1CKPASSWD(8) InterNetNews Documentation CKPASSWD(8)
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6 ckpasswd - nnrpd password authenticator
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9 ckpasswd [-gs] [-d database] [-f filename] [-u username -p password]
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12 ckpasswd is the basic password authenticator for nnrpd, suitable for
13 being run from an auth stanza in readers.conf. See readers.conf(5) for
14 more information on how to configure an nnrpd authenticator.
15 ckpasswd accepts a username and password from nnrpd and tells nnrpd(8)
17 whether that's the correct password for that username. By default,
18 when given no arguments, it tries to check the password using PAM if
19 support for PAM was found when INN was built. Failing that, it tries
20 to check the password against the password field returned by
21 getpwnam(3). Note that these days most systems no longer make real
22 passwords available via getpwnam(3) (some still do if and only if the
23 program calling getpwnam(3) is running as root).
24 When using PAM, ckpasswd identifies itself as "nnrpd", not as
26 "ckpasswd", and the PAM configuration must be set up accordingly. The
27 details of PAM configuration are different on different operating
28 systems (and even different Linux distributions); see EXAMPLES below
29 for help getting started, and look for a pam(7) or pam.conf(4) manual
30 page on your system.
31 When using any method other than PAM, ckpasswd expects all passwords to
33 be stored encrypted by the system crypt(3) function and calls crypt(3)
34 on the supplied password before comparing it to the expected password.
35 If you're using a different password hash scheme (like MD5), you must
36 use PAM.
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39 -d database
40 Read passwords from a database (ndbm, gdbm or dbm format depending
41 on what your system has) rather than by using getpwnam(3).
42 ckpasswd expects database.dir and database.pag to exist and to be a
43 database keyed by username with the encrypted passwords as the
44 values.
45 While INN doesn't come with a program intended specifically to
47 create such databases, on most systems it's fairly easy to write a
48 Perl script to do so. Something like:
49 #!/usr/bin/perl
51 use NDBM_File;
52 use Fcntl;
53 tie (%db, 'NDBM_File', '/path/to/database', O_RDWR|O_CREAT, 0640)
54 or die "Cannot open /path/to/database: $!\n";
55 $| = 1;
56 print "Username: ";
57 my $user = <STDIN>;
58 chomp $user;
59 print "Password: ";
60 my $passwd = <STDIN>;
61 chomp $passwd;
62 my @alphabet = ('.', '/', 0..9, 'A'..'Z', 'a'..'z');
63 my $salt = join '', @alphabet[rand 64, rand 64];
64 $db{$user} = crypt ($passwd, $salt);
65 untie %db;
66 Note that this will echo back the password when typed; there are
68 obvious improvements that could be made to this, but it should be a
69 reasonable start. Sometimes a program like this will be available
70 with the name dbmpasswd.
71 This option will not be available on systems without ndbm, gdbm or
73 dbm libraries.
74 -f filename
76 Read passwords from the given file rather than using getpwnam(3).
77 The file is expected to be formatted like a system password file,
78 at least vaguely. That means each line should look something like:
79 username:pdIh9NCNslkq6
81 (and each line may have an additional colon after the encrypted
83 password and additional data; that data will be ignored by
84 ckpasswd). Lines starting with a number sign ("#") are ignored.
85 INN does not come with a utility to create the encrypted passwords,
86 but htpasswd (which comes with Apache) can do so and it's a quick
87 job with Perl (see the one-line example script below).
88 A line in filename for the user "user" with the password "pass"
90 would be "user:LIfOpbjNaEQYE" as obtained with the following
91 command:
92 % htpasswd -nbd user pass
94 user:LIfOpbjNaEQYE
95 In case htpasswd is not installed on your server, just use the
97 following Perl command which does the same job:
98 % perl -e 'print "user:".crypt("pass", "LI")."\n";'
100 user:LIfOpbjNaEQYE
101 -g Attempt to look up system group corresponding to username and
103 return a string like "user@group" to be matched against in
104 readers.conf. This option is incompatible with the -d and -f
105 options.
106 -p password
108 Use password as the password for authentication rather than reading
109 a password using the nnrpd authenticator protocol. This option is
110 useful only for testing your authentication system (particularly
111 since it involves putting a password on the command line), and does
112 not work when ckpasswd is run by nnrpd. If this option is given,
113 -u must also be given.
114 -s Check passwords against the result of getspnam(3) instead of
116 getpwnam(3). This function, on those systems that supports it,
117 reads from /etc/shadow or similar more restricted files. If you
118 want to check passwords supplied to nnrpd(8) against system account
119 passwords, you will probably have to use this option on most
120 systems.
121 Most systems require special privileges to call getspnam(3), so in
123 order to use this option you may need to make ckpasswd setgid to
124 some group (like group "shadow") or even setuid root. ckpasswd has
125 not been specifically audited for such uses! It is, however, a
126 very small program that you should be able to check by hand for
127 security.
128 This configuration is not recommended if it can be avoided, for
130 serious security reasons. See "SECURITY CONSIDERATIONS" in
131 readers.conf(5) for discussion.
132 -u username
134 Authenticate as username. This option is useful only for testing
135 (so that you can test your authentication system easily) and does
136 not work when ckpasswd is run by nnrpd. If this option is given,
137 -p must also be given.
138
140 See readers.conf(5) for examples of nnrpd(8) authentication
141 configuration that uses ckpasswd to check passwords.
142 An example PAM configuration for /etc/pam.conf that tells ckpasswd to
144 check usernames and passwords against system accounts is:
145 nnrpd auth required pam_unix.so
147 nnrpd account required pam_unix.so
148 Your system may want you to instead create a file named nnrpd in
150 /etc/pam.d with lines like:
151 auth required pam_unix.so
153 account required pam_unix.so
154 This is only the simplest configuration. You may be able to include
156 common shared files, and you may want to stack other modules, either to
157 allow different authentication methods or to apply restrictions like
158 lists of users who can't authenticate using ckpasswd. The best guide
159 is the documentation for your system and the other PAM configurations
160 you're already using.
161 To test to make sure that ckpasswd is working correctly, you can run it
163 manually and then give it the username (prefixed with
164 "ClientAuthname:") and password (prefixed with "ClientPassword:") on
165 standard input. For example:
166 (echo 'ClientAuthname: test' ; echo 'ClientPassword: testing') \
168 | ckpasswd -f /path/to/passwd/file
169 will check a username of "test" and a password of "testing" against the
171 username and passwords stored in /path/to/passwd/file. On success,
172 ckpasswd will print "User:test" and exit with status 0. On failure, it
173 will print some sort of error message and exit a non-zero status.
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176 Written by Russ Allbery <eagle@eyrie.org> for InterNetNews.
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179 crypt(3), nnrpd(8), pam(7), readers.conf(5).
180INN 2.6.5 2022-01-23 CKPASSWD(8)