read public key from X.509 certificate signing request (csr)

.gitignore

@@ -1,2 +1,2 @@
+/cert-request.pem
 /gpg-key
-/pub.pem

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

@@ -2,6 +2,7 @@
 
 import cryptography.hazmat.backends
 import cryptography.hazmat.primitives.serialization
+import cryptography.x509
 import math
 import sys
 
@@ -10,13 +11,11 @@ backend = cryptography.hazmat.backends.default_backend()
 with open('smartcard-app-id.hex', 'r') as f:
     appid = int(f.read(), 16)
 
-with open('pub.pem', 'rb') as f:
-    pubkey = cryptography.hazmat.primitives.serialization.load_pem_public_key(
-        f.read(),
-        backend,
-    )
+with open('cert-request.pem', 'rb') as f:
+    req = cryptography.x509.load_pem_x509_csr(f.read(), backend)
+assert req.is_signature_valid
 
-pubnums = pubkey.public_numbers()
+pubnums = req.public_key().public_numbers()
 
 key_data = ['shadowed-private-key', [
     'rsa',