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linux/crypto/rsassa-pkcs1.c
Lukas Wunner 221f00418e crypto: sig - Rename crypto_sig_maxsize() to crypto_sig_keysize() 
crypto_sig_maxsize() is a bit of a misnomer as it doesn't return the
maximum signature size, but rather the key size.

Rename it as well as all implementations of the ->max_size callback.
A subsequent commit introduces a crypto_sig_maxsize() function which
returns the actual maximum signature size.

While at it, change the return type of crypto_sig_keysize() from int to
unsigned int for consistency with crypto_akcipher_maxsize().  None of
the callers checks for a negative return value and an error condition
can always be indicated by returning zero.

Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2024-10-05 13:22:04 +08:00

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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* RSA Signature Scheme with Appendix - PKCS #1 v1.5 (RFC 8017 sec 8.2)
*
* https://www.rfc-editor.org/rfc/rfc8017#section-8.2
*
* Copyright (c) 2015 - 2024 Intel Corporation
*/
#include <linux/module.h>
#include <linux/scatterlist.h>
#include <crypto/akcipher.h>
#include <crypto/algapi.h>
#include <crypto/hash.h>
#include <crypto/sig.h>
#include <crypto/internal/akcipher.h>
#include <crypto/internal/rsa.h>
#include <crypto/internal/sig.h>
/*
* Full Hash Prefix for EMSA-PKCS1-v1_5 encoding method (RFC 9580 table 24)
*
* RSA keys are usually much larger than the hash of the message to be signed.
* The hash is therefore prepended by the Full Hash Prefix and a 0xff padding.
* The Full Hash Prefix is an ASN.1 SEQUENCE containing the hash algorithm OID.
*
* https://www.rfc-editor.org/rfc/rfc9580#table-24
*/
static const u8 hash_prefix_md5[] = {
0x30, 0x20, 0x30, 0x0c, 0x06, 0x08, /* SEQUENCE (SEQUENCE (OID */
0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x02, 0x05, /* <algorithm>, */
0x05, 0x00, 0x04, 0x10 /* NULL), OCTET STRING <hash>) */
};
static const u8 hash_prefix_sha1[] = {
0x30, 0x21, 0x30, 0x09, 0x06, 0x05,
0x2b, 0x0e, 0x03, 0x02, 0x1a,
0x05, 0x00, 0x04, 0x14
};
static const u8 hash_prefix_rmd160[] = {
0x30, 0x21, 0x30, 0x09, 0x06, 0x05,
0x2b, 0x24, 0x03, 0x02, 0x01,
0x05, 0x00, 0x04, 0x14
};
static const u8 hash_prefix_sha224[] = {
0x30, 0x2d, 0x30, 0x0d, 0x06, 0x09,
0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x04,
0x05, 0x00, 0x04, 0x1c
};
static const u8 hash_prefix_sha256[] = {
0x30, 0x31, 0x30, 0x0d, 0x06, 0x09,
0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01,
0x05, 0x00, 0x04, 0x20
};
static const u8 hash_prefix_sha384[] = {
0x30, 0x41, 0x30, 0x0d, 0x06, 0x09,
0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x02,
0x05, 0x00, 0x04, 0x30
};
static const u8 hash_prefix_sha512[] = {
0x30, 0x51, 0x30, 0x0d, 0x06, 0x09,
0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x03,
0x05, 0x00, 0x04, 0x40
};
static const u8 hash_prefix_sha3_256[] = {
0x30, 0x31, 0x30, 0x0d, 0x06, 0x09,
0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x08,
0x05, 0x00, 0x04, 0x20
};
static const u8 hash_prefix_sha3_384[] = {
0x30, 0x41, 0x30, 0x0d, 0x06, 0x09,
0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x09,
0x05, 0x00, 0x04, 0x30
};
static const u8 hash_prefix_sha3_512[] = {
0x30, 0x51, 0x30, 0x0d, 0x06, 0x09,
0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x0a,
0x05, 0x00, 0x04, 0x40
};
static const struct hash_prefix {
const char *name;
const u8 *data;
size_t size;
} hash_prefixes[] = {
#define _(X) { #X, hash_prefix_##X, sizeof(hash_prefix_##X) }
_(md5),
_(sha1),
_(rmd160),
_(sha256),
_(sha384),
_(sha512),
_(sha224),
#undef _
#define _(X) { "sha3-" #X, hash_prefix_sha3_##X, sizeof(hash_prefix_sha3_##X) }
_(256),
_(384),
_(512),
#undef _
{ NULL }
};
static const struct hash_prefix *rsassa_pkcs1_find_hash_prefix(const char *name)
{
const struct hash_prefix *p;
for (p = hash_prefixes; p->name; p++)
if (strcmp(name, p->name) == 0)
return p;
return NULL;
}
static unsigned int rsassa_pkcs1_hash_len(const struct hash_prefix *p)
{
/*
* The final byte of the Full Hash Prefix encodes the hash length.
*
* This needs to be revisited should hash algorithms with more than
* 1016 bits (127 bytes * 8) ever be added. The length would then
* be encoded into more than one byte by ASN.1.
*/
static_assert(HASH_MAX_DIGESTSIZE <= 127);
return p->data[p->size - 1];
}
struct rsassa_pkcs1_ctx {
struct crypto_akcipher *child;
unsigned int key_size;
};
struct rsassa_pkcs1_inst_ctx {
struct crypto_akcipher_spawn spawn;
const struct hash_prefix *hash_prefix;
};
static int rsassa_pkcs1_sign(struct crypto_sig *tfm,
const void *src, unsigned int slen,
void *dst, unsigned int dlen)
{
struct sig_instance *inst = sig_alg_instance(tfm);
struct rsassa_pkcs1_inst_ctx *ictx = sig_instance_ctx(inst);
const struct hash_prefix *hash_prefix = ictx->hash_prefix;
struct rsassa_pkcs1_ctx *ctx = crypto_sig_ctx(tfm);
unsigned int child_reqsize = crypto_akcipher_reqsize(ctx->child);
struct akcipher_request *child_req __free(kfree_sensitive) = NULL;
struct scatterlist in_sg[3], out_sg;
struct crypto_wait cwait;
unsigned int pad_len;
unsigned int ps_end;
unsigned int len;
u8 *in_buf;
int err;
if (!ctx->key_size)
return -EINVAL;
if (dlen < ctx->key_size)
return -EOVERFLOW;
if (slen != rsassa_pkcs1_hash_len(hash_prefix))
return -EINVAL;
if (slen + hash_prefix->size > ctx->key_size - 11)
return -EOVERFLOW;
pad_len = ctx->key_size - slen - hash_prefix->size - 1;
child_req = kmalloc(sizeof(*child_req) + child_reqsize + pad_len,
GFP_KERNEL);
if (!child_req)
return -ENOMEM;
/* RFC 8017 sec 8.2.1 step 1 - EMSA-PKCS1-v1_5 encoding generation */
in_buf = (u8 *)(child_req + 1) + child_reqsize;
ps_end = pad_len - 1;
in_buf[0] = 0x01;
memset(in_buf + 1, 0xff, ps_end - 1);
in_buf[ps_end] = 0x00;
/* RFC 8017 sec 8.2.1 step 2 - RSA signature */
crypto_init_wait(&cwait);
sg_init_table(in_sg, 3);
sg_set_buf(&in_sg[0], in_buf, pad_len);
sg_set_buf(&in_sg[1], hash_prefix->data, hash_prefix->size);
sg_set_buf(&in_sg[2], src, slen);
sg_init_one(&out_sg, dst, dlen);
akcipher_request_set_tfm(child_req, ctx->child);
akcipher_request_set_crypt(child_req, in_sg, &out_sg,
ctx->key_size - 1, dlen);
akcipher_request_set_callback(child_req, CRYPTO_TFM_REQ_MAY_SLEEP,
crypto_req_done, &cwait);
err = crypto_akcipher_decrypt(child_req);
err = crypto_wait_req(err, &cwait);
if (err)
return err;
len = child_req->dst_len;
pad_len = ctx->key_size - len;
/* Four billion to one */
if (unlikely(pad_len)) {
memmove(dst + pad_len, dst, len);
memset(dst, 0, pad_len);
}
return 0;
}
static int rsassa_pkcs1_verify(struct crypto_sig *tfm,
const void *src, unsigned int slen,
const void *digest, unsigned int dlen)
{
struct sig_instance *inst = sig_alg_instance(tfm);
struct rsassa_pkcs1_inst_ctx *ictx = sig_instance_ctx(inst);
const struct hash_prefix *hash_prefix = ictx->hash_prefix;
struct rsassa_pkcs1_ctx *ctx = crypto_sig_ctx(tfm);
unsigned int child_reqsize = crypto_akcipher_reqsize(ctx->child);
struct akcipher_request *child_req __free(kfree_sensitive) = NULL;
struct scatterlist in_sg, out_sg;
struct crypto_wait cwait;
unsigned int dst_len;
unsigned int pos;
u8 *out_buf;
int err;
/* RFC 8017 sec 8.2.2 step 1 - length checking */
if (!ctx->key_size ||
slen != ctx->key_size ||
dlen != rsassa_pkcs1_hash_len(hash_prefix))
return -EINVAL;
/* RFC 8017 sec 8.2.2 step 2 - RSA verification */
child_req = kmalloc(sizeof(*child_req) + child_reqsize + ctx->key_size,
GFP_KERNEL);
if (!child_req)
return -ENOMEM;
out_buf = (u8 *)(child_req + 1) + child_reqsize;
crypto_init_wait(&cwait);
sg_init_one(&in_sg, src, slen);
sg_init_one(&out_sg, out_buf, ctx->key_size);
akcipher_request_set_tfm(child_req, ctx->child);
akcipher_request_set_crypt(child_req, &in_sg, &out_sg,
slen, ctx->key_size);
akcipher_request_set_callback(child_req, CRYPTO_TFM_REQ_MAY_SLEEP,
crypto_req_done, &cwait);
err = crypto_akcipher_encrypt(child_req);
err = crypto_wait_req(err, &cwait);
if (err)
return err;
/* RFC 8017 sec 8.2.2 step 3 - EMSA-PKCS1-v1_5 encoding verification */
dst_len = child_req->dst_len;
if (dst_len < ctx->key_size - 1)
return -EINVAL;
if (dst_len == ctx->key_size) {
if (out_buf[0] != 0x00)
/* Encrypted value had no leading 0 byte */
return -EINVAL;
dst_len--;
out_buf++;
}
if (out_buf[0] != 0x01)
return -EBADMSG;
for (pos = 1; pos < dst_len; pos++)
if (out_buf[pos] != 0xff)
break;
if (pos < 9 || pos == dst_len || out_buf[pos] != 0x00)
return -EBADMSG;
pos++;
if (hash_prefix->size > dst_len - pos)
return -EBADMSG;
if (crypto_memneq(out_buf + pos, hash_prefix->data, hash_prefix->size))
return -EBADMSG;
pos += hash_prefix->size;
/* RFC 8017 sec 8.2.2 step 4 - comparison of digest with out_buf */
if (dlen != dst_len - pos)
return -EKEYREJECTED;
if (memcmp(digest, out_buf + pos, dlen) != 0)
return -EKEYREJECTED;
return 0;
}
static unsigned int rsassa_pkcs1_key_size(struct crypto_sig *tfm)
{
struct rsassa_pkcs1_ctx *ctx = crypto_sig_ctx(tfm);
return ctx->key_size;
}
static int rsassa_pkcs1_set_pub_key(struct crypto_sig *tfm,
const void *key, unsigned int keylen)
{
struct rsassa_pkcs1_ctx *ctx = crypto_sig_ctx(tfm);
return rsa_set_key(ctx->child, &ctx->key_size, RSA_PUB, key, keylen);
}
static int rsassa_pkcs1_set_priv_key(struct crypto_sig *tfm,
const void *key, unsigned int keylen)
{
struct rsassa_pkcs1_ctx *ctx = crypto_sig_ctx(tfm);
return rsa_set_key(ctx->child, &ctx->key_size, RSA_PRIV, key, keylen);
}
static int rsassa_pkcs1_init_tfm(struct crypto_sig *tfm)
{
struct sig_instance *inst = sig_alg_instance(tfm);
struct rsassa_pkcs1_inst_ctx *ictx = sig_instance_ctx(inst);
struct rsassa_pkcs1_ctx *ctx = crypto_sig_ctx(tfm);
struct crypto_akcipher *child_tfm;
child_tfm = crypto_spawn_akcipher(&ictx->spawn);
if (IS_ERR(child_tfm))
return PTR_ERR(child_tfm);
ctx->child = child_tfm;
return 0;
}
static void rsassa_pkcs1_exit_tfm(struct crypto_sig *tfm)
{
struct rsassa_pkcs1_ctx *ctx = crypto_sig_ctx(tfm);
crypto_free_akcipher(ctx->child);
}
static void rsassa_pkcs1_free(struct sig_instance *inst)
{
struct rsassa_pkcs1_inst_ctx *ctx = sig_instance_ctx(inst);
struct crypto_akcipher_spawn *spawn = &ctx->spawn;
crypto_drop_akcipher(spawn);
kfree(inst);
}
static int rsassa_pkcs1_create(struct crypto_template *tmpl, struct rtattr **tb)
{
struct rsassa_pkcs1_inst_ctx *ctx;
struct akcipher_alg *rsa_alg;
struct sig_instance *inst;
const char *hash_name;
u32 mask;
int err;
err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SIG, &mask);
if (err)
return err;
inst = kzalloc(sizeof(*inst) + sizeof(*ctx), GFP_KERNEL);
if (!inst)
return -ENOMEM;
ctx = sig_instance_ctx(inst);
err = crypto_grab_akcipher(&ctx->spawn, sig_crypto_instance(inst),
crypto_attr_alg_name(tb[1]), 0, mask);
if (err)
goto err_free_inst;
rsa_alg = crypto_spawn_akcipher_alg(&ctx->spawn);
if (strcmp(rsa_alg->base.cra_name, "rsa") != 0) {
err = -EINVAL;
goto err_free_inst;
}
hash_name = crypto_attr_alg_name(tb[2]);
if (IS_ERR(hash_name)) {
err = PTR_ERR(hash_name);
goto err_free_inst;
}
ctx->hash_prefix = rsassa_pkcs1_find_hash_prefix(hash_name);
if (!ctx->hash_prefix) {
err = -EINVAL;
goto err_free_inst;
}
err = -ENAMETOOLONG;
if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
"pkcs1(%s,%s)", rsa_alg->base.cra_name,
hash_name) >= CRYPTO_MAX_ALG_NAME)
goto err_free_inst;
if (snprintf(inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME,
"pkcs1(%s,%s)", rsa_alg->base.cra_driver_name,
hash_name) >= CRYPTO_MAX_ALG_NAME)
goto err_free_inst;
inst->alg.base.cra_priority = rsa_alg->base.cra_priority;
inst->alg.base.cra_ctxsize = sizeof(struct rsassa_pkcs1_ctx);
inst->alg.init = rsassa_pkcs1_init_tfm;
inst->alg.exit = rsassa_pkcs1_exit_tfm;
inst->alg.sign = rsassa_pkcs1_sign;
inst->alg.verify = rsassa_pkcs1_verify;
inst->alg.key_size = rsassa_pkcs1_key_size;
inst->alg.set_pub_key = rsassa_pkcs1_set_pub_key;
inst->alg.set_priv_key = rsassa_pkcs1_set_priv_key;
inst->free = rsassa_pkcs1_free;
err = sig_register_instance(tmpl, inst);
if (err) {
err_free_inst:
rsassa_pkcs1_free(inst);
}
return err;
}
struct crypto_template rsassa_pkcs1_tmpl = {
.name = "pkcs1",
.create = rsassa_pkcs1_create,
.module = THIS_MODULE,
};
MODULE_ALIAS_CRYPTO("pkcs1");
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