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a380ae85be
Otherwise following operations would bail out in bn_check_top(). Reviewed-by: Paul Dale <ppzgs1@gmail.com> Reviewed-by: Neil Horman <nhorman@openssl.org> (Merged from https://github.com/openssl/openssl/pull/24265)
241 lines
7.5 KiB
C
241 lines
7.5 KiB
C
/*
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* Copyright 2022-2023 The OpenSSL Project Authors. All Rights Reserved.
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*
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* Licensed under the Apache License 2.0 (the "License"). You may not use
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* this file except in compliance with the License. You can obtain a copy
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* in the file LICENSE in the source distribution or at
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* https://www.openssl.org/source/license.html
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*/
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#include <string.h>
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#include <openssl/bn.h>
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#include <openssl/evp.h>
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#include <openssl/core_names.h>
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#include <openssl/kdf.h>
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#include "internal/deterministic_nonce.h"
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#include "crypto/bn.h"
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/*
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* Convert a Bit String to an Integer (See RFC 6979 Section 2.3.2)
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*
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* Params:
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* out The returned Integer as a BIGNUM
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* qlen_bits The maximum size of the returned integer in bits. The returned
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* Integer is shifted right if inlen is larger than qlen_bits..
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* in, inlen The input Bit String (in bytes).
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* Returns: 1 if successful, or 0 otherwise.
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*/
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static int bits2int(BIGNUM *out, int qlen_bits,
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const unsigned char *in, size_t inlen)
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{
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int blen_bits = inlen * 8;
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int shift;
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if (BN_bin2bn(in, (int)inlen, out) == NULL)
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return 0;
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shift = blen_bits - qlen_bits;
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if (shift > 0)
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return BN_rshift(out, out, shift);
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return 1;
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}
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/*
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* Convert as above a Bit String in const time to an Integer w fixed top
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*
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* Params:
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* out The returned Integer as a BIGNUM
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* qlen_bits The maximum size of the returned integer in bits. The returned
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* Integer is shifted right if inlen is larger than qlen_bits..
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* in, inlen The input Bit String (in bytes). It has sizeof(BN_ULONG) bytes
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* prefix with all bits set that needs to be cleared out after
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* the conversion.
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* Returns: 1 if successful, or 0 otherwise.
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*/
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static int bits2int_consttime(BIGNUM *out, int qlen_bits,
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const unsigned char *in, size_t inlen)
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{
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int blen_bits = (inlen - sizeof(BN_ULONG)) * 8;
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int shift;
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if (BN_bin2bn(in, (int)inlen, out) == NULL)
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return 0;
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BN_set_flags(out, BN_FLG_CONSTTIME);
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ossl_bn_mask_bits_fixed_top(out, blen_bits);
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shift = blen_bits - qlen_bits;
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if (shift > 0)
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return bn_rshift_fixed_top(out, out, shift);
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return 1;
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}
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/*
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* Convert an Integer to an Octet String (See RFC 6979 2.3.3).
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* The value is zero padded if required.
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*
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* Params:
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* out The returned Octet String
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* num The input Integer
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* rlen The required size of the returned Octet String in bytes
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* Returns: 1 if successful, or 0 otherwise.
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*/
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static int int2octets(unsigned char *out, const BIGNUM *num, int rlen)
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{
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return BN_bn2binpad(num, out, rlen) >= 0;
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}
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/*
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* Convert a Bit String to an Octet String (See RFC 6979 Section 2.3.4)
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*
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* Params:
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* out The returned octet string.
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* q The modulus
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* qlen_bits The length of q in bits
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* rlen The value of qlen_bits rounded up to the nearest 8 bits.
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* in, inlen The input bit string (in bytes)
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* Returns: 1 if successful, or 0 otherwise.
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*/
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static int bits2octets(unsigned char *out, const BIGNUM *q, int qlen_bits,
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int rlen, const unsigned char *in, size_t inlen)
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{
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int ret = 0;
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BIGNUM *z = BN_new();
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if (z == NULL
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|| !bits2int(z, qlen_bits, in, inlen))
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goto err;
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/* z2 = z1 mod q (Do a simple subtract, since z1 < 2^qlen_bits) */
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if (BN_cmp(z, q) >= 0
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&& !BN_usub(z, z, q))
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goto err;
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ret = int2octets(out, z, rlen);
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err:
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BN_free(z);
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return ret;
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}
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/*
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* Setup a KDF HMAC_DRBG object using fixed entropy and nonce data.
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*
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* Params:
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* digestname The digest name for the HMAC
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* entropy, entropylen A fixed input entropy buffer
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* nonce, noncelen A fixed input nonce buffer
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* libctx, propq Are used for fetching algorithms
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*
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* Returns: The created KDF HMAC_DRBG object if successful, or NULL otherwise.
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*/
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static EVP_KDF_CTX *kdf_setup(const char *digestname,
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const unsigned char *entropy, size_t entropylen,
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const unsigned char *nonce, size_t noncelen,
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OSSL_LIB_CTX *libctx, const char *propq)
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{
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EVP_KDF_CTX *ctx = NULL;
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EVP_KDF *kdf = NULL;
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OSSL_PARAM params[5], *p;
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kdf = EVP_KDF_fetch(libctx, "HMAC-DRBG-KDF", propq);
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ctx = EVP_KDF_CTX_new(kdf);
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EVP_KDF_free(kdf);
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if (ctx == NULL)
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goto err;
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p = params;
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*p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST,
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(char *)digestname, 0);
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if (propq != NULL)
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*p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_PROPERTIES,
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(char *)propq, 0);
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*p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_HMACDRBG_ENTROPY,
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(void *)entropy, entropylen);
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*p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_HMACDRBG_NONCE,
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(void *)nonce, noncelen);
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*p = OSSL_PARAM_construct_end();
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if (EVP_KDF_CTX_set_params(ctx, params) <= 0)
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goto err;
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return ctx;
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err:
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EVP_KDF_CTX_free(ctx);
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return NULL;
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}
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/*
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* Generate a Deterministic nonce 'k' for DSA/ECDSA as defined in
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* RFC 6979 Section 3.3. "Alternate Description of the Generation of k"
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*
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* Params:
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* out Returns the generated deterministic nonce 'k'
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* q A large prime number used for modulus operations for DSA and ECDSA.
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* priv The private key in the range [1, q-1]
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* hm, hmlen The digested message buffer in bytes
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* digestname The digest name used for signing. It is used as the HMAC digest.
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* libctx, propq Used for fetching algorithms
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*
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* Returns: 1 if successful, or 0 otherwise.
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*/
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int ossl_gen_deterministic_nonce_rfc6979(BIGNUM *out, const BIGNUM *q,
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const BIGNUM *priv,
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const unsigned char *hm, size_t hmlen,
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const char *digestname,
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OSSL_LIB_CTX *libctx,
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const char *propq)
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{
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EVP_KDF_CTX *kdfctx = NULL;
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int ret = 0, rlen = 0, qlen_bits = 0;
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unsigned char *entropyx = NULL, *nonceh = NULL, *rbits = NULL, *T = NULL;
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size_t allocsz = 0;
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const size_t prefsz = sizeof(BN_ULONG);
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if (out == NULL)
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return 0;
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qlen_bits = BN_num_bits(q);
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if (qlen_bits == 0)
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return 0;
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/* Note rlen used here is in bytes since the input values are byte arrays */
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rlen = (qlen_bits + 7) / 8;
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allocsz = prefsz + 3 * rlen;
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/* Use a single alloc for the buffers T, nonceh and entropyx */
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T = (unsigned char *)OPENSSL_zalloc(allocsz);
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if (T == NULL)
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return 0;
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rbits = T + prefsz;
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nonceh = rbits + rlen;
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entropyx = nonceh + rlen;
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memset(T, 0xff, prefsz);
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if (!int2octets(entropyx, priv, rlen)
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|| !bits2octets(nonceh, q, qlen_bits, rlen, hm, hmlen))
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goto end;
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kdfctx = kdf_setup(digestname, entropyx, rlen, nonceh, rlen, libctx, propq);
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if (kdfctx == NULL)
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goto end;
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do {
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if (!EVP_KDF_derive(kdfctx, rbits, rlen, NULL)
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|| !bits2int_consttime(out, qlen_bits, T, rlen + prefsz))
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goto end;
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} while (ossl_bn_is_word_fixed_top(out, 0)
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|| ossl_bn_is_word_fixed_top(out, 1)
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|| BN_ucmp(out, q) >= 0);
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#ifdef BN_DEBUG
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/* With BN_DEBUG on a fixed top number cannot be returned */
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bn_correct_top(out);
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#endif
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ret = 1;
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end:
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EVP_KDF_CTX_free(kdfctx);
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OPENSSL_clear_free(T, allocsz);
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return ret;
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}
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