Re: Backscattering

[Joerg Backschues <jbacksch-qmail@xxxxxxxxx>]

Arvind Singh wrote:

>  I was trying to implement the BATV patch given by John Levine,
> http://mipassoc.org/pipermail/batv-tech/2007q4/000032.html . The emails are
> getting signed with this patch But while the bounce mails come to MX the
> signature is not matching due to which the address is not stripped with the
> BATV tag. 

The qmail BATV patch from John is a little bit "buggy":

First of all qmail-remote uses the old syntax to sign senders:

tag-type "=" loc-core "=" tag-val

The recent syntax from "draft-levine-batv-03.txt" is:

tag-type "=" tag-val "=" loc-core

This are my qmail-remote modifications for BATV with the recent syntax 
from "draft-levine-batv-03.txt":

stralloc newsender = {0};

signenv()
  {
    int daynumber = (now() / 86400) % 1000;
    int i, atpos;
    char kdate[] = "0000";
    static char hex[] = "0123456789abcdef";
    MD5_CTX md5;
    unsigned char md5digest[MD5_DIGEST_LENGTH];

    if(stralloc_starts(&sender, "prvs=")) return; /* already signed */
    if(stralloc_starts(&sender, "sb*-")) { /* don't sign this */
      sender.len -= 4;
      byte_copy(sender.s, sender.len, sender.s+4);
      return;
    }

    if(!stralloc_ready(&newsender, sender.len+(2*BATVLEN+10))) 
temp_nomem();
    if(!stralloc_copyb(&newsender, "prvs=", 5))  temp_nomem();

    /* only one key so far */
    kdate[1] = '0' + daynumber/100;
    kdate[2] = '0' + (daynumber/10)%10;
    kdate[3] = '0' + daynumber%10;

    if(!stralloc_catb(&newsender, kdate, 4))  temp_nomem();

    MD5_Init(&md5);
    MD5_Update(&md5, kdate, 4);
    MD5_Update(&md5, sender.s, sender.len);
    MD5_Update(&md5, signkey.s, signkey.len);
    MD5_Final(md5digest, &md5);

    for(i = 0; i < BATVLEN; i++) {
      char md5hex[2];

      md5hex[0] = hex[md5digest[i]>>4];
      md5hex[1] = hex[md5digest[i]&15];
      if(!stralloc_catb(&newsender, md5hex, 2))  temp_nomem();
    }

    /*  separator */
    if(!stralloc_catb(&newsender, "=", 1)) temp_nomem();

    /* copy in the mailbox */
    if(!stralloc_0(&sender)) temp_nomem();
    sender.len--;                       /* null isn't part of of the 
sender */
    atpos = str_rchr(sender.s, '@');
    if(!stralloc_catb(&newsender, sender.s, atpos)) temp_nomem();

    if(!stralloc_catb(&newsender, sender.s+atpos, sender.len-atpos)) 
temp_nomem();
    if(!stralloc_copy(&sender, &newsender))  temp_nomem();
    if(!stralloc_copys(&newsender, ""))  temp_nomem();
 }

> But when it comes inside its batv  tag donât get stripped I checked the code
> its failing on byte compare.

The BATV checker of qmail-smtpd uses the very old syntax with "/":

local-part= tag-type "=" loc-core "/" tag-val

The modifications for qmail-smtpd are not ready yet.
I'm working on it.

Please consider:
<http://mipassoc.org/pipermail/batv-tech/2008q2/000045.html>
<http://mipassoc.org/pipermail/batv-tech/2008q2/000049.html>

--
Greetings
JÃrg Backschues