L-Band: Detect certificate corruption and remove as needed

Related to issue #459

Author: nseidle

Firmware/RTK_Surveyor/States.ino

@@ -278,8 +278,8 @@ void updateSystemState()
             }
 
             // Check for <1m horz accuracy before starting surveyIn
-            systemPrintf("Waiting for Horz Accuracy < %0.2f meters: %0.2f, SIV: %d\r\n", settings.surveyInStartingAccuracy,
-                         horizontalAccuracy, numSV);
+            systemPrintf("Waiting for Horz Accuracy < %0.2f meters: %0.2f, SIV: %d\r\n",
+                         settings.surveyInStartingAccuracy, horizontalAccuracy, numSV);
 
             if (horizontalAccuracy > 0.0 && horizontalAccuracy < settings.surveyInStartingAccuracy)
             {
@@ -483,7 +483,7 @@ void updateSystemState()
                         {
                             marksFileExists = SD_MMC.exists(fileName);
                         }
-#endif  // COMPILE_SD_MMC
+#endif // COMPILE_SD_MMC
 
                         // Open the marks file
                         FileSdFatMMC marksFile;
@@ -678,8 +678,8 @@ void updateSystemState()
                     websocket->textAll(settingsCSV);
                 }
             }
-#endif  // COMPILE_AP
-#endif  // COMPILE_WIFI
+#endif // COMPILE_AP
+#endif // COMPILE_WIFI
         }
         break;
 
@@ -818,8 +818,23 @@ void updateSystemState()
         break;
 
         case (STATE_KEYS_WIFI_CONNECTED): {
-            if (pointperfectUpdateKeys() == true) // Connect to ThingStream MQTT and get PointPerfect key UBX packet
-                displayKeysUpdated();
+
+            // Check that the certs are valid
+            if (checkCertificates() == true)
+            {
+                // Update the keys
+                if (pointperfectUpdateKeys() == true) // Connect to ThingStream MQTT and get PointPerfect key UBX packet
+                    displayKeysUpdated();
+            }
+            else
+            {
+                // Erase keys
+                erasePointperfectCredentials();
+
+                // Provision device
+                if(pointperfectProvisionDevice() == true) // Connect to ThingStream API and get keys
+                    displayKeysUpdated();
+            }
 
             // WiFi will be turned off once we exit this state, if no other service needs it
 
@@ -941,9 +956,9 @@ void updateSystemState()
             espnowBeginPairing();
 
             changeState(STATE_ESPNOW_PAIRING);
-#else   // COMPILE_ESPNOW
+#else  // COMPILE_ESPNOW
             changeState(STATE_ROVER_NOT_STARTED);
-#endif  // COMPILE_ESPNOW
+#endif // COMPILE_ESPNOW
         }
         break;
 
@@ -1029,7 +1044,7 @@ void updateSystemState()
             // The code should only be able to enter this state if configureViaEthernet is true.
             // If configureViaEthernet is not true, we need to restart again.
             //(If we continue, startEthernerWebServerESP32W5500 will fail as it won't have exclusive access to SPI and
-            //ints).
+            // ints).
             if (!configureViaEthernet)
             {
                 displayConfigViaEthNotStarted(1500);
@@ -1098,8 +1113,8 @@ void updateSystemState()
                     websocket->textAll(settingsCSV);
                 }
             }
-#endif  // COMPILE_AP
-#endif  // COMPILE_WIFI
+#endif // COMPILE_AP
+#endif // COMPILE_WIFI
         }
         break;
 
@@ -1115,7 +1130,7 @@ void updateSystemState()
             ESP.restart();
         }
         break;
-#endif  // COMPILE_ETHERNET
+#endif // COMPILE_ETHERNET
 
         case (STATE_SHUTDOWN): {
             forceDisplayUpdate = true;

Firmware/RTK_Surveyor/menuPP.ino

@@ -1,5 +1,7 @@
 #ifdef COMPILE_L_BAND
 
+#include "mbedtls/ssl.h" //Needed for certificate validation
+
 //----------------------------------------
 // Locals - compiled out
 //----------------------------------------
@@ -12,7 +14,7 @@ static SFE_UBLOX_GNSS_SUPER i2cLBand; // NEO-D9S
 #ifndef POINTPERFECT_TOKEN
 #define POINTPERFECT_TOKEN                                                                                             \
     0xAA, 0xBB, 0xCC, 0xDD, 0x00, 0x11, 0x22, 0x33, 0x0A, 0x0B, 0x0C, 0x0D, 0x00, 0x01, 0x02, 0x03
-#endif  // POINTPERFECT_TOKEN
+#endif // POINTPERFECT_TOKEN
 
 static uint8_t pointPerfectTokenArray[16] = {POINTPERFECT_TOKEN}; // Token in HEX form
 
@@ -196,7 +198,7 @@ bool pointperfectProvisionDevice()
         // Override ID with testing ID
         snprintf(hardwareID, sizeof(hardwareID), "%02X%02X%02X%02X%02X%02X", whitelistID[0], whitelistID[1],
                  whitelistID[2], whitelistID[3], whitelistID[4], whitelistID[5]);
-#endif  // WHITELISTED_ID
+#endif // WHITELISTED_ID
 
         char givenName[100];
         snprintf(givenName, sizeof(givenName), "SparkFun RTK %s v%d.%d - %s", platformPrefix, FIRMWARE_VERSION_MAJOR,
@@ -317,9 +319,94 @@ bool pointperfectProvisionDevice()
     bluetoothStart();
 
     return (retVal);
-#else   // COMPILE_WIFI
+#else  // COMPILE_WIFI
     return (false);
-#endif  // COMPILE_WIFI
+#endif // COMPILE_WIFI
+}
+
+// Check certificate and privatekey for valid formatting
+// Return false if improperly formatted
+bool checkCertificates()
+{
+    bool validCertificates = true;
+    char *certificateContents = nullptr; // Holds the contents of the keys prior to MQTT connection
+    char *keyContents = nullptr;
+
+    // Allocate the buffers
+    certificateContents = (char *)malloc(MQTT_CERT_SIZE);
+    keyContents = (char *)malloc(MQTT_CERT_SIZE);
+    if ((!certificateContents) || (!keyContents))
+    {
+        systemPrintln("Failed to allocate content buffers!");
+        return (false);
+    }
+
+    // Load the certificate
+    memset(certificateContents, 0, MQTT_CERT_SIZE);
+    loadFile("certificate", certificateContents);
+
+    if (checkCertificateValidity(certificateContents, strlen(certificateContents)) == false)
+    {
+        log_d("Certificate is corrupt.");
+        validCertificates = false;
+    }
+
+    // Load the private key
+    memset(keyContents, 0, MQTT_CERT_SIZE);
+    loadFile("privateKey", keyContents);
+
+    if (checkCertificateValidity(keyContents, strlen(keyContents)) == false)
+    {
+        log_d("PrivateKey is corrupt.");
+        validCertificates = false;
+    }
+
+    // Free the content buffers
+    if (certificateContents)
+        free(certificateContents);
+    if (keyContents)
+        free(keyContents);
+
+    return (validCertificates);
+}
+
+// Check if a given certificate is in a valid format
+// This was created to detect corrupt or invalid certificates caused by bugs in v3.0 to and including v3.3.
+bool checkCertificateValidity(char *certificateContent, int certificateContentSize)
+{
+    // Check for valid format of certificate
+    // From ssl_client.cpp
+    // https://stackoverflow.com/questions/70670070/mbedtls-cannot-parse-valid-x509-certificate
+    mbedtls_x509_crt certificate;
+    mbedtls_x509_crt_init(&certificate);
+
+    int result_code =
+        mbedtls_x509_crt_parse(&certificate, (unsigned char *)certificateContent, certificateContentSize + 1);
+
+    mbedtls_x509_crt_free(&certificate);
+
+    if (result_code < 0)
+    {
+        log_d("Cert formatting invalid");
+        return (false);
+    }
+
+    return (true);
+}
+
+// When called, removes the files used for SSL to PointPerfect obtained during provisioning
+// Also deletes keys so the user can immediately re-provision
+void erasePointperfectCredentials()
+{
+    char fileName[80];
+
+    snprintf(fileName, sizeof(fileName), "/%s_%s_%d.txt", platformFilePrefix, "certificate", profileNumber);
+    LittleFS.remove(fileName);
+
+    snprintf(fileName, sizeof(fileName), "/%s_%s_%d.txt", platformFilePrefix, "privateKey", profileNumber);
+    LittleFS.remove(fileName);
+    strcpy(settings.pointPerfectCurrentKey, ""); // Clear contents
+    strcpy(settings.pointPerfectNextKey, "");    // Clear contents
 }
 
 // Subscribe to MQTT channel, grab keys, then stop
@@ -445,9 +532,9 @@ bool pointperfectUpdateKeys()
 
     // Return the key status
     return (gotKeys);
-#else   // COMPILE_WIFI
+#else  // COMPILE_WIFI
     return (false);
-#endif  // COMPILE_WIFI
+#endif // COMPILE_WIFI
 }
 
 char *ltrim(char *s)
@@ -565,6 +652,13 @@ int daysFromEpoch(long long endEpoch)
 {
     endEpoch /= 1000; // Convert PointPerfect ms Epoch to s
 
+    if (online.rtc == false)
+    {
+        // If we don't have RTC we can't calculate days to expire
+        log_d("No RTC available");
+        return (0);
+    }
+
     long localEpoch = rtc.getEpoch();
 
     long delta = endEpoch - localEpoch; // number of s between dates
@@ -954,13 +1048,22 @@ void menuPointPerfect()
         systemPrint("Days until keys expire: ");
         if (strlen(settings.pointPerfectCurrentKey) > 0)
         {
-            int daysRemaining =
-                daysFromEpoch(settings.pointPerfectNextKeyStart + settings.pointPerfectNextKeyDuration + 1);
-
-            if (daysRemaining < 0)
-                systemPrintln("Expired");
+            if (online.rtc == false)
+            {
+                // If we don't have RTC we can't calculate days to expire
+                systemPrintln("No RTC");
+            }
             else
-                systemPrintln(daysRemaining);
+            {
+
+                int daysRemaining =
+                    daysFromEpoch(settings.pointPerfectNextKeyStart + settings.pointPerfectNextKeyDuration + 1);
+
+                if (daysRemaining < 0)
+                    systemPrintln("Expired");
+                else
+                    systemPrintln(daysRemaining);
+            }
         }
         else
             systemPrintln("No keys");
@@ -1021,8 +1124,23 @@ void menuPointPerfect()
                     {
                         pointperfectProvisionDevice(); // Connect to ThingStream API and get keys
                     }
-                    else
-                        pointperfectUpdateKeys();
+                    else // We have certs and keys
+                    {
+                        // Check that the certs are valid
+                        if (checkCertificates() == true)
+                        {
+                            // Update the keys
+                            pointperfectUpdateKeys();
+                        }
+                        else
+                        {
+                            // Erase keys
+                            erasePointperfectCredentials();
+
+                            // Provision device
+                            pointperfectProvisionDevice(); // Connect to ThingStream API and get keys
+                        }
+                    }
                 }
                 else
                 {