The LDAP directory has a PGP secured mail gateway that
allows users to safely and conveniently effect changes to their entries. It
makes use of PGP signed input messages to positively identify the user and
to confirm the validity of the request. Furthermore it implements a replay
cache that prevents the gateway from accepting the same message more than
There are three functions logically split into 3 seperate email addresses
that are implemented by the gateway: ping, new password and
changes. The function to act on is the first argument to the program.
Error handling is currently done by generating a bounce message and passing
descriptive error text to the mailer. This can generate a somewhat hard to
read error message, but it does have all the relevent information.
The ping command simply returns the users public record. It is useful for
testing the gateway and for the requester to get a basic dump of their
record. In future this address might 'freshen' the record to indicate the
user is alive. Any PGP signed message will produce a reply.
If a user looses their password they can request that a new one be generated
for them. This is done by sending the phrase "Please change my Debian
password" to email@example.com. The phrase is required to prevent the
daemon from triggering on arbitary signed email. The best way to invoke this
feature is with
echo "Please change my Debian password" | gpg --clearsign | mail firstname.lastname@example.org
After validating the request the daemon will generate a new random password,
set it in the directory and respond with an encrpyted message containing the
new password. The password can be changed using one of the other interface
An address (email@example.com) is provided for making almost arbitary
changes to the contents of the record. The daemon parses its input line by
line and acts on each line in a command oriented manner. Anything, except for
passwords, can be changed using this mechanism. Note however that because
this is a mail gateway it does stringent checking on its input. The other
tools allow fields to be set to virtually anything, the gateway requires
specific field formats to be met.
After processing the requests the daemon will generate a report which contains
each input command and the action taken. If there are any parsing errors
processing stops immediately, but valid changes up to that point are
- A line of the form 'field: value' will change the contents of
the field to value. Some simple checks are performed on value to make sure
that it is not set to nonsense. The values that can be changed are:
c, l, facsimiletelephonenumber, telephonenumber,
loginshell, emailforward, ircnick, onvacation,
- The daemon has a special parser to help changing latitude and longitude
values. It accepts several common formats for position information and
converts them to one of the standard forms. The permitted types are
D = Degrees, M = Minutes, S = Seconds, x = n,s,e,w
+-DDD.DDDDD, +- DDDMM.MMMM, +-DDDMMSS.SSSS [standard forms]
DDxMM.MMMM, DD:MM.MMMM x, DD:MM:SS.SSS X)
and the request format is 'Lat: xxx Long: xxx' where xxx
is one of the permitted types. The resulting response will include how the
input was parsed and the value in decimal degrees.
Part of the replicated dataset is a virtual .ssh/authorized_keys file for
each user. The change address is the simplest way to set the RSA key(s) you
intend to use. Simply place a key on a line by itself, the full SSH key
format specification is supported, see sshd(8). Probably the most common way
to use this function will be
cat .ssh/identity.pub | gpg --clearsign | mail firstname.lastname@example.org
which will set the authentication key to the identity you are using.
Multiple keys per user are supported, but they must all be sent at once.
- Debian.net DNS Zone Entry. The only way to get a debian.net address is
to use the mail gateway. It
will verify the request and prevent name collisions automatically. Requests
can take two forms: 'foo in a 188.8.131.52' or 'foo in cname
foo.bar.' The precise form is critical and must not be deviated from.
Like the SSH function above, multiple hosts are supported, but they must all
be sent at once. The debian.net zone is only reloaded once per day at
- If the single word show appears on a line then a PGP encrypted version
of the entire record will be attached to the resulting email.
In this document PGP refers to any message or key that GnuPG is
able to generate or parse, specificaly it includes both PGP2.x and OpenPGP
(aka GnuPG) keys.
Due to the replay cache the clock on the computer that generates the
signatures has to be accurate to at least one day. If it is off by several
months or more then the deamon will outright reject all messages.
Examples are given using GnuPG, but PGP 2.x can also be used. The correct
options to generate a clear signed ascii armored message in 'filter' mode
are pgp -fast which does the same as gpg --clearsign
Debian.org machines rely on secured replication to transfer login data out
of the database. Replication is performed at 15 min intervals so it can take
a short while before any changes made take effect.
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Last Modified: Fri, Jul 12 17:23:30 UTC 2002
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