crypto: ecrdsa - add EC-RDSA (GOST 34.10) algorithm

Add Elliptic Curve Russian Digital Signature Algorithm (GOST R
34.10-2012, RFC 7091, ISO/IEC 14888-3) is one of the Russian (and since
2018 the CIS countries) cryptographic standard algorithms (called GOST
algorithms). Only signature verification is supported, with intent to be
used in the IMA.

Summary of the changes:

* crypto/Kconfig:
  - EC-RDSA is added into Public-key cryptography section.

* crypto/Makefile:
  - ecrdsa objects are added.

* crypto/asymmetric_keys/x509_cert_parser.c:
  - Recognize EC-RDSA and Streebog OIDs.

* include/linux/oid_registry.h:
  - EC-RDSA OIDs are added to the enum. Also, a two currently not
    implemented curve OIDs are added for possible extension later (to
    not change numbering and grouping).

* crypto/ecc.c:
  - Kenneth MacKay copyright date is updated to 2014, because
    vli_mmod_slow, ecc_point_add, ecc_point_mult_shamir are based on his
    code from micro-ecc.
  - Functions needed for ecrdsa are EXPORT_SYMBOL'ed.
  - New functions:
    vli_is_negative - helper to determine sign of vli;
    vli_from_be64 - unpack big-endian array into vli (used for
      a signature);
    vli_from_le64 - unpack little-endian array into vli (used for
      a public key);
    vli_uadd, vli_usub - add/sub u64 value to/from vli (used for
      increment/decrement);
    mul_64_64 - optimized to use __int128 where appropriate, this speeds
      up point multiplication (and as a consequence signature
      verification) by the factor of 1.5-2;
    vli_umult - multiply vli by a small value (speeds up point
      multiplication by another factor of 1.5-2, depending on vli sizes);
    vli_mmod_special - module reduction for some form of Pseudo-Mersenne
      primes (used for the curves A);
    vli_mmod_special2 - module reduction for another form of
      Pseudo-Mersenne primes (used for the curves B);
    vli_mmod_barrett - module reduction using pre-computed value (used
      for the curve C);
    vli_mmod_slow - more general module reduction which is much slower
     (used when the modulus is subgroup order);
    vli_mod_mult_slow - modular multiplication;
    ecc_point_add - add two points;
    ecc_point_mult_shamir - add two points multiplied by scalars in one
      combined multiplication (this gives speed up by another factor 2 in
      compare to two separate multiplications).
    ecc_is_pubkey_valid_partial - additional samity check is added.
  - Updated vli_mmod_fast with non-strict heuristic to call optimal
      module reduction function depending on the prime value;
  - All computations for the previously defined (two NIST) curves should
    not unaffected.

* crypto/ecc.h:
  - Newly exported functions are documented.

* crypto/ecrdsa_defs.h
  - Five curves are defined.

* crypto/ecrdsa.c:
  - Signature verification is implemented.

* crypto/ecrdsa_params.asn1, crypto/ecrdsa_pub_key.asn1:
  - Templates for BER decoder for EC-RDSA parameters and public key.

Cc: linux-integrity@vger.kernel.org
Signed-off-by: Vitaly Chikunov <vt@altlinux.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 296 insertions, 0 deletions

diff --git a/crypto/ecrdsa.c b/crypto/ecrdsa.c
new file mode 100644
index 000000000000..887ec21aee49
--- /dev/null
+++ b/crypto/ecrdsa.c
@@ -0,0 +1,296 @@
+// 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");