AES GCM spec vs implementation discrepancy

[xanderbailey]

We're in the process of implementing the encryption spec in rust and python and have noticed something in the spec wording https://github.com/apache/iceberg/blob/1504ddd5d5119e934e7cbcaed82b9384caf35b82/format/gcm-stream-spec.md#cipher-block-structure The last block has a non-zero length <= BlockLength but Java AesGcmOutputStream will actually write an empty block and AesGcmInputFile will reject anything shorter than MIN_STREAM_LENGTH

iceberg/core/src/main/java/org/apache/iceberg/encryption/AesGcmInputFile.java

Lines 68 to 74 in 1504ddd

	public SeekableInputStream newStream() {
	long ciphertextLength = encryptedLength();
	Preconditions.checkState(
	ciphertextLength >= Ciphers.MIN_STREAM_LENGTH,
	"Invalid encrypted stream: %s is shorter than the minimum possible stream length",
	ciphertextLength);
	return new AesGcmInputStream(sourceFile.newStream(), ciphertextLength, dataKey, fileAADPrefix);

So java seems to disagree in both directions?

Link to python PR where this discussion came up apache/iceberg-python#3969