crypto: ecdsa - Support P1363 signature decoding

Alternatively to the X9.62 encoding of ecdsa signatures, which uses
ASN.1 and is already supported by the kernel, there's another common
encoding called P1363.  It stores r and s as the concatenation of two
big endian, unsigned integers.  The name originates from IEEE P1363.

Add a P1363 template in support of the forthcoming SPDM library
(Security Protocol and Data Model) for PCI device authentication.

P1363 is prescribed by SPDM 1.2.1 margin no 44:

   "For ECDSA signatures, excluding SM2, in SPDM, the signature shall be
    the concatenation of r and s.  The size of r shall be the size of
    the selected curve.  Likewise, the size of s shall be the size of
    the selected curve.  See BaseAsymAlgo in NEGOTIATE_ALGORITHMS for
    the size of r and s.  The byte order for r and s shall be in big
    endian order.  When placing ECDSA signatures into an SPDM signature
    field, r shall come first followed by s."

Link: https://www.dmtf.org/sites/default/files/standards/documents/DSP0274_1.2.1.pdf
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/Makefile

@@ -55,6 +55,7 @@ $(obj)/ecdsasignature.asn1.o: $(obj)/ecdsasignature.asn1.c $(obj)/ecdsasignature
 $(obj)/ecdsa-x962.o: $(obj)/ecdsasignature.asn1.h
 ecdsa_generic-y += ecdsa.o
 ecdsa_generic-y += ecdsa-x962.o
+ecdsa_generic-y += ecdsa-p1363.o
 ecdsa_generic-y += ecdsasignature.asn1.o
 obj-$(CONFIG_CRYPTO_ECDSA) += ecdsa_generic.o
 

crypto/asymmetric_keys/public_key.c

@@ -110,7 +110,8 @@ software_key_determine_akcipher(const struct public_key *pkey,
 			return -EINVAL;
 		*sig = false;
 	} else if (strncmp(pkey->pkey_algo, "ecdsa", 5) == 0) {
-		if (strcmp(encoding, "x962") != 0)
+		if (strcmp(encoding, "x962") != 0 &&
+		    strcmp(encoding, "p1363") != 0)
 			return -EINVAL;
 		/*
 		 * ECDSA signatures are taken over a raw hash, so they don't

crypto/ecdsa-p1363.c

@@ -0,0 +1,159 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * ECDSA P1363 signature encoding
+ *
+ * Copyright (c) 2024 Intel Corporation
+ */
+
+#include <linux/err.h>
+#include <linux/module.h>
+#include <crypto/algapi.h>
+#include <crypto/sig.h>
+#include <crypto/internal/ecc.h>
+#include <crypto/internal/sig.h>
+
+struct ecdsa_p1363_ctx {
+	struct crypto_sig *child;
+};
+
+static int ecdsa_p1363_verify(struct crypto_sig *tfm,
+			      const void *src, unsigned int slen,
+			      const void *digest, unsigned int dlen)
+{
+	struct ecdsa_p1363_ctx *ctx = crypto_sig_ctx(tfm);
+	unsigned int keylen = crypto_sig_keysize(ctx->child);
+	unsigned int ndigits = DIV_ROUND_UP(keylen, sizeof(u64));
+	struct ecdsa_raw_sig sig;
+
+	if (slen != 2 * keylen)
+		return -EINVAL;
+
+	ecc_digits_from_bytes(src, keylen, sig.r, ndigits);
+	ecc_digits_from_bytes(src + keylen, keylen, sig.s, ndigits);
+
+	return crypto_sig_verify(ctx->child, &sig, sizeof(sig), digest, dlen);
+}
+
+static unsigned int ecdsa_p1363_key_size(struct crypto_sig *tfm)
+{
+	struct ecdsa_p1363_ctx *ctx = crypto_sig_ctx(tfm);
+
+	return crypto_sig_keysize(ctx->child);
+}
+
+static unsigned int ecdsa_p1363_max_size(struct crypto_sig *tfm)
+{
+	struct ecdsa_p1363_ctx *ctx = crypto_sig_ctx(tfm);
+
+	return 2 * crypto_sig_keysize(ctx->child);
+}
+
+static unsigned int ecdsa_p1363_digest_size(struct crypto_sig *tfm)
+{
+	struct ecdsa_p1363_ctx *ctx = crypto_sig_ctx(tfm);
+
+	return crypto_sig_digestsize(ctx->child);
+}
+
+static int ecdsa_p1363_set_pub_key(struct crypto_sig *tfm,
+				   const void *key, unsigned int keylen)
+{
+	struct ecdsa_p1363_ctx *ctx = crypto_sig_ctx(tfm);
+
+	return crypto_sig_set_pubkey(ctx->child, key, keylen);
+}
+
+static int ecdsa_p1363_init_tfm(struct crypto_sig *tfm)
+{
+	struct sig_instance *inst = sig_alg_instance(tfm);
+	struct crypto_sig_spawn *spawn = sig_instance_ctx(inst);
+	struct ecdsa_p1363_ctx *ctx = crypto_sig_ctx(tfm);
+	struct crypto_sig *child_tfm;
+
+	child_tfm = crypto_spawn_sig(spawn);
+	if (IS_ERR(child_tfm))
+		return PTR_ERR(child_tfm);
+
+	ctx->child = child_tfm;
+
+	return 0;
+}
+
+static void ecdsa_p1363_exit_tfm(struct crypto_sig *tfm)
+{
+	struct ecdsa_p1363_ctx *ctx = crypto_sig_ctx(tfm);
+
+	crypto_free_sig(ctx->child);
+}
+
+static void ecdsa_p1363_free(struct sig_instance *inst)
+{
+	struct crypto_sig_spawn *spawn = sig_instance_ctx(inst);
+
+	crypto_drop_sig(spawn);
+	kfree(inst);
+}
+
+static int ecdsa_p1363_create(struct crypto_template *tmpl, struct rtattr **tb)
+{
+	struct crypto_sig_spawn *spawn;
+	struct sig_instance *inst;
+	struct sig_alg *ecdsa_alg;
+	u32 mask;
+	int err;
+
+	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SIG, &mask);
+	if (err)
+		return err;
+
+	inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
+	if (!inst)
+		return -ENOMEM;
+
+	spawn = sig_instance_ctx(inst);
+
+	err = crypto_grab_sig(spawn, sig_crypto_instance(inst),
+			      crypto_attr_alg_name(tb[1]), 0, mask);
+	if (err)
+		goto err_free_inst;
+
+	ecdsa_alg = crypto_spawn_sig_alg(spawn);
+
+	err = -EINVAL;
+	if (strncmp(ecdsa_alg->base.cra_name, "ecdsa", 5) != 0)
+		goto err_free_inst;
+
+	err = crypto_inst_setname(sig_crypto_instance(inst), tmpl->name,
+				  &ecdsa_alg->base);
+	if (err)
+		goto err_free_inst;
+
+	inst->alg.base.cra_priority = ecdsa_alg->base.cra_priority;
+	inst->alg.base.cra_ctxsize = sizeof(struct ecdsa_p1363_ctx);
+
+	inst->alg.init = ecdsa_p1363_init_tfm;
+	inst->alg.exit = ecdsa_p1363_exit_tfm;
+
+	inst->alg.verify = ecdsa_p1363_verify;
+	inst->alg.key_size = ecdsa_p1363_key_size;
+	inst->alg.max_size = ecdsa_p1363_max_size;
+	inst->alg.digest_size = ecdsa_p1363_digest_size;
+	inst->alg.set_pub_key = ecdsa_p1363_set_pub_key;
+
+	inst->free = ecdsa_p1363_free;
+
+	err = sig_register_instance(tmpl, inst);
+	if (err) {
+err_free_inst:
+		ecdsa_p1363_free(inst);
+	}
+	return err;
+}
+
+struct crypto_template ecdsa_p1363_tmpl = {
+	.name = "p1363",
+	.create = ecdsa_p1363_create,
+	.module = THIS_MODULE,
+};
+
+MODULE_ALIAS_CRYPTO("p1363");

crypto/ecdsa.c

@@ -298,8 +298,15 @@ static int __init ecdsa_init(void)
 	if (ret)
 		goto x962_tmpl_error;
 
+	ret = crypto_register_template(&ecdsa_p1363_tmpl);
+	if (ret)
+		goto p1363_tmpl_error;
+
 	return 0;
 
+p1363_tmpl_error:
+	crypto_unregister_template(&ecdsa_x962_tmpl);
+
 x962_tmpl_error:
 	crypto_unregister_sig(&ecdsa_nist_p521);
 
@@ -318,6 +325,7 @@ nist_p256_error:
 static void __exit ecdsa_exit(void)
 {
 	crypto_unregister_template(&ecdsa_x962_tmpl);
+	crypto_unregister_template(&ecdsa_p1363_tmpl);
 
 	if (ecdsa_nist_p192_registered)
 		crypto_unregister_sig(&ecdsa_nist_p192);

crypto/testmgr.c

@@ -5515,6 +5515,24 @@ static const struct alg_test_desc alg_test_descs[] = {
 		.suite = {
 			.hash = __VECS(nhpoly1305_tv_template)
 		}
+	}, {
+		.alg = "p1363(ecdsa-nist-p192)",
+		.test = alg_test_null,
+	}, {
+		.alg = "p1363(ecdsa-nist-p256)",
+		.test = alg_test_sig,
+		.fips_allowed = 1,
+		.suite = {
+			.sig = __VECS(p1363_ecdsa_nist_p256_tv_template)
+		}
+	}, {
+		.alg = "p1363(ecdsa-nist-p384)",
+		.test = alg_test_null,
+		.fips_allowed = 1,
+	}, {
+		.alg = "p1363(ecdsa-nist-p521)",
+		.test = alg_test_null,
+		.fips_allowed = 1,
 	}, {
 		.alg = "pcbc(fcrypt)",
 		.test = alg_test_skcipher,

crypto/testmgr.h

@@ -1805,6 +1805,34 @@ static const struct sig_testvec x962_ecdsa_nist_p521_tv_template[] = {
 	},
 };
 
+/*
+ * ECDSA P1363 test vectors.
+ *
+ * Identical to ECDSA test vectors, except signature in "c" is P1363 encoded.
+ */
+static const struct sig_testvec p1363_ecdsa_nist_p256_tv_template[] = {
+	{
+	.key = /* secp256r1(sha256) */
+	"\x04\xf1\xea\xc4\x53\xf3\xb9\x0e\x9f\x7e\xad\xe3\xea\xd7\x0e\x0f"
+	"\xd6\x98\x9a\xca\x92\x4d\x0a\x80\xdb\x2d\x45\xc7\xec\x4b\x97\x00"
+	"\x2f\xe9\x42\x6c\x29\xdc\x55\x0e\x0b\x53\x12\x9b\x2b\xad\x2c\xe9"
+	"\x80\xe6\xc5\x43\xc2\x1d\x5e\xbb\x65\x21\x50\xb6\x37\xb0\x03\x8e"
+	"\xb8",
+	.key_len = 65,
+	.m =
+	"\x8f\x43\x43\x46\x64\x8f\x6b\x96\xdf\x89\xdd\xa9\x01\xc5\x17\x6b"
+	"\x10\xa6\xd8\x39\x61\xdd\x3c\x1a\xc8\x8b\x59\xb2\xdc\x32\x7a\xa4",
+	.m_size = 32,
+	.c =
+	"\x08\x31\xfa\x74\x0d\x1d\x21\x5d\x09\xdc\x29\x63\xa8\x1a\xad\xfc"
+	"\xac\x44\xc3\xe8\x24\x11\x2d\xa4\x91\xdc\x02\x67\xdc\x0c\xd0\x82"
+	"\xbd\xff\xce\xee\x42\xc3\x97\xff\xf9\xa9\x81\xac\x4a\x50\xd0\x91"
+	"\x0a\x6e\x1b\xc4\xaf\xe1\x83\xc3\x4f\x2a\x65\x35\x23\xe3\x1d\xfa",
+	.c_size = 64,
+	.public_key_vec = true,
+	},
+};
+
 /*
  * EC-RDSA test vectors are generated by gost-engine.
  */

include/crypto/internal/ecc.h

@@ -306,4 +306,5 @@ void ecc_point_mult_shamir(const struct ecc_point *result,
 			   const struct ecc_curve *curve);
 
 extern struct crypto_template ecdsa_x962_tmpl;
+extern struct crypto_template ecdsa_p1363_tmpl;
 #endif