- PROBLEM DESCRIPTION: The ehframe saved on the stack was corrupted by the store of the stack guard canary value. When unwinding happens, a crash occurs. USERS AFFECTED: Users of -fstack-protector-strong and pthreads. Problem conclusion. The store of the canary word was corrected and the generated frame is now safe for unwinding.
- Only at system boot, as it happens with Mac OS and all versions of Android OS. SSP implemented in the Android security model uses static canaries ignoring the. All the functions (stack-protector-all): All the functions, regardless the type. Shen, H.: Add a new option “-fstack-protector-strong” (2012).
- Several distributions, including Gentoo, have patches which attempt to make glibc build when compiled with -fstack-protector. None of them that I have found actually work: at best, they make it crash instantly, because none of them suppress generation of stack guards around functions called before the guard is initialized (or even before ld-linux.so.2 has relocated itself).
- Hi all, I've worked this out with Apple support and wanted to share the outcome with you for future reference; It's confirmed that the bitcode version of your iOS app still has stack-protections in place (if it's built from Swift, or if it's built with a -fstack-protector-. flag in case of C or Objective-C code).
- Use Stack Protector All (stack Canaries For Macular Degeneration
- Use Stack Protector All (stack Canaries For Mac Os
- Use Stack Protector All (stack Canaries For Macs
Fstack-protector-all option adds a canary to all func-tions. However, it can incur a substantial use of stack space and run-time overhead in complex programs. The -fstack-protector-strong option provides a bet-ter trade-off between function coverage, run-time perfor-mance, and memory cost of stack canaries. It adds a canary.
![Use stack protector all (stack canaries for mac os Use stack protector all (stack canaries for mac os](https://www.informit.com/content/images/chap2_9780321822130/elementLinks/seacord_fig02-18.jpg)
The stack smashing protector is a feature implemented in gcc. When entering function, it stores the return address and frame pointer on stack. And then, it stores a specific guard value called “canary” on stack. when exit function, it checkes whether this canary value has been changed or not. If the value has been changed, it means buffer overflow is occurred. In this case, it calls “stack_chk_fail()” function which print error message and exit the program.
![Use Fstack Protector All (stack Canaries For Mac Use Fstack Protector All (stack Canaries For Mac](/uploads/1/1/8/9/118912567/942884081.png)
There are gcc options which enable/disable stack smashing protector.
- -fno-stack-protector : disables stack protection. This is default option.
- -fstack-protector : enables stack protection for vulnerable functions that contain buffers larger than 8 bytes. This includes functions that call “alloca”.
- -fstack-protector-all adds stack protection to all functions.
- -fstack-protector-strong : like -fstack-protector. but it includes additional functions that have local array definitions, or have references to local frame address.
In this post, let’s see about -fstack-protector-all.
source code
In this code, the element count of buf array is 2.
compile(generate executable file)
enables -fstack-protector-all.
compile(generate assembly code)
Use Stack Protector All (stack Canaries For Macular Degeneration
generates assembly code to see how stack smashing protector works.
output(with enabling -fstack-protector-all)
Here, input 3 or larger value to make buffer overflow.
Error message is printed and the program is exited.
generated assembly code
Let’s see “testFunc1” label
Use Stack Protector All (stack Canaries For Mac Os
Here is a snippet of testFunc1 and relevant code. I added @comment here.
Use Stack Protector All (stack Canaries For Macs
In gcc source code, __stack_chk_fail() is as below.