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- /* $OpenBSD: ssh_api.c,v 1.21 2020/08/27 01:06:18 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 <sys/types.h>
- #include <stdio.h>
- #include <stdlib.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 *,
- const u_char *, u_int, const char *, const char *, const char *, u_int);
- #ifdef WITH_OPENSSL
- DH *mm_choose_dh(int, int, int);
- #endif
- int
- mm_sshkey_sign(struct sshkey *key, u_char **sigp, u_int *lenp,
- const u_char *data, u_int datalen, const char *alg,
- const char *sk_provider, const char *sk_pin, u_int compat)
- {
- return (-1);
- }
- #ifdef WITH_OPENSSL
- DH *
- mm_choose_dh(int min, int nbits, int max)
- {
- return (NULL);
- }
- #endif
- /* 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_gen_server;
- ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_server;
- ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_server;
- ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_server;
- ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_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_gen_server;
- # endif
- #endif /* WITH_OPENSSL */
- ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_server;
- ssh->kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_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_gen_client;
- ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_client;
- ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_client;
- ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_client;
- ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_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_gen_client;
- # endif
- #endif /* WITH_OPENSSL */
- ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_client;
- ssh->kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_client;
- ssh->kex->verify_host_key =&_ssh_verify_host_key;
- }
- *sshp = ssh;
- return 0;
- }
- void
- ssh_free(struct ssh *ssh)
- {
- struct key_entry *k;
- if (ssh == NULL)
- return;
- /*
- * 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);
- }
- ssh_packet_close(ssh);
- 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 = NULL, *remote_version = NULL;
- int r = 0, 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;
- debug("%s: %.*s", __func__, (int)sshbuf_len(banner),
- sshbuf_ptr(banner));
- /* 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;
- /* XXX remote version must be the same size as banner for sscanf */
- if ((cp = sshbuf_dup_string(banner)) == NULL ||
- (remote_version = calloc(1, sshbuf_len(banner))) == NULL) {
- r = SSH_ERR_ALLOC_FAIL;
- goto out;
- }
- /*
- * 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) {
- r = SSH_ERR_INVALID_FORMAT;
- goto out;
- }
- debug("Remote protocol version %d.%d, remote software version %.100s",
- remote_major, remote_minor, remote_version);
- compat_banner(ssh, remote_version);
- if (remote_major == 1 && remote_minor == 99) {
- remote_major = 2;
- remote_minor = 0;
- }
- if (remote_major != 2)
- r = SSH_ERR_PROTOCOL_MISMATCH;
- debug("Remote version string %.100s", cp);
- out:
- free(cp);
- free(remote_version);
- return r;
- }
- /* 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_RELEASE)) != 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, NULL, NULL, ssh->compat);
- }
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