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glibc/stdlib/Makefile
Jason A. Donenfeld eaad4f9e8f arc4random: simplify design for better safety 
Rather than buffering 16 MiB of entropy in userspace (by way of
chacha20), simply call getrandom() every time.

This approach is doubtlessly slower, for now, but trying to prematurely
optimize arc4random appears to be leading toward all sorts of nasty
properties and gotchas. Instead, this patch takes a much more
conservative approach. The interface is added as a basic loop wrapper
around getrandom(), and then later, the kernel and libc together can
work together on optimizing that.

This prevents numerous issues in which userspace is unaware of when it
really must throw away its buffer, since we avoid buffering all
together. Future improvements may include userspace learning more from
the kernel about when to do that, which might make these sorts of
chacha20-based optimizations more possible. The current heuristic of 16
MiB is meaningless garbage that doesn't correspond to anything the
kernel might know about. So for now, let's just do something
conservative that we know is correct and won't lead to cryptographic
issues for users of this function.

This patch might be considered along the lines of, "optimization is the
root of all evil," in that the much more complex implementation it
replaces moves too fast without considering security implications,
whereas the incremental approach done here is a much safer way of going
about things. Once this lands, we can take our time in optimizing this
properly using new interplay between the kernel and userspace.

getrandom(0) is used, since that's the one that ensures the bytes
returned are cryptographically secure. But on systems without it, we
fallback to using /dev/urandom. This is unfortunate because it means
opening a file descriptor, but there's not much of a choice. Secondly,
as part of the fallback, in order to get more or less the same
properties of getrandom(0), we poll on /dev/random, and if the poll
succeeds at least once, then we assume the RNG is initialized. This is a
rough approximation, as the ancient "non-blocking pool" initialized
after the "blocking pool", not before, and it may not port back to all
ancient kernels, though it does to all kernels supported by glibc
(≥3.2), so generally it's the best approximation we can do.

The motivation for including arc4random, in the first place, is to have
source-level compatibility with existing code. That means this patch
doesn't attempt to litigate the interface itself. It does, however,
choose a conservative approach for implementing it.

Cc: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: Cristian Rodríguez <crrodriguez@opensuse.org>
Cc: Paul Eggert <eggert@cs.ucla.edu>
Cc: Mark Harris <mark.hsj@gmail.com>
Cc: Eric Biggers <ebiggers@kernel.org>
Cc: linux-crypto@vger.kernel.org
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
2022-07-27 08:58:27 -03:00

475 lines
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Makefile
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# Copyright (C) 1991-2022 Free Software Foundation, Inc.
# This file is part of the GNU C Library.
# The GNU C Library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
# The GNU C Library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Lesser General Public License for more details.
# You should have received a copy of the GNU Lesser General Public
# License along with the GNU C Library; if not, see
# <https://www.gnu.org/licenses/>.
#
# Makefile for stdlib routines
#
subdir := stdlib
include ../Makeconfig
headers := \
alloca.h \
bits/errno.h \
bits/indirect-return.h \
bits/monetary-ldbl.h \
bits/stdint-intn.h \
bits/stdint-uintn.h \
bits/stdlib-bsearch.h \
bits/stdlib-float.h \
bits/stdlib.h \
bits/stdlib-ldbl.h \
bits/time64.h \
bits/timesize.h \
bits/types/error_t.h \
bits/wordsize.h \
errno.h \
fmtmsg.h \
inttypes.h \
monetary.h \
stdint.h \
stdlib.h \
sys/errno.h \
sys/random.h \
sys/ucontext.h \
ucontext.h \
# headers
routines := \
a64l \
abort \
abs \
arc4random \
arc4random_uniform \
at_quick_exit \
atof \
atoi \
atol\
atoll \
bsearch \
canonicalize \
cxa_at_quick_exit \
cxa_atexit \
cxa_finalize \
cxa_thread_atexit_impl \
div \
drand48 \
drand48-iter \
drand48_r \
erand48 \
erand48_r \
exit \
fmtmsg \
getcontext \
getentropy \
getenv \
getrandom \
getsubopt \
jrand48 \
jrand48_r \
l64a \
labs \
lcong48 \
lcong48_r \
ldiv \
llabs \
lldiv \
lrand48 \
lrand48_r \
makecontext \
mblen \
mbstowcs \
mbtowc \
mrand48 \
mrand48_r \
msort \
nrand48 \
nrand48_r \
old_atexit \
on_exit atexit \
putenv \
qsort \
quick_exit \
rand \
rand_r \
random \
random_r \
rpmatch \
secure-getenv \
seed48 \
seed48_r \
setcontext \
setenv \
srand48 \
srand48_r \
strfmon \
strfmon_l \
strfromd \
strfromf \
strfroml \
strtod \
strtod_l \
strtod_nan \
strtof \
strtof_l \
strtof_nan \
strtol \
strtol_l \
strtold \
strtold_l \
strtold_nan \
strtoll \
strtoll_l \
strtoul \
strtoul_l \
strtoull \
strtoull_l \
swapcontext \
system \
wcstombs \
wctomb \
xpg_basename \
# routines
aux = \
grouping \
groupingwc \
tens_in_limb \
# aux
# These routines will be omitted from the libc shared object.
# Instead the static object files will be included in a special archive
# linked against when the shared library will be used.
static-only-routines = \
atexit \
at_quick_exit \
# static-only-routines
test-srcs := \
tst-fmtmsg \
#test-srcs
tests := \
bug-fmtmsg1 \
bug-getcontext \
bug-strtod \
bug-strtod2 \
test-a64l \
test-at_quick_exit-race \
test-atexit-race \
test-bz22786 \
test-canon \
test-canon2 \
test-cxa_atexit-race \
test-cxa_atexit-race2 \
test-dlclose-exit-race \
test-on_exit-race \
testdiv \
testmb \
testmb2 \
testrand \
testsort \
tst-arc4random-fork \
tst-arc4random-stats \
tst-arc4random-thread \
tst-at_quick_exit \
tst-atexit \
tst-atof1 \
tst-atof2 \
tst-bsearch \
tst-bz20544 \
tst-canon-bz26341 \
tst-cxa_atexit \
tst-environ \
tst-getrandom \
tst-limits \
tst-makecontext \
tst-makecontext-align \
tst-makecontext2 \
tst-makecontext3 \
tst-on_exit \
tst-qsort \
tst-qsort2 \
tst-quick_exit \
tst-rand48 \
tst-rand48-2 \
tst-random \
tst-random2 \
tst-realpath \
tst-realpath-toolong \
tst-secure-getenv \
tst-setcontext \
tst-setcontext2 \
tst-setcontext3 \
tst-setcontext4 \
tst-setcontext5 \
tst-setcontext6 \
tst-setcontext7 \
tst-setcontext8 \
tst-setcontext9 \
tst-strfmon_l \
tst-strfrom \
tst-strfrom-locale \
tst-strtod \
tst-strtod-nan-locale \
tst-strtod-nan-sign \
tst-strtod-overflow \
tst-strtod-round \
tst-strtod-underflow \
tst-strtod2 \
tst-strtod5 \
tst-strtod6 \
tst-strtol \
tst-strtol-locale \
tst-strtoll \
tst-swapcontext1 \
tst-thread-quick_exit \
tst-tininess \
tst-unsetenv1 \
tst-width \
tst-width-stdint \
tst-xpg-basename \
# tests
tests-internal := \
tst-strtod1i \
tst-strtod3 \
tst-strtod4 \
tst-strtod5i \
tst-tls-atexit \
tst-tls-atexit-nodelete \
# tests-internal
tests-static := \
tst-secure-getenv \
# tests-static
tests-container := \
tst-system \
#tests-container
ifeq ($(build-hardcoded-path-in-tests),yes)
tests += \
tst-empty-env \
# tests
endif
LDLIBS-test-atexit-race = $(shared-thread-library)
LDLIBS-test-at_quick_exit-race = $(shared-thread-library)
LDLIBS-test-cxa_atexit-race = $(shared-thread-library)
LDLIBS-test-cxa_atexit-race2 = $(shared-thread-library)
LDLIBS-test-on_exit-race = $(shared-thread-library)
LDLIBS-tst-canon-bz26341 = $(shared-thread-library)
LDLIBS-tst-arc4random-fork = $(shared-thread-library)
LDLIBS-tst-arc4random-thread = $(shared-thread-library)
LDLIBS-test-dlclose-exit-race = $(shared-thread-library)
LDFLAGS-test-dlclose-exit-race = $(LDFLAGS-rdynamic)
LDLIBS-test-dlclose-exit-race-helper.so = $(libsupport) $(shared-thread-library)
ifeq ($(have-cxx-thread_local),yes)
CFLAGS-tst-quick_exit.o = -std=c++11
LDLIBS-tst-quick_exit = -lstdc++
CFLAGS-tst-thread-quick_exit.o = -std=c++11
LDLIBS-tst-thread-quick_exit = -lstdc++
$(objpfx)tst-thread-quick_exit: $(shared-thread-library)
else
tests-unsupported += \
tst-quick_exit \
tst-thread-quick_exit \
# tests-unsupported
endif
modules-names = \
test-dlclose-exit-race-helper \
tst-tls-atexit-lib \
# modules-names
extra-test-objs += $(addsuffix .os, $(modules-names))
ifeq ($(build-shared),yes)
tests += \
tst-putenv \
# tests
endif
# Several mpn functions from GNU MP are used by the strtod function.
mpn-routines := \
add_n \
addmul_1 \
cmp \
divmod_1 \
divrem \
inlines \
lshift \
mod_1 \
mul \
mul_1 \
mul_n \
rshift \
sub_n \
submul_1 \
udiv_qrnnd \
# mpn-routines
mpn-headers = \
asm-syntax.h \
gmp-impl.h \
gmp-mparam.h \
gmp.h \
longlong.h \
# mpn-headers
routines := \
$(strip $(routines) $(mpn-routines)) \
dbl2mpn \
ldbl2mpn \
mpn2dbl \
mpn2flt \
mpn2ldbl \
# routines
aux += \
fpioconst \
mp_clz_tab \
# aux
tests-extras += \
tst-putenvmod \
# tests-extras
extra-test-objs += \
tst-putenvmod.os \
# extra-test-objs
generated += \
isomac \
isomac.out \
tst-putenvmod.so \
# generated
CFLAGS-bsearch.c += $(uses-callbacks)
CFLAGS-msort.c += $(uses-callbacks)
CFLAGS-qsort.c += $(uses-callbacks)
CFLAGS-system.c += -fexceptions
CFLAGS-system.os = -fomit-frame-pointer
CFLAGS-fmtmsg.c += -fexceptions
CFLAGS-strfmon.c += $(libio-mtsafe)
CFLAGS-strfmon_l.c += $(libio-mtsafe)
# The strfrom class of functions call __printf_fp in order to convert the
# floating-point value to characters. This requires the value of IO_MTSAFE_IO.
CFLAGS-strfromd.c += $(libio-mtsafe)
CFLAGS-strfromf.c += $(libio-mtsafe)
CFLAGS-strfroml.c += $(libio-mtsafe)
CFLAGS-tst-bsearch.c += $(stack-align-test-flags)
CFLAGS-tst-qsort.c += $(stack-align-test-flags)
CFLAGS-tst-makecontext.c += -funwind-tables
CFLAGS-tst-makecontext2.c += $(stack-align-test-flags)
CFLAGS-testmb.c += -D_FORTIFY_SOURCE=2 -Wall -Werror
# Run a test on the header files we use.
tests-special += $(objpfx)isomac.out
ifeq ($(run-built-tests),yes)
tests-special += $(objpfx)tst-fmtmsg.out
endif
include ../Rules
ifeq ($(run-built-tests),yes)
LOCALES := \
cs_CZ.UTF-8 \
de_DE.UTF-8 \
el_GR.UTF-8 \
en_US.ISO-8859-1 \
hi_IN.UTF-8 \
hr_HR.UTF-8 \
tg_TJ.UTF-8 \
tr_TR.ISO-8859-9 \
tr_TR.UTF-8 \
# LOCALES
include ../gen-locales.mk
$(objpfx)bug-strtod2.out: $(gen-locales)
$(objpfx)testmb2.out: $(gen-locales)
$(objpfx)tst-strtod.out: $(gen-locales)
$(objpfx)tst-strtod1i.out: $(gen-locales)
$(objpfx)tst-strtod3.out: $(gen-locales)
$(objpfx)tst-strtod4.out: $(gen-locales)
$(objpfx)tst-strtod5.out: $(gen-locales)
$(objpfx)tst-strtod5i.out: $(gen-locales)
$(objpfx)tst-strtol-locale.out: $(gen-locales)
$(objpfx)tst-strtod-nan-locale.out: $(gen-locales)
$(objpfx)tst-strfmon_l.out: $(gen-locales)
$(objpfx)tst-strfrom.out: $(gen-locales)
$(objpfx)tst-strfrom-locale.out: $(gen-locales)
$(objpfx)test-dlclose-exit-race.out: $(objpfx)test-dlclose-exit-race-helper.so
endif
# Testdir has to be named stdlib and needs to be writable
test-canon-ARGS = --test-dir=${common-objpfx}stdlib
bug-fmtmsg1-ENV = SEV_LEVEL=foo,11,newsev
$(objpfx)isomac.out: $(objpfx)isomac
$(dir $<)$(notdir $<) '$(CC)' \
'-I../include $(+sysdep-includes) $(sysincludes) -I..' > $@; \
$(evaluate-test)
isomac-CFLAGS = -O
$(objpfx)isomac: isomac.c
$(native-compile)
$(objpfx)tst-fmtmsg.out: tst-fmtmsg.sh $(objpfx)tst-fmtmsg
$(SHELL) $< $(common-objpfx) '$(test-program-prefix-before-env)' \
'$(run-program-env)' '$(test-program-prefix-after-env)' \
$(common-objpfx)stdlib/; \
$(evaluate-test)
$(objpfx)tst-putenv: $(objpfx)tst-putenvmod.so
LDFLAGS-tst-putenv = -Wl,--no-as-needed
$(objpfx)tst-putenvmod.so: $(objpfx)tst-putenvmod.os $(link-libc-deps)
$(build-module)
libof-tst-putenvmod = extramodules
$(objpfx)bug-getcontext: $(libm)
$(objpfx)bug-strtod2: $(libm)
$(objpfx)tst-strtod-round: $(libm)
$(objpfx)tst-tininess: $(libm)
$(objpfx)tst-strtod-underflow: $(libm)
$(objpfx)tst-strtod6: $(libm)
$(objpfx)tst-strtod-nan-locale: $(libm)
$(objpfx)tst-strtod-nan-sign: $(libm)
tst-tls-atexit-lib.so-no-z-defs = yes
test-dlclose-exit-race-helper.so-no-z-defs = yes
$(objpfx)tst-tls-atexit: $(shared-thread-library)
$(objpfx)tst-tls-atexit.out: $(objpfx)tst-tls-atexit-lib.so
$(objpfx)tst-tls-atexit-nodelete: $(shared-thread-library)
$(objpfx)tst-tls-atexit-nodelete.out: $(objpfx)tst-tls-atexit-lib.so
$(objpfx)tst-setcontext3.out: tst-setcontext3.sh $(objpfx)tst-setcontext3
$(SHELL) $< $(common-objpfx) '$(test-program-prefix-before-env)' \
'$(run-program-env)' '$(test-program-prefix-after-env)' \
$(common-objpfx)stdlib/; \
$(evaluate-test)
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