Strange encoding of attachment filname

[Ralf Hildebrandt]

Today a user reported that he received a mail without attachment.

Turns out that there *IS* an attachment, but it's strangely named.

Looking at the raw mail we find:

MIME-Version: 1.0
Content-Type: multipart/mixed;
        boundary="=_v1cFiJlk+hCgpTYQg6SrNjzrUErl8abdUWfJ88KLUInW8C9C"

...
--=_v1cFiJlk+hCgpTYQg6SrNjzrUErl8abdUWfJ88KLUInW8C9C
Content-Type: application/pdf; name*0*=
        "iso-8859-1"%41%6E%66%6F%72%64%65%72%75%6E%67%65%6E%5F%53%7A%31%5F%53";
        name*1*="%7A%32%2E%70%64%66"
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
	filename*0*="iso-8859-1"%41%6E%66%6F%72%64%65%72%75%6E%67%65%6E%5F%53%7A%31";
	filename*1*="%5F%53%7A%32%2E%70%64%66"
	
JVBERi0xLjQKJeLjz9MKMyAwIG9iago8PAovUHJvZHVjZXIgKFBERi1YQ2hhbmdlIDMuNjAu
...

If we interpret the numbers as HTML entitities, we get:
Anforderungen_Sz1_Sz2.pdf
which looks fairly normal.

Is this encoding ok? I know it's OK to encode special characters like
Umlaut characters. But all of it?

Also I have never seen this "line continuation" of the filename/name
field. Is that legit?

I've never seen this stuff before...

-- 
Ralf Hildebrandt                   Charite Universitätsmedizin Berlin
ralf.hildebrandt at charite.de        Campus Benjamin Franklin
http://www.charite.de              Hindenburgdamm 30, 12203 Berlin
Geschäftsbereich IT, Abt. Netzwerk fon: +49-30-450.570.155