Section 8. Rewriting user names

8. Rewriting user names

You can change the User-Name attribute in each request by using RewriteUsername configuration parameters globally and in different clauses. This allows you to apply separate rewriting rules to the User-Name. In case there are several clauses with RewriteUsername parameters, rewriting rules for a request are executed in the following order:

Globally when received by Radiator. This occurs prior to other rewrites.
Within a <Client>, <ServerRADSEC> or <ServerTACACSPLUS> clause depending on how the request was received.
When handled by a <Handler> or <Realm> depending on which clause is selected.
When handled by an <AuthBy GROUP> clause. This occurs before any of the <AuthBy> clauses in the group are called.

The parameter is a Perl substitution regular expression that is applied to the User-Name attribute in the request. If you do not know how to write Perl substitution regexps, you should consult a Perl programmer. At Trace level 4, you can see the result of each separate rewrite for debugging purposes.

You can have any number of RewriteUsername parameters. The rewrites are applied to the username in the same order that they appear in the configuration file.

Here are some example of using this feature in a variety of circumstances:

Strip the realm name from the username. This is handy if your user database contains only the usernames without the realm extension, for example, fred instead of fred@yourdomain.com.
```
# Strip realm
RewriteUsername s/^([^@]+).*/$1/
```
Convert Microsoft or other style usernames from domain\user to the user@realm form that Radiator uses. Note that regexps need to quote some characters. For example @ needs to be quoted with backslash \:
```
# Convert a MSN realm/user into user@realm
RewriteUsername s/^(.*)\/(.*)/$2\@$1/
```

Force all usernames to be lower case or upper case:

# Translate all uppercase to lowercase
RewriteUsername tr/A-Z/a-z/

Remove any white spaces from the username:
```
RewriteUsername s/\s+//g
```

Convert all <user>@realm1 to <user>@realm2:

RewriteUsername s/^([^@]+)\@realm1/$1\@realm2/

Change any mikem username to fred:
```
RewriteUsername s/^mikem\@/fred\@/
```