[PATCH 0/8] tools/nolibc: add support for stack protector

Willy Tarreau
2023-03-25T15:45:57Z

Hello Paul,

This is essentially Thomas' work so instead of paraphrasing his work,
I'm pasting his description below. I've tested his changes on all
supported archs, applied a tiny modification with his permission
to continue to support passing CFLAGS, and for me this is all fine.
In a short summary this adds support for stack protector to i386 and
x86_64 in nolibc, and the accompanying test to the selftest program.

A new test category was added, "protection", which currently has a
single test. Archs that support it will report "OK" there and those
that do not will report "SKIPPED", as is already the case for tests
that cannot be run.

This was applied on top of your dev.2023.03.20a branch. I'm reasonably
confident with the nature of the changes, so if your queue for 6.4 is
not closed yet, it can be a good target, otherwise 6.5 will be fine as
well.

Thanks in advance!
Willy

Thomas' description below:

This is useful when using nolibc for security-critical tools.
Using nolibc has the advantage that the code is easily auditable and
sandboxable with seccomp as no unexpected syscalls are used.
Using compiler-assistent stack protection provides another security
mechanism.

For this to work the compiler and libc have to collaborate.

This patch adds the following parts to nolibc that are required by the
compiler:

* __stack_chk_guard: random sentinel value
* __stack_chk_fail: handler for detected stack smashes

In addition an initialization function is added that randomizes the
sentinel value.

Only support for global guards is implemented.
Register guards are useful in multi-threaded context which nolibc does
not provide support for.

Link: https://lwn.net/Articles/584225/

Thomas Weißschuh (8):
tools/nolibc: add definitions for standard fds
tools/nolibc: add helpers for wait() signal exits
tools/nolibc: tests: constify test_names
tools/nolibc: add support for stack protector
tools/nolibc: tests: fold in no-stack-protector cflags
tools/nolibc: tests: add test for -fstack-protector
tools/nolibc: i386: add stackprotector support
tools/nolibc: x86_64: add stackprotector support

tools/include/nolibc/Makefile | 4 +-
tools/include/nolibc/arch-i386.h | 7 ++-
tools/include/nolibc/arch-x86_64.h | 5 ++
tools/include/nolibc/nolibc.h | 1 +
tools/include/nolibc/stackprotector.h | 53 ++++++++++++++++
tools/include/nolibc/types.h | 2 +
tools/include/nolibc/unistd.h | 5 ++
tools/testing/selftests/nolibc/Makefile | 11 +++-
tools/testing/selftests/nolibc/nolibc-test.c | 64 +++++++++++++++++++-
9 files changed, 144 insertions(+), 8 deletions(-)
create mode 100644 tools/include/nolibc/stackprotector.h

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2.17.5