path: root/fix-CVE-2015-3164.patch

From c4534a38b68aa07fb82318040dc8154fb48a9588 Mon Sep 17 00:00:00 2001
From: Ray Strode <rstrode@redhat.com>
Date: Tue, 5 May 2015 16:43:42 -0400
Subject: xwayland: Enable access control on open sockets [CVE-2015-3164 1/3]

Xwayland currently allows wide-open access to the X sockets
it listens on, ignoring Xauth access control.

This commit makes sure to enable access control on the sockets,
so one user can't snoop on another user's X-over-wayland
applications.

Signed-off-by: Ray Strode <rstrode@redhat.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Signed-off-by: Keith Packard <keithp@keithp.com>

diff --git a/hw/xwayland/xwayland.c b/hw/xwayland/xwayland.c
index 7e8d667..c5bee77 100644
--- a/hw/xwayland/xwayland.c
+++ b/hw/xwayland/xwayland.c
@@ -483,7 +483,7 @@ listen_on_fds(struct xwl_screen *xwl_screen)
     int i;
 
     for (i = 0; i < xwl_screen->listen_fd_count; i++)
-        ListenOnOpenFD(xwl_screen->listen_fds[i], TRUE);
+        ListenOnOpenFD(xwl_screen->listen_fds[i], FALSE);
 }
 
 static void
-- 
cgit v0.10.2
From 4b4b9086d02b80549981d205fb1f495edc373538 Mon Sep 17 00:00:00 2001
From: Ray Strode <rstrode@redhat.com>
Date: Tue, 5 May 2015 16:43:43 -0400
Subject: os: support new implicit local user access mode [CVE-2015-3164 2/3]

If the X server is started without a '-auth' argument, then
it gets started wide open to all local users on the system.

This isn't a great default access model, but changing it in
Xorg at this point would break backward compatibility.

Xwayland, on the other hand is new, and much more targeted
in scope.  It could, in theory, be changed to allow the much
more secure default of a "user who started X server can connect
clients to that server."

This commit paves the way for that change, by adding a mechanism
for DDXs to opt-in to that behavior.  They merely need to call

LocalAccessScopeUser()

in their init functions.

A subsequent commit will add that call for Xwayland.

Signed-off-by: Ray Strode <rstrode@redhat.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Signed-off-by: Keith Packard <keithp@keithp.com>

diff --git a/include/os.h b/include/os.h
index 6638c84..b2b96c8 100644
--- a/include/os.h
+++ b/include/os.h
@@ -431,11 +431,28 @@ extern _X_EXPORT void
 ResetHosts(const char *display);
 
 extern _X_EXPORT void
+EnableLocalAccess(void);
+
+extern _X_EXPORT void
+DisableLocalAccess(void);
+
+extern _X_EXPORT void
 EnableLocalHost(void);
 
 extern _X_EXPORT void
 DisableLocalHost(void);
 
+#ifndef NO_LOCAL_CLIENT_CRED
+extern _X_EXPORT void
+EnableLocalUser(void);
+
+extern _X_EXPORT void
+DisableLocalUser(void);
+
+extern _X_EXPORT void
+LocalAccessScopeUser(void);
+#endif
+
 extern _X_EXPORT void
 AccessUsingXdmcp(void);
 
diff --git a/os/access.c b/os/access.c
index 8fa028e..75e7a69 100644
--- a/os/access.c
+++ b/os/access.c
@@ -102,6 +102,10 @@ SOFTWARE.
 #include <sys/ioctl.h>
 #include <ctype.h>
 
+#ifndef NO_LOCAL_CLIENT_CRED
+#include <pwd.h>
+#endif
+
 #if defined(TCPCONN) || defined(STREAMSCONN)
 #include <netinet/in.h>
 #endif                          /* TCPCONN || STREAMSCONN */
@@ -225,6 +229,13 @@ static int LocalHostEnabled = FALSE;
 static int LocalHostRequested = FALSE;
 static int UsingXdmcp = FALSE;
 
+static enum {
+    LOCAL_ACCESS_SCOPE_HOST = 0,
+#ifndef NO_LOCAL_CLIENT_CRED
+    LOCAL_ACCESS_SCOPE_USER,
+#endif
+} LocalAccessScope;
+
 /* FamilyServerInterpreted implementation */
 static Bool siAddrMatch(int family, void *addr, int len, HOST * host,
                         ClientPtr client);
@@ -237,6 +248,21 @@ static void siTypesInitialize(void);
  */
 
 void
+EnableLocalAccess(void)
+{
+    switch (LocalAccessScope) {
+        case LOCAL_ACCESS_SCOPE_HOST:
+            EnableLocalHost();
+            break;
+#ifndef NO_LOCAL_CLIENT_CRED
+        case LOCAL_ACCESS_SCOPE_USER:
+            EnableLocalUser();
+            break;
+#endif
+    }
+}
+
+void
 EnableLocalHost(void)
 {
     if (!UsingXdmcp) {
@@ -249,6 +275,21 @@ EnableLocalHost(void)
  * called when authorization is enabled to keep us secure
  */
 void
+DisableLocalAccess(void)
+{
+    switch (LocalAccessScope) {
+        case LOCAL_ACCESS_SCOPE_HOST:
+            DisableLocalHost();
+            break;
+#ifndef NO_LOCAL_CLIENT_CRED
+        case LOCAL_ACCESS_SCOPE_USER:
+            DisableLocalUser();
+            break;
+#endif
+    }
+}
+
+void
 DisableLocalHost(void)
 {
     HOST *self;
@@ -262,6 +303,74 @@ DisableLocalHost(void)
     }
 }
 
+#ifndef NO_LOCAL_CLIENT_CRED
+static int GetLocalUserAddr(char **addr)
+{
+    static const char *type = "localuser";
+    static const char delimiter = '\0';
+    static const char *value;
+    struct passwd *pw;
+    int length = -1;
+
+    pw = getpwuid(getuid());
+
+    if (pw == NULL || pw->pw_name == NULL)
+        goto out;
+
+    value = pw->pw_name;
+
+    length = asprintf(addr, "%s%c%s", type, delimiter, value);
+
+    if (length == -1) {
+        goto out;
+    }
+
+    /* Trailing NUL */
+    length++;
+
+out:
+    return length;
+}
+
+void
+EnableLocalUser(void)
+{
+    char *addr = NULL;
+    int length = -1;
+
+    length = GetLocalUserAddr(&addr);
+
+    if (length == -1)
+        return;
+
+    NewHost(FamilyServerInterpreted, addr, length, TRUE);
+
+    free(addr);
+}
+
+void
+DisableLocalUser(void)
+{
+    char *addr = NULL;
+    int length = -1;
+
+    length = GetLocalUserAddr(&addr);
+
+    if (length == -1)
+        return;
+
+    RemoveHost(NULL, FamilyServerInterpreted, length, addr);
+
+    free(addr);
+}
+
+void
+LocalAccessScopeUser(void)
+{
+    LocalAccessScope = LOCAL_ACCESS_SCOPE_USER;
+}
+#endif
+
 /*
  * called at init time when XDMCP will be used; xdmcp always
  * adds local hosts manually when needed
diff --git a/os/auth.c b/os/auth.c
index 5fcb538..7da6fc6 100644
--- a/os/auth.c
+++ b/os/auth.c
@@ -181,11 +181,11 @@ CheckAuthorization(unsigned int name_length,
 
         /*
          * If the authorization file has at least one entry for this server,
-         * disable local host access. (loadauth > 0)
+         * disable local access. (loadauth > 0)
          *
          * If there are zero entries (either initially or when the
          * authorization file is later reloaded), or if a valid
-         * authorization file was never loaded, enable local host access.
+         * authorization file was never loaded, enable local access.
          * (loadauth == 0 || !loaded)
          *
          * If the authorization file was loaded initially (with valid
@@ -194,11 +194,11 @@ CheckAuthorization(unsigned int name_length,
          */
 
         if (loadauth > 0) {
-            DisableLocalHost(); /* got at least one */
+            DisableLocalAccess(); /* got at least one */
             loaded = TRUE;
         }
         else if (loadauth == 0 || !loaded)
-            EnableLocalHost();
+            EnableLocalAccess();
     }
     if (name_length) {
         for (i = 0; i < NUM_AUTHORIZATION; i++) {
-- 
cgit v0.10.2
From 76636ac12f2d1dbdf7be08222f80e7505d53c451 Mon Sep 17 00:00:00 2001
From: Ray Strode <rstrode@redhat.com>
Date: Tue, 5 May 2015 16:43:44 -0400
Subject: xwayland: default to local user if no xauth file given.
 [CVE-2015-3164 3/3]

Right now if "-auth" isn't passed on the command line, we let
any user on the system connect to the Xwayland server.

That's clearly suboptimal, given Xwayland is generally designed
to be used by one user at a time.

This commit changes the behavior, so only the user who started the
X server can connect clients to it.

Signed-off-by: Ray Strode <rstrode@redhat.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Signed-off-by: Keith Packard <keithp@keithp.com>

diff --git a/hw/xwayland/xwayland.c b/hw/xwayland/xwayland.c
index c5bee77..bc92beb 100644
--- a/hw/xwayland/xwayland.c
+++ b/hw/xwayland/xwayland.c
@@ -702,4 +702,6 @@ InitOutput(ScreenInfo * screen_info, int argc, char **argv)
     if (AddScreen(xwl_screen_init, argc, argv) == -1) {
         FatalError("Couldn't add screen\n");
     }
+
+    LocalAccessScopeUser();
 }
-- 
cgit v0.10.2