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Sync getentropy() checks with use-builtin-arc4random checks

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Without this, we actually fail to build a library that includes the
bultin getentropy when compiling for 10.11 on 10.12.
This commit is contained in:
Simone Basso 2016-12-10 20:58:04 +01:00 committed by Brent Cook
parent c4ee1a6fca
commit 730f199c9c
2 changed files with 48 additions and 30 deletions
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43
m4/check-libc.m4
View File

@ -54,52 +54,37 @@ AC_CACHE_CHECK([for getentropy], ac_cv_func_getentropy, [
#include <sys/types.h>
#include <unistd.h>
/*
* Explanation:
*
* - iOS <= 10.1 fails because of missing sys/random.h
*
* - in macOS 10.12 getentropy is not tagged as introduced in
* 10.12 so we cannot use it for target < 10.12
*/
#ifdef __APPLE__
# include <AvailabilityMacros.h>
# include <TargetConditionals.h>
# if (TARGET_OS_IPHONE || TARGET_OS_SIMULATOR)
/*
* As of iOS 10.1, getentropy() as a system call is defined but is not
* declared in sys/random.h and submitting an App that links to getentropy()
* leads to the App store rejecting the App because:
*
* > The app references non-public symbols in $appname: _getentropy
*
* Disabling the check for getentropy() and thus enabling libressl own
* emulation of that fixes the issue.
*/
# error "As far as we know, getentropy() is not usable on iOS"
# include <sys/random.h> /* Not available as of iOS <= 10.1 */
# else
/*
* Before macOS 10.12 getentropy() was not available. In 10.12 however it
* seems to be not marked for retro-compatibility and thus we cannot cross
* compile targeting, e.g., 10.12 unless we disable getentropy().
*
* To test,
*
* export CFLAGS="-mmacosx-version-min=10.11"
* ./configure
* # ensure that getentropy() is not found
*
* Based on: https://gitweb.torproject.org/tor.git/commit/?id=https://gitweb.torproject.org/tor.git/commit/?id=16fcbd21c963a9a65bf55024680c8323c8b7175d
*/
# include <sys/random.h> /* Pre 10.12 systems should die here */
/* Based on: https://gitweb.torproject.org/tor.git/commit/?id=16fcbd21 */
# ifndef MAC_OS_X_VERSION_10_12
# define MAC_OS_X_VERSION_10_12 101200
# define MAC_OS_X_VERSION_10_12 101200 /* Robustness */
# endif
# if defined(MAC_OS_X_VERSION_MIN_REQUIRED)
# if MAC_OS_X_VERSION_MIN_REQUIRED < MAC_OS_X_VERSION_10_12
# error "Running on Mac OSX 10.11 or earlier"
# error "Targeting on Mac OSX 10.11 or earlier"
# endif
# endif
# endif
#endif /* __APPLE__ */
]], [[
extern int getentropy(void *, size_t);
char buffer;
(void)getentropy(&buffer, sizeof (buffer));
]])],

35
m4/check-os-options.m4
View File

@ -17,10 +17,43 @@ case $host_os in
*darwin*)
HOST_OS=darwin
HOST_ABI=macosx
#
# Don't use arc4random on systems before 10.12 because of
# weak seed on failure to open /dev/random, based on latest
# public source:
# http://www.opensource.apple.com/source/Libc/Libc-997.90.3/gen/FreeBSD/arc4random.c
USE_BUILTIN_ARC4RANDOM=yes
#
# We use the presence of getentropy() to detect 10.12. The
# following check take into account that:
#
# - iOS <= 10.1 fails because of missing getentropy and
# hence they miss sys/random.h
#
# - in macOS 10.12 getentropy is not tagged as introduced in
# 10.12 so we cannot use it for target < 10.12
#
AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
#include <AvailabilityMacros.h>
#include <unistd.h>
#include <sys/random.h> /* Systems without getentropy() should die here */
/* Based on: https://gitweb.torproject.org/tor.git/commit/?id=16fcbd21 */
#ifndef MAC_OS_X_VERSION_10_12
# define MAC_OS_X_VERSION_10_12 101200
#endif
#if defined(MAC_OS_X_VERSION_MIN_REQUIRED)
# if MAC_OS_X_VERSION_MIN_REQUIRED < MAC_OS_X_VERSION_10_12
# error "Running on Mac OSX 10.11 or earlier"
# endif
#endif
]], [[
char buf[1]; getentropy(buf, 1);
]])],
[ USE_BUILTIN_ARC4RANDOM=no ],
[ USE_BUILTIN_ARC4RANDOM=yes ]
)
AC_MSG_CHECKING([whether to use builtin arc4random])
AC_MSG_RESULT([$USE_BUILTIN_ARC4RANDOM])
# Not available on iOS
AC_CHECK_HEADER([arpa/telnet.h], [], [BUILD_NC=no])
;;