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