Hi Fellow Monks, After spending the last few weeks developing a client/server to handle requests for my program I have covered both encryption and message integrity via CBC::Blowfish_PP and Digex::MD5. This seems to work very well for client command that only require one response from the server, such as a true or false. However, one of the functions I am now trying to complete is one that enables the server to send several responses to one query via an array. I run into trouble when I have the client verify the integrity of the responses - it seems that when one does not match and the client requests a resend the resend works as it should, but the next response that gets received by the client is a duplicate of the one that was originally sent even though debug on the server shows that the correct response is being sent. I can only figure this is a problem with STDIO buffering the input from the server on the client-side and what I would like to do is once the client verifies the servers md5 checksum reset the STDIN if possible. If not possible, does anyone know a better way to do what I want? The code for the server follows: 
      foreach $confline (@domconf) {
       chomp($confline);
       my $resend2 = "no";
       my $waitforok2 = "yes";
       while ($waitforok2 eq "yes") {
        my $checkhash2 = GenerateMD5("confline: $confline");
        if (defined($resend2) && $resend2 eq "yes") {
         print "$verify - Rebuilding Encryption Table: ";
         $cipher = new Crypt::CBC("$verify", 'Blowfish_PP');
        }
        my $response2 = $cipher->encrypt("confline: $confline");
        print $client "$checkhash2 $response2\n";
        ($waitforok2, $resend2) = FinishUp2($client);
       }
      }

[download]
FinishUp2 is a function that receives either "OK" or "Resend" from the client...if OK it returns "no, no" and if Resend it returns "yes, no". Now here is the client code: 
UNF: while ($waitforit eq "yes") {
  $cipher = new Crypt::CBC("$cipherkey", 'Blowfish_PP');
  $ciphertext = $cipher->encrypt("$msg");
  $hash = GenerateMD5("$msg");
  print $client "$hash $ciphertext\n";
  my ($argh)  =0;
  while (<$client>) {
   my ($line) = $_;
   chomp($line);
   $argh++;
   if ($line =~ /Resend/) { next UNF; $resend = "yes";}
   $inhash = substr($line, 0, 32);
   $encrypted = substr($line, 33, length($_)-33);
   $plaintext = $cipher->decrypt($encrypted);
   $checkhash = GenerateMD5($plaintext);
   if ($inhash eq $checkhash) {
    if ($plaintext =~ /!!beginresponse/) { print $client "OK\n"; @data
+=(); next; }
    if ($plaintext =~ /!!endresponse/) { print
$client "Finished\n"; print "Number: $argh\n"; return
@data; }
    if ($plaintext =~ /confline:\s+(.*)/) {
     print $client "OK\n"; push(@data, $1);
    }
   }
   else {
    $plaintext = ""; $inhash=""; $encrypted=""; $checkhash="";
    print $client "Resend\n";
   }
  }
 }

[download]
Let me know if you need any other info - I'll be glad to post it. -Adam Stanley Nethosters, Inc.

In reply to problems with STDIO buffer? by astanley

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.