ASN.1 null writer check should not bypass reading from TLVReader (#31088

) ... since it is just intended to be an optimization.
project-chip · Apr 11, 2024 · 1049594 · 1049594
1 parent b065298
commit 1049594
Show file tree

Hide file tree

Showing 2 changed files with 15 additions and 4 deletions.
diff --git a/src/lib/asn1/ASN1Writer.cpp b/src/lib/asn1/ASN1Writer.cpp
@@ -234,13 +234,13 @@ CHIP_ERROR ASN1Writer::PutBitString(uint8_t unusedBitCount, const uint8_t * enco
 
 CHIP_ERROR ASN1Writer::PutBitString(uint8_t unusedBitCount, chip::TLV::TLVReader & tlvReader)
 {
- ReturnErrorCodeIf(IsNullWriter(), CHIP_NO_ERROR);
-
  ByteSpan encodedBits;
  ReturnErrorOnFailure(tlvReader.Get(encodedBits));
 
  VerifyOrReturnError(CanCastTo<int32_t>(encodedBits.size() + 1), ASN1_ERROR_LENGTH_OVERFLOW);
 
+ ReturnErrorCodeIf(IsNullWriter(), CHIP_NO_ERROR);
+
  ReturnErrorOnFailure(
  EncodeHead(kASN1TagClass_Universal, kASN1UniversalTag_BitString, false, static_cast<int32_t>(encodedBits.size() + 1)));
 
@@ -335,13 +335,13 @@ CHIP_ERROR ASN1Writer::PutValue(uint8_t cls, uint8_t tag, bool isConstructed, co
 
 CHIP_ERROR ASN1Writer::PutValue(uint8_t cls, uint8_t tag, bool isConstructed, chip::TLV::TLVReader & tlvReader)
 {
- ReturnErrorCodeIf(IsNullWriter(), CHIP_NO_ERROR);
-
  ByteSpan val;
  ReturnErrorOnFailure(tlvReader.Get(val));
 
  VerifyOrReturnError(CanCastTo<int32_t>(val.size()), ASN1_ERROR_LENGTH_OVERFLOW);
 
+ ReturnErrorCodeIf(IsNullWriter(), CHIP_NO_ERROR);
+
  ReturnErrorOnFailure(EncodeHead(cls, tag, isConstructed, static_cast<int32_t>(val.size())));
 
  WriteData(val.data(), val.size());

diff --git a/src/lib/asn1/tests/TestASN1.cpp b/src/lib/asn1/tests/TestASN1.cpp
@@ -304,6 +304,17 @@ static void TestASN1_NullWriter(nlTestSuite * inSuite, void * inContext)
 
  encodedLen = writer.GetLengthWritten();
  NL_TEST_ASSERT(inSuite, encodedLen == 0);
+
+ // Methods that take a reader should still read from it,
+ // even if the output is suppressed by the null writer.
+ TLVReader emptyTlvReader;
+ emptyTlvReader.Init(ByteSpan());
+ err = writer.PutBitString(0, emptyTlvReader);
+ NL_TEST_ASSERT(inSuite, err == CHIP_ERROR_WRONG_TLV_TYPE);
+
+ emptyTlvReader.Init(ByteSpan());
+ err = writer.PutOctetString(kASN1TagClass_ContextSpecific, 123, emptyTlvReader);
+ NL_TEST_ASSERT(inSuite, err == CHIP_ERROR_WRONG_TLV_TYPE);
 }
 
 static void TestASN1_ASN1UniversalTime(nlTestSuite * inSuite, void * inContext)