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-rw-r--r--ssh_api.c570
1 files changed, 570 insertions, 0 deletions
diff --git a/ssh_api.c b/ssh_api.c
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index 0000000..d3c6617
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+++ b/ssh_api.c
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+/* $OpenBSD: ssh_api.c,v 1.27 2021/04/03 06:18:41 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_f("%.*s", (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_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_f("need %d", type);
+ TAILQ_FOREACH(k, &ssh->public_keys, next) {
+ debug3_f("check %s", 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_f("need %d", type);
+ TAILQ_FOREACH(k, &ssh->private_keys, next) {
+ debug3_f("check %s", 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_f("need %s", sshkey_type(hostkey));
+ TAILQ_FOREACH(k, &ssh->public_keys, next) {
+ debug3_f("check %s", 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_f("orig/%d %s", ssh->kex->server, orig);
+ debug2_f("replace/%d %s", 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);
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-10 07:38:14 +0000