mod_dav: Fix security issue in unreleased MS-WDV support:

* modules/dav/main/ms_wdv.c (mswdv_combined_proppatch):
  The MS-WDV combined PROPPATCH handler reads a 16-byte hex length
  prefix from the request body and uses it directly for memory
  allocation without bounds checking. An attacker can specify an
  extremely large value to trigger OOM and crash the worker process.

  This patch validates the parsed length against LimitXMLRequestBody
  and APR_SIZE_MAX before allocation.

Reported by: Pavel Kohout, Aisle Research, www.aisle.com
Submitted by: Pavel Kohout, jorton
Github: closes #592


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1931148 13f79535-47bb-0310-9956-ffa450edef68

Author: notroj

modules/dav/main/ms_wdv.c

@@ -6,6 +6,7 @@
 #include "http_protocol.h"
 #include "http_request.h"
 #include "http_log.h"
+#include "http_core.h"
 
 #include "mod_dav.h"
 
@@ -589,7 +590,7 @@ static dav_error *mswdv_combined_proppatch(request_rec *r)
     apr_bucket_brigade *bb;
     apr_status_t status;
     apr_size_t len = 16;
-    apr_off_t proppatch_len;
+    apr_off_t proppatch_len, limit;
     char proppatch_len_str[16 + 1];
     char *proppatch_data;
 
@@ -618,6 +619,17 @@ static dav_error *mswdv_combined_proppatch(request_rec *r)
         return dav_new_error(r->pool, HTTP_BAD_REQUEST, 0, status,
                              "Bad PROPPATCH part length");
 
+    /* Validate PROPPATCH length against configured limits */
+    limit = ap_get_limit_xml_body(r);
+    if (limit > 0 && proppatch_len > limit) {
+        return dav_new_error(r->pool, HTTP_REQUEST_ENTITY_TOO_LARGE, 0, 0,
+                             "PROPPATCH part length exceeds configured limit");
+    }
+    if (proppatch_len <= 0 || proppatch_len > (apr_off_t)APR_SIZE_MAX) {
+        return dav_new_error(r->pool, HTTP_REQUEST_ENTITY_TOO_LARGE, 0, 0,
+                             "PROPPATCH part length invalid or too large");
+    }
+
     apr_brigade_destroy(bb);
 
     bb = apr_brigade_create(r->pool, r->connection->bucket_alloc);