Annotation of src/usr.bin/ssh/hostfile.c, Revision 1.39
1.1 deraadt 1: /*
1.8 deraadt 2: * Author: Tatu Ylonen <ylo@cs.hut.fi>
3: * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
4: * All rights reserved
5: * Functions for manipulating the known hosts files.
1.16 markus 6: *
1.20 deraadt 7: * As far as I am concerned, the code I have written for this software
8: * can be used freely for any purpose. Any derived versions of this
9: * software must be clearly marked as such, and if the derived work is
10: * incompatible with the protocol description in the RFC file, it must be
11: * called by a name other than "ssh" or "Secure Shell".
12: *
13: *
1.28 markus 14: * Copyright (c) 1999, 2000 Markus Friedl. All rights reserved.
1.20 deraadt 15: * Copyright (c) 1999 Niels Provos. All rights reserved.
16: *
17: * Redistribution and use in source and binary forms, with or without
18: * modification, are permitted provided that the following conditions
19: * are met:
20: * 1. Redistributions of source code must retain the above copyright
21: * notice, this list of conditions and the following disclaimer.
22: * 2. Redistributions in binary form must reproduce the above copyright
23: * notice, this list of conditions and the following disclaimer in the
24: * documentation and/or other materials provided with the distribution.
25: *
26: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
27: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
28: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
29: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
30: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
31: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
32: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
33: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
34: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
35: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
1.8 deraadt 36: */
1.1 deraadt 37:
38: #include "includes.h"
1.33 djm 39:
40: #include <resolv.h>
1.37 stevesk 41:
1.33 djm 42: #include <openssl/hmac.h>
43: #include <openssl/sha.h>
1.1 deraadt 44:
1.14 markus 45: #include "match.h"
46: #include "key.h"
47: #include "hostfile.h"
1.24 markus 48: #include "log.h"
1.33 djm 49: #include "xmalloc.h"
50:
51: static int
52: extract_salt(const char *s, u_int l, char *salt, size_t salt_len)
53: {
54: char *p, *b64salt;
55: u_int b64len;
56: int ret;
57:
58: if (l < sizeof(HASH_MAGIC) - 1) {
59: debug2("extract_salt: string too short");
60: return (-1);
61: }
62: if (strncmp(s, HASH_MAGIC, sizeof(HASH_MAGIC) - 1) != 0) {
63: debug2("extract_salt: invalid magic identifier");
64: return (-1);
65: }
66: s += sizeof(HASH_MAGIC) - 1;
67: l -= sizeof(HASH_MAGIC) - 1;
68: if ((p = memchr(s, HASH_DELIM, l)) == NULL) {
69: debug2("extract_salt: missing salt termination character");
70: return (-1);
71: }
72:
73: b64len = p - s;
74: /* Sanity check */
75: if (b64len == 0 || b64len > 1024) {
76: debug2("extract_salt: bad encoded salt length %u", b64len);
77: return (-1);
78: }
79: b64salt = xmalloc(1 + b64len);
80: memcpy(b64salt, s, b64len);
81: b64salt[b64len] = '\0';
82:
83: ret = __b64_pton(b64salt, salt, salt_len);
84: xfree(b64salt);
85: if (ret == -1) {
86: debug2("extract_salt: salt decode error");
87: return (-1);
88: }
89: if (ret != SHA_DIGEST_LENGTH) {
1.36 dtucker 90: debug2("extract_salt: expected salt len %d, got %d",
91: SHA_DIGEST_LENGTH, ret);
1.33 djm 92: return (-1);
93: }
1.34 deraadt 94:
1.33 djm 95: return (0);
96: }
97:
98: char *
99: host_hash(const char *host, const char *name_from_hostfile, u_int src_len)
100: {
101: const EVP_MD *md = EVP_sha1();
102: HMAC_CTX mac_ctx;
103: char salt[256], result[256], uu_salt[512], uu_result[512];
104: static char encoded[1024];
105: u_int i, len;
106:
107: len = EVP_MD_size(md);
108:
109: if (name_from_hostfile == NULL) {
110: /* Create new salt */
111: for (i = 0; i < len; i++)
112: salt[i] = arc4random();
113: } else {
114: /* Extract salt from known host entry */
115: if (extract_salt(name_from_hostfile, src_len, salt,
116: sizeof(salt)) == -1)
117: return (NULL);
118: }
119:
120: HMAC_Init(&mac_ctx, salt, len, md);
121: HMAC_Update(&mac_ctx, host, strlen(host));
122: HMAC_Final(&mac_ctx, result, NULL);
123: HMAC_cleanup(&mac_ctx);
124:
1.34 deraadt 125: if (__b64_ntop(salt, len, uu_salt, sizeof(uu_salt)) == -1 ||
1.33 djm 126: __b64_ntop(result, len, uu_result, sizeof(uu_result)) == -1)
127: fatal("host_hash: __b64_ntop failed");
128:
129: snprintf(encoded, sizeof(encoded), "%s%s%c%s", HASH_MAGIC, uu_salt,
130: HASH_DELIM, uu_result);
131:
132: return (encoded);
133: }
1.1 deraadt 134:
1.9 markus 135: /*
1.14 markus 136: * Parses an RSA (number of bits, e, n) or DSA key from a string. Moves the
137: * pointer over the key. Skips any whitespace at the beginning and at end.
1.9 markus 138: */
1.1 deraadt 139:
1.29 jakob 140: int
1.22 markus 141: hostfile_read_key(char **cpp, u_int *bitsp, Key *ret)
1.1 deraadt 142: {
1.7 markus 143: char *cp;
144:
145: /* Skip leading whitespace. */
1.9 markus 146: for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++)
147: ;
1.1 deraadt 148:
1.21 markus 149: if (key_read(ret, &cp) != 1)
1.7 markus 150: return 0;
151:
152: /* Skip trailing whitespace. */
1.9 markus 153: for (; *cp == ' ' || *cp == '\t'; cp++)
154: ;
1.7 markus 155:
156: /* Return results. */
157: *cpp = cp;
1.21 markus 158: *bitsp = key_size(ret);
1.7 markus 159: return 1;
1.14 markus 160: }
1.1 deraadt 161:
1.27 itojun 162: static int
1.32 jakob 163: hostfile_check_key(int bits, const Key *key, const char *host, const char *filename, int linenum)
1.1 deraadt 164: {
1.21 markus 165: if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL)
1.14 markus 166: return 1;
167: if (bits != BN_num_bits(key->rsa->n)) {
1.31 itojun 168: logit("Warning: %s, line %d: keysize mismatch for host %s: "
1.14 markus 169: "actual %d vs. announced %d.",
170: filename, linenum, host, BN_num_bits(key->rsa->n), bits);
1.31 itojun 171: logit("Warning: replace %d with %d in %s, line %d.",
1.14 markus 172: bits, BN_num_bits(key->rsa->n), filename, linenum);
1.1 deraadt 173: }
1.14 markus 174: return 1;
1.1 deraadt 175: }
176:
1.9 markus 177: /*
178: * Checks whether the given host (which must be in all lowercase) is already
179: * in the list of our known hosts. Returns HOST_OK if the host is known and
180: * has the specified key, HOST_NEW if the host is not known, and HOST_CHANGED
181: * if the host is known but used to have a different host key.
1.30 markus 182: *
183: * If no 'key' has been specified and a key of type 'keytype' is known
184: * for the specified host, then HOST_FOUND is returned.
1.9 markus 185: */
1.1 deraadt 186:
1.30 markus 187: static HostStatus
188: check_host_in_hostfile_by_key_or_type(const char *filename,
1.32 jakob 189: const char *host, const Key *key, int keytype, Key *found, int *numret)
1.1 deraadt 190: {
1.7 markus 191: FILE *f;
192: char line[8192];
193: int linenum = 0;
1.25 stevesk 194: u_int kbits;
1.33 djm 195: char *cp, *cp2, *hashed_host;
1.7 markus 196: HostStatus end_return;
197:
1.26 markus 198: debug3("check_host_in_hostfile: filename %s", filename);
1.30 markus 199:
1.7 markus 200: /* Open the file containing the list of known hosts. */
201: f = fopen(filename, "r");
202: if (!f)
203: return HOST_NEW;
204:
1.9 markus 205: /*
206: * Return value when the loop terminates. This is set to
207: * HOST_CHANGED if we have seen a different key for the host and have
208: * not found the proper one.
209: */
1.7 markus 210: end_return = HOST_NEW;
211:
1.25 stevesk 212: /* Go through the file. */
1.7 markus 213: while (fgets(line, sizeof(line), f)) {
214: cp = line;
215: linenum++;
216:
1.9 markus 217: /* Skip any leading whitespace, comments and empty lines. */
218: for (; *cp == ' ' || *cp == '\t'; cp++)
219: ;
1.7 markus 220: if (!*cp || *cp == '#' || *cp == '\n')
221: continue;
222:
223: /* Find the end of the host name portion. */
1.9 markus 224: for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++)
225: ;
1.7 markus 226:
227: /* Check if the host name matches. */
1.33 djm 228: if (match_hostname(host, cp, (u_int) (cp2 - cp)) != 1) {
229: if (*cp != HASH_DELIM)
230: continue;
231: hashed_host = host_hash(host, cp, (u_int) (cp2 - cp));
232: if (hashed_host == NULL) {
233: debug("Invalid hashed host line %d of %s",
234: linenum, filename);
235: continue;
236: }
237: if (strncmp(hashed_host, cp, (u_int) (cp2 - cp)) != 0)
238: continue;
239: }
1.7 markus 240:
241: /* Got a match. Skip host name. */
242: cp = cp2;
243:
1.9 markus 244: /*
245: * Extract the key from the line. This will skip any leading
246: * whitespace. Ignore badly formatted lines.
247: */
1.14 markus 248: if (!hostfile_read_key(&cp, &kbits, found))
249: continue;
1.23 markus 250:
251: if (numret != NULL)
252: *numret = linenum;
1.7 markus 253:
1.30 markus 254: if (key == NULL) {
255: /* we found a key of the requested type */
1.38 djm 256: if (found->type == keytype) {
257: fclose(f);
1.30 markus 258: return HOST_FOUND;
1.38 djm 259: }
1.30 markus 260: continue;
261: }
262:
263: if (!hostfile_check_key(kbits, found, host, filename, linenum))
264: continue;
265:
1.7 markus 266: /* Check if the current key is the same as the given key. */
1.14 markus 267: if (key_equal(key, found)) {
1.7 markus 268: /* Ok, they match. */
1.26 markus 269: debug3("check_host_in_hostfile: match line %d", linenum);
1.7 markus 270: fclose(f);
271: return HOST_OK;
272: }
1.9 markus 273: /*
274: * They do not match. We will continue to go through the
275: * file; however, we note that we will not return that it is
276: * new.
277: */
1.7 markus 278: end_return = HOST_CHANGED;
1.1 deraadt 279: }
1.7 markus 280: /* Clear variables and close the file. */
281: fclose(f);
282:
1.9 markus 283: /*
284: * Return either HOST_NEW or HOST_CHANGED, depending on whether we
285: * saw a different key for the host.
286: */
1.7 markus 287: return end_return;
1.30 markus 288: }
289:
290: HostStatus
1.32 jakob 291: check_host_in_hostfile(const char *filename, const char *host, const Key *key,
1.30 markus 292: Key *found, int *numret)
293: {
294: if (key == NULL)
295: fatal("no key to look up");
296: return (check_host_in_hostfile_by_key_or_type(filename, host, key, 0,
297: found, numret));
298: }
299:
300: int
301: lookup_key_in_hostfile_by_type(const char *filename, const char *host,
302: int keytype, Key *found, int *numret)
303: {
304: return (check_host_in_hostfile_by_key_or_type(filename, host, NULL,
305: keytype, found, numret) == HOST_FOUND);
1.1 deraadt 306: }
307:
1.9 markus 308: /*
309: * Appends an entry to the host file. Returns false if the entry could not
310: * be appended.
311: */
1.1 deraadt 312:
1.2 provos 313: int
1.34 deraadt 314: add_host_to_hostfile(const char *filename, const char *host, const Key *key,
1.33 djm 315: int store_hash)
1.1 deraadt 316: {
1.7 markus 317: FILE *f;
1.14 markus 318: int success = 0;
1.35 dtucker 319: char *hashed_host = NULL;
1.33 djm 320:
1.14 markus 321: if (key == NULL)
1.17 markus 322: return 1; /* XXX ? */
1.7 markus 323: f = fopen(filename, "a");
324: if (!f)
325: return 0;
1.33 djm 326:
327: if (store_hash) {
328: if ((hashed_host = host_hash(host, NULL, 0)) == NULL) {
329: error("add_host_to_hostfile: host_hash failed");
330: fclose(f);
331: return 0;
332: }
333: }
334: fprintf(f, "%s ", store_hash ? hashed_host : host);
335:
1.14 markus 336: if (key_write(key, f)) {
337: success = 1;
338: } else {
1.17 markus 339: error("add_host_to_hostfile: saving key in %s failed", filename);
1.7 markus 340: }
1.17 markus 341: fprintf(f, "\n");
1.7 markus 342: fclose(f);
1.14 markus 343: return success;
1.1 deraadt 344: }
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