1 files changed, 94 insertions, 0 deletions
diff --git a/x11-misc/sddm/files/sddm-0.18.1-cve-2020-28049.patch b/x11-misc/sddm/files/sddm-0.18.1-cve-2020-28049.patch
new file mode 100644
index 00000000..8209c073
--- /dev/null
+++ b/x11-misc/sddm/files/sddm-0.18.1-cve-2020-28049.patch
@@ -0,0 +1,94 @@
+From be202f533ab98a684c6a007e8d5b4357846bc222 Mon Sep 17 00:00:00 2001
+From: Fabian Vogt <fabian@ritter-vogt.de>
+Date: Tue, 6 Oct 2020 21:21:38 +0200
+Subject: [PATCH] Fix X not having access control on startup
+
+If the auth file is empty, X allows any local application (= any user on the
+system) to connect. This is currently the case until X wrote the display
+number to sddm and sddm used that to write the entry into the file.
+To work around this chicken-and-egg problem, make use of the fact that X
+doesn't actually look at the display number in the passed auth file and just
+use :0 unconditionally. Also make sure that writing the entry was actually
+successful.
+
+CVE-2020-28049
+---
+ src/daemon/XorgDisplayServer.cpp | 25 ++++++++++++++++++++-----
+ src/daemon/XorgDisplayServer.h   |  2 +-
+ 2 files changed, 21 insertions(+), 6 deletions(-)
+
+diff --git a/src/daemon/XorgDisplayServer.cpp b/src/daemon/XorgDisplayServer.cpp
+index d04f6344..df685b2d 100644
+--- a/src/daemon/XorgDisplayServer.cpp
++++ b/src/daemon/XorgDisplayServer.cpp
+@@ -88,7 +88,7 @@ namespace SDDM {
+         return m_cookie;
+     }
+ 
+-    void XorgDisplayServer::addCookie(const QString &file) {
++    bool XorgDisplayServer::addCookie(const QString &file) {
+         // log message
+         qDebug() << "Adding cookie to" << file;
+ 
+@@ -104,13 +104,13 @@ namespace SDDM {
+ 
+         // check file
+         if (!fp)
+-            return;
++            return false;
+         fprintf(fp, "remove %s\n", qPrintable(m_display));
+         fprintf(fp, "add %s . %s\n", qPrintable(m_display), qPrintable(m_cookie));
+         fprintf(fp, "exit\n");
+ 
+         // close pipe
+-        pclose(fp);
++        return pclose(fp) == 0;
+     }
+ 
+     bool XorgDisplayServer::start() {
+@@ -127,6 +127,15 @@ namespace SDDM {
+         // log message
+         qDebug() << "Display server starting...";
+ 
++        // generate auth file.
++        // For the X server's copy, the display number doesn't matter.
++        // An empty file would result in no access control!
++        m_display = QStringLiteral(":0");
++        if(!addCookie(m_authPath)) {
++            qCritical() << "Failed to write xauth file";
++            return false;
++        }
++
+         if (daemonApp->testing()) {
+             QStringList args;
+             QDir x11socketDir(QStringLiteral("/tmp/.X11-unix"));
+@@ -217,8 +226,14 @@ namespace SDDM {
+             emit started();
+         }
+ 
+-        // generate auth file
+-        addCookie(m_authPath);
++        // The file is also used by the greeter, which does care about the
++        // display number. Write the proper entry, if it's different.
++        if(m_display != QStringLiteral(":0")) {
++            if(!addCookie(m_authPath)) {
++                qCritical() << "Failed to write xauth file";
++                return false;
++            }
++        }
+         changeOwner(m_authPath);
+ 
+         // set flag
+diff --git a/src/daemon/XorgDisplayServer.h b/src/daemon/XorgDisplayServer.h
+index d2bdf6d4..e97a0b53 100644
+--- a/src/daemon/XorgDisplayServer.h
++++ b/src/daemon/XorgDisplayServer.h
+@@ -40,7 +40,7 @@ namespace SDDM {
+ 
+         const QString &cookie() const;
+ 
+-        void addCookie(const QString &file);
++        bool addCookie(const QString &file);
+ 
+     public slots:
+         bool start();