CKPASSWD(1)

NAME
ckpasswd - nnrpd password authenticator

SYNOPSIS
ckpasswd [-s] [-d database] [-f filename]

DESCRIPTION
ckpasswd is the basic password authenticator for nnrpd, suitable for being run from an auth stanza in readers.conf(5). 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 checks the password against the password field returned by getpwnam(3). Note that these days most systems no longer make real passwords available via getpwnam(3) (some still do if and only if the program 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.

OPTIONS
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 create 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.

This option will not be available on systems without dbm or ndbm libraries. Read passwords from the given file rather than using getpwnam(3). The file is expected to be formatted like a system password file, at leat 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). INN does not come with a utility to create the encrypted passwords, but it's a quick job with Perl (see the example script under -d). Check passwords against the result of getspnam(3) instead of getpwnam(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 passwords, 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, since the NNTP protocol has no way of protecting passwords from casual interception, and using system passwords to authenticate NNTP connections therefore opens you up to the risk of password sniffing. If you do use system passwords to authenticate connections, you should seriously consider only doing NNTP through ssh tunnels or over SSL.

EXAMPLES
See readers.conf(5) for examples of nnrpd(8) authentication configuration that uses ckpasswd to check passwords.

HISTORY
Written by Russ Allbery <rra@stanford.edu> for InterNetNews.

$Id: ckpasswd.1,v 1.1.2.1 2000/11/06 08:41:11 rra Exp $

SEE ALSO
readers.conf(5), nnrpd(8)