Fixed bug #81502

Allow $tag to be null. This is the value that openssl_encrypt()
sets it to for non-AEAD ciphers, so we should also accept this
as an input to openssl_decrypt().

Prior to PHP 8.1, null was accepted in weak mode due to the special
treatment of null arguments to internal functions.

Author: nikic

NEWS

@@ -22,6 +22,10 @@ PHP                                                                        NEWS
 - PgSQL:
   . Fixed bug #81509 (pg_end_copy still expects a resource). (Matteo)
 
+- OpenSSL:
+  . Fixed bug #81502 ($tag argument of openssl_decrypt() should accept
+    null/empty string). (Nikita)
+
 - Standard:
   . Fixed bug #81491 (Incorrectly using libsodium for argon2 hashing).
     (Dan Pock)

ext/openssl/openssl.c

@@ -7614,7 +7614,7 @@ PHP_FUNCTION(openssl_decrypt)
 	size_t data_len, method_len, password_len, iv_len = 0, tag_len = 0, aad_len = 0;
 	zend_string *ret;
 
-	if (zend_parse_parameters(ZEND_NUM_ARGS(), "sss|lsss", &data, &data_len, &method, &method_len,
+	if (zend_parse_parameters(ZEND_NUM_ARGS(), "sss|lss!s", &data, &data_len, &method, &method_len,
 					&password, &password_len, &options, &iv, &iv_len, &tag, &tag_len, &aad, &aad_len) == FAILURE) {
 		RETURN_THROWS();
 	}

ext/openssl/openssl.stub.php

@@ -236,7 +236,7 @@ function openssl_digest(string $data, string $digest_algo, bool $binary = false)
 /** @param string $tag */
 function openssl_encrypt(string $data, string $cipher_algo, string $passphrase, int $options = 0, string $iv = "", &$tag = null, string $aad = "", int $tag_length = 16): string|false {}
 
-function openssl_decrypt(string $data, string $cipher_algo, string $passphrase, int $options = 0, string $iv = "", string $tag = "", string $aad = ""): string|false {}
+function openssl_decrypt(string $data, string $cipher_algo, string $passphrase, int $options = 0, string $iv = "", ?string $tag = null, string $aad = ""): string|false {}
 
 function openssl_cipher_iv_length(string $cipher_algo): int|false {}
 

ext/openssl/openssl_arginfo.h

@@ -1,5 +1,5 @@
 /* This is a generated file, edit the .stub.php file instead.
- * Stub hash: 3ad007a0b29648c29051f9ee00fe43dd6f2a766d */
+ * Stub hash: 320aca9647019329a42dc3e7937420610a8a4419 */
 
 ZEND_BEGIN_ARG_WITH_RETURN_TYPE_INFO_EX(arginfo_openssl_x509_export_to_file, 0, 2, _IS_BOOL, 0)
 	ZEND_ARG_OBJ_TYPE_MASK(0, certificate, OpenSSLCertificate, MAY_BE_STRING, NULL)
@@ -342,7 +342,7 @@ ZEND_BEGIN_ARG_WITH_RETURN_TYPE_MASK_EX(arginfo_openssl_decrypt, 0, 3, MAY_BE_ST
 	ZEND_ARG_TYPE_INFO(0, passphrase, IS_STRING, 0)
 	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, options, IS_LONG, 0, "0")
 	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, iv, IS_STRING, 0, "\"\"")
-	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, tag, IS_STRING, 0, "\"\"")
+	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, tag, IS_STRING, 1, "null")
 	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, aad, IS_STRING, 0, "\"\"")
 ZEND_END_ARG_INFO()
 

ext/openssl/tests/openssl_decrypt_basic.phpt

@@ -25,6 +25,11 @@ $encrypted = openssl_encrypt($padded_data, $method, $password, OPENSSL_RAW_DATA|
 $output = openssl_decrypt($encrypted, $method, $password, OPENSSL_RAW_DATA|OPENSSL_ZERO_PADDING, $iv);
 var_dump(rtrim($output));
 
+$output2 = openssl_decrypt($encrypted, $method, $password, OPENSSL_RAW_DATA|OPENSSL_ZERO_PADDING, $iv, tag: '');
+var_dump($output2 === $output);
+$output3 = openssl_decrypt($encrypted, $method, $password, OPENSSL_RAW_DATA|OPENSSL_ZERO_PADDING, $iv, tag: null);
+var_dump($output3 === $output);
+
 if (in_array("bf-ecb", openssl_get_cipher_methods())) {
     // if we want to prefer variable length cipher setting
     $encrypted = openssl_encrypt($data, "bf-ecb", $password, OPENSSL_DONT_ZERO_PAD_KEY);
@@ -45,4 +50,6 @@ string(45) "openssl_encrypt() and openssl_decrypt() tests"
 string(45) "openssl_encrypt() and openssl_decrypt() tests"
 string(45) "openssl_encrypt() and openssl_decrypt() tests"
 bool(true)
+bool(true)
+bool(true)
 NULL