LDAP Gateway

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 once.

There are three functions logically split into 3 separate 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 relevant information.

Ping

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.

New Password

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 chpasswd@db.oftc.net. The phrase is required to prevent the daemon from triggering on arbitrary signed email. The best way to invoke this feature is with

echo "Please change my Debian password" | gpg --clearsign | mail chpasswd@db.oftc.net

After validating the request the daemon will generate a new random password, set it in the directory and respond with an encrypted message containing the new password. The password can be changed using one of the other interface methods.

Changes

An address (changes@db.oftc.net) is provided for making almost arbitrary 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.

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. You can't set an empty string as value, use del instead (see below). The values that can be changed are: c, l, facsimiletelephonenumber, telephonenumber, postaladdress, postalcode, loginshell, emailforward, ircnick, onvacation, and labledurl
A line of the form 'del field' will completly remove all occurrences of a field. Useful e.g. to unset your vacation status. The fields that can be deleted are: c, l, facsimiletelephonenumber, telephonenumber, postaladdress, postalcode, emailforward, ircnick, onvacation, labeleduri, latitude, longitude, dnsZoneEntry icquin, sshrsaauthkey, and sshdsaauthkey
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/id_dsa.pub | gpg --clearsign | mail change@db.oftc.net
```
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.
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.

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 processed.

Notes

In this document PGP refers to any message or key that GnuPG is able to generate or parse, specifically 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 daemon 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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