blob: 114e6adf1031aaa80ecff71ff841a32f5d6fd52c [file] [log] [blame]
/*
* Copyright (c) 2015-2021, Arm Limited and Contributors. All rights reserved.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
#include <assert.h>
#include <stddef.h>
#include <string.h>
/* mbed TLS headers */
#include <mbedtls/gcm.h>
#include <mbedtls/md.h>
#include <mbedtls/memory_buffer_alloc.h>
#include <mbedtls/oid.h>
#include <mbedtls/platform.h>
#include <mbedtls/x509.h>
#include <common/debug.h>
#include <drivers/auth/crypto_mod.h>
#include <drivers/auth/mbedtls/mbedtls_common.h>
#include <drivers/auth/mbedtls/mbedtls_config.h>
#include <plat/common/platform.h>
#define LIB_NAME "mbed TLS"
#if MEASURED_BOOT
/*
* CRYPTO_MD_MAX_SIZE value is as per current stronger algorithm available
* so make sure that mbed TLS MD maximum size must be lesser than this.
*/
CASSERT(CRYPTO_MD_MAX_SIZE >= MBEDTLS_MD_MAX_SIZE,
assert_mbedtls_md_size_overflow);
#endif /* MEASURED_BOOT */
/*
* AlgorithmIdentifier ::= SEQUENCE {
* algorithm OBJECT IDENTIFIER,
* parameters ANY DEFINED BY algorithm OPTIONAL
* }
*
* SubjectPublicKeyInfo ::= SEQUENCE {
* algorithm AlgorithmIdentifier,
* subjectPublicKey BIT STRING
* }
*
* DigestInfo ::= SEQUENCE {
* digestAlgorithm AlgorithmIdentifier,
* digest OCTET STRING
* }
*/
/*
* Initialize the library and export the descriptor
*/
static void init(void)
{
/* Initialize mbed TLS */
mbedtls_init();
}
/*
* Verify a signature.
*
* Parameters are passed using the DER encoding format following the ASN.1
* structures detailed above.
*/
static int verify_signature(void *data_ptr, unsigned int data_len,
void *sig_ptr, unsigned int sig_len,
void *sig_alg, unsigned int sig_alg_len,
void *pk_ptr, unsigned int pk_len)
{
mbedtls_asn1_buf sig_oid, sig_params;
mbedtls_asn1_buf signature;
mbedtls_md_type_t md_alg;
mbedtls_pk_type_t pk_alg;
mbedtls_pk_context pk = {0};
int rc;
void *sig_opts = NULL;
const mbedtls_md_info_t *md_info;
unsigned char *p, *end;
unsigned char hash[MBEDTLS_MD_MAX_SIZE];
/* Get pointers to signature OID and parameters */
p = (unsigned char *)sig_alg;
end = (unsigned char *)(p + sig_alg_len);
rc = mbedtls_asn1_get_alg(&p, end, &sig_oid, &sig_params);
if (rc != 0) {
return CRYPTO_ERR_SIGNATURE;
}
/* Get the actual signature algorithm (MD + PK) */
rc = mbedtls_x509_get_sig_alg(&sig_oid, &sig_params, &md_alg, &pk_alg, &sig_opts);
if (rc != 0) {
return CRYPTO_ERR_SIGNATURE;
}
/* Parse the public key */
mbedtls_pk_init(&pk);
p = (unsigned char *)pk_ptr;
end = (unsigned char *)(p + pk_len);
rc = mbedtls_pk_parse_subpubkey(&p, end, &pk);
if (rc != 0) {
rc = CRYPTO_ERR_SIGNATURE;
goto end2;
}
/* Get the signature (bitstring) */
p = (unsigned char *)sig_ptr;
end = (unsigned char *)(p + sig_len);
signature.tag = *p;
rc = mbedtls_asn1_get_bitstring_null(&p, end, &signature.len);
if (rc != 0) {
rc = CRYPTO_ERR_SIGNATURE;
goto end1;
}
signature.p = p;
/* Calculate the hash of the data */
md_info = mbedtls_md_info_from_type(md_alg);
if (md_info == NULL) {
rc = CRYPTO_ERR_SIGNATURE;
goto end1;
}
p = (unsigned char *)data_ptr;
rc = mbedtls_md(md_info, p, data_len, hash);
if (rc != 0) {
rc = CRYPTO_ERR_SIGNATURE;
goto end1;
}
/* Verify the signature */
rc = mbedtls_pk_verify_ext(pk_alg, sig_opts, &pk, md_alg, hash,
mbedtls_md_get_size(md_info),
signature.p, signature.len);
if (rc != 0) {
rc = CRYPTO_ERR_SIGNATURE;
goto end1;
}
/* Signature verification success */
rc = CRYPTO_SUCCESS;
end1:
mbedtls_pk_free(&pk);
end2:
mbedtls_free(sig_opts);
return rc;
}
/*
* Match a hash
*
* Digest info is passed in DER format following the ASN.1 structure detailed
* above.
*/
static int verify_hash(void *data_ptr, unsigned int data_len,
void *digest_info_ptr, unsigned int digest_info_len)
{
mbedtls_asn1_buf hash_oid, params;
mbedtls_md_type_t md_alg;
const mbedtls_md_info_t *md_info;
unsigned char *p, *end, *hash;
unsigned char data_hash[MBEDTLS_MD_MAX_SIZE];
size_t len;
int rc;
/* Digest info should be an MBEDTLS_ASN1_SEQUENCE */
p = (unsigned char *)digest_info_ptr;
end = p + digest_info_len;
rc = mbedtls_asn1_get_tag(&p, end, &len, MBEDTLS_ASN1_CONSTRUCTED |
MBEDTLS_ASN1_SEQUENCE);
if (rc != 0) {
return CRYPTO_ERR_HASH;
}
/* Get the hash algorithm */
rc = mbedtls_asn1_get_alg(&p, end, &hash_oid, &params);
if (rc != 0) {
return CRYPTO_ERR_HASH;
}
rc = mbedtls_oid_get_md_alg(&hash_oid, &md_alg);
if (rc != 0) {
return CRYPTO_ERR_HASH;
}
md_info = mbedtls_md_info_from_type(md_alg);
if (md_info == NULL) {
return CRYPTO_ERR_HASH;
}
/* Hash should be octet string type */
rc = mbedtls_asn1_get_tag(&p, end, &len, MBEDTLS_ASN1_OCTET_STRING);
if (rc != 0) {
return CRYPTO_ERR_HASH;
}
/* Length of hash must match the algorithm's size */
if (len != mbedtls_md_get_size(md_info)) {
return CRYPTO_ERR_HASH;
}
hash = p;
/* Calculate the hash of the data */
p = (unsigned char *)data_ptr;
rc = mbedtls_md(md_info, p, data_len, data_hash);
if (rc != 0) {
return CRYPTO_ERR_HASH;
}
/* Compare values */
rc = memcmp(data_hash, hash, mbedtls_md_get_size(md_info));
if (rc != 0) {
return CRYPTO_ERR_HASH;
}
return CRYPTO_SUCCESS;
}
#if MEASURED_BOOT
/*
* Map a generic crypto message digest algorithm to the corresponding macro used
* by Mbed TLS.
*/
static inline mbedtls_md_type_t md_type(enum crypto_md_algo algo)
{
switch (algo) {
case CRYPTO_MD_SHA512:
return MBEDTLS_MD_SHA512;
case CRYPTO_MD_SHA384:
return MBEDTLS_MD_SHA384;
case CRYPTO_MD_SHA256:
return MBEDTLS_MD_SHA256;
default:
/* Invalid hash algorithm. */
return MBEDTLS_MD_NONE;
}
}
/*
* Calculate a hash
*
* output points to the computed hash
*/
static int calc_hash(enum crypto_md_algo md_algo, void *data_ptr,
unsigned int data_len,
unsigned char output[CRYPTO_MD_MAX_SIZE])
{
const mbedtls_md_info_t *md_info;
md_info = mbedtls_md_info_from_type(md_type(md_algo));
if (md_info == NULL) {
return CRYPTO_ERR_HASH;
}
/*
* Calculate the hash of the data, it is safe to pass the
* 'output' hash buffer pointer considering its size is always
* bigger than or equal to MBEDTLS_MD_MAX_SIZE.
*/
return mbedtls_md(md_info, data_ptr, data_len, output);
}
#endif /* MEASURED_BOOT */
#if TF_MBEDTLS_USE_AES_GCM
/*
* Stack based buffer allocation for decryption operation. It could
* be configured to balance stack usage vs execution speed.
*/
#define DEC_OP_BUF_SIZE 128
static int aes_gcm_decrypt(void *data_ptr, size_t len, const void *key,
unsigned int key_len, const void *iv,
unsigned int iv_len, const void *tag,
unsigned int tag_len)
{
mbedtls_gcm_context ctx;
mbedtls_cipher_id_t cipher = MBEDTLS_CIPHER_ID_AES;
unsigned char buf[DEC_OP_BUF_SIZE];
unsigned char tag_buf[CRYPTO_MAX_TAG_SIZE];
unsigned char *pt = data_ptr;
size_t dec_len;
int diff, i, rc;
mbedtls_gcm_init(&ctx);
rc = mbedtls_gcm_setkey(&ctx, cipher, key, key_len * 8);
if (rc != 0) {
rc = CRYPTO_ERR_DECRYPTION;
goto exit_gcm;
}
rc = mbedtls_gcm_starts(&ctx, MBEDTLS_GCM_DECRYPT, iv, iv_len, NULL, 0);
if (rc != 0) {
rc = CRYPTO_ERR_DECRYPTION;
goto exit_gcm;
}
while (len > 0) {
dec_len = MIN(sizeof(buf), len);
rc = mbedtls_gcm_update(&ctx, dec_len, pt, buf);
if (rc != 0) {
rc = CRYPTO_ERR_DECRYPTION;
goto exit_gcm;
}
memcpy(pt, buf, dec_len);
pt += dec_len;
len -= dec_len;
}
rc = mbedtls_gcm_finish(&ctx, tag_buf, sizeof(tag_buf));
if (rc != 0) {
rc = CRYPTO_ERR_DECRYPTION;
goto exit_gcm;
}
/* Check tag in "constant-time" */
for (diff = 0, i = 0; i < tag_len; i++)
diff |= ((const unsigned char *)tag)[i] ^ tag_buf[i];
if (diff != 0) {
rc = CRYPTO_ERR_DECRYPTION;
goto exit_gcm;
}
/* GCM decryption success */
rc = CRYPTO_SUCCESS;
exit_gcm:
mbedtls_gcm_free(&ctx);
return rc;
}
/*
* Authenticated decryption of an image
*/
static int auth_decrypt(enum crypto_dec_algo dec_algo, void *data_ptr,
size_t len, const void *key, unsigned int key_len,
unsigned int key_flags, const void *iv,
unsigned int iv_len, const void *tag,
unsigned int tag_len)
{
int rc;
assert((key_flags & ENC_KEY_IS_IDENTIFIER) == 0);
switch (dec_algo) {
case CRYPTO_GCM_DECRYPT:
rc = aes_gcm_decrypt(data_ptr, len, key, key_len, iv, iv_len,
tag, tag_len);
if (rc != 0)
return rc;
break;
default:
return CRYPTO_ERR_DECRYPTION;
}
return CRYPTO_SUCCESS;
}
#endif /* TF_MBEDTLS_USE_AES_GCM */
/*
* Register crypto library descriptor
*/
#if MEASURED_BOOT
#if TF_MBEDTLS_USE_AES_GCM
REGISTER_CRYPTO_LIB(LIB_NAME, init, verify_signature, verify_hash, calc_hash,
auth_decrypt);
#else
REGISTER_CRYPTO_LIB(LIB_NAME, init, verify_signature, verify_hash, calc_hash,
NULL);
#endif
#else /* MEASURED_BOOT */
#if TF_MBEDTLS_USE_AES_GCM
REGISTER_CRYPTO_LIB(LIB_NAME, init, verify_signature, verify_hash,
auth_decrypt);
#else
REGISTER_CRYPTO_LIB(LIB_NAME, init, verify_signature, verify_hash, NULL);
#endif
#endif /* MEASURED_BOOT */