CKPASSWD(8) InterNetNews Documentation CKPASSWD(8)NAMEckpasswd - nnrpd password authenticator
SYNOPSISckpasswd [-gs] [-d database] [-f filename] [-u username -p password]
DESCRIPTIONckpasswd is the basic password authenticator for nnrpd, suitable for
being run from an auth stanza in readers.conf. See readers.conf(5) for
more information on how to configure an nnrpd authenticator.
ckpasswd accepts a username and password from nnrpd and tells nnrpd(8)
whether that's the correct password for that username. By default,
when given no arguments, it tries to check the password using PAM if
support for PAM was found when INN was built. Failing that, it tries
to check the password against the password field returned by getpw‐
nam(3). Note that these days most systems no longer make real pass‐
words available via getpwnam(3) (some still do if and only if the pro‐
gram calling getpwnam(3) is running as root).
Note that ckpasswd expects all passwords to be stored encrypted by the
system crypt(3) function and calls crypt(3) on the supplied password
before comparing it to the expected password (when using any method
other than PAM).
OPTIONS-d database
Read passwords from a database (ndbm or dbm format depending on
what your system has) rather than by using getpwnam(3). ckpasswd
expects database.dir and database.pag to exist and to be a database
keyed by username with the encrypted passwords as the values.
While INN doesn't come with a program intended specifically to cre‐
ate such databases, on most systems it's fairly easy to write a
Perl script to do so. Something like:
#!/usr/bin/perl
use NDBM_File;
use Fcntl;
tie (%db, 'NDBM_File', '/path/to/database', O_RDWR⎪O_CREAT, 0640)
or die "Cannot open /path/to/database: $!\n";
$⎪ = 1;
print "Username: ";
my $user = <STDIN>;
chomp $user;
print "Password: ";
my $passwd = <STDIN>;
chomp $passwd;
my @alphabet = ('.', '/', 0..9, 'A'..'Z', 'a'..'z');
my $salt = join '', @alphabet[rand 64, rand 64];
$db{$user} = crypt ($passwd, $salt);
untie %db;
Note that this will echo back the password when typed; there are
obvious improvements that could be made to this, but it should be a
reasonable start. Sometimes a program like this will be available
with the name dbmpasswd.
This option will not be available on systems without dbm or ndbm
libraries.
-f filename
Read passwords from the given file rather than using getpwnam(3).
The file is expected to be formatted like a system password file,
at least vaguely. That means each line should look something like:
username:pdIh9NCNslkq6
(and each line may have an additional colon after the encrypted
password and additional data; that data will be ignored by
ckpasswd). Lines starting with a number sign (`#') are ignored.
INN does not come with a utility to create the encrypted passwords,
but htpasswd (which comes with Apache) can do so and it's a quick
job with Perl (see the example script under -d). If using Apache's
htpasswd program, be sure to give it the -d option so that it will
use crypt(3).
-g Attempt to look up system group corresponding to username and
return a string like "user@group" to be matched against in read‐
ers.conf. This option is incompatible with the -d and -f options.
-p password
Use password as the password for authentication rather than reading
a password using the nnrpd authenticator protocol. This option is
useful only for testing your authentication system (particularly
since it involves putting a password on the command line), and does
not work when ckpasswd is run by nnrpd. If this option is given,
-u must also be given.
-s Check passwords against the result of getspnam(3) instead of getpw‐
nam(3). This function, on those systems that supports it, reads
from /etc/shadow or similar more restricted files. If you want to
check passwords supplied to nnrpd(8) against system account pass‐
words, you will probably have to use this option on most systems.
Most systems require special privileges to call getspnam(3), so in
order to use this option you may need to make ckpasswd setgid to
some group (like group "shadow") or even setuid root. ckpasswd has
not been specifically audited for such uses! It is, however, a
very small program that you should be able to check by hand for
security.
This configuration is not recommended if it can be avoided, for
serious security reasons. See "SECURITY CONSIDERATIONS" in read‐
ers.conf(5) for discussion.
-u username
Authenticate as username. This option is useful only for testing
(so that you can test your authentication system easily) and does
not work when ckpasswd is run by nnrpd. If this option is given,
-p must also be given.
EXAMPLES
See readers.conf(5) for examples of nnrpd(8) authentication configura‐
tion that uses ckpasswd to check passwords.
To test to make sure that ckpasswd is working correctly, you can run it
manually and then give it the username (prefixed with "ClientAuth‐
name:") and password (prefixed with "ClientPassword:") on standard
input. For example:
(echo 'ClientAuthname: test' ; echo 'ClientPassword: testing') \
⎪ ckpasswd-f /path/to/passwd/file
will check a username of "test" and a password of "testing" against the
username and passwords stored in /path/to/passwd/file. On success,
ckpasswd will print "User:test" and exit with status 0. On failure, it
will print some sort of error message and exit a non-zero status.
HISTORY
Written by Russ Allbery <rra@stanford.edu> for InterNetNews.
$Id: ckpasswd.8,v 1.2.2.2 2003/08/08 22:02:42 vinocur Exp $
SEE ALSOreaders.conf(5), nnrpd(8)INN 2.4.1 2003-07-30 CKPASSWD(8)
