The Annoyance Filter.pdf - Fourmilab

132 MAIL FOLDER ANNOYANCE-FILTER §155
155. We have decoders for certain application file types. Check the Content−Type for types we can
decode, and if it’s indeed one we can, splice the appropriate decoder into the pipeline.
〈 Check for application file types for which we have a decoder 155 〉 ≡
#ifdef HAVE_PDF_DECODER
if (mimeContentType ≡ "application/pdf") {
asp = &aspPdf ;
}
else
#endif
if ((mimeContentType ≡ "application/x−shockwave−flash") ∨ (mimeContentType ≡
"image/vnd.rn−realflash")) {
asp = &aspFlash ;
}
if (asp ≠ Λ) {
asp ⃗ setMailFolder (this);
if (Annotate (’d’)) {
ostringstream os ;
}
}
os ≪ "Activating␣" ≪ asp ⃗ name ( ) ≪ "␣application␣file␣decoder.";
reportParserDiagnostic(os );
This code is used in section 153.
156. Certain MIME Content−Type declarations denote binary files best classified by parsing them
for ASCII strings. Test for such files and invoke the requisite decoder unless binary stream parsing has
been disabled by setting streamMinTokenLength to zero or the file is already scheduled for parsing by
an application-specific string parser.
Thanks to a hideous design error in Microsoft Outlook, mail worms can spoof the test for executable
content by declaring an attachment as an innocuous file type such an image or audio file, and then
cause it to be executed simply by specifying a file name with one of the many Microsoft executable file
extensions. We check for such spoofed attachments and pass them through the byte stream parser as
well.
〈 Detect binary parts worth parsing for embedded ASCII strings 156 〉 ≡
if ((asp ≡ Λ) ∧ (streamMinTokenLength > 0) ∧ ((mimeContentType .substr (0,
12) ≡ "application/") ∨ (((mimeContentType .substr (0,
6) ≡ "audio/") ∨ (mimeContentType .substr (0,
6) ≡ "image/")) ∧ (isSpoofedExecutableFileExtension (mimeContentTypeName ) ∨
isSpoofedExecutableFileExtension (mimeContentDispositionFilename ))))) { /∗ cout ¡¡ ”* *
* Content-type name = ¨” ¡¡ mimeContentTypeName ¡¡ ”¨” ¡¡ endl; ∗/ /∗ cout ¡¡ ”* * *
Content-Disposition filename = ¨” ¡¡ mimeContentDispositionFilename ¡¡ ”¨” ¡¡ endl; ∗/
if (Annotate (’d’)) {
ostringstream os ;
}
os ≪ "Activating␣byte␣stream␣parser␣for␣\"" ≪ mimeContentType ≪ "\"";
reportParserDiagnostic(os );
}
byteStream = true ;
This code is used in section 153.