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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Perhaps this initial email should have
said “validation would probably be much simpler” rather than “validation
would be much simpler”. </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>I’m having a go at performing the
validation using the one-byte string-length prefix to see how much it helps. I’ll
report back later today…</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Tim</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
sis-ams-bounces@mailman.ccsds.org [mailto:sis-ams-bounces@mailman.ccsds.org] <b><span
style='font-weight:bold'>On Behalf Of </span></b>Ray, Timothy J. (GSFC-583.0)<br>
<b><span style='font-weight:bold'>Sent:</span></b> Wednesday, June 25, 2008
11:04 AM<br>
<b><span style='font-weight:bold'>To:</span></b> sis-ams@mailman.ccsds.org<br>
<b><span style='font-weight:bold'>Subject:</span></b> [Sis-ams] validation of
Meta-AMS PDUs</span></font></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Dear WG Members,</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>In my implementation, I am trying to thoroughly validate
each incoming Meta-AMS protocol message (MPDU). The primary goal is to
avoid program crashes that can occur when an attempt is made to access an array
element beyond the end of the array’s allocated memory. For
example, if the supplementary data includes a field that is supposed to be a
null-terminated character string, but the null-terminator is missing, avoid any
attempts to access past the end of the entire array allocated to hold the raw
MPDU bytes.</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>I’m finding it quite complex to validate MPDUs whose
supplementary data includes null-terminated strings (especially if the strings
are buried within arrays of structures containing sub-structures). Validation
would be much simpler if, instead of adding a one-byte null terminator at the
end of each string, we added a one-byte length field at the beginning of each
string. (It would also be possible to add the one-byte length field and
keep the null terminator, although that seems redundant).</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Any thoughts/comments?</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Tim</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
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