Executable Stack

[claudioandre-br]

We now have some programs that have executable stack regions

Oh, indeed. We should have expected that when we let extra asm files into the tree.

While we keep the yasm files at all, the proper fix would be to add the equivalent of these to those:

$ tail -3 src/x86.S
#if defined(__ELF__) && defined(__linux__)
.section .note.GNU-stack,"",@progbits
#endif

... hoping that yasm does support specifying this in some way as well.

This is also a reason for us to get rid of yasm usage sooner.

---

See also openwall/john-packages#657 (comment)

[magnumripper]

Executable stack is fun and profit 😎

I should focus on #4314, hopefully it's not too much work.

[magnumripper]

While we keep the yasm files at all, the proper fix would be to add the equivalent of these to those:

$ tail -3 src/x86.S
#if defined(__ELF__) && defined(__linux__)
.section .note.GNU-stack,"",@progbits
#endif

@claudioandre-br can you check if the branch magnumripper/yasm-no-exec-stack fixes the problem? Right now I sit in a place lacking linux/yasm (and super doesn't seem to have yasm anywhere).

It adds this to the asm files:

%ifidn __OUTPUT_FORMAT__,elf
section .note.GNU-stack noalloc noexec nowrite progbits
%endif
%ifidn __OUTPUT_FORMAT__,elf32
section .note.GNU-stack noalloc noexec nowrite progbits
%endif
%ifidn __OUTPUT_FORMAT__,elf64
section .note.GNU-stack noalloc noexec nowrite progbits
%endif

I got that from https://wiki.gentoo.org/wiki/Hardened/GNU_stack_quickstart#Causes_of_executable_stack_markings and it says it's for nasm/yasm.

@solardiz does it look right? I'm not sure if/why noalloc and nowrite should be there.

[claudioandre-br]

Testing it!

[claudioandre-br]

It works (no files with executable stack was found):

$ john --test --format=o5logon
Will run 8 OpenMP threads
Benchmarking: o5logon, Oracle O5LOGON protocol [SHA1 AES 32/64]... (8xOMP) DONE
Many salts:	27787K c/s real, 3510K c/s virtual
Only one salt:	16269K c/s real, 2055K c/s virtual

Versus:

Will run 8 OpenMP threads
Benchmarking: o5logon, Oracle O5LOGON protocol [SHA1 AES 32/64]... (8xOMP) DONE
Many salts:	7684K c/s real, 1067K c/s virtual
Only one salt:	6053K c/s real, 849072 c/s virtual