Re: Perl syswrite and IO/SSL

On May 21, 2009, at 11:50 AM, Dale Moore wrote:

> Hi Graham,
>
> I believe that I've figured out this problem
> with syswrite returning 1 instead of the number of
> bytes actually written.
>
> The problem appears to be with Authen::SASL::Cyrus .

Unfortunately there are 2 different Authen::SASL::Cyrus
modules :-(, but I think you are using the one by Patrick Boettcher

As Patrick does not own the namespace his module is not easily found.

However, with his permission, I have created a rename of that module
and it is available on github at

http://github.com/gbarr/perl-authen-sasl-xs/tree

> In that module, they supply their own WRITE function
> in Authen::SASL::Cyrus::Security .  This WRITE function
> is called when syswrite is called with an LDAP connection
> that has been authenticated with Cyrus SASL.
>
> This WRITE function does not implement the standard
> syswrite semantics.  It's implementation is
> sub WRITE {
>  my($ref,$string,$len) = @_;
>  my($fh, $clearbuf, $cryptbuf);
>
>  $fh = $ref->{fh};
>  $clearbuf = substr($string, 0, $len);
>  $cryptbuf = $ref->{conn}->encode($clearbuf);
>  print $fh $cryptbuf;
> }

Yes that looks the same as

http://github.com/gbarr/perl-authen-sasl-xs/blob/91fb5bf011d3e6a345c6996141af71f563982040/lib/Authen/SASL/XS/Security.pm#L74

Authen::SASL needs to be modified to look for ::XS by default, but you  
can make it find it with

use Authen::SASL qw(XS Perl);

Any patches to Authen::SASL::XS would be welcome.

Graham.

> It does not handle offsets, and print returns
> TRUE on success (what I was seeing), and not the
> number of bytes.  This is a bug in Authen::SASL::Cyrus .
>
> If I avoid Cyrus Sasl, and use Perl SASL all is well
> and the problem does not persist.
>
> I appreciate your help in resolving this problem.
>
> Dale Moore
>
> -----Original Message-----
> From: Graham Barr [mailto:[email protected]]
> Sent: Tuesday, May 19, 2009 4:27 PM
> To: [email protected]
> Cc: [email protected]
> Subject: Re: Perl syswrite and IO/SSL
>
> On May 19, 2009, at 2:31 PM, Dale Moore wrote:
>> I am having a problem with LDAP.pm and wondering
>> if any other folks are experiencing similar problems.
>>
>> The problems are the result of code that was modified
>> in this patch
>>
>> http://git.goingon.net/?p=perl-ldap.git;a=commitdiff;h=8c6c9cfcb78adf229437507f2e8ffe86d15e712d
>>
>> There are some style issues that I don’t like about this patch.
>> - We do a length() call on each time through the loop rather than
>> once
>> - We do a substr call each time through the loop, which isnt
>> necessary
>>   if we would instead use the offset parameter to syswrite
>> - No reference in where the number 15000 came from.
>>
>> But the patch appears to basically sound, even if it does offend my
>> sense
>> of asthetics.
>
> Patches welcome.
>
>> The only problem I am having is that after a successful
>> bind and several passes through this code, it starts to misbehave.
>> The calls to syswrite return the value 1 instead of the number of
>> bytes
>> in the buffer as I might have expected.
>>
>> The problem is
>> - The call to syswrite() of a buffer of several hundred bytes
>> always returns 1
>>   and not the number of the several hundred bytes as expected.
>>   This causes the syswrite to be retried with a slightly smaller
>> buffer.
>>   The remote server appears to receive the original request, and
>> responds
>>   but subsequent writes of the smaller buffer confuse it and it
>> drops the connection.
>> - A system call trace of perl process reveals that it is calling
>> write()
>>   with several hundred bytes, and it is succeeding in writing all
>> of the bytes,
>>   NOT just 1 or a smaller number of bytes...
>
> Do you have the latest Net::SSLeay and IO::Socket::SSL installed ?
>
> When using SSL, the syswrite is effectively a call to
> Net::SSLeay::write_partial
>
>> I've tried judicious use of 'use bytes;' and a few other common
>> tricks.
>
> use bytes would not make a difference here.
>
>> If you'll look at the previous version, before this patch, you'll
>> see where
>> we only looked to see if syswrite returned zero or non-zero.  Not
>> the actual
>> number of bytes.
>
> Which was a bug as syswrite does not guarantee to send all the data
>
> Graham.
>
>> If I tweak my private copy of LDAP.pm to assume that
>> syswrite returned what I was expecting, it works as expected, and
>> the client
>> and server successfully communicate for as long as expected.
>>
>> I've seen this problem with Perl 5.8.8 on Solaris 9, 10, and 32Bit
>> i386 Redhat Fc5.
>> If you've seen this problem, or similar problems, or have a strong
>> clue
>> as to what might be wrong, I'd appreciate your comments.
>>
>> Comments welcome,
>>
>>
>
>
>