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Add a patch to obtain random bytes using getentropy()

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Signed-off-by: Björn Esser <besser82@fedoraproject.org>
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Björn Esser 2021-07-04 12:34:22 +02:00
parent 2b6f713524
commit a6d57fc8a3
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2 changed files with 130 additions and 1 deletions
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123
shadow-4.8.1-getentropy_random_bytes.patch Normal file
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@ -0,0 +1,123 @@
From c82ed0c15e0e9e47df0b4c22672b72e35f061a9d
From: =?UTF-8?q?Bj=C3=B6rn=20Esser?= <besser82@fedoraproject.org>
Date: Sun, 4 Jul 2021 12:10:11 +0200
Subject: [PATCH] libmisc/salt.c: Use secure system ressources to obtain random
bytes.
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
In a previous commit we introduced /dev/urandom as a source to obtain
random bytes from. This may not be available on all systems, or when
operating inside of a chroot.
Almost all systems provide functions to obtain random bytes from
secure system ressources. Thus we should prefer to use these, and
fall back to /dev/urandom, if there is no such function present, as
a last resort.
Signed-off-by: Björn Esser <besser82@fedoraproject.org>
---
configure.ac | 17 +++++++++--------
libmisc/salt.c | 42 ++++++++++++++++++++++++++++++++++++------
2 files changed, 45 insertions(+), 14 deletions(-)
Index: shadow-4.8.1/configure.ac
===================================================================
--- shadow-4.8.1.orig/configure.ac
+++ shadow-4.8.1/configure.ac
@@ -44,18 +44,19 @@ AC_HEADER_STDBOOL
AC_CHECK_HEADERS(crypt.h errno.h fcntl.h limits.h unistd.h sys/time.h utmp.h \
utmpx.h termios.h termio.h sgtty.h sys/ioctl.h syslog.h paths.h \
- utime.h ulimit.h sys/capability.h sys/resource.h gshadow.h lastlog.h \
- locale.h rpc/key_prot.h netdb.h acl/libacl.h attr/libattr.h \
- attr/error_context.h)
+ utime.h ulimit.h sys/capability.h sys/random.h sys/resource.h \
+ gshadow.h lastlog.h locale.h rpc/key_prot.h netdb.h acl/libacl.h \
+ attr/libattr.h attr/error_context.h)
dnl shadow now uses the libc's shadow implementation
AC_CHECK_HEADER([shadow.h],,[AC_MSG_ERROR([You need a libc with shadow.h])])
-AC_CHECK_FUNCS(l64a fchmod fchown fsync futimes getgroups gethostname getspnam \
- gettimeofday getusershell getutent initgroups lchown lckpwdf lstat \
- lutimes memcpy memset setgroups sigaction strchr updwtmp updwtmpx innetgr \
- getpwnam_r getpwuid_r getgrnam_r getgrgid_r getspnam_r getaddrinfo \
- ruserok dlopen)
+AC_CHECK_FUNCS(arc4random_buf l64a fchmod fchown fsync futimes getgroups \
+ gethostname getentropy getrandom getspnam gettimeofday getusershell \
+ getutent initgroups lchown lckpwdf lstat lutimes memcpy memset \
+ setgroups sigaction strchr updwtmp updwtmpx innetgr getpwnam_r \
+ getpwuid_r getgrnam_r getgrgid_r getspnam_r getaddrinfo ruserok \
+ dlopen)
AC_SYS_LARGEFILE
dnl Checks for typedefs, structures, and compiler characteristics.
Index: shadow-4.8.1/libmisc/salt.c
===================================================================
--- shadow-4.8.1.orig/libmisc/salt.c
+++ shadow-4.8.1/libmisc/salt.c
@@ -15,6 +15,9 @@
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
+#if HAVE_SYS_RANDOM_H
+#include <sys/random.h>
+#endif
#include "prototypes.h"
#include "defines.h"
#include "getdef.h"
@@ -128,19 +131,46 @@ static /*@observer@*/char *l64a (long va
static long read_random_bytes (void)
{
long randval = 0;
- FILE *f = fopen ("/dev/urandom", "r");
- if (fread (&randval, sizeof (randval), 1, f) != sizeof (randval))
- {
- fprintf (shadow_logfd,
- _("Unable to read from /dev/urandom.\n"));
+#ifdef HAVE_ARC4RANDOM_BUF
+ /* arc4random_buf, if it exists, can never fail. */
+ arc4random_buf (&randval, sizeof (randval));
+ goto end;
+
+#elif defined(HAVE_GETENTROPY)
+ /* getentropy may exist but lack kernel support. */
+ if (getentropy (&randval, sizeof (randval))) {
+ goto fail;
+ }
+
+ goto end;
+
+#elif defined(HAVE_GETRANDOM)
+ /* Likewise getrandom. */
+ if ((size_t) getrandom (&randval, sizeof (randval), 0) != sizeof (randval)) {
+ goto fail;
+ }
+ goto end;
+
+#else
+ FILE *f = fopen ("/dev/urandom", "r");
+
+ if (fread (&randval, sizeof (randval), 1, f) != sizeof (randval)) {
fclose(f);
- exit (1);
+ goto fail;
}
fclose(f);
+ goto end;
+#endif
+
+fail:
+ fprintf (shadow_logfd,
+ _("Unable to obtain random bytes.\n"));
+ exit (1);
+end:
return randval;
}

8
shadow-utils.spec
View File

@ -1,7 +1,7 @@
Summary: Utilities for managing accounts and shadow password files
Name: shadow-utils
Version: 4.8.1
Release: 15%{?dist}
Release: 16%{?dist}
Epoch: 2
URL: https://github.com/shadow-maint/shadow
Source0: https://github.com/shadow-maint/shadow/releases/download/%{version}/shadow-%{version}.tar.xz
@ -116,6 +116,8 @@ Patch63: shadow-4.8.1-salt_c_comments.patch
Patch64: shadow-4.8.1-salt_c_use_dev_urandom.patch
# https://github.com/shadow-maint/shadow/commit/2c542f6c65f858b3dba20f58db4da56572f67a54
Patch65: shadow-4.8.1-useradd_create_relative_home_path_correctly.patch
# https://github.com/shadow-maint/shadow/commit/c82ed0c15e0e9e47df0b4c22672b72e35f061a9d
Patch66: shadow-4.8.1-getentropy_random_bytes.patch
License: BSD and GPLv2+
BuildRequires: make
@ -206,6 +208,7 @@ Development files for shadow-utils-subid.
%patch63 -p1 -b .comments
%patch64 -p1 -b .use_dev_urandom
%patch65 -p1 -b .useradd_create_relative_home_path_correctly
%patch66 -p1 -b .getentropy_random_bytes
iconv -f ISO88591 -t utf-8 doc/HOWTO > doc/HOWTO.utf8
cp -f doc/HOWTO.utf8 doc/HOWTO
@ -375,6 +378,9 @@ rm -f $RPM_BUILD_ROOT/%{_libdir}/libsubid.la
%{_libdir}/libsubid.so
%changelog
* Sun Jul 04 2021 Björn Esser <besser82@fedoraproject.org> - 2:4.8.1-16
- Add a patch to obtain random bytes using getentropy()
* Tue Jun 29 2021 Iker Pedrosa <ipedrosa@redhat.com> - 2:4.8.1-15
- useradd: free correct pointer (#1976809)