alg, u_int compat) |
| { |
| return (-1); |
| } |
| |
| DH * |
| mm_choose_dh(int min, int nbits, int max) |
| { |
| return (NULL); |
| } |
| |
| /* API */ |
| |
| int |
| ssh_init(struct ssh **sshp, int is_server, struct kex_params *kex_params) |
| { |
| char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT }; |
| struct ssh *ssh; |
| char **proposal; |
| static int called; |
| int r; |
| |
| if (!called) { |
| seed_rng(); |
| called = 1; |
| } |
| |
| if ((ssh = ssh_packet_set_connection(NULL, -1, -1)) == NULL) |
| return SSH_ERR_ALLOC_FAIL; |
| if (is_server) |
| ssh_packet_set_server(ssh); |
| |
| /* Initialize key exchange */ |
| proposal = kex_params ? kex_params->proposal : myproposal; |
| if ((r = kex_ready(ssh, proposal)) != 0) { |
| ssh_free(ssh); |
| return r; |
| } |
| ssh->kex->server = is_server; |
| if (is_server) { |
| #ifdef WITH_OPENSSL |
| ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_kem_server; |
| ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_kem_server; |
| ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_kem_server; |
| ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_kem_server; |
| ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_kem_server; |
| ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; |
| ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_server; |
| # ifdef OPENSSL_HAS_ECC |
| ssh->kex->kex[KEX_ECDH_SHA2] = kex_kem_server; |
| # endif |
| #endif /* WITH_OPENSSL */ |
| ssh->kex->kex[KEX_C25519_SHA256] = kex_kem_server; |
| ssh->kex->kex[KEX_KEM_SNTRUP4591761X25519_SHA512] = kex_kem_server; |
| ssh->kex->load_host_public_key=&_ssh_host_public_key; |
| ssh->kex->load_host_private_key=&_ssh_host_private_key; |
| ssh->kex->sign=&_ssh_host_key_sign; |
| } else { |
| #ifdef WITH_OPENSSL |
| ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_kem_client; |
| ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_kem_client; |
| ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_kem_client; |
| ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_kem_client; |
| ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_kem_client; |
| ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client; |
| ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client; |
| # ifdef OPENSSL_HAS_ECC |
| ssh->kex->kex[KEX_ECDH_SHA2] = kex_kem_client; |
| # endif |
| #endif /* WITH_OPENSSL */ |
| ssh->kex->kex[KEX_C25519_SHA256] = kex_kem_client; |
| ssh->kex->kex[KEX_KEM_SNTRUP4591761X25519_SHA512] = kex_kem_client; |
| ssh->kex->verify_host_key =&_ssh_verify_host_key; |
| } |
| *sshp = ssh; |
| return 0; |
| } |
| |
| void |
| ssh_free(struct ssh *ssh) |
| { |
| struct key_entry *k; |
| |
| ssh_packet_close(ssh); |
| /* |
| * we've only created the public keys variants in case we |
| * are a acting as a server. |
| */ |
| while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) { |
| TAILQ_REMOVE(&ssh->public_keys, k, next); |
| if (ssh->kex && ssh->kex->server) |
| sshkey_free(k->key); |
| free(k); |
| } |
| while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) { |
| TAILQ_REMOVE(&ssh->private_keys, k, next); |
| free(k); |
| } |
| if (ssh->kex) |
| kex_free(ssh->kex); |
| free(ssh); |
| } |
| |
| void |
| ssh_set_app_data(struct ssh *ssh, void *app_data) |
| { |
| ssh->app_data = app_data; |
| } |
| |
| void * |
| ssh_get_app_data(struct ssh *ssh) |
| { |
| return ssh->app_data; |
| } |
| |
| /* Returns < 0 on error, 0 otherwise */ |
| int |
| ssh_add_hostkey(struct ssh *ssh, struct sshkey *key) |
| { |
| struct sshkey *pubkey = NULL; |
| struct key_entry *k = NULL, *k_prv = NULL; |
| int r; |
| |
| if (ssh->kex->server) { |
| if ((r = sshkey_from_private(key, &pubkey)) != 0) |
| return r; |
| if ((k = malloc(sizeof(*k))) == NULL || |
| (k_prv = malloc(sizeof(*k_prv))) == NULL) { |
| free(k); |
| sshkey_free(pubkey); |
| return SSH_ERR_ALLOC_FAIL; |
| } |
| k_prv->key = key; |
| TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next); |
| |
| /* add the public key, too */ |
| k->key = pubkey; |
| TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); |
| r = 0; |
| } else { |
| if ((k = malloc(sizeof(*k))) == NULL) |
| return SSH_ERR_ALLOC_FAIL; |
| k->key = key; |
| TAILQ_INSERT_TAIL(&ssh->public_keys, k, next); |
| r = 0; |
| } |
| |
| return r; |
| } |
| |
| int |
| ssh_set_verify_host_key_callback(struct ssh *ssh, |
| int (*cb)(struct sshkey *, struct ssh *)) |
| { |
| if (cb == NULL || ssh->kex == NULL) |
| return SSH_ERR_INVALID_ARGUMENT; |
| |
| ssh->kex->verify_host_key = cb; |
| |
| return 0; |
| } |
| |
| int |
| ssh_input_append(struct ssh *ssh, const u_char *data, size_t len) |
| { |
| return sshbuf_put(ssh_packet_get_input(ssh), data, len); |
| } |
| |
| int |
| ssh_packet_next(struct ssh *ssh, u_char *typep) |
| { |
| int r; |
| u_int32_t seqnr; |
| u_char type; |
| |
| /* |
| * Try to read a packet. Return SSH_MSG_NONE if no packet or not |
| * enough data. |
| */ |
| *typep = SSH_MSG_NONE; |
| if (sshbuf_len(ssh->kex->client_version) == 0 || |
| sshbuf_len(ssh->kex->server_version) == 0) |
| return _ssh_exchange_banner(ssh); |
| /* |
| * If we enough data and a dispatch function then |
| * call the function and get the next packet. |
| * Otherwise return the packet type to the caller so it |
| * can decide how to go on. |
| * |
| * We will only call the dispatch function for: |
| * 20-29 Algorithm negotiation |
| * 30-49 Key exchange method specific (numbers can be reused for |
| * different authentication methods) |
| */ |
| for (;;) { |
| if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0) |
| return r; |
| if (type > 0 && type < DISPATCH_MAX && |
| type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX && |
| ssh->dispatch[type] != NULL) { |
| if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0) |
| return r; |
| } else { |
| *typep = type; |
| return 0; |
| } |
| } |
| } |
| |
| const u_char * |
| ssh_packet_payload(struct ssh *ssh, size_t *lenp) |
| { |
| return sshpkt_ptr(ssh, lenp); |
| } |
| |
| int |
| ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len) |
| { |
| int r; |
| |
| if ((r = sshpkt_start(ssh, type)) != 0 || |
| (r = sshpkt_put(ssh, data, len)) != 0 || |
| (r = sshpkt_send(ssh)) != 0) |
| return r; |
| return 0; |
| } |
| |
| const u_char * |
| ssh_output_ptr(struct ssh *ssh, size_t *len) |
| { |
| struct sshbuf *output = ssh_packet_get_output(ssh); |
| |
| *len = sshbuf_len(output); |
| return sshbuf_ptr(output); |
| } |
| |
| int |
| ssh_output_consume(struct ssh *ssh, size_t len) |
| { |
| return sshbuf_consume(ssh_packet_get_output(ssh), len); |
| } |
| |
| int |
| ssh_output_space(struct ssh *ssh, size_t len) |
| { |
| return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len)); |
| } |
| |
| int |
| ssh_input_space(struct ssh *ssh, size_t len) |
| { |
| return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len)); |
| } |
| |
| /* Read other side's version identification. */ |
| int |
| _ssh_read_banner(struct ssh *ssh, struct sshbuf *banner) |
| { |
| struct sshbuf *input = ssh_packet_get_input(ssh); |
| const char *mismatch = "Protocol mismatch.\r\n"; |
| const u_char *s = sshbuf_ptr(input); |
| u_char c; |
| char *cp, *remote_version; |
| int r, remote_major, remote_minor, expect_nl; |
| size_t n, j; |
| |
| for (j = n = 0;;) { |
| sshbuf_reset(banner); |
| expect_nl = 0; |
| for (;;) { |
| if (j >= sshbuf_len(input)) |
| return 0; /* insufficient data in input buf */ |
| c = s[j++]; |
| if (c == '\r') { |
| expect_nl = 1; |
| continue; |
| } |
| if (c == '\n') |
| break; |
| if (expect_nl) |
| goto bad; |
| if ((r = sshbuf_put_u8(banner, c)) != 0) |
| return r; |
| if (sshbuf_len(banner) > SSH_MAX_BANNER_LEN) |
| goto bad; |
| } |
| if (sshbuf_len(banner) >= 4 && |
| memcmp(sshbuf_ptr(banner), "SSH-", 4) == 0) |
| break; |
| if ((cp = sshbuf_dup_string(banner)) == NULL) |
| return SSH_ERR_ALLOC_FAIL; |
| debug("%s: %s", __func__, cp); |
| free(cp); |
| /* Accept lines before banner only on client */ |
| if (ssh->kex->server || ++n > SSH_MAX_PRE_BANNER_LINES) { |
| bad: |
| if ((r = sshbuf_put(ssh_packet_get_output(ssh), |
| mismatch, strlen(mismatch))) != 0) |
| return r; |
| return SSH_ERR_NO_PROTOCOL_VERSION; |
| } |
| } |
| if ((r = sshbuf_consume(input, j)) != 0) |
| return r; |
| |
| if ((cp = sshbuf_dup_string(banner)) == NULL) |
| return SSH_ERR_ALLOC_FAIL; |
| /* XXX remote version must be the same size as banner for sscanf */ |
| if ((remote_version = calloc(1, sshbuf_len(banner))) == NULL) |
| return SSH_ERR_ALLOC_FAIL; |
| |
| /* |
| * Check that the versions match. In future this might accept |
| * several versions and set appropriate flags to handle them. |
| */ |
| if (sscanf(cp, "SSH-%d.%d-%[^\n]\n", |
| &remote_major, &remote_minor, remote_version) != 3) |
| return SSH_ERR_INVALID_FORMAT; |
| debug("Remote protocol version %d.%d, remote software version %.100s", |
| remote_major, remote_minor, remote_version); |
| |
| ssh->compat = compat_datafellows(remote_version); |
| if (remote_major == 1 && remote_minor == 99) { |
| remote_major = 2; |
| remote_minor = 0; |
| } |
| if (remote_major != 2) |
| return SSH_ERR_PROTOCOL_MISMATCH; |
| debug("Remote version string %.100s", cp); |
| free(cp); |
| return 0; |
| } |
| |
| /* Send our own protocol version identification. */ |
| int |
| _ssh_send_banner(struct ssh *ssh, struct sshbuf *banner) |
| { |
| char *cp; |
| int r; |
| |
| if ((r = sshbuf_putf(banner, "SSH-2.0-%.100s\r\n", SSH_VERSION)) != 0) |
| return r; |
| if ((r = sshbuf_putb(ssh_packet_get_output(ssh), banner)) != 0) |
| return r; |
| /* Remove trailing \r\n */ |
| if ((r = sshbuf_consume_end(banner, 2)) != 0) |
| return r; |
| if ((cp = sshbuf_dup_string(banner)) == NULL) |
| return SSH_ERR_ALLOC_FAIL; |
| debug("Local version string %.100s", cp); |
| free(cp); |
| return 0; |
| } |
| |
| int |
| _ssh_exchange_banner(struct ssh *ssh) |
| { |
| struct kex *kex = ssh->kex; |
| int r; |
| |
| /* |
| * if _ssh_read_banner() cannot parse a full version string |
| * it will return NULL and we end up calling it again. |
| */ |
| |
| r = 0; |
| if (kex->server) { |
| if (sshbuf_len(ssh->kex->server_version) == 0) |
| r = _ssh_send_banner(ssh, ssh->kex->server_version); |
| if (r == 0 && |
| sshbuf_len(ssh->kex->server_version) != 0 && |
| sshbuf_len(ssh->kex->client_version) == 0) |
| r = _ssh_read_banner(ssh, ssh->kex->client_version); |
| } else { |
| if (sshbuf_len(ssh->kex->server_version) == 0) |
| r = _ssh_read_banner(ssh, ssh->kex->server_version); |
| if (r == 0 && |
| sshbuf_len(ssh->kex->server_version) != 0 && |
| sshbuf_len(ssh->kex->client_version) == 0) |
| r = _ssh_send_banner(ssh, ssh->kex->client_version); |
| } |
| if (r != 0) |
| return r; |
| /* start initial kex as soon as we have exchanged the banners */ |
| if (sshbuf_len(ssh->kex->server_version) != 0 && |
| sshbuf_len(ssh->kex->client_version) != 0) { |
| if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 || |
| (r = kex_send_kexinit(ssh)) != 0) |
| return r; |
| } |
| return 0; |
| } |
| |
| struct sshkey * |
| _ssh_host_public_key(int type, int nid, struct ssh *ssh) |
| { |
| struct key_entry *k; |
| |
| debug3("%s: need %d", __func__, type); |
| TAILQ_FOREACH(k, &ssh->public_keys, next) { |
| debug3("%s: check %s", __func__, sshkey_type(k->key)); |
| if (k->key->type == type && |
| (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) |
| return (k->key); |
| } |
| return (NULL); |
| } |
| |
| struct sshkey * |
| _ssh_host_private_key(int type, int nid, struct ssh *ssh) |
| { |
| struct key_entry *k; |
| |
| debug3("%s: need %d", __func__, type); |
| TAILQ_FOREACH(k, &ssh->private_keys, next) { |
| debug3("%s: check %s", __func__, sshkey_type(k->key)); |
| if (k->key->type == type && |
| (type != KEY_ECDSA || k->key->ecdsa_nid == nid)) |
| return (k->key); |
| } |
| return (NULL); |
| } |
| |
| int |
| _ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh) |
| { |
| struct key_entry *k; |
| |
| debug3("%s: need %s", __func__, sshkey_type(hostkey)); |
| TAILQ_FOREACH(k, &ssh->public_keys, next) { |
| debug3("%s: check %s", __func__, sshkey_type(k->key)); |
| if (sshkey_equal_public(hostkey, k->key)) |
| return (0); /* ok */ |
| } |
| return (-1); /* failed */ |
| } |
| |
| /* offer hostkey algorithms in kexinit depending on registered keys */ |
| int |
| _ssh_order_hostkeyalgs(struct ssh *ssh) |
| { |
| struct key_entry *k; |
| char *orig, *avail, *oavail = NULL, *alg, *replace = NULL; |
| char **proposal; |
| size_t maxlen; |
| int ktype, r; |
| |
| /* XXX we de-serialize ssh->kex->my, modify it, and change it */ |
| if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0) |
| return r; |
| orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS]; |
| if ((oavail = avail = strdup(orig)) == NULL) { |
| r = SSH_ERR_ALLOC_FAIL; |
| goto out; |
| } |
| maxlen = strlen(avail) + 1; |
| if ((replace = calloc(1, maxlen)) == NULL) { |
| r = SSH_ERR_ALLOC_FAIL; |
| goto out; |
| } |
| *replace = '\0'; |
| while ((alg = strsep(&avail, ",")) && *alg != '\0') { |
| if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC) |
| continue; |
| TAILQ_FOREACH(k, &ssh->public_keys, next) { |
| if (k->key->type == ktype || |
| (sshkey_is_cert(k->key) && k->key->type == |
| sshkey_type_plain(ktype))) { |
| if (*replace != '\0') |
| strlcat(replace, ",", maxlen); |
| strlcat(replace, alg, maxlen); |
| break; |
| } |
| } |
| } |
| if (*replace != '\0') { |
| debug2("%s: orig/%d %s", __func__, ssh->kex->server, orig); |
| debug2("%s: replace/%d %s", __func__, ssh->kex->server, replace); |
| free(orig); |
| proposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = replace; |
| replace = NULL; /* owned by proposal */ |
| r = kex_prop2buf(ssh->kex->my, proposal); |
| } |
| out: |
| free(oavail); |
| free(replace); |
| kex_prop_free(proposal); |
| return r; |
| } |
| |
| int |
| _ssh_host_key_sign(struct ssh *ssh, struct sshkey *privkey, |
| struct sshkey *pubkey, u_char **signature, size_t *slen, |
| const u_char *data, size_t dlen, const char *alg) |
| { |
| return sshkey_sign(privkey, signature, slen, data, dlen, |
| alg, ssh->compat); |
| } |