Annotation of src/usr.bin/ssh/dh.c, Revision 1.2.4.3
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"
1.2.4.3 ! jason 26: RCSID("$OpenBSD: dh.c,v 1.8 2001/03/05 17:58:22 stevesk 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 "buffer.h"
1.2.4.2 jason 35: #include "cipher.h"
1.1 provos 36: #include "kex.h"
37: #include "dh.h"
1.2.4.2 jason 38: #include "pathnames.h"
39: #include "log.h"
40: #include "misc.h"
1.1 provos 41:
42: int
43: parse_prime(int linenum, char *line, struct dhgroup *dhg)
44: {
45: char *cp, *arg;
46: char *strsize, *gen, *prime;
47:
48: cp = line;
49: arg = strdelim(&cp);
50: /* Ignore leading whitespace */
51: if (*arg == '\0')
52: arg = strdelim(&cp);
53: if (!*arg || *arg == '#')
54: return 0;
55:
56: /* time */
57: if (cp == NULL || *arg == '\0')
58: goto fail;
59: arg = strsep(&cp, " "); /* type */
60: if (cp == NULL || *arg == '\0')
61: goto fail;
62: arg = strsep(&cp, " "); /* tests */
63: if (cp == NULL || *arg == '\0')
64: goto fail;
65: arg = strsep(&cp, " "); /* tries */
66: if (cp == NULL || *arg == '\0')
67: goto fail;
68: strsize = strsep(&cp, " "); /* size */
69: if (cp == NULL || *strsize == '\0' ||
70: (dhg->size = atoi(strsize)) == 0)
71: goto fail;
72: gen = strsep(&cp, " "); /* gen */
73: if (cp == NULL || *gen == '\0')
74: goto fail;
75: prime = strsep(&cp, " "); /* prime */
76: if (cp != NULL || *prime == '\0')
77: goto fail;
78:
79: dhg->g = BN_new();
80: if (BN_hex2bn(&dhg->g, gen) < 0) {
81: BN_free(dhg->g);
82: goto fail;
83: }
84: dhg->p = BN_new();
85: if (BN_hex2bn(&dhg->p, prime) < 0) {
86: BN_free(dhg->g);
87: BN_free(dhg->p);
88: goto fail;
89: }
90:
91: return (1);
92: fail:
1.2.4.3 ! jason 93: error("Bad prime description in line %d", linenum);
1.1 provos 94: return (0);
95: }
96:
97: DH *
98: choose_dh(int minbits)
99: {
100: FILE *f;
101: char line[1024];
102: int best, bestcount, which;
103: int linenum;
104: struct dhgroup dhg;
105:
1.2.4.2 jason 106: f = fopen(_PATH_DH_PRIMES, "r");
1.1 provos 107: if (!f) {
1.2.4.2 jason 108: log("WARNING: %s does not exist, using old prime", _PATH_DH_PRIMES);
1.1 provos 109: return (dh_new_group1());
110: }
111:
112: linenum = 0;
113: best = bestcount = 0;
114: while (fgets(line, sizeof(line), f)) {
115: linenum++;
116: if (!parse_prime(linenum, line, &dhg))
117: continue;
118: BN_free(dhg.g);
119: BN_free(dhg.p);
120:
121: if ((dhg.size > minbits && dhg.size < best) ||
122: (dhg.size > best && best < minbits)) {
123: best = dhg.size;
124: bestcount = 0;
125: }
126: if (dhg.size == best)
127: bestcount++;
128: }
129: fclose (f);
130:
131: if (bestcount == 0) {
1.2.4.2 jason 132: log("WARNING: no primes in %s, using old prime", _PATH_DH_PRIMES);
1.1 provos 133: return (dh_new_group1());
134: }
135:
1.2.4.2 jason 136: f = fopen(_PATH_DH_PRIMES, "r");
1.1 provos 137: if (!f) {
1.2.4.3 ! jason 138: fatal("WARNING: %s disappeared, giving up", _PATH_DH_PRIMES);
1.1 provos 139: }
140:
141: linenum = 0;
142: which = arc4random() % bestcount;
143: while (fgets(line, sizeof(line), f)) {
144: if (!parse_prime(linenum, line, &dhg))
145: continue;
146: if (dhg.size != best)
147: continue;
148: if (linenum++ != which) {
149: BN_free(dhg.g);
150: BN_free(dhg.p);
151: continue;
152: }
153: break;
154: }
155: fclose(f);
156:
157: return (dh_new_group(dhg.g, dhg.p));
158: }
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