| /* $OpenBSD: ssh-keysign.c,v 1.56 2018/11/23 05:08:07 djm 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> |
| #include "openbsd-compat/openssl-compat.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" |
| |
| 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; |
| |
| 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, NULL); |
| 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"); |
| |
| 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); |
| } |