NAME
aliascheck - check for existence of mail alias
SYNOPSIS
aliascheck [--nopwd] name [alias-file]
aliascheck --map [--case] name map-file
aliascheck --qmail [--nopwd] name [alias-user]
DESCRIPTION
aliascheck checks whether name is a valid email alias or a user in the
password file. It converts name to lower-case before performing any of
the checks. If the alias or user exists, aliascheck exits with status
0 and outputs what the address resolves to. If the alias does not
exist, aliascheck exits with status 1. If aliascheck cannot determine
the validity of name because of some system error, it exits with status
2.
aliascheck can run in three different modes--sendmail alias mode (the
default), sendmail map mode, and qmail mode. In sendmail alias mode
the second argument, alias-file, is the name of the sendmail alias
file, typically /etc/mail/aliases.db. If no second argument is
supplied, aliascheck first checks for the existence of
/etc/mail/aliases.db, then for the existence of /etc/aliases.db, then
finally exits with status 2 if neither file exists. When an alias is
found, aliascheck outputs the value of that alias in the alias
database.
When aliascheck is invoked with --map, it looks up name in map-file,
which should be a database created with sendmail’s makemap(8) utility.
Note that maps have a slightly different and incompatible format from
that of alias files. Use the --case argument to prevent name from
being folded to lower-case before it is looked up in the database.
Note that --map implies the --nopwd option.
When aliascheck is given the argument --qmail, it runs in qmail mode.
In this case, the second argument, alias-user, specifies the user under
which qmail processes mail aliases. aliascheck will check this user’s
home directory for files named .qmail-XXX for various appropriate
suffixes XXX. On success, it outputs the full pathname of the
appropriate file.
If aliascheck cannot find an alias, it also checks the password file,
and exits 0 if it can find name there. If name is found, aliascheck
also outputs name (in lower-case) to standard output before exiting.
(This is useful for Mail Avenger, because asmtpd does not recognize
users with invalid shells or UID 0, while MTAs typically do.) To
suppress password file checking, supply the --nopwd argument to
aliascheck.
EXAMPLES
If you are using Mail Avenger in conjunction with a sendmail
installation, you might want to put the following code in your
/etc/avenger/unknown file to reject mail for unknown users who do not
show up in the alias file.
aliascheck "$RECIPIENT_LOCAL" /etc/mail/aliases.db > /dev/null
case "$?" in
0)
# Fall through to default checks
;;
1)
reject unknown user
;;
*)
# Probably safest to do nothing, but could also
# defer the mail with the following command:
#
#defer Temporary error processing alias file
;;
esac
If you have qmail instead of sendmail, assuming the qmail alias user is
called "alias", you would change the first line in the previous example
to:
aliascheck --qmail "$RECIPIENT_LOCAL" alias > /dev/null
FILES
/etc/avenger/unknown
Mail Avenger rules for local email addresses that do not correspond
to local users, or correspond to local users without valid shells,
or local users with uid 0 (i.e., root). Note the location may be
different if you set EtcDir in your asmtpd.conf file.
/etc/mail/aliases.db
/etc/aliases.db
Default locations of sendmail alias file
/etc/mail/virtusertable.db
Default location of the sendmail virtual user table map, when this
feature is in use.
~alias/.qmail-*
Default locations of qmail alias files
/etc/password
System password file. (Note, however, that aliascheck uses the
getpwnam function, and will thus be compatible with schemes such as
NIS that do not keep all users in the local password file.)
SEE ALSO
avenger(1), asmtpd.conf(5), makemap(8),
The Mail Avenger home page: <http://www.mailavenger.org/>.
BUGS
aliascheck doesn’t necessarily know how to parse the particular
database format your sendmail installation uses for aliases. Make sure
you test it before using it in an avenger script.
In some sendmail installations, the alias database is not world
readable, which can obviously prevent aliascheck from working properly
if run under the wrong user identity (such as the AvengerUser).
It is quite possible for aliascheck to return a system error (exit code
2), particularly if you run it while you are rebuilding a large alias
database. (aliascheck checks for the existence of special key "@" in
the database.) Make sure you differentiate between error code 1 (no
user) and error code 2 (system error).
aliascheck may not do the right thing if you installed qmail with conf-
break set to a character other than "-".
Remember that aliascheck does not read your qmail users/assign or
users/cdb files--it only checks for .qmail files in the alias user’s
home directory.
AUTHOR
David Mazieres