Annotation of src/usr.bin/ssh/hostfile.c, Revision 1.43
1.43 ! stevesk 1: /* $OpenBSD: hostfile.c,v 1.42 2006/07/22 20:48:23 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>
1.43 ! stevesk 49: #include <stdlib.h>
1.42 stevesk 50: #include <string.h>
1.1 deraadt 51:
1.14 markus 52: #include "match.h"
53: #include "key.h"
54: #include "hostfile.h"
1.24 markus 55: #include "log.h"
1.33 djm 56: #include "xmalloc.h"
57:
58: static int
59: extract_salt(const char *s, u_int l, char *salt, size_t salt_len)
60: {
61: char *p, *b64salt;
62: u_int b64len;
63: int ret;
64:
65: if (l < sizeof(HASH_MAGIC) - 1) {
66: debug2("extract_salt: string too short");
67: return (-1);
68: }
69: if (strncmp(s, HASH_MAGIC, sizeof(HASH_MAGIC) - 1) != 0) {
70: debug2("extract_salt: invalid magic identifier");
71: return (-1);
72: }
73: s += sizeof(HASH_MAGIC) - 1;
74: l -= sizeof(HASH_MAGIC) - 1;
75: if ((p = memchr(s, HASH_DELIM, l)) == NULL) {
76: debug2("extract_salt: missing salt termination character");
77: return (-1);
78: }
79:
80: b64len = p - s;
81: /* Sanity check */
82: if (b64len == 0 || b64len > 1024) {
83: debug2("extract_salt: bad encoded salt length %u", b64len);
84: return (-1);
85: }
86: b64salt = xmalloc(1 + b64len);
87: memcpy(b64salt, s, b64len);
88: b64salt[b64len] = '\0';
89:
90: ret = __b64_pton(b64salt, salt, salt_len);
91: xfree(b64salt);
92: if (ret == -1) {
93: debug2("extract_salt: salt decode error");
94: return (-1);
95: }
96: if (ret != SHA_DIGEST_LENGTH) {
1.36 dtucker 97: debug2("extract_salt: expected salt len %d, got %d",
98: SHA_DIGEST_LENGTH, ret);
1.33 djm 99: return (-1);
100: }
1.34 deraadt 101:
1.33 djm 102: return (0);
103: }
104:
105: char *
106: host_hash(const char *host, const char *name_from_hostfile, u_int src_len)
107: {
108: const EVP_MD *md = EVP_sha1();
109: HMAC_CTX mac_ctx;
110: char salt[256], result[256], uu_salt[512], uu_result[512];
111: static char encoded[1024];
112: u_int i, len;
113:
114: len = EVP_MD_size(md);
115:
116: if (name_from_hostfile == NULL) {
117: /* Create new salt */
118: for (i = 0; i < len; i++)
119: salt[i] = arc4random();
120: } else {
121: /* Extract salt from known host entry */
122: if (extract_salt(name_from_hostfile, src_len, salt,
123: sizeof(salt)) == -1)
124: return (NULL);
125: }
126:
127: HMAC_Init(&mac_ctx, salt, len, md);
128: HMAC_Update(&mac_ctx, host, strlen(host));
129: HMAC_Final(&mac_ctx, result, NULL);
130: HMAC_cleanup(&mac_ctx);
131:
1.34 deraadt 132: if (__b64_ntop(salt, len, uu_salt, sizeof(uu_salt)) == -1 ||
1.33 djm 133: __b64_ntop(result, len, uu_result, sizeof(uu_result)) == -1)
134: fatal("host_hash: __b64_ntop failed");
135:
136: snprintf(encoded, sizeof(encoded), "%s%s%c%s", HASH_MAGIC, uu_salt,
137: HASH_DELIM, uu_result);
138:
139: return (encoded);
140: }
1.1 deraadt 141:
1.9 markus 142: /*
1.14 markus 143: * Parses an RSA (number of bits, e, n) or DSA key from a string. Moves the
144: * pointer over the key. Skips any whitespace at the beginning and at end.
1.9 markus 145: */
1.1 deraadt 146:
1.29 jakob 147: int
1.22 markus 148: hostfile_read_key(char **cpp, u_int *bitsp, Key *ret)
1.1 deraadt 149: {
1.7 markus 150: char *cp;
151:
152: /* Skip leading whitespace. */
1.9 markus 153: for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++)
154: ;
1.1 deraadt 155:
1.21 markus 156: if (key_read(ret, &cp) != 1)
1.7 markus 157: return 0;
158:
159: /* Skip trailing whitespace. */
1.9 markus 160: for (; *cp == ' ' || *cp == '\t'; cp++)
161: ;
1.7 markus 162:
163: /* Return results. */
164: *cpp = cp;
1.21 markus 165: *bitsp = key_size(ret);
1.7 markus 166: return 1;
1.14 markus 167: }
1.1 deraadt 168:
1.27 itojun 169: static int
1.32 jakob 170: hostfile_check_key(int bits, const Key *key, const char *host, const char *filename, int linenum)
1.1 deraadt 171: {
1.21 markus 172: if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL)
1.14 markus 173: return 1;
174: if (bits != BN_num_bits(key->rsa->n)) {
1.31 itojun 175: logit("Warning: %s, line %d: keysize mismatch for host %s: "
1.14 markus 176: "actual %d vs. announced %d.",
177: filename, linenum, host, BN_num_bits(key->rsa->n), bits);
1.31 itojun 178: logit("Warning: replace %d with %d in %s, line %d.",
1.14 markus 179: bits, BN_num_bits(key->rsa->n), filename, linenum);
1.1 deraadt 180: }
1.14 markus 181: return 1;
1.1 deraadt 182: }
183:
1.9 markus 184: /*
185: * Checks whether the given host (which must be in all lowercase) is already
186: * in the list of our known hosts. Returns HOST_OK if the host is known and
187: * has the specified key, HOST_NEW if the host is not known, and HOST_CHANGED
188: * if the host is known but used to have a different host key.
1.30 markus 189: *
190: * If no 'key' has been specified and a key of type 'keytype' is known
191: * for the specified host, then HOST_FOUND is returned.
1.9 markus 192: */
1.1 deraadt 193:
1.30 markus 194: static HostStatus
195: check_host_in_hostfile_by_key_or_type(const char *filename,
1.32 jakob 196: const char *host, const Key *key, int keytype, Key *found, int *numret)
1.1 deraadt 197: {
1.7 markus 198: FILE *f;
199: char line[8192];
200: int linenum = 0;
1.25 stevesk 201: u_int kbits;
1.33 djm 202: char *cp, *cp2, *hashed_host;
1.7 markus 203: HostStatus end_return;
204:
1.26 markus 205: debug3("check_host_in_hostfile: filename %s", filename);
1.30 markus 206:
1.7 markus 207: /* Open the file containing the list of known hosts. */
208: f = fopen(filename, "r");
209: if (!f)
210: return HOST_NEW;
211:
1.9 markus 212: /*
213: * Return value when the loop terminates. This is set to
214: * HOST_CHANGED if we have seen a different key for the host and have
215: * not found the proper one.
216: */
1.7 markus 217: end_return = HOST_NEW;
218:
1.25 stevesk 219: /* Go through the file. */
1.7 markus 220: while (fgets(line, sizeof(line), f)) {
221: cp = line;
222: linenum++;
223:
1.9 markus 224: /* Skip any leading whitespace, comments and empty lines. */
225: for (; *cp == ' ' || *cp == '\t'; cp++)
226: ;
1.7 markus 227: if (!*cp || *cp == '#' || *cp == '\n')
228: continue;
229:
230: /* Find the end of the host name portion. */
1.9 markus 231: for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++)
232: ;
1.7 markus 233:
234: /* Check if the host name matches. */
1.33 djm 235: if (match_hostname(host, cp, (u_int) (cp2 - cp)) != 1) {
236: if (*cp != HASH_DELIM)
237: continue;
238: hashed_host = host_hash(host, cp, (u_int) (cp2 - cp));
239: if (hashed_host == NULL) {
240: debug("Invalid hashed host line %d of %s",
241: linenum, filename);
242: continue;
243: }
244: if (strncmp(hashed_host, cp, (u_int) (cp2 - cp)) != 0)
245: continue;
246: }
1.7 markus 247:
248: /* Got a match. Skip host name. */
249: cp = cp2;
250:
1.9 markus 251: /*
252: * Extract the key from the line. This will skip any leading
253: * whitespace. Ignore badly formatted lines.
254: */
1.14 markus 255: if (!hostfile_read_key(&cp, &kbits, found))
256: continue;
1.23 markus 257:
258: if (numret != NULL)
259: *numret = linenum;
1.7 markus 260:
1.30 markus 261: if (key == NULL) {
262: /* we found a key of the requested type */
1.38 djm 263: if (found->type == keytype) {
264: fclose(f);
1.30 markus 265: return HOST_FOUND;
1.38 djm 266: }
1.30 markus 267: continue;
268: }
269:
270: if (!hostfile_check_key(kbits, found, host, filename, linenum))
271: continue;
272:
1.7 markus 273: /* Check if the current key is the same as the given key. */
1.14 markus 274: if (key_equal(key, found)) {
1.7 markus 275: /* Ok, they match. */
1.26 markus 276: debug3("check_host_in_hostfile: match line %d", linenum);
1.7 markus 277: fclose(f);
278: return HOST_OK;
279: }
1.9 markus 280: /*
281: * They do not match. We will continue to go through the
282: * file; however, we note that we will not return that it is
283: * new.
284: */
1.7 markus 285: end_return = HOST_CHANGED;
1.1 deraadt 286: }
1.7 markus 287: /* Clear variables and close the file. */
288: fclose(f);
289:
1.9 markus 290: /*
291: * Return either HOST_NEW or HOST_CHANGED, depending on whether we
292: * saw a different key for the host.
293: */
1.7 markus 294: return end_return;
1.30 markus 295: }
296:
297: HostStatus
1.32 jakob 298: check_host_in_hostfile(const char *filename, const char *host, const Key *key,
1.30 markus 299: Key *found, int *numret)
300: {
301: if (key == NULL)
302: fatal("no key to look up");
303: return (check_host_in_hostfile_by_key_or_type(filename, host, key, 0,
304: found, numret));
305: }
306:
307: int
308: lookup_key_in_hostfile_by_type(const char *filename, const char *host,
309: int keytype, Key *found, int *numret)
310: {
311: return (check_host_in_hostfile_by_key_or_type(filename, host, NULL,
312: keytype, found, numret) == HOST_FOUND);
1.1 deraadt 313: }
314:
1.9 markus 315: /*
316: * Appends an entry to the host file. Returns false if the entry could not
317: * be appended.
318: */
1.1 deraadt 319:
1.2 provos 320: int
1.34 deraadt 321: add_host_to_hostfile(const char *filename, const char *host, const Key *key,
1.33 djm 322: int store_hash)
1.1 deraadt 323: {
1.7 markus 324: FILE *f;
1.14 markus 325: int success = 0;
1.35 dtucker 326: char *hashed_host = NULL;
1.33 djm 327:
1.14 markus 328: if (key == NULL)
1.17 markus 329: return 1; /* XXX ? */
1.7 markus 330: f = fopen(filename, "a");
331: if (!f)
332: return 0;
1.33 djm 333:
334: if (store_hash) {
335: if ((hashed_host = host_hash(host, NULL, 0)) == NULL) {
336: error("add_host_to_hostfile: host_hash failed");
337: fclose(f);
338: return 0;
339: }
340: }
341: fprintf(f, "%s ", store_hash ? hashed_host : host);
342:
1.14 markus 343: if (key_write(key, f)) {
344: success = 1;
345: } else {
1.17 markus 346: error("add_host_to_hostfile: saving key in %s failed", filename);
1.7 markus 347: }
1.17 markus 348: fprintf(f, "\n");
1.7 markus 349: fclose(f);
1.14 markus 350: return success;
1.1 deraadt 351: }
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