Added Helper Function to Check Validity of Base64 Encoded String

emargolis · Jul 7, 2023 · b9bb3f8 · b9bb3f8
1 parent e3304c0
commit b9bb3f8
Showing 1 changed file with 36 additions and 0 deletions.
diff --git a/src/lib/support/jsontlv/JsonToTlv.cpp b/src/lib/support/jsontlv/JsonToTlv.cpp
@@ -130,6 +130,40 @@ bool isSignedInteger(const std::string & s)
  return isUnsignedInteger(s);
 }
 
+bool isValidBase64String(const std::string & s)
+{
+ const std::string base64Chars =
+ "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+ size_t len = s.length();
+
+ // Check if the length is a multiple of 4
+ if (len == 0 || len % 4 != 0)
+ {
+ return false;
+ }
+
+ size_t paddingLen = 0;
+ if (s[len - 1] == '=')
+ {
+ paddingLen++;
+ if (s[len - 2] == '=')
+ {
+ paddingLen++;
+ }
+ }
+
+ // Check for invalid characters
+ for (char c : s.substr(0, len - paddingLen - 1))
+ {
+ if (base64Chars.find(c) == std::string::npos)
+ {
+ return false;
+ }
+ }
+
+ return true;
+}
+
 CHIP_ERROR ParseJsonKey(const std::string & key, TLV::Tag & tag, ElementTypeContext & type, ElementTypeContext & subType)
 {
  uint64_t tagNumber = 0;
@@ -257,6 +291,8 @@ CHIP_ERROR EncodeTlvElement(const json & val, TLV::TLVWriter & writer, TLV::Tag
  size_t encodedLen = val.get<std::string>().length();
  VerifyOrReturnError(CanCastTo<uint16_t>(encodedLen), CHIP_ERROR_INVALID_ARGUMENT);
 
+ VerifyOrReturnError(isValidBase64String(val.get<std::string>()), CHIP_ERROR_INVALID_ARGUMENT);
+
  Platform::ScopedMemoryBuffer<uint8_t> byteString;
  byteString.Alloc(BASE64_MAX_DECODED_LEN(static_cast<uint16_t>(encodedLen)));
  VerifyOrReturnError(byteString.Get() != nullptr, CHIP_ERROR_NO_MEMORY);