Refactor algorithm factories

Author: tvdijen

src/Alg/AbstractAlgorithmFactory.php

@@ -27,7 +27,7 @@ public function __construct(SymmetricKey $key, string $algId = C::BLOCK_ENC_AES2
 
 
     /**
-     * @inheritDoc
+     * @return string[]
      */
     public static function getSupportedAlgorithms(): array
     {

src/Alg/Encryption/AES.php

@@ -5,19 +5,36 @@
 namespace SimpleSAML\XMLSecurity\Alg\Encryption;
 
 use SimpleSAML\Assert\Assert;
-use SimpleSAML\XMLSecurity\Alg\AbstractAlgorithmFactory;
 use SimpleSAML\XMLSecurity\Constants as C;
 use SimpleSAML\XMLSecurity\Exception\BlacklistedAlgorithmException;
 use SimpleSAML\XMLSecurity\Exception\UnsupportedAlgorithmException;
 use SimpleSAML\XMLSecurity\Key\KeyInterface;
 
+use function array_key_exists;
+use function in_array;
+use function sprintf;
+
 /**
  * Factory class to create and configure encryption algorithms.
  *
  * @package simplesamlphp/xml-security
  */
-final class EncryptionAlgorithmFactory extends AbstractAlgorithmFactory
+final class EncryptionAlgorithmFactory
 {
+    /**
+     * A cache of algorithm implementations indexed by algorithm ID.
+     *
+     * @var array<string, \SimpleSAML\XMLSecurity\Alg\Encryption\EncryptionAlgorithmInterface>
+     */
+    protected static array $cache = [];
+
+    /**
+     * Whether the factory has been initialized or not.
+     *
+     * @var bool
+     */
+    protected static bool $initialized = false;
+
     /**
      * An array of blacklisted algorithms.
      *
@@ -30,44 +47,92 @@ final class EncryptionAlgorithmFactory extends AbstractAlgorithmFactory
     ];
 
     /**
-     * A cache of algorithm implementations indexed by algorithm ID.
+     * An array of default algorithms that can be used.
      *
-     * @var array<string, \SimpleSAML\XMLSecurity\Alg\Encryption\EncryptionAlgorithmInterface>
+     * @var class-string[]
      */
-    protected static array $cache = [];
+    private const SUPPORTED_DEFAULTS = [
+        TripleDES::class,
+        AES::class,
+    ];
+
 
     /**
-     * Whether the factory has been initialized or not.
+     * Build a factory that creates algorithms.
      *
-     * @var bool
+     * @param string[]|null $blacklist A list of algorithms forbidden for their use.
      */
-    protected static bool $initialized = false;
+    public function __construct(
+        protected ?array $blacklist = self::DEFAULT_BLACKLIST,
+    ) {
+        // initialize the cache for supported algorithms per known implementation
+        if (!self::$initialized && $blacklist !== null) {
+            foreach (self::SUPPORTED_DEFAULTS as $algorithm) {
+                foreach ($algorithm::getSupportedAlgorithms() as $algId) {
+                    if (array_key_exists($algId, self::$cache)) {
+                        /*
+                         * If the key existed before initialization, that means someone registered a handler for this
+                         * algorithm, so we should respect that and skip registering the default here.
+                         */
+                        continue;
+                    }
+                    self::$cache[$algId] = $algorithm;
+                }
+            }
+            self::$initialized = true;
+        }
+    }
 
 
     /**
-     * Build a factory that creates encryption algorithms.
+     * Get a new object implementing the given digital signature algorithm.
      *
-     * @param string[]|null $blacklist A list of algorithms forbidden for their use.
+     * @param string $algId The identifier of the algorithm desired.
+     * @param \SimpleSAML\XMLSecurity\Key\KeyInterface $key The key to use with the given algorithm.
+     *
+     * @return \SimpleSAML\XMLSecurity\Alg\Encryption\EncryptionAlgorithmInterface An object implementing the given
+     * algorithm.
+     *
+     * @throws \SimpleSAML\XMLSecurity\Exception\UnsupportedAlgorithmException If an error occurs, e.g. the given
+     * algorithm is blacklisted, unknown or the given key is not suitable for it.
      */
-    public function __construct(array $blacklist = null)
+    public function getAlgorithm(string $algId, KeyInterface $key): EncryptionAlgorithmInterface
     {
-        parent::__construct(
-            $blacklist ?? self::DEFAULT_BLACKLIST,
-            [
-                TripleDES::class,
-                AES::class,
-            ],
+        Assert::false(
+            ($this->blacklist !== null) && in_array($algId, $this->blacklist, true),
+            sprintf('Blacklisted algorithm: \'%s\'.', $algId),
+            BlacklistedAlgorithmException::class,
         );
+        Assert::keyExists(
+            self::$cache,
+            $algId,
+            sprintf('Unknown or unsupported algorithm: \'%s\'.', $algId),
+            UnsupportedAlgorithmException::class,
+        );
+
+        return new self::$cache[$algId]($key, $algId);
     }
 
 
     /**
-     * Get the name of the abstract class our algorithm implementations must extend.
+     * Register an implementation of some algorithm(s) for its use.
      *
-     * @return string
+     * @param class-string $className
      */
-    protected static function getExpectedParent(): string
+    public static function registerAlgorithm(string $className): void
     {
-        return EncryptionAlgorithmInterface::class;
+        Assert::implementsInterface(
+            $className,
+            EncryptionAlgorithmInterface::class,
+            sprintf(
+                'Cannot register algorithm "%s", must implement %s.',
+                $className,
+                EncryptionAlgorithmInterface::class,
+            ),
+        );
+
+        foreach ($className::getSupportedAlgorithms() as $algId) {
+            self::$cache[$algId] = $className;
+        }
     }
 }

src/Alg/Encryption/EncryptionAlgorithmFactory.php

@@ -26,7 +26,7 @@ public function __construct(SymmetricKey $key)
 
 
     /**
-     * @inheritDoc
+     * @return string[]
      */
     public static function getSupportedAlgorithms(): array
     {

src/Alg/Encryption/TripleDES.php

@@ -5,7 +5,6 @@
 namespace SimpleSAML\XMLSecurity\Alg\KeyTransport;
 
 use SimpleSAML\Assert\Assert;
-use SimpleSAML\XMLSecurity\Alg\Encryption\EncryptionAlgorithmInterface;
 use SimpleSAML\XMLSecurity\Backend;
 use SimpleSAML\XMLSecurity\Backend\EncryptionBackend;
 use SimpleSAML\XMLSecurity\Exception\UnsupportedAlgorithmException;
@@ -16,7 +15,7 @@
  *
  * @package simplesamlphp/xml-security
  */
-abstract class AbstractKeyTransporter implements EncryptionAlgorithmInterface
+abstract class AbstractKeyTransporter implements KeyTransportAlgorithmInterface
 {
     /** @var string */
     protected const DEFAULT_BACKEND = Backend\OpenSSL::class;