Revert #67 and fix padding stripping

Author: paragonie-security

src/Base64.php

@@ -213,24 +213,24 @@ public static function decode(
                     'Incorrect padding'
                 );
             }
-        }
-
-        $encodedString = rtrim($encodedString, '=');
-        $srcLen = strlen($encodedString);
-
-        if (extension_loaded('sodium')) {
-            $variant = match(static::class) {
-                Base64::class => SODIUM_BASE64_VARIANT_ORIGINAL_NO_PADDING,
-                Base64UrlSafe::class => SODIUM_BASE64_VARIANT_URLSAFE_NO_PADDING,
-                default => 0,
-            };
-            if ($variant > 0) {
-                try {
-                    return sodium_base642bin($encodedString, $variant);
-                } catch (SodiumException $ex) {
-                    throw new RangeException($ex->getMessage(), $ex->getCode(), $ex);
+            if (extension_loaded('sodium')) {
+                $variant = match(static::class) {
+                    Base64::class => SODIUM_BASE64_VARIANT_ORIGINAL_NO_PADDING,
+                    Base64UrlSafe::class => SODIUM_BASE64_VARIANT_URLSAFE_NO_PADDING,
+                    default => 0,
+                };
+                if ($variant > 0) {
+                    try {
+                        return sodium_base642bin(substr($encodedString, 0, $srcLen), $variant);
+                    } catch (SodiumException $ex) {
+                        throw new RangeException($ex->getMessage(), $ex->getCode(), $ex);
+                    }
                 }
             }
+        } else {
+            // Just remove all padding.
+            $encodedString = rtrim($encodedString, '=');
+            $srcLen = strlen($encodedString);
         }
 
         $err = 0;