Annotation of src/usr.bin/ssh/ssh-keysign.c, Revision 1.68
1.68 ! djm 1: /* $OpenBSD: ssh-keysign.c,v 1.67 2021/07/05 01:16:46 dtucker Exp $ */
1.1 markus 2: /*
3: * Copyright (c) 2002 Markus Friedl. All rights reserved.
4: *
5: * Redistribution and use in source and binary forms, with or without
6: * modification, are permitted provided that the following conditions
7: * are met:
8: * 1. Redistributions of source code must retain the above copyright
9: * notice, this list of conditions and the following disclaimer.
10: * 2. Redistributions in binary form must reproduce the above copyright
11: * notice, this list of conditions and the following disclaimer in the
12: * documentation and/or other materials provided with the distribution.
13: *
14: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24: */
1.20 stevesk 25:
1.24 stevesk 26: #include <sys/types.h>
1.1 markus 27:
1.60 djm 28: #ifdef WITH_OPENSSL
1.1 markus 29: #include <openssl/evp.h>
1.60 djm 30: #endif
1.24 stevesk 31:
1.25 stevesk 32: #include <fcntl.h>
1.24 stevesk 33: #include <paths.h>
34: #include <pwd.h>
1.67 dtucker 35: #include <stdarg.h>
36: #include <stdio.h>
1.28 stevesk 37: #include <stdlib.h>
1.27 stevesk 38: #include <string.h>
1.26 stevesk 39: #include <unistd.h>
1.50 djm 40: #include <errno.h>
1.1 markus 41:
1.29 deraadt 42: #include "xmalloc.h"
1.1 markus 43: #include "log.h"
1.46 djm 44: #include "sshkey.h"
1.7 markus 45: #include "ssh.h"
1.1 markus 46: #include "ssh2.h"
47: #include "misc.h"
1.46 djm 48: #include "sshbuf.h"
1.1 markus 49: #include "authfile.h"
50: #include "msg.h"
1.2 markus 51: #include "canohost.h"
1.1 markus 52: #include "pathnames.h"
1.7 markus 53: #include "readconf.h"
1.17 dtucker 54: #include "uidswap.h"
1.45 djm 55: #include "ssherr.h"
1.7 markus 56:
1.50 djm 57: extern char *__progname;
58:
1.1 markus 59: static int
1.46 djm 60: valid_request(struct passwd *pw, char *host, struct sshkey **ret,
61: u_char *data, size_t datalen)
1.1 markus 62: {
1.46 djm 63: struct sshbuf *b;
64: struct sshkey *key = NULL;
65: u_char type, *pkblob;
66: char *p;
67: size_t blen, len;
68: char *pkalg, *luser;
69: int r, pktype, fail;
1.1 markus 70:
1.45 djm 71: if (ret != NULL)
72: *ret = NULL;
1.1 markus 73: fail = 0;
74:
1.46 djm 75: if ((b = sshbuf_from(data, datalen)) == NULL)
1.65 djm 76: fatal_f("sshbuf_from failed");
1.4 deraadt 77:
1.68 ! djm 78: /* session id */
1.46 djm 79: if ((r = sshbuf_get_string(b, NULL, &len)) != 0)
1.65 djm 80: fatal_fr(r, "parse session ID");
1.68 ! djm 81: if (len != 20 && /* SHA1 */
! 82: len != 32 && /* SHA256 */
! 83: len != 48 && /* SHA384 */
! 84: len != 64) /* SHA512 */
1.3 markus 85: fail++;
86:
1.46 djm 87: if ((r = sshbuf_get_u8(b, &type)) != 0)
1.65 djm 88: fatal_fr(r, "parse type");
1.46 djm 89: if (type != SSH2_MSG_USERAUTH_REQUEST)
1.1 markus 90: fail++;
91:
92: /* server user */
1.46 djm 93: if ((r = sshbuf_skip_string(b)) != 0)
1.65 djm 94: fatal_fr(r, "parse user");
1.1 markus 95:
96: /* service */
1.46 djm 97: if ((r = sshbuf_get_cstring(b, &p, NULL)) != 0)
1.65 djm 98: fatal_fr(r, "parse service");
1.1 markus 99: if (strcmp("ssh-connection", p) != 0)
100: fail++;
1.37 djm 101: free(p);
1.1 markus 102:
103: /* method */
1.46 djm 104: if ((r = sshbuf_get_cstring(b, &p, NULL)) != 0)
1.65 djm 105: fatal_fr(r, "parse method");
1.1 markus 106: if (strcmp("hostbased", p) != 0)
107: fail++;
1.37 djm 108: free(p);
1.1 markus 109:
110: /* pubkey */
1.46 djm 111: if ((r = sshbuf_get_cstring(b, &pkalg, NULL)) != 0 ||
112: (r = sshbuf_get_string(b, &pkblob, &blen)) != 0)
1.65 djm 113: fatal_fr(r, "parse pk");
1.1 markus 114:
1.46 djm 115: pktype = sshkey_type_from_name(pkalg);
1.1 markus 116: if (pktype == KEY_UNSPEC)
117: fail++;
1.46 djm 118: else if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) {
1.65 djm 119: error_fr(r, "decode key");
1.1 markus 120: fail++;
1.46 djm 121: } else if (key->type != pktype)
1.1 markus 122: fail++;
1.37 djm 123: free(pkalg);
124: free(pkblob);
1.1 markus 125:
1.2 markus 126: /* client host name, handle trailing dot */
1.46 djm 127: if ((r = sshbuf_get_cstring(b, &p, &len)) != 0)
1.65 djm 128: fatal_fr(r, "parse hostname");
129: debug2_f("check expect chost %s got %s", host, p);
1.2 markus 130: if (strlen(host) != len - 1)
131: fail++;
132: else if (p[len - 1] != '.')
1.4 deraadt 133: fail++;
1.2 markus 134: else if (strncasecmp(host, p, len - 1) != 0)
1.4 deraadt 135: fail++;
1.37 djm 136: free(p);
1.1 markus 137:
138: /* local user */
1.46 djm 139: if ((r = sshbuf_get_cstring(b, &luser, NULL)) != 0)
1.65 djm 140: fatal_fr(r, "parse luser");
1.2 markus 141:
1.46 djm 142: if (strcmp(pw->pw_name, luser) != 0)
1.1 markus 143: fail++;
1.46 djm 144: free(luser);
1.1 markus 145:
146: /* end of message */
1.46 djm 147: if (sshbuf_len(b) != 0)
1.1 markus 148: fail++;
1.46 djm 149: sshbuf_free(b);
1.1 markus 150:
1.65 djm 151: debug3_f("fail %d", fail);
1.1 markus 152:
1.53 dtucker 153: if (fail)
1.46 djm 154: sshkey_free(key);
1.48 markus 155: else if (ret != NULL)
1.1 markus 156: *ret = key;
157:
158: return (fail ? -1 : 0);
159: }
160:
161: int
162: main(int argc, char **argv)
163: {
1.46 djm 164: struct sshbuf *b;
1.7 markus 165: Options options;
1.54 markus 166: #define NUM_KEYTYPES 5
1.46 djm 167: struct sshkey *keys[NUM_KEYTYPES], *key = NULL;
1.1 markus 168: struct passwd *pw;
1.45 djm 169: int r, key_fd[NUM_KEYTYPES], i, found, version = 2, fd;
1.46 djm 170: u_char *signature, *data, rver;
1.40 djm 171: char *host, *fp;
1.46 djm 172: size_t slen, dlen;
1.19 djm 173:
1.50 djm 174: if (pledge("stdio rpath getpw dns id", NULL) != 0)
175: fatal("%s: pledge: %s", __progname, strerror(errno));
176:
1.19 djm 177: /* Ensure that stdin and stdout are connected */
178: if ((fd = open(_PATH_DEVNULL, O_RDWR)) < 2)
179: exit(1);
180: /* Leave /dev/null fd iff it is attached to stderr */
181: if (fd > 2)
182: close(fd);
1.1 markus 183:
1.36 djm 184: i = 0;
1.49 djm 185: /* XXX This really needs to read sshd_config for the paths */
1.36 djm 186: key_fd[i++] = open(_PATH_HOST_DSA_KEY_FILE, O_RDONLY);
187: key_fd[i++] = open(_PATH_HOST_ECDSA_KEY_FILE, O_RDONLY);
1.39 markus 188: key_fd[i++] = open(_PATH_HOST_ED25519_KEY_FILE, O_RDONLY);
1.54 markus 189: key_fd[i++] = open(_PATH_HOST_XMSS_KEY_FILE, O_RDONLY);
1.36 djm 190: key_fd[i++] = open(_PATH_HOST_RSA_KEY_FILE, O_RDONLY);
1.1 markus 191:
1.55 dtucker 192: if ((pw = getpwuid(getuid())) == NULL)
1.17 dtucker 193: fatal("getpwuid failed");
194: pw = pwcopy(pw);
195:
196: permanently_set_uid(pw);
1.1 markus 197:
198: #ifdef DEBUG_SSH_KEYSIGN
199: log_init("ssh-keysign", SYSLOG_LEVEL_DEBUG3, SYSLOG_FACILITY_AUTH, 0);
1.4 deraadt 200: #endif
1.7 markus 201:
202: /* verify that ssh-keysign is enabled by the admin */
203: initialize_options(&options);
1.56 djm 204: (void)read_config_file(_PATH_HOST_CONFIG_FILE, pw, "", "",
205: &options, 0, NULL);
1.66 djm 206: (void)fill_default_options(&options);
1.8 markus 207: if (options.enable_ssh_keysign != 1)
208: fatal("ssh-keysign not enabled in %s",
1.7 markus 209: _PATH_HOST_CONFIG_FILE);
1.1 markus 210:
1.36 djm 211: for (i = found = 0; i < NUM_KEYTYPES; i++) {
212: if (key_fd[i] != -1)
213: found = 1;
214: }
215: if (found == 0)
1.1 markus 216: fatal("could not open any host key");
217:
1.60 djm 218: #ifdef WITH_OPENSSL
1.35 djm 219: OpenSSL_add_all_algorithms();
1.60 djm 220: #endif
1.1 markus 221: found = 0;
1.36 djm 222: for (i = 0; i < NUM_KEYTYPES; i++) {
1.1 markus 223: keys[i] = NULL;
224: if (key_fd[i] == -1)
225: continue;
1.45 djm 226: r = sshkey_load_private_type_fd(key_fd[i], KEY_UNSPEC,
227: NULL, &key, NULL);
1.1 markus 228: close(key_fd[i]);
1.45 djm 229: if (r != 0)
1.65 djm 230: debug_r(r, "parse key %d", i);
1.45 djm 231: else if (key != NULL) {
232: keys[i] = key;
1.1 markus 233: found = 1;
1.45 djm 234: }
1.1 markus 235: }
236: if (!found)
237: fatal("no hostkey found");
238:
1.50 djm 239: if (pledge("stdio dns", NULL) != 0)
240: fatal("%s: pledge: %s", __progname, strerror(errno));
241:
1.46 djm 242: if ((b = sshbuf_new()) == NULL)
1.50 djm 243: fatal("%s: sshbuf_new failed", __progname);
1.46 djm 244: if (ssh_msg_recv(STDIN_FILENO, b) < 0)
1.65 djm 245: fatal("%s: ssh_msg_recv failed", __progname);
1.46 djm 246: if ((r = sshbuf_get_u8(b, &rver)) != 0)
1.65 djm 247: fatal_r(r, "%s: buffer error", __progname);
1.46 djm 248: if (rver != version)
1.65 djm 249: fatal("%s: bad version: received %d, expected %d",
250: __progname, rver, version);
1.46 djm 251: if ((r = sshbuf_get_u32(b, (u_int *)&fd)) != 0)
1.65 djm 252: fatal_r(r, "%s: buffer error", __progname);
1.46 djm 253: if (fd < 0 || fd == STDIN_FILENO || fd == STDOUT_FILENO)
1.65 djm 254: fatal("%s: bad fd = %d", __progname, fd);
1.2 markus 255: if ((host = get_local_name(fd)) == NULL)
1.65 djm 256: fatal("%s: cannot get local name for fd", __progname);
1.4 deraadt 257:
1.46 djm 258: if ((r = sshbuf_get_string(b, &data, &dlen)) != 0)
1.65 djm 259: fatal_r(r, "%s: buffer error", __progname);
1.2 markus 260: if (valid_request(pw, host, &key, data, dlen) < 0)
1.65 djm 261: fatal("%s: not a valid request", __progname);
1.37 djm 262: free(host);
1.1 markus 263:
264: found = 0;
1.36 djm 265: for (i = 0; i < NUM_KEYTYPES; i++) {
1.1 markus 266: if (keys[i] != NULL &&
1.46 djm 267: sshkey_equal_public(key, keys[i])) {
1.1 markus 268: found = 1;
269: break;
270: }
271: }
1.40 djm 272: if (!found) {
1.47 djm 273: if ((fp = sshkey_fingerprint(key, options.fingerprint_hash,
274: SSH_FP_DEFAULT)) == NULL)
1.50 djm 275: fatal("%s: sshkey_fingerprint failed", __progname);
1.65 djm 276: fatal("%s: no matching hostkey found for key %s %s", __progname,
1.46 djm 277: sshkey_type(key), fp ? fp : "");
1.40 djm 278: }
1.1 markus 279:
1.62 djm 280: if ((r = sshkey_sign(keys[i], &signature, &slen, data, dlen,
1.64 djm 281: NULL, NULL, NULL, 0)) != 0)
1.65 djm 282: fatal_r(r, "%s: sshkey_sign failed", __progname);
1.37 djm 283: free(data);
1.4 deraadt 284:
1.1 markus 285: /* send reply */
1.46 djm 286: sshbuf_reset(b);
287: if ((r = sshbuf_put_string(b, signature, slen)) != 0)
1.65 djm 288: fatal_r(r, "%s: buffer error", __progname);
1.46 djm 289: if (ssh_msg_send(STDOUT_FILENO, version, b) == -1)
1.65 djm 290: fatal("%s: ssh_msg_send failed", __progname);
1.1 markus 291:
292: return (0);
293: }
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