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