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-rw-r--r--plugins/mod_tombstones.lua75
1 files changed, 75 insertions, 0 deletions
diff --git a/plugins/mod_tombstones.lua b/plugins/mod_tombstones.lua
new file mode 100644
index 00000000..1707c9dd
--- /dev/null
+++ b/plugins/mod_tombstones.lua
@@ -0,0 +1,75 @@
+-- TODO warn when trying to create an user before the tombstone expires
+-- e.g. via telnet or other admin interface
+local datetime = require "util.datetime";
+local errors = require "util.error";
+local jid_split = require"util.jid".split;
+local st = require "util.stanza";
+
+-- Using a map store as key-value store so that removal of all user data
+-- does not also remove the tombstone, which would defeat the point
+local graveyard = module:open_store(nil, "map");
+
+local ttl = module:get_option_number("user_tombstone_expiry", nil);
+-- Keep tombstones forever by default
+--
+-- Rationale:
+-- There is no way to be completely sure when remote services have
+-- forgotten and revoked all memberships.
+
+module:hook_global("user-deleted", function(event)
+ if event.host == module.host then
+ local ok, err = graveyard:set(nil, event.username, os.time());
+ if not ok then module:log("error", "Could store tombstone for %s: %s", event.username, err); end
+ end
+end);
+
+-- Public API
+function has_tombstone(username)
+ local tombstone, err = graveyard:get(nil, username);
+
+ if err or not tombstone then return tombstone, err; end
+
+ if ttl and tombstone + ttl < os.time() then
+ module:log("debug", "Tombstone for %s created at %s has expired", username, datetime.datetime(tombstone));
+ graveyard:set(nil, username, nil);
+ return nil;
+ end
+ return tombstone;
+end
+
+module:hook("user-registering", function(event)
+ local tombstone, err = has_tombstone(event.username);
+
+ if err then
+ event.allowed, event.error = errors.coerce(false, err);
+ return true;
+ elseif not tombstone then
+ -- Feel free
+ return;
+ end
+
+ module:log("debug", "Tombstone for %s created at %s", event.username, datetime.datetime(tombstone));
+ event.allowed = false;
+ return true;
+end);
+
+module:hook("presence/bare", function(event)
+ local origin, presence = event.origin, event.stanza;
+
+ -- We want to undo any left-over presence subscriptions and notify the former
+ -- contact that they're gone.
+ --
+ -- FIXME This leaks that the user once existed. Hard to avoid without keeping
+ -- the contact list in some form, which we don't want to do for privacy
+ -- reasons. Bloom filter perhaps?
+ if has_tombstone(jid_split(presence.attr.to)) then
+ if presence.attr.type == "probe" then
+ origin.send(st.error_reply(presence, "cancel", "gone", "User deleted"));
+ origin.send(st.presence({ type = "unsubscribed"; to = presence.attr.from; from = presence.attr.to }));
+ elseif presence.attr.type == nil or presence.attr.type == "unavailable" then
+ origin.send(st.error_reply(presence, "cancel", "gone", "User deleted"));
+ origin.send(st.presence({ type = "unsubscribe"; to = presence.attr.from; from = presence.attr.to }));
+ end
+ return true;
+ end
+end, 1);