Add support for using 3-arg pkcheck syntax for process (CVE-2013-4311)

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@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
(cherry picked from commit 922b7fda77b094dbf022d625238262ea05335666)

diff --git a/configure.ac b/configure.ac
index 9b3dbd46d4d464a01c75c288baaf813fe50f69bd..1593603ca194c4f59fddd28e35660177962f27c9 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -1153,6 +1153,14 @@ 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([WITH_POLKIT], 1,
         [use PolicyKit for UNIX socket access checks])
     AC_DEFINE_UNQUOTED([WITH_POLKIT1], 1,

diff --git a/daemon/remote.c b/daemon/remote.c
index a11ba942f3f49e8450b44cbb7a72faba0ea4b4ba..8329c7c08dac488e10ad61e1ba6ab2bd7f9ddd17 100644 (file)
--- a/daemon/remote.c
+++ b/daemon/remote.c
@@ -2731,10 +2731,12 @@ 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) ?
@@ -2756,14 +2758,28 @@ 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 a3a831f58ee6a4435b82ac862a4e737cda481135..78f72d11f6e2a51e7ba83b745d6b687c3db664b8 100644 (file)
--- a/libvirt.spec.in
+++ b/libvirt.spec.in
@@ -487,8 +487,7 @@ 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

diff --git a/src/access/viraccessdriverpolkit.c b/src/access/viraccessdriverpolkit.c
index 4c76e64ebb2ed5d5085521385d9fc38e6adb24be..bb170b5d94fee55e867fbf4861b2d1f831f79050 100644 (file)
--- a/src/access/viraccessdriverpolkit.c
+++ b/src/access/viraccessdriverpolkit.c
@@ -72,8 +72,12 @@ static char *
 virAccessDriverPolkitFormatProcess(const char *actionid)
 {
     virIdentityPtr identity = virIdentityGetCurrent();
-    const char *process = NULL;
+    const char *callerPid = NULL;
+    const char *callerTime = NULL;
+    const char *callerUid = NULL;
     char *ret = NULL;
+    bool supportsuid = false;
+    static bool polkitInsecureWarned;
 
     if (!identity) {
         virAccessError(VIR_ERR_ACCESS_DENIED,
@@ -81,17 +85,43 @@ virAccessDriverPolkitFormatProcess(const char *actionid)
                        actionid);
         return NULL;
     }
-    if (virIdentityGetAttr(identity, VIR_IDENTITY_ATTR_UNIX_PROCESS_ID, &process) < 0)
+    if (virIdentityGetAttr(identity, VIR_IDENTITY_ATTR_UNIX_PROCESS_ID, &callerPid) < 0)
+        goto cleanup;
+    if (virIdentityGetAttr(identity, VIR_IDENTITY_ATTR_UNIX_PROCESS_TIME, &callerTime) < 0)
+        goto cleanup;
+    if (virIdentityGetAttr(identity, VIR_IDENTITY_ATTR_UNIX_USER_ID, &callerUid) < 0)
         goto cleanup;
 
-    if (!process) {
+    if (!callerPid) {
         virAccessError(VIR_ERR_INTERNAL_ERROR, "%s",
                        _("No UNIX process ID available"));
         goto cleanup;
     }
-
-    if (VIR_STRDUP(ret, process) < 0)
+    if (!callerTime) {
+        virAccessError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("No UNIX process start time available"));
+        goto cleanup;
+    }
+    if (!callerUid) {
+        virAccessError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("No UNIX caller UID available"));
         goto cleanup;
+    }
+
+#ifdef PKCHECK_SUPPORTS_UID
+    supportsuid = true;
+#endif
+    if (supportsuid) {
+        if (virAsprintf(&ret, "%s,%s,%s", callerPid, callerTime, callerUid) < 0)
+            goto cleanup;
+    } else {
+        if (!polkitInsecureWarned) {
+            VIR_WARN("No support for caller UID with pkcheck. This deployment is known to be insecure.");
+            polkitInsecureWarned = true;
+        }
+        if (virAsprintf(&ret, "%s,%s", callerPid, callerTime) < 0)
+            goto cleanup;
+    }
 
 cleanup:
     virObjectUnref(identity);