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  is present for FreeBSD, Mac OS X, and HP-UX.  I personally can only test on
  Linux and rely on others to report problems on other operating systems.

  Old versions of OpenSSH are known to call `pam_authenticate` followed by
  `pam_setcred(PAM_REINITIALIZE_CRED)` without first calling
  `pam_open_session`, thereby requesting that an existing ticket cache be
  renewed (similar to what a screensaver would want) rather than requesting a
  new ticket cache be created.  Since this behavior is indistinguishable at
  the PAM level from a screensaver, pam-krb5 when used with these old versions
  of OpenSSH will refresh the ticket cache of the OpenSSH daemon rather than
  setting up a new ticket cache for the user.  The resulting ticket cache will
  have the correct permissions (this is not a security concern), but will not
  be named correctly or referenced in the user's environment and will be
  overwritten by the next user login.  The best solution to this problem is to
  upgrade OpenSSH.  I'm not sure exactly when this problem was fixed, but at
  the very least OpenSSH 4.3 and later do not exhibit it.

test:
  lancaster: true
  prefix: |
    pam-krb5 comes with a comprehensive test suite, but it requires some
    configuration in order to test anything other than low-level utility
    functions.  For the full test suite, you will need to have a running KDC
    in which you can create two test accounts, one with admin access to the
    other.  Using a test KDC environment, if you have one, is recommended.

    Follow the instructions in `tests/config/README` to configure the test
    suite.

    Now, you can run the test suite with:
  suffix: |
    The default libkadm5clnt library on the system must match the
    implementation of your KDC for the module/expired test to work, since the
    two kadmin protocols are not compatible.  If you use the MIT library
    against a Heimdal server, the test will be skipped; if you use the Heimdal
    library against an MIT server, the test suite may hang.

    Several `module/expired` tests are expected to fail with Heimdal 1.5 due
    to a bug in Heimdal with reauthenticating immediately after a
    library-mediated password change of an expired password.  This is fixed in
    later releases of Heimdal.

    To run the full test suite, Perl 5.10 or later is required.  The following
    additional Perl modules will be used if present:

    * Test::Pod
    * Test::Spelling

    All are available on CPAN.  Those tests will be skipped if the modules are
    not available.

sections:
  - title: Configuring
    body: |
      Just installing the module does not enable it or change anything about
      your system authentication configuration.  To use the module for all
      system authentication on Debian systems, put something like:

      ```
          auth  sufficient   pam_krb5.so minimum_uid=1000
          auth  required     pam_unix.so try_first_pass nullok_secure
      ```

      in `/etc/pam.d/common-auth`, something like:

      ```
          session  optional  pam_krb5.so minimum_uid=1000
          session  required  pam_unix.so
      ```

      in `/etc/pam.d/common-session`, and something like:

      ```
          account  required  pam_krb5.so minimum_uid=1000
          account  required  pam_unix.so
      ```

      in `/etc/pam.d/common-account`.  The `minimum_uid` setting tells the PAM
      module to pass on any users with a UID lower than 1000, thereby
      bypassing Kerberos authentication for the root account and any system
      accounts.  You normally want to do this since otherwise, if the network
      is down, the Kerberos authentication can time out and make it difficult
      to log in as root and fix matters.  This also avoids problems with
      Kerberos principals that happen to match system accounts accidentally
      getting access to those accounts.

      Be sure to include the module in the session group as well as the auth
      group.  Without the session entry, the user's ticket cache will not be
      created properly for ssh logins (among possibly others).

      If your users should normally all use Kerberos passwords exclusively,
      putting something like:

      ```
          password sufficient pam_krb5.so minimum_uid=1000
          password required   pam_unix.so try_first_pass obscure md5
      ```

      in `/etc/pam.d/common-password` will change users' passwords in Kerberos
      by default and then only fall back on Unix if that doesn't work.  (You
      can make this tighter by using the more complex new-style PAM
      configuration.)  If you instead want to synchronize local and Kerberos
      passwords and change them both at the same time, you can do something
      like:

      ```
          password required   pam_unix.so obscure sha512
          password required   pam_krb5.so use_authtok minimum_uid=1000
      ```

      If you have multiple environments that you want to synchronize and you
      don't want password changes to continue if the Kerberos password change
      fails, use the `clear_on_fail` option.  For example:

      ```
          password required   pam_krb5.so clear_on_fail minimum_uid=1000
          password required   pam_unix.so use_authtok obscure sha512
          password required   pam_smbpass.so use_authtok
      ```

      In this case, if `pam_krb5` cannot change the password (due to password
      strength rules on the KDC, for example), it will clear the stored
      password (because of the `clear_on_fail` option), and since `pam_unix`
      and `pam_smbpass` are both configured with `use_authtok`, they will both
      fail.  `clear_on_fail` is not the default because it would interfere
      with the more common pattern of falling back to local passwords if the
      user doesn't exist in Kerberos.

      If you use a more complex configuration with the Linux PAM `[]` syntax
      for the session and account groups, note that `pam_krb5` returns a
      status of ignore, not success, if the user didn't log on with Kerberos.
      You may need to handle that explicitly with `ignore=ignore` in your
      action list.

      There are many, many other possibilities.  See the Linux PAM
      documentation for all the configuration options.

      On Red Hat systems, modify `/etc/pam.d/system-auth` instead, which
      contains all of the configuration for the different stacks.

      You can also use pam-krb5 only for specific services.  In that case,
      modify the files in `/etc/pam.d` for that particular service to use
      `pam_krb5.so` for authentication.  For services that are using passwords
      over TLS to authenticate users, you may want to use the `ignore_k5login`
      and `no_ccache` options to the authenticate module.  `.k5login`
      authorization is only meaningful for local accounts and ticket caches
      are usually (although not always) only useful for interactive sessions.

      Configuring the module for Solaris is both simpler and less flexible,
      since Solaris (at least Solaris 8 and 9, which are the last versions of
      Solaris with which this module was extensively tested) use a single
      `/etc/pam.conf` file that contains configuration for all programs.  For
      console login on Solaris, try something like:

      ```
          login auth sufficient /usr/local/lib/security/pam_krb5.so minimum_uid=100
          login auth required /usr/lib/security/pam_unix_auth.so.1 use_first_pass
          login account required /usr/local/lib/security/pam_krb5.so minimum_uid=100
          login account required /usr/lib/security/pam_unix_account.so.1
          login session required /usr/local/lib/security/pam_krb5.so retain_after_close minimum_uid=100
          login session required /usr/lib/security/pam_unix_session.so.1
      ```

      A similar configuration could be used for other services, such as ssh.
      See the pam.conf(5) man page for more information.  When using this
      module with Solaris login (at least on Solaris 8 and 9), you will
      probably also need to add `retain_after_close` to the PAM configuration
      to avoid having the user's credentials deleted before they are logged
      in.

      The Solaris Kerberos library reportedly does not support prompting for a
      password change of an expired account during authentication.  Supporting
      password change for expired accounts on Solaris with native Kerberos may
      therefore require setting the `defer_pwchange` or `force_pwchange`
      option for selected login applications.  See the description and
      warnings about that option in the pam_krb5(5) man page.

      Some configuration options may be put in the `krb5.conf` file used by
      your Kerberos libraries (usually `/etc/krb5.conf` or
      `/usr/local/etc/krb5.conf`) instead or in addition to the PAM
      configuration.  See the man page for more details.

      The Kerberos library, via pam-krb5, will prompt the user to change their
      password if their password is expired, but when using OpenSSH, this will
      only work when `ChallengeResponseAuthentication` is enabled.  Unless
      this option is enabled, OpenSSH doesn't pass PAM messages to the user
      and can only respond to a simple password prompt.

      If you are using MIT Kerberos, be aware that users whose passwords are
      expired will not be prompted to change their password unless the KDC
      configuration for your realm in `[realms]` in `krb5.conf` contains a
      `master_kdc` setting or, if using DNS SRV records, you have a DNS entry
      for `_kerberos-master` as well as `_kerberos`.
  - title: Debugging
    body: |
      The first step when debugging any problems with this module is to add
      `debug` to the PAM options for the module (either in the PAM
      configuration or in `krb5.conf`).  This will significantly increase the
      logging from the module and should provide a trace of exactly what
      failed and any available error information.

      Many Kerberos authentication problems are due to configuration issues in
      `krb5.conf`.  If pam-krb5 doesn't work, first check that `kinit` works
      on the same system.  That will test your basic Kerberos configuration.
      If the system has a keytab file installed that's readable by the process
      doing authentication via PAM, make sure that the keytab is current and
      contains a key for `host/<system>` where <system> is the fully-qualified
      hostname.  pam-krb5 prevents KDC spoofing by checking the user's
      credentials when possible, but this means that if a keytab is present it
      must be correct or authentication will fail.  You can check the keytab
      with `klist -k` and `kinit -k`.

      Be sure that all libraries and modules, including PAM modules, loaded by
      a program use the same Kerberos libraries.  Sometimes programs that use
      PAM, such as current versions of OpenSSH, also link against Kerberos
      directly.  If your sshd is linked against one set of Kerberos libraries
      and pam-krb5 is linked against a different set of Kerberos libraries,
      this will often cause problems (such as segmentation faults, bus errors,
      assertions, or other strange behavior).  Similar issues apply to the
      com_err library or any other library used by both modules and shared
      libraries and by the application that loads them.  If your OS ships