Annotation of src/usr.bin/ssh/ssh-keysign.c, Revision 1.53
1.53 ! dtucker 1: /* $OpenBSD: ssh-keysign.c,v 1.52 2016/02/15 09:47:49 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:
28: #include <openssl/evp.h>
1.6 markus 29: #include <openssl/rsa.h>
1.24 stevesk 30:
1.25 stevesk 31: #include <fcntl.h>
1.24 stevesk 32: #include <paths.h>
33: #include <pwd.h>
1.28 stevesk 34: #include <stdlib.h>
1.27 stevesk 35: #include <string.h>
1.26 stevesk 36: #include <unistd.h>
1.50 djm 37: #include <errno.h>
1.1 markus 38:
1.29 deraadt 39: #include "xmalloc.h"
1.1 markus 40: #include "log.h"
1.46 djm 41: #include "sshkey.h"
1.7 markus 42: #include "ssh.h"
1.1 markus 43: #include "ssh2.h"
44: #include "misc.h"
1.46 djm 45: #include "sshbuf.h"
1.1 markus 46: #include "authfile.h"
47: #include "msg.h"
1.2 markus 48: #include "canohost.h"
1.1 markus 49: #include "pathnames.h"
1.7 markus 50: #include "readconf.h"
1.17 dtucker 51: #include "uidswap.h"
1.45 djm 52: #include "sshkey.h"
53: #include "ssherr.h"
1.7 markus 54:
1.50 djm 55: extern char *__progname;
56:
1.12 djm 57: /* XXX readconf.c needs these */
58: uid_t original_real_uid;
1.1 markus 59:
60: static int
1.46 djm 61: valid_request(struct passwd *pw, char *host, struct sshkey **ret,
62: u_char *data, size_t datalen)
1.1 markus 63: {
1.46 djm 64: struct sshbuf *b;
65: struct sshkey *key = NULL;
66: u_char type, *pkblob;
67: char *p;
68: size_t blen, len;
69: char *pkalg, *luser;
70: int r, pktype, fail;
1.1 markus 71:
1.45 djm 72: if (ret != NULL)
73: *ret = NULL;
1.1 markus 74: fail = 0;
75:
1.46 djm 76: if ((b = sshbuf_from(data, datalen)) == NULL)
77: fatal("%s: sshbuf_from failed", __func__);
1.4 deraadt 78:
1.23 dtucker 79: /* session id, currently limited to SHA1 (20 bytes) or SHA256 (32) */
1.46 djm 80: if ((r = sshbuf_get_string(b, NULL, &len)) != 0)
81: fatal("%s: buffer error: %s", __func__, ssh_err(r));
1.23 dtucker 82: if (len != 20 && len != 32)
1.3 markus 83: fail++;
84:
1.46 djm 85: if ((r = sshbuf_get_u8(b, &type)) != 0)
86: fatal("%s: buffer error: %s", __func__, ssh_err(r));
87: if (type != SSH2_MSG_USERAUTH_REQUEST)
1.1 markus 88: fail++;
89:
90: /* server user */
1.46 djm 91: if ((r = sshbuf_skip_string(b)) != 0)
92: fatal("%s: buffer error: %s", __func__, ssh_err(r));
1.1 markus 93:
94: /* service */
1.46 djm 95: if ((r = sshbuf_get_cstring(b, &p, NULL)) != 0)
96: fatal("%s: buffer error: %s", __func__, ssh_err(r));
1.1 markus 97: if (strcmp("ssh-connection", p) != 0)
98: fail++;
1.37 djm 99: free(p);
1.1 markus 100:
101: /* method */
1.46 djm 102: if ((r = sshbuf_get_cstring(b, &p, NULL)) != 0)
103: fatal("%s: buffer error: %s", __func__, ssh_err(r));
1.1 markus 104: if (strcmp("hostbased", p) != 0)
105: fail++;
1.37 djm 106: free(p);
1.1 markus 107:
108: /* pubkey */
1.46 djm 109: if ((r = sshbuf_get_cstring(b, &pkalg, NULL)) != 0 ||
110: (r = sshbuf_get_string(b, &pkblob, &blen)) != 0)
111: fatal("%s: buffer error: %s", __func__, ssh_err(r));
1.1 markus 112:
1.46 djm 113: pktype = sshkey_type_from_name(pkalg);
1.1 markus 114: if (pktype == KEY_UNSPEC)
115: fail++;
1.46 djm 116: else if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) {
117: error("%s: bad key blob: %s", __func__, ssh_err(r));
1.1 markus 118: fail++;
1.46 djm 119: } else if (key->type != pktype)
1.1 markus 120: fail++;
1.37 djm 121: free(pkalg);
122: free(pkblob);
1.1 markus 123:
1.2 markus 124: /* client host name, handle trailing dot */
1.46 djm 125: if ((r = sshbuf_get_cstring(b, &p, &len)) != 0)
126: fatal("%s: buffer error: %s", __func__, ssh_err(r));
127: debug2("%s: check expect chost %s got %s", __func__, host, p);
1.2 markus 128: if (strlen(host) != len - 1)
129: fail++;
130: else if (p[len - 1] != '.')
1.4 deraadt 131: fail++;
1.2 markus 132: else if (strncasecmp(host, p, len - 1) != 0)
1.4 deraadt 133: fail++;
1.37 djm 134: free(p);
1.1 markus 135:
136: /* local user */
1.46 djm 137: if ((r = sshbuf_get_cstring(b, &luser, NULL)) != 0)
138: fatal("%s: buffer error: %s", __func__, ssh_err(r));
1.2 markus 139:
1.46 djm 140: if (strcmp(pw->pw_name, luser) != 0)
1.1 markus 141: fail++;
1.46 djm 142: free(luser);
1.1 markus 143:
144: /* end of message */
1.46 djm 145: if (sshbuf_len(b) != 0)
1.1 markus 146: fail++;
1.46 djm 147: sshbuf_free(b);
1.1 markus 148:
1.46 djm 149: debug3("%s: fail %d", __func__, fail);
1.1 markus 150:
1.53 ! dtucker 151: if (fail)
1.46 djm 152: sshkey_free(key);
1.48 markus 153: else if (ret != NULL)
1.1 markus 154: *ret = key;
155:
156: return (fail ? -1 : 0);
157: }
158:
159: int
160: main(int argc, char **argv)
161: {
1.46 djm 162: struct sshbuf *b;
1.7 markus 163: Options options;
1.39 markus 164: #define NUM_KEYTYPES 4
1.46 djm 165: struct sshkey *keys[NUM_KEYTYPES], *key = NULL;
1.1 markus 166: struct passwd *pw;
1.45 djm 167: int r, key_fd[NUM_KEYTYPES], i, found, version = 2, fd;
1.46 djm 168: u_char *signature, *data, rver;
1.40 djm 169: char *host, *fp;
1.46 djm 170: size_t slen, dlen;
1.19 djm 171:
1.52 dtucker 172: ssh_malloc_init(); /* must be called before any mallocs */
1.50 djm 173: if (pledge("stdio rpath getpw dns id", NULL) != 0)
174: fatal("%s: pledge: %s", __progname, strerror(errno));
175:
1.19 djm 176: /* Ensure that stdin and stdout are connected */
177: if ((fd = open(_PATH_DEVNULL, O_RDWR)) < 2)
178: exit(1);
179: /* Leave /dev/null fd iff it is attached to stderr */
180: if (fd > 2)
181: close(fd);
1.1 markus 182:
1.36 djm 183: i = 0;
1.49 djm 184: /* XXX This really needs to read sshd_config for the paths */
1.36 djm 185: key_fd[i++] = open(_PATH_HOST_DSA_KEY_FILE, O_RDONLY);
186: key_fd[i++] = open(_PATH_HOST_ECDSA_KEY_FILE, O_RDONLY);
1.39 markus 187: key_fd[i++] = open(_PATH_HOST_ED25519_KEY_FILE, O_RDONLY);
1.36 djm 188: key_fd[i++] = open(_PATH_HOST_RSA_KEY_FILE, O_RDONLY);
1.1 markus 189:
1.18 dtucker 190: original_real_uid = getuid(); /* XXX readconf.c needs this */
191: if ((pw = getpwuid(original_real_uid)) == NULL)
1.17 dtucker 192: fatal("getpwuid failed");
193: pw = pwcopy(pw);
194:
195: permanently_set_uid(pw);
1.1 markus 196:
197: #ifdef DEBUG_SSH_KEYSIGN
198: log_init("ssh-keysign", SYSLOG_LEVEL_DEBUG3, SYSLOG_FACILITY_AUTH, 0);
1.4 deraadt 199: #endif
1.7 markus 200:
201: /* verify that ssh-keysign is enabled by the admin */
202: initialize_options(&options);
1.43 djm 203: (void)read_config_file(_PATH_HOST_CONFIG_FILE, pw, "", "", &options, 0);
1.7 markus 204: fill_default_options(&options);
1.8 markus 205: if (options.enable_ssh_keysign != 1)
206: fatal("ssh-keysign not enabled in %s",
1.7 markus 207: _PATH_HOST_CONFIG_FILE);
1.1 markus 208:
1.36 djm 209: for (i = found = 0; i < NUM_KEYTYPES; i++) {
210: if (key_fd[i] != -1)
211: found = 1;
212: }
213: if (found == 0)
1.1 markus 214: fatal("could not open any host key");
215:
1.35 djm 216: OpenSSL_add_all_algorithms();
1.1 markus 217:
218: found = 0;
1.36 djm 219: for (i = 0; i < NUM_KEYTYPES; i++) {
1.1 markus 220: keys[i] = NULL;
221: if (key_fd[i] == -1)
222: continue;
1.45 djm 223: r = sshkey_load_private_type_fd(key_fd[i], KEY_UNSPEC,
224: NULL, &key, NULL);
1.1 markus 225: close(key_fd[i]);
1.45 djm 226: if (r != 0)
227: debug("parse key %d: %s", i, ssh_err(r));
228: else if (key != NULL) {
229: keys[i] = key;
1.1 markus 230: found = 1;
1.45 djm 231: }
1.1 markus 232: }
233: if (!found)
234: fatal("no hostkey found");
235:
1.50 djm 236: if (pledge("stdio dns", NULL) != 0)
237: fatal("%s: pledge: %s", __progname, strerror(errno));
238:
1.46 djm 239: if ((b = sshbuf_new()) == NULL)
1.50 djm 240: fatal("%s: sshbuf_new failed", __progname);
1.46 djm 241: if (ssh_msg_recv(STDIN_FILENO, b) < 0)
1.9 djm 242: fatal("ssh_msg_recv failed");
1.46 djm 243: if ((r = sshbuf_get_u8(b, &rver)) != 0)
1.50 djm 244: fatal("%s: buffer error: %s", __progname, ssh_err(r));
1.46 djm 245: if (rver != version)
246: fatal("bad version: received %d, expected %d", rver, version);
247: if ((r = sshbuf_get_u32(b, (u_int *)&fd)) != 0)
1.50 djm 248: fatal("%s: buffer error: %s", __progname, ssh_err(r));
1.46 djm 249: if (fd < 0 || fd == STDIN_FILENO || fd == STDOUT_FILENO)
1.2 markus 250: fatal("bad fd");
251: if ((host = get_local_name(fd)) == NULL)
1.30 dtucker 252: fatal("cannot get local name for fd");
1.4 deraadt 253:
1.46 djm 254: if ((r = sshbuf_get_string(b, &data, &dlen)) != 0)
1.50 djm 255: fatal("%s: buffer error: %s", __progname, ssh_err(r));
1.2 markus 256: if (valid_request(pw, host, &key, data, dlen) < 0)
1.1 markus 257: fatal("not a valid request");
1.37 djm 258: free(host);
1.1 markus 259:
260: found = 0;
1.36 djm 261: for (i = 0; i < NUM_KEYTYPES; i++) {
1.1 markus 262: if (keys[i] != NULL &&
1.46 djm 263: sshkey_equal_public(key, keys[i])) {
1.1 markus 264: found = 1;
265: break;
266: }
267: }
1.40 djm 268: if (!found) {
1.47 djm 269: if ((fp = sshkey_fingerprint(key, options.fingerprint_hash,
270: SSH_FP_DEFAULT)) == NULL)
1.50 djm 271: fatal("%s: sshkey_fingerprint failed", __progname);
1.40 djm 272: fatal("no matching hostkey found for key %s %s",
1.46 djm 273: sshkey_type(key), fp ? fp : "");
1.40 djm 274: }
1.1 markus 275:
1.51 markus 276: if ((r = sshkey_sign(keys[i], &signature, &slen, data, dlen, NULL, 0))
277: != 0)
1.46 djm 278: fatal("sshkey_sign failed: %s", ssh_err(r));
1.37 djm 279: free(data);
1.4 deraadt 280:
1.1 markus 281: /* send reply */
1.46 djm 282: sshbuf_reset(b);
283: if ((r = sshbuf_put_string(b, signature, slen)) != 0)
1.50 djm 284: fatal("%s: buffer error: %s", __progname, ssh_err(r));
1.46 djm 285: if (ssh_msg_send(STDOUT_FILENO, version, b) == -1)
1.14 djm 286: fatal("ssh_msg_send failed");
1.1 markus 287:
288: return (0);
289: }
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