7fda8d2aa4
Reuse the top bits of _JB_SIGFLAG field previously used to store a boolean to store a cookie that's validated by [sig]longjmp to make it harder to use as a ROP gadget. Additionally, encrypt saved registers with the cookie so that an attacker can't modify a register's value to a specific value without knowing the cookie. Bug: http://b/23942752 Change-Id: Id0eb8d06916e89d5d776bfcaa9458f8826717ba3
65 lines
2.3 KiB
C++
65 lines
2.3 KiB
C++
/*
|
|
* Copyright (C) 2015 The Android Open Source Project
|
|
* All rights reserved.
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following conditions
|
|
* are met:
|
|
* * Redistributions of source code must retain the above copyright
|
|
* notice, this list of conditions and the following disclaimer.
|
|
* * Redistributions in binary form must reproduce the above copyright
|
|
* notice, this list of conditions and the following disclaimer in
|
|
* the documentation and/or other materials provided with the
|
|
* distribution.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
|
|
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
|
|
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
|
|
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
|
|
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
|
|
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
|
|
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
|
|
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
|
|
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
|
|
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
|
|
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
* SUCH DAMAGE.
|
|
*/
|
|
|
|
#include <assert.h>
|
|
#include <errno.h>
|
|
#include <stddef.h>
|
|
#include <stdlib.h>
|
|
#include <string.h>
|
|
#include <sys/auxv.h>
|
|
#include <sys/cdefs.h>
|
|
|
|
#include "private/libc_logging.h"
|
|
|
|
extern "C" __LIBC_HIDDEN__ int getentropy(void*, size_t);
|
|
static long __bionic_setjmp_cookie;
|
|
|
|
extern "C" void __bionic_setjmp_cookie_init() {
|
|
char* random_data = reinterpret_cast<char*>(getauxval(AT_RANDOM));
|
|
long value = *reinterpret_cast<long*>(random_data + 8);
|
|
|
|
// Mask off the last bit to store the signal flag.
|
|
__bionic_setjmp_cookie = value & ~1;
|
|
}
|
|
|
|
extern "C" long __bionic_setjmp_cookie_get(long sigflag) {
|
|
if (sigflag & ~1) {
|
|
__libc_fatal("unexpected sigflag value: %ld", sigflag);
|
|
}
|
|
|
|
return __bionic_setjmp_cookie | sigflag;
|
|
}
|
|
|
|
// Aborts if cookie doesn't match, returns the signal flag otherwise.
|
|
extern "C" long __bionic_setjmp_cookie_check(long cookie) {
|
|
if (__bionic_setjmp_cookie != (cookie & ~1)) {
|
|
__libc_fatal("setjmp cookie mismatch");
|
|
}
|
|
|
|
return cookie & 1;
|
|
}
|