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[crypto] Add support for ECDSA signatures
Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown
@@ -0,0 +1,928 @@
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/*
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* Copyright (C) 2025 Michael Brown <mbrown@fensystems.co.uk>.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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* 02110-1301, USA.
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*
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* You can also choose to distribute this program under the terms of
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* the Unmodified Binary Distribution Licence (as given in the file
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* COPYING.UBDL), provided that you have satisfied its requirements.
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*/
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FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
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/** @file
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*
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* Elliptic curve digital signature algorithm (ECDSA)
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*
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* The elliptic curve public key format is documented in RFC 5480.
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* The original private key format is documented in RFC 5915, and the
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* generic container PKCS#8 format documented in RFC 5208.
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*
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*/
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#include <stdlib.h>
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#include <errno.h>
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#include <string.h>
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#include <ipxe/crypto.h>
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#include <ipxe/bigint.h>
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#include <ipxe/hmac_drbg.h>
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#include <ipxe/ecdsa.h>
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/* Disambiguate the various error causes */
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#define EINVAL_POINTSIZE \
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__einfo_error ( EINFO_EINVAL_POINTSIZE )
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#define EINFO_EINVAL_POINTSIZE \
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__einfo_uniqify ( EINFO_EINVAL, 0x01, "Invalid point size" )
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#define EINVAL_KEYSIZE \
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__einfo_error ( EINFO_EINVAL_KEYSIZE )
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#define EINFO_EINVAL_KEYSIZE \
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__einfo_uniqify ( EINFO_EINVAL, 0x02, "Invalid key size" )
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#define EINVAL_COMPRESSION \
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__einfo_error ( EINFO_EINVAL_COMPRESSION )
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#define EINFO_EINVAL_COMPRESSION \
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__einfo_uniqify ( EINFO_EINVAL, 0x03, "Invalid compression")
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#define EINVAL_INFINITY \
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__einfo_error ( EINFO_EINVAL_INFINITY )
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#define EINFO_EINVAL_INFINITY \
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__einfo_uniqify ( EINFO_EINVAL, 0x04, "Point is infinity" )
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#define EINVAL_SIGNATURE \
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__einfo_error ( EINFO_EINVAL_SIGNATURE )
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#define EINFO_EINVAL_SIGNATURE \
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__einfo_uniqify ( EINFO_EINVAL, 0x05, "Invalid signature" )
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/** An ECDSA key */
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struct ecdsa_key {
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/** Elliptic curve */
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struct elliptic_curve *curve;
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/** Public curve point */
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const void *public;
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/** Private multiple of base curve point (if applicable) */
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const void *private;
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};
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/** ECDSA context */
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struct ecdsa_context {
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/** Key */
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struct ecdsa_key key;
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/** Big integer size */
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unsigned int size;
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/** Digest algorithm */
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struct digest_algorithm *digest;
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/** Digest length */
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size_t zlen;
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/** Dynamically allocated storage */
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void *dynamic;
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/** Element 0 of modulus N (i.e. curve group order */
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bigint_element_t *modulus0;
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/** Element 0 of constant N-2 (for Fermat's little theorem) */
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bigint_element_t *fermat0;
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/** Element 0 of Montgomery constant R^2 mod N */
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bigint_element_t *square0;
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/** Element 0 of constant 1 (in Montgomery form) */
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bigint_element_t *one0;
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/** Element 0 of digest value "z" */
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bigint_element_t *z0;
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/** Element 0 of random key "k" */
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bigint_element_t *k0;
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/** Element 0 of signature value "r" */
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bigint_element_t *r0;
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/** Element 0 of signature value "s" */
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bigint_element_t *s0;
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/** Element 0 of temporary value */
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bigint_element_t *temp0;
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/** Element 0 of product buffer */
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bigint_element_t *product0;
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/** Curve point 1 */
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void *point1;
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/** Curve point 2 */
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void *point2;
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/** Scalar value */
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void *scalar;
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/** HMAC_DRBG state for random value generation */
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struct hmac_drbg_state *drbg;
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};
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/**
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* Parse ECDSA key
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*
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* @v key ECDSA key
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* @v raw ASN.1 cursor
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* @ret rc Return status code
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*/
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static int ecdsa_parse_key ( struct ecdsa_key *key,
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const struct asn1_cursor *raw ) {
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struct asn1_algorithm *algorithm;
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struct asn1_cursor cursor;
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struct asn1_cursor curve;
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struct asn1_cursor private;
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const uint8_t *compression;
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int is_private;
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int rc;
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/* Enter subjectPublicKeyInfo/ECPrivateKey */
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memcpy ( &cursor, raw, sizeof ( cursor ) );
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asn1_enter ( &cursor, ASN1_SEQUENCE );
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asn1_invalidate_cursor ( &curve );
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asn1_invalidate_cursor ( &private );
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/* Determine key format */
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if ( asn1_type ( &cursor ) == ASN1_INTEGER ) {
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/* Private key */
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is_private = 1;
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/* Skip version */
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asn1_skip_any ( &cursor );
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/* Parse privateKeyAlgorithm, if present */
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if ( asn1_type ( &cursor ) == ASN1_SEQUENCE ) {
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/* PKCS#8 format */
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DBGC ( key, "ECDSA %p is in PKCS#8 format\n", key );
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/* Parse privateKeyAlgorithm */
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memcpy ( &curve, &cursor, sizeof ( curve ) );
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asn1_skip_any ( &cursor );
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/* Enter privateKey */
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asn1_enter ( &cursor, ASN1_OCTET_STRING );
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/* Enter ECPrivateKey */
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asn1_enter ( &cursor, ASN1_SEQUENCE );
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/* Skip version */
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asn1_skip ( &cursor, ASN1_INTEGER );
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}
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/* Parse privateKey */
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memcpy ( &private, &cursor, sizeof ( private ) );
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asn1_enter ( &private, ASN1_OCTET_STRING );
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asn1_skip_any ( &cursor );
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/* Parse parameters, if present */
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if ( asn1_type ( &cursor ) == ASN1_EXPLICIT_TAG ( 0 ) ) {
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memcpy ( &curve, &cursor, sizeof ( curve ) );
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asn1_enter_any ( &curve );
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asn1_skip_any ( &cursor );
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}
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/* Enter publicKey */
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asn1_enter ( &cursor, ASN1_EXPLICIT_TAG ( 1 ) );
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} else {
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/* Public key */
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is_private = 0;
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/* Parse algorithm */
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memcpy ( &curve, &cursor, sizeof ( curve ) );
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asn1_skip_any ( &cursor );
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}
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/* Enter publicKey */
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asn1_enter_bits ( &cursor, NULL );
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/* Identify curve */
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if ( ( rc = asn1_curve_algorithm ( &curve, &algorithm ) ) != 0 ) {
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DBGC ( key, "ECDSA %p unknown curve: %s\n",
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key, strerror ( rc ) );
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DBGC_HDA ( key, 0, raw->data, raw->len );
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return rc;
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}
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key->curve = algorithm->curve;
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DBGC ( key, "ECDSA %p is a %s (%s) %s key\n", key, algorithm->name,
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key->curve->name, ( is_private ? "private" : "public" ) );
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/* Check public key length */
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if ( cursor.len != ( sizeof ( *compression ) +
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key->curve->pointsize ) ) {
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DBGC ( key, "ECDSA %p invalid public key length %zd\n",
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key, cursor.len );
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DBGC_HDA ( key, 0, raw->data, raw->len );
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return -EINVAL_POINTSIZE;
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}
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/* Check that key is uncompressed */
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compression = cursor.data;
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if ( *compression != ECDSA_UNCOMPRESSED ) {
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DBGC ( key, "ECDSA %p invalid compression %#02x\n",
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key, *compression );
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DBGC_HDA ( key, 0, raw->data, raw->len );
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return -EINVAL_COMPRESSION;
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}
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/* Extract public curve point */
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key->public = ( cursor.data + sizeof ( *compression ) );
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DBGC ( key, "ECDSA %p public curve point:\n", key );
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DBGC_HDA ( key, 0, key->public, key->curve->pointsize );
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/* Check that public key is not the point at infinity */
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if ( elliptic_is_infinity ( key->curve, key->public ) ) {
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DBGC ( key, "ECDSA %p public curve point is infinity\n", key );
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return -EINVAL_INFINITY;
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}
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/* Extract private key, if applicable */
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if ( is_private ) {
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/* Check private key length */
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if ( private.len != key->curve->keysize ) {
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DBGC ( key, "ECDSA %p invalid private key length "
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"%zd\n", key, private.len );
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DBGC_HDA ( key, 0, raw->data, raw->len );
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return -EINVAL_KEYSIZE;
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}
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/* Extract private key */
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key->private = private.data;
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DBGC ( key, "ECDSA %p private multiplier:\n", key );
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DBGC_HDA ( key, 0, key->private, key->curve->keysize );
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} else {
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/* No private key */
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key->private = NULL;
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}
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return 0;
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}
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/**
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* Parse ECDSA signature value
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*
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* @v ctx ECDSA context
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* @v rs0 Element 0 of signature "r" or "s" value
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* @v raw ASN.1 cursor
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* @ret rc Return status code
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*/
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static int ecdsa_parse_signature ( struct ecdsa_context *ctx,
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bigint_element_t *rs0,
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const struct asn1_cursor *raw ) {
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size_t keysize = ctx->key.curve->keysize;
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unsigned int size = ctx->size;
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bigint_t ( size ) __attribute__ (( may_alias )) *modulus =
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( ( void * ) ctx->modulus0 );
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bigint_t ( size ) __attribute__ (( may_alias )) *rs =
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( ( void * ) rs0 );
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struct asn1_cursor cursor;
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int rc;
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/* Enter integer */
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memcpy ( &cursor, raw, sizeof ( cursor ) );
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if ( ( rc = asn1_enter_unsigned ( &cursor ) ) != 0 ) {
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DBGC ( ctx, "ECDSA %p invalid integer:\n", ctx );
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DBGC_HDA ( ctx, 0, raw->data, raw->len );
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return rc;
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}
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/* Extract value */
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if ( cursor.len > keysize ) {
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DBGC ( ctx, "ECDSA %p invalid signature value:\n", ctx );
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DBGC_HDA ( ctx, 0, raw->data, raw->len );
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return -EINVAL_KEYSIZE;
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}
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bigint_init ( rs, cursor.data, cursor.len );
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/* Check that value is within the required range */
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if ( bigint_is_zero ( rs ) || bigint_is_geq ( rs, modulus ) ) {
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DBGC ( ctx, "ECDSA %p out-of-range signature value:\n", ctx );
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DBGC_HDA ( ctx, 0, raw->data, raw->len );
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return -ERANGE;
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}
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return 0;
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}
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/**
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* Prepend ECDSA signature value
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*
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* @v ctx ECDSA context
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* @v rs0 Element 0 of signature "r" or "s" value
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* @v builder ASN.1 builder
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* @ret rc Return status code
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*/
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static int ecdsa_prepend_signature ( struct ecdsa_context *ctx,
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bigint_element_t *rs0,
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struct asn1_builder *builder ) {
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size_t keysize = ctx->key.curve->keysize;
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unsigned int size = ctx->size;
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bigint_t ( size ) __attribute__ (( may_alias )) *rs =
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( ( void * ) rs0 );
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uint8_t buf[ 1 /* potential sign byte */ + keysize ];
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uint8_t *data;
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size_t len;
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int rc;
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/* Construct value */
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buf[0] = 0;
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bigint_done ( rs, &buf[1], keysize );
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/* Strip leading zeros */
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data = buf;
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len = sizeof ( buf );
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while ( ( len > 1 ) && ( data[0] == 0 ) && ( data[1] < 0x80 ) ) {
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data++;
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len--;
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}
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/* Prepend integer */
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if ( ( rc = asn1_prepend ( builder, ASN1_INTEGER, data, len ) ) != 0 )
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return rc;
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return 0;
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}
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/**
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* Allocate ECDSA context dynamic storage
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*
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* @v ctx ECDSA context
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* @ret rc Return status code
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*/
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static int ecdsa_alloc ( struct ecdsa_context *ctx ) {
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struct elliptic_curve *curve = ctx->key.curve;
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size_t pointsize = curve->pointsize;
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size_t keysize = curve->keysize;
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unsigned int size =
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bigint_required_size ( keysize + 1 /* for addition */ );
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struct {
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bigint_t ( size ) modulus;
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bigint_t ( size ) fermat;
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bigint_t ( size ) square;
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bigint_t ( size ) one;
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bigint_t ( size ) z;
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bigint_t ( size ) k;
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bigint_t ( size ) r;
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bigint_t ( size ) s;
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bigint_t ( size ) temp;
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bigint_t ( size * 2 ) product;
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uint8_t point1[pointsize];
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uint8_t point2[pointsize];
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uint8_t scalar[keysize];
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struct hmac_drbg_state drbg;
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} *dynamic;
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/* Allocate dynamic storage */
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dynamic = malloc ( sizeof ( *dynamic ) );
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if ( ! dynamic )
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return -ENOMEM;
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/* Populate context */
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ctx->size = size;
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ctx->dynamic = dynamic;
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ctx->modulus0 = dynamic->modulus.element;
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ctx->fermat0 = dynamic->fermat.element;
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ctx->square0 = dynamic->square.element;
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ctx->one0 = dynamic->one.element;
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ctx->z0 = dynamic->z.element;
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ctx->k0 = dynamic->k.element;
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ctx->r0 = dynamic->r.element;
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ctx->s0 = dynamic->s.element;
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ctx->temp0 = dynamic->temp.element;
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ctx->product0 = dynamic->product.element;
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ctx->point1 = dynamic->point1;
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ctx->point2 = dynamic->point2;
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ctx->scalar = dynamic->scalar;
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ctx->drbg = &dynamic->drbg;
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return 0;
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}
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/**
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* Free ECDSA context dynamic storage
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*
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* @v ctx ECDSA context
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*/
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static void ecdsa_free ( struct ecdsa_context *ctx ) {
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/* Free dynamic storage */
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free ( ctx->dynamic );
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}
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/**
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* Initialise ECDSA values
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*
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* @v ctx ECDSA context
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* @v digest Digest algorithm
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* @v value Digest value
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*/
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static void ecdsa_init_values ( struct ecdsa_context *ctx,
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struct digest_algorithm *digest,
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const void *value ) {
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struct elliptic_curve *curve = ctx->key.curve;
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unsigned int size = ctx->size;
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bigint_t ( size ) __attribute__ (( may_alias )) *modulus =
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( ( void * ) ctx->modulus0 );
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bigint_t ( size ) __attribute__ (( may_alias )) *fermat =
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( ( void * ) ctx->fermat0 );
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bigint_t ( size ) __attribute__ (( may_alias )) *square =
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( ( void * ) ctx->square0 );
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bigint_t ( size ) __attribute__ (( may_alias )) *one =
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( ( void * ) ctx->one0 );
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bigint_t ( size ) __attribute__ (( may_alias )) *z =
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( ( void * ) ctx->z0 );
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bigint_t ( size * 2 ) __attribute__ (( may_alias )) *product =
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( ( void * ) ctx->product0 );
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static const uint8_t two_raw[] = { 2 };
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size_t zlen;
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/* Initialise modulus N */
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bigint_init ( modulus, curve->order, curve->keysize );
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DBGC2 ( ctx, "ECDSA %p N = %s\n", ctx, bigint_ntoa ( modulus ) );
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/* Calculate N-2 (using Montgomery constant as temporary buffer) */
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bigint_copy ( modulus, fermat );
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bigint_init ( square, two_raw, sizeof ( two_raw ) );
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bigint_subtract ( square, fermat );
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/* Calculate Montgomery constant */
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bigint_reduce ( modulus, square );
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DBGC2 ( ctx, "ECDSA %p R^2 = %s mod N\n",
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ctx, bigint_ntoa ( square ) );
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/* Construct one in Montgomery form */
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bigint_grow ( square, product );
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bigint_montgomery ( modulus, product, one );
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DBGC2 ( ctx, "ECDSA %p R = %s mod N\n",
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ctx, bigint_ntoa ( one ) );
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/* Initialise digest */
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ctx->digest = digest;
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zlen = ctx->key.curve->keysize;
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if ( zlen > digest->digestsize )
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zlen = digest->digestsize;
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ctx->zlen = zlen;
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bigint_init ( z, value, zlen );
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DBGC2 ( ctx, "ECDSA %p z = %s (%s)\n",
|
||||
ctx, bigint_ntoa ( z ), digest->name );
|
||||
}
|
||||
|
||||
/**
|
||||
* Initialise ECDSA context
|
||||
*
|
||||
* @v ctx ECDSA context
|
||||
* @v key Key
|
||||
* @v digest Digest algorithm
|
||||
* @v value Digest value
|
||||
* @ret rc Return status code
|
||||
*/
|
||||
static int ecdsa_init ( struct ecdsa_context *ctx,
|
||||
const struct asn1_cursor *key,
|
||||
struct digest_algorithm *digest,
|
||||
const void *value ) {
|
||||
int rc;
|
||||
|
||||
/* Parse key */
|
||||
if ( ( rc = ecdsa_parse_key ( &ctx->key, key ) ) != 0 )
|
||||
goto err_parse;
|
||||
|
||||
/* Allocate dynamic storage */
|
||||
if ( ( rc = ecdsa_alloc ( ctx ) ) != 0 )
|
||||
goto err_alloc;
|
||||
|
||||
/* Initialise values */
|
||||
ecdsa_init_values ( ctx, digest, value );
|
||||
|
||||
return 0;
|
||||
|
||||
ecdsa_free ( ctx );
|
||||
err_alloc:
|
||||
err_parse:
|
||||
return rc;
|
||||
}
|
||||
|
||||
/**
|
||||
* Invert ECDSA value
|
||||
*
|
||||
* @v ctx ECDSA context
|
||||
* @v val0 Element 0 of value to invert
|
||||
*/
|
||||
static void ecdsa_invert ( struct ecdsa_context *ctx,
|
||||
bigint_element_t *val0 ) {
|
||||
unsigned int size = ctx->size;
|
||||
bigint_t ( size ) __attribute__ (( may_alias )) *modulus =
|
||||
( ( void * ) ctx->modulus0 );
|
||||
bigint_t ( size ) __attribute__ (( may_alias )) *fermat =
|
||||
( ( void * ) ctx->fermat0 );
|
||||
bigint_t ( size ) __attribute__ (( may_alias )) *square =
|
||||
( ( void * ) ctx->square0 );
|
||||
bigint_t ( size ) __attribute__ (( may_alias )) *one =
|
||||
( ( void * ) ctx->one0 );
|
||||
bigint_t ( size ) __attribute__ (( may_alias )) *temp =
|
||||
( ( void * ) ctx->temp0 );
|
||||
bigint_t ( size * 2 ) __attribute__ (( may_alias )) *product =
|
||||
( ( void * ) ctx->product0 );
|
||||
bigint_t ( size ) __attribute__ (( may_alias )) *val =
|
||||
( ( void * ) val0 );
|
||||
|
||||
/* Convert value to Montgomery form */
|
||||
bigint_multiply ( val, square, product );
|
||||
bigint_montgomery ( modulus, product, temp );
|
||||
|
||||
/* Invert value via Fermat's little theorem */
|
||||
bigint_copy ( one, val );
|
||||
bigint_ladder ( val, temp, fermat, bigint_mod_exp_ladder, modulus,
|
||||
product );
|
||||
}
|
||||
|
||||
/**
|
||||
* Generate ECDSA "r" and "s" values
|
||||
*
|
||||
* @v ctx ECDSA context
|
||||
* @v sig Signature
|
||||
* @ret rc Return status code
|
||||
*/
|
||||
static int ecdsa_sign_rs ( struct ecdsa_context *ctx ) {
|
||||
struct digest_algorithm *digest = ctx->digest;
|
||||
struct elliptic_curve *curve = ctx->key.curve;
|
||||
size_t pointsize = curve->pointsize;
|
||||
size_t keysize = curve->keysize;
|
||||
unsigned int size = ctx->size;
|
||||
bigint_t ( size ) __attribute__ (( may_alias )) *modulus =
|
||||
( ( void * ) ctx->modulus0 );
|
||||
bigint_t ( size ) __attribute__ (( may_alias )) *square =
|
||||
( ( void * ) ctx->square0 );
|
||||
bigint_t ( size ) __attribute__ (( may_alias )) *one =
|
||||
( ( void * ) ctx->one0 );
|
||||
bigint_t ( size ) __attribute__ (( may_alias )) *z =
|
||||
( ( void * ) ctx->z0 );
|
||||
bigint_t ( size ) __attribute__ (( may_alias )) *k =
|
||||
( ( void * ) ctx->k0 );
|
||||
bigint_t ( size ) __attribute__ (( may_alias )) *r =
|
||||
( ( void * ) ctx->r0 );
|
||||
bigint_t ( size ) __attribute__ (( may_alias )) *s =
|
||||
( ( void * ) ctx->s0 );
|
||||
bigint_t ( size ) __attribute__ (( may_alias )) *temp =
|
||||
( ( void * ) ctx->temp0 );
|
||||
bigint_t ( size * 2 ) __attribute__ (( may_alias )) *product =
|
||||
( ( void * ) ctx->product0 );
|
||||
bigint_t ( size ) __attribute__ (( may_alias )) *x1 =
|
||||
( ( void * ) temp );
|
||||
void *point1 = ctx->point1;
|
||||
void *scalar = ctx->scalar;
|
||||
int rc;
|
||||
|
||||
/* Loop until a suitable signature is generated */
|
||||
while ( 1 ) {
|
||||
|
||||
/* Generate pseudo-random data */
|
||||
if ( ( rc = hmac_drbg_generate ( digest, ctx->drbg, NULL, 0,
|
||||
scalar, keysize ) ) != 0 ) {
|
||||
DBGC ( ctx, "ECDSA %p could not generate: %s\n",
|
||||
ctx, strerror ( rc ) );
|
||||
return rc;
|
||||
}
|
||||
|
||||
/* Check suitability of pseudo-random data */
|
||||
bigint_init ( k, scalar, keysize );
|
||||
DBGC2 ( ctx, "ECDSA %p k = %s\n",
|
||||
ctx, bigint_ntoa ( k ) );
|
||||
if ( bigint_is_zero ( k ) )
|
||||
continue;
|
||||
if ( bigint_is_geq ( k, modulus ) )
|
||||
continue;
|
||||
|
||||
/* Calculate (x1,y1) = k*G */
|
||||
elliptic_multiply ( curve, curve->base, scalar, point1 );
|
||||
bigint_init ( x1, point1, ( pointsize / 2 ) );
|
||||
DBGC2 ( ctx, "ECDSA %p x1 = %s mod N\n",
|
||||
ctx, bigint_ntoa ( x1 ) );
|
||||
|
||||
/* Calculate r = x1 mod N */
|
||||
bigint_multiply ( x1, one, product );
|
||||
bigint_montgomery ( modulus, product, r );
|
||||
DBGC2 ( ctx, "ECDSA %p r = %s\n",
|
||||
ctx, bigint_ntoa ( r ) );
|
||||
|
||||
/* Check suitability of r */
|
||||
if ( bigint_is_zero ( r ) )
|
||||
continue;
|
||||
|
||||
/* Calculate k^-1 mod N (in Montgomery form) */
|
||||
ecdsa_invert ( ctx, k->element );
|
||||
DBGC2 ( ctx, "ECDSA %p (k^-1)R = %s mod N\n",
|
||||
ctx, bigint_ntoa ( k ) );
|
||||
|
||||
/* Calculate r * dA */
|
||||
bigint_init ( temp, ctx->key.private, keysize );
|
||||
DBGC2 ( ctx, "ECDSA %p dA = %s\n",
|
||||
ctx, bigint_ntoa ( temp ) );
|
||||
bigint_multiply ( r, temp, product );
|
||||
bigint_montgomery ( modulus, product, temp );
|
||||
bigint_multiply ( temp, square, product );
|
||||
bigint_montgomery ( modulus, product, temp );
|
||||
DBGC2 ( ctx, "ECDSA %p r*dA = %s mod N\n",
|
||||
ctx, bigint_ntoa ( temp ) );
|
||||
|
||||
/* Calculate k^-1 * (z + r*dA) */
|
||||
bigint_add ( z, temp );
|
||||
DBGC2 ( ctx, "ECDSA %p z+r*dA = %s mod N\n",
|
||||
ctx, bigint_ntoa ( temp ) );
|
||||
bigint_multiply ( k, temp, product );
|
||||
bigint_montgomery ( modulus, product, s );
|
||||
DBGC2 ( ctx, "ECDSA %p s = %s\n",
|
||||
ctx, bigint_ntoa ( s ) );
|
||||
|
||||
/* Check suitability of s */
|
||||
if ( bigint_is_zero ( s ) )
|
||||
continue;
|
||||
|
||||
return 0;
|
||||
}
|
||||
}
|
||||
|
||||
/**
|
||||
* Verify ECDSA "r" and "s" values
|
||||
*
|
||||
* @v ctx ECDSA context
|
||||
* @v sig Signature
|
||||
* @ret rc Return status code
|
||||
*/
|
||||
static int ecdsa_verify_rs ( struct ecdsa_context *ctx ) {
|
||||
struct elliptic_curve *curve = ctx->key.curve;
|
||||
size_t pointsize = curve->pointsize;
|
||||
size_t keysize = curve->keysize;
|
||||
const void *public = ctx->key.public;
|
||||
unsigned int size = ctx->size;
|
||||
bigint_t ( size ) __attribute__ (( may_alias )) *modulus =
|
||||
( ( void * ) ctx->modulus0 );
|
||||
bigint_t ( size ) __attribute__ (( may_alias )) *one =
|
||||
( ( void * ) ctx->one0 );
|
||||
bigint_t ( size ) __attribute__ (( may_alias )) *z =
|
||||
( ( void * ) ctx->z0 );
|
||||
bigint_t ( size ) __attribute__ (( may_alias )) *r =
|
||||
( ( void * ) ctx->r0 );
|
||||
bigint_t ( size ) __attribute__ (( may_alias )) *s =
|
||||
( ( void * ) ctx->s0 );
|
||||
bigint_t ( size ) __attribute__ (( may_alias )) *temp =
|
||||
( ( void * ) ctx->temp0 );
|
||||
bigint_t ( size * 2 ) __attribute__ (( may_alias )) *product =
|
||||
( ( void * ) ctx->product0 );
|
||||
bigint_t ( size ) __attribute__ (( may_alias )) *u1 =
|
||||
( ( void * ) temp );
|
||||
bigint_t ( size ) __attribute__ (( may_alias )) *u2 =
|
||||
( ( void * ) temp );
|
||||
bigint_t ( size ) __attribute__ (( may_alias )) *x1 =
|
||||
( ( void * ) temp );
|
||||
void *point1 = ctx->point1;
|
||||
void *point2 = ctx->point2;
|
||||
void *scalar = ctx->scalar;
|
||||
int valid;
|
||||
int rc;
|
||||
|
||||
DBGC2 ( ctx, "ECDSA %p r = %s\n", ctx, bigint_ntoa ( r ) );
|
||||
DBGC2 ( ctx, "ECDSA %p s = %s\n", ctx, bigint_ntoa ( s ) );
|
||||
|
||||
/* Calculate s^-1 mod N (in Montgomery form) */
|
||||
ecdsa_invert ( ctx, s->element );
|
||||
DBGC2 ( ctx, "ECDSA %p (s^-1)R = %s mod N\n", ctx, bigint_ntoa ( s ) );
|
||||
|
||||
/* Calculate u1 = (z * s^-1) mod N */
|
||||
bigint_multiply ( z, s, product );
|
||||
bigint_montgomery ( modulus, product, u1 );
|
||||
DBGC2 ( ctx, "ECDSA %p u1 = %s mod N\n",
|
||||
ctx, bigint_ntoa ( u1 ) );
|
||||
bigint_done ( u1, scalar, keysize );
|
||||
|
||||
/* Calculate u1 * G */
|
||||
if ( ( rc = elliptic_multiply ( curve, curve->base, scalar,
|
||||
point1 ) ) != 0 ) {
|
||||
DBGC ( ctx, "ECDSA %p could not calculate u1*G: %s\n",
|
||||
ctx, strerror ( rc ) );
|
||||
return rc;
|
||||
}
|
||||
|
||||
/* Calculate u2 = (r * s^-1) mod N */
|
||||
bigint_multiply ( r, s, product );
|
||||
bigint_montgomery ( modulus, product, u2 );
|
||||
bigint_done ( u2, scalar, keysize );
|
||||
DBGC2 ( ctx, "ECDSA %p u2 = %s mod N\n",
|
||||
ctx, bigint_ntoa ( u2 ) );
|
||||
|
||||
/* Calculate u2 * Qa */
|
||||
if ( ( rc = elliptic_multiply ( curve, public, scalar,
|
||||
point2 ) ) != 0 ) {
|
||||
DBGC ( ctx, "ECDSA %p could not calculate u2*Qa: %s\n",
|
||||
ctx, strerror ( rc ) );
|
||||
return rc;
|
||||
}
|
||||
|
||||
/* Calculate u1 * G + u2 * Qa */
|
||||
if ( ( rc = elliptic_add ( curve, point1, point2, point1 ) ) != 0 ) {
|
||||
DBGC ( ctx, "ECDSA %p could not calculate u1*G+u2*Qa: %s\n",
|
||||
ctx, strerror ( rc ) );
|
||||
return rc;
|
||||
}
|
||||
|
||||
/* Check that result is not the point at infinity */
|
||||
if ( elliptic_is_infinity ( curve, point1 ) ) {
|
||||
DBGC ( ctx, "ECDSA %p result is point at infinity\n", ctx );
|
||||
return -EINVAL;
|
||||
}
|
||||
|
||||
/* Calculate x1 mod N */
|
||||
bigint_init ( x1, point1, ( pointsize / 2 ) );
|
||||
DBGC2 ( ctx, "ECDSA %p x1 = %s mod N\n", ctx, bigint_ntoa ( x1 ) );
|
||||
bigint_multiply ( x1, one, product );
|
||||
bigint_montgomery ( modulus, product, x1 );
|
||||
DBGC2 ( ctx, "ECDSA %p x1 = %s\n", ctx, bigint_ntoa ( x1 ) );
|
||||
|
||||
/* Check signature */
|
||||
bigint_subtract ( x1, r );
|
||||
valid = bigint_is_zero ( r );
|
||||
DBGC2 ( ctx, "ECDSA %p signature is%s valid\n",
|
||||
ctx, ( valid ? "" : " not" ) );
|
||||
|
||||
return ( valid ? 0 : -EINVAL_SIGNATURE );
|
||||
}
|
||||
|
||||
/**
|
||||
* Encrypt using ECDSA
|
||||
*
|
||||
* @v key Key
|
||||
* @v plaintext Plaintext
|
||||
* @v ciphertext Ciphertext
|
||||
* @ret rc Return status code
|
||||
*/
|
||||
static int ecdsa_encrypt ( const struct asn1_cursor *key __unused,
|
||||
const struct asn1_cursor *plaintext __unused,
|
||||
struct asn1_builder *ciphertext __unused ) {
|
||||
|
||||
/* Not a defined operation for ECDSA */
|
||||
return -ENOTTY;
|
||||
}
|
||||
|
||||
/**
|
||||
* Decrypt using ECDSA
|
||||
*
|
||||
* @v key Key
|
||||
* @v ciphertext Ciphertext
|
||||
* @v plaintext Plaintext
|
||||
* @ret rc Return status code
|
||||
*/
|
||||
static int ecdsa_decrypt ( const struct asn1_cursor *key __unused,
|
||||
const struct asn1_cursor *ciphertext __unused,
|
||||
struct asn1_builder *plaintext __unused ) {
|
||||
|
||||
/* Not a defined operation for ECDSA */
|
||||
return -ENOTTY;
|
||||
}
|
||||
|
||||
/**
|
||||
* Sign digest value using ECDSA
|
||||
*
|
||||
* @v key Key
|
||||
* @v digest Digest algorithm
|
||||
* @v value Digest value
|
||||
* @v signature Signature
|
||||
* @ret rc Return status code
|
||||
*/
|
||||
static int ecdsa_sign ( const struct asn1_cursor *key,
|
||||
struct digest_algorithm *digest, const void *value,
|
||||
struct asn1_builder *signature ) {
|
||||
struct ecdsa_context ctx;
|
||||
int rc;
|
||||
|
||||
/* Initialise context */
|
||||
if ( ( rc = ecdsa_init ( &ctx, key, digest, value ) ) != 0 )
|
||||
goto err_init;
|
||||
|
||||
/* Fail unless we have a private key */
|
||||
if ( ! ctx.key.private ) {
|
||||
rc = -ENOTTY;
|
||||
goto err_no_key;
|
||||
}
|
||||
|
||||
/* Instantiate DRBG */
|
||||
hmac_drbg_instantiate ( digest, ctx.drbg, ctx.key.private,
|
||||
ctx.key.curve->keysize, value, ctx.zlen );
|
||||
|
||||
/* Create signature */
|
||||
if ( ( rc = ecdsa_sign_rs ( &ctx ) ) != 0 )
|
||||
goto err_signature;
|
||||
|
||||
/* Construct "r" and "s" values */
|
||||
if ( ( rc = ecdsa_prepend_signature ( &ctx, ctx.s0, signature ) ) != 0)
|
||||
goto err_s;
|
||||
if ( ( rc = ecdsa_prepend_signature ( &ctx, ctx.r0, signature ) ) != 0)
|
||||
goto err_r;
|
||||
if ( ( rc = asn1_wrap ( signature, ASN1_SEQUENCE ) ) != 0 )
|
||||
goto err_wrap;
|
||||
|
||||
/* Free context */
|
||||
ecdsa_free ( &ctx );
|
||||
|
||||
return 0;
|
||||
|
||||
err_wrap:
|
||||
err_r:
|
||||
err_s:
|
||||
err_signature:
|
||||
err_no_key:
|
||||
ecdsa_free ( &ctx );
|
||||
err_init:
|
||||
return rc;
|
||||
}
|
||||
|
||||
/**
|
||||
* Verify signed digest using ECDSA
|
||||
*
|
||||
* @v key Key
|
||||
* @v digest Digest algorithm
|
||||
* @v value Digest value
|
||||
* @v signature Signature
|
||||
* @ret rc Return status code
|
||||
*/
|
||||
static int ecdsa_verify ( const struct asn1_cursor *key,
|
||||
struct digest_algorithm *digest, const void *value,
|
||||
const struct asn1_cursor *signature ) {
|
||||
struct ecdsa_context ctx;
|
||||
struct asn1_cursor cursor;
|
||||
int rc;
|
||||
|
||||
/* Initialise context */
|
||||
if ( ( rc = ecdsa_init ( &ctx, key, digest, value ) ) != 0 )
|
||||
goto err_init;
|
||||
|
||||
/* Enter sequence */
|
||||
memcpy ( &cursor, signature, sizeof ( cursor ) );
|
||||
asn1_enter ( &cursor, ASN1_SEQUENCE );
|
||||
|
||||
/* Extract "r" and "s" values */
|
||||
if ( ( rc = ecdsa_parse_signature ( &ctx, ctx.r0, &cursor ) ) != 0 )
|
||||
goto err_r;
|
||||
asn1_skip_any ( &cursor );
|
||||
if ( ( rc = ecdsa_parse_signature ( &ctx, ctx.s0, &cursor ) ) != 0 )
|
||||
goto err_s;
|
||||
|
||||
/* Verify signature */
|
||||
if ( ( rc = ecdsa_verify_rs ( &ctx ) ) != 0 )
|
||||
goto err_verify;
|
||||
|
||||
/* Free context */
|
||||
ecdsa_free ( &ctx );
|
||||
|
||||
return 0;
|
||||
|
||||
err_verify:
|
||||
err_s:
|
||||
err_r:
|
||||
ecdsa_free ( &ctx );
|
||||
err_init:
|
||||
return rc;
|
||||
}
|
||||
|
||||
/**
|
||||
* Check for matching ECDSA public/private key pair
|
||||
*
|
||||
* @v private_key Private key
|
||||
* @v public_key Public key
|
||||
* @ret rc Return status code
|
||||
*/
|
||||
static int ecdsa_match ( const struct asn1_cursor *private_key,
|
||||
const struct asn1_cursor *public_key ) {
|
||||
struct elliptic_curve *curve;
|
||||
struct ecdsa_key privkey;
|
||||
struct ecdsa_key pubkey;
|
||||
int rc;
|
||||
|
||||
/* Parse keys */
|
||||
if ( ( rc = ecdsa_parse_key ( &privkey, private_key ) ) != 0 )
|
||||
return rc;
|
||||
if ( ( rc = ecdsa_parse_key ( &pubkey, public_key ) ) != 0 )
|
||||
return rc;
|
||||
|
||||
/* Compare curves */
|
||||
if ( privkey.curve != pubkey.curve )
|
||||
return -ENOTTY;
|
||||
curve = privkey.curve;
|
||||
|
||||
/* Compare public curve points */
|
||||
if ( memcmp ( privkey.public, pubkey.public, curve->pointsize ) != 0 )
|
||||
return -ENOTTY;
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
/** ECDSA public-key algorithm */
|
||||
struct pubkey_algorithm ecdsa_algorithm = {
|
||||
.name = "ecdsa",
|
||||
.encrypt = ecdsa_encrypt,
|
||||
.decrypt = ecdsa_decrypt,
|
||||
.sign = ecdsa_sign,
|
||||
.verify = ecdsa_verify,
|
||||
.match = ecdsa_match,
|
||||
};
|
||||
Reference in New Issue
Block a user