Annotation of src/usr.bin/ssh/hostfile.c, Revision 1.44
1.44 ! stevesk 1: /* $OpenBSD: hostfile.c,v 1.43 2006/07/26 13:57:17 stevesk 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:
39: #include "includes.h"
1.41 stevesk 40:
41: #include <sys/types.h>
42:
43: #include <netinet/in.h>
1.33 djm 44:
1.43 stevesk 45: #include <openssl/hmac.h>
46: #include <openssl/sha.h>
47:
1.33 djm 48: #include <resolv.h>
1.44 ! stevesk 49: #include <stdio.h>
1.43 stevesk 50: #include <stdlib.h>
1.42 stevesk 51: #include <string.h>
1.1 deraadt 52:
1.14 markus 53: #include "match.h"
54: #include "key.h"
55: #include "hostfile.h"
1.24 markus 56: #include "log.h"
1.33 djm 57: #include "xmalloc.h"
58:
59: static int
60: extract_salt(const char *s, u_int l, char *salt, size_t salt_len)
61: {
62: char *p, *b64salt;
63: u_int b64len;
64: int ret;
65:
66: if (l < sizeof(HASH_MAGIC) - 1) {
67: debug2("extract_salt: string too short");
68: return (-1);
69: }
70: if (strncmp(s, HASH_MAGIC, sizeof(HASH_MAGIC) - 1) != 0) {
71: debug2("extract_salt: invalid magic identifier");
72: return (-1);
73: }
74: s += sizeof(HASH_MAGIC) - 1;
75: l -= sizeof(HASH_MAGIC) - 1;
76: if ((p = memchr(s, HASH_DELIM, l)) == NULL) {
77: debug2("extract_salt: missing salt termination character");
78: return (-1);
79: }
80:
81: b64len = p - s;
82: /* Sanity check */
83: if (b64len == 0 || b64len > 1024) {
84: debug2("extract_salt: bad encoded salt length %u", b64len);
85: return (-1);
86: }
87: b64salt = xmalloc(1 + b64len);
88: memcpy(b64salt, s, b64len);
89: b64salt[b64len] = '\0';
90:
91: ret = __b64_pton(b64salt, salt, salt_len);
92: xfree(b64salt);
93: if (ret == -1) {
94: debug2("extract_salt: salt decode error");
95: return (-1);
96: }
97: if (ret != SHA_DIGEST_LENGTH) {
1.36 dtucker 98: debug2("extract_salt: expected salt len %d, got %d",
99: SHA_DIGEST_LENGTH, ret);
1.33 djm 100: return (-1);
101: }
1.34 deraadt 102:
1.33 djm 103: return (0);
104: }
105:
106: char *
107: host_hash(const char *host, const char *name_from_hostfile, u_int src_len)
108: {
109: const EVP_MD *md = EVP_sha1();
110: HMAC_CTX mac_ctx;
111: char salt[256], result[256], uu_salt[512], uu_result[512];
112: static char encoded[1024];
113: u_int i, len;
114:
115: len = EVP_MD_size(md);
116:
117: if (name_from_hostfile == NULL) {
118: /* Create new salt */
119: for (i = 0; i < len; i++)
120: salt[i] = arc4random();
121: } else {
122: /* Extract salt from known host entry */
123: if (extract_salt(name_from_hostfile, src_len, salt,
124: sizeof(salt)) == -1)
125: return (NULL);
126: }
127:
128: HMAC_Init(&mac_ctx, salt, len, md);
129: HMAC_Update(&mac_ctx, host, strlen(host));
130: HMAC_Final(&mac_ctx, result, NULL);
131: HMAC_cleanup(&mac_ctx);
132:
1.34 deraadt 133: if (__b64_ntop(salt, len, uu_salt, sizeof(uu_salt)) == -1 ||
1.33 djm 134: __b64_ntop(result, len, uu_result, sizeof(uu_result)) == -1)
135: fatal("host_hash: __b64_ntop failed");
136:
137: snprintf(encoded, sizeof(encoded), "%s%s%c%s", HASH_MAGIC, uu_salt,
138: HASH_DELIM, uu_result);
139:
140: return (encoded);
141: }
1.1 deraadt 142:
1.9 markus 143: /*
1.14 markus 144: * Parses an RSA (number of bits, e, n) or DSA key from a string. Moves the
145: * pointer over the key. Skips any whitespace at the beginning and at end.
1.9 markus 146: */
1.1 deraadt 147:
1.29 jakob 148: int
1.22 markus 149: hostfile_read_key(char **cpp, u_int *bitsp, Key *ret)
1.1 deraadt 150: {
1.7 markus 151: char *cp;
152:
153: /* Skip leading whitespace. */
1.9 markus 154: for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++)
155: ;
1.1 deraadt 156:
1.21 markus 157: if (key_read(ret, &cp) != 1)
1.7 markus 158: return 0;
159:
160: /* Skip trailing whitespace. */
1.9 markus 161: for (; *cp == ' ' || *cp == '\t'; cp++)
162: ;
1.7 markus 163:
164: /* Return results. */
165: *cpp = cp;
1.21 markus 166: *bitsp = key_size(ret);
1.7 markus 167: return 1;
1.14 markus 168: }
1.1 deraadt 169:
1.27 itojun 170: static int
1.32 jakob 171: hostfile_check_key(int bits, const Key *key, const char *host, const char *filename, int linenum)
1.1 deraadt 172: {
1.21 markus 173: if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL)
1.14 markus 174: return 1;
175: if (bits != BN_num_bits(key->rsa->n)) {
1.31 itojun 176: logit("Warning: %s, line %d: keysize mismatch for host %s: "
1.14 markus 177: "actual %d vs. announced %d.",
178: filename, linenum, host, BN_num_bits(key->rsa->n), bits);
1.31 itojun 179: logit("Warning: replace %d with %d in %s, line %d.",
1.14 markus 180: bits, BN_num_bits(key->rsa->n), filename, linenum);
1.1 deraadt 181: }
1.14 markus 182: return 1;
1.1 deraadt 183: }
184:
1.9 markus 185: /*
186: * Checks whether the given host (which must be in all lowercase) is already
187: * in the list of our known hosts. Returns HOST_OK if the host is known and
188: * has the specified key, HOST_NEW if the host is not known, and HOST_CHANGED
189: * if the host is known but used to have a different host key.
1.30 markus 190: *
191: * If no 'key' has been specified and a key of type 'keytype' is known
192: * for the specified host, then HOST_FOUND is returned.
1.9 markus 193: */
1.1 deraadt 194:
1.30 markus 195: static HostStatus
196: check_host_in_hostfile_by_key_or_type(const char *filename,
1.32 jakob 197: const char *host, const Key *key, int keytype, Key *found, int *numret)
1.1 deraadt 198: {
1.7 markus 199: FILE *f;
200: char line[8192];
201: int linenum = 0;
1.25 stevesk 202: u_int kbits;
1.33 djm 203: char *cp, *cp2, *hashed_host;
1.7 markus 204: HostStatus end_return;
205:
1.26 markus 206: debug3("check_host_in_hostfile: filename %s", filename);
1.30 markus 207:
1.7 markus 208: /* Open the file containing the list of known hosts. */
209: f = fopen(filename, "r");
210: if (!f)
211: return HOST_NEW;
212:
1.9 markus 213: /*
214: * Return value when the loop terminates. This is set to
215: * HOST_CHANGED if we have seen a different key for the host and have
216: * not found the proper one.
217: */
1.7 markus 218: end_return = HOST_NEW;
219:
1.25 stevesk 220: /* Go through the file. */
1.7 markus 221: while (fgets(line, sizeof(line), f)) {
222: cp = line;
223: linenum++;
224:
1.9 markus 225: /* Skip any leading whitespace, comments and empty lines. */
226: for (; *cp == ' ' || *cp == '\t'; cp++)
227: ;
1.7 markus 228: if (!*cp || *cp == '#' || *cp == '\n')
229: continue;
230:
231: /* Find the end of the host name portion. */
1.9 markus 232: for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++)
233: ;
1.7 markus 234:
235: /* Check if the host name matches. */
1.33 djm 236: if (match_hostname(host, cp, (u_int) (cp2 - cp)) != 1) {
237: if (*cp != HASH_DELIM)
238: continue;
239: hashed_host = host_hash(host, cp, (u_int) (cp2 - cp));
240: if (hashed_host == NULL) {
241: debug("Invalid hashed host line %d of %s",
242: linenum, filename);
243: continue;
244: }
245: if (strncmp(hashed_host, cp, (u_int) (cp2 - cp)) != 0)
246: continue;
247: }
1.7 markus 248:
249: /* Got a match. Skip host name. */
250: cp = cp2;
251:
1.9 markus 252: /*
253: * Extract the key from the line. This will skip any leading
254: * whitespace. Ignore badly formatted lines.
255: */
1.14 markus 256: if (!hostfile_read_key(&cp, &kbits, found))
257: continue;
1.23 markus 258:
259: if (numret != NULL)
260: *numret = linenum;
1.7 markus 261:
1.30 markus 262: if (key == NULL) {
263: /* we found a key of the requested type */
1.38 djm 264: if (found->type == keytype) {
265: fclose(f);
1.30 markus 266: return HOST_FOUND;
1.38 djm 267: }
1.30 markus 268: continue;
269: }
270:
271: if (!hostfile_check_key(kbits, found, host, filename, linenum))
272: continue;
273:
1.7 markus 274: /* Check if the current key is the same as the given key. */
1.14 markus 275: if (key_equal(key, found)) {
1.7 markus 276: /* Ok, they match. */
1.26 markus 277: debug3("check_host_in_hostfile: match line %d", linenum);
1.7 markus 278: fclose(f);
279: return HOST_OK;
280: }
1.9 markus 281: /*
282: * They do not match. We will continue to go through the
283: * file; however, we note that we will not return that it is
284: * new.
285: */
1.7 markus 286: end_return = HOST_CHANGED;
1.1 deraadt 287: }
1.7 markus 288: /* Clear variables and close the file. */
289: fclose(f);
290:
1.9 markus 291: /*
292: * Return either HOST_NEW or HOST_CHANGED, depending on whether we
293: * saw a different key for the host.
294: */
1.7 markus 295: return end_return;
1.30 markus 296: }
297:
298: HostStatus
1.32 jakob 299: check_host_in_hostfile(const char *filename, const char *host, const Key *key,
1.30 markus 300: Key *found, int *numret)
301: {
302: if (key == NULL)
303: fatal("no key to look up");
304: return (check_host_in_hostfile_by_key_or_type(filename, host, key, 0,
305: found, numret));
306: }
307:
308: int
309: lookup_key_in_hostfile_by_type(const char *filename, const char *host,
310: int keytype, Key *found, int *numret)
311: {
312: return (check_host_in_hostfile_by_key_or_type(filename, host, NULL,
313: keytype, found, numret) == HOST_FOUND);
1.1 deraadt 314: }
315:
1.9 markus 316: /*
317: * Appends an entry to the host file. Returns false if the entry could not
318: * be appended.
319: */
1.1 deraadt 320:
1.2 provos 321: int
1.34 deraadt 322: add_host_to_hostfile(const char *filename, const char *host, const Key *key,
1.33 djm 323: int store_hash)
1.1 deraadt 324: {
1.7 markus 325: FILE *f;
1.14 markus 326: int success = 0;
1.35 dtucker 327: char *hashed_host = NULL;
1.33 djm 328:
1.14 markus 329: if (key == NULL)
1.17 markus 330: return 1; /* XXX ? */
1.7 markus 331: f = fopen(filename, "a");
332: if (!f)
333: return 0;
1.33 djm 334:
335: if (store_hash) {
336: if ((hashed_host = host_hash(host, NULL, 0)) == NULL) {
337: error("add_host_to_hostfile: host_hash failed");
338: fclose(f);
339: return 0;
340: }
341: }
342: fprintf(f, "%s ", store_hash ? hashed_host : host);
343:
1.14 markus 344: if (key_write(key, f)) {
345: success = 1;
346: } else {
1.17 markus 347: error("add_host_to_hostfile: saving key in %s failed", filename);
1.7 markus 348: }
1.17 markus 349: fprintf(f, "\n");
1.7 markus 350: fclose(f);
1.14 markus 351: return success;
1.1 deraadt 352: }
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