Annotation of src/usr.bin/ssh/hostfile.c, Revision 1.4
1.1 deraadt 1: /*
2:
3: hostfile.c
4:
5: Author: Tatu Ylonen <ylo@cs.hut.fi>
6:
7: Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
8: All rights reserved
9:
10: Created: Thu Jun 29 07:10:56 1995 ylo
11:
12: Functions for manipulating the known hosts files.
13:
14: */
15:
16: #include "includes.h"
1.4 ! markus 17: RCSID("$Id: hostfile.c,v 1.3 1999/10/03 21:50:03 provos Exp $");
1.1 deraadt 18:
19: #include "packet.h"
20: #include "ssh.h"
21:
22: /* Reads a multiple-precision integer in hex from the buffer, and advances the
23: pointer. The integer must already be initialized. This function is
24: permitted to modify the buffer. This leaves *cpp to point just beyond
25: the last processed (and maybe modified) character. Note that this may
26: modify the buffer containing the number. */
27:
1.2 provos 28: int
29: auth_rsa_read_bignum(char **cpp, BIGNUM *value)
1.1 deraadt 30: {
31: char *cp = *cpp;
32: int len, old;
33:
34: /* Skip any leading whitespace. */
35: for (; *cp == ' ' || *cp == '\t'; cp++)
36: ;
37:
38: /* Check that it begins with a hex digit. */
39: if (*cp < '0' || *cp > '9')
40: return 0;
41:
42: /* Save starting position. */
43: *cpp = cp;
44:
45: /* Move forward until all hex digits skipped. */
46: for (; *cp >= '0' && *cp <= '9'; cp++)
47: ;
48:
49: /* Compute the length of the hex number. */
50: len = cp - *cpp;
51:
52: /* Save the old terminating character, and replace it by \0. */
53: old = *cp;
54: *cp = 0;
55:
1.2 provos 56:
1.1 deraadt 57: /* Parse the number. */
1.2 provos 58: if (BN_dec2bn(&value, *cpp) == 0)
1.1 deraadt 59: return 0;
60:
61: /* Restore old terminating character. */
62: *cp = old;
63:
64: /* Move beyond the number and return success. */
65: *cpp = cp;
66: return 1;
67: }
68:
69: /* Parses an RSA key (number of bits, e, n) from a string. Moves the pointer
70: over the key. Skips any whitespace at the beginning and at end. */
71:
1.2 provos 72: int
73: auth_rsa_read_key(char **cpp, unsigned int *bitsp, BIGNUM *e, BIGNUM *n)
1.1 deraadt 74: {
75: unsigned int bits;
76: char *cp;
77:
78: /* Skip leading whitespace. */
79: for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++)
80: ;
81:
82: /* Get number of bits. */
83: if (*cp < '0' || *cp > '9')
84: return 0; /* Bad bit count... */
85: for (bits = 0; *cp >= '0' && *cp <= '9'; cp++)
86: bits = 10 * bits + *cp - '0';
87:
88: /* Get public exponent. */
1.2 provos 89: if (!auth_rsa_read_bignum(&cp, e))
1.1 deraadt 90: return 0;
91:
92: /* Get public modulus. */
1.2 provos 93: if (!auth_rsa_read_bignum(&cp, n))
1.1 deraadt 94: return 0;
95:
96: /* Skip trailing whitespace. */
97: for (; *cp == ' ' || *cp == '\t'; cp++)
98: ;
99:
100: /* Return results. */
101: *cpp = cp;
102: *bitsp = bits;
103: return 1;
104: }
105:
106: /* Tries to match the host name (which must be in all lowercase) against the
107: comma-separated sequence of subpatterns (each possibly preceded by ! to
108: indicate negation). Returns true if there is a positive match; zero
109: otherwise. */
110:
1.2 provos 111: int
112: match_hostname(const char *host, const char *pattern, unsigned int len)
1.1 deraadt 113: {
114: char sub[1024];
115: int negated;
116: int got_positive;
117: unsigned int i, subi;
118:
119: got_positive = 0;
120: for (i = 0; i < len;)
121: {
122: /* Check if the subpattern is negated. */
123: if (pattern[i] == '!')
124: {
125: negated = 1;
126: i++;
127: }
128: else
129: negated = 0;
130:
131: /* Extract the subpattern up to a comma or end. Convert the subpattern
132: to lowercase. */
133: for (subi = 0;
134: i < len && subi < sizeof(sub) - 1 && pattern[i] != ',';
135: subi++, i++)
136: sub[subi] = isupper(pattern[i]) ? tolower(pattern[i]) : pattern[i];
137: /* If subpattern too long, return failure (no match). */
138: if (subi >= sizeof(sub) - 1)
139: return 0;
140:
141: /* If the subpattern was terminated by a comma, skip the comma. */
142: if (i < len && pattern[i] == ',')
143: i++;
144:
145: /* Null-terminate the subpattern. */
146: sub[subi] = '\0';
147:
148: /* Try to match the subpattern against the host name. */
1.2 provos 149: if (match_pattern(host, sub)) {
1.1 deraadt 150: if (negated)
151: return 0; /* Fail if host matches any negated subpattern. */
152: else
153: got_positive = 1;
1.2 provos 154: }
1.1 deraadt 155: }
156:
157: /* Return success if got a positive match. If there was a negative match,
158: we have already returned zero and never get here. */
159: return got_positive;
160: }
161:
162: /* Checks whether the given host (which must be in all lowercase) is
163: already in the list of our known hosts.
164: Returns HOST_OK if the host is known and has the specified key,
165: HOST_NEW if the host is not known, and HOST_CHANGED if the host is known
166: but used to have a different host key. */
167:
1.2 provos 168: HostStatus
169: check_host_in_hostfile(const char *filename,
170: const char *host, unsigned int bits,
1.3 provos 171: BIGNUM *e, BIGNUM *n,
172: BIGNUM *ke, BIGNUM *kn)
1.1 deraadt 173: {
174: FILE *f;
175: char line[8192];
176: unsigned int kbits, hostlen;
177: char *cp, *cp2;
178: HostStatus end_return;
179: struct stat st;
180:
181: /* Open the file containing the list of known hosts. */
182: f = fopen(filename, "r");
183: if (!f)
184: {
185: if (stat(filename, &st) >= 0)
186: {
187: packet_send_debug("Could not open %.900s for reading.", filename);
188: packet_send_debug("If your home directory is on an NFS volume, it may need to be world-readable.");
189: }
190: return HOST_NEW;
191: }
192:
193: /* Cache the length of the host name. */
194: hostlen = strlen(host);
195:
196: /* Return value when the loop terminates. This is set to HOST_CHANGED if
197: we have seen a different key for the host and have not found the proper
198: one. */
199: end_return = HOST_NEW;
200:
201: /* Go trough the file. */
202: while (fgets(line, sizeof(line), f))
203: {
204: cp = line;
205:
206: /* Skip any leading whitespace. */
207: for (; *cp == ' ' || *cp == '\t'; cp++)
208: ;
209:
210: /* Ignore comment lines and empty lines. */
211: if (!*cp || *cp == '#' || *cp == '\n')
212: continue;
213:
214: /* Find the end of the host name portion. */
215: for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++)
216: ;
217:
218: /* Check if the host name matches. */
219: if (!match_hostname(host, cp, (unsigned int)(cp2 - cp)))
220: continue;
221:
222: /* Got a match. Skip host name. */
223: cp = cp2;
224:
225: /* Extract the key from the line. This will skip any leading
226: whitespace. Ignore badly formatted lines. */
1.2 provos 227: if (!auth_rsa_read_key(&cp, &kbits, ke, kn))
1.1 deraadt 228: continue;
229:
230: /* Check if the current key is the same as the previous one. */
1.2 provos 231: if (kbits == bits && BN_cmp(ke, e) == 0 && BN_cmp(kn, n) == 0)
1.1 deraadt 232: {
233: /* Ok, they match. */
234: fclose(f);
235: return HOST_OK;
236: }
237:
238: /* They do not match. We will continue to go through the file; however,
239: we note that we will not return that it is new. */
240: end_return = HOST_CHANGED;
241: }
242: /* Clear variables and close the file. */
243: fclose(f);
244:
245: /* Return either HOST_NEW or HOST_CHANGED, depending on whether we saw a
246: different key for the host. */
247: return end_return;
248: }
249:
250: /* Appends an entry to the host file. Returns false if the entry
251: could not be appended. */
252:
1.2 provos 253: int
254: add_host_to_hostfile(const char *filename, const char *host,
255: unsigned int bits, BIGNUM *e, BIGNUM *n)
1.1 deraadt 256: {
257: FILE *f;
1.2 provos 258: char *buf;
1.1 deraadt 259:
260: /* Open the file for appending. */
261: f = fopen(filename, "a");
262: if (!f)
263: return 0;
264:
265: /* Print the host name and key to the file. */
266: fprintf(f, "%s %u ", host, bits);
1.2 provos 267: buf = BN_bn2dec(e);
1.4 ! markus 268: if (buf == NULL) {
! 269: error("add_host_to_hostfile: BN_bn2dec #1 failed");
! 270: fclose(f);
! 271: return 0;
! 272: }
1.2 provos 273: fprintf(f, "%s ", buf);
274: free (buf);
275: buf = BN_bn2dec(n);
1.4 ! markus 276: if (buf == NULL) {
! 277: error("add_host_to_hostfile: BN_bn2dec #2 failed");
! 278: fclose(f);
! 279: return 0;
! 280: }
1.2 provos 281: fprintf(f, "%s\n", buf);
282: free (buf);
1.1 deraadt 283:
284: /* Close the file. */
285: fclose(f);
286: return 1;
287: }
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