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ext/openssl: openssl_encrypt() zend mm heap overflow on AES-WRAP-PAD … #22187

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ext/openssl: openssl_encrypt() zend mm heap overflow on AES-WRAP-PAD … #22187

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ext/openssl: openssl_encrypt() zend mm heap overflow on AES-WRAP-PAD …
devnexen May 29, 2026
6501136
add test
devnexen May 29, 2026
c0eecd5
fix test attempt
devnexen May 29, 2026
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17 changes: 15 additions & 2 deletions ext/openssl/openssl.c
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Original file line number Diff line number Diff line change
Expand Up @@ -7932,6 +7932,7 @@ static int php_openssl_cipher_update(const EVP_CIPHER *cipher_type,
const char *aad, size_t aad_len, int enc) /* {{{ */
{
int i = 0;
size_t outlen = data_len + EVP_CIPHER_block_size(cipher_type);

@ndossche ndossche Jun 15, 2026

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Do we risk an overflow of the sum? I also don't like how the data_len is downcasted to an int due to OpenSSL's API.
It means we need to cap data_len to INT_MAX (if that's not already the case).

@devnexen devnexen Jun 15, 2026

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No overflow risk. Both callers cap data_len to INT_MAX first (the PHP_OPENSSL_CHECK_SIZE_T_TO_INT_NULL_RETURN checks), so the worst case is INT_MAX + 2*block_size, which fits in size_t even on 32-bit. Same cap is what keeps the (int) casts safe.

@devnexen devnexen Jun 15, 2026

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I also do not appreciate the downcasting much, but I guess that s the long (hi)story of openssl existence showing :)

@ndossche ndossche Jun 15, 2026

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OKay, all good then


if (mode->is_single_run_aead && !EVP_CipherUpdate(cipher_ctx, NULL, &i, NULL, (int)data_len)) {
php_openssl_store_errors();
Expand All @@ -7945,7 +7946,19 @@ static int php_openssl_cipher_update(const EVP_CIPHER *cipher_type,
return FAILURE;
}

*poutbuf = zend_string_alloc((int)data_len + EVP_CIPHER_block_size(cipher_type), 0);
#ifdef EVP_CIPH_WRAP_MODE
if ((EVP_CIPHER_mode(cipher_type)) == EVP_CIPH_WRAP_MODE) {
/*
* RFC 5649 wrap-with-padding rounds the input up to the block size
* and prepends an integrity block, we reserve one extra block.
* See EVP_EncryptUpdate(3): wrap mode may write up to
* inl + cipher_block_size bytes.
*/
outlen += EVP_CIPHER_block_size(cipher_type);
}
#endif

*poutbuf = zend_string_alloc(outlen, false);

if (!EVP_CipherUpdate(cipher_ctx, (unsigned char*)ZSTR_VAL(*poutbuf),
&i, (const unsigned char *)data, (int)data_len)) {
Expand All @@ -7957,7 +7970,7 @@ static int php_openssl_cipher_update(const EVP_CIPHER *cipher_type,
}
*/
php_openssl_store_errors();
zend_string_release_ex(*poutbuf, 0);
zend_string_release_ex(*poutbuf, false);
return FAILURE;
}

Expand Down
32 changes: 32 additions & 0 deletions ext/openssl/tests/gh22186.phpt
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@@ -0,0 +1,32 @@
--TEST--
GH-22186 (Heap buffer overflow in openssl_encrypt with AES-WRAP-PAD)
--EXTENSIONS--
openssl
--SKIPIF--
<?php
/* openssl_get_cipher_methods() enumerates provider ciphers, but openssl_encrypt()
* resolves names via the legacy EVP_get_cipherbyname(), so on some builds the
* cipher is listed yet not usable. Probe the actual call path instead. */
if (!@openssl_encrypt("test", "aes-128-wrap-pad", str_repeat("k", 16),
OPENSSL_RAW_DATA | OPENSSL_DONT_ZERO_PAD_KEY, str_repeat("\0", 4))) {
die('skip aes-128-wrap-pad not usable on this OpenSSL build');
}
?>
--FILE--
<?php
$pass = str_repeat("k", 16);
$iv = str_repeat("\0", 4);

for ($i = 1; $i < 258; $i++) {
$data = str_repeat("a", $i);
$enc = openssl_encrypt($data, 'aes-128-wrap-pad', $pass, OPENSSL_RAW_DATA | OPENSSL_DONT_ZERO_PAD_KEY, $iv);
$dec = openssl_decrypt($enc, 'aes-128-wrap-pad', $pass, OPENSSL_RAW_DATA | OPENSSL_DONT_ZERO_PAD_KEY, $iv);
if ($dec !== $data) {
die("mismatch at $i\n");
}
}

echo "done\n";
?>
--EXPECT--
done
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