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// SPDX-License-Identifier: GPL-2.0+
/*
* Public key helper functions using MbedTLS X509 library
*
* Copyright (c) 2024 Linaro Limited
* Author: Raymond Mao <raymond.mao@linaro.org>
*/
#include <linux/compat.h>
#include <crypto/public_key.h>
int public_key_verify_signature(const struct public_key *pkey,
const struct public_key_signature *sig)
{
mbedtls_md_type_t mb_hash_algo;
mbedtls_pk_context pk_ctx;
int ret;
if (!pkey || !sig || pkey->key_is_private)
return -EINVAL;
/*
* ECRDSA (Elliptic Curve Russian Digital Signature Algorithm) is not
* supported by MbedTLS.
*/
if (strcmp(pkey->pkey_algo, "rsa")) {
pr_err("Encryption is not RSA: %s\n", sig->pkey_algo);
return -EINVAL;
}
/*
* Can be pkcs1 or raw, but pkcs1 is expected.
* This is just for argument checking, not necessarily passed to MbedTLS,
* For RSA signatures, MbedTLS typically supports the PKCS#1 v1.5
* (aka. pkcs1) encoding by default.
* The library internally handles the details of decoding and verifying
* the signature according to the expected encoding for the specified algorithm.
*/
if (strcmp(sig->encoding, "pkcs1")) {
pr_err("Encoding %s is not supported, only supports pkcs1\n",
sig->encoding);
return -EINVAL;
}
if (!strcmp(sig->hash_algo, "sha1"))
mb_hash_algo = MBEDTLS_MD_SHA1;
else if (!strcmp(sig->hash_algo, "sha224"))
mb_hash_algo = MBEDTLS_MD_SHA224;
else if (!strcmp(sig->hash_algo, "sha256"))
mb_hash_algo = MBEDTLS_MD_SHA256;
else if (!strcmp(sig->hash_algo, "sha384"))
mb_hash_algo = MBEDTLS_MD_SHA384;
else if (!strcmp(sig->hash_algo, "sha512"))
mb_hash_algo = MBEDTLS_MD_SHA512;
else /* Unknown or unsupported hash algorithm */
return -EINVAL;
/* Initialize the mbedtls_pk_context with RSA key type */
mbedtls_pk_init(&pk_ctx);
/* Parse the DER-encoded public key */
ret = mbedtls_pk_parse_public_key(&pk_ctx, pkey->key, pkey->keylen);
if (ret) {
pr_err("Failed to parse public key, ret:-0x%04x\n", -ret);
ret = -EINVAL;
goto err_key;
}
/* Ensure that it is a RSA key */
if (mbedtls_pk_get_type(&pk_ctx) != MBEDTLS_PK_RSA) {
pr_err("Only RSA keys are supported\n");
ret = -EKEYREJECTED;
goto err_key;
}
/* Verify the hash */
ret = mbedtls_pk_verify(&pk_ctx, mb_hash_algo, sig->digest,
sig->digest_size, sig->s, sig->s_size);
err_key:
mbedtls_pk_free(&pk_ctx);
return ret;
}
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