/* $OpenBSD: ssh_api.c,v 1.4 2015/02/16 22:13:32 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 "ssh1.h" /* For SSH_MSG_NONE */
#include "ssh_api.h"
#include "compat.h"
#include "log.h"
#include "authfile.h"
#include "sshkey.h"
#include "misc.h"
#include "ssh1.h"
#include "ssh2.h"
#include "version.h"
#include "myproposal.h"
#include "ssherr.h"
#include "sshbuf.h"
#include <string.h>
int _ssh_exchange_banner(struct ssh *);
int _ssh_send_banner(struct ssh *, char **);
int _ssh_read_banner(struct ssh *, char **);
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 sshkey *, struct sshkey *, u_char **,
size_t *, const u_char *, size_t, u_int);
/*
* 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, 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, 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) {
#ifdef WITH_OPENSSL
OpenSSL_add_all_algorithms();
#endif /* WITH_OPENSSL */
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_new(ssh, proposal, &ssh->kex)) != 0) {
ssh_free(ssh);
return r;
}
ssh->kex->server = is_server;
if (is_server) {
#ifdef WITH_OPENSSL
ssh->kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server;
ssh->kex->kex[KEX_DH_GRP14_SHA1] = kexdh_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] = kexecdh_server;
# endif
#endif /* WITH_OPENSSL */
ssh->kex->kex[KEX_C25519_SHA256] = kexc25519_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] = kexdh_client;
ssh->kex->kex[KEX_DH_GRP14_SHA1] = kexdh_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] = kexecdh_client;
# endif
#endif /* WITH_OPENSSL */
ssh->kex->kex[KEX_C25519_SHA256] = kexc25519_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 (ssh->kex->client_version_string == NULL ||
ssh->kex->server_version_string == NULL)
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, char **bannerp)
{
struct sshbuf *input;
const char *s;
char buf[256], remote_version[256]; /* must be same size! */
const char *mismatch = "Protocol mismatch.\r\n";
int r, remote_major, remote_minor;
size_t i, n, j, len;
*bannerp = NULL;
input = ssh_packet_get_input(ssh);
len = sshbuf_len(input);
s = (const char *)sshbuf_ptr(input);
for (j = n = 0;;) {
for (i = 0; i < sizeof(buf) - 1; i++) {
if (j >= len)
return (0);
buf[i] = s[j++];
if (buf[i] == '\r') {
buf[i] = '\n';
buf[i + 1] = 0;
continue; /**XXX wait for \n */
}
if (buf[i] == '\n') {
buf[i + 1] = 0;
break;
}
}
buf[sizeof(buf) - 1] = 0;
if (strncmp(buf, "SSH-", 4) == 0)
break;
debug("ssh_exchange_identification: %s", buf);
if (ssh->kex->server || ++n > 65536) {
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;
/*
* Check that the versions match. In future this might accept
* several versions and set appropriate flags to handle them.
*/
if (sscanf(buf, "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;
enable_compat20();
chop(buf);
debug("Remote version string %.100s", buf);
if ((*bannerp = strdup(buf)) == NULL)
return SSH_ERR_ALLOC_FAIL;
return 0;
}
/* Send our own protocol version identification. */
int
_ssh_send_banner(struct ssh *ssh, char **bannerp)
{
char buf[256];
int r;
snprintf(buf, sizeof buf, "SSH-2.0-%.100s\r\n", SSH_VERSION);
if ((r = sshbuf_put(ssh_packet_get_output(ssh), buf, strlen(buf))) != 0)
return r;
chop(buf);
debug("Local version string %.100s", buf);
if ((*bannerp = strdup(buf)) == NULL)
return SSH_ERR_ALLOC_FAIL;
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 (kex->server_version_string == NULL)
r = _ssh_send_banner(ssh, &kex->server_version_string);
if (r == 0 &&
kex->server_version_string != NULL &&
kex->client_version_string == NULL)
r = _ssh_read_banner(ssh, &kex->client_version_string);
} else {
if (kex->server_version_string == NULL)
r = _ssh_read_banner(ssh, &kex->server_version_string);
if (r == 0 &&
kex->server_version_string != NULL &&
kex->client_version_string == NULL)
r = _ssh_send_banner(ssh, &kex->client_version_string);
}
if (r != 0)
return r;
/* start initial kex as soon as we have exchanged the banners */
if (kex->server_version_string != NULL &&
kex->client_version_string != NULL) {
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 sshkey *privkey, struct sshkey *pubkey,
u_char **signature, size_t *slen,
const u_char *data, size_t dlen, u_int compat)
{
return sshkey_sign(privkey, signature, slen, data, dlen, compat);
}