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1df80a4f5f
Add RSA helper layer on top on MbedTLS PK and RSA library. Introduce _LEGACY and _MBEDTLS kconfigs for RSA helper legacy and MbedTLS implementations respectively. Signed-off-by: Raymond Mao <raymond.mao@linaro.org> Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
95 lines
2.3 KiB
C
95 lines
2.3 KiB
C
// SPDX-License-Identifier: GPL-2.0+
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/*
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* RSA helper functions using MbedTLS
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*
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* Copyright (c) 2024 Linaro Limited
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* Author: Raymond Mao <raymond.mao@linaro.org>
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*/
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#include <linux/err.h>
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#include <crypto/internal/rsa.h>
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#include <library/common.h>
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#include <mbedtls/pk.h>
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#include <mbedtls/rsa.h>
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#include <mbedtls/asn1.h>
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/**
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* rsa_parse_pub_key() - decodes the BER encoded buffer and stores in the
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* provided struct rsa_key, pointers to the raw key as is,
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* so that the caller can copy it or MPI parse it, etc.
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*
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* @rsa_key: struct rsa_key key representation
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* @key: key in BER format
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* @key_len: length of key
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*
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* Return: 0 on success or error code in case of error
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*/
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int rsa_parse_pub_key(struct rsa_key *rsa_key, const void *key,
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unsigned int key_len)
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{
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int ret = 0;
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mbedtls_pk_context pk;
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mbedtls_rsa_context *rsa;
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mbedtls_pk_init(&pk);
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ret = mbedtls_pk_parse_public_key(&pk, (const unsigned char *)key,
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key_len);
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if (ret) {
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pr_err("Failed to parse public key, ret:-0x%04x\n", -ret);
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ret = -EINVAL;
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goto clean_pubkey;
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}
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/* Ensure that it is a RSA key */
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if (mbedtls_pk_get_type(&pk) != MBEDTLS_PK_RSA) {
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pr_err("Non-RSA keys are not supported\n");
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ret = -EKEYREJECTED;
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goto clean_pubkey;
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}
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/* Get RSA key context */
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rsa = mbedtls_pk_rsa(pk);
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if (!rsa) {
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pr_err("Failed to get RSA key context, ret:-0x%04x\n", -ret);
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ret = -EINVAL;
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goto clean_pubkey;
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}
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/* Parse modulus (n) */
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rsa_key->n_sz = mbedtls_mpi_size(&rsa->N);
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rsa_key->n = kzalloc(rsa_key->n_sz, GFP_KERNEL);
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if (!rsa_key->n) {
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ret = -ENOMEM;
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goto clean_pubkey;
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}
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ret = mbedtls_mpi_write_binary(&rsa->N, (unsigned char *)rsa_key->n,
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rsa_key->n_sz);
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if (ret) {
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pr_err("Failed to parse modulus (n), ret:-0x%04x\n", -ret);
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ret = -EINVAL;
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goto clean_modulus;
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}
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/* Parse public exponent (e) */
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rsa_key->e_sz = mbedtls_mpi_size(&rsa->E);
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rsa_key->e = kzalloc(rsa_key->e_sz, GFP_KERNEL);
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if (!rsa_key->e) {
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ret = -ENOMEM;
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goto clean_modulus;
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}
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ret = mbedtls_mpi_write_binary(&rsa->E, (unsigned char *)rsa_key->e,
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rsa_key->e_sz);
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if (!ret)
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return 0;
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pr_err("Failed to parse public exponent (e), ret:-0x%04x\n", -ret);
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ret = -EINVAL;
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kfree(rsa_key->e);
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clean_modulus:
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kfree(rsa_key->n);
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clean_pubkey:
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mbedtls_pk_free(&pk);
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return ret;
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}
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