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Introduction of timing attack safe bcmp implementation.

Browse Source 
Nothing new but to refactor usage b/w hash and password
extensions but using volatile pointers to be a bit safer,
allowing to expand its usage eventually.
This commit is contained in:
David Carlier 2019-09-20 16:42:47 +01:00
parent 8aa7e203ed
commit bfe6f9e66a
6 changed files with 52 additions and 19 deletions
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2
configure.ac
View File

@ -1616,7 +1616,7 @@ PHP_ADD_SOURCES(main, main.c snprintf.c spprintf.c \
php_ini_builder.c \
php_ini.c SAPI.c rfc1867.c php_content_types.c strlcpy.c \
strlcat.c explicit_bzero.c reentrancy.c php_variables.c php_ticks.c \
network.c php_open_temporary_file.c php_odbc_utils.c \
network.c php_open_temporary_file.c php_odbc_utils.c safe_bcmp.c \
output.c getopt.c php_syslog.c, -DZEND_ENABLE_STATIC_TSRMLS_CACHE=1)
PHP_ADD_SOURCES_X(main, fastcgi.c, -DZEND_ENABLE_STATIC_TSRMLS_CACHE=1, PHP_FASTCGI_OBJS, no)

13
ext/hash/hash.c
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@ -1111,9 +1111,7 @@ PHP_FUNCTION(hash_pbkdf2)
PHP_FUNCTION(hash_equals)
{
zval *known_zval, *user_zval;
char *known_str, *user_str;
int result = 0;
size_t j;
if (zend_parse_parameters(ZEND_NUM_ARGS(), "zz", &known_zval, &user_zval) == FAILURE) {
RETURN_THROWS();
@ -1130,17 +1128,8 @@ PHP_FUNCTION(hash_equals)
RETURN_THROWS();
}
if (Z_STRLEN_P(known_zval) != Z_STRLEN_P(user_zval)) {
RETURN_FALSE;
}
known_str = Z_STRVAL_P(known_zval);
user_str = Z_STRVAL_P(user_zval);
/* This is security sensitive code. Do not optimize this for speed. */
for (j = 0; j < Z_STRLEN_P(known_zval); j++) {
result |= known_str[j] ^ user_str[j];
}
result = php_safe_bcmp(Z_STR_P(known_zval), Z_STR_P(user_zval));
RETURN_BOOL(0 == result);
}

7
ext/standard/password.c
View File

@ -152,7 +152,6 @@ static bool php_password_bcrypt_needs_rehash(const zend_string *hash, zend_array
}
static bool php_password_bcrypt_verify(const zend_string *password, const zend_string *hash) {
size_t i;
int status = 0;
zend_string *ret = php_crypt(ZSTR_VAL(password), (int)ZSTR_LEN(password), ZSTR_VAL(hash), (int)ZSTR_LEN(hash), 1);
@ -160,7 +159,7 @@ static bool php_password_bcrypt_verify(const zend_string *password, const zend_s
return 0;
}
if (ZSTR_LEN(ret) != ZSTR_LEN(hash) || ZSTR_LEN(hash) < 13) {
if (ZSTR_LEN(hash) < 13) {
zend_string_free(ret);
return 0;
}
@ -169,9 +168,7 @@ static bool php_password_bcrypt_verify(const zend_string *password, const zend_s
* resistance towards timing attacks. This is a constant time
* equality check that will always check every byte of both
* values. */
for (i = 0; i < ZSTR_LEN(hash); i++) {
status |= (ZSTR_VAL(ret)[i] ^ ZSTR_VAL(hash)[i]);
}
status = php_safe_bcmp(ret, hash);
zend_string_free(ret);
return status == 0;

4
main/php.h
View File

@ -179,6 +179,10 @@ END_EXTERN_C()
#define explicit_bzero php_explicit_bzero
#endif
BEGIN_EXTERN_C()
PHPAPI int php_safe_bcmp(const zend_string *a, const zend_string *b);
END_EXTERN_C()
#ifndef HAVE_STRTOK_R
BEGIN_EXTERN_C()
char *strtok_r(char *s, const char *delim, char **last);

43
main/safe_bcmp.c Normal file
View File

@ -0,0 +1,43 @@
/*
+----------------------------------------------------------------------+
| Copyright (c) The PHP Group |
+----------------------------------------------------------------------+
| This source file is subject to version 3.01 of the PHP license, |
| that is bundled with this package in the file LICENSE, and is |
| available through the world-wide-web at the following url: |
| http://www.php.net/license/3_01.txt |
| If you did not receive a copy of the PHP license and are unable to |
| obtain it through the world-wide-web, please send a note to |
| license@php.net so we can mail you a copy immediately. |
+----------------------------------------------------------------------+
| Author: David Carlier <devnexen@gmail.com> |
+----------------------------------------------------------------------+
*/
#include "php.h"
#include <string.h>
/*
* Returns 0 if both inputs match, 1 if they don't.
* Returns -1 early if inputs do not have the same lengths.
*
*/
PHPAPI int php_safe_bcmp(const zend_string *a, const zend_string *b)
{
const volatile unsigned char *ua = (const volatile unsigned char *)ZSTR_VAL(a);
const volatile unsigned char *ub = (const volatile unsigned char *)ZSTR_VAL(b);
size_t i = 0;
int r = 0;
if (ZSTR_LEN(a) != ZSTR_LEN(b)) {
return -1;
}
while (i < ZSTR_LEN(a)) {
r |= ua[i] ^ ub[i];
++i;
}
return r;
}

2
win32/build/config.w32
View File

@ -265,7 +265,7 @@ ADD_SOURCES("main", "main.c snprintf.c spprintf.c getopt.c fopen_wrappers.c \
php_scandir.c php_ini.c SAPI.c rfc1867.c php_content_types.c strlcpy.c \
strlcat.c reentrancy.c php_variables.c php_ticks.c network.c \
php_open_temporary_file.c output.c internal_functions.c \
php_syslog.c php_odbc_utils.c");
php_syslog.c php_odbc_utils.c safe_bcmp.c");
ADD_FLAG("CFLAGS_BD_MAIN", "/D ZEND_ENABLE_STATIC_TSRMLS_CACHE=1");
if (VS_TOOLSET && VCVERS >= 1914) {
ADD_FLAG("CFLAGS_BD_MAIN", "/d2FuncCache1");