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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  14  <h1>
  15      <a href="http://people.skolelinux.org/pere/blog/">Petter Reinholdtsen</a>
  16
  17  </h1>
  18
  19 </div>
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  22     <div class="entry">
  23       <div class="title">Forcing new users to change their password on first login</div>
  24       <div class="date"> 2nd May 2010</div>
  25       <div class="body"><p>One interesting feature in Active Directory, is the ability to
  26 create a new user with an expired password, and thus force the user to
  27 change the password on the first login attempt.</p>
  28
  29 <p>I'm not quite sure how to do that with the LDAP setup in Debian
  30 Edu, but did some initial testing with a local account.  The account
  31 and password aging information is available in /etc/shadow, but
  32 unfortunately, it is not possible to specify an expiration time for
  33 passwords, only a maximum age for passwords.</p>
  34
  35 <p>A freshly created account (using adduser test) will have these
  36 settings in /etc/shadow:</p>
  37
  38 <blockquote><pre>
  39 root@tjener:~# chage -l test
  40 Last password change                                    : May 02, 2010
  41 Password expires                                        : never
  42 Password inactive                                       : never
  43 Account expires                                         : never
  44 Minimum number of days between password change          : 0
  45 Maximum number of days between password change          : 99999
  46 Number of days of warning before password expires       : 7
  47 root@tjener:~#
  48 </pre></blockquote>
  49
  50 <p>The only way I could come up with to create a user with an expired
  51 account, is to change the date of the last password change to the
  52 lowest value possible (January 1th 1970), and the maximum password age
  53 to the difference in days between that date and today.  To make it
  54 simple, I went for 30 years (30 * 365 = 10950) and January 2th (to
  55 avoid testing if 0 is a valid value).</p>
  56
  57 <p>After using these commands to set it up, it seem to work as
  58 intended:</p>
  59
  60 <blockquote><pre>
  61 root@tjener:~# chage -d 1 test; chage -M 10950 test
  62 root@tjener:~# chage -l test
  63 Last password change                                    : Jan 02, 1970
  64 Password expires                                        : never
  65 Password inactive                                       : never
  66 Account expires                                         : never
  67 Minimum number of days between password change          : 0
  68 Maximum number of days between password change          : 10950
  69 Number of days of warning before password expires       : 7
  70 root@tjener:~#
  71 </pre></blockquote>
  72
  73 <p>So far I have tested this with ssh and console, and kdm (in
  74 Squeeze) login, and all ask for a new password before login in the
  75 user (with ssh, I was thrown out and had to log in again).</p>
  76
  77 <p>Perhaps we should set up something similar for Debian Edu, to make
  78 sure only the user itself have the account password?</p>
  79
  80 <p>If you want to comment on or help out with implementing this for
  81 Debian Edu, please contact us on debian-edu@lists.debian.org.</p>
  82
  83 <p>Update 2010-05-02 17:20: Paul Tötterman tells me on IRC that the
  84 shadow(8) page in Debian/testing now state that setting the date of
  85 last password change to zero (0) will force the password to be changed
  86 on the first login.  This was not mentioned in the manual in Lenny, so
  87 I did not notice this in my initial testing.  I have tested it on
  88 Squeeze, and '<tt>chage -d 0 username</tt>' do work there.  I have not
  89 tested it on Lenny yet.</p>
  90
  91 <p>Update 2010-05-02-19:05: Jim Paris tells me via email that an
  92 equivalent command to expire a password is '<tt>passwd -e
  93 username</tt>', which insert zero into the date of the last password
  94 change.</p>
  95 </div>
  96
  97       <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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