[exim-dev] servers expansion

I'm wanting to be able to use expansion variables in the servers=
parameter of query-style lookups.

I can use variables if I put servers= inside the query, but if
servers= is used there I can't use tainted variables in the query.

I crawled around looking at the source code trying to
backtrace to the caller code and finally came up with this patch:

--- a/build/exim/src/lookups/lf_sqlperform.c
+++ b/build/exim/src/lookups/lf_sqlperform.c
@@ -129,7 +129,7 @@ else
     uschar * ele;
     for (int sep = ','; ele = string_nextinlist(&opts, &sep, NULL, 0); )
       if (Ustrncmp(ele, "servers=", 8) == 0)
-       { serverlist = ele + 8; break; }
+       { serverlist = expand_string( ele + 8 ); break; }
     }

if (!serverlist)
---

This seems to work for simple variables which is enough for me. Full
brace expansion does not work (I think the parser gets confused).

As I understand it this is not going to cause a memory leak.

a few lines down from this serverlist is checked to be taint-free so
this feels safe to me.

--
Jasen.