Annotation of src/usr.bin/ssh/ssh-keysign.c, Revision 1.55
1.55 ! dtucker 1: /* $OpenBSD: ssh-keysign.c,v 1.54 2018/02/23 15:58:38 markus 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:
1.1 markus 57: static int
1.46 djm 58: valid_request(struct passwd *pw, char *host, struct sshkey **ret,
59: u_char *data, size_t datalen)
1.1 markus 60: {
1.46 djm 61: struct sshbuf *b;
62: struct sshkey *key = NULL;
63: u_char type, *pkblob;
64: char *p;
65: size_t blen, len;
66: char *pkalg, *luser;
67: int r, pktype, fail;
1.1 markus 68:
1.45 djm 69: if (ret != NULL)
70: *ret = NULL;
1.1 markus 71: fail = 0;
72:
1.46 djm 73: if ((b = sshbuf_from(data, datalen)) == NULL)
74: fatal("%s: sshbuf_from failed", __func__);
1.4 deraadt 75:
1.23 dtucker 76: /* session id, currently limited to SHA1 (20 bytes) or SHA256 (32) */
1.46 djm 77: if ((r = sshbuf_get_string(b, NULL, &len)) != 0)
78: fatal("%s: buffer error: %s", __func__, ssh_err(r));
1.23 dtucker 79: if (len != 20 && len != 32)
1.3 markus 80: fail++;
81:
1.46 djm 82: if ((r = sshbuf_get_u8(b, &type)) != 0)
83: fatal("%s: buffer error: %s", __func__, ssh_err(r));
84: if (type != SSH2_MSG_USERAUTH_REQUEST)
1.1 markus 85: fail++;
86:
87: /* server user */
1.46 djm 88: if ((r = sshbuf_skip_string(b)) != 0)
89: fatal("%s: buffer error: %s", __func__, ssh_err(r));
1.1 markus 90:
91: /* service */
1.46 djm 92: if ((r = sshbuf_get_cstring(b, &p, NULL)) != 0)
93: fatal("%s: buffer error: %s", __func__, ssh_err(r));
1.1 markus 94: if (strcmp("ssh-connection", p) != 0)
95: fail++;
1.37 djm 96: free(p);
1.1 markus 97:
98: /* method */
1.46 djm 99: if ((r = sshbuf_get_cstring(b, &p, NULL)) != 0)
100: fatal("%s: buffer error: %s", __func__, ssh_err(r));
1.1 markus 101: if (strcmp("hostbased", p) != 0)
102: fail++;
1.37 djm 103: free(p);
1.1 markus 104:
105: /* pubkey */
1.46 djm 106: if ((r = sshbuf_get_cstring(b, &pkalg, NULL)) != 0 ||
107: (r = sshbuf_get_string(b, &pkblob, &blen)) != 0)
108: fatal("%s: buffer error: %s", __func__, ssh_err(r));
1.1 markus 109:
1.46 djm 110: pktype = sshkey_type_from_name(pkalg);
1.1 markus 111: if (pktype == KEY_UNSPEC)
112: fail++;
1.46 djm 113: else if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) {
114: error("%s: bad key blob: %s", __func__, ssh_err(r));
1.1 markus 115: fail++;
1.46 djm 116: } else if (key->type != pktype)
1.1 markus 117: fail++;
1.37 djm 118: free(pkalg);
119: free(pkblob);
1.1 markus 120:
1.2 markus 121: /* client host name, handle trailing dot */
1.46 djm 122: if ((r = sshbuf_get_cstring(b, &p, &len)) != 0)
123: fatal("%s: buffer error: %s", __func__, ssh_err(r));
124: debug2("%s: check expect chost %s got %s", __func__, host, p);
1.2 markus 125: if (strlen(host) != len - 1)
126: fail++;
127: else if (p[len - 1] != '.')
1.4 deraadt 128: fail++;
1.2 markus 129: else if (strncasecmp(host, p, len - 1) != 0)
1.4 deraadt 130: fail++;
1.37 djm 131: free(p);
1.1 markus 132:
133: /* local user */
1.46 djm 134: if ((r = sshbuf_get_cstring(b, &luser, NULL)) != 0)
135: fatal("%s: buffer error: %s", __func__, ssh_err(r));
1.2 markus 136:
1.46 djm 137: if (strcmp(pw->pw_name, luser) != 0)
1.1 markus 138: fail++;
1.46 djm 139: free(luser);
1.1 markus 140:
141: /* end of message */
1.46 djm 142: if (sshbuf_len(b) != 0)
1.1 markus 143: fail++;
1.46 djm 144: sshbuf_free(b);
1.1 markus 145:
1.46 djm 146: debug3("%s: fail %d", __func__, fail);
1.1 markus 147:
1.53 dtucker 148: if (fail)
1.46 djm 149: sshkey_free(key);
1.48 markus 150: else if (ret != NULL)
1.1 markus 151: *ret = key;
152:
153: return (fail ? -1 : 0);
154: }
155:
156: int
157: main(int argc, char **argv)
158: {
1.46 djm 159: struct sshbuf *b;
1.7 markus 160: Options options;
1.54 markus 161: #define NUM_KEYTYPES 5
1.46 djm 162: struct sshkey *keys[NUM_KEYTYPES], *key = NULL;
1.1 markus 163: struct passwd *pw;
1.45 djm 164: int r, key_fd[NUM_KEYTYPES], i, found, version = 2, fd;
1.46 djm 165: u_char *signature, *data, rver;
1.40 djm 166: char *host, *fp;
1.46 djm 167: size_t slen, dlen;
1.19 djm 168:
1.52 dtucker 169: ssh_malloc_init(); /* must be called before any mallocs */
1.50 djm 170: if (pledge("stdio rpath getpw dns id", NULL) != 0)
171: fatal("%s: pledge: %s", __progname, strerror(errno));
172:
1.19 djm 173: /* Ensure that stdin and stdout are connected */
174: if ((fd = open(_PATH_DEVNULL, O_RDWR)) < 2)
175: exit(1);
176: /* Leave /dev/null fd iff it is attached to stderr */
177: if (fd > 2)
178: close(fd);
1.1 markus 179:
1.36 djm 180: i = 0;
1.49 djm 181: /* XXX This really needs to read sshd_config for the paths */
1.36 djm 182: key_fd[i++] = open(_PATH_HOST_DSA_KEY_FILE, O_RDONLY);
183: key_fd[i++] = open(_PATH_HOST_ECDSA_KEY_FILE, O_RDONLY);
1.39 markus 184: key_fd[i++] = open(_PATH_HOST_ED25519_KEY_FILE, O_RDONLY);
1.54 markus 185: key_fd[i++] = open(_PATH_HOST_XMSS_KEY_FILE, O_RDONLY);
1.36 djm 186: key_fd[i++] = open(_PATH_HOST_RSA_KEY_FILE, O_RDONLY);
1.1 markus 187:
1.55 ! dtucker 188: if ((pw = getpwuid(getuid())) == NULL)
1.17 dtucker 189: fatal("getpwuid failed");
190: pw = pwcopy(pw);
191:
192: permanently_set_uid(pw);
1.1 markus 193:
194: #ifdef DEBUG_SSH_KEYSIGN
195: log_init("ssh-keysign", SYSLOG_LEVEL_DEBUG3, SYSLOG_FACILITY_AUTH, 0);
1.4 deraadt 196: #endif
1.7 markus 197:
198: /* verify that ssh-keysign is enabled by the admin */
199: initialize_options(&options);
1.43 djm 200: (void)read_config_file(_PATH_HOST_CONFIG_FILE, pw, "", "", &options, 0);
1.7 markus 201: fill_default_options(&options);
1.8 markus 202: if (options.enable_ssh_keysign != 1)
203: fatal("ssh-keysign not enabled in %s",
1.7 markus 204: _PATH_HOST_CONFIG_FILE);
1.1 markus 205:
1.36 djm 206: for (i = found = 0; i < NUM_KEYTYPES; i++) {
207: if (key_fd[i] != -1)
208: found = 1;
209: }
210: if (found == 0)
1.1 markus 211: fatal("could not open any host key");
212:
1.35 djm 213: OpenSSL_add_all_algorithms();
1.1 markus 214:
215: found = 0;
1.36 djm 216: for (i = 0; i < NUM_KEYTYPES; i++) {
1.1 markus 217: keys[i] = NULL;
218: if (key_fd[i] == -1)
219: continue;
1.45 djm 220: r = sshkey_load_private_type_fd(key_fd[i], KEY_UNSPEC,
221: NULL, &key, NULL);
1.1 markus 222: close(key_fd[i]);
1.45 djm 223: if (r != 0)
224: debug("parse key %d: %s", i, ssh_err(r));
225: else if (key != NULL) {
226: keys[i] = key;
1.1 markus 227: found = 1;
1.45 djm 228: }
1.1 markus 229: }
230: if (!found)
231: fatal("no hostkey found");
232:
1.50 djm 233: if (pledge("stdio dns", NULL) != 0)
234: fatal("%s: pledge: %s", __progname, strerror(errno));
235:
1.46 djm 236: if ((b = sshbuf_new()) == NULL)
1.50 djm 237: fatal("%s: sshbuf_new failed", __progname);
1.46 djm 238: if (ssh_msg_recv(STDIN_FILENO, b) < 0)
1.9 djm 239: fatal("ssh_msg_recv failed");
1.46 djm 240: if ((r = sshbuf_get_u8(b, &rver)) != 0)
1.50 djm 241: fatal("%s: buffer error: %s", __progname, ssh_err(r));
1.46 djm 242: if (rver != version)
243: fatal("bad version: received %d, expected %d", rver, version);
244: if ((r = sshbuf_get_u32(b, (u_int *)&fd)) != 0)
1.50 djm 245: fatal("%s: buffer error: %s", __progname, ssh_err(r));
1.46 djm 246: if (fd < 0 || fd == STDIN_FILENO || fd == STDOUT_FILENO)
1.2 markus 247: fatal("bad fd");
248: if ((host = get_local_name(fd)) == NULL)
1.30 dtucker 249: fatal("cannot get local name for fd");
1.4 deraadt 250:
1.46 djm 251: if ((r = sshbuf_get_string(b, &data, &dlen)) != 0)
1.50 djm 252: fatal("%s: buffer error: %s", __progname, ssh_err(r));
1.2 markus 253: if (valid_request(pw, host, &key, data, dlen) < 0)
1.1 markus 254: fatal("not a valid request");
1.37 djm 255: free(host);
1.1 markus 256:
257: found = 0;
1.36 djm 258: for (i = 0; i < NUM_KEYTYPES; i++) {
1.1 markus 259: if (keys[i] != NULL &&
1.46 djm 260: sshkey_equal_public(key, keys[i])) {
1.1 markus 261: found = 1;
262: break;
263: }
264: }
1.40 djm 265: if (!found) {
1.47 djm 266: if ((fp = sshkey_fingerprint(key, options.fingerprint_hash,
267: SSH_FP_DEFAULT)) == NULL)
1.50 djm 268: fatal("%s: sshkey_fingerprint failed", __progname);
1.40 djm 269: fatal("no matching hostkey found for key %s %s",
1.46 djm 270: sshkey_type(key), fp ? fp : "");
1.40 djm 271: }
1.1 markus 272:
1.51 markus 273: if ((r = sshkey_sign(keys[i], &signature, &slen, data, dlen, NULL, 0))
274: != 0)
1.46 djm 275: fatal("sshkey_sign failed: %s", ssh_err(r));
1.37 djm 276: free(data);
1.4 deraadt 277:
1.1 markus 278: /* send reply */
1.46 djm 279: sshbuf_reset(b);
280: if ((r = sshbuf_put_string(b, signature, slen)) != 0)
1.50 djm 281: fatal("%s: buffer error: %s", __progname, ssh_err(r));
1.46 djm 282: if (ssh_msg_send(STDOUT_FILENO, version, b) == -1)
1.14 djm 283: fatal("ssh_msg_send failed");
1.1 markus 284:
285: return (0);
286: }
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