filter, list, deliver, token, vf - filtering mail
upas/filter [ -bh ] rcvr mailbox [ regexp file ] ...
upas/list [ -d ] add|check patternfile addressfile ...
upas/deliver recipient fromfile mbox
upas/token key [ tokenfile ]
upas/vf [ -r ] [ -s savefile ]
A user may filter all incoming mail by creating a world readable/exe‐
cutable file /mail/box/username/pipeto. If the file is a shell script,
it can use the commands described here to implement a filter.
Filter provides simple mail filtering. The first two arguments are the
recipient's address and mailbox, that is, the same arguments provided
to pipeto. The remaining arguments are all pairs of a regular expres‐
sion and a file name. With no flags, the sender's address is matched
against each regular expression starting with the first. If the
expression matches, then the message is delivered to the file whose
name follows the expression. The file must be world writable and
should be append only. A message that matches none of the expressions
is delivered into the user's standard mail box.
By default, filter matches each regular expression against the mes‐
sage's sender. The -h flag causes filter to match against the entire
header, and the -b flag causes filter to match against the entire mes‐
sage (header and body).
For example, to delete any messages of precedence bulk, place in your
/bin/upas/filter -h $1 $2 'Precedence: bulk' /dev/null
Three other commands exist which, combined by an rc(1) script, allow
you to build your own filter.
List takes two verbs; check and add. Check directs list to check each
address contained in the addressfiles against a list of patterns in
patternfile. Patterns come in four forms:
If any address matches the regular expression, list returns suc‐
If any address exactly matches string, list returns success‐
If any address matches the regular expression and no other
address matches a non `!' rule, list returns error status
If any address exactly matches string and no other address
matches a non `!' rule, list returns error status "!match".
If no addresses match a pattern, list returns "no match".
The pattern file may also contain lines of the form
to allow pattern files to include other pattern files. All pattern
matches are case insensitive. List searches the pattern file (and its
includes) in order. The first matching pattern determines the action.
List add directs list to add a pattern to patternfile for each address
in the addressfiles that doesh't already match a pattern.
Token, with only one argument, prints to standard output a unique token
created from the current date and key. With two arguments, it checks
token against tokens created over the last 10 days with key. If a
match is found, it returns successfully.
Deliver delivers into mail box mbox the message read from standard
input. It obeys standard mail file locking and logging conventions.
/sys/src/cmd/upas/filterkit/pipeto.sample is a sample pipeto using the
A sample pipefrom, /sys/src/cmd/upas/filterkit/pipefrom.sample, is pro‐
vided which adds all addresses of your outgoing mail to your pattern
file. You should copy it into a directory that normally gets bound by
your profile onto /bin.
Vf (virus filter) takes a mail message as standard input and searches
for executable MIME attachments, either rewriting them to be non-exe‐
cutable or rejecting the message. The behavior depends on the attach‐
ment's file name extension and MIME content type. /sys/lib/mimetype
contains the list of known extensions and MIME content types. The
fifth field of each line specifies the safety of a particular file
type: y (yes), m (maybe; treated same as yes), n (no), p (previous), or
r (reject). Vf allows attachments with safety y or m to pass through
unaltered. Attachments with safety n both are wrapped in extra MIME
headers and have .suspect appended to their file names, to avoid auto‐
matic execution by mail readers. Attachments with safety r (currently,
.bat, .com, .exe, and .scr, all Microsoft executable extensions) are
taken as cause for the entire message to be rejected. A safety of p
(used for the x-gunzip mime type) causes the previous extension to be
tested, so that x.tar.gz is treated the same as x.tar.
If /mail/lib/validateattachment exists and is executable, vf runs it on
all attachments with safety n (attachments it would normally sanitize).
If validateattachment's exit status contains the string vf rejects the
entire message. If the status contains the string vf does not sanitize
the attachment. Otherwise, vf sanitizes the attachment as before. The
standard validateattachment uses file(1) to determine the file type.
It accepts text and image files and discards messages containing exe‐
cutables or zip (see gzip(1)) archives of executables.
The -r option causes vf not to sanitize MIME attachments, but instead
to reject messages it determines to be viruses. The -s option causes
vf to log all attachments of safety r in the mail box savefile.
MIME content types
SEE ALSOaliasmail(8), faces(1), mail(1), marshal(1), mlmgr(1), nedmail(1),
qer(8), rewrite(6), send(8), smtp(8), upasfs(4)FILTER(1)