diff options
Diffstat (limited to 'ssh-keysign.c')
| -rw-r--r-- | ssh-keysign.c | 303 |
1 files changed, 303 insertions, 0 deletions
diff --git a/ssh-keysign.c b/ssh-keysign.c new file mode 100644 index 0000000..744ecb4 --- /dev/null +++ b/ssh-keysign.c @@ -0,0 +1,303 @@ +/* $OpenBSD: ssh-keysign.c,v 1.55 2018/07/27 05:34:42 dtucker Exp $ */ +/* + * Copyright (c) 2002 Markus Friedl. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR + * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. + * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT + * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF + * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +#include "includes.h" + +#include <fcntl.h> +#ifdef HAVE_PATHS_H +#include <paths.h> +#endif +#include <pwd.h> +#include <stdarg.h> +#include <stdlib.h> +#include <string.h> +#include <unistd.h> +#include <errno.h> + +#ifdef WITH_OPENSSL +#include <openssl/evp.h> +#include <openssl/rand.h> +#include <openssl/rsa.h> +#endif + +#include "xmalloc.h" +#include "log.h" +#include "sshkey.h" +#include "ssh.h" +#include "ssh2.h" +#include "misc.h" +#include "sshbuf.h" +#include "authfile.h" +#include "msg.h" +#include "canohost.h" +#include "pathnames.h" +#include "readconf.h" +#include "uidswap.h" +#include "sshkey.h" +#include "ssherr.h" + +struct ssh *active_state = NULL; /* XXX needed for linking */ + +extern char *__progname; + +static int +valid_request(struct passwd *pw, char *host, struct sshkey **ret, + u_char *data, size_t datalen) +{ + struct sshbuf *b; + struct sshkey *key = NULL; + u_char type, *pkblob; + char *p; + size_t blen, len; + char *pkalg, *luser; + int r, pktype, fail; + + if (ret != NULL) + *ret = NULL; + fail = 0; + + if ((b = sshbuf_from(data, datalen)) == NULL) + fatal("%s: sshbuf_from failed", __func__); + + /* session id, currently limited to SHA1 (20 bytes) or SHA256 (32) */ + if ((r = sshbuf_get_string(b, NULL, &len)) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + if (len != 20 && len != 32) + fail++; + + if ((r = sshbuf_get_u8(b, &type)) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + if (type != SSH2_MSG_USERAUTH_REQUEST) + fail++; + + /* server user */ + if ((r = sshbuf_skip_string(b)) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + + /* service */ + if ((r = sshbuf_get_cstring(b, &p, NULL)) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + if (strcmp("ssh-connection", p) != 0) + fail++; + free(p); + + /* method */ + if ((r = sshbuf_get_cstring(b, &p, NULL)) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + if (strcmp("hostbased", p) != 0) + fail++; + free(p); + + /* pubkey */ + if ((r = sshbuf_get_cstring(b, &pkalg, NULL)) != 0 || + (r = sshbuf_get_string(b, &pkblob, &blen)) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + + pktype = sshkey_type_from_name(pkalg); + if (pktype == KEY_UNSPEC) + fail++; + else if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) { + error("%s: bad key blob: %s", __func__, ssh_err(r)); + fail++; + } else if (key->type != pktype) + fail++; + free(pkalg); + free(pkblob); + + /* client host name, handle trailing dot */ + if ((r = sshbuf_get_cstring(b, &p, &len)) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + debug2("%s: check expect chost %s got %s", __func__, host, p); + if (strlen(host) != len - 1) + fail++; + else if (p[len - 1] != '.') + fail++; + else if (strncasecmp(host, p, len - 1) != 0) + fail++; + free(p); + + /* local user */ + if ((r = sshbuf_get_cstring(b, &luser, NULL)) != 0) + fatal("%s: buffer error: %s", __func__, ssh_err(r)); + + if (strcmp(pw->pw_name, luser) != 0) + fail++; + free(luser); + + /* end of message */ + if (sshbuf_len(b) != 0) + fail++; + sshbuf_free(b); + + debug3("%s: fail %d", __func__, fail); + + if (fail) + sshkey_free(key); + else if (ret != NULL) + *ret = key; + + return (fail ? -1 : 0); +} + +int +main(int argc, char **argv) +{ + struct sshbuf *b; + Options options; +#define NUM_KEYTYPES 5 + struct sshkey *keys[NUM_KEYTYPES], *key = NULL; + struct passwd *pw; + int r, key_fd[NUM_KEYTYPES], i, found, version = 2, fd; + u_char *signature, *data, rver; + char *host, *fp; + size_t slen, dlen; +#ifdef WITH_OPENSSL + u_int32_t rnd[256]; +#endif + + ssh_malloc_init(); /* must be called before any mallocs */ + if (pledge("stdio rpath getpw dns id", NULL) != 0) + fatal("%s: pledge: %s", __progname, strerror(errno)); + + /* Ensure that stdin and stdout are connected */ + if ((fd = open(_PATH_DEVNULL, O_RDWR)) < 2) + exit(1); + /* Leave /dev/null fd iff it is attached to stderr */ + if (fd > 2) + close(fd); + + i = 0; + /* XXX This really needs to read sshd_config for the paths */ + key_fd[i++] = open(_PATH_HOST_DSA_KEY_FILE, O_RDONLY); + key_fd[i++] = open(_PATH_HOST_ECDSA_KEY_FILE, O_RDONLY); + key_fd[i++] = open(_PATH_HOST_ED25519_KEY_FILE, O_RDONLY); + key_fd[i++] = open(_PATH_HOST_XMSS_KEY_FILE, O_RDONLY); + key_fd[i++] = open(_PATH_HOST_RSA_KEY_FILE, O_RDONLY); + + if ((pw = getpwuid(getuid())) == NULL) + fatal("getpwuid failed"); + pw = pwcopy(pw); + + permanently_set_uid(pw); + + seed_rng(); + +#ifdef DEBUG_SSH_KEYSIGN + log_init("ssh-keysign", SYSLOG_LEVEL_DEBUG3, SYSLOG_FACILITY_AUTH, 0); +#endif + + /* verify that ssh-keysign is enabled by the admin */ + initialize_options(&options); + (void)read_config_file(_PATH_HOST_CONFIG_FILE, pw, "", "", &options, 0); + fill_default_options(&options); + if (options.enable_ssh_keysign != 1) + fatal("ssh-keysign not enabled in %s", + _PATH_HOST_CONFIG_FILE); + + for (i = found = 0; i < NUM_KEYTYPES; i++) { + if (key_fd[i] != -1) + found = 1; + } + if (found == 0) + fatal("could not open any host key"); + +#ifdef WITH_OPENSSL + OpenSSL_add_all_algorithms(); + arc4random_buf(rnd, sizeof(rnd)); + RAND_seed(rnd, sizeof(rnd)); +#endif + + found = 0; + for (i = 0; i < NUM_KEYTYPES; i++) { + keys[i] = NULL; + if (key_fd[i] == -1) + continue; + r = sshkey_load_private_type_fd(key_fd[i], KEY_UNSPEC, + NULL, &key, NULL); + close(key_fd[i]); + if (r != 0) + debug("parse key %d: %s", i, ssh_err(r)); + else if (key != NULL) { + keys[i] = key; + found = 1; + } + } + if (!found) + fatal("no hostkey found"); + + if (pledge("stdio dns", NULL) != 0) + fatal("%s: pledge: %s", __progname, strerror(errno)); + + if ((b = sshbuf_new()) == NULL) + fatal("%s: sshbuf_new failed", __progname); + if (ssh_msg_recv(STDIN_FILENO, b) < 0) + fatal("ssh_msg_recv failed"); + if ((r = sshbuf_get_u8(b, &rver)) != 0) + fatal("%s: buffer error: %s", __progname, ssh_err(r)); + if (rver != version) + fatal("bad version: received %d, expected %d", rver, version); + if ((r = sshbuf_get_u32(b, (u_int *)&fd)) != 0) + fatal("%s: buffer error: %s", __progname, ssh_err(r)); + if (fd < 0 || fd == STDIN_FILENO || fd == STDOUT_FILENO) + fatal("bad fd"); + if ((host = get_local_name(fd)) == NULL) + fatal("cannot get local name for fd"); + + if ((r = sshbuf_get_string(b, &data, &dlen)) != 0) + fatal("%s: buffer error: %s", __progname, ssh_err(r)); + if (valid_request(pw, host, &key, data, dlen) < 0) + fatal("not a valid request"); + free(host); + + found = 0; + for (i = 0; i < NUM_KEYTYPES; i++) { + if (keys[i] != NULL && + sshkey_equal_public(key, keys[i])) { + found = 1; + break; + } + } + if (!found) { + if ((fp = sshkey_fingerprint(key, options.fingerprint_hash, + SSH_FP_DEFAULT)) == NULL) + fatal("%s: sshkey_fingerprint failed", __progname); + fatal("no matching hostkey found for key %s %s", + sshkey_type(key), fp ? fp : ""); + } + + if ((r = sshkey_sign(keys[i], &signature, &slen, data, dlen, NULL, 0)) + != 0) + fatal("sshkey_sign failed: %s", ssh_err(r)); + free(data); + + /* send reply */ + sshbuf_reset(b); + if ((r = sshbuf_put_string(b, signature, slen)) != 0) + fatal("%s: buffer error: %s", __progname, ssh_err(r)); + if (ssh_msg_send(STDOUT_FILENO, version, b) == -1) + fatal("ssh_msg_send failed"); + + return (0); +} |