[libvirt] [PATCH 2/2] Add support for using 3-arg pkcheck syntax for process (CVE-2013-4311)
From: "Daniel P. Berrange" <berrange(a)redhat.com>
With the existing pkcheck (pid, start time) tuple for identifying
the process, there is a race condition, where a process can make
a libvirt RPC call and in another thread exec a setuid application,
causing it to change to effective UID 0. This in turn causes polkit
to do its permission check based on the wrong UID.
To address this, libvirt must get the UID the caller had at time
of connect() (from SO_PEERCRED) and pass a (pid, start time, uid)
triple to the pkcheck program.
This fix requires that libvirt is re-built against a version of
polkit that has the fix for its CVE-2013-4288, so that libvirt
can see 'pkg-config --variable pkcheck_supports_uid polkit-gobject-1'
Signed-off-by: Colin Walters <walters(a)redhat.com>
Signed-off-by: Daniel P. Berrange <berrange(a)redhat.com>
(cherry picked from commit 922b7fda77b094dbf022d625238262ea05335666)
Signed-off-by: Eric Blake <eblake(a)redhat.com>
Conflicts:
configure.ac - context
libvirt.spec.in - context of indentation
src/access/viraccessdriverpolkit.c - not present on this branch
---
configure.ac | 8 ++++++++
daemon/remote.c | 22 +++++++++++++++++++---
libvirt.spec.in | 3 +--
3 files changed, 28 insertions(+), 5 deletions(-)
diff --git a/configure.ac b/configure.ac
index 5825517..ea0fde6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1270,6 +1270,14 @@ if test "x$with_polkit" = "xyes" || test
"x$with_polkit" = "xcheck"; then
AC_PATH_PROG([PKCHECK_PATH],[pkcheck], [], [/usr/sbin:$PATH])
if test "x$PKCHECK_PATH" != "x" ; then
AC_DEFINE_UNQUOTED([PKCHECK_PATH],["$PKCHECK_PATH"],[Location of pkcheck
program])
+ AC_MSG_CHECKING([whether pkcheck supports uid value])
+ pkcheck_supports_uid=`$PKG_CONFIG --variable pkcheck_supports_uid polkit-gobject-1`
+ if test "x$pkcheck_supports_uid" = "xtrue"; then
+ AC_MSG_RESULT([yes])
+ AC_DEFINE_UNQUOTED([PKCHECK_SUPPORTS_UID], 1, [Pass uid to pkcheck])
+ else
+ AC_MSG_RESULT([no])
+ fi
AC_DEFINE_UNQUOTED([HAVE_POLKIT], 1,
[use PolicyKit for UNIX socket access checks])
AC_DEFINE_UNQUOTED([HAVE_POLKIT1], 1,
diff --git a/daemon/remote.c b/daemon/remote.c
index dd608cd..ab2d639 100644
--- a/daemon/remote.c
+++ b/daemon/remote.c
@@ -2792,10 +2792,12 @@ remoteDispatchAuthPolkit(virNetServerPtr server ATTRIBUTE_UNUSED,
int status = -1;
char *ident = NULL;
bool authdismissed = 0;
+ bool supportsuid = false;
char *pkout = NULL;
struct daemonClientPrivate *priv =
virNetServerClientGetPrivateData(client);
virCommandPtr cmd = NULL;
+ static bool polkitInsecureWarned;
virMutexLock(&priv->lock);
action = virNetServerClientGetReadonly(client) ?
@@ -2817,14 +2819,28 @@ remoteDispatchAuthPolkit(virNetServerPtr server ATTRIBUTE_UNUSED,
goto authfail;
}
+ if (timestamp == 0) {
+ VIR_WARN("Failing polkit auth due to missing client (pid=%lld) start
time",
+ (long long)callerPid);
+ goto authfail;
+ }
+
VIR_INFO("Checking PID %lld running as %d",
(long long) callerPid, callerUid);
virCommandAddArg(cmd, "--process");
- if (timestamp != 0) {
- virCommandAddArgFormat(cmd, "%lld,%llu", (long long) callerPid,
timestamp);
+# ifdef PKCHECK_SUPPORTS_UID
+ supportsuid = true;
+# endif
+ if (supportsuid) {
+ virCommandAddArgFormat(cmd, "%lld,%llu,%lu",
+ (long long) callerPid, timestamp, (unsigned long)
callerUid);
} else {
- virCommandAddArgFormat(cmd, "%lld", (long long) callerPid);
+ if (!polkitInsecureWarned) {
+ VIR_WARN("No support for caller UID with pkcheck. This deployment is
known to be insecure.");
+ polkitInsecureWarned = true;
+ }
+ virCommandAddArgFormat(cmd, "%lld,%llu", (long long) callerPid,
timestamp);
}
virCommandAddArg(cmd, "--allow-user-interaction");
diff --git a/libvirt.spec.in b/libvirt.spec.in
index bb6b2d5..37718c5 100644
--- a/libvirt.spec.in
+++ b/libvirt.spec.in
@@ -456,8 +456,7 @@ BuildRequires: cyrus-sasl-devel
%endif
%if %{with_polkit}
%if 0%{?fedora} >= 12 || 0%{?rhel} >= 6
-# Only need the binary, not -devel
-BuildRequires: polkit >= 0.93
+BuildRequires: polkit-devel >= 0.93
%else
BuildRequires: PolicyKit-devel >= 0.6
%endif
--
1.8.3.1