/*
* Copyright (c) 2015-2016, ARM Limited and Contributors. All rights reserved.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
#include <assert.h>
#include <auth_common.h>
#include <auth_mod.h>
#include <cot_def.h>
#include <crypto_mod.h>
#include <debug.h>
#include <img_parser_mod.h>
#include <platform.h>
#include <platform_def.h>
#include <stdint.h>
#include <string.h>
/* ASN.1 tags */
#define ASN1_INTEGER 0x02
#define return_if_error(rc) \
do { \
if (rc != 0) { \
return rc; \
} \
} while (0)
#pragma weak plat_set_nv_ctr2
/* Pointer to CoT */
extern const auth_img_desc_t *const cot_desc_ptr;
extern unsigned int auth_img_flags[];
static int cmp_auth_param_type_desc(const auth_param_type_desc_t *a,
const auth_param_type_desc_t *b)
{
if ((a->type == b->type) && (a->cookie == b->cookie)) {
return 0;
}
return 1;
}
/*
* This function obtains the requested authentication parameter data from the
* information extracted from the parent image after its authentication.
*/
static int auth_get_param(const auth_param_type_desc_t *param_type_desc,
const auth_img_desc_t *img_desc,
void **param, unsigned int *len)
{
int i;
for (i = 0 ; i < COT_MAX_VERIFIED_PARAMS ; i++) {
if (0 == cmp_auth_param_type_desc(param_type_desc,
img_desc->authenticated_data[i].type_desc)) {
*param = img_desc->authenticated_data[i].data.ptr;
*len = img_desc->authenticated_data[i].data.len;
return 0;
}
}
return 1;
}
/*
* Authenticate an image by matching the data hash
*
* This function implements 'AUTH_METHOD_HASH'. To authenticate an image using
* this method, the image must contain:
*
* - The data to calculate the hash from
*
* The parent image must contain:
*
* - The hash to be matched with (including hash algorithm)
*
* For a successful authentication, both hashes must match. The function calls
* the crypto-module to check this matching.
*
* Parameters:
* param: parameters to perform the hash authentication
* img_desc: pointer to image descriptor so we can know the image type
* and parent image
* img: pointer to image in memory
* img_len: length of image (in bytes)
*
* Return:
* 0 = success, Otherwise = error
*/
static int auth_hash(const auth_method_param_hash_t *param,
const auth_img_desc_t *img_desc,
void *img, unsigned int img_len)
{
void *data_ptr, *hash_der_ptr;
unsigned int data_len, hash_der_len;
int rc = 0;
/* Get the hash from the parent image. This hash will be DER encoded
* and contain the hash algorithm */
rc = auth_get_param(param->hash, img_desc->parent,
&hash_der_ptr, &hash_der_len);
return_if_error(rc);
/* Get the data to be hashed from the current image */
rc = img_parser_get_auth_param(img_desc->img_type, param->data,
img, img_len, &data_ptr, &data_len);
return_if_error(rc);
/* Ask the crypto module to verify this hash */
rc = crypto_mod_verify_hash(data_ptr, data_len,
hash_der_ptr, hash_der_len);
return rc;
}
/*
* Authenticate by digital signature
*
* This function implements 'AUTH_METHOD_SIG'. To authenticate an image using
* this method, the image must contain:
*
* - Data to be signed
* - Signature
* - Signature algorithm
*
* We rely on the image parser module to extract this data from the image.
* The parent image must contain:
*
* - Public key (or a hash of it)
*
* If the parent image contains only a hash of the key, we will try to obtain
* the public key from the image itself (i.e. self-signed certificates). In that
* case, the signature verification is considered just an integrity check and
* the authentication is established by calculating the hash of the key and
* comparing it with the hash obtained from the parent.
*
* If the image has no parent (NULL), it means it has to be authenticated using
* the ROTPK stored in the platform. Again, this ROTPK could be the key itself
* or a hash of it.
*
* Return: 0 = success, Otherwise = error
*/
static int auth_signature(const auth_method_param_sig_t *param,
const auth_img_desc_t *img_desc,
void *img, unsigned int img_len)
{
void *data_ptr, *pk_ptr, *pk_hash_ptr, *sig_ptr, *sig_alg_ptr;
unsigned int data_len, pk_len, pk_hash_len, sig_len, sig_alg_len;
unsigned int flags = 0;
int rc = 0;
/* Get the data to be signed from current image */
rc = img_parser_get_auth_param(img_desc->img_type, param->data,
img, img_len, &data_ptr, &data_len);
return_if_error(rc);
/* Get the signature from current image */
rc = img_parser_get_auth_param(img_desc->img_type, param->sig,
img, img_len, &sig_ptr, &sig_len);
return_if_error(rc);
/* Get the signature algorithm from current image */
rc = img_parser_get_auth_param(img_desc->img_type, param->alg,
img, img_len, &sig_alg_ptr, &sig_alg_len);
return_if_error(rc);
/* Get the public key from the parent. If there is no parent (NULL),
* the certificate has been signed with the ROTPK, so we have to get
* the PK from the platform */
if (img_desc->parent) {
rc = auth_get_param(param->pk, img_desc->parent,
&pk_ptr, &pk_len);
} else {
rc = plat_get_rotpk_info(param->pk->cookie, &pk_ptr, &pk_len,
&flags);
}
return_if_error(rc);
if (flags & (ROTPK_IS_HASH | ROTPK_NOT_DEPLOYED)) {
/* If the PK is a hash of the key or if the ROTPK is not
deployed on the platform, retrieve the key from the image */
pk_hash_ptr = pk_ptr;
pk_hash_len = pk_len;
rc = img_parser_get_auth_param(img_desc->img_type,
param->pk, img, img_len,
&pk_ptr, &pk_len);
return_if_error(rc);
/* Ask the crypto module to verify the signature */
rc = crypto_mod_verify_signature(data_ptr, data_len,
sig_ptr, sig_len,
sig_alg_ptr, sig_alg_len,
pk_ptr, pk_len);
return_if_error(rc);
if (flags & ROTPK_NOT_DEPLOYED) {
NOTICE("ROTPK is not deployed on platform. "
"Skipping ROTPK verification.\n");
} else {
/* Ask the crypto-module to verify the key hash */
rc = crypto_mod_verify_hash(pk_ptr, pk_len,
pk_hash_ptr, pk_hash_len);
}
} else {
/* Ask the crypto module to verify the signature */
rc = crypto_mod_verify_signature(data_ptr, data_len,
sig_ptr, sig_len,
sig_alg_ptr, sig_alg_len,
pk_ptr, pk_len);
}
return rc;
}
/*
* Authenticate by Non-Volatile counter
*
* To protect the system against rollback, the platform includes a non-volatile
* counter whose value can only be increased. All certificates include a counter
* value that should not be lower than the value stored in the platform. If the
* value is larger, the counter in the platform must be updated to the new
* value.
*
* Return: 0 = success, Otherwise = error
*/
static int auth_nvctr(const auth_method_param_nv_ctr_t *param,
const auth_img_desc_t *img_desc,
void *img, unsigned int img_len)
{
char *p;
void *data_ptr = NULL;
unsigned int data_len, len, i;
unsigned int cert_nv_ctr, plat_nv_ctr;
int rc = 0;
/* Get the counter value from current image. The AM expects the IPM
* to return the counter value as a DER encoded integer */
rc = img_parser_get_auth_param(img_desc->img_type, param->cert_nv_ctr,
img, img_len, &data_ptr, &data_len);
return_if_error(rc);
/* Parse the DER encoded integer */
assert(data_ptr);
p = (char *)data_ptr;
if (*p != ASN1_INTEGER) {
/* Invalid ASN.1 integer */
return 1;
}
p++;
/* NV-counters are unsigned integers up to 32-bit */
len = (unsigned int)(*p & 0x7f);
if ((*p & 0x80) || (len > 4)) {
return 1;
}
p++;
/* Check the number is not negative */
if (*p & 0x80) {
return 1;
}
/* Convert to unsigned int. This code is for a little-endian CPU */
cert_nv_ctr = 0;
for (i = 0; i < len; i++) {
cert_nv_ctr = (cert_nv_ctr << 8) | *p++;
}
/* Get the counter from the platform */
rc = plat_get_nv_ctr(param->plat_nv_ctr->cookie, &plat_nv_ctr);
return_if_error(rc);
if (cert_nv_ctr < plat_nv_ctr) {
/* Invalid NV-counter */
return 1;
} else if (cert_nv_ctr > plat_nv_ctr) {
rc = plat_set_nv_ctr2(param->plat_nv_ctr->cookie,
img_desc, cert_nv_ctr);
return_if_error(rc);
}
return 0;
}
int plat_set_nv_ctr2(void *cookie, const auth_img_desc_t *img_desc __unused,
unsigned int nv_ctr)
{
return plat_set_nv_ctr(cookie, nv_ctr);
}
/*
* Return the parent id in the output parameter '*parent_id'
*
* Return value:
* 0 = Image has parent, 1 = Image has no parent or parent is authenticated
*/
int auth_mod_get_parent_id(unsigned int img_id, unsigned int *parent_id)
{
const auth_img_desc_t *img_desc = NULL;
assert(parent_id != NULL);
/* Get the image descriptor */
img_desc = &cot_desc_ptr[img_id];
/* Check if the image has no parent (ROT) */
if (img_desc->parent == NULL) {
*parent_id = 0;
return 1;
}
/* Check if the parent has already been authenticated */
if (auth_img_flags[img_desc->parent->img_id] & IMG_FLAG_AUTHENTICATED) {
*parent_id = 0;
return 1;
}
*parent_id = img_desc->parent->img_id;
return 0;
}
/*
* Initialize the different modules in the authentication framework
*/
void auth_mod_init(void)
{
/* Check we have a valid CoT registered */
assert(cot_desc_ptr != NULL);
/* Crypto module */
crypto_mod_init();
/* Image parser module */
img_parser_init();
}
/*
* Authenticate a certificate/image
*
* Return: 0 = success, Otherwise = error
*/
int auth_mod_verify_img(unsigned int img_id,
void *img_ptr,
unsigned int img_len)
{
const auth_img_desc_t *img_desc = NULL;
const auth_method_desc_t *auth_method = NULL;
void *param_ptr;
unsigned int param_len;
int rc, i;
/* Get the image descriptor from the chain of trust */
img_desc = &cot_desc_ptr[img_id];
/* Ask the parser to check the image integrity */
rc = img_parser_check_integrity(img_desc->img_type, img_ptr, img_len);
return_if_error(rc);
/* Authenticate the image using the methods indicated in the image
* descriptor. */
for (i = 0 ; i < AUTH_METHOD_NUM ; i++) {
auth_method = &img_desc->img_auth_methods[i];
switch (auth_method->type) {
case AUTH_METHOD_NONE:
rc = 0;
break;
case AUTH_METHOD_HASH:
rc = auth_hash(&auth_method->param.hash,
img_desc, img_ptr, img_len);
break;
case AUTH_METHOD_SIG:
rc = auth_signature(&auth_method->param.sig,
img_desc, img_ptr, img_len);
break;
case AUTH_METHOD_NV_CTR:
rc = auth_nvctr(&auth_method->param.nv_ctr,
img_desc, img_ptr, img_len);
break;
default:
/* Unknown authentication method */
rc = 1;
break;
}
return_if_error(rc);
}
/* Extract the parameters indicated in the image descriptor to
* authenticate the children images. */
for (i = 0 ; i < COT_MAX_VERIFIED_PARAMS ; i++) {
if (img_desc->authenticated_data[i].type_desc == NULL) {
continue;
}
/* Get the parameter from the image parser module */
rc = img_parser_get_auth_param(img_desc->img_type,
img_desc->authenticated_data[i].type_desc,
img_ptr, img_len, ¶m_ptr, ¶m_len);
return_if_error(rc);
/* Check parameter size */
if (param_len > img_desc->authenticated_data[i].data.len) {
return 1;
}
/* Copy the parameter for later use */
memcpy((void *)img_desc->authenticated_data[i].data.ptr,
(void *)param_ptr, param_len);
}
/* Mark image as authenticated */
auth_img_flags[img_desc->img_id] |= IMG_FLAG_AUTHENTICATED;
return 0;
}