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Update getentropy() code from OpenBSD

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Includes changes to handle the Linux syscall blocking when there is not
enough entropy during boot, by switching it to non-blocking mode and
falling back to the alternative implementations. Man page URL reference
fixes. Build fixes for Mac OS X.

Fixes: https://bugs.debian.org/898088
This commit is contained in:
Guillem Jover
2018-05-15 00:41:26 +02:00
parent 993828d84e
commit e42381dc51
7 changed files with 36 additions and 22 deletions
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25
src/getentropy_linux.c
View File

@@ -1,4 +1,4 @@
/* $OpenBSD: getentropy_linux.c,v 1.40 2015/08/25 17:26:43 deraadt Exp $ */
/* $OpenBSD: getentropy_linux.c,v 1.45 2018/03/13 22:53:28 bcook Exp $ */
/*
* Copyright (c) 2014 Theo de Raadt <deraadt@openbsd.org>
@@ -17,7 +17,7 @@
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
* Emulation of getentropy(2) as documented at:
* http://www.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man2/getentropy.2
* http://man.openbsd.org/getentropy.2
*/
#define _POSIX_C_SOURCE 199309L
@@ -75,7 +75,7 @@
int getentropy(void *buf, size_t len);
static int gotdata(char *buf, size_t len);
#ifdef SYS_getrandom
#if defined(SYS_getrandom) && defined(GRND_NONBLOCK)
static int getentropy_getrandom(void *buf, size_t len);
#endif
static int getentropy_urandom(void *buf, size_t len);
@@ -95,15 +95,18 @@ getentropy(void *buf, size_t len)
return (-1);
}
#ifdef SYS_getrandom
#if defined(SYS_getrandom) && defined(GRND_NONBLOCK)
/*
* Try descriptor-less getrandom()
* Try descriptor-less getrandom(), in non-blocking mode.
*
* The design of Linux getrandom is broken. It has an
* uninitialized phase coupled with blocking behaviour, which
* is unacceptable from within a library at boot time without
* possible recovery. See http://bugs.python.org/issue26839#msg267745
*/
ret = getentropy_getrandom(buf, len);
if (ret != -1)
return (ret);
if (errno != ENOSYS)
return (-1);
#endif
/*
@@ -121,7 +124,7 @@ getentropy(void *buf, size_t len)
* Try to use sysctl CTL_KERN, KERN_RANDOM, RANDOM_UUID.
* sysctl is a failsafe API, so it guarantees a result. This
* should work inside a chroot, or when file descriptors are
* exhuasted.
* exhausted.
*
* However this can fail if the Linux kernel removes support
* for sysctl. Starting in 2007, there have been efforts to
@@ -157,7 +160,7 @@ getentropy(void *buf, size_t len)
* - Do the best under the circumstances....
*
* This code path exists to bring light to the issue that Linux
* does not provide a failsafe API for entropy collection.
* still does not provide a failsafe API for entropy collection.
*
* We hope this demonstrates that Linux should either retain their
* sysctl ABI, or consider providing a new failsafe API which
@@ -191,7 +194,7 @@ gotdata(char *buf, size_t len)
return (0);
}
#ifdef SYS_getrandom
#if defined(SYS_getrandom) && defined(GRND_NONBLOCK)
static int
getentropy_getrandom(void *buf, size_t len)
{
@@ -200,7 +203,7 @@ getentropy_getrandom(void *buf, size_t len)
if (len > 256)
return (-1);
do {
ret = syscall(SYS_getrandom, buf, len, 0);
ret = syscall(SYS_getrandom, buf, len, GRND_NONBLOCK);
} while (ret == -1 && errno == EINTR);
if (ret != (int)len)