File U_Use-getentropy-if-arc4random_buf-is-not-available.patch of Package libICE
From ff5e59f32255913bb1cdf51441b98c9107ae165b Mon Sep 17 00:00:00 2001
From: Benjamin Tissoires <benjamin.tissoires@gmail.com>
Date: Tue, 4 Apr 2017 19:12:53 +0200
Subject: [PATCH] Use getentropy() if arc4random_buf() is not available
This allows to fix CVE-2017-2626 on Linux platforms without pulling in
libbsd.
The libc getentropy() is available since glibc 2.25 but also on OpenBSD.
For Linux, we need at least a v3.17 kernel. If the recommended
arc4random_buf() function is not available, emulate it by first trying
to use getentropy() on a supported glibc and kernel. If the call fails,
fall back to the current (partly vulnerable) code.
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>
Reviewed-by: Mark Kettenis <kettenis@openbsd.org>
Reviewed-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
---
configure.ac | 2 +-
src/iceauth.c | 65 ++++++++++++++++++++++++++++++++++++++++++-----------------
2 files changed, 47 insertions(+), 20 deletions(-)
Index: libICE-1.0.9/configure.ac
===================================================================
--- libICE-1.0.9.orig/configure.ac
+++ libICE-1.0.9/configure.ac
@@ -38,7 +38,7 @@ AC_DEFINE(ICE_t, 1, [Xtrans transport ty
# Checks for library functions.
AC_CHECK_LIB([bsd], [arc4random_buf])
-AC_CHECK_FUNCS([asprintf arc4random_buf])
+AC_CHECK_FUNCS([asprintf arc4random_buf getentropy])
# Allow checking code with lint, sparse, etc.
XORG_WITH_LINT
Index: libICE-1.0.9/src/iceauth.c
===================================================================
--- libICE-1.0.9.orig/src/iceauth.c
+++ libICE-1.0.9/src/iceauth.c
@@ -42,31 +42,19 @@ Author: Ralph Mor, X Consortium
static int was_called_state;
-/*
- * MIT-MAGIC-COOKIE-1 is a sample authentication method implemented by
- * the SI. It is not part of standard ICElib.
- */
+#ifndef HAVE_ARC4RANDOM_BUF
-
-char *
-IceGenerateMagicCookie (
+static void
+emulate_getrandom_buf (
+ char *auth,
int len
)
{
- char *auth;
-#ifndef HAVE_ARC4RANDOM_BUF
long ldata[2];
int seed;
int value;
int i;
-#endif
-
- if ((auth = malloc (len + 1)) == NULL)
- return (NULL);
-#ifdef HAVE_ARC4RANDOM_BUF
- arc4random_buf(auth, len);
-#else
#ifdef ITIMER_REAL
{
struct timeval now;
@@ -74,13 +62,13 @@ IceGenerateMagicCookie (
ldata[0] = now.tv_sec;
ldata[1] = now.tv_usec;
}
-#else
+#else /* ITIMER_REAL */
{
long time ();
ldata[0] = time ((long *) 0);
ldata[1] = getpid ();
}
-#endif
+#endif /* ITIMER_REAL */
seed = (ldata[0]) + (ldata[1] << 16);
srand (seed);
for (i = 0; i < len; i++)
@@ -88,7 +76,169 @@ IceGenerateMagicCookie (
value = rand ();
auth[i] = value & 0xff;
}
+}
+
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE // needed on SLE11 for O_CLOEXEC
#endif
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <linux/random.h>
+#include <sys/syscall.h>
+
+int getentropy_urandom(void *buffer, size_t length)
+{
+ int random_fd = -1;
+ ssize_t res = -1;
+ size_t filled = 0;
+
+ if( length > 256 )
+ {
+ errno = EIO;
+ return -1;
+ }
+
+ random_fd = open("/dev/urandom", O_RDONLY | O_CLOEXEC);
+
+ if( random_fd == -1 )
+ {
+ return -1;
+ }
+
+ while( filled < length )
+ {
+ res = read(random_fd, (char*)buffer + filled, length - filled);
+
+ if( res == -1 )
+ {
+ // shouldn't actually happen acc. to man(4) random,
+ // but you never know
+ if( errno == EINTR )
+ continue;
+
+ close(random_fd);
+ return -1;
+ }
+ else if( res == 0 )
+ {
+ // no more bytes available? should not happen
+ errno = EIO;
+ close(random_fd);
+ return -1;
+ }
+
+ filled += res;
+ }
+
+ close(random_fd);
+ return 0;
+}
+
+int getentropy_getrandom(void *buffer, size_t length)
+{
+ int res;
+ size_t filled = 0;
+
+ if( length > 256 )
+ {
+ errno = EIO;
+ return -1;
+ }
+
+ while( filled < length )
+ {
+#ifdef SYS_getrandom
+ /*
+ * glibc does not contain a syscall wrapper for this in older
+ * versions
+ */
+ res = syscall(SYS_getrandom, (char*)buffer + filled, length - filled, 0);
+#else
+# warning no getrandom
+ errno = ENOSYS;
+ return -1;
+#endif // SYS_getrandom
+
+ if( res == -1 )
+ {
+ if( errno == EINTR )
+ continue;
+
+ return -1;
+ }
+ else if( res == 0 )
+ {
+ // no more bytes available? should not happen
+ errno = EIO;
+ return -1;
+ }
+
+ filled += res;
+ }
+
+ return 0;
+}
+
+int getentropy_emulate(void *buffer, size_t length)
+{
+ /*
+ * check at runtime whether we have a getrandom system call available,
+ * otherwise fall back to urandom approach. autoconf check for
+ * getrandom() does not work, because there's been no declaration for
+ * it for years.
+ */
+ int res = getentropy_getrandom(buffer, length);
+
+ if( res == -1 && errno == ENOSYS )
+ {
+ return getentropy_urandom(buffer, length);
+ }
+
+ return res;
+}
+
+static void
+arc4random_buf (
+ char *auth,
+ int len
+)
+{
+ int ret;
+
+#if HAVE_GETENTROPY
+ /* weak emulation of arc4random through the entropy libc */
+ ret = getentropy (auth, len);
+#else
+ ret = getentropy_emulate (auth, len);
+#endif /* HAVE_GETENTROPY */
+ if (ret == 0)
+ return;
+
+ emulate_getrandom_buf (auth, len);
+}
+
+#endif /* !defined(HAVE_ARC4RANDOM_BUF) */
+
+/*
+ * MIT-MAGIC-COOKIE-1 is a sample authentication method implemented by
+ * the SI. It is not part of standard ICElib.
+ */
+
+
+char *
+IceGenerateMagicCookie (
+ int len
+)
+{
+ char *auth;
+
+ if ((auth = malloc (len + 1)) == NULL)
+ return (NULL);
+
+ arc4random_buf (auth, len);
+
auth[len] = '\0';
return (auth);
}
