Fix/xmlsecuritykey type hardening (#286)

* Harden XMLSecEnc against PHP 8 null fatals

Guard encrypt/decrypt and EncryptedKey construction against null DOM
nodes and failed crypto returns; tighten PHPDoc and changelog.

* Harden XMLSecurityKey types and null/false handling.

Tighten cryptParams/key typing, fail closed on unreadable key files and
oversized convertRSA input, and validate RSA/symmetric crypto results so
static analysis and failure paths stay consistent.

* Normalize decrypt exceptions and harden empty RSA ASN.1 input.

Catch phpseclib throws on symmetric/RSA decrypt so failures always surface
as Failure decrypting Data, and reject empty convertRSA inputs; add coverage
for both.

* Make decrypt-failure-uniform.phpt resilient to CI OpenSSL noise.

Silence display errors and allow optional STDERR between assertions so
PHPUnit PHPT runs do not fail when OpenSSL writes padding diagnostics.

* Migrate phpunit.xml to the PHPUnit 9.6 configuration schema.

Author: robrichards

CHANGELOG.txt

@@ -27,7 +27,10 @@ Security Improvements:
   DEFAULT_KEY_ALGORITHMS / DEFAULT_DATA_ALGORITHMS presets)
 - Use a single generic "Failure decrypting Data" error for all decryption
   failures (bad padding, cipher error, failed RSA unwrap) so callers cannot
-  build a CBC padding oracle from distinguishable errors
+  build a CBC padding oracle from distinguishable errors. Catch and normalize
+  phpseclib throws (LengthException, BadDecryptionException, RuntimeException,
+  etc.) on symmetric and RSA decrypt paths so exception type/message cannot
+  form a ciphertext-validity oracle either.
 - Add verifyDocument(): safe-by-default signature verification that requires a
   caller-pinned key (never trusts KeyInfo), enforces a SignatureMethod/DigestMethod
   algorithm allowlist, fails closed on unvalidated references, and returns the

phpunit.xml

@@ -1,7 +1,8 @@
-<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/6.5/phpunit.xsd">
-	<filter>
-		<whitelist addUncoveredFilesFromWhitelist="false">
+<?xml version="1.0"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.6/phpunit.xsd">
+	<coverage includeUncoveredFiles="false">
+		<include>
 			<directory suffix=".php">src</directory>
-		</whitelist>
-	</filter>
+		</include>
+	</coverage>
 </phpunit>