[lkml]   [1999]   [Feb]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: PPP bug
    >>>>> "Dick" == Richard B Johnson <> writes:

    Dick> The +++ sequence in a packet can't affect the modem because
    Dick> you need at least 500ms (lowest you can set it) of quiet after
    Dick> the sequence to change its mode. The data strings will never
    Dick> be the last thing sent, so you can't get 500ms between
    Dick> characters no matter how hard you try.

    This is partially true. Unfortunately (I believe) Hayes patented the
    idea of there having to be a pause before and after the +++ sequence,
    and some manufacturers (namely Rockwell) simply look for any +++
    sequence as a break sequence regardless of timing. Experience is that
    roughly 40% of people on IRC are susceptible to this problem, so these
    modems are fairly wide-spread. To test a host (with permission,
    of-course:) use:

    % ping -p 2b2b2b415448300d <hostname>

    If it replies, the host is fine. If it doesn't, it's got a faulty
    modem. This was all covered in depth a while back on the Bugtraq
    mailing lists (search the geek-girl archives... I think "Old school
    DoS" was the subject). The only solution if you've got one of these
    modems is to change break character from + to something else, or
    (preferably) disable it entirely with AT S2=255. An interesting
    side-effect of the bug is that you can "patch" people's modems for
    them if they're buggy with something like (untested):

    % ping -p 2b2b2b415453323d323535204f300d

    - Andrew
    #!/usr/bin/env python
    print(lambda s:s+"("+`s`+")")\
    ('#!/usr/bin/env python\012print(lambda s:s+"("+`s`+")")\\\012')
    print(lambda x:x%`x`)('print(lambda x:x%%`x`)(%s)')
    [unhandled content-type:application/pgp-signature]
     \ /
      Last update: 2005-03-22 13:50    [W:0.021 / U:30.416 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site