From 8aca45b45b116abaa9594fc7f065128b858613d2 Mon Sep 17 00:00:00 2001
From: John Christopher Anderson <jchris@apache.org>
Date: Wed, 5 May 2010 19:51:32 +0000
Subject: rewriter security to allow isolation of databases via subdomains

git-svn-id: https://svn.apache.org/repos/asf/couchdb/trunk@941451 13f79535-47bb-0310-9956-ffa450edef68
---
 etc/couchdb/default.ini.tpl.in      |  1 +
 share/www/script/test/rewrite.js    | 30 ++++++++++++++++++++----------
 src/couchdb/couch_httpd_rewrite.erl | 26 ++++++++++++++++++--------
 3 files changed, 39 insertions(+), 18 deletions(-)

diff --git a/etc/couchdb/default.ini.tpl.in b/etc/couchdb/default.ini.tpl.in
index d6f52096..fb88ba63 100644
--- a/etc/couchdb/default.ini.tpl.in
+++ b/etc/couchdb/default.ini.tpl.in
@@ -18,6 +18,7 @@ bind_address = 127.0.0.1
 max_connections = 2048
 authentication_handlers = {couch_httpd_oauth, oauth_authentication_handler}, {couch_httpd_auth, cookie_authentication_handler}, {couch_httpd_auth, default_authentication_handler}
 default_handler = {couch_httpd_db, handle_request}
+secure_rewrites = true
 
 [log]
 file = %localstatelogdir%/couch.log
diff --git a/share/www/script/test/rewrite.js b/share/www/script/test/rewrite.js
index 848427be..d3888d9a 100644
--- a/share/www/script/test/rewrite.js
+++ b/share/www/script/test/rewrite.js
@@ -137,14 +137,7 @@ couchTests.rewrite = function(debug) {
               "query": {
                 "key": [":a", ":b"]
               }
-            },
-            
-            {
-              "from": "uuids",
-              "to": "../../../_uuids"
             }
-            
-            
           ],
           lists: {
             simpleForm: stringFun(function(head, req) {
@@ -339,12 +332,29 @@ couchTests.rewrite = function(debug) {
         T(/Value: doc 4/.test(xhr.responseText));
         
         // test path relative to server
+        designDoc.rewrites.push({
+           "from": "uuids",
+           "to": "../../../_uuids"
+        });
+        T(db.save(designDoc).ok);
         
         var xhr = CouchDB.request("GET", "/test_suite_db/_design/test/_rewrite/uuids");
-        T(xhr.status == 200);
+        T(xhr.status == 500);
         var result = JSON.parse(xhr.responseText);
-        T(result.uuids.length == 1);
-        var first = result.uuids[0];
+        T(result.error == "insecure_rewrite_rule");
+
+        run_on_modified_server(
+          [{section: "httpd",
+            key: "secure_rewrites",
+            value: "false"}],
+            function() {
+              var xhr = CouchDB.request("GET", "/test_suite_db/_design/test/_rewrite/uuids?cache=bust");
+              T(xhr.status == 200);
+              var result = JSON.parse(xhr.responseText);
+              T(result.uuids.length == 1);
+              var first = result.uuids[0];
+        });
+
   });
   
 }
\ No newline at end of file
diff --git a/src/couchdb/couch_httpd_rewrite.erl b/src/couchdb/couch_httpd_rewrite.erl
index 1e2a532f..c1869b5e 100644
--- a/src/couchdb/couch_httpd_rewrite.erl
+++ b/src/couchdb/couch_httpd_rewrite.erl
@@ -366,24 +366,34 @@ make_rule(Rule) ->
 
 parse_path(Path) ->
     {ok, SlashRE} = re:compile(<<"\\/">>),
-    path_to_list(re:split(Path, SlashRE), []).
+    path_to_list(re:split(Path, SlashRE), [], 0).
 
 %% @doc convert a path rule (from or to) to an erlang list
 %% * and path variable starting by ":" are converted
 %% in erlang atom.
-path_to_list([], Acc) ->
+path_to_list([], Acc, _DotDotCount) ->
     lists:reverse(Acc);
-path_to_list([<<>>|R], Acc) ->
-    path_to_list(R, Acc);
-path_to_list([<<"*">>|R], Acc) ->
-    path_to_list(R, [?MATCH_ALL|Acc]);
-path_to_list([P|R], Acc) ->
+path_to_list([<<>>|R], Acc, DotDotCount) ->
+    path_to_list(R, Acc, DotDotCount);
+path_to_list([<<"*">>|R], Acc, DotDotCount) ->
+    path_to_list(R, [?MATCH_ALL|Acc], DotDotCount);
+path_to_list([<<"..">>|R], Acc, DotDotCount) when DotDotCount == 2 ->
+    case couch_config:get("httpd", "secure_rewrites", "true") of
+    "false" ->
+        path_to_list(R, [<<"..">>|Acc], DotDotCount+1);
+    Else ->
+        ?LOG_INFO("insecure_rewrite_rule ~p blocked", [lists:reverse(Acc) ++ [<<"..">>] ++ R]),
+        throw({insecure_rewrite_rule, "too many ../.. segments"})
+    end;
+path_to_list([<<"..">>|R], Acc, DotDotCount) ->
+    path_to_list(R, [<<"..">>|Acc], DotDotCount+1);
+path_to_list([P|R], Acc, DotDotCount) ->
     P1 = case P of
         <<":", Var/binary>> ->
             list_to_atom(binary_to_list(Var));
         _ -> P
     end,
-    path_to_list(R, [P1|Acc]).
+    path_to_list(R, [P1|Acc], DotDotCount).
 
 encode_query(Props) ->
     Props1 = lists:foldl(fun ({K, V}, Acc) ->
-- 
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