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Build + LibC: Enable -fstack-protector-strong in user space

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Modify the user mode runtime to insert stack canaries to find stack corruptions.

The `-fstack-protector-strong` variant was chosen because it catches more
issues than vanilla `-fstack-protector`, but doesn't have substantial
performance impact like `-fstack-protector-all`.

Details:

    -fstack-protector enables stack protection for vulnerable functions that contain:

    * A character array larger than 8 bytes.
    * An 8-bit integer array larger than 8 bytes.
    * A call to alloca() with either a variable size or a constant size bigger than 8 bytes.

    -fstack-protector-strong enables stack protection for vulnerable functions that contain:

    * An array of any size and type.
    * A call to alloca().
    * A local variable that has its address taken.

Example of it catching corrupting in the `stack-smash` test:
```
courage ~ $ ./user/Tests/LibC/stack-smash
[+] Starting the stack smash ...
Error: Stack protector failure, stack smashing detected!
Shell: Job 1 (/usr/Tests/LibC/stack-smash) Aborted
```
This commit is contained in:
Brian Gianforcaro 2021-01-01 15:27:42 -08:00 • committed by Andreas Kling
parent bf3772362a
commit 06da50afc7
7 changed files with 124 additions and 13 deletions
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54
Userland/Tests/LibC/stack-smash.cpp Normal file
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/*
* Copyright (c) 2021, Brian Gianforcaro <b.gianfo@gmail.com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. 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 HOLDER 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 <cstdio>
// Note: Needs to be 'noline' so stack canary isn't optimized out.
static void __attribute__((noinline)) smasher(char* string)
{
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Warray-bounds"
for (int i = 0; i < 256; i++) {
string[i] = 'A';
}
#pragma GCC diagnostic pop
}
// Note: Needs to be 'noline' so stack canary isn't optimized out.
static void __attribute__((noinline)) stack_to_smash()
{
char string[8] = {};
smasher(string);
}
int main()
{
puts("[+] Starting the stack smash...");
stack_to_smash();
puts("[+] Stack smash wasn't detected!");
return 0;
}