kernel 5.6 added support for a new flag for getrandom(): GRND_INSECURE.
If we set it we can get some random data out of the kernel random pool,
even if it is not yet initializated. This is great for us to initialize
hash table seeds and such, where it is OK if they are crap initially. We
used RDRAND for these cases so far, but RDRAND is only available on
newer CPUs and some archs. Let's now use GRND_INSECURE for these cases
as well, which means we won't needlessly delay boot anymore even on
archs/CPUs that do not have RDRAND.
Of course we never set this flag when generating crypto keys or uuids.
Which makes it different from RDRAND for us (and is the reason I think
we should keep explicit RDRAND support in): RDRAND we don't trust enough
for crypto keys. But we do trust it enough for UUIDs.
An ugly, ugly work-around for #11810. And no, we shouldn't have to do
this. This is something for AMD, the firmware or the kernel to
fix/work-around, not us. But nonetheless, this should do it for now.
Fixes: #11810
Otherwise, the fuzzers will fail to compile with MSan:
```
../../src/systemd/src/basic/random-util.c:64:40: error: use of undeclared identifier 'sucess'; did you mean 'success'?
msan_unpoison(&success, sizeof(sucess));
^~~~~~
success
../../src/systemd/src/basic/alloc-util.h:169:50: note: expanded from macro 'msan_unpoison'
^
../../src/systemd/src/basic/random-util.c:38:17: note: 'success' declared here
uint8_t success;
^
1 error generated.
[80/545] Compiling C object 'src/basic/a6ba3eb@@basic@sta/process-util.c.o'.
ninja: build stopped: subcommand failed.
Fuzzers build failed
```
Let's be a bit paranoid and hash the 16 bytes we get from getauxval()
before using them. AFter all they might be used by other stuff too (in
particular ASLR), and we probably shouldn't end up leaking that seed
though our crappy pseudo-random numbers.
The old flag name was a bit of a misnomer, as /dev/urandom cannot be
"drained". Once it's initialized it's initialized and then is good
forever. (Only /dev/random has a concept of 'draining', but we never use
that, as it's an obsolete interface).
The flag is still useful though, since it allows us to suppress accesses
to the random pool while it is not initialized, as that trips up the
kernel and it logs about any such attempts, which we really don't want.
This isn't really necessary for the subsequent commit, but I expect that we'll
need to unpoison more often once we turn on msan in CI, so I think think this
change makes sense in the long run.
Rename rdrand64 to rdrand, and switch from uint64_t to unsigned long.
This produces code that will compile/assemble on both x86-64 and x86-32.
This could be useful when running a 32-bit copy of systemd on a modern
Intel processor.
RDRAND is inherently arch-specific, so relying on the compiler-defined
'long' type seems reasonable.
We only use this when we don't require the best randomness. The primary
usecase for this is UUID generation, as this means we don't drain
randomness from the kernel pool for them. Since UUIDs are usually not
secrets RDRAND should be goot enough for them to avoid real-life
collisions.
Originally, the high_quality_required boolean argument controlled two
things: whether to extend any random data we successfully read with
pseudo-random data, and whether to return -ENODATA if we couldn't read
any data at all.
The boolean got replaced by RANDOM_EXTEND_WITH_PSEUDO, but this name
doesn't really cover the second part nicely. Moreover hiding both
changes of behaviour under a single flag is confusing. Hence, let's
split this part off under a new flag, and use it from random_bytes().
This should normally not happen, but given that the man page suggests
something about this in the context of interruption, let's handle this
and propagate an I/O error.
It's more descriptive, since we also have a function random_bytes()
which sounds very similar.
Also rename pseudorandom_bytes() to pseudo_random_bytes(). This way the
two functions are nicely systematic, one returning genuine random bytes
and the other pseudo random ones.
It's cheap to get RDRAND and given that srand() is anyway not really
useful for trusted randomness let's use RDRAND for it, after all we have
all the hard work for that already in place.
Pretty much all intel cpus have had RDRAND in a long time. While
CPU-internal RNG are widely not trusted, for seeding hash tables it's
perfectly OK to use: we don't high quality entropy in that case, hence
let's use it.
This is only hooked up with 'high_quality_required' is false. If we
require high quality entropy the kernel is the only source we should
use.
These lines are generally out-of-date, incomplete and unnecessary. With
SPDX and git repository much more accurate and fine grained information
about licensing and authorship is available, hence let's drop the
per-file copyright notice. Of course, removing copyright lines of others
is problematic, hence this commit only removes my own lines and leaves
all others untouched. It might be nicer if sooner or later those could
go away too, making git the only and accurate source of authorship
information.
This part of the copyright blurb stems from the GPL use recommendations:
https://www.gnu.org/licenses/gpl-howto.en.html
The concept appears to originate in times where version control was per
file, instead of per tree, and was a way to glue the files together.
Ultimately, we nowadays don't live in that world anymore, and this
information is entirely useless anyway, as people are very welcome to
copy these files into any projects they like, and they shouldn't have to
change bits that are part of our copyright header for that.
hence, let's just get rid of this old cruft, and shorten our codebase a
bit.
`fuzz-journal-remote` seems to be failing under `msan` as soon as it starts:
$ sudo infra/helper.py run_fuzzer systemd fuzz-journal-remote
Running: docker run --rm -i --privileged -e FUZZING_ENGINE=libfuzzer -v /home/vagrant/oss-fuzz/build/out/systemd:/out -t gcr.io/oss-fuzz-base/base-runner run_fuzzer fuzz-journal-remote
Using seed corpus: fuzz-journal-remote_seed_corpus.zip
/out/fuzz-journal-remote -rss_limit_mb=2048 -timeout=25 /tmp/fuzz-journal-remote_corpus -max_len=65536 < /dev/null
INFO: Seed: 3380449479
INFO: Loaded 2 modules (36336 inline 8-bit counters): 36139 [0x7ff36ea31d39, 0x7ff36ea3aa64), 197 [0x9998c8, 0x99998d),
INFO: Loaded 2 PC tables (36336 PCs): 36139 [0x7ff36ea3aa68,0x7ff36eac7d18), 197 [0x999990,0x99a5e0),
INFO: 2 files found in /tmp/fuzz-journal-remote_corpus
INFO: seed corpus: files: 2 min: 4657b max: 7790b total: 12447b rss: 97Mb
Uninitialized bytes in __interceptor_pwrite64 at offset 24 inside [0x7fffdd4d7230, 240)
==15==WARNING: MemorySanitizer: use-of-uninitialized-value
#0 0x7ff36e685e8a in journal_file_init_header /work/build/../../src/systemd/src/journal/journal-file.c:436:13
#1 0x7ff36e683a9d in journal_file_open /work/build/../../src/systemd/src/journal/journal-file.c:3333:21
#2 0x7ff36e68b8f6 in journal_file_open_reliably /work/build/../../src/systemd/src/journal/journal-file.c:3520:13
#3 0x4a3f35 in open_output /work/build/../../src/systemd/src/journal-remote/journal-remote.c:70:13
#4 0x4a34d0 in journal_remote_get_writer /work/build/../../src/systemd/src/journal-remote/journal-remote.c:136:21
#5 0x4a550f in get_source_for_fd /work/build/../../src/systemd/src/journal-remote/journal-remote.c:183:13
#6 0x4a46bd in journal_remote_add_source /work/build/../../src/systemd/src/journal-remote/journal-remote.c:235:13
#7 0x4a271c in LLVMFuzzerTestOneInput /work/build/../../src/systemd/src/fuzz/fuzz-journal-remote.c:36:9
#8 0x4f27cc in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) /src/libfuzzer/FuzzerLoop.cpp:524:13
#9 0x4efa0b in fuzzer::Fuzzer::RunOne(unsigned char const*, unsigned long, bool, fuzzer::InputInfo*, bool*) /src/libfuzzer/FuzzerLoop.cpp:448:3
#10 0x4f8e96 in fuzzer::Fuzzer::ReadAndExecuteSeedCorpora(std::__1::vector<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, fuzzer::fuzzer_allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > > const&) /src/libfuzzer/FuzzerLoop.cpp:732:7
#11 0x4f9f73 in fuzzer::Fuzzer::Loop(std::__1::vector<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, fuzzer::fuzzer_allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > > const&) /src/libfuzzer/FuzzerLoop.cpp:752:3
#12 0x4bf329 in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) /src/libfuzzer/FuzzerDriver.cpp:756:6
#13 0x4ac391 in main /src/libfuzzer/FuzzerMain.cpp:20:10
#14 0x7ff36d14982f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)
#15 0x41f9d8 in _start (/out/fuzz-journal-remote+0x41f9d8)
Uninitialized value was stored to memory at
#0 0x7ff36e61cd41 in sd_id128_randomize /work/build/../../src/systemd/src/libsystemd/sd-id128/sd-id128.c:288:16
#1 0x7ff36e685cec in journal_file_init_header /work/build/../../src/systemd/src/journal/journal-file.c:426:13
#2 0x7ff36e683a9d in journal_file_open /work/build/../../src/systemd/src/journal/journal-file.c:3333:21
#3 0x7ff36e68b8f6 in journal_file_open_reliably /work/build/../../src/systemd/src/journal/journal-file.c:3520:13
#4 0x4a3f35 in open_output /work/build/../../src/systemd/src/journal-remote/journal-remote.c:70:13
#5 0x4a34d0 in journal_remote_get_writer /work/build/../../src/systemd/src/journal-remote/journal-remote.c:136:21
#6 0x4a550f in get_source_for_fd /work/build/../../src/systemd/src/journal-remote/journal-remote.c:183:13
#7 0x4a46bd in journal_remote_add_source /work/build/../../src/systemd/src/journal-remote/journal-remote.c:235:13
#8 0x4a271c in LLVMFuzzerTestOneInput /work/build/../../src/systemd/src/fuzz/fuzz-journal-remote.c:36:9
#9 0x4f27cc in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) /src/libfuzzer/FuzzerLoop.cpp:524:13
#10 0x4efa0b in fuzzer::Fuzzer::RunOne(unsigned char const*, unsigned long, bool, fuzzer::InputInfo*, bool*) /src/libfuzzer/FuzzerLoop.cpp:448:3
#11 0x4f8e96 in fuzzer::Fuzzer::ReadAndExecuteSeedCorpora(std::__1::vector<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, fuzzer::fuzzer_allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > > const&) /src/libfuzzer/FuzzerLoop.cpp:732:7
#12 0x4f9f73 in fuzzer::Fuzzer::Loop(std::__1::vector<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, fuzzer::fuzzer_allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > > const&) /src/libfuzzer/FuzzerLoop.cpp:752:3
#13 0x4bf329 in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) /src/libfuzzer/FuzzerDriver.cpp:756:6
#14 0x4ac391 in main /src/libfuzzer/FuzzerMain.cpp:20:10
#15 0x7ff36d14982f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)
Uninitialized value was created by an allocation of 't' in the stack frame of function 'sd_id128_randomize'
#0 0x7ff36e61cb00 in sd_id128_randomize /work/build/../../src/systemd/src/libsystemd/sd-id128/sd-id128.c:274
SUMMARY: MemorySanitizer: use-of-uninitialized-value /work/build/../../src/systemd/src/journal/journal-file.c:436:13 in journal_file_init_header
Exiting
MS: 0 ; base unit: 0000000000000000000000000000000000000000
artifact_prefix='./'; Test unit written to ./crash-847911777b3096783f4ee70a69ab6d28380c810b
[vagrant@localhost oss-fuzz]$ sudo infra/helper.py check_build --sanitizer=memory systemd
Running: docker run --rm -i --privileged -e FUZZING_ENGINE=libfuzzer -e SANITIZER=memory -v /home/vagrant/oss-fuzz/build/out/systemd:/out -t gcr.io/oss-fuzz-base/base-runner test_all
INFO: performing bad build checks for /out/fuzz-dhcp-server.
INFO: performing bad build checks for /out/fuzz-journal-remote.
INFO: performing bad build checks for /out/fuzz-unit-file.
INFO: performing bad build checks for /out/fuzz-dns-packet.
4 fuzzers total, 0 seem to be broken (0%).
Check build passed.
It's a false positive which is most likely caused by
https://github.com/google/sanitizers/issues/852. I think it could be got around
by avoiding `getrandom` when the code is compiled with `msan`
Previously we were a bit sloppy with the index and size types of arrays,
we'd regularly use unsigned. While I don't think this ever resulted in
real issues I think we should be more careful there and follow a
stricter regime: unless there's a strong reason not to use size_t for
array sizes and indexes, size_t it should be. Any allocations we do
ultimately will use size_t anyway, and converting forth and back between
unsigned and size_t will always be a source of problems.
Note that on 32bit machines "unsigned" and "size_t" are equivalent, and
on 64bit machines our arrays shouldn't grow that large anyway, and if
they do we have a problem, however that kind of overly large allocation
we have protections for usually, but for overflows we do not have that
so much, hence let's add it.
So yeah, it's a story of the current code being already "good enough",
but I think some extra type hygiene is better.
This patch tries to be comprehensive, but it probably isn't and I missed
a few cases. But I guess we can cover that later as we notice it. Among
smaller fixes, this changes:
1. strv_length()' return type becomes size_t
2. the unit file changes array size becomes size_t
3. DNS answer and query array sizes become size_t
Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=76745
Double newlines (i.e. one empty lines) are great to structure code. But
let's avoid triple newlines (i.e. two empty lines), quadruple newlines,
quintuple newlines, …, that's just spurious whitespace.
It's an easy way to drop 121 lines of code, and keeps the coding style
of our sources a bit tigther.
Files which are installed as-is (any .service and other unit files, .conf
files, .policy files, etc), are left as is. My assumption is that SPDX
identifiers are not yet that well known, so it's better to retain the
extended header to avoid any doubt.
I also kept any copyright lines. We can probably remove them, but it'd nice to
obtain explicit acks from all involved authors before doing that.
log.h really should only include the bare minimum of other headers, as
it is really pulled into pretty much everything else and already in
itself one of the most basic pieces of code we have.
Let's hence drop inclusion of:
1. sd-id128.h because it's entirely unneeded in current log.h
2. errno.h, dito.
3. sys/signalfd.h which we can replace by a simple struct forward
declaration
4. process-util.h which was needed for getpid_cached() which we now hide
in a funciton log_emergency_level() instead, which nicely abstracts
the details away.
5. sys/socket.h which was needed for struct iovec, but a simple struct
forward declaration suffices for that too.
Ultimately this actually makes our source tree larger (since users of
the functionality above must now include it themselves, log.h won't do
that for them), but I think it helps to untangle our web of includes a
tiny bit.
(Background: I'd like to isolate the generic bits of src/basic/ enough
so that we can do a git submodule import into casync for it)
The advantage is that is the name is mispellt, cpp will warn us.
$ git grep -Ee "conf.set\('(HAVE|ENABLE)_" -l|xargs sed -r -i "s/conf.set\('(HAVE|ENABLE)_/conf.set10('\1_/"
$ git grep -Ee '#ifn?def (HAVE|ENABLE)' -l|xargs sed -r -i 's/#ifdef (HAVE|ENABLE)/#if \1/; s/#ifndef (HAVE|ENABLE)/#if ! \1/;'
$ git grep -Ee 'if.*defined\(HAVE' -l|xargs sed -i -r 's/defined\((HAVE_[A-Z0-9_]*)\)/\1/g'
$ git grep -Ee 'if.*defined\(ENABLE' -l|xargs sed -i -r 's/defined\((ENABLE_[A-Z0-9_]*)\)/\1/g'
+ manual changes to meson.build
squash! build-sys: use #if Y instead of #ifdef Y everywhere
v2:
- fix incorrect setting of HAVE_LIBIDN2
When we compare two size values, let's make sure we cast from the
smaller to the bigger type first, if both types differ, rather than the
reverse in order to not run into overflows.
During early boot, we'd call getrandom(), and immediately fall back to
reading from /dev/urandom unless we got the full requested number of bytes.
Those two sources are the same, so the most likely result is /dev/urandom
producing some pseudorandom numbers for us, complaining widely on the way.
Let's change our behaviour to be more conservative:
- if the numbers are only used to initialize a hash table, a short read is OK,
we don't really care if we get the first part of the seed truly random and
then some pseudorandom bytes. So just do that and return "success".
- if getrandom() returns -EAGAIN, fall back to rand() instead of querying
/dev/urandom again.
The idea with those two changes is to avoid generating a warning about
reading from an /dev/urandom when the kernel doesn't have enough entropy.
- only in the cases where we really need to make the best effort possible
(sd_id128_randomize and firstboot password hashing), fall back to
/dev/urandom.
When calling getrandom(), drop the checks whether the argument fits in an int —
getrandom() should do that for us already, and we call it with small arguments
only anyway.
Note that this does not really change the (relatively high) number of random
bytes we request from the kernel. On my laptop, during boot, PID 1 and all
other processes using this code through libsystemd request:
74780 bytes with high_quality_required == false
464 bytes with high_quality_required == true
and it does not eliminate reads from /dev/urandom completely. If the kernel was
short on entropy and getrandom() would fail, we would fall back to /dev/urandom
for those 464 bytes.
When falling back to /dev/urandom, don't lose the short read we already got,
and just read the remaining bytes.
If getrandom() syscall is not available, we fall back to /dev/urandom same
as before.
Fixes#4167 (possibly partially, let's see).
The only implementation that we care about — glibc — provides us
with 31 bits of entropy. Let's use 24 bits of that, instead of throwing
all but 8 away.
There's some confusion: older man pages specify that linux/random.h
contains getrandom, but newer glibc has it in sys/random.h. Detect if
the newer header is available and include it. We still need the older
header for the flags.
Lennart Poettering