Currently, -Wall and -Wextra override previously passed flags like
-Wno-unused-parameter. This reorders them to be passed before any
optional flags. -Wsign-compare is part of -Wextra and therefore dropped.
-nostdlib is a link-stage flag and dropped as it is already part of
efi_ldflags.
Device paths are a packed data structure and the UEFI spec is clear that
members may be misaligned.
In this case all accesses are aligned except for the signature. We can
simply memcpy it instead of making a whole (aligned) copy of the device
path.
This drops the unused xnew0 and xallocate_zero_pool as there is only two
users of it. _cleanup_freepool_ will be phased out once the types in the
declarations are changed/renamed.
A future commit will add support for unicode collation protocol that
allows case folding and comparing strings with locale awareness. But it
only operates on whole strings, so fnmatch cannot use those without a
heavy cost. Instead we just case fold the patterns instead (the IDs we
try to match are already lower case).
The casts in this and the next few commits are curently necessary
because CHAR8 is defined as uint8_t in gnu-efi, while char is signed.
Once we switch from gnu-efi typedefs to stdint types, the casts
will be dropped.
We currently have a convoluted and complex selection of which random
numbers to use. We can simplify this down to two functions that cover
all of our use cases:
1) Randomness for crypto: this one needs to wait until the RNG is
initialized. So it uses getrandom(0). If that's not available, it
polls on /dev/random, and then reads from /dev/urandom. This function
returns whether or not it was successful, as before.
2) Randomness for other things: this one uses getrandom(GRND_INSECURE).
If it's not available it uses getrandom(GRND_NONBLOCK). And if that
would block, then it falls back to /dev/urandom. And if /dev/urandom
isn't available, it uses the fallback code. It never fails and
doesn't return a value.
These two cases match all the uses of randomness inside of systemd.
I would prefer to make both of these return void, and get rid of the
fallback code, and simply assert in the incredibly unlikely case that
/dev/urandom doesn't exist. But Luca disagrees, so this commit attempts
to instead keep case (1) returning a return value, which all the callers
already check, and fix the fallback code in (2) to be less bad than
before.
For the less bad fallback code for (2), we now use auxval and some
timestamps, together with various counters representing the invocation,
hash it all together and provide the output. Provided that AT_RANDOM is
secure, this construction is probably okay too, though notably it
doesn't have any forward secrecy. Fortunately, it's only used by
random_bytes() and not by crypto_random_bytes().
Jan Janssen
Yu Watanabe
Shreenidhi Shedi
Zbigniew Jędrzejewski-Szmek
Jason A. Donenfeld