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Properly initialize AEAD cipher flags in OpenSSL backend #20853

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Properly initialize AEAD cipher flags in OpenSSL backend #20853

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7de1357
properly initialize AEAD cipher flags in OpenSSL backend
jordikroon Jan 6, 2026
59cba53
allow null AAD parameter in openssl_encrypt/decrypt
jordikroon Jan 7, 2026
ca12f45
Check for EVP_CIPH_SIV_MODE in switch
jordikroon Jan 12, 2026
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4 changes: 2 additions & 2 deletions ext/openssl/openssl.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4481,7 +4481,7 @@ PHP_FUNCTION(openssl_encrypt)
zend_string *ret;
zval *tag = NULL;

if (zend_parse_parameters(ZEND_NUM_ARGS(), "sss|lszsl", &data, &data_len, &method, &method_len,
if (zend_parse_parameters(ZEND_NUM_ARGS(), "sss|lszs!l", &data, &data_len, &method, &method_len,
&password, &password_len, &options, &iv, &iv_len, &tag, &aad, &aad_len, &tag_len) == FAILURE) {
RETURN_THROWS();
}
Expand All @@ -4503,7 +4503,7 @@ 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|lss!s", &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();
}
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4 changes: 2 additions & 2 deletions ext/openssl/openssl.stub.php
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Expand Up @@ -662,9 +662,9 @@ function openssl_digest(string $data, string $digest_algo, bool $binary = false)
/**
* @param string $tag
*/
function openssl_encrypt(#[\SensitiveParameter] string $data, string $cipher_algo, #[\SensitiveParameter] string $passphrase, int $options = 0, string $iv = "", &$tag = null, string $aad = "", int $tag_length = 16): string|false {}
function openssl_encrypt(#[\SensitiveParameter] string $data, string $cipher_algo, #[\SensitiveParameter] 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, #[\SensitiveParameter] string $passphrase, int $options = 0, string $iv = "", ?string $tag = null, string $aad = ""): string|false {}
function openssl_decrypt(string $data, string $cipher_algo, #[\SensitiveParameter] string $passphrase, int $options = 0, string $iv = "", ?string $tag = null, ?string $aad = ""): string|false {}

function openssl_cipher_iv_length(string $cipher_algo): int|false {}

Expand Down
6 changes: 3 additions & 3 deletions ext/openssl/openssl_arginfo.h
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10 changes: 8 additions & 2 deletions ext/openssl/openssl_backend_common.c
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Expand Up @@ -1637,10 +1637,14 @@ void php_openssl_load_cipher_mode(struct php_openssl_cipher_mode *mode, const EV
{
int cipher_mode = EVP_CIPHER_mode(cipher_type);
memset(mode, 0, sizeof(struct php_openssl_cipher_mode));

switch (cipher_mode) {
case EVP_CIPH_GCM_MODE:
case EVP_CIPH_CCM_MODE:
/* We check for EVP_CIPH_OCB_MODE, because LibreSSL does not support it. */
/* We check for EVP_CIPH_SIV_MODE and EVP_CIPH_SIV_MODE, because LibreSSL does not support it. */
#ifdef EVP_CIPH_SIV_MODE
case EVP_CIPH_SIV_MODE:
#endif
#ifdef EVP_CIPH_OCB_MODE
case EVP_CIPH_OCB_MODE:
/* For OCB mode, explicitly set the tag length even when decrypting,
Expand Down Expand Up @@ -1797,7 +1801,9 @@ zend_result php_openssl_cipher_update(const EVP_CIPHER *cipher_type,
return FAILURE;
}

if (mode->is_aead && !EVP_CipherUpdate(cipher_ctx, NULL, &i, (const unsigned char *) aad, (int) aad_len)) {
/* Only pass AAD to OpenSSL if caller provided it.
This makes NULL mean zero AAD items, while "" with len 0 means one empty AAD item. */
if (mode->is_aead && aad != NULL && !EVP_CipherUpdate(cipher_ctx, NULL, &i, (const unsigned char *)aad, (int)aad_len)) {
Comment on lines +1804 to +1806
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@bukka bukka Jan 12, 2026

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Is this for SIV or is this for all modes. I thought that empty string won't make difference but I guess it might.

In general allowing null should be fine for master so it's not really a problem. Just want to know the reasoning as I haven't checked this propertly.

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@jordikroon jordikroon Jan 12, 2026

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Only SIV produces different outputs for aad = null and add = "". Other modes produce the same output.
From my understanding this is because in SIV mode aad could be a vector list. Thus null here means an empty vector list. And I don't believe we need to support multiple vectors as aad. Because then we would need to change $aad to string|array.

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@bukka bukka Jan 12, 2026 •
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ah ok. It would be good to check if skipping actually works for ccm, gcm and ocb (using null argument). It might make sense to potentially limit it just to SIV and treat null as "" for other modes.

php_openssl_store_errors();
php_error_docref(NULL, E_WARNING, "Setting of additional application data failed");
return FAILURE;
Expand Down
47 changes: 47 additions & 0 deletions ext/openssl/tests/gh20851_aad_empty.phpt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,47 @@
--TEST--
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@bukka bukka Jan 12, 2026

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Could you actually change it to a single test for encryption and decryption that will look like https://github.com/jordikroon/php-src/blob/ca12f45a76f3242953e7e27a9b64e509e9f518e2/ext/openssl/tests/openssl_decrypt_gcm.phpt
and
https://github.com/jordikroon/php-src/blob/ca12f45a76f3242953e7e27a9b64e509e9f518e2/ext/openssl/tests/openssl_encrypt_gcm.phpt

Please name it in a similar way and use the standard test vectors. It will also match the ccm and ocb tests...

openssl: AES-256-SIV AEAD tag and AAD roundtrip
--EXTENSIONS--
openssl
--FILE--
<?php
$algo = 'aes-256-siv';
$key = str_repeat('1', 64);
$tag = '';
$aad = '';
$input = 'Hello world!';

$ciphertext = openssl_encrypt(
'Hello world!',
$algo,
$key,
OPENSSL_RAW_DATA,
'', // IV is empty for this cipher in PHP
$tag, // gets filled with the SIV
$aad,
16
);

echo 'input: ' . $input . PHP_EOL;
echo 'tag: ' . bin2hex($tag) . PHP_EOL;
echo 'ciphertext: ' . bin2hex($ciphertext) . PHP_EOL;
echo 'combined: ' . bin2hex($tag . $ciphertext) . PHP_EOL;

$dec = openssl_decrypt(
$ciphertext,
$algo,
$key,
OPENSSL_RAW_DATA,
'',
$tag,
$aad
);

echo 'decrypted: ' . var_export($dec, true) . PHP_EOL;
?>
--EXPECTF--
input: Hello world!
tag: f6c98e3e785947502a09994d2757f9c1
ciphertext: a430a41a9bc089fa45ad27be
combined: f6c98e3e785947502a09994d2757f9c1a430a41a9bc089fa45ad27be
decrypted: 'Hello world!'

47 changes: 47 additions & 0 deletions ext/openssl/tests/gh20851_aad_null.phpt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,47 @@
--TEST--
openssl: AES-256-SIV AEAD tag and AAD roundtrip
--EXTENSIONS--
openssl
--FILE--
<?php
$algo = 'aes-256-siv';
$key = str_repeat('1', 64);
$tag = '';
$aad = null;
$input = 'Hello world!';

$ciphertext = openssl_encrypt(
'Hello world!',
$algo,
$key,
OPENSSL_RAW_DATA,
'', // IV is empty for this cipher in PHP
$tag, // gets filled with the SIV
$aad,
16
);

echo 'input: ' . $input . PHP_EOL;
echo 'tag: ' . bin2hex($tag) . PHP_EOL;
echo 'ciphertext: ' . bin2hex($ciphertext) . PHP_EOL;
echo 'combined: ' . bin2hex($tag . $ciphertext) . PHP_EOL;

$dec = openssl_decrypt(
$ciphertext,
$algo,
$key,
OPENSSL_RAW_DATA,
'',
$tag,
$aad
);

echo 'decrypted: ' . var_export($dec, true) . PHP_EOL;
?>
--EXPECTF--
input: Hello world!
tag: c06f0df087e2784c5560ce5d0b378311
ciphertext: 72fffba74d7bc3ddcceeb6d1
combined: c06f0df087e2784c5560ce5d0b37831172fffba74d7bc3ddcceeb6d1
decrypted: 'Hello world!'

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