Merge branch 'ejabberd-pleroma-auth' into 'develop'

Add ejabberd auth document

See merge request !3074

docs/configuration/howto_ejabberd.md

+# Configuring Ejabberd (XMPP Server) to use Pleroma for authentication
+
+If you want to give your Pleroma users an XMPP (chat) account, you can configure [Ejabberd](https://github.com/processone/ejabberd) to use your Pleroma server for user authentication, automatically giving every local user an XMPP account.
+
+In general, you just have to follow the configuration described at [https://docs.ejabberd.im/admin/configuration/authentication/#external-script](https://docs.ejabberd.im/admin/configuration/authentication/#external-script). Please read this section carefully. 
+
+Copy the script below to suitable path on your system and set owner and permissions. Also do not forget adjusting `PLEROMA_HOST` and `PLEROMA_PORT`, if necessary.
+
+```bash
+cp pleroma_ejabberd_auth.py /etc/ejabberd/pleroma_ejabberd_auth.py
+chown ejabberd /etc/ejabberd/pleroma_ejabberd_auth.py
+chmod 700 /etc/ejabberd/pleroma_ejabberd_auth.py
+```
+
+Set external auth params in ejabberd.yaml file:
+
+```bash
+auth_method: [external]
+extauth_program: "python3 /etc/ejabberd/pleroma_ejabberd_auth.py"
+extauth_instances: 3
+auth_use_cache: false
+```
+
+Restart / reload your ejabberd service.
+
+After restarting your Ejabberd server, your users should now be able to connect with their Pleroma credentials.
+
+
+```python
+import sys
+import struct
+import http.client
+from base64 import b64encode
+import logging
+
+
+PLEROMA_HOST = "127.0.0.1"
+PLEROMA_PORT = "4000"
+AUTH_ENDPOINT = "/api/v1/accounts/verify_credentials"
+USER_ENDPOINT = "/api/v1/accounts"
+LOGFILE = "/var/log/ejabberd/pleroma_auth.log"
+
+logging.basicConfig(filename=LOGFILE, level=logging.INFO)
+
+
+# Pleroma functions
+def create_connection():
+    return http.client.HTTPConnection(PLEROMA_HOST, PLEROMA_PORT)
+
+
+def verify_credentials(user: str, password: str) -> bool:
+    user_pass_b64 = b64encode("{}:{}".format(
+        user, password).encode('utf-8')).decode("ascii")
+    params = {}
+    headers = {
+        "Authorization": "Basic {}".format(user_pass_b64)
+    }
+
+    try:
+        conn = create_connection()
+        conn.request("GET", AUTH_ENDPOINT, params, headers)
+
+        response = conn.getresponse()
+        if response.status == 200:
+            return True
+
+        return False
+    except Exception as e:
+        logging.info("Can not connect: %s", str(e))
+        return False
+
+
+def does_user_exist(user: str) -> bool:
+    conn = create_connection()
+    conn.request("GET", "{}/{}".format(USER_ENDPOINT, user))
+
+    response = conn.getresponse()
+    if response.status == 200:
+        return True
+
+    return False
+
+
+def auth(username: str, server: str, password: str) -> bool:
+    return verify_credentials(username, password)
+
+
+def isuser(username, server):
+    return does_user_exist(username)
+
+
+def read():
+    (pkt_size,) = struct.unpack('>H', bytes(sys.stdin.read(2), encoding='utf8'))
+    pkt = sys.stdin.read(pkt_size)
+    cmd = pkt.split(':')[0]
+    if cmd == 'auth':
+        username, server, password = pkt.split(':', 3)[1:]
+        write(auth(username, server, password))
+    elif cmd == 'isuser':
+        username, server = pkt.split(':', 2)[1:]
+        write(isuser(username, server))
+    elif cmd == 'setpass':
+        # u, s, p = pkt.split(':', 3)[1:]
+        write(False)
+    elif cmd == 'tryregister':
+        # u, s, p = pkt.split(':', 3)[1:]
+        write(False)
+    elif cmd == 'removeuser':
+        # u, s = pkt.split(':', 2)[1:]
+        write(False)
+    elif cmd == 'removeuser3':
+        # u, s, p = pkt.split(':', 3)[1:]
+        write(False)
+    else:
+        write(False)
+
+
+def write(result):
+    if result:
+        sys.stdout.write('\x00\x02\x00\x01')
+    else:
+        sys.stdout.write('\x00\x02\x00\x00')
+    sys.stdout.flush()
+
+
+if __name__ == "__main__":
+    logging.info("Starting pleroma ejabberd auth daemon...")
+    while True:
+        try:
+            read()
+        except Exception as e:
+            logging.info(
+                "Error while processing data from ejabberd %s", str(e))
+            pass
+
+```
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