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copy esp_crt_bundle.c from esp-idf@d51f7d8821

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Jeff Epler 2022-10-05 13:46:35 -05:00
parent a64c1a11c5
commit 944d388158
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GPG Key ID: D5BF15AB975AB4DE
1 changed files with 251 additions and 0 deletions
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ports/raspberrypi/mbedtls/esp_crt_bundle.c Normal file
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// Copyright 2018-2019 Espressif Systems (Shanghai) PTE LTD
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include <string.h>
#include <esp_system.h>
#include "esp_crt_bundle.h"
#include "esp_log.h"
#define BUNDLE_HEADER_OFFSET 2
#define CRT_HEADER_OFFSET 4
static const char *TAG = "esp-x509-crt-bundle";
/* a dummy certificate so that
* cacert_ptr passes non-NULL check during handshake */
static mbedtls_x509_crt s_dummy_crt;
extern const uint8_t x509_crt_imported_bundle_bin_start[] asm("_binary_x509_crt_bundle_start");
extern const uint8_t x509_crt_imported_bundle_bin_end[] asm("_binary_x509_crt_bundle_end");
typedef struct crt_bundle_t {
const uint8_t **crts;
uint16_t num_certs;
size_t x509_crt_bundle_len;
} crt_bundle_t;
static crt_bundle_t s_crt_bundle;
static int esp_crt_check_signature(mbedtls_x509_crt *child, const uint8_t *pub_key_buf, size_t pub_key_len);
static int esp_crt_check_signature(mbedtls_x509_crt *child, const uint8_t *pub_key_buf, size_t pub_key_len)
{
int ret = 0;
mbedtls_x509_crt parent;
const mbedtls_md_info_t *md_info;
unsigned char hash[MBEDTLS_MD_MAX_SIZE];
mbedtls_x509_crt_init(&parent);
if ( (ret = mbedtls_pk_parse_public_key(&parent.pk, pub_key_buf, pub_key_len) ) != 0) {
ESP_LOGE(TAG, "PK parse failed with error %X", ret);
goto cleanup;
}
// Fast check to avoid expensive computations when not necessary
if (!mbedtls_pk_can_do(&parent.pk, child->sig_pk)) {
ESP_LOGE(TAG, "Simple compare failed");
ret = -1;
goto cleanup;
}
md_info = mbedtls_md_info_from_type(child->sig_md);
if ( (ret = mbedtls_md( md_info, child->tbs.p, child->tbs.len, hash )) != 0 ) {
ESP_LOGE(TAG, "Internal mbedTLS error %X", ret);
goto cleanup;
}
if ( (ret = mbedtls_pk_verify_ext( child->sig_pk, child->sig_opts, &parent.pk,
child->sig_md, hash, mbedtls_md_get_size( md_info ),
child->sig.p, child->sig.len )) != 0 ) {
ESP_LOGE(TAG, "PK verify failed with error %X", ret);
goto cleanup;
}
cleanup:
mbedtls_x509_crt_free(&parent);
return ret;
}
/* This callback is called for every certificate in the chain. If the chain
* is proper each intermediate certificate is validated through its parent
* in the x509_crt_verify_chain() function. So this callback should
* only verify the first untrusted link in the chain is signed by the
* root certificate in the trusted bundle
*/
int esp_crt_verify_callback(void *buf, mbedtls_x509_crt *crt, int depth, uint32_t *flags)
{
mbedtls_x509_crt *child = crt;
/* It's OK for a trusted cert to have a weak signature hash alg.
as we already trust this certificate */
uint32_t flags_filtered = *flags & ~(MBEDTLS_X509_BADCERT_BAD_MD);
if (flags_filtered != MBEDTLS_X509_BADCERT_NOT_TRUSTED) {
return 0;
}
if (s_crt_bundle.crts == NULL) {
ESP_LOGE(TAG, "No certificates in bundle");
return MBEDTLS_ERR_X509_FATAL_ERROR;
}
ESP_LOGD(TAG, "%d certificates in bundle", s_crt_bundle.num_certs);
size_t name_len = 0;
const uint8_t *crt_name;
bool crt_found = false;
int start = 0;
int end = s_crt_bundle.num_certs - 1;
int middle = (end - start) / 2;
/* Look for the certificate using binary search on subject name */
while (start <= end) {
name_len = s_crt_bundle.crts[middle][0] << 8 | s_crt_bundle.crts[middle][1];
crt_name = s_crt_bundle.crts[middle] + CRT_HEADER_OFFSET;
int cmp_res = memcmp(child->issuer_raw.p, crt_name, name_len );
if (cmp_res == 0) {
crt_found = true;
break;
} else if (cmp_res < 0) {
end = middle - 1;
} else {
start = middle + 1;
}
middle = (start + end) / 2;
}
int ret = MBEDTLS_ERR_X509_FATAL_ERROR;
if (crt_found) {
size_t key_len = s_crt_bundle.crts[middle][2] << 8 | s_crt_bundle.crts[middle][3];
ret = esp_crt_check_signature(child, s_crt_bundle.crts[middle] + CRT_HEADER_OFFSET + name_len, key_len);
}
if (ret == 0) {
ESP_LOGI(TAG, "Certificate validated");
*flags = 0;
return 0;
}
ESP_LOGE(TAG, "Failed to verify certificate");
return MBEDTLS_ERR_X509_FATAL_ERROR;
}
/* Initialize the bundle into an array so we can do binary search for certs,
the bundle generated by the python utility is already presorted by subject name
*/
static esp_err_t esp_crt_bundle_init(const uint8_t *x509_bundle, size_t bundle_size)
{
if (bundle_size < BUNDLE_HEADER_OFFSET + CRT_HEADER_OFFSET) {
ESP_LOGE(TAG, "Invalid certificate bundle");
return ESP_ERR_INVALID_ARG;
}
uint16_t num_certs = (x509_bundle[0] << 8) | x509_bundle[1];
if (num_certs > CONFIG_MBEDTLS_CERTIFICATE_BUNDLE_MAX_CERTS) {
ESP_LOGE(TAG, "No. of certs in the certificate bundle = %d exceeds\n"
"Max allowed certificates in the certificate bundle = %d\n"
"Please update the menuconfig option with appropriate value", num_certs, CONFIG_MBEDTLS_CERTIFICATE_BUNDLE_MAX_CERTS);
return ESP_ERR_INVALID_ARG;
}
const uint8_t **crts = calloc(num_certs, sizeof(x509_bundle));
if (crts == NULL) {
ESP_LOGE(TAG, "Unable to allocate memory for bundle");
return ESP_ERR_NO_MEM;
}
const uint8_t *cur_crt;
/* This is the maximum region that is allowed to access */
const uint8_t *bundle_end = x509_bundle + bundle_size;
cur_crt = x509_bundle + BUNDLE_HEADER_OFFSET;
for (int i = 0; i < num_certs; i++) {
crts[i] = cur_crt;
if (cur_crt + CRT_HEADER_OFFSET > bundle_end) {
ESP_LOGE(TAG, "Invalid certificate bundle");
free(crts);
return ESP_ERR_INVALID_ARG;
}
size_t name_len = cur_crt[0] << 8 | cur_crt[1];
size_t key_len = cur_crt[2] << 8 | cur_crt[3];
cur_crt = cur_crt + CRT_HEADER_OFFSET + name_len + key_len;
}
if (cur_crt > bundle_end) {
ESP_LOGE(TAG, "Invalid certificate bundle");
free(crts);
return ESP_ERR_INVALID_ARG;
}
/* The previous crt bundle is only updated when initialization of the
* current crt_bundle is successful */
/* Free previous crt_bundle */
free(s_crt_bundle.crts);
s_crt_bundle.num_certs = num_certs;
s_crt_bundle.crts = crts;
return ESP_OK;
}
esp_err_t esp_crt_bundle_attach(void *conf)
{
esp_err_t ret = ESP_OK;
// If no bundle has been set by the user then use the bundle embedded in the binary
if (s_crt_bundle.crts == NULL) {
ret = esp_crt_bundle_init(x509_crt_imported_bundle_bin_start, x509_crt_imported_bundle_bin_end - x509_crt_imported_bundle_bin_start);
}
if (ret != ESP_OK) {
ESP_LOGE(TAG, "Failed to attach bundle");
return ret;
}
if (conf) {
/* point to a dummy certificate
* This is only required so that the
* cacert_ptr passes non-NULL check during handshake
*/
mbedtls_ssl_config *ssl_conf = (mbedtls_ssl_config *)conf;
mbedtls_x509_crt_init(&s_dummy_crt);
mbedtls_ssl_conf_ca_chain(ssl_conf, &s_dummy_crt, NULL);
mbedtls_ssl_conf_verify(ssl_conf, esp_crt_verify_callback, NULL);
}
return ret;
}
void esp_crt_bundle_detach(mbedtls_ssl_config *conf)
{
free(s_crt_bundle.crts);
s_crt_bundle.crts = NULL;
if (conf) {
mbedtls_ssl_conf_verify(conf, NULL, NULL);
}
}
esp_err_t esp_crt_bundle_set(const uint8_t *x509_bundle, size_t bundle_size)
{
return esp_crt_bundle_init(x509_bundle, bundle_size);
}