From: Bodo Möller Date: Thu, 8 Feb 2001 12:20:25 +0000 (+0000) Subject: Integrate my implementation of a countermeasure against X-Git-Tag: OpenSSL_0_9_6a-beta1~57 X-Git-Url: https://git.librecmc.org/?a=commitdiff_plain;h=07fc72fea10ee005fae181ce104e0c6ae7a42ea6;p=oweals%2Fopenssl.git Integrate my implementation of a countermeasure against Bleichenbacher's DSA attack. With this implementation, the expected number of iterations never exceeds 2. New semantics for BN_rand_range(): BN_rand_range(r, min, range) now generates r such that min <= r < min+range. (Previously, BN_rand_range(r, min, max) generated r such that min <= r < max. It is more convenient to have the range; also the previous prototype was misleading because max was larger than the actual maximum.) --- diff --git a/crypto/bn/bn.h b/crypto/bn/bn.h index fe4fea55cf..9a40276a45 100644 --- a/crypto/bn/bn.h +++ b/crypto/bn/bn.h @@ -328,7 +328,7 @@ BIGNUM *BN_CTX_get(BN_CTX *ctx); void BN_CTX_end(BN_CTX *ctx); int BN_rand(BIGNUM *rnd, int bits, int top,int bottom); int BN_pseudo_rand(BIGNUM *rnd, int bits, int top,int bottom); -int BN_rand_range(BIGNUM *rnd, BIGNUM *min, BIGNUM *max); +int BN_rand_range(BIGNUM *rnd, BIGNUM *min, BIGNUM *range); int BN_num_bits(const BIGNUM *a); int BN_num_bits_word(BN_ULONG); BIGNUM *BN_new(void); @@ -494,6 +494,7 @@ BN_ULONG bn_sub_words(BN_ULONG *rp, BN_ULONG *ap, BN_ULONG *bp,int num); #define BN_F_BN_MPI2BN 112 #define BN_F_BN_NEW 113 #define BN_F_BN_RAND 114 +#define BN_F_BN_RAND_RANGE 122 #define BN_F_BN_USUB 115 /* Reason codes. */ @@ -505,6 +506,7 @@ BN_ULONG bn_sub_words(BN_ULONG *rp, BN_ULONG *ap, BN_ULONG *bp,int num); #define BN_R_ENCODING_ERROR 104 #define BN_R_EXPAND_ON_STATIC_BIGNUM_DATA 105 #define BN_R_INVALID_LENGTH 106 +#define BN_R_INVALID_RANGE 115 #define BN_R_NOT_INITIALIZED 107 #define BN_R_NO_INVERSE 108 #define BN_R_TOO_MANY_TEMPORARY_VARIABLES 109 diff --git a/crypto/bn/bn_err.c b/crypto/bn/bn_err.c index f6b762818d..adc6a214fc 100644 --- a/crypto/bn/bn_err.c +++ b/crypto/bn/bn_err.c @@ -84,6 +84,7 @@ static ERR_STRING_DATA BN_str_functs[]= {ERR_PACK(0,BN_F_BN_MPI2BN,0), "BN_mpi2bn"}, {ERR_PACK(0,BN_F_BN_NEW,0), "BN_new"}, {ERR_PACK(0,BN_F_BN_RAND,0), "BN_rand"}, +{ERR_PACK(0,BN_F_BN_RAND_RANGE,0), "BN_rand_range"}, {ERR_PACK(0,BN_F_BN_USUB,0), "BN_usub"}, {0,NULL} }; @@ -98,6 +99,7 @@ static ERR_STRING_DATA BN_str_reasons[]= {BN_R_ENCODING_ERROR ,"encoding error"}, {BN_R_EXPAND_ON_STATIC_BIGNUM_DATA ,"expand on static bignum data"}, {BN_R_INVALID_LENGTH ,"invalid length"}, +{BN_R_INVALID_RANGE ,"invalid range"}, {BN_R_NOT_INITIALIZED ,"not initialized"}, {BN_R_NO_INVERSE ,"no inverse"}, {BN_R_TOO_MANY_TEMPORARY_VARIABLES ,"too many temporary variables"}, diff --git a/crypto/bn/bn_rand.c b/crypto/bn/bn_rand.c index dfa53bc2f3..0826ce01e3 100644 --- a/crypto/bn/bn_rand.c +++ b/crypto/bn/bn_rand.c @@ -141,14 +141,63 @@ int BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom) return bnrand(1, rnd, bits, top, bottom); } -/* random number r: min <= r < max */ -int BN_rand_range(BIGNUM *r, BIGNUM *min, BIGNUM *max) +/* random number r: min <= r < min+range */ +int BN_rand_range(BIGNUM *r, BIGNUM *min, BIGNUM *range) { - int n = BN_num_bits(max); - do + int n; + + if (range->neg || BN_is_zero(range)) { - if (!BN_rand(r, n, 0, 0)) return 0; - } while ((min && BN_cmp(r, min) < 0) || BN_cmp(r, max) >= 0); + BNerr(BN_F_BN_RAND_RANGE, BN_R_INVALID_RANGE); + return 0; + } + + n = BN_num_bits(range); /* n > 0 */ + + if (n == 1) + { + if (!BN_zero(r)) return 0; + } + else if (BN_is_bit_set(range, n - 2)) + { + do + { + /* range = 11..._2, so each iteration succeeds with probability > .5 */ + if (!BN_rand(r, n, 0, 0)) return 0; + fprintf(stderr, "?"); + } + while (BN_cmp(r, range) >= 0); + fprintf(stderr, "! (11...)\n"); + } + else + { + /* range = 10..._2, + * so 3*range (= 11..._2) is exactly one bit longer than range */ + do + { + if (!BN_rand(r, n + 1, 0, 0)) return 0; + /* If r < 3*range, use r := r MOD range + * (which is either r, r - range, or r - 2*range). + * Otherwise, iterate once more. + * Since 3*range = 11..._2, each iteration succeeds with + * probability > .5. */ + if (BN_cmp(r ,range) >= 0) + { + if (!BN_sub(r, r, range)) return 0; + if (BN_cmp(r, range) >= 0) + if (!BN_sub(r, r, range)) return 0; + } + fprintf(stderr, "?"); + } + while (BN_cmp(r, range) >= 0); + fprintf(stderr, "! (10...)\n"); + } + + if (min != NULL) + { + if (!BN_add(r, r, min)) return 0; + } + return 1; } diff --git a/crypto/dsa/dsa_ossl.c b/crypto/dsa/dsa_ossl.c index 28e5a9e407..a26b47ed5a 100644 --- a/crypto/dsa/dsa_ossl.c +++ b/crypto/dsa/dsa_ossl.c @@ -179,7 +179,9 @@ static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp) kinv=NULL; /* Get random k */ - if (!BN_rand_range(&k, BN_value_one(), dsa->q)) goto err; + do + if (!BN_rand_range(&k, NULL, dsa->q)) goto err; + while (BN_is_zero(&k)); if ((dsa->method_mont_p == NULL) && (dsa->flags & DSA_FLAG_CACHE_MONT_P)) { diff --git a/doc/crypto/BN_rand.pod b/doc/crypto/BN_rand.pod index dc93949246..e4c94e3d12 100644 --- a/doc/crypto/BN_rand.pod +++ b/doc/crypto/BN_rand.pod @@ -12,7 +12,7 @@ BN_rand, BN_pseudo_rand - generate pseudo-random number int BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom); - int BN_rand_range(BIGNUM *rnd, BIGNUM *min, BIGNUM *max); + int BN_rand_range(BIGNUM *rnd, BIGNUM *min, BIGNUM *range); =head1 DESCRIPTION @@ -28,8 +28,8 @@ non-cryptographic purposes and for certain purposes in cryptographic protocols, but usually not for key generation etc. BN_rand_range() generates a cryptographically strong pseudo-random -number B in the range B E= B E B. B -may be NULL, in that case 0 E= B E B. +number B in the range B E= B E B + B. +B may be NULL, in that case 0 E= B E B. The PRNG must be seeded prior to calling BN_rand() or BN_rand_range().