Mailing-List: contact dev-help@httpd.apache.org; run by ezmlm
Precedence: bulk
Reply-To: dev@httpd.apache.org
Received-SPF: neutral (hermes.apache.org: local policy)
Message-ID: <41B17401.5000905@apache.org>
Date: Sat, 04 Dec 2004 09:23:29 +0100
From: Mladen Turk <mturk@apache.org>
User-Agent: Mozilla
MIME-Version: 1.0
To: HTTPD Developers List <dev@httpd.apache.org>
Subject: mod_headers -- RequestHeader passing common vars.
Content-Type: multipart/mixed;
 boundary="------------090209010309070406090705"

This is a multi-part message in MIME format.
--------------090209010309070406090705
Content-Type: text/plain; charset=ISO-8859-2; format=flowed
Content-Transfer-Encoding: 7bit

Hi all,

Is there any reason (RFC or security) that prevents using common vars
within 'RequestHeader XX %{ENV_VAR}e'. Those can now be only set by
SetEnv, SetEnvIf and PassEnv.

A simple patch that calls ap_add_common_vars(r) before processing
the variable from r->subprocess_env will do more then enough.
It will allow to pass the REMOTE_USER for example down the reverse
proxy backend as header.

Second thing is setting the unknown value to string "(null)".
I propose to not set anything if the header value is not present and
to remove the value from headers_in if present and the required env var
doesn't exists.

As an example of current behavior:
RequestHeader REMOTE_USER %{REMOTE_USER}e
sets the header:
HTTP_REMOTE_USER="(null)"
Of course the '(null)' is far from being a valid user name.


I have enclosed the patch.

Regards,
Mladen

--------------090209010309070406090705
Content-Type: text/plain;
 name="mod_headers.patch"
Content-Transfer-Encoding: 7bit
Content-Disposition: inline;
 filename="mod_headers.patch"

Index: mod_headers.c
===================================================================
--- mod_headers.c	(revision 109218)
+++ mod_headers.c	(working copy)
@@ -77,6 +77,7 @@
 #include "http_log.h"
 #include "util_filter.h"
 #include "http_protocol.h"
+#include "util_script.h"
 
 #include "mod_ssl.h" /* for the ssl_var_lookup optional function defn */
 
@@ -177,12 +178,15 @@
 
 static const char *header_request_env_var(request_rec *r, char *a)
 {
-    const char *s = apr_table_get(r->subprocess_env,a);
+    const char *s;
 
+    ap_add_common_vars(r);
+    s = apr_table_get(r->subprocess_env,a);
+
     if (s)
         return unwrap_header(r->pool, s);
     else
-        return "(null)";
+        return NULL;
 }
 
 static const char *header_request_ssl_var(request_rec *r, char *name)
@@ -193,10 +197,10 @@
         if (val && val[0])
             return unwrap_header(r->pool, val);
         else
-            return "(null)";
+            return NULL;
     }
     else {
-        return "(null)";
+        return NULL;
     }
 }
 
@@ -504,12 +508,14 @@
  
     for (i = 0; i < hdr->ta->nelts; i++) {
         s = tag[i].func(r, tag[i].arg);
-        if (str == NULL) 
-            str = apr_pstrdup(r->pool, s);
-        else
-            str = apr_pstrcat(r->pool, str, s, NULL);
+        if (s) {
+            if (str == NULL) 
+                str = apr_pstrdup(r->pool, s);
+            else
+                str = apr_pstrcat(r->pool, str, s, NULL);
+        }
     }
-    return str ? str : "";
+    return str;
 }
 
 static int echo_header(echo_do *v, const char *key, const char *val)
@@ -532,7 +538,7 @@
     for (i = 0; i < fixup->nelts; ++i) {
         header_entry *hdr = &((header_entry *) (fixup->elts))[i];
         const char *envar = hdr->condition_var;
-
+        char *tag;
 	/* ignore early headers in late calls */
         if (!early && (envar == condition_early)) {
             continue;
@@ -555,13 +561,21 @@
 
         switch (hdr->action) {
         case hdr_add:
-            apr_table_addn(headers, hdr->header, process_tags(hdr, r));
+            tag = process_tags(hdr, r);
+            if (tag)
+                apr_table_addn(headers, hdr->header, tag);
             break;
         case hdr_append:
-            apr_table_mergen(headers, hdr->header, process_tags(hdr, r));
+            tag = process_tags(hdr, r);
+            if (tag)
+                apr_table_mergen(headers, hdr->header, tag);
             break;
         case hdr_set:
-            apr_table_setn(headers, hdr->header, process_tags(hdr, r));
+            tag = process_tags(hdr, r);
+            if (tag)
+                apr_table_setn(headers, hdr->header, tag);
+            else
+                apr_table_unset(headers, hdr->header);
             break;
         case hdr_unset:
             apr_table_unset(headers, hdr->header);

--------------090209010309070406090705--