From c6e090dc9801bdaf7db9866ec85086dc687d223f Mon Sep 17 00:00:00 2001
From: Bob Mottram <bob@libreserver.org>
Date: Mon, 9 Jan 2023 22:05:58 +0000
Subject: [PATCH] Add protocol handler

---
 daemon.py    | 29 +++++++++++++++++++++++++++--
 webfinger.py | 30 ++++++++++++++++++++++++++++++
 2 files changed, 57 insertions(+), 2 deletions(-)

diff --git a/daemon.py b/daemon.py
index bd68c5960..e22994ccf 100644
--- a/daemon.py
+++ b/daemon.py
@@ -30,6 +30,7 @@ from session import set_session_for_sender
 from webfinger import webfinger_meta
 from webfinger import webfinger_node_info
 from webfinger import webfinger_lookup
+from webfinger import wellknown_protocol_handler
 from webfinger import webfinger_update
 from mastoapiv1 import masto_api_v1_response
 from metadata import meta_data_node_info
@@ -1686,7 +1687,8 @@ class PubServer(BaseHTTPRequestHandler):
         self.server.security_txt_is_active = False
         return True
 
-    def _webfinger(self, calling_domain: str, referer_domain: str) -> bool:
+    def _webfinger(self, calling_domain: str, referer_domain: str,
+                   cookie: str) -> bool:
         if not self.path.startswith('/.well-known'):
             return False
         if self.server.debug:
@@ -1723,6 +1725,29 @@ class PubServer(BaseHTTPRequestHandler):
            self.path.startswith('/friendi'):
             self._404()
             return True
+        # protocol handler. See https://fedi-to.github.io/protocol-handler.html
+        if self.path.startswith('/.well-known/protocol-handler'):
+            if referer_domain.endswidth('.onion'):
+                protocol_url = \
+                    wellknown_protocol_handler(self.path,
+                                               self.server.base_dir, 'http',
+                                               self.server.onion_domain)
+            elif referer_domain.endswidth('.i2p'):
+                protocol_url = \
+                    wellknown_protocol_handler(self.path, self.server.base_dir,
+                                               'http', self.server.i2p_domain)
+            else:
+                protocol_url = \
+                    wellknown_protocol_handler(self.path, self.server.base_dir,
+                                               self.server.http_prefix,
+                                               self.server.domain_full)
+            if protocol_url:
+                self._redirect_headers(protocol_url, cookie,
+                                       calling_domain)
+            else:
+                self._404()
+            return True
+        # nodeinfo
         if self.path.startswith('/.well-known/nodeinfo') or \
            self.path.startswith('/.well-known/x-nodeinfo'):
             if calling_domain.endswith('.onion') and \
@@ -18386,7 +18411,7 @@ class PubServer(BaseHTTPRequestHandler):
             return
 
         # get webfinger endpoint for a person
-        if self._webfinger(calling_domain, referer_domain):
+        if self._webfinger(calling_domain, referer_domain, cookie):
             fitness_performance(getreq_start_time, self.server.fitness,
                                 '_GET', 'webfinger called',
                                 self.server.debug)
diff --git a/webfinger.py b/webfinger.py
index 7235ed909..39f758018 100644
--- a/webfinger.py
+++ b/webfinger.py
@@ -252,6 +252,36 @@ def webfinger_meta(http_prefix: str, domain_full: str) -> str:
     return meta_str
 
 
+def wellknown_protocol_handler(path: str, base_dir: str,
+                               http_prefix: str, domain_full: str) -> {}:
+    """See https://fedi-to.github.io/protocol-handler.html
+    """
+    if not path.startswith('/.well-known/protocol-handler?'):
+        return None
+
+    if 'target=' in path:
+        target = path.split('target=')[1]
+        if ';' in target:
+            target = target.split(';')[0]
+        if not target:
+            return None
+        if not target.startswith('web+epicyon:'):
+            return None
+        handle = target.split(':', 1)[1].strip()
+        if handle.startswith('@'):
+            handle = handle[1:]
+        if '@' in handle:
+            nickname = handle.split('@')[0]
+            domain = handle.split('@')[1]
+        else:
+            nickname = handle
+            domain = domain_full
+        # not an open redirect
+        if domain == domain_full:
+            return http_prefix + '://' + domain_full + '/users/' + nickname
+    return None
+
+
 def webfinger_lookup(path: str, base_dir: str,
                      domain: str, onion_domain: str, i2p_domain: str,
                      port: int, debug: bool) -> {}: