From 92d0cd837e510e03cc051e4fde5781252c107f5c Mon Sep 17 00:00:00 2001
From: terrafrost <terrafrost@gmail.com>
Date: Fri, 17 Apr 2020 09:06:48 -0500
Subject: [PATCH] PKCS8: add extractEncryptionAlgorithm() method

---
 phpseclib/Crypt/Common/Formats/Keys/PKCS8.php | 81 ++++++++++++++-----
 1 file changed, 62 insertions(+), 19 deletions(-)

diff --git a/phpseclib/Crypt/Common/Formats/Keys/PKCS8.php b/phpseclib/Crypt/Common/Formats/Keys/PKCS8.php
index 6625ec9b..638a58bf 100644
--- a/phpseclib/Crypt/Common/Formats/Keys/PKCS8.php
+++ b/phpseclib/Crypt/Common/Formats/Keys/PKCS8.php
@@ -332,25 +332,7 @@ abstract class PKCS8 extends PKCS
      */
     protected static function load($key, $password = '')
     {
-        self::initialize_static_variables();
-
-        if (!Strings::is_stringable($key)) {
-            throw new \UnexpectedValueException('Key should be a string - not a ' . gettype($key));
-        }
-
-        if (self::$format != self::MODE_DER) {
-            $decoded = ASN1::extractBER($key);
-            if ($decoded !== false) {
-                $key = $decoded;
-            } elseif (self::$format == self::MODE_PEM) {
-                throw new \UnexpectedValueException('Expected base64-encoded PEM format but was unable to decode base64 text');
-            }
-        }
-
-        $decoded = ASN1::decodeBER($key);
-        if (empty($decoded)) {
-            throw new \RuntimeException('Unable to decode BER');
-        }
+        $decoded = self::preParse($key);
 
         $meta = [];
 
@@ -655,4 +637,65 @@ abstract class PKCS8 extends PKCS
                chunk_split(Base64::encode($key), 64) .
                "-----END PUBLIC KEY-----";
     }
+
+    /**
+     * Perform some preliminary parsing of the key
+     *
+     * @param string $key
+     * @return array
+     */
+    private static function preParse(&$key)
+    {
+        self::initialize_static_variables();
+
+        if (!Strings::is_stringable($key)) {
+            throw new \UnexpectedValueException('Key should be a string - not a ' . gettype($key));
+        }
+
+        if (self::$format != self::MODE_DER) {
+            $decoded = ASN1::extractBER($key);
+            if ($decoded !== false) {
+                $key = $decoded;
+            } elseif (self::$format == self::MODE_PEM) {
+                throw new \UnexpectedValueException('Expected base64-encoded PEM format but was unable to decode base64 text');
+            }
+        }
+
+        $decoded = ASN1::decodeBER($key);
+        if (empty($decoded)) {
+            throw new \RuntimeException('Unable to decode BER');
+        }
+
+        return $decoded;
+    }
+
+    /**
+     * Returns the encryption parameters used by the key
+     *
+     * @param string $key
+     * @return array
+     */
+    public static function extractEncryptionAlgorithm($key)
+    {
+        $decoded = self::preParse($key);
+
+        $r = ASN1::asn1map($decoded[0], ASN1\Maps\EncryptedPrivateKeyInfo::MAP);
+        if (!is_array($r)) {
+            throw new \RuntimeException('Unable to parse using EncryptedPrivateKeyInfo map');
+        }
+
+        if ($r['encryptionAlgorithm']['algorithm'] == 'id-PBES2') {
+            $decoded = ASN1::decodeBER($r['encryptionAlgorithm']['parameters']->element);
+            $r['encryptionAlgorithm']['parameters'] = ASN1::asn1map($decoded[0], ASN1\Maps\PBES2params::MAP);
+
+            $kdf = &$r['encryptionAlgorithm']['parameters']['keyDerivationFunc'];
+            switch ($kdf['algorithm']) {
+                case 'id-PBKDF2':
+                    $decoded = ASN1::decodeBER($kdf['parameters']->element);
+                    $kdf['parameters'] = ASN1::asn1map($decoded[0], Maps\PBKDF2params::MAP);
+            }
+        }
+
+        return $r['encryptionAlgorithm'];
+    }
 }