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Adhemerval Zanella Netto 6f4e0fcfa2 stdlib: Add arc4random, arc4random_buf, and arc4random_uniform (BZ #4417) 
The implementation is based on scalar Chacha20 with per-thread cache.
It uses getrandom or /dev/urandom as fallback to get the initial entropy,
and reseeds the internal state on every 16MB of consumed buffer.

To improve performance and lower memory consumption the per-thread cache
is allocated lazily on first arc4random functions call, and if the
memory allocation fails getentropy or /dev/urandom is used as fallback.
The cache is also cleared on thread exit iff it was initialized (so if
arc4random is not called it is not touched).

Although it is lock-free, arc4random is still not async-signal-safe
(the per thread state is not updated atomically).

The ChaCha20 implementation is based on RFC8439 [1], omitting the final
XOR of the keystream with the plaintext because the plaintext is a
stream of zeros.  This strategy is similar to what OpenBSD arc4random
does.

The arc4random_uniform is based on previous work by Florian Weimer,
where the algorithm is based on Jérémie Lumbroso paper Optimal Discrete
Uniform Generation from Coin Flips, and Applications (2013) [2], who
credits Donald E. Knuth and Andrew C. Yao, The complexity of nonuniform
random number generation (1976), for solving the general case.

The main advantage of this method is the that the unit of randomness is not
the uniform random variable (uint32_t), but a random bit.  It optimizes the
internal buffer sampling by initially consuming a 32-bit random variable
and then sampling byte per byte.  Depending of the upper bound requested,
it might lead to better CPU utilization.

Checked on x86_64-linux-gnu, aarch64-linux, and powerpc64le-linux-gnu.

Co-authored-by: Florian Weimer <fweimer@redhat.com>
Reviewed-by: Yann Droneaud <ydroneaud@opteya.com>

[1] https://datatracker.ietf.org/doc/html/rfc8439
[2] https://arxiv.org/pdf/1304.1916.pdf
2022-07-22 11:58:27 -03:00
..
alpha
alphaev6/fpu
alphaev67/fpu
bits Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
fpu
sys Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
____longjmp_chk.S Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
a.out.h Break lines before not after operators, batch 4. 2019-03-07 20:20:25 +00:00
adjtime.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
adjtimex.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
aio_cancel.c Linux: Move aio_cancel, aio_cancel64 into libc 2021-06-25 11:48:46 +02:00
arch-syscall.h Update syscall lists for Linux 5.17 2022-03-23 17:11:56 +00:00
brk_call.h Linux: Introduce __brk_call for invoking the brk system call 2022-05-16 18:41:52 +02:00
c++-types.data
clone.S Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
configure
configure.ac
dl-auxv.h Linux: Consolidate auxiliary vector parsing (redo) 2022-02-28 11:50:41 +01:00
dl-support.c
dl-sysdep.c
errlist-compat-data.h stdio: Remove the usage of $(fno-unit-at-a-time) for errlist.c 2022-05-13 10:54:41 -03:00
fraiseexcpt.S Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
fstatfs64.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
fstatfs.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
fxstat64.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
fxstatat64.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
getclktck.c
getcontext.S Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
getdents64.c Consolidate Linux getdents{64} implementation 2018-04-19 08:49:52 -03:00
getdents.c Consolidate Linux getdents{64} implementation 2018-04-19 08:49:52 -03:00
getegid.S Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
geteuid.S Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
gethostname.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
getppid.S Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
getrlimit64.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
gettimeofday.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
glob-lstat-compat.c posix: Add compat glob symbol to not follow dangling symbols 2017-09-25 18:04:16 -07:00
globfree.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
ieee_get_fp_control.S Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
ieee_set_fp_control.S Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
Implies
ioperm.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
ipc_priv.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
kernel_sigaction.h alpha: Use Linux generic sigaction implementation 2018-12-18 19:52:21 -02:00
kernel_stat.h alpha: Remove anonymous union in struct stat [BZ #27042] 2020-12-21 09:09:43 -03:00
kernel_sysinfo.h
kernel_termios.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
kernel-features.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
ld.abilist Linux: Use ptrdiff_t for __rseq_offset 2022-02-02 22:37:20 +01:00
libanl.abilist resolv: Move libanl into libc (if libpthread is in libc) 2021-07-02 11:45:00 +02:00
libBrokenLocale.abilist Ignore absolute symbols in ABI tests. 2018-05-04 15:46:32 +00:00
libc_malloc_debug.abilist Move malloc_{g,s}et_state to libc_malloc_debug 2021-07-22 18:38:10 +05:30
libc.abilist stdlib: Add arc4random, arc4random_buf, and arc4random_uniform (BZ #4417) 2022-07-22 11:58:27 -03:00
libcrypt.abilist Ignore absolute symbols in ABI tests. 2018-05-04 15:46:32 +00:00
libdl.abilist dlfcn: Move dlopen into libc 2021-06-03 08:26:04 +02:00
libm.abilist math: Remove the error handling wrapper from hypot and hypotf 2021-12-13 10:08:46 -03:00
libnsl.abilist Ignore absolute symbols in ABI tests. 2018-05-04 15:46:32 +00:00
libpthread.abilist nptl: Remove remaining code from libpthread 2021-05-21 22:35:01 +02:00
libresolv.abilist resolv: Move res_query functions into libc 2021-07-19 07:56:57 +02:00
librt-compat.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
librt.abilist Linux: Move timer_settime, __timer_settime64 from librt to libc 2021-06-28 09:51:01 +02:00
libthread_db.abilist Ignore absolute symbols in ABI tests. 2018-05-04 15:46:32 +00:00
libutil.abilist login: Move libutil into libc 2021-06-30 08:43:37 +02:00
localplt.data mtrace: Wean away from malloc hooks 2021-07-22 18:38:06 +05:30
lxstat64.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
makecontext.S Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
Makefile nptl: Remove remaining code from libpthread 2021-05-21 22:35:01 +02:00
nldbl-abi.h
oldglob.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
osf_adjtime.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
osf_getitimer.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
osf_getrusage.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
osf_gettimeofday.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
osf_setitimer.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
osf_settimeofday.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
osf_utimes.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
osf_wait4.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
rt_sigaction.S Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
select.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
setcontext.S Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
setfpucw.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
setrlimit64.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
settimeofday.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
shlib-versions
sigcontextinfo.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
sizes.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
statfs64.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
statfs.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
swapcontext.S Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
syscall.S Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
syscalls.list linux: Consolidate Linux setsockopt implementation 2021-07-06 11:45:35 -03:00
sysconf.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
sysdep.h Replace __libc_multiple_threads with __libc_single_threaded 2022-07-05 10:14:47 -03:00
timer_t_was_int_compat.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
ucontext-offsets.sym
Versions Linux: Move timer_settime, __timer_settime64 from librt to libc 2021-06-28 09:51:01 +02:00
vfork.S Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
wait4.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
wordexp.c
xstat64.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
xstatconv.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
xstatconv.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
xstatver.h Remove mknod wrapper functions, move them to symbols 2020-10-09 17:02:06 -03:00