Add function to get authorityKeyId from certificate

Author: pennam

src/ECP256Certificate.cpp

@@ -12,6 +12,8 @@
  * INCLUDE
  ******************************************************************************/
 
+#define _GNU_SOURCE
+#include <string.h>
 #include "ECP256Certificate.h"
 
 /******************************************************************************
@@ -384,6 +386,17 @@ int ECP256Certificate::setSignature(const byte* signature, int signatureLen) {
   return 0;
 }
 
+const byte * ECP256Certificate::authorityKeyId() const {
+  static const byte objectId[] = {0x06, 0x03, 0x55, 0x1D, 0x23};
+  byte * result = nullptr;
+  void * ptr = memmem(_certBuffer, _certBufferLen, objectId, sizeof(objectId));
+  if (ptr != nullptr) {
+    result = (byte*)ptr;
+    result += 11;
+  }
+  return result;
+}
+
 /******************************************************************************
  * PRIVATE MEMBER FUNCTIONS
  ******************************************************************************/

src/ECP256Certificate.h

@@ -68,6 +68,9 @@ class ECP256Certificate {
   inline byte* bytes() { return _certBuffer; }
   inline int length() { return _certBufferLen; }
 
+  /* Parsing Helpers */
+  const byte * authorityKeyId() const;
+
 #if defined(SECURE_ELEMENT_IS_ECCX08)
   /* Get Data to create ECCX08 compressed cert */
   inline byte* compressedCertBytes() { return _compressedCert.data; }