From: Shawn Anderson <shawn42@...>
Date: 2010-01-13T08:57:03+09:00
Subject: Re: ffi, kerberos

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You may want to post this to the ruby-ffi mailing list.

/Shawn

On Tue, Jan 12, 2010 at 6:00 PM, Daniel Berger <djberg96@gmail.com> wrote:

>
>
> On Jan 12, 3:48 pm, Daniel Berger <djber...@gmail.com> wrote:
> > Hi,
> >
> > I'm trying to wrap two function calls from kerberos, krb5_init_context
> > and krb5_free_context. Here are the prototypes for both:
> >
> > krb5_init_context(krb5_context * context) => krb5_error_code
> > krb5_free_context(krb5_context context) => void
> >
> > krb5_context is a struct, but unfortunately I don't know what its
> > members are.
> >
> > From the docs:
> >
> >      The krb5_context structure is designed to hold all per thread
> > state. All
> >      global variables that are context specific are stored in this
> > structure,
> >      including default encryption types, credentials-cache (ticket
> > file), and
> >      default realms.
> >
> >      The internals of the structure should never be accessed directly,
> > func-
> >      tions exist for extracting information.
> >
> > All I know is that it's 8 bytes in size.
> >
> > I tried something like this, but it didn't work:
> >
> > require 'ffi'
> >
> > module Krb5
> >   class Context
> >     extend FFI::Library
> >
> >     class Error < StandardError; end
> >
> >     ffi_lib 'krb5'
> >
> >     attach_function :krb5_init_context, [:string], :uint
> >     attach_function :krb5_free_context, [:string], :void
> >
> >     def initialize
> >       @ctx = FFI::MemoryPointer.new(:pointer, 8)
> >       ret = krb5_init_context(@ctx)
> >
> >       if ret > 0
> >         raise Error, "krb5_init_context() failed"
> >       end
> >
> >       if block_given?
> >         begin
> >           yield self
> >         ensure
> >           free
> >         end
> >       end
> >     end
> >
> >     def free
> >       krb5_free_context(@ctx)
> >     end
> >   end
> > end
> >
> > k = Krb5::Context.new
> > k.free
> >
> > I can use a plain string buffer, but then it segfaults on the 'free'
> > call.
> >
> > Any suggestions?
>
> Oops, here's an updated version, but it segfaults on the 'free' call:
>
> require 'ffi'
>
> module Krb5
>  class Context
>    extend FFI::Library
>
>    class Error < StandardError; end
>
>    ffi_lib 'krb5'
>
>     attach_function :krb5_init_context, [:pointer], :uint
>    attach_function :krb5_free_context, [:pointer], :void
>
>    def initialize
>      @ctx = FFI::MemoryPointer.new(:char, 8)
>       ret = krb5_init_context(@ctx)
>
>      if ret > 0
>        raise Error, "krb5_init_context() failed"
>      end
>
>      if block_given?
>        begin
>          yield self
>        ensure
>          free
>        end
>      end
>    end
>
>    def free
>      krb5_free_context(@ctx)
>    end
>  end
> end
>
> k = Krb5::Context.new
> k.free
>
>

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