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#include "php_snuffleupagus.h"
// condensed version of PHP's php_hash_do_hash_hmac() in ext/hash/hash.c
#if PHP_VERSION_ID < 80000
static inline void *php_hash_alloc_context(const php_hash_ops *ops) {
/* Zero out context memory so serialization doesn't expose internals */
return ecalloc(1, ops->context_size);
}
#endif
static zend_string *sp_do_hash_hmac_sha256(char *data, size_t data_len, char *key, size_t key_len)
{
#if PHP_VERSION_ID < 80000
const php_hash_ops *ops = php_hash_fetch_ops(ZEND_STRL("sha256"));
#else
zend_string *algo = zend_string_init(ZEND_STRL("sha256"), 0);
const php_hash_ops *ops = php_hash_fetch_ops(algo);
zend_string_release_ex(algo, 0);
#endif
if (!ops || !ops->is_crypto) {
sp_log_err("hmac", "unsupported hash algorithm: sha256");
return NULL;
}
void *context = php_hash_alloc_context(ops);
unsigned char *K = emalloc(ops->block_size);
zend_string *digest = zend_string_alloc(ops->digest_size, 0);
php_hash_hmac_prep_key(K, ops, context, (unsigned char *) key, key_len);
php_hash_hmac_round((unsigned char *) ZSTR_VAL(digest), ops, context, K, (unsigned char *) data, data_len);
php_hash_string_xor_char(K, K, 0x6A, ops->block_size);
php_hash_hmac_round((unsigned char *) ZSTR_VAL(digest), ops, context, K, (unsigned char *) ZSTR_VAL(digest), ops->digest_size);
/* Zero the key */
ZEND_SECURE_ZERO(K, ops->block_size);
efree(K);
efree(context);
zend_string *hex_digest = zend_string_safe_alloc(ops->digest_size, 2, 0, 0);
php_hash_bin2hex(ZSTR_VAL(hex_digest), (unsigned char *) ZSTR_VAL(digest), ops->digest_size);
ZSTR_VAL(hex_digest)[2 * ops->digest_size] = 0;
zend_string_release_ex(digest, 0);
return hex_digest;
}
// ------------------
PHP_FUNCTION(sp_serialize) {
zif_handler orig_handler;
/* Call the original `serialize` function. */
orig_handler = zend_hash_str_find_ptr(SPG(sp_internal_functions_hook), ZEND_STRL("serialize"));
if (orig_handler) {
orig_handler(INTERNAL_FUNCTION_PARAM_PASSTHRU);
}
/* Compute the HMAC of the textual representation of the serialized data*/
zend_string *hmac = sp_do_hash_hmac_sha256(Z_STRVAL_P(return_value), Z_STRLEN_P(return_value), ZSTR_VAL(SPCFG(encryption_key)), ZSTR_LEN(SPCFG(encryption_key)));
if (!hmac) {
zend_bailout();
}
size_t len = Z_STRLEN_P(return_value) + ZSTR_LEN(hmac);
if (len < Z_STRLEN_P(return_value)) {
// LCOV_EXCL_START
sp_log_err("overflow_error",
"Overflow tentative detected in sp_serialize.");
zend_bailout();
// LCOV_EXCL_STOP
}
/* Append the computed HMAC to the serialized data. */
zend_string *orig_ret_str = return_value->value.str;
RETVAL_NEW_STR(zend_string_concat2(Z_STRVAL_P(return_value), Z_STRLEN_P(return_value), ZSTR_VAL(hmac), ZSTR_LEN(hmac)));
zend_string_free(orig_ret_str);
}
PHP_FUNCTION(sp_unserialize) {
zif_handler orig_handler;
char *buf = NULL;
char *serialized_str = NULL;
char *hmac = NULL;
size_t buf_len = 0;
zval *opts = NULL;
const sp_config_unserialize *config_unserialize = &(SPCFG(unserialize));
if (zend_parse_parameters(ZEND_NUM_ARGS(), "s|a", &buf, &buf_len, &opts) ==
FAILURE) {
RETURN_FALSE;
}
/* 64 is the length of HMAC-256 */
if (buf_len < 64) {
sp_log_drop("unserialize", "The serialized object is too small.");
}
hmac = buf + buf_len - 64;
serialized_str = ecalloc(buf_len - 64 + 1, 1);
memcpy(serialized_str, buf, buf_len - 64);
zend_string *expected_hmac = sp_do_hash_hmac_sha256(serialized_str, strlen(serialized_str), ZSTR_VAL(SPCFG(encryption_key)), ZSTR_LEN(SPCFG(encryption_key)));
unsigned int status = 0;
if (expected_hmac) {
for (uint8_t i = 0; i < 64; i++) {
status |= (hmac[i] ^ (ZSTR_VAL(expected_hmac))[i]);
}
} else { status = 1; }
if (0 == status) {
if ((orig_handler = zend_hash_str_find_ptr(SPG(sp_internal_functions_hook), ZEND_STRL("unserialize")))) {
orig_handler(INTERNAL_FUNCTION_PARAM_PASSTHRU);
}
} else {
if (config_unserialize->dump) {
sp_log_request(config_unserialize->dump,
config_unserialize->textual_representation);
}
if (true == config_unserialize->simulation) {
sp_log_simulation("unserialize", "Invalid HMAC for %s", serialized_str);
if ((orig_handler = zend_hash_str_find_ptr(SPG(sp_internal_functions_hook), ZEND_STRL("unserialize")))) {
orig_handler(INTERNAL_FUNCTION_PARAM_PASSTHRU);
}
} else {
sp_log_drop("unserialize", "Invalid HMAC for %s", serialized_str);
}
}
efree(serialized_str);
return;
}
int hook_serialize(void) {
TSRMLS_FETCH();
HOOK_FUNCTION("serialize", sp_internal_functions_hook, PHP_FN(sp_serialize));
HOOK_FUNCTION("unserialize", sp_internal_functions_hook,
PHP_FN(sp_unserialize));
return SUCCESS;
}
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