use main() function

create-gpg-shadow-key-from-x509-cert-req.py

@@ -4,40 +4,38 @@ import cryptography.hazmat.backends
 import cryptography.hazmat.primitives.serialization
 import cryptography.x509
 import math
-import sys
 
-backend = cryptography.hazmat.backends.default_backend()
-
-with open('smartcard-app-id.hex', 'r') as f:
-    appid = int(f.read(), 16)
-
-with open('cert-request.pem', 'rb') as f:
-    req = cryptography.x509.load_pem_x509_csr(f.read(), backend)
-assert req.is_signature_valid
-
-pubnums = req.public_key().public_numbers()
-
-key_data = ['shadowed-private-key', [
-    'rsa',
-    ['n', pubnums.n],
-    ['e', pubnums.e],
-    ['shadowed', 't1-v1', [appid, 'OPENPGP.1']],
-]]
-
-def convert(data):
+def convert_to_sexp(data):
     if isinstance(data, int):
-        return convert(data.to_bytes(
+        return convert_to_sexp(data.to_bytes(
             math.ceil(data.bit_length() / 8),
             'big',
         ))
     elif isinstance(data, str):
-        return convert(data.encode())
+        return convert_to_sexp(data.encode())
     elif isinstance(data, bytes):
         return str(len(data)).encode() + b':' + data
     else:
-        return b'(' + b''.join(convert(i) for i in data) + b')'
-
-key = convert(key_data)
-
-with open('gpg-key.sexp', 'wb') as f:
-    f.write(key)
+        return b'(' + b''.join(convert_to_sexp(i) for i in data) + b')'
+
+def main(argv):
+    backend = cryptography.hazmat.backends.default_backend()
+    with open('smartcard-app-id.hex', 'r') as f:
+        appid = int(f.read(), 16)
+    with open('cert-request.pem', 'rb') as f:
+        req = cryptography.x509.load_pem_x509_csr(f.read(), backend)
+    assert req.is_signature_valid
+    pubnums = req.public_key().public_numbers()
+    key_data = ['shadowed-private-key', [
+        'rsa',
+        ['n', pubnums.n],
+        ['e', pubnums.e],
+        ['shadowed', 't1-v1', [appid, 'OPENPGP.1']],
+    ]]
+    key = convert_to_sexp(key_data)
+    with open('gpg-key.sexp', 'wb') as f:
+        f.write(key)
+
+if __name__ == '__main__':
+    import sys
+    sys.exit(main(sys.argv))