Use getrandom syscall instead of pulling in libbsd

This commit is contained in:
Benjamin Tissoires 2017-04-26 13:44:35 +02:00
parent d1011d3731
commit a9c53bc5a1
3 changed files with 229 additions and 2 deletions

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@ -0,0 +1,143 @@
From 8044880840bcde6f15a078e267cf163072ac1878 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 libICE 1/2] 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(-)
diff --git a/configure.ac b/configure.ac
index 458882a..c971ab6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -38,7 +38,7 @@ AC_DEFINE(ICE_t, 1, [Xtrans transport type])
# 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
diff --git a/src/iceauth.c b/src/iceauth.c
index ef66626..9b77eac 100644
--- a/src/iceauth.c
+++ b/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 +76,46 @@ IceGenerateMagicCookie (
value = rand ();
auth[i] = value & 0xff;
}
-#endif
+}
+
+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);
+ if (ret == 0)
+ return;
+#endif /* HAVE_GETENTROPY */
+
+ 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);
}
--
2.9.3

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@ -0,0 +1,75 @@
From 6a92ea98544e0d03d4ce0563ad765ae21773b0fd Mon Sep 17 00:00:00 2001
From: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Date: Tue, 25 Apr 2017 11:00:36 +0200
Subject: [PATCH libICE 2/2] Add getentropy emulation through syscall
RHEL/f24/f25 only patch
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
---
src/iceauth.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 49 insertions(+)
diff --git a/src/iceauth.c b/src/iceauth.c
index 9b77eac..9af62f5 100644
--- a/src/iceauth.c
+++ b/src/iceauth.c
@@ -78,6 +78,55 @@ emulate_getrandom_buf (
}
}
+#ifndef HAVE_GETENTROPY
+#include <sys/syscall.h>
+#include <errno.h>
+
+/* code taken from libressl, license: */
+/*
+ * Copyright (c) 2014 Theo de Raadt <deraadt@openbsd.org>
+ * Copyright (c) 2014 Bob Beck <beck@obtuse.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ * Emulation of getentropy(2) as documented at:
+ * http://man.openbsd.org/getentropy.2
+ */
+#ifdef __NR_getrandom
+static int
+getentropy(void *buf, size_t len)
+{
+ int pre_errno = errno;
+ int ret;
+ if (len > 256)
+ return (-1);
+ do {
+ ret = syscall(__NR_getrandom, buf, len, 0);
+ } while (ret == -1 && errno == EINTR);
+
+ if (ret != len)
+ return (-1);
+ errno = pre_errno;
+
+ fprintf(stderr, "generating cookie with syscall\n");
+
+ return (0);
+}
+#define HAVE_GETENTROPY 1
+#endif /* __NR_getrandom */
+
+#endif /* HAVE_GETENTROPY */
+
static void
arc4random_buf (
char *auth,
--
2.9.3

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@ -1,16 +1,18 @@
Summary: X.Org X11 ICE runtime library
Name: libICE
Version: 1.0.9
Release: 8%{?dist}
Release: 9%{?dist}
License: MIT
Group: System Environment/Libraries
URL: http://www.x.org
Source0: ftp://ftp.x.org/pub/individual/lib/%{name}-%{version}.tar.bz2
Patch0: 0001-Use-getentropy-if-arc4random_buf-is-not-available.patch
Patch1: 0002-Add-getentropy-emulation-through-syscall.patch
BuildRequires: xorg-x11-util-macros
BuildRequires: autoconf automake libtool
BuildRequires: libbsd-devel
BuildRequires: pkgconfig
BuildRequires: xorg-x11-proto-devel
BuildRequires: xorg-x11-xtrans-devel >= 1.0.3-5
@ -29,6 +31,9 @@ The X.Org X11 ICE (Inter-Client Exchange) development package.
%prep
%setup -q
%patch0 -p1 -b .cve-2017-2626
%patch1 -p1 -b .cve-2017-2626
%build
autoreconf -v --install --force
%configure --disable-static \
@ -70,6 +75,10 @@ rm -rf $RPM_BUILD_ROOT
%{_libdir}/pkgconfig/ice.pc
%changelog
* Wed May 03 2017 Benjamin Tissoires <benjamin.tissoires@redhat.com> 1.0.9-9
- Add upstream patch to not pull libbsd
- Add custom patch for Fedora 24 & 25
* Wed Mar 01 2017 Benjamin Tissoires <benjamin.tissoires@redhat.com> 1.0.9-8
- Fix changelog