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random: switch to using getrandom() directly

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This requires a linux kernel of 3.17.0+, which seems entirely
reasonable. 3.17 went EOL in 2015, and the last supported 3.x kernel
(3.16) went EOL > 4 years ago, in 2020. For reference, the current
oldest maintained kernel is 4.14 (released 2017, EOL Jan 2024).

Support for `getrandom()` (and `getentropy()`) was added to
glibc 2.25, https://sourceware.org/legacy-ml/libc-alpha/2017-02/msg00079.html,
and we already require 2.27+.

All that being said, I don't think you would encounter a current day
system, running with kernel headers older than 3.17 (released 2014) but
also having a glibc of 2.27+ (released 2018).
This commit is contained in:
fanquake 2023-05-18 11:25:44 +01:00
parent c2ba3f5b0c
commit d5e06919db
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3 changed files with 11 additions and 24 deletions
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11
configure.ac
View File

@ -1170,12 +1170,11 @@ AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <ctime>]],
)
dnl Check for different ways of gathering OS randomness
AC_MSG_CHECKING([for Linux getrandom syscall])
AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <unistd.h>
#include <sys/syscall.h>
#include <linux/random.h>]],
[[ syscall(SYS_getrandom, nullptr, 32, 0); ]])],
[ AC_MSG_RESULT([yes]); AC_DEFINE([HAVE_SYS_GETRANDOM], [1], [Define this symbol if the Linux getrandom system call is available]) ],
AC_MSG_CHECKING([for Linux getrandom function])
AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
#include <sys/random.h>]],
[[ getrandom(nullptr, 32, 0); ]])],
[ AC_MSG_RESULT([yes]); AC_DEFINE([HAVE_GETRANDOM], [1], [Define this symbol if the Linux getrandom function call is available]) ],
[ AC_MSG_RESULT([no])]
)

2
doc/dependencies.md
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@ -20,7 +20,7 @@ You can find installation instructions in the `build-*.md` file for your platfor
| [Boost](../depends/packages/boost.mk) | [link](https://www.boost.org/users/download/) | [1.81.0](https://github.com/bitcoin/bitcoin/pull/26557) | [1.64.0](https://github.com/bitcoin/bitcoin/pull/22320) | No |
| [libevent](../depends/packages/libevent.mk) | [link](https://github.com/libevent/libevent/releases) | [2.1.12-stable](https://github.com/bitcoin/bitcoin/pull/21991) | [2.1.8](https://github.com/bitcoin/bitcoin/pull/24681) | No |
| glibc | [link](https://www.gnu.org/software/libc/) | N/A | [2.27](https://github.com/bitcoin/bitcoin/pull/27029) | Yes |
| Linux Kernel | [link](https://www.kernel.org/) | N/A | 3.2.0 | Yes |
| Linux Kernel | [link](https://www.kernel.org/) | N/A | [3.17.0](https://github.com/bitcoin/bitcoin/pull/27699) | Yes |
## Optional

22
src/random.cpp
View File

@ -28,13 +28,10 @@
#include <sys/time.h>
#endif
#ifdef HAVE_SYS_GETRANDOM
#include <sys/syscall.h>
#include <linux/random.h>
#endif
#if defined(HAVE_GETENTROPY_RAND) && defined(MAC_OSX)
#if defined(HAVE_GETRANDOM) || (defined(HAVE_GETENTROPY_RAND) && defined(MAC_OSX))
#include <sys/random.h>
#endif
#ifdef HAVE_SYSCTL_ARND
#include <sys/sysctl.h>
#endif
@ -284,23 +281,14 @@ void GetOSRand(unsigned char *ent32)
RandFailure();
}
CryptReleaseContext(hProvider, 0);
#elif defined(HAVE_SYS_GETRANDOM)
#elif defined(HAVE_GETRANDOM)
/* Linux. From the getrandom(2) man page:
* "If the urandom source has been initialized, reads of up to 256 bytes
* will always return as many bytes as requested and will not be
* interrupted by signals."
*/
int rv = syscall(SYS_getrandom, ent32, NUM_OS_RANDOM_BYTES, 0);
if (rv != NUM_OS_RANDOM_BYTES) {
if (rv < 0 && errno == ENOSYS) {
/* Fallback for kernel <3.17: the return value will be -1 and errno
* ENOSYS if the syscall is not available, in that case fall back
* to /dev/urandom.
*/
GetDevURandom(ent32);
} else {
RandFailure();
}
if (getrandom(ent32, NUM_OS_RANDOM_BYTES, 0) != NUM_OS_RANDOM_BYTES) {
RandFailure();
}
#elif defined(__OpenBSD__)
/* OpenBSD. From the arc4random(3) man page: