verify() with an empty signature throws FFI\Exception instead of OqsException #3

$sig = new OqsSig('ML-DSA-65');
$keys = $sig->generateKeypair();

$sig->verify('msg', '', $keys['public_key']);
// FFI\Exception: Cannot instantiate FFI\CData of zero size

verify() allocates the signature buffer with $ffi->new('uint8_t[' . strlen($signature) . ']'), and PHP FFI rejects a zero-size allocation.

This matters because the README documents verify() as "Never throws for an invalid signature — only for malformed input lengths", and signatures are attacker-controlled input. Code following that contract with catch (OqsException) won't contain the exception, so an empty signature becomes an uncaught fatal error.

The message buffer already handles this case:

$msgBuf = $ffi->new('uint8_t[' . max(1, strlen($message)) . ']');

The same treatment applied to the signature buffer (passing the real length to OQS_SIG_verify separately) fixes it. An explicit length check that returns false would work too — a zero-length signature is never valid for any supported algorithm.

Non-empty malformed signatures behave correctly: a 1-byte signature and an oversized signature both return false as expected.

Reproduced with liboqs 0.16.0 (shared build), PHP 8.5.8 with FFI, macOS/arm64.

🤖 Generated with Claude Code