+++ /dev/null
-From 1252dc1d1f465b8ab6b36ff7252e395e66a040cf Mon Sep 17 00:00:00 2001
-From: Simon McVittie <smcv@debian.org>
-Date: Fri, 21 Jul 2017 10:46:39 +0100
-Subject: [PATCH 1/2] config-loader-expat: Tell Expat not to defend against
- hash collisions
-
-By default, Expat uses cryptographic-quality random numbers as a salt for
-its hash algorithm, and since 2.2.1 it gets them from the getrandom
-syscall on Linux. That syscall refuses to return any entropy until the
-kernel's CSPRNG (random pool) has been initialized. Unfortunately, this
-can take as long as 40 seconds on embedded devices with few entropy
-sources, which is too long: if the system dbus-daemon blocks for that
-length of time, important D-Bus clients like systemd and systemd-logind
-time out and fail to connect to it.
-
-We're parsing small configuration files here, and we trust them
-completely, so we don't need to defend against hash collisions: nobody
-is going to be crafting them to cause pathological performance.
-
-Bug: https://bugs.freedesktop.org/show_bug.cgi?id=101858
-Signed-off-by: Simon McVittie <smcv@debian.org>
-Tested-by: Christopher Hewitt <hewitt@ieee.org>
-Reviewed-by: Philip Withnall <withnall@endlessm.com>
-
-Upstream commit 1252dc1d1f465b8ab6b36ff7252e395e66a040cf
-Signed-off-by: Marcus Hoffmann <m.hoffmann@cartelsol.com>
----
- bus/config-loader-expat.c | 14 ++++++++++++++
- configure.ac | 8 ++++++++
- 2 files changed, 22 insertions(+)
-
-diff --git a/bus/config-loader-expat.c b/bus/config-loader-expat.c
-index b571fda3..27cbe2d0 100644
---- a/bus/config-loader-expat.c
-+++ b/bus/config-loader-expat.c
-@@ -203,6 +203,20 @@ bus_config_load (const DBusString *file,
- goto failed;
- }
-
-+ /* We do not need protection against hash collisions (CVE-2012-0876)
-+ * because we are only parsing trusted XML; and if we let Expat block
-+ * waiting for the CSPRNG to be initialized, as it does by default to
-+ * defeat CVE-2012-0876, it can cause timeouts during early boot on
-+ * entropy-starved embedded devices.
-+ *
-+ * TODO: When Expat gets a more explicit API for this than
-+ * XML_SetHashSalt, check for that too, and use it preferentially.
-+ * https://github.com/libexpat/libexpat/issues/91 */
-+#if defined(HAVE_XML_SETHASHSALT)
-+ /* Any nonzero number will do. https://xkcd.com/221/ */
-+ XML_SetHashSalt (expat, 4);
-+#endif
-+
- if (!_dbus_string_get_dirname (file, &dirname))
- {
- dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
-diff --git a/configure.ac b/configure.ac
-index 52da11fb..c4022ed7 100644
---- a/configure.ac
-+++ b/configure.ac
-@@ -938,6 +938,14 @@ XML_CFLAGS=
- AC_SUBST([XML_CFLAGS])
- AC_SUBST([XML_LIBS])
-
-+save_cflags="$CFLAGS"
-+save_libs="$LIBS"
-+CFLAGS="$CFLAGS $XML_CFLAGS"
-+LIBS="$LIBS $XML_LIBS"
-+AC_CHECK_FUNCS([XML_SetHashSalt])
-+CFLAGS="$save_cflags"
-+LIBS="$save_libs"
-+
- # Thread lib detection
- AC_ARG_VAR([THREAD_LIBS])
- save_libs="$LIBS"
---
-2.11.0
-
projects / buildroot.git / commitdiff