This change introduces the nointernet() function which may be called to
prevent a process and its descendants from communicating with publicly
routable Internet addresses. GNU Make has been modified to always call
this function. In the future Landlock Make will have a way to whitelist
subnets to override this behavior, or disable it entirely. Support is
available for Linux only. Our firewall does not require root access.
Calling nointernet() will return control to the caller inside a new
process that has a SECCOMP BPF filter installed, which traps network
related system calls. Your original process then becomes a permanent
ptrace() supervisor that monitors all processes and threads descending
from the returned child. Whenever a networking system call happens the
kernel will stop the process and wakes up the monitor, which then peeks
into the child memory to read the sockaddr_in to determine if it's ok.
The downside to doing this is that there can be only one supervisor at a
time using ptrace() on a process. So this firewall won't be enabled if
you run make under strace or inside gdb. It also makes testing tricky.
The earlier iterations did too much guesswork when it came to things
like stderr logging and syscall origin verification. This change will
make things more conformant to existing practices. The __pledge_mode
extension now can be configured in a better way.
There's also a new `-q` flag added to pledge.com, e.g.
o//tool/build/pledge.com -qv. ls
Is a good way to disable warnings about `tty` access attempts.
This change also removes the futimens() call on the Landlock Make output
file workaround, since it caused problems with commands like fixupobj
which modify-in-place. It turns out if a file is opened for writing and
then no writes actually occur, then the modified time doesn't change.
- 10.5% reduction of o//depend dependency graph
- 8.8% reduction in latency of make command
- Fix issue with temporary file cleanup
There's a new -w option in compile.com that turns off the recent
Landlock output path workaround for "good commands" which do not
unlink() the output file like GNU tooling does.
Our new GNU Make unveil sandboxing appears to have zero overhead
in the grand scheme of things. Full builds are pretty fast since
the only thing that's actually slowed us down is probably libcxx
make -j16 MODE=rel
RL: took 85,732,063µs wall time
RL: ballooned to 323,612kb in size
RL: needed 828,560,521µs cpu (11% kernel)
RL: caused 39,080,670 page faults (99% memcpy)
RL: 350,073 context switches (72% consensual)
RL: performed 0 reads and 11,494,960 write i/o operations
pledge() and unveil() no longer consider ENOSYS to be an error.
These functions have also been added to Python's cosmo module.
This change also removes some WIN32 APIs and System Five magnums
which we're not using and it's doubtful anyone else would be too
This change fixes Landlock Make so that only the output target file is
unveiled, rather than unveiling the directory that contains it. This
gives us a much stronger sandbox. It also helped identify problematic
build code in our repo that should have been using o/tmp instead.
Landlock isn't able to let us unveil files that don't exist. Even if
they do, then once a file is deleted, the sandboxing for it goes away.
This caused problems for Landlock Make because tools like GNU LD will
repeatedly delete and recreate the output file. This change uses the
compile.com wrapper to ensure on changes happen to the output inode.
New binary available on https://justine.lol/make/Fixes#528
We're now able to drop both `exec` and `prot_exec` privileges
automatically when launching glibc dynamic executables. We also have
really outstanding standard error logging now, that explains which
promises are needed, even in cases where `exec` is used.
- We now kill the program on violations like OpenBSD
- We now print a message explaining which promise is needed
- This change also fixes a linkage bug with thread local storage
- Your sigaction() handlers should now be more thread safe
A new `__pledge_mode` global has been introduced to make pledge() more
customizable on Linux. For example:
__attribute__((__constructor__)) static void init(void) {
__pledge_mode = SECCOMP_RET_ERRNO | EPERM;
}
Can be used to restore our old permissive pledge() behavior.
- Make memmem() faster
- Make readdir() thread safe
- Remove 64kb limit from mkdeps.com
- Add old crypt() function from Musl
- Improve new fix-third-party.py tool
- Improve libc/isystem/ headers and fix bugs
The whole repository is now buildable with GNU Make Landlock sandboxing.
This proves that no Makefile targets exist which touch files other than
their declared prerequisites. In order to do this, we had to:
1. Stop code morphing GCC output in package.com and instead run a
newly introduced FIXUPOBJ.COM command after GCC invocations.
2. Disable all the crumby Python unit tests that do things like create
files in the current directory, or rename() files between folders.
This ended up being a lot of tests, but most of them are still ok.
3. Introduce an .UNSANDBOXED variable to GNU Make to disable Landlock.
We currently only do this for things like `make tags`.
4. This change deletes some GNU Make code that was preventing the
execve() optimization from working. This means it should no longer
be necessary in most cases for command invocations to be indirected
through the cocmd interpreter.
5. Missing dependencies had to be declared in certain places, in cases
where they couldn't be automatically determined by MKDEPS.COM
6. The libcxx header situation has finally been tamed. One of the
things that makes this difficult is MKDEPS.COM only wants to
consider the first 64kb of a file, in order to go fast. But libcxx
likes to have #include lines buried after huge documentation.
7. An .UNVEIL variable has been introduced to GNU Make just in case
we ever wish to explicitly specify additional things that need to
be whitelisted which aren't strictly prerequisites. This works in
a manner similar to the recently introduced .EXTRA_PREREQS feature.
There's now a new build/bootstrap/make.com prebuilt binary available. It
should no longer be possible to write invalid Makefile code.
Doing this improves message latency and throughput, since we're
consolidating the 504 bytes of static memory which has the most
churn into a single place.
