Fix for temporary file security whole

We create temporary files in /tmp/ with predictable names.  These
could be used by an attacker to DoS a box by setting a symlink to
some other file (say, /etc/shadow) and waiting for us to overwrite
it.

The minimalistic solution employed by this patch is to wrap all such
file writing with a paranoid wrapper that:

1) Check to see if the target exists
2) Issues a warning if it was a symlink
3) Deletes it
4) Waits (0.1 seconds if it was a file, 5 seconds if it was a symlink)
5) Opens the file with EXCL, which will fail if the file has come back.

If this succeeds (as it normally will) it has exactly the same semantics
as the original code (a must, as we are right at a release boundary).
However, under no circumstances will it follow a preexisting symlink (the
operating system guarantees this with EXCL) so the danger of an exploit
has been converted into the possibility of a failure, with an appropriate
warning.

1 files changed, 6 insertions, 3 deletions

diff --git a/lib/puppet/util/reference.rb b/lib/puppet/util/reference.rb
index 7526e6566..93542df28 100644
--- a/lib/puppet/util/reference.rb
+++ b/lib/puppet/util/reference.rb
@@ -36,7 +36,7 @@ class Puppet::Util::Reference
 
     def self.pdf(text)
         puts "creating pdf"
-        File.open("/tmp/puppetdoc.txt", "w") do |f|
+        Puppet::Util.secure_open("/tmp/puppetdoc.txt", "w") do |f|
             f.puts text
         end
         rst2latex = %x{which rst2latex}
@@ -48,6 +48,9 @@ class Puppet::Util::Reference
         end
         rst2latex.chomp!
         cmd = %{#{rst2latex} /tmp/puppetdoc.txt > /tmp/puppetdoc.tex}
+        Puppet::Util.secure_open("/tmp/puppetdoc.tex","w") do |f|
+            # If we get here without an error, /tmp/puppetdoc.tex isn't a tricky cracker's symlink
+        end
         output = %x{#{cmd}}
         unless $? == 0
             $stderr.puts "rst2latex failed"
@@ -67,7 +70,7 @@ class Puppet::Util::Reference
         puts "Creating markdown for #{name} reference."
         dir = "/tmp/" + Puppet::PUPPETVERSION
         FileUtils.mkdir(dir) unless File.directory?(dir) 
-        File.open(dir + "/" + "#{name}.rst", "w") do |f|
+        Puppet::Util.secure_open(dir + "/" + "#{name}.rst", "w") do |f|
             f.puts text
         end
         pandoc = %x{which pandoc}
@@ -190,7 +193,7 @@ class Puppet::Util::Reference
     end
 
     def trac
-        File.open("/tmp/puppetdoc.txt", "w") do |f|
+        Puppet::Util.secure_open("/tmp/puppetdoc.txt", "w") do |f|
             f.puts self.to_trac
         end