/* $NetBSD: ssh_api.c,v 1.8.2.1 2023/12/25 12:31:09 martin Exp $ */ /* $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" __RCSID("$NetBSD: ssh_api.c,v 1.8.2.1 2023/12/25 12:31:09 martin Exp $"); #include #include #include #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 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) { const char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT }; struct ssh *ssh; const char **proposal; static int called; int r; if (!called) { #ifdef WITH_OPENSSL OpenSSL_add_all_algorithms(); #endif 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 ? __UNCONST(kex_params->proposal) : myproposal; if ((r = kex_ready(ssh, __UNCONST(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; ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_server; #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; ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_client; #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); }