1 files changed, 143 insertions, 0 deletions
diff --git a/scripts/federation_client.py b/scripts/federation_client.py
new file mode 100644
index 0000000000..3139c61761
--- /dev/null
+++ b/scripts/federation_client.py
@@ -0,0 +1,143 @@
+import nacl.signing
+import json
+import base64
+import requests
+import sys
+import srvlookup
+
+
+def encode_base64(input_bytes):
+    """Encode bytes as a base64 string without any padding."""
+
+    input_len = len(input_bytes)
+    output_len = 4 * ((input_len + 2) // 3) + (input_len + 2) % 3 - 2
+    output_bytes = base64.b64encode(input_bytes)
+    output_string = output_bytes[:output_len].decode("ascii")
+    return output_string
+
+
+def decode_base64(input_string):
+    """Decode a base64 string to bytes inferring padding from the length of the
+    string."""
+
+    input_bytes = input_string.encode("ascii")
+    input_len = len(input_bytes)
+    padding = b"=" * (3 - ((input_len + 3) % 4))
+    output_len = 3 * ((input_len + 2) // 4) + (input_len + 2) % 4 - 2
+    output_bytes = base64.b64decode(input_bytes + padding)
+    return output_bytes[:output_len]
+
+
+def encode_canonical_json(value):
+    return json.dumps(
+         value,
+         # Encode code-points outside of ASCII as UTF-8 rather than \u escapes
+         ensure_ascii=False,
+         # Remove unecessary white space.
+         separators=(',',':'),
+         # Sort the keys of dictionaries.
+         sort_keys=True,
+         # Encode the resulting unicode as UTF-8 bytes.
+     ).encode("UTF-8")
+
+
+def sign_json(json_object, signing_key, signing_name):
+    signatures = json_object.pop("signatures", {})
+    unsigned = json_object.pop("unsigned", None)
+
+    signed = signing_key.sign(encode_canonical_json(json_object))
+    signature_base64 = encode_base64(signed.signature)
+
+    key_id = "%s:%s" % (signing_key.alg, signing_key.version)
+    signatures.setdefault(signing_name, {})[key_id] = signature_base64
+
+    json_object["signatures"] = signatures
+    if unsigned is not None:
+        json_object["unsigned"] = unsigned
+
+    return json_object
+
+
+NACL_ED25519 = "ed25519"
+
+def decode_signing_key_base64(algorithm, version, key_base64):
+    """Decode a base64 encoded signing key
+    Args:
+        algorithm (str): The algorithm the key is for (currently "ed25519").
+        version (str): Identifies this key out of the keys for this entity.
+        key_base64 (str): Base64 encoded bytes of the key.
+    Returns:
+        A SigningKey object.
+    """
+    if algorithm == NACL_ED25519:
+        key_bytes = decode_base64(key_base64)
+        key = nacl.signing.SigningKey(key_bytes)
+        key.version = version
+        key.alg = NACL_ED25519
+        return key
+    else:
+        raise ValueError("Unsupported algorithm %s" % (algorithm,))
+
+
+def read_signing_keys(stream):
+    """Reads a list of keys from a stream
+    Args:
+        stream : A stream to iterate for keys.
+    Returns:
+        list of SigningKey objects.
+    """
+    keys = []
+    for line in stream:
+        algorithm, version, key_base64 = line.split()
+        keys.append(decode_signing_key_base64(algorithm, version, key_base64))
+    return keys
+
+
+def lookup(destination, path):
+    if ":" in destination:
+        return "https://%s%s" % (destination, path)
+    else:
+        srv = srvlookup.lookup("matrix", "tcp", destination)[0]
+        return "https://%s:%d%s" % (srv.host, srv.port, path)
+
+def get_json(origin_name, origin_key, destination, path):
+    request_json = {
+        "method": "GET",
+        "uri": path,
+        "origin": origin_name,
+        "destination": destination,
+    }
+
+    signed_json = sign_json(request_json, origin_key, origin_name)
+
+    authorization_headers = []
+
+    for key, sig in signed_json["signatures"][origin_name].items():
+        authorization_headers.append(bytes(
+            "X-Matrix origin=%s,key=\"%s\",sig=\"%s\"" % (
+                origin_name, key, sig,
+            )
+        ))
+
+    result = requests.get(
+        lookup(destination, path),
+        headers={"Authorization": authorization_headers[0]},
+        verify=False,
+    )
+    return result.json()
+
+
+def main():
+    origin_name, keyfile, destination, path = sys.argv[1:]
+
+    with open(keyfile) as f:
+        key = read_signing_keys(f)[0]
+
+    result = get_json(
+        origin_name, key, destination, "/_matrix/federation/v1/" + path
+    )
+
+    json.dump(result, sys.stdout)
+
+if __name__ == "__main__":
+    main()