Re: [bug-patch] [PATCH] do not let a malicious patch create files above current directory

[Jim Meyering]

Jim Meyering wrote:
> Surprised that no one has posted a patch for this yet, I wrote my own:
>
>>From aeed44154b388210f0e70dbe802a78949224aa97 Mon Sep 17 00:00:00 2001
> From: Jim Meyering <address@hidden>
> Date: Tue, 1 Feb 2011 11:21:15 +0100
> Subject: [PATCH] do not let a malicious patch create files above current 
> directory
>
> This addresses CVE-2010-4651, reported by Jakub Wilk.
> https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2010-4651
> * src/pch.c (intuit_diff_type): Reject any file name containing a
> component of "..".
> * tests/dot-dot: New file.  Test for this.
> * tests/Makefile.am (TESTS): Add it.

That patch did not go far enough in that it still permitted
absolute output file names, at least with -p0.  I must have
tested only with -p1.

This improves on the preceding in a couple ways:
  - now rejects *before* prompting about an invalid name at the expense
      of also testing from "maybe_reverse".  It looks like it would be
      too invasive to try to defer the two calls to that function
      until after inname is set.
  - added a test case with an absolute name
  - fixed the comment at the top of the test script

Also, it changes the diagnostic to be more general,
so that the same diagnostic applies to both cases.


>From ccf76efc15978399de01710502a1b153b87b73eb Mon Sep 17 00:00:00 2001
From: Jim Meyering <address@hidden>
Date: Tue, 1 Feb 2011 11:21:15 +0100
Subject: [PATCH] do not let a malicious patch create files above current 
directory

This addresses CVE-2010-4651, reported by Jakub Wilk.
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2010-4651
With this change, patch rejects any output file name that
is absolute or that contains a ".." component.
* src/pch.c (file_name_contains_dot_dot): New function.
(invalid_file_name): New function.
(maybe_reverse): Don't prompt about an invalid file name.
(intuit_diff_type): Reject any file name containing a
component of "..".
* tests/dot-dot: New file.  Test for this.
* tests/Makefile.am (TESTS): Add it.
---
 ChangeLog         |   12 +++++++++++-
 src/pch.c         |   31 ++++++++++++++++++++++++++++++-
 tests/Makefile.am |    3 ++-
 tests/dot-dot     |   50 ++++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 93 insertions(+), 3 deletions(-)
 create mode 100644 tests/dot-dot

diff --git a/ChangeLog b/ChangeLog
index bbe5fe7..88db61c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+2011-02-01  Jim Meyering  <address@hidden>
+
+       do not let a malicious patch create files above current directory
+       This addresses CVE-2010-4651, reported by Jakub Wilk.
+       https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2010-4651
+       * src/pch.c (intuit_diff_type): Reject any file name containing a
+       component of "..".
+       * tests/dot-dot: New file.  Test for this.
+       * tests/Makefile.am (TESTS): Add it.
+
 2010-12-04  Andreas Gruenbacher <address@hidden>

        * src/util.c (make_tempfile): Create missing directories when
@@ -3594,7 +3604,7 @@ Sun Dec 17 17:29:48 1989  Jim Kingdon  (kingdon at 
hobbes.ai.mit.edu)
 Copyright (C) 1984, 1985, 1986, 1987, 1988 Larry Wall.

 Copyright (C) 1989, 1990, 1991, 1992, 1993, 1997, 1998, 1999, 2000, 2001,
-2002, 2009, 2010 Free Software Foundation, Inc.
+2002, 2009, 2010, 2011 Free Software Foundation, Inc.

 This file is part of GNU Patch.

diff --git a/src/pch.c b/src/pch.c
index 1653ee4..60a660c 100644
--- a/src/pch.c
+++ b/src/pch.c
@@ -3,7 +3,7 @@
 /* Copyright (C) 1986, 1987, 1988 Larry Wall

    Copyright (C) 1990, 1991, 1992, 1993, 1997, 1998, 1999, 2000, 2001,
-   2002, 2003, 2006, 2009, 2010 Free Software Foundation, Inc.
+   2002, 2003, 2006, 2009, 2010, 2011 Free Software Foundation, Inc.

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -193,11 +193,37 @@ grow_hunkmax (void)
     return false;
 }

+/* Return true if NAME contains a ".." component.  */
+
+static bool
+file_name_contains_dot_dot (char const *name)
+{
+  size_t len = strlen (name);
+  return (len >= 3
+         && (strnEQ (name, "../", 3)
+             || strnEQ (name + len - 3, "/..", 3)
+             || strstr (name, "/../")));
+}
+
+/* A file name, NAME, is invalid if it is absolute or if
+   it contains a ".." component.  */
+
+static bool
+invalid_file_name (char const *name)
+{
+  return (IS_ABSOLUTE_FILE_NAME (name)
+         || file_name_contains_dot_dot (name));
+}
+
 static bool
 maybe_reverse (char const *name, bool nonexistent, bool is_empty)
 {
   bool looks_reversed = (! is_empty) < p_says_nonexistent[reverse ^ is_empty];

+  /* If it's a name that we'll reject, don't bother prompting.  */
+  if (invalid_file_name (name))
+    return false;
+
   /* Allow to create and delete empty files when we know that they are empty:
      in the "diff --git" format, we know that from the index header.  */
   if (is_empty
@@ -935,6 +961,9 @@ intuit_diff_type (bool need_header, mode_t *p_file_type)
        instat = st[i];
       }

+    if (inname && invalid_file_name (inname))
+      fatal ("invalid output file name: %s", quotearg (inname));
+
     return retval;
 }

diff --git a/tests/Makefile.am b/tests/Makefile.am
index ffe02af..69d8ea1 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -1,5 +1,5 @@
 # Copyright (C) 1989, 1990, 1991, 1992, 1993, 1997, 1998, 1999, 2002,
-# 2003, 2006, 2009, 2010 Free Software Foundation, Inc.
+# 2003, 2006, 2009, 2010, 2011 Free Software Foundation, Inc.

 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -24,6 +24,7 @@ TESTS = \
        create-delete \
        criss-cross \
        crlf-handling \
+       dot-dot \
        dash-o-append \
        empty-files \
        file-modes \
diff --git a/tests/dot-dot b/tests/dot-dot
new file mode 100644
index 0000000..b868a0c
--- /dev/null
+++ b/tests/dot-dot
@@ -0,0 +1,50 @@
+# Copyright (C) 2011 Free Software Foundation, Inc.
+#
+# Copying and distribution of this file, with or without modification,
+# in any medium, are permitted without royalty provided the copyright
+# notice and this notice are preserved.
+
+# Reject an output file name that is absolute or that contains a ".." 
component.
+
+. $srcdir/test-lib.sh
+
+require_cat
+use_local_patch
+use_tmpdir
+
+# ==============================================================
+
+emit_patch()
+{
+cat <<EOF
+--- /dev/null
++++ $1
+@@ -0,0 +1 @@
++x
+EOF
+}
+
+check 'emit_patch /tmp/x | patch -p0; echo status: $?' <<EOF
+$PATCH: **** invalid output file name: /tmp/x
+status: 2
+EOF
+
+check 'emit_patch a/../z | patch -p0; echo status: $?' <<EOF
+$PATCH: **** invalid output file name: a/../z
+status: 2
+EOF
+
+check 'emit_patch a/../z | patch -p1; echo status: $?' <<EOF
+$PATCH: **** invalid output file name: ../z
+status: 2
+EOF
+
+check 'emit_patch a/.. | patch -p0; echo status: $?' <<EOF
+$PATCH: **** invalid output file name: a/..
+status: 2
+EOF
+
+check 'emit_patch ../z | patch -p0; echo status: $?' <<EOF
+$PATCH: **** invalid output file name: ../z
+status: 2
+EOF
--
1.7.3.5.44.g960a