upload-pack: disable object filtering when disabled by config

When upload-pack gained partial clone support (v2.17.0-rc0~132^2~12,
2017-12-08), it was guarded by the uploadpack.allowFilter config item
to allow server operators to control when they start supporting it.

That config item didn't go far enough, though: it controls whether the
'filter' capability is advertised, but if a (custom) client ignores
the capability advertisement and passes a filter specification anyway,
the server would handle that despite allowFilter being false.

This is particularly significant if a security bug is discovered in
this new experimental partial clone code.  Installations without
uploadpack.allowFilter ought not to be affected since they don't
intend to support partial clone, but they would be swept up into being
vulnerable.

Simplify and limit the attack surface by making uploadpack.allowFilter
disable the feature, not just the advertisement of it.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Documentation/config.txt b/Documentation/config.txt
index e528210c67a4c66bef22e560b425d3bb3bb9f2e6..7b67afc674b773152def4f97948406a84184dcd6 100644 (file)
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -3270,7 +3270,7 @@ uploadpack.packObjectsHook::
        stdout.
 
 uploadpack.allowFilter::
-       If this option is set, `upload-pack` will advertise partial
+       If this option is set, `upload-pack` will support partial
        clone and partial fetch object filtering.
 +
 Note that this configuration variable is ignored if it is seen in the

diff --git a/upload-pack.c b/upload-pack.c
index 15b66051ce9a03aabb1b57f3839235f2ad9bdfb3..7217f3bd816fa0283691856c727a8d8a6b134cf7 100644 (file)
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -68,7 +68,7 @@ static int stateless_rpc;
 static const char *pack_objects_hook;
 
 static int filter_capability_requested;
-static int filter_advertise;
+static int allow_filter;
 static struct list_objects_filter_options filter_options;
 
 static void reset_timeout(void)
@@ -845,7 +845,7 @@ static void receive_needs(void)
                        no_progress = 1;
                if (parse_feature_request(features, "include-tag"))
                        use_include_tag = 1;
-               if (parse_feature_request(features, "filter"))
+               if (allow_filter && parse_feature_request(features, "filter"))
                        filter_capability_requested = 1;
 
                o = parse_object(&oid_buf);
@@ -975,7 +975,7 @@ static int send_ref(const char *refname, const struct object_id *oid,
                                     " allow-reachable-sha1-in-want" : "",
                             stateless_rpc ? " no-done" : "",
                             symref_info.buf,
-                            filter_advertise ? " filter" : "",
+                            allow_filter ? " filter" : "",
                             git_user_agent_sanitized());
                strbuf_release(&symref_info);
        } else {
@@ -1055,7 +1055,7 @@ static int upload_pack_config(const char *var, const char *value, void *unused)
                if (!strcmp("uploadpack.packobjectshook", var))
                        return git_config_string(&pack_objects_hook, var, value);
        } else if (!strcmp("uploadpack.allowfilter", var)) {
-               filter_advertise = git_config_bool(var, value);
+               allow_filter = git_config_bool(var, value);
        }
        return parse_hide_refs_config(var, value, "uploadpack");
 }