1 #!/usr/local/plan9/bin/rc
2 rfork n
3 
4 . 9.rc
5 
6 # exit status matching:
7 #
8 #	$discard - is really bad, refuse the message 
9 #	$accept - is really good, leave attachment alone
10 #	anything else - rewrite attachment to have .suspect extension
11 # 
12 
13 # magic exit statuses known to vf
14 accept=10
15 discard=13
16 
17 wrap=123	# anything but 10, 13
18 
19 if(! ~ $#* 1){
20 	echo usage: validateattachment mboxfile >[1=2]
21 	exit usage
22 }
23 
24 # some idiot virus is sending around attachments marked as .zip
25 # that are completely bogus and just say %TS_ZIP_ATTACH%
26 # as the base64 encoding of the zip file.  gmail rejects all zip
27 # attachments when we forward them, so nip this one here.
28 if(grep -s '^%TS_ZIP_ATTACH%$' $1 && ~ `{wc -l <$1} 1 2 3 4 5 6 7 8 9 10){
29 	echo bogus zip file!
30 	exit $discard
31 }
32 
33 upas/unvf < $1 >$1.unvf
34 file=$1.unvf
35 fn sigexit { rm $file }
36 
37 fn save {
38 #	d=`{date -n}
39 #	cp $file /n/other/upas/tmp/$d.$1
40 #	cp raw /n/other/upas/tmp/$d.$1.raw
41 #	whatis x >/n/other/upas/tmp/$d.$1.file
42 }
43 
44 x=`{file <$file | sed s/stdin://}
45 x=$"x
46 switch($x){
47 case *Ascii* *text* *'c program'* *'rc executable'* 
48 	save accept
49 	exit $accept
50 
51 case *'zip archive'*
52 	
53 	# >[2=1] because sometimes we get zip files we can't parse
54 	# but the errors look like
55 	# unzip: reading data for philw.doc.scr failed: ...
56 	# so we can still catch these.
57 	if(! unzip -tsf $file >[2=1] >/dev/null){
58 		echo corrupt zip file!
59 		exit $discard
60 	}
61 	if(unzip -tsf $file >[2=1] | grep -si '      |\.(scr|exe|pif|bat|com)$'){
62 		echo executables inside zip file!
63 		exit $discard
64 	}
65 
66 case jpeg 'PNG image' bmp 'GIF image' *'plan 9 image'
67 	save accept
68 	exit $accept
69 
70 case *Microsoft* *Office*
71 	save wrap
72 	exit $wrap
73 
74 case *MSDOS*
75 	# no executables
76 	echo $x
77 	exit $discard
78 }
79 
80 save wrap
81 exit $wrap
82 
83