diff options
Diffstat (limited to 'crypto/deterministic_nonce.c')
| -rw-r--r-- | crypto/deterministic_nonce.c | 54 |
1 files changed, 48 insertions, 6 deletions
diff --git a/crypto/deterministic_nonce.c b/crypto/deterministic_nonce.c index 60af7f6ab6..67a5b98d2b 100644 --- a/crypto/deterministic_nonce.c +++ b/crypto/deterministic_nonce.c @@ -7,11 +7,13 @@ * https://www.openssl.org/source/license.html */ +#include <string.h> #include <openssl/bn.h> #include <openssl/evp.h> #include <openssl/core_names.h> #include <openssl/kdf.h> #include "internal/deterministic_nonce.h" +#include "crypto/bn.h" /* * Convert a Bit String to an Integer (See RFC 6979 Section 2.3.2) @@ -39,6 +41,36 @@ static int bits2int(BIGNUM *out, int qlen_bits, } /* + * Convert as above a Bit String in const time to an Integer w fixed top + * + * Params: + * out The returned Integer as a BIGNUM + * qlen_bits The maximum size of the returned integer in bits. The returned + * Integer is shifted right if inlen is larger than qlen_bits.. + * in, inlen The input Bit String (in bytes). It has sizeof(BN_ULONG) bytes + * prefix with all bits set that needs to be cleared out after + * the conversion. + * Returns: 1 if successful, or 0 otherwise. + */ +static int bits2int_consttime(BIGNUM *out, int qlen_bits, + const unsigned char *in, size_t inlen) +{ + int blen_bits = (inlen - sizeof(BN_ULONG)) * 8; + int shift; + + if (BN_bin2bn(in, (int)inlen, out) == NULL) + return 0; + + BN_set_flags(out, BN_FLG_CONSTTIME); + ossl_bn_mask_bits_fixed_top(out, blen_bits); + + shift = blen_bits - qlen_bits; + if (shift > 0) + return bn_rshift_fixed_top(out, out, shift); + return 1; +} + +/* * Convert an Integer to an Octet String (See RFC 6979 2.3.3). * The value is zero padded if required. * @@ -155,8 +187,9 @@ int ossl_gen_deterministic_nonce_rfc6979(BIGNUM *out, const BIGNUM *q, { EVP_KDF_CTX *kdfctx = NULL; int ret = 0, rlen = 0, qlen_bits = 0; - unsigned char *entropyx = NULL, *nonceh = NULL, *T = NULL; + unsigned char *entropyx = NULL, *nonceh = NULL, *rbits = NULL, *T = NULL; size_t allocsz = 0; + const size_t prefsz = sizeof(BN_ULONG); if (out == NULL) return 0; @@ -167,15 +200,18 @@ int ossl_gen_deterministic_nonce_rfc6979(BIGNUM *out, const BIGNUM *q, /* Note rlen used here is in bytes since the input values are byte arrays */ rlen = (qlen_bits + 7) / 8; - allocsz = 3 * rlen; + allocsz = prefsz + 3 * rlen; /* Use a single alloc for the buffers T, nonceh and entropyx */ T = (unsigned char *)OPENSSL_zalloc(allocsz); if (T == NULL) return 0; - nonceh = T + rlen; + rbits = T + prefsz; + nonceh = rbits + rlen; entropyx = nonceh + rlen; + memset(T, 0xff, prefsz); + if (!int2octets(entropyx, priv, rlen) || !bits2octets(nonceh, q, qlen_bits, rlen, hm, hmlen)) goto end; @@ -185,10 +221,16 @@ int ossl_gen_deterministic_nonce_rfc6979(BIGNUM *out, const BIGNUM *q, goto end; do { - if (!EVP_KDF_derive(kdfctx, T, rlen, NULL) - || !bits2int(out, qlen_bits, T, rlen)) + if (!EVP_KDF_derive(kdfctx, rbits, rlen, NULL) + || !bits2int_consttime(out, qlen_bits, T, rlen + prefsz)) goto end; - } while (BN_is_zero(out) || BN_is_one(out) || BN_cmp(out, q) >= 0); + } while (ossl_bn_is_word_fixed_top(out, 0) + || ossl_bn_is_word_fixed_top(out, 1) + || BN_ucmp(out, q) >= 0); +#ifdef BN_DEBUG + /* With BN_DEBUG on a fixed top number cannot be returned */ + bn_correct_top(out); +#endif ret = 1; end: |