DNS lookup strategy

README.md

@@ -5,8 +5,13 @@ mxisd is an implementation of the Matrix Identity Server which aims to provide a
 to [sydent](https://github.com/matrix-org/sydent) and an external validation implementation of the
 [Identity Service API](http://matrix.org/docs/spec/identity_service/unstable.html).
 
-mxisd is currently in read-only mode with the following lookup strategies in priority order:
+mxisd is currently in read-only mode and use a priority lookup strategy with several providers.
+
+Given the 3PID `john.doe@example.org`, the following would be performed in priority order until a mapping is found:
 - LDAP: lookup the Matrix ID from an configurable attribute.
+- DNS: lookup another Identity Server using the domain part of an e-mail and:
+  - Look for a SRV record under `_identity._matrix._tcp.example.org`
+  - Lookup using the base domain name `example.org`
 - Forwarder: Proxy the request to other identity servers (`matrix.org` and `vector.im` currently hardcoded).
 
 # Quick start
@@ -23,7 +28,7 @@ cd mxisd
 ## Configure
 1. Create a new local config: `cp application.example.yaml application.yaml`
 - Edit `application.yaml` to your needs - at least provide the LDAP attributes
-- Edit an entity in your LDAP database and set the configure attribute with a Matrix ID (e.g. @johndoe:example.org)
+- Edit an entity in your LDAP database and set the configure attribute with a Matrix ID (e.g. `@john.doe:example.org`)
 
 ## Run
 Start the server in foreground:
@@ -38,7 +43,7 @@ curl http://localhost:8090/_matrix/identity/api/v1/pubkey/ed25519:0
 
 Validate your LDAP config and binding info (replace the e-mail):
 ```
-curl http://localhost:8090/_matrix/identity/api/v1/lookup?medium=email&address=johndoe@example.org
+curl "http://localhost:8090/_matrix/identity/api/v1/lookup?medium=email&address=john.doe@example.org"
 ```
 
 If you plan on testing the integration with a homeserver, you will need to run an HTTPS reverse proxy in front of it
@@ -58,4 +63,3 @@ as the homeserver implementation seems to require a HTTPS connection to an ID se
 # TODO
 - Deb package
 - Docker container
-- Auto-discovery of matrix ids based on server name and username-like attribute

build.gradle

@@ -51,6 +51,9 @@ dependencies {
     // LDAP connector
     compile 'org.apache.directory.api:api-all:1.0.0-RC2'
 
+    // DNS lookups
+    compile 'dnsjava:dnsjava:2.1.8'
+
     testCompile 'junit:junit:4.12'
 }
 

src/main/groovy/io/kamax/mxisd/lookup/DnsLookupProvider.groovy

@@ -0,0 +1,86 @@
+/*
+ * mxisd - Matrix Identity Server Daemon
+ * Copyright (C) 2017 Maxime Dor
+ *
+ * https://max.kamax.io/
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package io.kamax.mxisd.lookup
+
+import io.kamax.mxisd.api.ThreePidType
+import org.slf4j.Logger
+import org.slf4j.LoggerFactory
+import org.springframework.stereotype.Component
+import org.xbill.DNS.Lookup
+import org.xbill.DNS.SRVRecord
+import org.xbill.DNS.Type
+
+@Component
+class DnsLookupProvider extends RemoteIdentityServerProvider {
+
+    private Logger log = LoggerFactory.getLogger(DnsLookupProvider.class)
+
+    @Override
+    int getPriority() {
+        return 10
+    }
+
+    @Override
+    Optional<?> find(ThreePidType type, String threePid) {
+        log.info("Performing DNS lookup for {}", threePid)
+        if (ThreePidType.email != type) {
+            log.info("Skipping unsupported type {} for {}", type, threePid)
+            return Optional.empty()
+        }
+
+        String domain = threePid.substring(threePid.lastIndexOf("@") + 1)
+        log.info("Domain name for {}: {}", threePid, domain)
+
+        log.info("Performing SRV lookup")
+        String lookupDns = "_identity._matrix._tcp." + domain
+        log.info("Lookup name: {}", lookupDns)
+
+        SRVRecord[] records = (SRVRecord[]) new Lookup(lookupDns, Type.SRV).run()
+        if (records != null) {
+            Arrays.sort(records, new Comparator<SRVRecord>() {
+
+                @Override
+                int compare(SRVRecord o1, SRVRecord o2) {
+                    return Integer.compare(o1.getPriority(), o2.getPriority())
+                }
+
+            })
+
+            for (SRVRecord record : records) {
+                log.info("Found SRV record: {}", record.toString())
+                String baseUrl = (record.getPort() != 80 ? "https://" : "http://") + record.getTarget().toString(true)
+                Optional<?> answer = find(baseUrl, type, threePid)
+                if (answer.isPresent()) {
+                    return answer
+                } else {
+                    log.info("No mapping found at {}", baseUrl)
+                }
+            }
+        } else {
+            log.info("No SRV record for {}", lookupDns)
+        }
+
+        log.info("Performing basic lookup using domain name {}", domain)
+        String baseUrl = "https://" + domain
+        return find(baseUrl, type, threePid)
+    }
+
+}

src/main/groovy/io/kamax/mxisd/lookup/RemoteIdentityServerProvider.groovy

@@ -0,0 +1,58 @@
+/*
+ * mxisd - Matrix Identity Server Daemon
+ * Copyright (C) 2017 Maxime Dor
+ *
+ * https://max.kamax.io/
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package io.kamax.mxisd.lookup
+
+import groovy.json.JsonException
+import groovy.json.JsonSlurper
+import io.kamax.mxisd.api.ThreePidType
+import org.slf4j.Logger
+import org.slf4j.LoggerFactory
+
+abstract class RemoteIdentityServerProvider implements ThreePidProvider {
+
+    private Logger log = LoggerFactory.getLogger(RemoteIdentityServerProvider.class)
+    private JsonSlurper json = new JsonSlurper()
+
+    Optional<?> find(String remote, ThreePidType type, String threePid) {
+        log.info("Looking up {} 3PID {} using {}", type, threePid, remote)
+
+        HttpURLConnection rootSrvConn = (HttpURLConnection) new URL(
+                "${remote}/_matrix/identity/api/v1/lookup?medium=${type}&address=${threePid}"
+        ).openConnection()
+
+        try {
+            def output = json.parseText(rootSrvConn.getInputStream().getText())
+            if (output['address'] != null) {
+                return Optional.of(output)
+            }
+
+            log.info("Empty 3PID mapping from {}", remote)
+            return Optional.empty()
+        } catch (IOException e) {
+            log.warn("Error looking up 3PID mapping {}: {}", threePid, e.getMessage())
+            return Optional.empty()
+        } catch (JsonException e) {
+            log.warn("Invalid JSON answer from {}", remote)
+            return Optional.empty()
+        }
+    }
+
+}

src/main/groovy/io/kamax/mxisd/lookup/RootProvider.groovy

@@ -20,15 +20,13 @@
 
 package io.kamax.mxisd.lookup
 
-import groovy.json.JsonSlurper
 import io.kamax.mxisd.api.ThreePidType
 import org.springframework.stereotype.Component
 
 @Component
-class RootProvider implements ThreePidProvider {
+class RootProvider extends RemoteIdentityServerProvider {
 
     private List<String> roots = Arrays.asList("https://matrix.org", "https://vector.im")
-    private JsonSlurper json = new JsonSlurper()
 
     @Override
     int getPriority() {
@@ -38,13 +36,9 @@ class RootProvider implements ThreePidProvider {
     @Override
     Optional<?> find(ThreePidType type, String threePid) {
         for (String root : roots) {
-            HttpURLConnection rootSrvConn = (HttpURLConnection) new URL(
-                    "${root}/_matrix/identity/api/v1/lookup?medium=${type}&address=${threePid}"
-            ).openConnection()
-
-            def output = json.parseText(rootSrvConn.getInputStream().getText())
-            if (output['address'] != null) {
-                return Optional.of(output)
+            Optional<?> answer = find(root, type, threePid)
+            if (answer.isPresent()) {
+                return answer
             }
         }