[DRE-maint] Bug#557043: libpcap-ruby1.8: /usr/lib/ruby/1.8/pcaplet.rb:77:in `=~': wrong type Regexp (expected Pcap::Packet) (TypeError)

[Clinton Gower]

Package: libpcap-ruby1.8
Version: 0.6-9.1
Severity: normal


Attempting to add two Filter objects to a Pcaplet object produces the error.

I have included sample code that will reproduce the error, along with a patch to 
/usr/lib/ruby/1.8/pcaplet.rb that seems to resolve the issue.

Simple code sample that reproduces the error:

        #!/usr/bin/ruby
        require 'pcaplet'

        network = Pcaplet.new

        # The first add_filter works correctly, but adding the second filter produces the error.
        network.add_filter(Pcap::Filter.new('src net 192.168.0.0/24', network.capture))
        network.add_filter(Pcap::Filter.new('dst port 80', network.capture))

        network.close

        exit(0)

Line 77 in pcaplet.rb uses a regular expression to check to see if @filter an empty string.

If @filter is empty, then it is set to f.  If f was a Filter object, then when =~ is
used on @filter in the next add_filter call, it expects a Packet to come after the =~ 
operator and fails.

The solution I found is to sanitize the f variable and make sure it is a string before
it gets assigned to initialize the @filter variable.  This is done by moving line 80 up, 
to before the if statement on line 77.

The patch I used on the /usr/lib/ruby/1.8/pcaplet.rb file is as follows:
76a77
>       f = f.source if f.is_a? Filter
80d80
<       f = f.source if f.is_a? Filter

After applying the patch, both Filter objects are successfully added without error.

Regards,

Clinton Gower

-- System Information:
Debian Release: sid
  APT prefers transitional
  APT policy: (500, 'transitional'), (500, 'unstable')
Architecture: amd64 (x86_64)

Kernel: Linux 2.6.31-1-amd64 (SMP w/1 CPU core)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages libpcap-ruby1.8 depends on:
ii  libc6                        2.10.1-5    GNU C Library: Shared libraries
ii  libpcap0.8                   1.0.0-4     system interface for user-level pa
ii  libruby1.8                   1.8.7.174-2 Libraries necessary to run Ruby 1.

Versions of packages libpcap-ruby1.8 recommends:
ii  libpcap-ruby                  0.6-9.1    Ruby interface for the libpcap pac

libpcap-ruby1.8 suggests no packages.

-- no debconf information