From ed8b418f1341cf7fc576f6b17de5c6dd4017e034 Mon Sep 17 00:00:00 2001
From: "Jeremy A. Puhlman" <jpuhlman@mvista.com>
Date: Thu, 27 Jan 2022 00:01:27 +0000
Subject: [PATCH] CVE-2021-4034: Local privilege escalation in pkexec due to 
 incorrect handling of argument vector

Upstream-Status: Backport https://gitlab.freedesktop.org/polkit/polkit/-/commit/a2bf5c9c83b6ae46cbd5c779d3055bff81ded683
CVE: CVE-2021-4034

Signed-off-by: Jeremy A. Puhlman <jpuhlman@mvista.com>
---
 src/programs/pkcheck.c |  6 ++++++
 src/programs/pkexec.c  | 21 ++++++++++++++++++++-
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/src/programs/pkcheck.c b/src/programs/pkcheck.c
index f1bb4e1..aff4f60 100644
--- a/src/programs/pkcheck.c
+++ b/src/programs/pkcheck.c
@@ -363,6 +363,12 @@ main (int argc, char *argv[])
   local_agent_handle = NULL;
   ret = 126;
 
+  if (argc < 1)
+    {
+      help();
+      exit(1);
+    }
+
   /* Disable remote file access from GIO. */
   setenv ("GIO_USE_VFS", "local", 1);
 
diff --git a/src/programs/pkexec.c b/src/programs/pkexec.c
index 7698c5c..3ff4c58 100644
--- a/src/programs/pkexec.c
+++ b/src/programs/pkexec.c
@@ -488,6 +488,17 @@ main (int argc, char *argv[])
   pid_t pid_of_caller;
   gpointer local_agent_handle;
 
+
+  /*
+   * If 'pkexec' is called wrong, just show help and bail out.
+   */
+  if (argc<1)
+    {
+      clearenv();
+      usage(argc, argv);
+      exit(1);
+    }
+
   ret = 127;
   authority = NULL;
   subject = NULL;
@@ -636,7 +647,15 @@ main (int argc, char *argv[])
           goto out;
         }
       g_free (path);
-      argv[n] = path = s;
+      path = s;
+
+      /* argc<2 and pkexec runs just shell, argv is guaranteed to be null-terminated.
+       * /-less shell shouldn't happen, but let's be defensive and don't write to null-termination
+       */
+      if (argv[n] != NULL)
+      {
+        argv[n] = path;
+      }
     }
   if (access (path, F_OK) != 0)
     {
-- 
2.26.2