CIP-0008: Allow for signing with stake key directly

In the browser, if a user specifies the stake key as part of CIP-0030
the message returned in JSON has the COSE key as the staking key.  The
verify() method correctly detects this, but the sign() method does not.
This change detects if a stake SigningKey type was passed in and if so,
sign with a stake key.

Sample behavior:

[00:28:29 01/24 thaddeuss-mbp] hacker:~/workspaces/wildtangz/cardano-vending-machine$ python3
Python 3.8.1 (v3.8.1:1b293b6006, Dec 18 2019, 14:08:53)
[Clang 6.0 (clang-600.0.57)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import pycardano
>>> skey = pycardano.key.StakeSigningKey.load('/var/folders/qz/ldnst4y96_z436s0ptw0vyp40000gn/T/cardano-vm-test-eobtvu6g/buyers/buyer.stake.skey')
>>> sign_addr = pycardano.cip.cip8.verify(pycardano.cip.cip8.sign('hello', skey, attach_cose_key=False, network=pycardano.network.Network.TESTNET))['signing_address']
>>> sign_addr
stake_test1uq5xgs974dna05tjc5pr8sfq5cc4hzludaz7z4e4vpx6p0gkrzzmd

The old behavior resulted in output of 'addr_test1vq5xgs974dna05tjc5pr8sfq5cc4hzludaz7z4e4vpx6p0gktu6v8'

[ Documentation: pydoc updates ]
[ Testing: python -m build, manual test in CLI ]
[ Code Review: #154 ]

Author: thaddeusdiamond

pycardano/cip/cip8.py

@@ -13,6 +13,8 @@
 from pycardano.key import (
     PaymentVerificationKey,
     SigningKey,
+    StakeExtendedSigningKey,
+    StakeSigningKey,
     StakeVerificationKey,
     VerificationKey,
 )
@@ -27,7 +29,9 @@ def sign(
     attach_cose_key: bool = False,
     network: Network = Network.MAINNET,
 ) -> Union[str, dict]:
-    """Sign an arbitrary message with a payment key following CIP-0008.
+    """Sign an arbitrary message with a payment or stake key following CIP-0008.
+    Note that a stake key passed in must be of type StakeSigningKey or
+    StakeExtendedSigningKey to be detected.
 
     Args:
         message (str): Message to be signed
@@ -43,11 +47,22 @@ def sign(
     # derive the verification key
     verification_key = VerificationKey.from_signing_key(signing_key)
 
+    if isinstance(signing_key, StakeSigningKey) or isinstance(
+        signing_key, StakeExtendedSigningKey
+    ):
+        address = Address(
+            payment_part=None, staking_part=verification_key.hash(), network=network
+        )
+    else:
+        address = Address(
+            payment_part=verification_key.hash(), staking_part=None, network=network
+        )
+
     # create the message object, attach verification key to the header
     msg = Sign1Message(
         phdr={
             Algorithm: EdDSA,
-            "address": Address(verification_key.hash(), network=network).to_primitive(),
+            "address": address.to_primitive(),
         },
         payload=message.encode("utf-8"),
     )

test/pycardano/test_cip8.py

@@ -1,5 +1,10 @@
 from pycardano.cip.cip8 import sign, verify
-from pycardano.key import PaymentSigningKey, PaymentVerificationKey
+from pycardano.key import (
+    PaymentSigningKey,
+    PaymentVerificationKey,
+    StakeSigningKey,
+    StakeVerificationKey,
+)
 from pycardano.network import Network
 
 SK = PaymentSigningKey.from_json(
@@ -18,6 +23,22 @@
     }"""
 )
 
+STAKE_SK = StakeSigningKey.from_json(
+    """{
+        "type": "StakeSigningKeyShelley_ed25519",
+        "description": "Stake Signing Key",
+        "cborHex": "5820ff3a330df8859e4e5f42a97fcaee73f6a00d0cf864f4bca902bd106d423f02c0"
+    }"""
+)
+
+STAKE_VK = StakeVerificationKey.from_json(
+    """{
+        "type": "StakeVerificationKeyShelley_ed25519",
+        "description": "Stake Verification Key",
+        "cborHex": "58205edaa384c658c2bd8945ae389edac0a5bd452d0cfd5d1245e3ecd540030d1e3c"
+    }"""
+)
+
 
 def test_verify_message():
 
@@ -75,6 +96,18 @@ def test_sign_message():
     )
 
 
+def test_sign_message_with_stake():
+
+    message = "Pycardano is cool."
+    signed_message = sign(
+        message, signing_key=STAKE_SK, attach_cose_key=False, network=Network.TESTNET
+    )
+    assert (
+        signed_message
+        == "84584da301276761646472657373581de04828a2dadba97ca9fd0cdc99975899470c219bdc0d828cfa6ddf6d690458205edaa384c658c2bd8945ae389edac0a5bd452d0cfd5d1245e3ecd540030d1e3ca166686173686564f452507963617264616e6f20697320636f6f6c2e5840ba1dd643f0d2e844f0509b1a7161ae4a3650f1d553fcc6e517020c5703acb70dfeea1014f2a1513baefaa2279cb151e8ff2dada6b51269cf33127d3c05829502"
+    )
+
+
 def test_sign_message_cosy_key_separate():
 
     message = "Pycardano is cool."
@@ -109,3 +142,29 @@ def test_sign_and_verify():
     assert verification["verified"]
     assert verification["message"] == "Pycardano is cool."
     assert verification["signing_address"].payment_part == VK.hash()
+
+
+def test_sign_and_verify_stake():
+
+    # try first with no cose key attached
+    message = "Pycardano is cool."
+    signed_message = sign(
+        message, signing_key=STAKE_SK, attach_cose_key=False, network=Network.TESTNET
+    )
+
+    verification = verify(signed_message)
+    assert verification["verified"]
+    assert verification["message"] == "Pycardano is cool."
+    assert verification["signing_address"].payment_part == None
+    assert verification["signing_address"].staking_part == STAKE_VK.hash()
+
+    # try again but attach cose key
+    signed_message = sign(
+        message, signing_key=STAKE_SK, attach_cose_key=True, network=Network.TESTNET
+    )
+
+    verification = verify(signed_message)
+    assert verification["verified"]
+    assert verification["message"] == "Pycardano is cool."
+    assert verification["signing_address"].payment_part == None
+    assert verification["signing_address"].staking_part == STAKE_VK.hash()