Annotation of src/usr.bin/ssh/hostfile.c, Revision 1.41
1.41 ! stevesk 1: /* $OpenBSD: hostfile.c,v 1.40 2006/03/25 13:17:02 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:
39: #include "includes.h"
1.41 ! stevesk 40:
! 41: #include <sys/types.h>
! 42:
! 43: #include <netinet/in.h>
1.33 djm 44:
45: #include <resolv.h>
1.37 stevesk 46:
1.33 djm 47: #include <openssl/hmac.h>
48: #include <openssl/sha.h>
1.1 deraadt 49:
1.14 markus 50: #include "match.h"
51: #include "key.h"
52: #include "hostfile.h"
1.24 markus 53: #include "log.h"
1.33 djm 54: #include "xmalloc.h"
55:
56: static int
57: extract_salt(const char *s, u_int l, char *salt, size_t salt_len)
58: {
59: char *p, *b64salt;
60: u_int b64len;
61: int ret;
62:
63: if (l < sizeof(HASH_MAGIC) - 1) {
64: debug2("extract_salt: string too short");
65: return (-1);
66: }
67: if (strncmp(s, HASH_MAGIC, sizeof(HASH_MAGIC) - 1) != 0) {
68: debug2("extract_salt: invalid magic identifier");
69: return (-1);
70: }
71: s += sizeof(HASH_MAGIC) - 1;
72: l -= sizeof(HASH_MAGIC) - 1;
73: if ((p = memchr(s, HASH_DELIM, l)) == NULL) {
74: debug2("extract_salt: missing salt termination character");
75: return (-1);
76: }
77:
78: b64len = p - s;
79: /* Sanity check */
80: if (b64len == 0 || b64len > 1024) {
81: debug2("extract_salt: bad encoded salt length %u", b64len);
82: return (-1);
83: }
84: b64salt = xmalloc(1 + b64len);
85: memcpy(b64salt, s, b64len);
86: b64salt[b64len] = '\0';
87:
88: ret = __b64_pton(b64salt, salt, salt_len);
89: xfree(b64salt);
90: if (ret == -1) {
91: debug2("extract_salt: salt decode error");
92: return (-1);
93: }
94: if (ret != SHA_DIGEST_LENGTH) {
1.36 dtucker 95: debug2("extract_salt: expected salt len %d, got %d",
96: SHA_DIGEST_LENGTH, ret);
1.33 djm 97: return (-1);
98: }
1.34 deraadt 99:
1.33 djm 100: return (0);
101: }
102:
103: char *
104: host_hash(const char *host, const char *name_from_hostfile, u_int src_len)
105: {
106: const EVP_MD *md = EVP_sha1();
107: HMAC_CTX mac_ctx;
108: char salt[256], result[256], uu_salt[512], uu_result[512];
109: static char encoded[1024];
110: u_int i, len;
111:
112: len = EVP_MD_size(md);
113:
114: if (name_from_hostfile == NULL) {
115: /* Create new salt */
116: for (i = 0; i < len; i++)
117: salt[i] = arc4random();
118: } else {
119: /* Extract salt from known host entry */
120: if (extract_salt(name_from_hostfile, src_len, salt,
121: sizeof(salt)) == -1)
122: return (NULL);
123: }
124:
125: HMAC_Init(&mac_ctx, salt, len, md);
126: HMAC_Update(&mac_ctx, host, strlen(host));
127: HMAC_Final(&mac_ctx, result, NULL);
128: HMAC_cleanup(&mac_ctx);
129:
1.34 deraadt 130: if (__b64_ntop(salt, len, uu_salt, sizeof(uu_salt)) == -1 ||
1.33 djm 131: __b64_ntop(result, len, uu_result, sizeof(uu_result)) == -1)
132: fatal("host_hash: __b64_ntop failed");
133:
134: snprintf(encoded, sizeof(encoded), "%s%s%c%s", HASH_MAGIC, uu_salt,
135: HASH_DELIM, uu_result);
136:
137: return (encoded);
138: }
1.1 deraadt 139:
1.9 markus 140: /*
1.14 markus 141: * Parses an RSA (number of bits, e, n) or DSA key from a string. Moves the
142: * pointer over the key. Skips any whitespace at the beginning and at end.
1.9 markus 143: */
1.1 deraadt 144:
1.29 jakob 145: int
1.22 markus 146: hostfile_read_key(char **cpp, u_int *bitsp, Key *ret)
1.1 deraadt 147: {
1.7 markus 148: char *cp;
149:
150: /* Skip leading whitespace. */
1.9 markus 151: for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++)
152: ;
1.1 deraadt 153:
1.21 markus 154: if (key_read(ret, &cp) != 1)
1.7 markus 155: return 0;
156:
157: /* Skip trailing whitespace. */
1.9 markus 158: for (; *cp == ' ' || *cp == '\t'; cp++)
159: ;
1.7 markus 160:
161: /* Return results. */
162: *cpp = cp;
1.21 markus 163: *bitsp = key_size(ret);
1.7 markus 164: return 1;
1.14 markus 165: }
1.1 deraadt 166:
1.27 itojun 167: static int
1.32 jakob 168: hostfile_check_key(int bits, const Key *key, const char *host, const char *filename, int linenum)
1.1 deraadt 169: {
1.21 markus 170: if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL)
1.14 markus 171: return 1;
172: if (bits != BN_num_bits(key->rsa->n)) {
1.31 itojun 173: logit("Warning: %s, line %d: keysize mismatch for host %s: "
1.14 markus 174: "actual %d vs. announced %d.",
175: filename, linenum, host, BN_num_bits(key->rsa->n), bits);
1.31 itojun 176: logit("Warning: replace %d with %d in %s, line %d.",
1.14 markus 177: bits, BN_num_bits(key->rsa->n), filename, linenum);
1.1 deraadt 178: }
1.14 markus 179: return 1;
1.1 deraadt 180: }
181:
1.9 markus 182: /*
183: * Checks whether the given host (which must be in all lowercase) is already
184: * in the list of our known hosts. Returns HOST_OK if the host is known and
185: * has the specified key, HOST_NEW if the host is not known, and HOST_CHANGED
186: * if the host is known but used to have a different host key.
1.30 markus 187: *
188: * If no 'key' has been specified and a key of type 'keytype' is known
189: * for the specified host, then HOST_FOUND is returned.
1.9 markus 190: */
1.1 deraadt 191:
1.30 markus 192: static HostStatus
193: check_host_in_hostfile_by_key_or_type(const char *filename,
1.32 jakob 194: const char *host, const Key *key, int keytype, Key *found, int *numret)
1.1 deraadt 195: {
1.7 markus 196: FILE *f;
197: char line[8192];
198: int linenum = 0;
1.25 stevesk 199: u_int kbits;
1.33 djm 200: char *cp, *cp2, *hashed_host;
1.7 markus 201: HostStatus end_return;
202:
1.26 markus 203: debug3("check_host_in_hostfile: filename %s", filename);
1.30 markus 204:
1.7 markus 205: /* Open the file containing the list of known hosts. */
206: f = fopen(filename, "r");
207: if (!f)
208: return HOST_NEW;
209:
1.9 markus 210: /*
211: * Return value when the loop terminates. This is set to
212: * HOST_CHANGED if we have seen a different key for the host and have
213: * not found the proper one.
214: */
1.7 markus 215: end_return = HOST_NEW;
216:
1.25 stevesk 217: /* Go through the file. */
1.7 markus 218: while (fgets(line, sizeof(line), f)) {
219: cp = line;
220: linenum++;
221:
1.9 markus 222: /* Skip any leading whitespace, comments and empty lines. */
223: for (; *cp == ' ' || *cp == '\t'; cp++)
224: ;
1.7 markus 225: if (!*cp || *cp == '#' || *cp == '\n')
226: continue;
227:
228: /* Find the end of the host name portion. */
1.9 markus 229: for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++)
230: ;
1.7 markus 231:
232: /* Check if the host name matches. */
1.33 djm 233: if (match_hostname(host, cp, (u_int) (cp2 - cp)) != 1) {
234: if (*cp != HASH_DELIM)
235: continue;
236: hashed_host = host_hash(host, cp, (u_int) (cp2 - cp));
237: if (hashed_host == NULL) {
238: debug("Invalid hashed host line %d of %s",
239: linenum, filename);
240: continue;
241: }
242: if (strncmp(hashed_host, cp, (u_int) (cp2 - cp)) != 0)
243: continue;
244: }
1.7 markus 245:
246: /* Got a match. Skip host name. */
247: cp = cp2;
248:
1.9 markus 249: /*
250: * Extract the key from the line. This will skip any leading
251: * whitespace. Ignore badly formatted lines.
252: */
1.14 markus 253: if (!hostfile_read_key(&cp, &kbits, found))
254: continue;
1.23 markus 255:
256: if (numret != NULL)
257: *numret = linenum;
1.7 markus 258:
1.30 markus 259: if (key == NULL) {
260: /* we found a key of the requested type */
1.38 djm 261: if (found->type == keytype) {
262: fclose(f);
1.30 markus 263: return HOST_FOUND;
1.38 djm 264: }
1.30 markus 265: continue;
266: }
267:
268: if (!hostfile_check_key(kbits, found, host, filename, linenum))
269: continue;
270:
1.7 markus 271: /* Check if the current key is the same as the given key. */
1.14 markus 272: if (key_equal(key, found)) {
1.7 markus 273: /* Ok, they match. */
1.26 markus 274: debug3("check_host_in_hostfile: match line %d", linenum);
1.7 markus 275: fclose(f);
276: return HOST_OK;
277: }
1.9 markus 278: /*
279: * They do not match. We will continue to go through the
280: * file; however, we note that we will not return that it is
281: * new.
282: */
1.7 markus 283: end_return = HOST_CHANGED;
1.1 deraadt 284: }
1.7 markus 285: /* Clear variables and close the file. */
286: fclose(f);
287:
1.9 markus 288: /*
289: * Return either HOST_NEW or HOST_CHANGED, depending on whether we
290: * saw a different key for the host.
291: */
1.7 markus 292: return end_return;
1.30 markus 293: }
294:
295: HostStatus
1.32 jakob 296: check_host_in_hostfile(const char *filename, const char *host, const Key *key,
1.30 markus 297: Key *found, int *numret)
298: {
299: if (key == NULL)
300: fatal("no key to look up");
301: return (check_host_in_hostfile_by_key_or_type(filename, host, key, 0,
302: found, numret));
303: }
304:
305: int
306: lookup_key_in_hostfile_by_type(const char *filename, const char *host,
307: int keytype, Key *found, int *numret)
308: {
309: return (check_host_in_hostfile_by_key_or_type(filename, host, NULL,
310: keytype, found, numret) == HOST_FOUND);
1.1 deraadt 311: }
312:
1.9 markus 313: /*
314: * Appends an entry to the host file. Returns false if the entry could not
315: * be appended.
316: */
1.1 deraadt 317:
1.2 provos 318: int
1.34 deraadt 319: add_host_to_hostfile(const char *filename, const char *host, const Key *key,
1.33 djm 320: int store_hash)
1.1 deraadt 321: {
1.7 markus 322: FILE *f;
1.14 markus 323: int success = 0;
1.35 dtucker 324: char *hashed_host = NULL;
1.33 djm 325:
1.14 markus 326: if (key == NULL)
1.17 markus 327: return 1; /* XXX ? */
1.7 markus 328: f = fopen(filename, "a");
329: if (!f)
330: return 0;
1.33 djm 331:
332: if (store_hash) {
333: if ((hashed_host = host_hash(host, NULL, 0)) == NULL) {
334: error("add_host_to_hostfile: host_hash failed");
335: fclose(f);
336: return 0;
337: }
338: }
339: fprintf(f, "%s ", store_hash ? hashed_host : host);
340:
1.14 markus 341: if (key_write(key, f)) {
342: success = 1;
343: } else {
1.17 markus 344: error("add_host_to_hostfile: saving key in %s failed", filename);
1.7 markus 345: }
1.17 markus 346: fprintf(f, "\n");
1.7 markus 347: fclose(f);
1.14 markus 348: return success;
1.1 deraadt 349: }
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