generate a random value with unlang?

[Phil Mayers]

On 21/03/12 10:07, Stefan Winter wrote:
> Hi,
>
> in some weird business case, I would like to generate a one-time use
> token for later consumption in post-auth. So when the user is accepted,
> trigger an
>
> {sql:INSERT randomvalue INTO someplace}
>
> The value should be new for every Access-Accept. I wonder how to
> generate such a random value with unlang. Is there some {%rand} or
> anything like that?
>
> Currently I do it embedded in the INSERT:
>
> INSERT ... SHA1(RAND())... INTO someplace
>
> but our MySQL admins don't like me doing that. So I'd prefer to do this
> on FreeRADIUS and send a simple string to the DB.


How secure a random value? You could generate a reasonably unique value 
with something like:

  update request {
   My-Random := "%{md5:A-Secret-String/%l/%n/%I}"
  }

There's no built-in xlat for "rand()" but it would be very trivial to add:

--- xlat.c	2012-03-21 11:00:51.736371799 +0000
+++ xlat.c~	2012-01-05 17:06:51.512061373 +0000
@@ -628,17 +628,6 @@
  	return strlen(out);
  }

-/**
- * @brief Return a random integer
- *
- */
-static size_t xlat_rand(UNUSED void *instance, REQUEST *request,
-		       char *fmt, char *out, size_t outlen,
-		       UNUSED RADIUS_ESCAPE_STRING func)
-{
-	snprintf(out, outlen, "%d", fr_rand());
-	return strlen(out);
-}

  /**
   * @brief Convert a string to lowercase
@@ -840,11 +829,6 @@
  		rad_assert(c != NULL);
  		c->internal = TRUE;

-		xlat_register("rand", xlat_rand, &xlat_inst[0]);
-		c = xlat_find("rand");
-		rad_assert(c != NULL);
-		c->internal = TRUE;
-
  		xlat_register("tolower", xlat_lc, &xlat_inst[0]);
  		c = xlat_find("tolower");
  		rad_assert(c != NULL);