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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
..
arpa resolv: Move ns_samename into its own file, and into libc 2021-07-19 07:56:21 +02:00
bits Apply asm redirections in stdio.h before first use [BZ #27087] 2022-07-14 16:01:14 -03:00
gnu Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
net Fix resolver if_* namespace (bug 17717). 2014-12-16 18:18:49 +00:00
netinet nss_files: Consolidate line parse declarations in <nss_files.h> 2020-07-21 07:33:20 +02:00
programs Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
protocols
rpc Handle out-of-memory case in svc_tcp.c/svc_unix.c:rendezvous_request. 2020-12-10 11:11:20 +01:00
rpcsvc Remove --enable-obsolete-nsl configure flag 2020-07-08 17:25:57 +02:00
sys misc: Optimize internal usage of __libc_single_threaded 2022-06-24 17:45:58 -03:00
aio.h Linux: Move aio_suspend, aio_suspend64, __aio_suspend_time64 to libc 2021-06-25 11:55:27 +02:00
aliases.h Remove --enable-obsolete-nsl configure flag 2020-07-08 17:25:57 +02:00
alloc_buffer.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
alloca.h Remove macros extend_alloca, extend_alloca_account [BZ #18023] 2018-06-27 19:20:37 +02:00
allocate_once.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
ar.h Add missing header wrappers under include/ 2019-02-16 08:25:16 +01:00
argp-fmtstream.h Mark internal argp functions with attribute_hidden [BZ #18822] 2017-10-01 15:10:27 -07:00
argp.h ldbl-opt: Add argp_error and argp_failure (bug 23983) 2019-03-01 15:21:32 -03:00
argz.h Use libc_hidden_* for argz_next, __argz_next (bug 15105). 2018-02-15 21:00:02 +00:00
array_length.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
assert.h Introduce NO_RTLD_HIDDEN, make hurd use it instead of NO_HIDDEN 2017-10-03 01:33:38 +02:00
atomic.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
atomic_wide_counter.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
byteswap.h
clone_internal.h Add an internal wrapper for clone, clone2 and clone3 2021-07-14 06:33:58 -07:00
complex.h float128: Add private _Float128 declarations for libm. 2017-05-15 10:23:28 -03:00
cpio.h Add more headers to include/ for conform tests. 2014-12-11 21:41:30 +00:00
crypt.h Add include/crypt.h. 2016-10-28 22:40:16 -04:00
ctype.h Use libc_hidden_* for tolower, toupper (bug 15105). 2018-02-23 13:54:53 +00:00
des.h
dirent.h Use 64 bit time_t stat internally 2021-06-22 12:09:52 -03:00
dlfcn.h elf: Add _dl_find_object function 2021-12-28 22:52:56 +01:00
dso_handle.h Mark __dso_handle as hidden [BZ #18822] 2017-09-26 16:53:44 -07:00
elf.h elf: Refuse to dlopen PIE objects [BZ #24323] 2019-06-18 16:42:10 +02:00
endian.h
envz.h Installed header hygiene (BZ#20366): Test of installed headers. 2016-09-23 08:43:56 -04:00
err.h ldbl-128ibm-compat: PLT redirects for using ldbl redirects internally 2020-03-25 14:34:23 -05:00
errno.h Remove tls.h inclusion from internal errno.h 2020-11-13 12:59:19 -03:00
error.h ldbl-opt: Add error and error_at_line (bug 23984) 2019-03-01 15:26:36 -03:00
execinfo.h Installed header hygiene (BZ#20366): Test of installed headers. 2016-09-23 08:43:56 -04:00
fcntl.h Fix Linux fcntl OFD locks for non-LFS architectures (BZ#20251) 2018-06-26 13:22:53 -03:00
features-time64.h y2038: Add support for 64-bit time on legacy ABIs 2021-06-15 10:42:11 -03:00
features.h Prepare for glibc 2.35 release. 2022-02-03 00:23:26 -05:00
fenv.h Move fenv.h soft-float inlines from fenv_private.h to include/fenv.h. 2018-09-04 19:52:06 +00:00
file_change_detection.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
filename.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
float.h Make totalorder and totalordermag functions take pointer arguments. 2019-08-15 15:18:34 +00:00
fmtmsg.h Add more headers to include/ for conform tests. 2014-12-11 21:41:30 +00:00
fnmatch.h First steps to get conformtest fully working 2012-02-25 23:18:39 -05:00
fpu_control.h Hide internal __setfpucw function [BZ #18822] 2017-10-01 17:52:15 -07:00
fstab.h Add missing header wrappers under include/ 2019-02-16 08:25:16 +01:00
fts.h io: Add fts64 with 64-bit time_t support 2021-06-15 10:42:11 -03:00
ftw.h io: Add ftw64 with 64-bit time_t support 2021-06-15 10:42:11 -03:00
gconv.h
getopt.h getopt: remove USE_NONOPTION_FLAGS 2017-04-07 07:45:53 -04:00
getopt_int.h
glob.h Fix extra PLT reference in libc.so due to __glob64_time64 if build with gcc 7.5 on 32bit. 2021-07-01 16:46:59 +02:00
gmp.h Mark internal gmp functions with attribute_hidden [BZ #18822] 2017-10-01 15:15:30 -07:00
gnu-versions.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
grp-merge.h NSS: Implement group merging support. 2016-04-29 22:18:21 -04:00
grp.h nss_files: Consolidate line parse declarations in <nss_files.h> 2020-07-21 07:33:20 +02:00
gshadow.h nss_files: Consolidate line parse declarations in <nss_files.h> 2020-07-21 07:33:20 +02:00
iconv.h
idx.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
ifaddrs.h hurd: Fix getifaddrs' and freeifaddrs' symbol exposition 2017-09-28 01:05:18 +02:00
ifreq.h Hide internal __ifreq function [BZ #18822] 2017-10-01 17:35:46 -07:00
ifunc-impl-list.h Add bounds check to __libc_ifunc_impl_list 2022-06-10 17:13:29 +01:00
inline-hashtab.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
intprops.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
inttypes.h Make strtoimax, strtoumax, wcstoimax, wcstoumax into aliases 2020-12-08 18:15:27 +00:00
langinfo.h Add first fixes for conformtest for POSIX2008 2012-02-26 21:32:56 -05:00
lastlog.h Add missing header wrappers under include/ 2019-02-16 08:25:16 +01:00
libc-diag.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
libc-internal.h elf: Remove __libc_init_secure 2022-04-19 15:52:27 -07:00
libc-pointer-arith.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
libc-symbols.h libc-symbols.h: remove unused macros 2022-07-04 21:15:51 -07:00
libgen.h
libintl.h Document the internal _ and N_ macros 2020-05-06 17:35:40 +02:00
limits.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
link.h Add GLIBC_ABI_DT_RELR for DT_RELR support 2022-04-26 10:16:11 -07:00
list.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
list_t.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
locale.h First steps to get conformtest fully working 2012-02-25 23:18:39 -05:00
loop_unroll.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
malloc.h Simplify __malloc_initialized 2021-07-22 18:38:04 +05:30
math-narrow-eval.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
math.h Redirect fma calls to __fma in libm 2021-09-15 22:57:35 +00:00
mcheck.h mcheck: Wean away from malloc hooks [BZ #23489] 2021-07-22 18:38:02 +05:30
memory.h
mntent.h Hide internal __hasmntopt function [BZ #18822] 2017-10-01 17:37:42 -07:00
monetary.h Rename __LONG_DOUBLE_USES_FLOAT128 to __LDOUBLE_REDIRECTS_TO_FLOAT128_ABI 2020-04-30 08:52:08 -05:00
mqueue.h Linux: Move mq_send, mq_timedsend, __mq_timedsend_time64 to libc 2021-06-25 12:21:12 +02:00
netdb.h nss_files: Move into libc 2021-07-07 18:33:52 +02:00
netgroup.h
nl_types.h
nss.h nss: Export nscd hash function as __nss_hash [BZ #22459] 2017-11-23 14:08:11 +01:00
nss_dns.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
nss_files.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
nsswitch.h
obstack.h Installed header hygiene (BZ#20366): Test of installed headers. 2016-09-23 08:43:56 -04:00
plural-exp.h Hide internal __gettextparse function [BZ #18822] 2017-10-01 17:31:05 -07:00
poll.h
printf.h stdio-common: Move union printf_arg int <printf.h> 2022-05-24 08:03:11 +02:00
pthread.h Linux: Move mq_notify from librt to libc 2021-06-25 12:20:47 +02:00
pty.h login: Move libutil into libc 2021-06-30 08:43:37 +02:00
pwd.h nss_files: Consolidate line parse declarations in <nss_files.h> 2020-07-21 07:33:20 +02:00
random-bits.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
re_comp.h Add missing header wrappers under include/ 2019-02-16 08:25:16 +01:00
regex.h regex: copy back from Gnulib 2021-09-21 08:00:44 -07:00
regexp.h Add missing header wrappers under include/ 2019-02-16 08:25:16 +01:00
register-atfork.h Fix deadlock when pthread_atfork handler calls pthread_atfork or dlclose 2022-05-25 11:27:31 +02:00
resolv.h resolv: Move res_queriesmatch to its own file and into libc 2021-07-19 07:56:21 +02:00
rounding-mode.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
rtld-malloc.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
sched.h Add hidden prototypes for __sched_getparam, __sched_getscheduler 2020-02-20 08:57:01 +01:00
scratch_buffer.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
search.h misc: Add twalk_r function 2019-05-02 11:42:51 +02:00
set-hooks.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
setjmp.h setjmp: Replace jmp_buf-macros.h with jmp_buf-macros.sym 2021-11-22 13:43:22 -03:00
sgtty.h
shadow.h nss_files: Consolidate line parse declarations in <nss_files.h> 2020-07-21 07:33:20 +02:00
shlib-compat.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
shm-directory.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
signal.h stdio: Remove the usage of $(fno-unit-at-a-time) for siglist.c 2022-05-13 10:54:41 -03:00
spawn.h posix: Use posix_spawn for wordexp 2019-10-09 17:48:41 -03:00
stab.h
stackinfo.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
stap-probe.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
stdc-predef.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
stdint.h Move inttypes.h and stdint.h to stdlib. 2019-03-13 09:42:09 -04:00
stdio.h stdio: Remove the usage of $(fno-unit-at-a-time) for errlist.c 2022-05-13 10:54:41 -03:00
stdio_ext.h Installed header hygiene (BZ#20366): Test of installed headers. 2016-09-23 08:43:56 -04:00
stdlib.h stdlib: Add arc4random, arc4random_buf, and arc4random_uniform (BZ #4417) 2022-07-22 11:58:27 -03:00
string.h String: Add hidden defs for __memcmpeq() to enable internal usage 2021-10-26 16:51:29 -05:00
strings.h
struct___timeb64.h time: Add 64-bit time_t support for ftime 2020-10-27 09:54:50 -03:00
struct___timespec64.h y2038: include: Move struct __timespec64 definition to a separate file 2020-04-06 23:05:11 +02:00
struct___timeval64.h y2038: include: Move struct __timeval64 definition to a separate file 2020-05-05 19:36:25 +02:00
stubs-prologue.h
syscall.h
sysexits.h
syslog.h
tar.h
termios.h Hide internal __tcgetattr function [BZ #18822] 2017-10-01 17:48:24 -07:00
tgmath.h
time.h clock_settime/clock_gettime: Use __nonnull to avoid null pointer 2022-05-05 17:48:04 +05:30
ttyent.h Installed header hygiene (BZ#20366): Test of installed headers. 2016-09-23 08:43:56 -04:00
uchar.h First steps to get conformtest fully working 2012-02-25 23:18:39 -05:00
ucontext.h
ulimit.h First steps to get conformtest fully working 2012-02-25 23:18:39 -05:00
unistd.h elf: Remove __libc_init_secure 2022-04-19 15:52:27 -07:00
utime.h First steps to get conformtest fully working 2012-02-25 23:18:39 -05:00
utmp.h login: Move libutil into libc 2021-06-30 08:43:37 +02:00
values.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
verify.h posix: Sync regex with gnulib 2019-11-06 09:20:52 -03:00
wait.h Add missing header wrappers under include/ 2019-02-16 08:25:16 +01:00
wchar.h wcrtomb: Make behavior POSIX compliant 2022-05-13 19:15:46 +05:30
wctype.h Remove __need macros from stdio.h and wchar.h. 2017-06-08 13:58:17 -04:00
wordexp.h First steps to get conformtest fully working 2012-02-25 23:18:39 -05:00