1// SPDX-License-Identifier: GPL-2.0+
  2/*
  3 * ECDSA X9.62 signature encoding
  4 *
  5 * Copyright (c) 2021 IBM Corporation
  6 * Copyright (c) 2024 Intel Corporation
  7 */
  8
  9#include <linux/asn1_decoder.h>
 10#include <linux/err.h>
 11#include <linux/module.h>
 12#include <crypto/algapi.h>
 13#include <crypto/sig.h>
 14#include <crypto/internal/ecc.h>
 15#include <crypto/internal/sig.h>
 16
 17#include "ecdsasignature.asn1.h"
 18
 19struct ecdsa_x962_ctx {
 20	struct crypto_sig *child;
 21};
 22
 23struct ecdsa_x962_signature_ctx {
 24	struct ecdsa_raw_sig sig;
 25	unsigned int ndigits;
 26};
 27
 28/* Get the r and s components of a signature from the X.509 certificate. */
 29static int ecdsa_get_signature_rs(u64 *dest, size_t hdrlen, unsigned char tag,
 30				  const void *value, size_t vlen,
 31				  unsigned int ndigits)
 32{
 33	size_t bufsize = ndigits * sizeof(u64);
 34	const char *d = value;
 35
 36	if (!value || !vlen || vlen > bufsize + 1)
 37		return -EINVAL;
 38
 39	/*
 40	 * vlen may be 1 byte larger than bufsize due to a leading zero byte
 41	 * (necessary if the most significant bit of the integer is set).
 42	 */
 43	if (vlen > bufsize) {
 44		/* skip over leading zeros that make 'value' a positive int */
 45		if (*d == 0) {
 46			vlen -= 1;
 47			d++;
 48		} else {
 49			return -EINVAL;
 50		}
 51	}
 52
 53	ecc_digits_from_bytes(d, vlen, dest, ndigits);
 54
 55	return 0;
 56}
 57
 58int ecdsa_get_signature_r(void *context, size_t hdrlen, unsigned char tag,
 59			  const void *value, size_t vlen)
 60{
 61	struct ecdsa_x962_signature_ctx *sig_ctx = context;
 62
 63	return ecdsa_get_signature_rs(sig_ctx->sig.r, hdrlen, tag, value, vlen,
 64				      sig_ctx->ndigits);
 65}
 66
 67int ecdsa_get_signature_s(void *context, size_t hdrlen, unsigned char tag,
 68			  const void *value, size_t vlen)
 69{
 70	struct ecdsa_x962_signature_ctx *sig_ctx = context;
 71
 72	return ecdsa_get_signature_rs(sig_ctx->sig.s, hdrlen, tag, value, vlen,
 73				      sig_ctx->ndigits);
 74}
 75
 76static int ecdsa_x962_verify(struct crypto_sig *tfm,
 77			     const void *src, unsigned int slen,
 78			     const void *digest, unsigned int dlen)
 79{
 80	struct ecdsa_x962_ctx *ctx = crypto_sig_ctx(tfm);
 81	struct ecdsa_x962_signature_ctx sig_ctx;
 82	int err;
 83
 84	sig_ctx.ndigits = DIV_ROUND_UP(crypto_sig_keysize(ctx->child),
 85				       sizeof(u64));
 86
 87	err = asn1_ber_decoder(&ecdsasignature_decoder, &sig_ctx, src, slen);
 88	if (err < 0)
 89		return err;
 90
 91	return crypto_sig_verify(ctx->child, &sig_ctx.sig, sizeof(sig_ctx.sig),
 92				 digest, dlen);
 93}
 94
 95static unsigned int ecdsa_x962_key_size(struct crypto_sig *tfm)
 96{
 97	struct ecdsa_x962_ctx *ctx = crypto_sig_ctx(tfm);
 98
 99	return crypto_sig_keysize(ctx->child);
100}
101
102static unsigned int ecdsa_x962_max_size(struct crypto_sig *tfm)
103{
104	struct ecdsa_x962_ctx *ctx = crypto_sig_ctx(tfm);
105	struct sig_alg *alg = crypto_sig_alg(ctx->child);
106	int slen = crypto_sig_keysize(ctx->child);
107
108	/*
109	 * Verify takes ECDSA-Sig-Value (described in RFC 5480) as input,
110	 * which is actually 2 'key_size'-bit integers encoded in ASN.1.
111	 * Account for the ASN.1 encoding overhead here.
112	 *
113	 * NIST P192/256/384 may prepend a '0' to a coordinate to indicate
114	 * a positive integer. NIST P521 never needs it.
115	 */
116	if (strcmp(alg->base.cra_name, "ecdsa-nist-p521") != 0)
117		slen += 1;
118
119	/* Length of encoding the x & y coordinates */
120	slen = 2 * (slen + 2);
121
122	/*
123	 * If coordinate encoding takes at least 128 bytes then an
124	 * additional byte for length encoding is needed.
125	 */
126	return 1 + (slen >= 128) + 1 + slen;
127}
128
129static unsigned int ecdsa_x962_digest_size(struct crypto_sig *tfm)
130{
131	struct ecdsa_x962_ctx *ctx = crypto_sig_ctx(tfm);
132
133	return crypto_sig_digestsize(ctx->child);
134}
135
136static int ecdsa_x962_set_pub_key(struct crypto_sig *tfm,
137				  const void *key, unsigned int keylen)
138{
139	struct ecdsa_x962_ctx *ctx = crypto_sig_ctx(tfm);
140
141	return crypto_sig_set_pubkey(ctx->child, key, keylen);
142}
143
144static int ecdsa_x962_init_tfm(struct crypto_sig *tfm)
145{
146	struct sig_instance *inst = sig_alg_instance(tfm);
147	struct crypto_sig_spawn *spawn = sig_instance_ctx(inst);
148	struct ecdsa_x962_ctx *ctx = crypto_sig_ctx(tfm);
149	struct crypto_sig *child_tfm;
150
151	child_tfm = crypto_spawn_sig(spawn);
152	if (IS_ERR(child_tfm))
153		return PTR_ERR(child_tfm);
154
155	ctx->child = child_tfm;
156
157	return 0;
158}
159
160static void ecdsa_x962_exit_tfm(struct crypto_sig *tfm)
161{
162	struct ecdsa_x962_ctx *ctx = crypto_sig_ctx(tfm);
163
164	crypto_free_sig(ctx->child);
165}
166
167static void ecdsa_x962_free(struct sig_instance *inst)
168{
169	struct crypto_sig_spawn *spawn = sig_instance_ctx(inst);
170
171	crypto_drop_sig(spawn);
172	kfree(inst);
173}
174
175static int ecdsa_x962_create(struct crypto_template *tmpl, struct rtattr **tb)
176{
177	struct crypto_sig_spawn *spawn;
178	struct sig_instance *inst;
179	struct sig_alg *ecdsa_alg;
180	u32 mask;
181	int err;
182
183	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SIG, &mask);
184	if (err)
185		return err;
186
187	inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
188	if (!inst)
189		return -ENOMEM;
190
191	spawn = sig_instance_ctx(inst);
192
193	err = crypto_grab_sig(spawn, sig_crypto_instance(inst),
194			      crypto_attr_alg_name(tb[1]), 0, mask);
195	if (err)
196		goto err_free_inst;
197
198	ecdsa_alg = crypto_spawn_sig_alg(spawn);
199
200	err = -EINVAL;
201	if (strncmp(ecdsa_alg->base.cra_name, "ecdsa", 5) != 0)
202		goto err_free_inst;
203
204	err = crypto_inst_setname(sig_crypto_instance(inst), tmpl->name,
205				  &ecdsa_alg->base);
206	if (err)
207		goto err_free_inst;
208
209	inst->alg.base.cra_priority = ecdsa_alg->base.cra_priority;
210	inst->alg.base.cra_ctxsize = sizeof(struct ecdsa_x962_ctx);
211
212	inst->alg.init = ecdsa_x962_init_tfm;
213	inst->alg.exit = ecdsa_x962_exit_tfm;
214
215	inst->alg.verify = ecdsa_x962_verify;
216	inst->alg.key_size = ecdsa_x962_key_size;
217	inst->alg.max_size = ecdsa_x962_max_size;
218	inst->alg.digest_size = ecdsa_x962_digest_size;
219	inst->alg.set_pub_key = ecdsa_x962_set_pub_key;
220
221	inst->free = ecdsa_x962_free;
222
223	err = sig_register_instance(tmpl, inst);
224	if (err) {
225err_free_inst:
226		ecdsa_x962_free(inst);
227	}
228	return err;
229}
230
231struct crypto_template ecdsa_x962_tmpl = {
232	.name = "x962",
233	.create = ecdsa_x962_create,
234	.module = THIS_MODULE,
235};
236
237MODULE_ALIAS_CRYPTO("x962");