Annotation of src/usr.bin/ssh/hostfile.c, Revision 1.50
1.50 ! djm 1: /* $OpenBSD: hostfile.c,v 1.49 2010/11/29 23:45:51 djm Exp $ */
1.1 deraadt 2: /*
1.8 deraadt 3: * Author: Tatu Ylonen <ylo@cs.hut.fi>
4: * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5: * All rights reserved
6: * Functions for manipulating the known hosts files.
1.16 markus 7: *
1.20 deraadt 8: * As far as I am concerned, the code I have written for this software
9: * can be used freely for any purpose. Any derived versions of this
10: * software must be clearly marked as such, and if the derived work is
11: * incompatible with the protocol description in the RFC file, it must be
12: * called by a name other than "ssh" or "Secure Shell".
13: *
14: *
1.28 markus 15: * Copyright (c) 1999, 2000 Markus Friedl. All rights reserved.
1.20 deraadt 16: * Copyright (c) 1999 Niels Provos. All rights reserved.
17: *
18: * Redistribution and use in source and binary forms, with or without
19: * modification, are permitted provided that the following conditions
20: * are met:
21: * 1. Redistributions of source code must retain the above copyright
22: * notice, this list of conditions and the following disclaimer.
23: * 2. Redistributions in binary form must reproduce the above copyright
24: * notice, this list of conditions and the following disclaimer in the
25: * documentation and/or other materials provided with the distribution.
26: *
27: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
28: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
29: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
30: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
31: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
32: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
33: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
34: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
35: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
36: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
1.8 deraadt 37: */
1.1 deraadt 38:
1.41 stevesk 39: #include <sys/types.h>
40:
41: #include <netinet/in.h>
1.33 djm 42:
1.43 stevesk 43: #include <openssl/hmac.h>
44: #include <openssl/sha.h>
45:
1.33 djm 46: #include <resolv.h>
1.44 stevesk 47: #include <stdio.h>
1.43 stevesk 48: #include <stdlib.h>
1.42 stevesk 49: #include <string.h>
1.1 deraadt 50:
1.45 deraadt 51: #include "xmalloc.h"
1.14 markus 52: #include "match.h"
53: #include "key.h"
54: #include "hostfile.h"
1.24 markus 55: #include "log.h"
1.49 djm 56: #include "misc.h"
57:
58: struct hostkeys {
59: struct hostkey_entry *entries;
60: u_int num_entries;
61: };
1.33 djm 62:
63: static int
64: extract_salt(const char *s, u_int l, char *salt, size_t salt_len)
65: {
66: char *p, *b64salt;
67: u_int b64len;
68: int ret;
69:
70: if (l < sizeof(HASH_MAGIC) - 1) {
71: debug2("extract_salt: string too short");
72: return (-1);
73: }
74: if (strncmp(s, HASH_MAGIC, sizeof(HASH_MAGIC) - 1) != 0) {
75: debug2("extract_salt: invalid magic identifier");
76: return (-1);
77: }
78: s += sizeof(HASH_MAGIC) - 1;
79: l -= sizeof(HASH_MAGIC) - 1;
80: if ((p = memchr(s, HASH_DELIM, l)) == NULL) {
81: debug2("extract_salt: missing salt termination character");
82: return (-1);
83: }
84:
85: b64len = p - s;
86: /* Sanity check */
87: if (b64len == 0 || b64len > 1024) {
88: debug2("extract_salt: bad encoded salt length %u", b64len);
89: return (-1);
90: }
91: b64salt = xmalloc(1 + b64len);
92: memcpy(b64salt, s, b64len);
93: b64salt[b64len] = '\0';
94:
95: ret = __b64_pton(b64salt, salt, salt_len);
96: xfree(b64salt);
97: if (ret == -1) {
98: debug2("extract_salt: salt decode error");
99: return (-1);
100: }
101: if (ret != SHA_DIGEST_LENGTH) {
1.36 dtucker 102: debug2("extract_salt: expected salt len %d, got %d",
103: SHA_DIGEST_LENGTH, ret);
1.33 djm 104: return (-1);
105: }
1.34 deraadt 106:
1.33 djm 107: return (0);
108: }
109:
110: char *
111: host_hash(const char *host, const char *name_from_hostfile, u_int src_len)
112: {
113: const EVP_MD *md = EVP_sha1();
114: HMAC_CTX mac_ctx;
115: char salt[256], result[256], uu_salt[512], uu_result[512];
116: static char encoded[1024];
117: u_int i, len;
118:
119: len = EVP_MD_size(md);
120:
121: if (name_from_hostfile == NULL) {
122: /* Create new salt */
123: for (i = 0; i < len; i++)
124: salt[i] = arc4random();
125: } else {
126: /* Extract salt from known host entry */
127: if (extract_salt(name_from_hostfile, src_len, salt,
128: sizeof(salt)) == -1)
129: return (NULL);
130: }
131:
132: HMAC_Init(&mac_ctx, salt, len, md);
133: HMAC_Update(&mac_ctx, host, strlen(host));
134: HMAC_Final(&mac_ctx, result, NULL);
135: HMAC_cleanup(&mac_ctx);
136:
1.34 deraadt 137: if (__b64_ntop(salt, len, uu_salt, sizeof(uu_salt)) == -1 ||
1.33 djm 138: __b64_ntop(result, len, uu_result, sizeof(uu_result)) == -1)
139: fatal("host_hash: __b64_ntop failed");
140:
141: snprintf(encoded, sizeof(encoded), "%s%s%c%s", HASH_MAGIC, uu_salt,
142: HASH_DELIM, uu_result);
143:
144: return (encoded);
145: }
1.1 deraadt 146:
1.9 markus 147: /*
1.14 markus 148: * Parses an RSA (number of bits, e, n) or DSA key from a string. Moves the
149: * pointer over the key. Skips any whitespace at the beginning and at end.
1.9 markus 150: */
1.1 deraadt 151:
1.29 jakob 152: int
1.22 markus 153: hostfile_read_key(char **cpp, u_int *bitsp, Key *ret)
1.1 deraadt 154: {
1.7 markus 155: char *cp;
156:
157: /* Skip leading whitespace. */
1.9 markus 158: for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++)
159: ;
1.1 deraadt 160:
1.21 markus 161: if (key_read(ret, &cp) != 1)
1.7 markus 162: return 0;
163:
164: /* Skip trailing whitespace. */
1.9 markus 165: for (; *cp == ' ' || *cp == '\t'; cp++)
166: ;
1.7 markus 167:
168: /* Return results. */
169: *cpp = cp;
1.49 djm 170: if (bitsp != NULL)
171: *bitsp = key_size(ret);
1.7 markus 172: return 1;
1.14 markus 173: }
1.1 deraadt 174:
1.27 itojun 175: static int
1.49 djm 176: hostfile_check_key(int bits, const Key *key, const char *host,
177: const char *filename, u_long linenum)
1.1 deraadt 178: {
1.21 markus 179: if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL)
1.14 markus 180: return 1;
181: if (bits != BN_num_bits(key->rsa->n)) {
1.49 djm 182: logit("Warning: %s, line %lu: keysize mismatch for host %s: "
1.14 markus 183: "actual %d vs. announced %d.",
184: filename, linenum, host, BN_num_bits(key->rsa->n), bits);
1.49 djm 185: logit("Warning: replace %d with %d in %s, line %lu.",
1.14 markus 186: bits, BN_num_bits(key->rsa->n), filename, linenum);
1.1 deraadt 187: }
1.14 markus 188: return 1;
1.1 deraadt 189: }
190:
1.49 djm 191: static HostkeyMarker
1.48 djm 192: check_markers(char **cpp)
193: {
194: char marker[32], *sp, *cp = *cpp;
195: int ret = MRK_NONE;
196:
197: while (*cp == '@') {
198: /* Only one marker is allowed */
199: if (ret != MRK_NONE)
200: return MRK_ERROR;
201: /* Markers are terminated by whitespace */
202: if ((sp = strchr(cp, ' ')) == NULL &&
203: (sp = strchr(cp, '\t')) == NULL)
204: return MRK_ERROR;
205: /* Extract marker for comparison */
206: if (sp <= cp + 1 || sp >= cp + sizeof(marker))
207: return MRK_ERROR;
208: memcpy(marker, cp, sp - cp);
209: marker[sp - cp] = '\0';
210: if (strcmp(marker, CA_MARKER) == 0)
211: ret = MRK_CA;
212: else if (strcmp(marker, REVOKE_MARKER) == 0)
213: ret = MRK_REVOKE;
214: else
215: return MRK_ERROR;
216:
217: /* Skip past marker and any whitespace that follows it */
218: cp = sp;
219: for (; *cp == ' ' || *cp == '\t'; cp++)
220: ;
221: }
222: *cpp = cp;
223: return ret;
224: }
225:
1.49 djm 226: struct hostkeys *
227: init_hostkeys(void)
228: {
229: struct hostkeys *ret = xcalloc(1, sizeof(*ret));
230:
231: ret->entries = NULL;
232: return ret;
233: }
1.1 deraadt 234:
1.49 djm 235: void
236: load_hostkeys(struct hostkeys *hostkeys, const char *host, const char *path)
1.1 deraadt 237: {
1.7 markus 238: FILE *f;
239: char line[8192];
1.49 djm 240: u_long linenum = 0, num_loaded = 0;
1.33 djm 241: char *cp, *cp2, *hashed_host;
1.49 djm 242: HostkeyMarker marker;
243: Key *key;
244: int kbits;
245:
246: if ((f = fopen(path, "r")) == NULL)
247: return;
248: debug3("%s: loading entries for host \"%.100s\" from file \"%s\"",
249: __func__, host, path);
250: while (read_keyfile_line(f, path, line, sizeof(line), &linenum) == 0) {
1.7 markus 251: cp = line;
252:
1.9 markus 253: /* Skip any leading whitespace, comments and empty lines. */
254: for (; *cp == ' ' || *cp == '\t'; cp++)
255: ;
1.7 markus 256: if (!*cp || *cp == '#' || *cp == '\n')
257: continue;
258:
1.49 djm 259: if ((marker = check_markers(&cp)) == MRK_ERROR) {
260: verbose("%s: invalid marker at %s:%lu",
261: __func__, path, linenum);
1.47 djm 262: continue;
1.49 djm 263: }
1.47 djm 264:
1.7 markus 265: /* Find the end of the host name portion. */
1.9 markus 266: for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++)
267: ;
1.7 markus 268:
269: /* Check if the host name matches. */
1.33 djm 270: if (match_hostname(host, cp, (u_int) (cp2 - cp)) != 1) {
271: if (*cp != HASH_DELIM)
272: continue;
273: hashed_host = host_hash(host, cp, (u_int) (cp2 - cp));
274: if (hashed_host == NULL) {
1.49 djm 275: debug("Invalid hashed host line %lu of %s",
276: linenum, path);
1.33 djm 277: continue;
278: }
279: if (strncmp(hashed_host, cp, (u_int) (cp2 - cp)) != 0)
280: continue;
281: }
1.7 markus 282:
283: /* Got a match. Skip host name. */
284: cp = cp2;
285:
1.9 markus 286: /*
287: * Extract the key from the line. This will skip any leading
288: * whitespace. Ignore badly formatted lines.
289: */
1.49 djm 290: key = key_new(KEY_UNSPEC);
291: if (!hostfile_read_key(&cp, &kbits, key)) {
292: key_free(key);
293: key = key_new(KEY_RSA1);
294: if (!hostfile_read_key(&cp, &kbits, key)) {
295: key_free(key);
296: continue;
297: }
298: }
299: if (!hostfile_check_key(kbits, key, host, path, linenum))
1.14 markus 300: continue;
1.23 markus 301:
1.49 djm 302: debug3("%s: found %skey type %s in file %s:%lu", __func__,
303: marker == MRK_NONE ? "" :
304: (marker == MRK_CA ? "ca " : "revoked "),
305: key_type(key), path, linenum);
306: hostkeys->entries = xrealloc(hostkeys->entries,
307: hostkeys->num_entries + 1, sizeof(*hostkeys->entries));
308: hostkeys->entries[hostkeys->num_entries].host = xstrdup(host);
309: hostkeys->entries[hostkeys->num_entries].file = xstrdup(path);
310: hostkeys->entries[hostkeys->num_entries].line = linenum;
311: hostkeys->entries[hostkeys->num_entries].key = key;
312: hostkeys->entries[hostkeys->num_entries].marker = marker;
313: hostkeys->num_entries++;
314: num_loaded++;
315: }
316: debug3("%s: loaded %lu keys", __func__, num_loaded);
1.50 ! djm 317: fclose(f);
1.49 djm 318: return;
319: }
320:
321: void
322: free_hostkeys(struct hostkeys *hostkeys)
323: {
324: u_int i;
325:
326: for (i = 0; i < hostkeys->num_entries; i++) {
327: xfree(hostkeys->entries[i].host);
328: xfree(hostkeys->entries[i].file);
329: key_free(hostkeys->entries[i].key);
330: bzero(hostkeys->entries + i, sizeof(*hostkeys->entries));
331: }
332: if (hostkeys->entries != NULL)
333: xfree(hostkeys->entries);
334: hostkeys->entries = NULL;
335: hostkeys->num_entries = 0;
336: xfree(hostkeys);
337: }
338:
339: static int
340: check_key_not_revoked(struct hostkeys *hostkeys, Key *k)
341: {
342: int is_cert = key_is_cert(k);
343: u_int i;
1.7 markus 344:
1.49 djm 345: for (i = 0; i < hostkeys->num_entries; i++) {
346: if (hostkeys->entries[i].marker != MRK_REVOKE)
1.30 markus 347: continue;
1.49 djm 348: if (key_equal_public(k, hostkeys->entries[i].key))
349: return -1;
350: if (is_cert &&
351: key_equal_public(k->cert->signature_key,
352: hostkeys->entries[i].key))
353: return -1;
354: }
355: return 0;
356: }
357:
358: /*
359: * Match keys against a specified key, or look one up by key type.
360: *
361: * If looking for a keytype (key == NULL) and one is found then return
362: * HOST_FOUND, otherwise HOST_NEW.
363: *
364: * If looking for a key (key != NULL):
365: * 1. If the key is a cert and a matching CA is found, return HOST_OK
366: * 2. If the key is not a cert and a matching key is found, return HOST_OK
367: * 3. If no key matches but a key with a different type is found, then
368: * return HOST_CHANGED
369: * 4. If no matching keys are found, then return HOST_NEW.
370: *
371: * Finally, check any found key is not revoked.
372: */
373: static HostStatus
374: check_hostkeys_by_key_or_type(struct hostkeys *hostkeys,
375: Key *k, int keytype, const struct hostkey_entry **found)
376: {
377: u_int i;
378: HostStatus end_return = HOST_NEW;
379: int want_cert = key_is_cert(k);
380: HostkeyMarker want_marker = want_cert ? MRK_CA : MRK_NONE;
381: int proto = (k ? k->type : keytype) == KEY_RSA1 ? 1 : 2;
382:
383: if (found != NULL)
384: *found = NULL;
1.30 markus 385:
1.49 djm 386: for (i = 0; i < hostkeys->num_entries; i++) {
387: if (proto == 1 && hostkeys->entries[i].key->type != KEY_RSA1)
388: continue;
389: if (proto == 2 && hostkeys->entries[i].key->type == KEY_RSA1)
1.30 markus 390: continue;
1.49 djm 391: if (hostkeys->entries[i].marker != want_marker)
392: continue;
393: if (k == NULL) {
394: if (hostkeys->entries[i].key->type != keytype)
395: continue;
396: end_return = HOST_FOUND;
397: if (found != NULL)
398: *found = hostkeys->entries + i;
399: k = hostkeys->entries[i].key;
400: break;
401: }
402: if (want_cert) {
403: if (key_equal_public(k->cert->signature_key,
404: hostkeys->entries[i].key)) {
405: /* A matching CA exists */
406: end_return = HOST_OK;
407: if (found != NULL)
408: *found = hostkeys->entries + i;
409: break;
1.48 djm 410: }
1.49 djm 411: } else {
412: if (key_equal(k, hostkeys->entries[i].key)) {
413: end_return = HOST_OK;
414: if (found != NULL)
415: *found = hostkeys->entries + i;
416: break;
1.48 djm 417: }
1.49 djm 418: /* A non-maching key exists */
419: end_return = HOST_CHANGED;
420: if (found != NULL)
421: *found = hostkeys->entries + i;
1.48 djm 422: }
1.1 deraadt 423: }
1.49 djm 424: if (check_key_not_revoked(hostkeys, k) != 0) {
425: end_return = HOST_REVOKED;
426: if (found != NULL)
427: *found = NULL;
428: }
1.7 markus 429: return end_return;
1.30 markus 430: }
1.49 djm 431:
1.30 markus 432: HostStatus
1.49 djm 433: check_key_in_hostkeys(struct hostkeys *hostkeys, Key *key,
434: const struct hostkey_entry **found)
1.30 markus 435: {
436: if (key == NULL)
437: fatal("no key to look up");
1.49 djm 438: return check_hostkeys_by_key_or_type(hostkeys, key, 0, found);
1.30 markus 439: }
440:
441: int
1.49 djm 442: lookup_key_in_hostkeys_by_type(struct hostkeys *hostkeys, int keytype,
443: const struct hostkey_entry **found)
1.30 markus 444: {
1.49 djm 445: return (check_hostkeys_by_key_or_type(hostkeys, NULL, keytype,
446: found) == HOST_FOUND);
1.1 deraadt 447: }
448:
1.9 markus 449: /*
450: * Appends an entry to the host file. Returns false if the entry could not
451: * be appended.
452: */
1.1 deraadt 453:
1.2 provos 454: int
1.34 deraadt 455: add_host_to_hostfile(const char *filename, const char *host, const Key *key,
1.33 djm 456: int store_hash)
1.1 deraadt 457: {
1.7 markus 458: FILE *f;
1.14 markus 459: int success = 0;
1.35 dtucker 460: char *hashed_host = NULL;
1.33 djm 461:
1.14 markus 462: if (key == NULL)
1.17 markus 463: return 1; /* XXX ? */
1.7 markus 464: f = fopen(filename, "a");
465: if (!f)
466: return 0;
1.33 djm 467:
468: if (store_hash) {
469: if ((hashed_host = host_hash(host, NULL, 0)) == NULL) {
470: error("add_host_to_hostfile: host_hash failed");
471: fclose(f);
472: return 0;
473: }
474: }
475: fprintf(f, "%s ", store_hash ? hashed_host : host);
476:
1.14 markus 477: if (key_write(key, f)) {
478: success = 1;
479: } else {
1.17 markus 480: error("add_host_to_hostfile: saving key in %s failed", filename);
1.7 markus 481: }
1.17 markus 482: fprintf(f, "\n");
1.7 markus 483: fclose(f);
1.14 markus 484: return success;
1.1 deraadt 485: }
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