crypto/ecrdsa.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0+
 /*
  * Elliptic Curve (Russian) Digital Signature Algorithm for Cryptographic API
  *
  * Copyright (c) 2019 Vitaly Chikunov <vt@altlinux.org>
  *
  * References:
  * GOST 34.10-2018, GOST R 34.10-2012, RFC 7091, ISO/IEC 14888-3:2018.
  *
  * Historical references:
  * GOST R 34.10-2001, RFC 4357, ISO/IEC 14888-3:2006/Amd 1:2010.
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License as published by the Free
  * Software Foundation; either version 2 of the License, or (at your option)
  * any later version.
  */

 #include <linux/module.h>
 #include <linux/crypto.h>
 #include <crypto/streebog.h>
 #include <crypto/internal/akcipher.h>
 #include <crypto/akcipher.h>
 #include <linux/oid_registry.h>
 #include "ecrdsa_params.asn1.h"
 #include "ecrdsa_pub_key.asn1.h"
 #include "ecc.h"
 #include "ecrdsa_defs.h"

 #define ECRDSA_MAX_SIG_SIZE (2 * 512 / 8)
 #define ECRDSA_MAX_DIGITS (512 / 64)

 struct ecrdsa_ctx {
 	enum OID algo_oid; /* overall public key oid */
 	enum OID curve_oid; /* parameter */
 	enum OID digest_oid; /* parameter */
 	const struct ecc_curve *curve; /* curve from oid */
 	unsigned int digest_len; /* parameter (bytes) */
 	const char *digest; /* digest name from oid */
 	unsigned int key_len; /* @key length (bytes) */
 	const char *key; /* raw public key */
 	struct ecc_point pub_key;
 	u64 _pubp[2][ECRDSA_MAX_DIGITS]; /* point storage for @pub_key */
 };

 static const struct ecc_curve *get_curve_by_oid(enum OID oid)
 {
 	switch (oid) {
 	case OID_gostCPSignA:
 	case OID_gostTC26Sign256B:
 		return &gost_cp256a;
 	case OID_gostCPSignB:
 	case OID_gostTC26Sign256C:
 		return &gost_cp256b;
 	case OID_gostCPSignC:
 	case OID_gostTC26Sign256D:
 		return &gost_cp256c;
 	case OID_gostTC26Sign512A:
 		return &gost_tc512a;
 	case OID_gostTC26Sign512B:
 		return &gost_tc512b;
 	/* The following two aren't implemented: */
 	case OID_gostTC26Sign256A:
 	case OID_gostTC26Sign512C:
 	default:
 		return NULL;
 	}
 }

 static int ecrdsa_verify(struct akcipher_request *req)
 {
 	struct crypto_akcipher *tfm = crypto_akcipher_reqtfm(req);
 	struct ecrdsa_ctx *ctx = akcipher_tfm_ctx(tfm);
 	unsigned char sig[ECRDSA_MAX_SIG_SIZE];
 	unsigned char digest[STREEBOG512_DIGEST_SIZE];
 	unsigned int ndigits = req->dst_len / sizeof(u64);
 	u64 r[ECRDSA_MAX_DIGITS]; /* witness (r) */
 	u64 _r[ECRDSA_MAX_DIGITS]; /* -r */
 	u64 s[ECRDSA_MAX_DIGITS]; /* second part of sig (s) */
 	u64 e[ECRDSA_MAX_DIGITS]; /* h \mod q */
 	u64 *v = e;		  /* e^{-1} \mod q */
 	u64 z1[ECRDSA_MAX_DIGITS];
 	u64 *z2 = _r;
 	struct ecc_point cc = ECC_POINT_INIT(s, e, ndigits); /* reuse s, e */

 	/*
 	 * Digest value, digest algorithm, and curve (modulus) should have the
 	 * same length (256 or 512 bits), public key and signature should be
 	 * twice bigger.
 	 */
 	if (!ctx->curve ||
 	    !ctx->digest ||
 	    !req->src ||
 	    !ctx->pub_key.x ||
 	    req->dst_len != ctx->digest_len ||
 	    req->dst_len != ctx->curve->g.ndigits * sizeof(u64) ||
 	    ctx->pub_key.ndigits != ctx->curve->g.ndigits ||
 	    req->dst_len * 2 != req->src_len ||
 	    WARN_ON(req->src_len > sizeof(sig)) ||
 	    WARN_ON(req->dst_len > sizeof(digest)))
 		return -EBADMSG;

 	sg_copy_to_buffer(req->src, sg_nents_for_len(req->src, req->src_len),
 			  sig, req->src_len);
 	sg_pcopy_to_buffer(req->src,
 			   sg_nents_for_len(req->src,
 					    req->src_len + req->dst_len),
 			   digest, req->dst_len, req->src_len);

 	vli_from_be64(s, sig, ndigits);
 	vli_from_be64(r, sig + ndigits * sizeof(u64), ndigits);

 	/* Step 1: verify that 0 < r < q, 0 < s < q */
 	if (vli_is_zero(r, ndigits) ||
 	    vli_cmp(r, ctx->curve->n, ndigits) == 1 ||
 	    vli_is_zero(s, ndigits) ||
 	    vli_cmp(s, ctx->curve->n, ndigits) == 1)
 		return -EKEYREJECTED;

 	/* Step 2: calculate hash (h) of the message (passed as input) */
 	/* Step 3: calculate e = h \mod q */
 	vli_from_le64(e, digest, ndigits);
 	if (vli_cmp(e, ctx->curve->n, ndigits) == 1)
 		vli_sub(e, e, ctx->curve->n, ndigits);
 	if (vli_is_zero(e, ndigits))
 		e[0] = 1;

 	/* Step 4: calculate v = e^{-1} \mod q */
 	vli_mod_inv(v, e, ctx->curve->n, ndigits);

 	/* Step 5: calculate z_1 = sv \mod q, z_2 = -rv \mod q */
 	vli_mod_mult_slow(z1, s, v, ctx->curve->n, ndigits);
 	vli_sub(_r, ctx->curve->n, r, ndigits);
 	vli_mod_mult_slow(z2, _r, v, ctx->curve->n, ndigits);

 	/* Step 6: calculate point C = z_1P + z_2Q, and R = x_c \mod q */
 	ecc_point_mult_shamir(&cc, z1, &ctx->curve->g, z2, &ctx->pub_key,
 			      ctx->curve);
 	if (vli_cmp(cc.x, ctx->curve->n, ndigits) == 1)
 		vli_sub(cc.x, cc.x, ctx->curve->n, ndigits);

 	/* Step 7: if R == r signature is valid */
 	if (!vli_cmp(cc.x, r, ndigits))
 		return 0;
 	else
 		return -EKEYREJECTED;
 }

 int ecrdsa_param_curve(void *context, size_t hdrlen, unsigned char tag,
 		       const void *value, size_t vlen)
 {
 	struct ecrdsa_ctx *ctx = context;

 	ctx->curve_oid = look_up_OID(value, vlen);
 	if (!ctx->curve_oid)
 		return -EINVAL;
 	ctx->curve = get_curve_by_oid(ctx->curve_oid);
 	return 0;
 }

 /* Optional. If present should match expected digest algo OID. */
 int ecrdsa_param_digest(void *context, size_t hdrlen, unsigned char tag,
 			const void *value, size_t vlen)
 {
 	struct ecrdsa_ctx *ctx = context;
 	int digest_oid = look_up_OID(value, vlen);

 	if (digest_oid != ctx->digest_oid)
 		return -EINVAL;
 	return 0;
 }

 int ecrdsa_parse_pub_key(void *context, size_t hdrlen, unsigned char tag,
 			 const void *value, size_t vlen)
 {
 	struct ecrdsa_ctx *ctx = context;

 	ctx->key = value;
 	ctx->key_len = vlen;
 	return 0;
 }

 static u8 *ecrdsa_unpack_u32(u32 *dst, void *src)
 {
 	memcpy(dst, src, sizeof(u32));
 	return src + sizeof(u32);
 }

 /* Parse BER encoded subjectPublicKey. */
 static int ecrdsa_set_pub_key(struct crypto_akcipher *tfm, const void *key,
 			      unsigned int keylen)
 {
 	struct ecrdsa_ctx *ctx = akcipher_tfm_ctx(tfm);
 	unsigned int ndigits;
 	u32 algo, paramlen;
 	u8 *params;
 	int err;

 	err = asn1_ber_decoder(&ecrdsa_pub_key_decoder, ctx, key, keylen);
 	if (err < 0)
 		return err;

 	/* Key parameters is in the key after keylen. */
 	params = ecrdsa_unpack_u32(&paramlen,
 			  ecrdsa_unpack_u32(&algo, (u8 *)key + keylen));

 	if (algo == OID_gost2012PKey256) {
 		ctx->digest	= "streebog256";
 		ctx->digest_oid	= OID_gost2012Digest256;
 		ctx->digest_len	= 256 / 8;
 	} else if (algo == OID_gost2012PKey512) {
 		ctx->digest	= "streebog512";
 		ctx->digest_oid	= OID_gost2012Digest512;
 		ctx->digest_len	= 512 / 8;
 	} else
 		return -ENOPKG;
 	ctx->algo_oid = algo;

 	/* Parse SubjectPublicKeyInfo.AlgorithmIdentifier.parameters. */
 	err = asn1_ber_decoder(&ecrdsa_params_decoder, ctx, params, paramlen);
 	if (err < 0)
 		return err;
 	/*
 	 * Sizes of algo (set in digest_len) and curve should match
 	 * each other.
 	 */
 	if (!ctx->curve ||
 	    ctx->curve->g.ndigits * sizeof(u64) != ctx->digest_len)
 		return -ENOPKG;
 	/*
 	 * Key is two 256- or 512-bit coordinates which should match
 	 * curve size.
 	 */
 	if ((ctx->key_len != (2 * 256 / 8) &&
 	     ctx->key_len != (2 * 512 / 8)) ||
 	    ctx->key_len != ctx->curve->g.ndigits * sizeof(u64) * 2)
 		return -ENOPKG;

 	ndigits = ctx->key_len / sizeof(u64) / 2;
 	ctx->pub_key = ECC_POINT_INIT(ctx->_pubp[0], ctx->_pubp[1], ndigits);
 	vli_from_le64(ctx->pub_key.x, ctx->key, ndigits);
 	vli_from_le64(ctx->pub_key.y, ctx->key + ndigits * sizeof(u64),
 		      ndigits);

 	if (ecc_is_pubkey_valid_partial(ctx->curve, &ctx->pub_key))
 		return -EKEYREJECTED;

 	return 0;
 }

 static unsigned int ecrdsa_max_size(struct crypto_akcipher *tfm)
 {
 	struct ecrdsa_ctx *ctx = akcipher_tfm_ctx(tfm);

 	/*
 	 * Verify doesn't need any output, so it's just informational
 	 * for keyctl to determine the key bit size.
 	 */
 	return ctx->pub_key.ndigits * sizeof(u64);
 }

 static void ecrdsa_exit_tfm(struct crypto_akcipher *tfm)
 {
 }

 static struct akcipher_alg ecrdsa_alg = {
 	.verify		= ecrdsa_verify,
 	.set_pub_key	= ecrdsa_set_pub_key,
 	.max_size	= ecrdsa_max_size,
 	.exit		= ecrdsa_exit_tfm,
 	.base = {
 		.cra_name	 = "ecrdsa",
 		.cra_driver_name = "ecrdsa-generic",
 		.cra_priority	 = 100,
 		.cra_module	 = THIS_MODULE,
 		.cra_ctxsize	 = sizeof(struct ecrdsa_ctx),
 	},
 };

 static int __init ecrdsa_mod_init(void)
 {
 	return crypto_register_akcipher(&ecrdsa_alg);
 }

 static void __exit ecrdsa_mod_fini(void)
 {
 	crypto_unregister_akcipher(&ecrdsa_alg);
 }

 module_init(ecrdsa_mod_init);
 module_exit(ecrdsa_mod_fini);

 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Vitaly Chikunov <vt@altlinux.org>");
 MODULE_DESCRIPTION("EC-RDSA generic algorithm");
 MODULE_ALIAS_CRYPTO("ecrdsa-generic");
	// SPDX-License-Identifier: GPL-2.0+
	/*
	* Elliptic Curve (Russian) Digital Signature Algorithm for Cryptographic API
	*
	* Copyright (c) 2019 Vitaly Chikunov <vt@altlinux.org>
	*
	* References:
	* GOST 34.10-2018, GOST R 34.10-2012, RFC 7091, ISO/IEC 14888-3:2018.
	*
	* Historical references:
	* GOST R 34.10-2001, RFC 4357, ISO/IEC 14888-3:2006/Amd 1:2010.
	*
	* This program is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License as published by the Free
	* Software Foundation; either version 2 of the License, or (at your option)
	* any later version.
	*/

	#include <linux/module.h>
	#include <linux/crypto.h>
	#include <crypto/streebog.h>
	#include <crypto/internal/akcipher.h>
	#include <crypto/akcipher.h>
	#include <linux/oid_registry.h>
	#include "ecrdsa_params.asn1.h"
	#include "ecrdsa_pub_key.asn1.h"
	#include "ecc.h"
	#include "ecrdsa_defs.h"

	#define ECRDSA_MAX_SIG_SIZE (2 * 512 / 8)
	#define ECRDSA_MAX_DIGITS (512 / 64)

	struct ecrdsa_ctx {
	enum OID algo_oid; /* overall public key oid */
	enum OID curve_oid; /* parameter */
	enum OID digest_oid; /* parameter */
	const struct ecc_curve curve; / curve from oid */
	unsigned int digest_len; /* parameter (bytes) */
	const char digest; / digest name from oid */
	unsigned int key_len; /* @key length (bytes) */
	const char key; / raw public key */
	struct ecc_point pub_key;
	u64 _pubp[2][ECRDSA_MAX_DIGITS]; /* point storage for @pub_key */
	};

	static const struct ecc_curve *get_curve_by_oid(enum OID oid)
	{
	switch (oid) {
	case OID_gostCPSignA:
	case OID_gostTC26Sign256B:
	return &gost_cp256a;
	case OID_gostCPSignB:
	case OID_gostTC26Sign256C:
	return &gost_cp256b;
	case OID_gostCPSignC:
	case OID_gostTC26Sign256D:
	return &gost_cp256c;
	case OID_gostTC26Sign512A:
	return &gost_tc512a;
	case OID_gostTC26Sign512B:
	return &gost_tc512b;
	/* The following two aren't implemented: */
	case OID_gostTC26Sign256A:
	case OID_gostTC26Sign512C:
	default:
	return NULL;
	}
	}

	static int ecrdsa_verify(struct akcipher_request *req)
	{
	struct crypto_akcipher *tfm = crypto_akcipher_reqtfm(req);
	struct ecrdsa_ctx *ctx = akcipher_tfm_ctx(tfm);
	unsigned char sig[ECRDSA_MAX_SIG_SIZE];
	unsigned char digest[STREEBOG512_DIGEST_SIZE];
	unsigned int ndigits = req->dst_len / sizeof(u64);
	u64 r[ECRDSA_MAX_DIGITS]; /* witness (r) */
	u64 _r[ECRDSA_MAX_DIGITS]; /* -r */
	u64 s[ECRDSA_MAX_DIGITS]; /* second part of sig (s) */
	u64 e[ECRDSA_MAX_DIGITS]; /* h \mod q */
	u64 v = e; / e^{-1} \mod q */
	u64 z1[ECRDSA_MAX_DIGITS];
	u64 *z2 = _r;
	struct ecc_point cc = ECC_POINT_INIT(s, e, ndigits); /* reuse s, e */

	/*
	* Digest value, digest algorithm, and curve (modulus) should have the
	* same length (256 or 512 bits), public key and signature should be
	* twice bigger.
	*/
	if (!ctx->curve \|\|
	!ctx->digest \|\|
	!req->src \|\|
	!ctx->pub_key.x \|\|
	req->dst_len != ctx->digest_len \|\|
	req->dst_len != ctx->curve->g.ndigits * sizeof(u64) \|\|
	ctx->pub_key.ndigits != ctx->curve->g.ndigits \|\|
	req->dst_len * 2 != req->src_len \|\|
	WARN_ON(req->src_len > sizeof(sig)) \|\|
	WARN_ON(req->dst_len > sizeof(digest)))
	return -EBADMSG;

	sg_copy_to_buffer(req->src, sg_nents_for_len(req->src, req->src_len),
	sig, req->src_len);
	sg_pcopy_to_buffer(req->src,
	sg_nents_for_len(req->src,
	req->src_len + req->dst_len),
	digest, req->dst_len, req->src_len);

	vli_from_be64(s, sig, ndigits);
	vli_from_be64(r, sig + ndigits * sizeof(u64), ndigits);

	/* Step 1: verify that 0 < r < q, 0 < s < q */
	if (vli_is_zero(r, ndigits) \|\|
	vli_cmp(r, ctx->curve->n, ndigits) == 1 \|\|
	vli_is_zero(s, ndigits) \|\|
	vli_cmp(s, ctx->curve->n, ndigits) == 1)
	return -EKEYREJECTED;

	/* Step 2: calculate hash (h) of the message (passed as input) */
	/* Step 3: calculate e = h \mod q */
	vli_from_le64(e, digest, ndigits);
	if (vli_cmp(e, ctx->curve->n, ndigits) == 1)
	vli_sub(e, e, ctx->curve->n, ndigits);
	if (vli_is_zero(e, ndigits))
	e[0] = 1;

	/* Step 4: calculate v = e^{-1} \mod q */
	vli_mod_inv(v, e, ctx->curve->n, ndigits);

	/* Step 5: calculate z_1 = sv \mod q, z_2 = -rv \mod q */
	vli_mod_mult_slow(z1, s, v, ctx->curve->n, ndigits);
	vli_sub(_r, ctx->curve->n, r, ndigits);
	vli_mod_mult_slow(z2, _r, v, ctx->curve->n, ndigits);

	/* Step 6: calculate point C = z_1P + z_2Q, and R = x_c \mod q */
	ecc_point_mult_shamir(&cc, z1, &ctx->curve->g, z2, &ctx->pub_key,
	ctx->curve);
	if (vli_cmp(cc.x, ctx->curve->n, ndigits) == 1)
	vli_sub(cc.x, cc.x, ctx->curve->n, ndigits);

	/* Step 7: if R == r signature is valid */
	if (!vli_cmp(cc.x, r, ndigits))
	return 0;
	else
	return -EKEYREJECTED;
	}

	int ecrdsa_param_curve(void *context, size_t hdrlen, unsigned char tag,
	const void *value, size_t vlen)
	{
	struct ecrdsa_ctx *ctx = context;

	ctx->curve_oid = look_up_OID(value, vlen);
	if (!ctx->curve_oid)
	return -EINVAL;
	ctx->curve = get_curve_by_oid(ctx->curve_oid);
	return 0;
	}

	/* Optional. If present should match expected digest algo OID. */
	int ecrdsa_param_digest(void *context, size_t hdrlen, unsigned char tag,
	const void *value, size_t vlen)
	{
	struct ecrdsa_ctx *ctx = context;
	int digest_oid = look_up_OID(value, vlen);

	if (digest_oid != ctx->digest_oid)
	return -EINVAL;
	return 0;
	}

	int ecrdsa_parse_pub_key(void *context, size_t hdrlen, unsigned char tag,
	const void *value, size_t vlen)
	{
	struct ecrdsa_ctx *ctx = context;

	ctx->key = value;
	ctx->key_len = vlen;
	return 0;
	}

	static u8 ecrdsa_unpack_u32(u32 dst, void *src)
	{
	memcpy(dst, src, sizeof(u32));
	return src + sizeof(u32);
	}

	/* Parse BER encoded subjectPublicKey. */
	static int ecrdsa_set_pub_key(struct crypto_akcipher tfm, const void key,
	unsigned int keylen)
	{
	struct ecrdsa_ctx *ctx = akcipher_tfm_ctx(tfm);
	unsigned int ndigits;
	u32 algo, paramlen;
	u8 *params;
	int err;

	err = asn1_ber_decoder(&ecrdsa_pub_key_decoder, ctx, key, keylen);
	if (err < 0)
	return err;

	/* Key parameters is in the key after keylen. */
	params = ecrdsa_unpack_u32(&paramlen,
	ecrdsa_unpack_u32(&algo, (u8 *)key + keylen));

	if (algo == OID_gost2012PKey256) {
	ctx->digest = "streebog256";
	ctx->digest_oid = OID_gost2012Digest256;
	ctx->digest_len = 256 / 8;
	} else if (algo == OID_gost2012PKey512) {
	ctx->digest = "streebog512";
	ctx->digest_oid = OID_gost2012Digest512;
	ctx->digest_len = 512 / 8;
	} else
	return -ENOPKG;
	ctx->algo_oid = algo;

	/* Parse SubjectPublicKeyInfo.AlgorithmIdentifier.parameters. */
	err = asn1_ber_decoder(&ecrdsa_params_decoder, ctx, params, paramlen);
	if (err < 0)
	return err;
	/*
	* Sizes of algo (set in digest_len) and curve should match
	* each other.
	*/
	if (!ctx->curve \|\|
	ctx->curve->g.ndigits * sizeof(u64) != ctx->digest_len)
	return -ENOPKG;
	/*
	* Key is two 256- or 512-bit coordinates which should match
	* curve size.
	*/
	if ((ctx->key_len != (2 * 256 / 8) &&
	ctx->key_len != (2 * 512 / 8)) \|\|
	ctx->key_len != ctx->curve->g.ndigits * sizeof(u64) * 2)
	return -ENOPKG;

	ndigits = ctx->key_len / sizeof(u64) / 2;
	ctx->pub_key = ECC_POINT_INIT(ctx->_pubp[0], ctx->_pubp[1], ndigits);
	vli_from_le64(ctx->pub_key.x, ctx->key, ndigits);
	vli_from_le64(ctx->pub_key.y, ctx->key + ndigits * sizeof(u64),
	ndigits);

	if (ecc_is_pubkey_valid_partial(ctx->curve, &ctx->pub_key))
	return -EKEYREJECTED;

	return 0;
	}

	static unsigned int ecrdsa_max_size(struct crypto_akcipher *tfm)
	{
	struct ecrdsa_ctx *ctx = akcipher_tfm_ctx(tfm);

	/*
	* Verify doesn't need any output, so it's just informational
	* for keyctl to determine the key bit size.
	*/
	return ctx->pub_key.ndigits * sizeof(u64);
	}

	static void ecrdsa_exit_tfm(struct crypto_akcipher *tfm)
	{
	}

	static struct akcipher_alg ecrdsa_alg = {
	.verify = ecrdsa_verify,
	.set_pub_key = ecrdsa_set_pub_key,
	.max_size = ecrdsa_max_size,
	.exit = ecrdsa_exit_tfm,
	.base = {
	.cra_name = "ecrdsa",
	.cra_driver_name = "ecrdsa-generic",
	.cra_priority = 100,
	.cra_module = THIS_MODULE,
	.cra_ctxsize = sizeof(struct ecrdsa_ctx),
	},
	};

	static int __init ecrdsa_mod_init(void)
	{
	return crypto_register_akcipher(&ecrdsa_alg);
	}

	static void __exit ecrdsa_mod_fini(void)
	{
	crypto_unregister_akcipher(&ecrdsa_alg);
	}

	module_init(ecrdsa_mod_init);
	module_exit(ecrdsa_mod_fini);

	MODULE_LICENSE("GPL");
	MODULE_AUTHOR("Vitaly Chikunov <vt@altlinux.org>");
	MODULE_DESCRIPTION("EC-RDSA generic algorithm");
	MODULE_ALIAS_CRYPTO("ecrdsa-generic");