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From 8044880840bcde6f15a078e267cf163072ac1878 Mon Sep 17 00:00:00 2001
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From: Benjamin Tissoires <benjamin.tissoires@gmail.com>
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Date: Tue, 4 Apr 2017 19:12:53 +0200
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Subject: [PATCH libICE 1/2] Use getentropy() if arc4random_buf() is not
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available
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This allows to fix CVE-2017-2626 on Linux platforms without pulling in
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libbsd.
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The libc getentropy() is available since glibc 2.25 but also on OpenBSD.
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For Linux, we need at least a v3.17 kernel. If the recommended
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arc4random_buf() function is not available, emulate it by first trying
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to use getentropy() on a supported glibc and kernel. If the call fails,
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fall back to the current (partly vulnerable) code.
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Signed-off-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>
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Reviewed-by: Mark Kettenis <kettenis@openbsd.org>
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Reviewed-by: Alan Coopersmith <alan.coopersmith@oracle.com>
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Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
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---
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configure.ac | 2 +-
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src/iceauth.c | 65 ++++++++++++++++++++++++++++++++++++++++++-----------------
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2 files changed, 47 insertions(+), 20 deletions(-)
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diff --git a/configure.ac b/configure.ac
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index 458882a..c971ab6 100644
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--- a/configure.ac
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+++ b/configure.ac
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@@ -38,7 +38,7 @@ AC_DEFINE(ICE_t, 1, [Xtrans transport type])
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# Checks for library functions.
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AC_CHECK_LIB([bsd], [arc4random_buf])
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-AC_CHECK_FUNCS([asprintf arc4random_buf])
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+AC_CHECK_FUNCS([asprintf arc4random_buf getentropy])
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# Allow checking code with lint, sparse, etc.
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XORG_WITH_LINT
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diff --git a/src/iceauth.c b/src/iceauth.c
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index ef66626..9b77eac 100644
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--- a/src/iceauth.c
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+++ b/src/iceauth.c
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@@ -42,31 +42,19 @@ Author: Ralph Mor, X Consortium
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static int was_called_state;
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-/*
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- * MIT-MAGIC-COOKIE-1 is a sample authentication method implemented by
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- * the SI. It is not part of standard ICElib.
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- */
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+#ifndef HAVE_ARC4RANDOM_BUF
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-
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-char *
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-IceGenerateMagicCookie (
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+static void
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+emulate_getrandom_buf (
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+ char *auth,
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int len
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)
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{
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- char *auth;
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-#ifndef HAVE_ARC4RANDOM_BUF
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long ldata[2];
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int seed;
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int value;
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int i;
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-#endif
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- if ((auth = malloc (len + 1)) == NULL)
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- return (NULL);
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-
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-#ifdef HAVE_ARC4RANDOM_BUF
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- arc4random_buf(auth, len);
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-#else
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#ifdef ITIMER_REAL
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{
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struct timeval now;
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@@ -74,13 +62,13 @@ IceGenerateMagicCookie (
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ldata[0] = now.tv_sec;
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ldata[1] = now.tv_usec;
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}
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-#else
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+#else /* ITIMER_REAL */
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{
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long time ();
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ldata[0] = time ((long *) 0);
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ldata[1] = getpid ();
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}
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-#endif
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+#endif /* ITIMER_REAL */
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seed = (ldata[0]) + (ldata[1] << 16);
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srand (seed);
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for (i = 0; i < len; i++)
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@@ -88,7 +76,46 @@ IceGenerateMagicCookie (
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value = rand ();
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auth[i] = value & 0xff;
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}
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-#endif
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+}
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+
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+static void
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+arc4random_buf (
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+ char *auth,
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+ int len
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+)
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+{
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+ int ret;
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+
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+#if HAVE_GETENTROPY
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+ /* weak emulation of arc4random through the entropy libc */
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+ ret = getentropy (auth, len);
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+ if (ret == 0)
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+ return;
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+#endif /* HAVE_GETENTROPY */
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+
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+ emulate_getrandom_buf (auth, len);
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+}
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+
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+#endif /* !defined(HAVE_ARC4RANDOM_BUF) */
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+
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+/*
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+ * MIT-MAGIC-COOKIE-1 is a sample authentication method implemented by
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+ * the SI. It is not part of standard ICElib.
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+ */
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+
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+
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+char *
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+IceGenerateMagicCookie (
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+ int len
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+)
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+{
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+ char *auth;
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+
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+ if ((auth = malloc (len + 1)) == NULL)
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+ return (NULL);
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+
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+ arc4random_buf (auth, len);
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+
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auth[len] = '\0';
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return (auth);
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}
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--
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2.9.3
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