Modified mbed TLS headers for AES functionality only to reduce build size
Dependents: BLE_Gateway_Linker_fix BLE_Gateway
Fork of mbedtls by
source/ecdsa.c
- Committer:
- Christopher Haster
- Date:
- 2016-01-22
- Revision:
- 1:24750b9ad5ef
File content as of revision 1:24750b9ad5ef:
/* * Elliptic curve DSA * * Copyright (C) 2006-2015, ARM Limited, All Rights Reserved * SPDX-License-Identifier: Apache-2.0 * * Licensed under the Apache License, Version 2.0 (the "License"); you may * not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. * * This file is part of mbed TLS (https://tls.mbed.org) */ /* * References: * * SEC1 http://www.secg.org/index.php?action=secg,docs_secg */ #if !defined(MBEDTLS_CONFIG_FILE) #include "mbedtls/config.h" #else #include MBEDTLS_CONFIG_FILE #endif #if defined(MBEDTLS_ECDSA_C) #include "mbedtls/ecdsa.h" #include "mbedtls/asn1write.h" #include <string.h> #if defined(MBEDTLS_ECDSA_DETERMINISTIC) #include "mbedtls/hmac_drbg.h" #endif /* * Derive a suitable integer for group grp from a buffer of length len * SEC1 4.1.3 step 5 aka SEC1 4.1.4 step 3 */ static int derive_mpi( const mbedtls_ecp_group *grp, mbedtls_mpi *x, const unsigned char *buf, size_t blen ) { int ret; size_t n_size = ( grp->nbits + 7 ) / 8; size_t use_size = blen > n_size ? n_size : blen; MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( x, buf, use_size ) ); if( use_size * 8 > grp->nbits ) MBEDTLS_MPI_CHK( mbedtls_mpi_shift_r( x, use_size * 8 - grp->nbits ) ); /* While at it, reduce modulo N */ if( mbedtls_mpi_cmp_mpi( x, &grp->N ) >= 0 ) MBEDTLS_MPI_CHK( mbedtls_mpi_sub_mpi( x, x, &grp->N ) ); cleanup: return( ret ); } /* * Compute ECDSA signature of a hashed message (SEC1 4.1.3) * Obviously, compared to SEC1 4.1.3, we skip step 4 (hash message) */ int mbedtls_ecdsa_sign( mbedtls_ecp_group *grp, mbedtls_mpi *r, mbedtls_mpi *s, const mbedtls_mpi *d, const unsigned char *buf, size_t blen, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng ) { int ret, key_tries, sign_tries, blind_tries; mbedtls_ecp_point R; mbedtls_mpi k, e, t; /* Fail cleanly on curves such as Curve25519 that can't be used for ECDSA */ if( grp->N.p == NULL ) return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA ); mbedtls_ecp_point_init( &R ); mbedtls_mpi_init( &k ); mbedtls_mpi_init( &e ); mbedtls_mpi_init( &t ); sign_tries = 0; do { /* * Steps 1-3: generate a suitable ephemeral keypair * and set r = xR mod n */ key_tries = 0; do { MBEDTLS_MPI_CHK( mbedtls_ecp_gen_keypair( grp, &k, &R, f_rng, p_rng ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( r, &R.X, &grp->N ) ); if( key_tries++ > 10 ) { ret = MBEDTLS_ERR_ECP_RANDOM_FAILED; goto cleanup; } } while( mbedtls_mpi_cmp_int( r, 0 ) == 0 ); /* * Step 5: derive MPI from hashed message */ MBEDTLS_MPI_CHK( derive_mpi( grp, &e, buf, blen ) ); /* * Generate a random value to blind inv_mod in next step, * avoiding a potential timing leak. */ blind_tries = 0; do { size_t n_size = ( grp->nbits + 7 ) / 8; MBEDTLS_MPI_CHK( mbedtls_mpi_fill_random( &t, n_size, f_rng, p_rng ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_shift_r( &t, 8 * n_size - grp->nbits ) ); /* See mbedtls_ecp_gen_keypair() */ if( ++blind_tries > 30 ) return( MBEDTLS_ERR_ECP_RANDOM_FAILED ); } while( mbedtls_mpi_cmp_int( &t, 1 ) < 0 || mbedtls_mpi_cmp_mpi( &t, &grp->N ) >= 0 ); /* * Step 6: compute s = (e + r * d) / k = t (e + rd) / (kt) mod n */ MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( s, r, d ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_add_mpi( &e, &e, s ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &e, &e, &t ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &k, &k, &t ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_inv_mod( s, &k, &grp->N ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( s, s, &e ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( s, s, &grp->N ) ); if( sign_tries++ > 10 ) { ret = MBEDTLS_ERR_ECP_RANDOM_FAILED; goto cleanup; } } while( mbedtls_mpi_cmp_int( s, 0 ) == 0 ); cleanup: mbedtls_ecp_point_free( &R ); mbedtls_mpi_free( &k ); mbedtls_mpi_free( &e ); mbedtls_mpi_free( &t ); return( ret ); } #if defined(MBEDTLS_ECDSA_DETERMINISTIC) /* * Deterministic signature wrapper */ int mbedtls_ecdsa_sign_det( mbedtls_ecp_group *grp, mbedtls_mpi *r, mbedtls_mpi *s, const mbedtls_mpi *d, const unsigned char *buf, size_t blen, mbedtls_md_type_t md_alg ) { int ret; mbedtls_hmac_drbg_context rng_ctx; unsigned char data[2 * MBEDTLS_ECP_MAX_BYTES]; size_t grp_len = ( grp->nbits + 7 ) / 8; const mbedtls_md_info_t *md_info; mbedtls_mpi h; if( ( md_info = mbedtls_md_info_from_type( md_alg ) ) == NULL ) return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA ); mbedtls_mpi_init( &h ); mbedtls_hmac_drbg_init( &rng_ctx ); /* Use private key and message hash (reduced) to initialize HMAC_DRBG */ MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( d, data, grp_len ) ); MBEDTLS_MPI_CHK( derive_mpi( grp, &h, buf, blen ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &h, data + grp_len, grp_len ) ); mbedtls_hmac_drbg_seed_buf( &rng_ctx, md_info, data, 2 * grp_len ); ret = mbedtls_ecdsa_sign( grp, r, s, d, buf, blen, mbedtls_hmac_drbg_random, &rng_ctx ); cleanup: mbedtls_hmac_drbg_free( &rng_ctx ); mbedtls_mpi_free( &h ); return( ret ); } #endif /* MBEDTLS_ECDSA_DETERMINISTIC */ /* * Verify ECDSA signature of hashed message (SEC1 4.1.4) * Obviously, compared to SEC1 4.1.3, we skip step 2 (hash message) */ int mbedtls_ecdsa_verify( mbedtls_ecp_group *grp, const unsigned char *buf, size_t blen, const mbedtls_ecp_point *Q, const mbedtls_mpi *r, const mbedtls_mpi *s) { int ret; mbedtls_mpi e, s_inv, u1, u2; mbedtls_ecp_point R; mbedtls_ecp_point_init( &R ); mbedtls_mpi_init( &e ); mbedtls_mpi_init( &s_inv ); mbedtls_mpi_init( &u1 ); mbedtls_mpi_init( &u2 ); /* Fail cleanly on curves such as Curve25519 that can't be used for ECDSA */ if( grp->N.p == NULL ) return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA ); /* * Step 1: make sure r and s are in range 1..n-1 */ if( mbedtls_mpi_cmp_int( r, 1 ) < 0 || mbedtls_mpi_cmp_mpi( r, &grp->N ) >= 0 || mbedtls_mpi_cmp_int( s, 1 ) < 0 || mbedtls_mpi_cmp_mpi( s, &grp->N ) >= 0 ) { ret = MBEDTLS_ERR_ECP_VERIFY_FAILED; goto cleanup; } /* * Additional precaution: make sure Q is valid */ MBEDTLS_MPI_CHK( mbedtls_ecp_check_pubkey( grp, Q ) ); /* * Step 3: derive MPI from hashed message */ MBEDTLS_MPI_CHK( derive_mpi( grp, &e, buf, blen ) ); /* * Step 4: u1 = e / s mod n, u2 = r / s mod n */ MBEDTLS_MPI_CHK( mbedtls_mpi_inv_mod( &s_inv, s, &grp->N ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &u1, &e, &s_inv ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &u1, &u1, &grp->N ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &u2, r, &s_inv ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &u2, &u2, &grp->N ) ); /* * Step 5: R = u1 G + u2 Q * * Since we're not using any secret data, no need to pass a RNG to * mbedtls_ecp_mul() for countermesures. */ MBEDTLS_MPI_CHK( mbedtls_ecp_muladd( grp, &R, &u1, &grp->G, &u2, Q ) ); if( mbedtls_ecp_is_zero( &R ) ) { ret = MBEDTLS_ERR_ECP_VERIFY_FAILED; goto cleanup; } /* * Step 6: convert xR to an integer (no-op) * Step 7: reduce xR mod n (gives v) */ MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &R.X, &R.X, &grp->N ) ); /* * Step 8: check if v (that is, R.X) is equal to r */ if( mbedtls_mpi_cmp_mpi( &R.X, r ) != 0 ) { ret = MBEDTLS_ERR_ECP_VERIFY_FAILED; goto cleanup; } cleanup: mbedtls_ecp_point_free( &R ); mbedtls_mpi_free( &e ); mbedtls_mpi_free( &s_inv ); mbedtls_mpi_free( &u1 ); mbedtls_mpi_free( &u2 ); return( ret ); } /* * Convert a signature (given by context) to ASN.1 */ static int ecdsa_signature_to_asn1( const mbedtls_mpi *r, const mbedtls_mpi *s, unsigned char *sig, size_t *slen ) { int ret; unsigned char buf[MBEDTLS_ECDSA_MAX_LEN]; unsigned char *p = buf + sizeof( buf ); size_t len = 0; MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &p, buf, s ) ); MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &p, buf, r ) ); MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &p, buf, len ) ); MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &p, buf, MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ); memcpy( sig, p, len ); *slen = len; return( 0 ); } /* * Compute and write signature */ int mbedtls_ecdsa_write_signature( mbedtls_ecdsa_context *ctx, mbedtls_md_type_t md_alg, const unsigned char *hash, size_t hlen, unsigned char *sig, size_t *slen, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng ) { int ret; mbedtls_mpi r, s; mbedtls_mpi_init( &r ); mbedtls_mpi_init( &s ); #if defined(MBEDTLS_ECDSA_DETERMINISTIC) (void) f_rng; (void) p_rng; MBEDTLS_MPI_CHK( mbedtls_ecdsa_sign_det( &ctx->grp, &r, &s, &ctx->d, hash, hlen, md_alg ) ); #else (void) md_alg; MBEDTLS_MPI_CHK( mbedtls_ecdsa_sign( &ctx->grp, &r, &s, &ctx->d, hash, hlen, f_rng, p_rng ) ); #endif MBEDTLS_MPI_CHK( ecdsa_signature_to_asn1( &r, &s, sig, slen ) ); cleanup: mbedtls_mpi_free( &r ); mbedtls_mpi_free( &s ); return( ret ); } #if ! defined(MBEDTLS_DEPRECATED_REMOVED) && \ defined(MBEDTLS_ECDSA_DETERMINISTIC) int mbedtls_ecdsa_write_signature_det( mbedtls_ecdsa_context *ctx, const unsigned char *hash, size_t hlen, unsigned char *sig, size_t *slen, mbedtls_md_type_t md_alg ) { return( mbedtls_ecdsa_write_signature( ctx, md_alg, hash, hlen, sig, slen, NULL, NULL ) ); } #endif /* * Read and check signature */ int mbedtls_ecdsa_read_signature( mbedtls_ecdsa_context *ctx, const unsigned char *hash, size_t hlen, const unsigned char *sig, size_t slen ) { int ret; unsigned char *p = (unsigned char *) sig; const unsigned char *end = sig + slen; size_t len; mbedtls_mpi r, s; mbedtls_mpi_init( &r ); mbedtls_mpi_init( &s ); if( ( ret = mbedtls_asn1_get_tag( &p, end, &len, MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ) != 0 ) { ret += MBEDTLS_ERR_ECP_BAD_INPUT_DATA; goto cleanup; } if( p + len != end ) { ret = MBEDTLS_ERR_ECP_BAD_INPUT_DATA + MBEDTLS_ERR_ASN1_LENGTH_MISMATCH; goto cleanup; } if( ( ret = mbedtls_asn1_get_mpi( &p, end, &r ) ) != 0 || ( ret = mbedtls_asn1_get_mpi( &p, end, &s ) ) != 0 ) { ret += MBEDTLS_ERR_ECP_BAD_INPUT_DATA; goto cleanup; } if( ( ret = mbedtls_ecdsa_verify( &ctx->grp, hash, hlen, &ctx->Q, &r, &s ) ) != 0 ) goto cleanup; if( p != end ) ret = MBEDTLS_ERR_ECP_SIG_LEN_MISMATCH; cleanup: mbedtls_mpi_free( &r ); mbedtls_mpi_free( &s ); return( ret ); } /* * Generate key pair */ int mbedtls_ecdsa_genkey( mbedtls_ecdsa_context *ctx, mbedtls_ecp_group_id gid, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng ) { return( mbedtls_ecp_group_load( &ctx->grp, gid ) || mbedtls_ecp_gen_keypair( &ctx->grp, &ctx->d, &ctx->Q, f_rng, p_rng ) ); } /* * Set context from an mbedtls_ecp_keypair */ int mbedtls_ecdsa_from_keypair( mbedtls_ecdsa_context *ctx, const mbedtls_ecp_keypair *key ) { int ret; if( ( ret = mbedtls_ecp_group_copy( &ctx->grp, &key->grp ) ) != 0 || ( ret = mbedtls_mpi_copy( &ctx->d, &key->d ) ) != 0 || ( ret = mbedtls_ecp_copy( &ctx->Q, &key->Q ) ) != 0 ) { mbedtls_ecdsa_free( ctx ); } return( ret ); } /* * Initialize context */ void mbedtls_ecdsa_init( mbedtls_ecdsa_context *ctx ) { mbedtls_ecp_keypair_init( ctx ); } /* * Free context */ void mbedtls_ecdsa_free( mbedtls_ecdsa_context *ctx ) { mbedtls_ecp_keypair_free( ctx ); } #endif /* MBEDTLS_ECDSA_C */