diff options
Diffstat (limited to 'crypto/bn')
-rw-r--r-- | crypto/bn/bn_lib.c | 53 | ||||
-rw-r--r-- | crypto/bn/bn_rand.c | 166 | ||||
-rw-r--r-- | crypto/bn/bn_shift.c | 8 |
3 files changed, 177 insertions, 50 deletions
diff --git a/crypto/bn/bn_lib.c b/crypto/bn/bn_lib.c index 9070647b35..18c9d54f67 100644 --- a/crypto/bn/bn_lib.c +++ b/crypto/bn/bn_lib.c @@ -1,5 +1,5 @@ /* - * Copyright 1995-2023 The OpenSSL Project Authors. All Rights Reserved. + * Copyright 1995-2024 The OpenSSL Project Authors. All Rights Reserved. * * Licensed under the Apache License 2.0 (the "License"). You may not use * this file except in compliance with the License. You can obtain a copy @@ -708,14 +708,29 @@ int BN_ucmp(const BIGNUM *a, const BIGNUM *b) int i; BN_ULONG t1, t2, *ap, *bp; + ap = a->d; + bp = b->d; + + if (BN_get_flags(a, BN_FLG_CONSTTIME) + && a->top == b->top) { + int res = 0; + + for (i = 0; i < b->top; i++) { + res = constant_time_select_int(constant_time_lt_bn(ap[i], bp[i]), + -1, res); + res = constant_time_select_int(constant_time_lt_bn(bp[i], ap[i]), + 1, res); + } + return res; + } + bn_check_top(a); bn_check_top(b); i = a->top - b->top; if (i != 0) return i; - ap = a->d; - bp = b->d; + for (i = a->top - 1; i >= 0; i--) { t1 = ap[i]; t2 = bp[i]; @@ -827,11 +842,10 @@ int BN_is_bit_set(const BIGNUM *a, int n) return (int)(((a->d[i]) >> j) & ((BN_ULONG)1)); } -int BN_mask_bits(BIGNUM *a, int n) +int ossl_bn_mask_bits_fixed_top(BIGNUM *a, int n) { int b, w; - bn_check_top(a); if (n < 0) return 0; @@ -845,10 +859,21 @@ int BN_mask_bits(BIGNUM *a, int n) a->top = w + 1; a->d[w] &= ~(BN_MASK2 << b); } - bn_correct_top(a); + a->flags |= BN_FLG_FIXED_TOP; return 1; } +int BN_mask_bits(BIGNUM *a, int n) +{ + int ret; + + bn_check_top(a); + ret = ossl_bn_mask_bits_fixed_top(a, n); + if (ret) + bn_correct_top(a); + return ret; +} + void BN_set_negative(BIGNUM *a, int b) { if (b && !BN_is_zero(a)) @@ -1022,6 +1047,22 @@ int BN_is_word(const BIGNUM *a, const BN_ULONG w) return BN_abs_is_word(a, w) && (!w || !a->neg); } +int ossl_bn_is_word_fixed_top(const BIGNUM *a, const BN_ULONG w) +{ + int res, i; + const BN_ULONG *ap = a->d; + + if (a->neg || a->top == 0) + return 0; + + res = constant_time_select_int(constant_time_eq_bn(ap[0], w), 1, 0); + + for (i = 1; i < a->top; i++) + res = constant_time_select_int(constant_time_is_zero_bn(ap[i]), + res, 0); + return res; +} + int BN_is_odd(const BIGNUM *a) { return (a->top > 0) && (a->d[0] & 1); diff --git a/crypto/bn/bn_rand.c b/crypto/bn/bn_rand.c index a94dfcecdf..da537a07a9 100644 --- a/crypto/bn/bn_rand.c +++ b/crypto/bn/bn_rand.c @@ -1,5 +1,5 @@ /* - * Copyright 1995-2023 The OpenSSL Project Authors. All Rights Reserved. + * Copyright 1995-2024 The OpenSSL Project Authors. All Rights Reserved. * * Licensed under the Apache License 2.0 (the "License"). You may not use * this file except in compliance with the License. You can obtain a copy @@ -184,8 +184,8 @@ static int bnrand_range(BNRAND_FLAG flag, BIGNUM *r, const BIGNUM *range, } else { do { /* range = 11..._2 or range = 101..._2 */ - if (!bnrand(flag, r, n, BN_RAND_TOP_ANY, BN_RAND_BOTTOM_ANY, 0, - ctx)) + if (!bnrand(flag, r, n, BN_RAND_TOP_ANY, BN_RAND_BOTTOM_ANY, + strength, ctx)) return 0; if (!--count) { @@ -238,17 +238,63 @@ int BN_pseudo_rand_range(BIGNUM *r, const BIGNUM *range) # endif #endif +int ossl_bn_priv_rand_range_fixed_top(BIGNUM *r, const BIGNUM *range, + unsigned int strength, BN_CTX *ctx) +{ + int n; + int count = 100; + + if (r == NULL) { + ERR_raise(ERR_LIB_BN, ERR_R_PASSED_NULL_PARAMETER); + return 0; + } + + if (range->neg || BN_is_zero(range)) { + ERR_raise(ERR_LIB_BN, BN_R_INVALID_RANGE); + return 0; + } + + n = BN_num_bits(range); /* n > 0 */ + + /* BN_is_bit_set(range, n - 1) always holds */ + + if (n == 1) { + BN_zero(r); + } else { + BN_set_flags(r, BN_FLG_CONSTTIME); + do { + if (!bnrand(PRIVATE, r, n + 1, BN_RAND_TOP_ONE, BN_RAND_BOTTOM_ANY, + strength, ctx)) + return 0; + + if (!--count) { + ERR_raise(ERR_LIB_BN, BN_R_TOO_MANY_ITERATIONS); + return 0; + } + ossl_bn_mask_bits_fixed_top(r, n); + } + while (BN_ucmp(r, range) >= 0); +#ifdef BN_DEBUG + /* With BN_DEBUG on a fixed top number cannot be returned */ + bn_correct_top(r); +#endif + } + + return 1; +} + /* - * BN_generate_dsa_nonce generates a random number 0 <= out < range. Unlike - * BN_rand_range, it also includes the contents of |priv| and |message| in - * the generation so that an RNG failure isn't fatal as long as |priv| + * ossl_bn_gen_dsa_nonce_fixed_top generates a random number 0 <= out < range. + * Unlike BN_rand_range, it also includes the contents of |priv| and |message| + * in the generation so that an RNG failure isn't fatal as long as |priv| * remains secret. This is intended for use in DSA and ECDSA where an RNG * weakness leads directly to private key exposure unless this function is * used. */ -int BN_generate_dsa_nonce(BIGNUM *out, const BIGNUM *range, - const BIGNUM *priv, const unsigned char *message, - size_t message_len, BN_CTX *ctx) +int ossl_bn_gen_dsa_nonce_fixed_top(BIGNUM *out, const BIGNUM *range, + const BIGNUM *priv, + const unsigned char *message, + size_t message_len, BN_CTX *ctx) { EVP_MD_CTX *mdctx = EVP_MD_CTX_new(); /* @@ -258,20 +304,24 @@ int BN_generate_dsa_nonce(BIGNUM *out, const BIGNUM *range, unsigned char random_bytes[64]; unsigned char digest[SHA512_DIGEST_LENGTH]; unsigned done, todo; - /* We generate |range|+8 bytes of random output. */ - const unsigned num_k_bytes = BN_num_bytes(range) + 8; + /* We generate |range|+1 bytes of random output. */ + const unsigned num_k_bytes = BN_num_bytes(range) + 1; unsigned char private_bytes[96]; unsigned char *k_bytes = NULL; + const int max_n = 64; /* Pr(failure to generate) < 2^max_n */ + int n; int ret = 0; EVP_MD *md = NULL; OSSL_LIB_CTX *libctx = ossl_bn_get_libctx(ctx); if (mdctx == NULL) - goto err; + goto end; k_bytes = OPENSSL_malloc(num_k_bytes); if (k_bytes == NULL) - goto err; + goto end; + /* Ensure top byte is set to avoid non-constant time in bin2bn */ + k_bytes[0] = 0xff; /* We copy |priv| into a local buffer to avoid exposing its length. */ if (BN_bn2binpad(priv, private_bytes, sizeof(private_bytes)) < 0) { @@ -281,41 +331,60 @@ int BN_generate_dsa_nonce(BIGNUM *out, const BIGNUM *range, * length of the private key. */ ERR_raise(ERR_LIB_BN, BN_R_PRIVATE_KEY_TOO_LARGE); - goto err; + goto end; } md = EVP_MD_fetch(libctx, "SHA512", NULL); if (md == NULL) { ERR_raise(ERR_LIB_BN, BN_R_NO_SUITABLE_DIGEST); - goto err; - } - for (done = 0; done < num_k_bytes;) { - if (RAND_priv_bytes_ex(libctx, random_bytes, sizeof(random_bytes), 0) <= 0) - goto err; - - if (!EVP_DigestInit_ex(mdctx, md, NULL) - || !EVP_DigestUpdate(mdctx, &done, sizeof(done)) - || !EVP_DigestUpdate(mdctx, private_bytes, - sizeof(private_bytes)) - || !EVP_DigestUpdate(mdctx, message, message_len) - || !EVP_DigestUpdate(mdctx, random_bytes, sizeof(random_bytes)) - || !EVP_DigestFinal_ex(mdctx, digest, NULL)) - goto err; - - todo = num_k_bytes - done; - if (todo > SHA512_DIGEST_LENGTH) - todo = SHA512_DIGEST_LENGTH; - memcpy(k_bytes + done, digest, todo); - done += todo; + goto end; } + for (n = 0; n < max_n; n++) { + unsigned char i = 0; + + for (done = 1; done < num_k_bytes;) { + if (RAND_priv_bytes_ex(libctx, random_bytes, sizeof(random_bytes), + 0) <= 0) + goto end; + + if (!EVP_DigestInit_ex(mdctx, md, NULL) + || !EVP_DigestUpdate(mdctx, &i, sizeof(i)) + || !EVP_DigestUpdate(mdctx, private_bytes, + sizeof(private_bytes)) + || !EVP_DigestUpdate(mdctx, message, message_len) + || !EVP_DigestUpdate(mdctx, random_bytes, + sizeof(random_bytes)) + || !EVP_DigestFinal_ex(mdctx, digest, NULL)) + goto end; + + todo = num_k_bytes - done; + if (todo > SHA512_DIGEST_LENGTH) + todo = SHA512_DIGEST_LENGTH; + memcpy(k_bytes + done, digest, todo); + done += todo; + ++i; + } - if (!BN_bin2bn(k_bytes, num_k_bytes, out)) - goto err; - if (BN_mod(out, out, range, ctx) != 1) - goto err; - ret = 1; + if (!BN_bin2bn(k_bytes, num_k_bytes, out)) + goto end; - err: + /* Clear out the top bits and rejection filter into range */ + BN_set_flags(out, BN_FLG_CONSTTIME); + ossl_bn_mask_bits_fixed_top(out, BN_num_bits(range)); + + if (BN_ucmp(out, range) < 0) { + ret = 1; +#ifdef BN_DEBUG + /* With BN_DEBUG on a fixed top number cannot be returned */ + bn_correct_top(out); +#endif + goto end; + } + } + /* Failed to generate anything */ + ERR_raise(ERR_LIB_BN, ERR_R_INTERNAL_ERROR); + + end: EVP_MD_CTX_free(mdctx); EVP_MD_free(md); OPENSSL_clear_free(k_bytes, num_k_bytes); @@ -324,3 +393,20 @@ int BN_generate_dsa_nonce(BIGNUM *out, const BIGNUM *range, OPENSSL_cleanse(private_bytes, sizeof(private_bytes)); return ret; } + +int BN_generate_dsa_nonce(BIGNUM *out, const BIGNUM *range, + const BIGNUM *priv, const unsigned char *message, + size_t message_len, BN_CTX *ctx) +{ + int ret; + + ret = ossl_bn_gen_dsa_nonce_fixed_top(out, range, priv, message, + message_len, ctx); + /* + * This call makes the BN_generate_dsa_nonce non-const-time, thus we + * do not use it internally. But fixed_top BNs currently cannot be returned + * from public API calls. + */ + bn_correct_top(out); + return ret; +} diff --git a/crypto/bn/bn_shift.c b/crypto/bn/bn_shift.c index 8fcb04324e..d67331f1f6 100644 --- a/crypto/bn/bn_shift.c +++ b/crypto/bn/bn_shift.c @@ -1,5 +1,5 @@ /* - * Copyright 1995-2020 The OpenSSL Project Authors. All Rights Reserved. + * Copyright 1995-2024 The OpenSSL Project Authors. All Rights Reserved. * * Licensed under the Apache License 2.0 (the "License"). You may not use * this file except in compliance with the License. You can obtain a copy @@ -156,6 +156,9 @@ int BN_rshift(BIGNUM *r, const BIGNUM *a, int n) return 0; } + bn_check_top(r); + bn_check_top(a); + ret = bn_rshift_fixed_top(r, a, n); bn_correct_top(r); @@ -177,9 +180,6 @@ int bn_rshift_fixed_top(BIGNUM *r, const BIGNUM *a, int n) BN_ULONG *t, *f; BN_ULONG l, m, mask; - bn_check_top(r); - bn_check_top(a); - assert(n >= 0); nw = n / BN_BITS2; |