Merge branch 'bugfix/backport_certificate_bundle_fixes_v4.3' into 'release/v4.3'

Certificate bundle fixes (v4.3)

See merge request espressif/esp-idf!18353

components/mbedtls/CMakeLists.txt

@@ -15,9 +15,9 @@ if(CONFIG_MBEDTLS_CERTIFICATE_BUNDLE)
     set(GENERATE_CERT_BUNDLEPY ${python} ${COMPONENT_DIR}/esp_crt_bundle/gen_crt_bundle.py)
 
     if(CONFIG_MBEDTLS_CERTIFICATE_BUNDLE_DEFAULT_FULL)
-        list(APPEND crt_paths ${DEFAULT_CRT_DIR}/cacrt_all.pem)
+        list(APPEND crt_paths ${DEFAULT_CRT_DIR}/cacrt_all.pem ${DEFAULT_CRT_DIR}/cacrt_local.pem)
     elseif(CONFIG_MBEDTLS_CERTIFICATE_BUNDLE_DEFAULT_CMN)
-        list(APPEND crt_paths ${DEFAULT_CRT_DIR}/cacrt_all.pem)
+        list(APPEND crt_paths ${DEFAULT_CRT_DIR}/cacrt_all.pem ${DEFAULT_CRT_DIR}/cacrt_local.pem)
         list(APPEND args --filter ${DEFAULT_CRT_DIR}/cmn_crt_authorities.csv)
     endif()
 

components/mbedtls/Kconfig

@@ -323,6 +323,12 @@ menu "mbedTLS"
             help
                 Name of the custom certificate directory or file. This path is evaluated
                 relative to the project root directory.
+
+        config MBEDTLS_CERTIFICATE_BUNDLE_MAX_CERTS
+            int "Maximum no of certificates allowed in certificate bundle"
+            default 200
+            depends on MBEDTLS_CERTIFICATE_BUNDLE
+
     endmenu
 
     config MBEDTLS_ECP_RESTARTABLE

components/mbedtls/esp_crt_bundle/cacrt_local.pem

@@ -0,0 +1,33 @@
+##
+## Local CA Root Certificates
+##
+## Local CA Root Certificates that gets appended to "cacrt_all.pem"
+
+
+## letsencrypt has generated a cross signed certificate with DST ROOT CA X3
+## for compatibility after the expiry of the certificate.
+## The new certificate has the ISSUER name as DST Root CA X3.
+## Thus, the handshake fails if esp_crt_bundle does not find the
+## respective name in the crt_bundle.
+## Keeping this certificate for compatibility reasons.
+## This will be removed once the cross-signed certificate expires in Sep 2024.
+
+DST Root CA X3
+==============
+-----BEGIN CERTIFICATE-----
+MIIDSjCCAjKgAwIBAgIQRK+wgNajJ7qJMDmGLvhAazANBgkqhkiG9w0BAQUFADA/MSQwIgYDVQQK
+ExtEaWdpdGFsIFNpZ25hdHVyZSBUcnVzdCBDby4xFzAVBgNVBAMTDkRTVCBSb290IENBIFgzMB4X
+DTAwMDkzMDIxMTIxOVoXDTIxMDkzMDE0MDExNVowPzEkMCIGA1UEChMbRGlnaXRhbCBTaWduYXR1
+cmUgVHJ1c3QgQ28uMRcwFQYDVQQDEw5EU1QgUm9vdCBDQSBYMzCCASIwDQYJKoZIhvcNAQEBBQAD
+ggEPADCCAQoCggEBAN+v6ZdQCINXtMxiZfaQguzH0yxrMMpb7NnDfcdAwRgUi+DoM3ZJKuM/IUmT
+rE4Orz5Iy2Xu/NMhD2XSKtkyj4zl93ewEnu1lcCJo6m67XMuegwGMoOifooUMM0RoOEqOLl5CjH9
+UL2AZd+3UWODyOKIYepLYYHsUmu5ouJLGiifSKOeDNoJjj4XLh7dIN9bxiqKqy69cK3FCxolkHRy
+xXtqqzTWMIn/5WgTe1QLyNau7Fqckh49ZLOMxt+/yUFw7BZy1SbsOFU5Q9D8/RhcQPGX69Wam40d
+utolucbY38EVAjqr2m7xPi71XAicPNaDaeQQmxkqtilX4+U9m5/wAl0CAwEAAaNCMEAwDwYDVR0T
+AQH/BAUwAwEB/zAOBgNVHQ8BAf8EBAMCAQYwHQYDVR0OBBYEFMSnsaR7LHH62+FLkHX/xBVghYkQ
+MA0GCSqGSIb3DQEBBQUAA4IBAQCjGiybFwBcqR7uKGY3Or+Dxz9LwwmglSBd49lZRNI+DT69ikug
+dB/OEIKcdBodfpga3csTS7MgROSR6cz8faXbauX+5v3gTt23ADq1cEmv8uXrAvHRAosZy5Q6XkjE
+GB5YGV8eAlrwDPGxrancWYaLbumR9YbK+rlmM6pZW87ipxZzR8srzJmwN0jP41ZL9c8PDHIyh8bw
+RLtTcm1D9SZImlJnt1ir/md2cXjbDaJWFBM5JDGFoqgCWjBH4d1QB7wCCZAA62RjYJsWvIjJEubS
+fZGL+T0yjWW06XyxV3bqxbYoOb8VZRzI9neWagqNdwvYkQsEjgfbKbYK7p2CNTUQ
+-----END CERTIFICATE-----

components/mbedtls/esp_crt_bundle/esp_crt_bundle.c

@@ -17,7 +17,6 @@
 #include <esp_system.h>
 #include "esp_crt_bundle.h"
 #include "esp_log.h"
-#include "esp_err.h"
 
 #define BUNDLE_HEADER_OFFSET 2
 #define CRT_HEADER_OFFSET 4
@@ -157,27 +156,56 @@ int esp_crt_verify_callback(void *buf, mbedtls_x509_crt *crt, int depth, uint32_
 /* 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)
+static esp_err_t esp_crt_bundle_init(const uint8_t *x509_bundle, size_t bundle_size)
 {
-    s_crt_bundle.num_certs = (x509_bundle[0] << 8) | x509_bundle[1];
+    if (bundle_size < BUNDLE_HEADER_OFFSET + CRT_HEADER_OFFSET) {
-    s_crt_bundle.crts = calloc(s_crt_bundle.num_certs, sizeof(x509_bundle));
+        ESP_LOGE(TAG, "Invalid certificate bundle");
+        return ESP_ERR_INVALID_ARG;
+    }
 
-    if (s_crt_bundle.crts == NULL) {
+    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 < s_crt_bundle.num_certs; i++) {
+    for (int i = 0; i < num_certs; i++) {
-        s_crt_bundle.crts[i] = cur_crt;
+        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;
 }
 
@@ -186,7 +214,7 @@ 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);
+        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) {
@@ -217,9 +245,7 @@ void esp_crt_bundle_detach(mbedtls_ssl_config *conf)
     }
 }
 
-void esp_crt_bundle_set(const uint8_t *x509_bundle)
+esp_err_t esp_crt_bundle_set(const uint8_t *x509_bundle, size_t bundle_size)
 {
-    // Free any previously used bundle
+    return esp_crt_bundle_init(x509_bundle, bundle_size);
-    free(s_crt_bundle.crts);
-    esp_crt_bundle_init(x509_bundle);
 }

components/mbedtls/esp_crt_bundle/include/esp_crt_bundle.h

@@ -1,21 +1,14 @@
-// Copyright 2017-2019 Espressif Systems (Shanghai) PTE LTD
+/*
-//
+ * SPDX-FileCopyrightText: 2017-2022 Espressif Systems (Shanghai) CO LTD
-// Licensed under the Apache License, Version 2.0 (the "License");
+ *
-// you may not use this file except in compliance with the License.
+ * SPDX-License-Identifier: Apache-2.0
-// 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.
 
 
 #ifndef _ESP_CRT_BUNDLE_H_
 #define _ESP_CRT_BUNDLE_H_
 
+#include "esp_err.h"
 #include "mbedtls/ssl.h"
 
 #ifdef __cplusplus
@@ -52,13 +45,19 @@ void esp_crt_bundle_detach(mbedtls_ssl_config *conf);
 /**
  * @brief      Set the default certificate bundle used for verification
  *
- * Overrides the default certificate bundle. In most use cases the bundle should be
+ * Overrides the default certificate bundle only in case of successful initialization. In most use cases the bundle should be
  * set through menuconfig. The bundle needs to be sorted by subject name since binary search is
  * used to find certificates.
  *
  * @param[in]  x509_bundle     A pointer to the certificate bundle.
+ *
+ * @param[in]  bundle_size     Size of the certificate bundle in bytes.
+ *
+ * @return
+ *             - ESP_OK  if adding certificates was successful.
+ *             - Other   if an error occured or an action must be taken by the calling process.
  */
-void esp_crt_bundle_set(const uint8_t *x509_bundle);
+esp_err_t esp_crt_bundle_set(const uint8_t *x509_bundle, size_t bundle_size);
 
 
 #ifdef __cplusplus

components/mbedtls/test/test_esp_crt_bundle.c

@@ -35,6 +35,7 @@
 #include "mbedtls/debug.h"
 
 #include "esp_crt_bundle.h"
+// #include "esp_random.h"
 
 #include "unity.h"
 #include "test_utils.h"
@@ -253,7 +254,7 @@ esp_err_t client_setup(mbedtls_endpoint_t *client)
     return ESP_OK;
 }
 
-int client_task(const uint8_t *bundle, esp_crt_validate_res_t *res)
+int client_task(const uint8_t *bundle, size_t bundle_size, esp_crt_validate_res_t *res)
 {
     int ret = ESP_FAIL;
 
@@ -269,7 +270,7 @@ int client_task(const uint8_t *bundle, esp_crt_validate_res_t *res)
     esp_crt_bundle_attach(&client.conf);
     if (bundle) {
         /* Set a bundle different from the menuconfig bundle */
-        esp_crt_bundle_set(bundle);
+        esp_crt_bundle_set(bundle, bundle_size);
     }
 
     ESP_LOGI(TAG, "Connecting to %s:%s...", SERVER_ADDRESS, SERVER_PORT);
@@ -329,11 +330,11 @@ TEST_CASE("custom certificate bundle", "[mbedtls]")
    }
 
    /* Test with default crt bundle that doesnt contain the ca crt */
-   client_task(NULL, &validate_res);
+   client_task(NULL, 0, &validate_res);
    TEST_ASSERT(validate_res == ESP_CRT_VALIDATE_FAIL);
 
    /* Test with bundle that does contain the CA crt */
-   client_task(server_cert_bundle_start, &validate_res);
+   client_task(server_cert_bundle_start, server_cert_bundle_end - server_cert_bundle_start, &validate_res);
    TEST_ASSERT(validate_res == ESP_CRT_VALIDATE_OK);
 
    exit_flag = true;
@@ -390,3 +391,50 @@ TEST_CASE("custom certificate bundle - wrong signature", "[mbedtls]")
 
     esp_crt_bundle_detach(NULL);
 }
+
+TEST_CASE("custom certificate bundle init API - bound checking", "[mbedtls]")
+{
+
+    uint8_t test_bundle[256] = {0};
+    esp_err_t esp_ret;
+    /* The API should fail with bundle size given as 1 */
+    esp_ret = esp_crt_bundle_set(test_bundle, 1);
+    TEST_ASSERT( esp_ret == ESP_ERR_INVALID_ARG);
+
+    /* Check that the esp_crt_bundle_set API will not accept a bundle
+     * which has more no. of certs than configured in
+     * CONFIG_MBEDTLS_CERTIFICATE_BUNDLE_MAX_CERTS */
+
+    uint8_t rand;
+    esp_fill_random(&rand, 1);
+    test_bundle[0] = rand;
+
+    /* Make sure that the number of certs will always be greater than
+     * CONFIG_MBEDTLS_CERTIFICATE_BUNDLE_MAX_CERTS */
+    test_bundle[1] = rand + CONFIG_MBEDTLS_CERTIFICATE_BUNDLE_MAX_CERTS;
+
+    esp_ret = esp_crt_bundle_set(test_bundle, sizeof(test_bundle));
+    TEST_ASSERT( esp_ret == ESP_ERR_INVALID_ARG);
+
+    /* The API should fail with bundle_size < BUNDLE_HEADER_OFFSET (2) + CRT_HEADER_OFFSET (4) */
+    test_bundle[0] = 0;
+    test_bundle[1] = 1; /* set num_certs = 1 */
+    esp_ret = esp_crt_bundle_set(test_bundle, 5);
+    TEST_ASSERT(esp_ret == ESP_ERR_INVALID_ARG);
+
+    /* Cert number is greater than actual certs present, The API should fail */
+    /* Actual No. of certs present in bundle = 1, setting num_certs to 5 */
+    test_bundle[1] = 5; /* num_certs */
+    test_bundle[3] = 5; /* cert_1_name_len */
+    test_bundle[5] = 10; /* cert_1_pub_key_len */
+    /* Actual bundle size becomes BUNDLE_HEADER_OFFSET (2) + CRT_HEADER_OFFSET (4) + cert_1_name_len(5) + cert_1_pub_key_len(10)
+     * i.e. 21 bytes */
+    esp_ret = esp_crt_bundle_set(test_bundle, 21);
+    TEST_ASSERT(esp_ret == ESP_ERR_INVALID_ARG);
+
+    /* The API should fail if bundle_size < BUNDLE_HEADER_OFFSET (2) + CRT_HEADER_OFFSET (4) + cert_1_name_len(5) + cert_1_pub_key_len(10) */
+    esp_ret = esp_crt_bundle_set(test_bundle, 20);
+    TEST_ASSERT(esp_ret == ESP_ERR_INVALID_ARG);
+
+    esp_crt_bundle_detach(NULL);
+}

docs/en/api-reference/protocols/esp_crt_bundle.rst

@@ -12,7 +12,7 @@ The bundle comes with the complete list of root certificates from Mozilla’s NS
 
 When generating the bundle you may choose between:
 
- * The full root certificate bundle from Mozilla, containing more than 130 certificates. The current bundle was updated Wed Jan 23 04:12:09 2019 GMT.
+ * The full root certificate bundle from Mozilla, containing more than 130 certificates. The current bundle was updated Tue Apr 26 03:12:05 2022 GMT.
  * A pre-selected filter list of the name of the most commonly used root certificates, reducing the amount of certificates to around 35 while still having around 90 % coverage according to market share statistics.
 
 In addition it is possible to specify a path to a certificate file or a directory containing certificates which then will be added to the generated bundle.