=================================================================== RCS file: /cvsrepo/anoncvs/cvs/src/usr.bin/ssh/dh.c,v retrieving revision 1.2 retrieving revision 1.2.2.6 diff -u -r1.2 -r1.2.2.6 --- src/usr.bin/ssh/dh.c 2000/10/11 20:11:35 1.2 +++ src/usr.bin/ssh/dh.c 2002/03/08 17:04:42 1.2.2.6 @@ -23,7 +23,7 @@ */ #include "includes.h" -RCSID("$OpenBSD: dh.c,v 1.2 2000/10/11 20:11:35 markus Exp $"); +RCSID("$OpenBSD: dh.c,v 1.2.2.6 2002/03/08 17:04:42 brad Exp $"); #include "xmalloc.h" @@ -31,12 +31,15 @@ #include #include -#include "ssh.h" #include "buffer.h" +#include "cipher.h" #include "kex.h" #include "dh.h" +#include "pathnames.h" +#include "log.h" +#include "misc.h" -int +static int parse_prime(int linenum, char *line, struct dhgroup *dhg) { char *cp, *arg; @@ -66,6 +69,8 @@ if (cp == NULL || *strsize == '\0' || (dhg->size = atoi(strsize)) == 0) goto fail; + /* The whole group is one bit larger */ + dhg->size++; gen = strsep(&cp, " "); /* gen */ if (cp == NULL || *gen == '\0') goto fail; @@ -73,37 +78,41 @@ if (cp != NULL || *prime == '\0') goto fail; - dhg->g = BN_new(); - if (BN_hex2bn(&dhg->g, gen) < 0) { - BN_free(dhg->g); - goto fail; - } - dhg->p = BN_new(); - if (BN_hex2bn(&dhg->p, prime) < 0) { - BN_free(dhg->g); - BN_free(dhg->p); - goto fail; - } + if ((dhg->g = BN_new()) == NULL) + fatal("parse_prime: BN_new failed"); + if ((dhg->p = BN_new()) == NULL) + fatal("parse_prime: BN_new failed"); + if (BN_hex2bn(&dhg->g, gen) == 0) + goto failclean; + if (BN_hex2bn(&dhg->p, prime) == 0) + goto failclean; + + if (BN_num_bits(dhg->p) != dhg->size) + goto failclean; + return (1); + + failclean: + BN_clear_free(dhg->g); + BN_clear_free(dhg->p); fail: - fprintf(stderr, "Bad prime description in line %d\n", linenum); + error("Bad prime description in line %d", linenum); return (0); } DH * -choose_dh(int minbits) +choose_dh(int min, int wantbits, int max) { FILE *f; - char line[1024]; + char line[2048]; int best, bestcount, which; int linenum; struct dhgroup dhg; - f = fopen(DH_PRIMES, "r"); - if (!f) { - perror(DH_PRIMES); - log("WARNING: %s does not exist, using old prime", DH_PRIMES); + if ((f = fopen(_PATH_DH_MODULI, "r")) == NULL && + (f = fopen(_PATH_DH_PRIMES, "r")) == NULL) { + log("WARNING: %s does not exist, using old modulus", _PATH_DH_MODULI); return (dh_new_group1()); } @@ -113,45 +122,168 @@ linenum++; if (!parse_prime(linenum, line, &dhg)) continue; - BN_free(dhg.g); - BN_free(dhg.p); + BN_clear_free(dhg.g); + BN_clear_free(dhg.p); - if ((dhg.size > minbits && dhg.size < best) || - (dhg.size > best && best < minbits)) { + if (dhg.size > max || dhg.size < min) + continue; + + if ((dhg.size > wantbits && dhg.size < best) || + (dhg.size > best && best < wantbits)) { best = dhg.size; bestcount = 0; } if (dhg.size == best) bestcount++; } - fclose (f); + rewind(f); if (bestcount == 0) { - log("WARNING: no primes in %s, using old prime", DH_PRIMES); - return (dh_new_group1()); + fclose(f); + log("WARNING: no suitable primes in %s", _PATH_DH_PRIMES); + return (NULL); } - f = fopen(DH_PRIMES, "r"); - if (!f) { - perror(DH_PRIMES); - exit(1); - } - linenum = 0; which = arc4random() % bestcount; while (fgets(line, sizeof(line), f)) { if (!parse_prime(linenum, line, &dhg)) continue; - if (dhg.size != best) + if ((dhg.size > max || dhg.size < min) || + dhg.size != best || + linenum++ != which) { + BN_clear_free(dhg.g); + BN_clear_free(dhg.p); continue; - if (linenum++ != which) { - BN_free(dhg.g); - BN_free(dhg.p); - continue; } break; } fclose(f); + if (linenum != which+1) + fatal("WARNING: line %d disappeared in %s, giving up", + which, _PATH_DH_PRIMES); return (dh_new_group(dhg.g, dhg.p)); +} + +/* diffie-hellman-group1-sha1 */ + +int +dh_pub_is_valid(DH *dh, BIGNUM *dh_pub) +{ + int i; + int n = BN_num_bits(dh_pub); + int bits_set = 0; + + if (dh_pub->neg) { + log("invalid public DH value: negativ"); + return 0; + } + for (i = 0; i <= n; i++) + if (BN_is_bit_set(dh_pub, i)) + bits_set++; + debug("bits set: %d/%d", bits_set, BN_num_bits(dh->p)); + + /* if g==2 and bits_set==1 then computing log_g(dh_pub) is trivial */ + if (bits_set > 1 && (BN_cmp(dh_pub, dh->p) == -1)) + return 1; + log("invalid public DH value (%d/%d)", bits_set, BN_num_bits(dh->p)); + return 0; +} + +void +dh_gen_key(DH *dh, int need) +{ + int i, bits_set = 0, tries = 0; + + if (dh->p == NULL) + fatal("dh_gen_key: dh->p == NULL"); + if (2*need >= BN_num_bits(dh->p)) + fatal("dh_gen_key: group too small: %d (2*need %d)", + BN_num_bits(dh->p), 2*need); + do { + if (dh->priv_key != NULL) + BN_clear_free(dh->priv_key); + if ((dh->priv_key = BN_new()) == NULL) + fatal("dh_gen_key: BN_new failed"); + /* generate a 2*need bits random private exponent */ + if (!BN_rand(dh->priv_key, 2*need, 0, 0)) + fatal("dh_gen_key: BN_rand failed"); + if (DH_generate_key(dh) == 0) + fatal("DH_generate_key"); + for (i = 0; i <= BN_num_bits(dh->priv_key); i++) + if (BN_is_bit_set(dh->priv_key, i)) + bits_set++; + debug("dh_gen_key: priv key bits set: %d/%d", + bits_set, BN_num_bits(dh->priv_key)); + if (tries++ > 10) + fatal("dh_gen_key: too many bad keys: giving up"); + } while (!dh_pub_is_valid(dh, dh->pub_key)); +} + +DH * +dh_new_group_asc(const char *gen, const char *modulus) +{ + DH *dh; + + if ((dh = DH_new()) == NULL) + fatal("dh_new_group_asc: DH_new"); + + if (BN_hex2bn(&dh->p, modulus) == 0) + fatal("BN_hex2bn p"); + if (BN_hex2bn(&dh->g, gen) == 0) + fatal("BN_hex2bn g"); + + return (dh); +} + +/* + * This just returns the group, we still need to generate the exchange + * value. + */ + +DH * +dh_new_group(BIGNUM *gen, BIGNUM *modulus) +{ + DH *dh; + + if ((dh = DH_new()) == NULL) + fatal("dh_new_group: DH_new"); + dh->p = modulus; + dh->g = gen; + + return (dh); +} + +DH * +dh_new_group1(void) +{ + static char *gen = "2", *group1 = + "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1" + "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD" + "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245" + "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED" + "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE65381" + "FFFFFFFF" "FFFFFFFF"; + + return (dh_new_group_asc(gen, group1)); +} + +/* + * Estimates the group order for a Diffie-Hellman group that has an + * attack complexity approximately the same as O(2**bits). Estimate + * with: O(exp(1.9223 * (ln q)^(1/3) (ln ln q)^(2/3))) + */ + +int +dh_estimate(int bits) +{ + + if (bits < 64) + return (512); /* O(2**63) */ + if (bits < 128) + return (1024); /* O(2**86) */ + if (bits < 192) + return (2048); /* O(2**116) */ + return (4096); /* O(2**156) */ }