%{rand} in recent versions

[Arran Cudbard-Bell]

On 15 Jul 2013, at 08:20, Arran Cudbard-Bell <a.cudbardb at freeradius.org> wrote:

> 
> On 15 Jul 2013, at 07:41, Stefan Winter <stefan.winter at restena.lu> wrote:
> 
>> Hi,
>> 
>> while I've been staring at debug output of 2.x.x I noticed that%{rand:x}
>> doesn't seem to do what it should:
>> 
>> ++? if (true ) -> TRUE
>> ++- entering if (true ) {...}
>>       expand: %{rand:1000000}%Y%m%d%H%M%S -> 201307150802013-07-15
>> 08:17:08
>>       expand: %{rand:1000000}%Y%m%d%H%M%S -> 201307150802013-07-15
>> 08:17:08
>>       expand: %{rand:1000000}%Y%m%d%H%M%S -> 201307150802013-07-15
>> 08:17:08
>> 
>> As you see, the expression %{rand:1000000} gets expanded into an empty
>> string. In my particular case, this leads to a lot less entropy than I
>> thought. The expansion is there three times alright, that's as per
>> config, but I would have expected the results to be different.
>> 
>> Now that I knew where to look, I went back to 2.2.0 mainstream release
>> code - and saw the same :-(
> 
> Works in 3.0.0, but yes, broken in v2.x.x HEAD. Odd seeing as the xlat code is very similar.

So after investigating this a bit more, it seems the correct way to pass arguments to xlat functions in 2.x.x is with a space after the colon.

This is because xlat functions which take numerical arguments, may get mistaken for attributes with tag selectors by the xlat parser code (in 2.x.x at least).

The behaviour change which caused your issue was introduced by https://github.com/FreeRADIUS/freeradius-server/commit/33e9e1f7fbf5e63baa0fbd734e570474bee10878, but it's not a bug. The man pages for xlat, show a space after the ':' for module calls.

The parser is 3.0.0 is smarter, and uses the table of registered xlat functions to determine whether it's an xlat module or an attribute. We don't do this in 2.x.x because of the potential performance hit. Though as compilation and evaluation is still done at runtime... um never mind, that'll be fixed in 3.1 :) The difficult work was splitting it into two stages, which is now complete.

Anyway %{rand: 1000000} should work fine.

+- entering group authorize {...}
	expand:  500 ->  500
	expand: %{rand: 500} -> 309
	expand: ccccccccccccc -> ccccccccccccc
	expand: %{randstr:ccccccccccccc} -> aodcqryxbsgpg


Arran Cudbard-Bell <a.cudbardb at freeradius.org>
FreeRADIUS Development Team