Annotation of src/usr.bin/ssh/dh.c, Revision 1.3
1.1 provos 1: /*
2: * Copyright (c) 2000 Niels Provos. All rights reserved.
3: *
4: * Redistribution and use in source and binary forms, with or without
5: * modification, are permitted provided that the following conditions
6: * are met:
7: * 1. Redistributions of source code must retain the above copyright
8: * notice, this list of conditions and the following disclaimer.
9: * 2. Redistributions in binary form must reproduce the above copyright
10: * notice, this list of conditions and the following disclaimer in the
11: * documentation and/or other materials provided with the distribution.
12: *
13: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
14: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
15: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
16: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
17: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
18: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
19: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
20: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
22: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
23: */
24:
25: #include "includes.h"
1.3 ! markus 26: RCSID("$OpenBSD: dh.c,v 1.2 2000/10/11 20:11:35 markus Exp $");
1.1 provos 27:
28: #include "xmalloc.h"
29:
30: #include <openssl/bn.h>
31: #include <openssl/dh.h>
32: #include <openssl/evp.h>
33:
34: #include "ssh.h"
35: #include "buffer.h"
36: #include "kex.h"
37: #include "dh.h"
38:
39: int
40: parse_prime(int linenum, char *line, struct dhgroup *dhg)
41: {
42: char *cp, *arg;
43: char *strsize, *gen, *prime;
44:
45: cp = line;
46: arg = strdelim(&cp);
47: /* Ignore leading whitespace */
48: if (*arg == '\0')
49: arg = strdelim(&cp);
50: if (!*arg || *arg == '#')
51: return 0;
52:
53: /* time */
54: if (cp == NULL || *arg == '\0')
55: goto fail;
56: arg = strsep(&cp, " "); /* type */
57: if (cp == NULL || *arg == '\0')
58: goto fail;
59: arg = strsep(&cp, " "); /* tests */
60: if (cp == NULL || *arg == '\0')
61: goto fail;
62: arg = strsep(&cp, " "); /* tries */
63: if (cp == NULL || *arg == '\0')
64: goto fail;
65: strsize = strsep(&cp, " "); /* size */
66: if (cp == NULL || *strsize == '\0' ||
67: (dhg->size = atoi(strsize)) == 0)
68: goto fail;
69: gen = strsep(&cp, " "); /* gen */
70: if (cp == NULL || *gen == '\0')
71: goto fail;
72: prime = strsep(&cp, " "); /* prime */
73: if (cp != NULL || *prime == '\0')
74: goto fail;
75:
76: dhg->g = BN_new();
77: if (BN_hex2bn(&dhg->g, gen) < 0) {
78: BN_free(dhg->g);
79: goto fail;
80: }
81: dhg->p = BN_new();
82: if (BN_hex2bn(&dhg->p, prime) < 0) {
83: BN_free(dhg->g);
84: BN_free(dhg->p);
85: goto fail;
86: }
87:
88: return (1);
89: fail:
90: fprintf(stderr, "Bad prime description in line %d\n", linenum);
91: return (0);
92: }
93:
94: DH *
95: choose_dh(int minbits)
96: {
97: FILE *f;
98: char line[1024];
99: int best, bestcount, which;
100: int linenum;
101: struct dhgroup dhg;
102:
103: f = fopen(DH_PRIMES, "r");
104: if (!f) {
105: log("WARNING: %s does not exist, using old prime", DH_PRIMES);
106: return (dh_new_group1());
107: }
108:
109: linenum = 0;
110: best = bestcount = 0;
111: while (fgets(line, sizeof(line), f)) {
112: linenum++;
113: if (!parse_prime(linenum, line, &dhg))
114: continue;
115: BN_free(dhg.g);
116: BN_free(dhg.p);
117:
118: if ((dhg.size > minbits && dhg.size < best) ||
119: (dhg.size > best && best < minbits)) {
120: best = dhg.size;
121: bestcount = 0;
122: }
123: if (dhg.size == best)
124: bestcount++;
125: }
126: fclose (f);
127:
128: if (bestcount == 0) {
129: log("WARNING: no primes in %s, using old prime", DH_PRIMES);
130: return (dh_new_group1());
131: }
132:
133: f = fopen(DH_PRIMES, "r");
134: if (!f) {
1.3 ! markus 135: fatal("WARNING: %s dissappeared, giving up", DH_PRIMES);
1.1 provos 136: }
137:
138: linenum = 0;
139: which = arc4random() % bestcount;
140: while (fgets(line, sizeof(line), f)) {
141: if (!parse_prime(linenum, line, &dhg))
142: continue;
143: if (dhg.size != best)
144: continue;
145: if (linenum++ != which) {
146: BN_free(dhg.g);
147: BN_free(dhg.p);
148: continue;
149: }
150: break;
151: }
152: fclose(f);
153:
154: return (dh_new_group(dhg.g, dhg.p));
155: }