i wasn't using strict mode enough in make:
make strict
now it compiles cleanly. mostly removing
unused variables, fixing implicit conversions,
etc.
Signed-off-by: Leah Rowe <leah@libreboot.org>
where possible, try not to clobber sys errno. override
it only when relatively safe.
also: when a syscall succeeds, it may set errno. this
is rare, but permitted (nothing specified against it
in specs, and the specs say that errno is undefined
on success).
i'm not libc, but i'm wrapping around it, so i need
to be careful in how i handle the errno value.
also:
i removed the requirement for directories to be
executable, in mkhtemp.c, because this isn't required
and will only break certain setups.
in world_writeable and sticky, i made the checks stricter:
the faccessat check was being skipped on some paths, so
i've closed that loophole now.
i also generally cleaned up some code, as part of the errno
handling refactoring, where it made sense to do so, plus a
few other bits of code cleanup.
Signed-off-by: Leah Rowe <leah@libreboot.org>
i previously used error status and set return values
indirectly. i still do that, but where possible, i
also now return the real value.
this is because these string functions can no longer
return with error status; on error, they all abort.
this forces the program maintainer to keep their code
reliable, and removes the need to check the error status
after using syscalls, because these libc wrappers mitigate
that and make use of libc for you, including errors.
this is part of a general effort to promote safe use
of the C programming language, especially in libreboot!
Signed-off-by: Leah Rowe <leah@libreboot.org>
on the conditions where these functions encounter
an unexpected error, we currently return -1
this means that the caller must check. which means
the caller won't check. nobody does. i often forget.
force the caller (me) to be correct, instead.
the current calling convention is that the real
return value is stored in a pointer, provided inside
the function signature, on a given string function,
and the function's return value is merely an indicator.
this calling convention is retained for now; the next
patch will change it, such that the real value is also
the function's return value. this is more flexible.
Signed-off-by: Leah Rowe <leah@libreboot.org>
operate per word, not per byte
this is also done on sdup, which uses a slightly
inefficient method: the new string allocation is
that of the maximum size, rather than what we
need. for example, if you wanted a 20 character
string (21 including null), you would still allocate
4096 bytes if that was the maximum length.
it's a bit naughty, and i have half a mind to
keep sdup on the old implementation, but i'll leave
it be for now.
Signed-off-by: Leah Rowe <leah@libreboot.org>
spoiler alert: it's slow as molasses
part 2 will be presented at a later date
(yes, please don't fill 8GB of memory with
random data and hexdump it)
Signed-off-by: Leah Rowe <leah@libreboot.org>
the functions no longer return errors, so i don't
need to handle them.
furthermore, the handling in state.c is redundant,
so i've removed that too.
Signed-off-by: Leah Rowe <leah@libreboot.org>
make it more reliable; it can't segfault
now, under any circumstance. not even
once.
the problem arised when lbsetname was not
called in a program, before calling the
function: lbgetprogname. a segfault would
occur, due to it being NULL.
not every os/libc has getprogname, so i have
my own implementation.
Signed-off-by: Leah Rowe <leah@libreboot.org>
i now use a singleton hook function per program:
nvmutil, mkhtemp and lottery
call this at the startup of your program:
(void) errhook(exit_cleanup);
then provide that function. make it static,
so that each program has its own version.
if you're writing a program that handles lots
of files for example, and you want to do certain
cleanup on exit (including error exit), this can
be quite useful.
Signed-off-by: Leah Rowe <leah@libreboot.org>
i no longer care about openbsd 5.9. we assume unveil
is available, as has been the case for the past 12
years.
i use wrappers for unveil and pledge, which means that
i call them on every os. on OSes that don't have these,
i just return. it's somewhat inelegant, but also means
that i see errors more easily, e.g. misnamed variables
inside previous ifdef OpenBSD blocks.
Signed-off-by: Leah Rowe <leah@libreboot.org>
yes, a common thing in C programs is one or all
of the following:
* use after frees
* double free (on non-NULL pointer)
* over-writing currently used pointer (mem leak)
i try to reduce the chance of this in my software,
by running free() through a filter function,
free_if_not_null, that returns if a function
is being freed twice - because it sets NULL
after freeing, but will only free if it's not
null already.
this patch adds two functions: smalloc and vmalloc,
for strings and voids. using these makes the program
abort if:
* non-null pointer given for initialisation
* pointer to pointer is null (of course)
* size of zero given, for malloc (zero bytes)
i myself was caught out by this change, prompting
me to make the following fix in fs_dirname_basename()
inside lib/file.c:
- char *buf;
+ char *buf = NULL;
Yes.
Signed-off-by: Leah Rowe <leah@libreboot.org>
concatenate an arbitrary number of strings,
pointed to by char **
i'll use this and the next function, dcatn,
in an upcoming feature planned for mkhtemp.
Signed-off-by: Leah Rowe <leah@libreboot.org>
This will also be used in lbmk itself at some point,
which currently just uses regular mktemp, for tmpdir
handling during the build process.
Renamed util/nvmutil to util/libreboot-utils, which
now contains two tools. The new tool, mkhtemp, is a
hardened implementation of mktemp, which nvmutil
also uses now. Still experimental, but good enough
for nvmutil.
Mkhtemp attempts to provide TOCTOU resistance on
Linux, by using modern features in Linux such as
Openat2 (syscall) with O_EXCL and O_TMPFILE,
and many various security checks e.g.
inode/dev during creation. Checks are done constantly,
to try to detect race conditions. The code is very
strict about things like sticky bits in world writeable
directories, also ownership (it can be made to bar even
root access on files and directories it doesn't own).
It's a security-first implementation of mktemp, likely
even more secure than the OpenBSD mkstemp, but more
auditing and testing is needed - more features are
also planned, including a compatibility mode to make
it also work like traditional mktemp/mkstemp. The
intention, once this becomes stable, is that it will
become a modern drop-in replacement for mkstemp on
Linux and BSD systems.
Some legacy code has been removed, and in general
cleaned up. I wrote mkhtemp for nvmutil, as part of
its atomic write behaviour, but mktemp was the last
remaining liability, so I rewrote that too!
Docs/manpage/website will be made for mkhtemp once
the code is mature.
Other changes have also been made. This is from another
experimental branch of Libreboot, that I'm pushing
early. For example, nvmutil's state machine has been
tidied up, moving more logic back into main.
Mktemp is historically prone to race conditions,
e.g. symlink attacks, directory replacement, remounting
during operation, all sorts of things. Mkhtemp has
been written to solve, or otherwise mitigate, that
problem. Mkhtemp is currently experimental and will
require a major cleanup at some point, but it
already works well enough, and you can in fact use
it; at this time, the -d, -p and -q flags are
supported, and you can add a custom template at
the end, e.g.
mkhtemp -p test -d
Eventually, I will make this have complete parity
with the GNU and BSD implementations, so that it is
fully useable on existing setups, while optionally
providing the hardening as well.
A lot of code has also been tidied up. I didn't
track the changes I made with this one, because
it was a major re-write of nvmutil; it is now
libreboot-utils, and I will continue to write
more programs in here over time. It's basically
now a bunch of hardened wrappers around various
libc functions, e.g. there is also a secure I/O
wrapper for read/write.
There is a custom randomisation function, rlong,
which simply uses arc4random or getrandom, on
BSD and Linux respectively. Efforts are made to
make it as reliable as possible, to the extent
that it never returns with failure; in the unlikely
event that it fails, it aborts. It also sleeps
between failure, to mitigate certain DoS attacks.
You can just go in util/libreboot-utils and
type make, then you will have the nvmutil and
mkhtemp binaries, which you can just use. It
all works. Everything was massively rewritten.
Signed-off-by: Leah Rowe <leah@libreboot.org>
Leah Rowe