blog/Forcing_new_users_to_change_their_password_on_first_login.html

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   6     <title>Petter Reinholdtsen: Forcing new users to change their password on first login</title>
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  12  <h1>
  13      <a href="http://people.skolelinux.org/pere/blog/">Petter Reinholdtsen</a>
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  21       <div class="title">Forcing new users to change their password on first login</div>
  22       <div class="date"> 2nd May 2010</div>
  23       <div class="body"><p>One interesting feature in Active Directory, is the ability to
  24 create a new user with an expired password, and thus force the user to
  25 change the password on the first login attempt.</p>
  26
  27 <p>I'm not quite sure how to do that with the LDAP setup in Debian
  28 Edu, but did some initial testing with a local account.  The account
  29 and password aging information is available in /etc/shadow, but
  30 unfortunately, it is not possible to specify an expiration time for
  31 passwords, only a maximum age for passwords.</p>
  32
  33 <p>A freshly created account (using adduser test) will have these
  34 settings in /etc/shadow:</p>
  35
  36 <blockquote><pre>
  37 root@tjener:~# chage -l test
  38 Last password change                                    : May 02, 2010
  39 Password expires                                        : never
  40 Password inactive                                       : never
  41 Account expires                                         : never
  42 Minimum number of days between password change          : 0
  43 Maximum number of days between password change          : 99999
  44 Number of days of warning before password expires       : 7
  45 root@tjener:~#
  46 </pre></blockquote>
  47
  48 <p>The only way I could come up with to create a user with an expired
  49 account, is to change the date of the last password change to the
  50 lowest value possible (January 1th 1970), and the maximum password age
  51 to the difference in days between that date and today.  To make it
  52 simple, I went for 30 years (30 * 365 = 10950) and January 2th (to
  53 avoid testing if 0 is a valid value).</p>
  54
  55 <p>After using these commands to set it up, it seem to work as
  56 intended:</p>
  57
  58 <blockquote><pre>
  59 root@tjener:~# chage -d 1 test; chage -M 10950 test
  60 root@tjener:~# chage -l test
  61 Last password change                                    : Jan 02, 1970
  62 Password expires                                        : never
  63 Password inactive                                       : never
  64 Account expires                                         : never
  65 Minimum number of days between password change          : 0
  66 Maximum number of days between password change          : 10950
  67 Number of days of warning before password expires       : 7
  68 root@tjener:~#
  69 </pre></blockquote>
  70
  71 <p>So far I have tested this with ssh and console, and kdm (in
  72 Squeeze) login, and all ask for a new password before login in the
  73 user (with ssh, I was thrown out and had to log in again).</p>
  74
  75 <p>Perhaps we should set up something similar for Debian Edu, to make
  76 sure only the user itself have the account password?</p>
  77
  78 <p>If you want to comment on or help out with implementing this for
  79 Debian Edu, please contact us on debian-edu@lists.debian.org.</p>
  80
  81 <p>Update 2010-05-02 17:20: Paul Tötterman tells me on IRC that the
  82 shadow(8) page in Debian/testing now state that setting the date of
  83 last password change to zero (0) will force the password to be changed
  84 on the first login.  This was not mentioned in the manual in Lenny, so
  85 I did not notice this in my initial testing.  I have tested it on
  86 Squeeze, and '<tt>chage -d 0 username</tt>' do work there.  I have not
  87 tested it on Lenny yet.</p>
  88
  89 <p>Update 2010-05-02-19:05: Jim Paris tells me via email that an
  90 equivalent command to expire a password is '<tt>passwd -e
  91 username</tt>', which insert zero into the date of the last password
  92 change.</p>
  93 </div>
  94
  95       <div class="tags">Tags: <a href="http://people.skolelinux.org/pere/blog/tags/debian edu">debian edu</a>, <a href="http://people.skolelinux.org/pere/blog/tags/english">english</a>, <a href="http://people.skolelinux.org/pere/blog/tags/nuug">nuug</a>, <a href="http://people.skolelinux.org/pere/blog/tags/sikkerhet">sikkerhet</a>.</div>
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