Support NUT-XX (signatures on quotes) for mint and wallet side (#670)

* nut-19 sign mint quote

* ephemeral key for quote

* `mint` adjustments + crypto/nut19.py

* wip: mint side working

* fix import

* post-merge fixups

* more fixes

* make format

* move nut19 to nuts directory

* `key` -> `privkey` and `pubkey`

* make format

* mint_info method for nut-19 support

* fix tests imports

* fix signature missing positional argument + fix db migration format not correctly escaped + pass in NUT-19 keypair to `request_mint` `request_mint_with_callback`

* make format

* fix `get_invoice_status`

* rename to xx

* nutxx -> nut20

* mypy

* remove `mint_quote_signature_required` as per spec

* wip edits

* clean up

* fix tests

* fix deprecated api tests

* fix redis tests

* fix cache tests

* fix regtest mint external

* fix mint regtest

* add test without signature

* test pubkeys in quotes

* wip

* add compat

---------

Co-authored-by: callebtc <93376500+callebtc@users.noreply.github.com>

cashu/core/base.py

@@ -413,6 +413,8 @@ class MintQuote(LedgerEvent):
     paid_time: Union[int, None] = None
     expiry: Optional[int] = None
     mint: Optional[str] = None
+    privkey: Optional[str] = None
+    pubkey: Optional[str] = None
 
     @classmethod
     def from_row(cls, row: Row):
@@ -436,6 +438,8 @@ def from_row(cls, row: Row):
             state=MintQuoteState(row["state"]),
             created_time=created_time,
             paid_time=paid_time,
+            pubkey=row["pubkey"] if "pubkey" in row.keys() else None,
+            privkey=row["privkey"] if "privkey" in row.keys() else None,
         )
 
     @classmethod
@@ -458,6 +462,7 @@ def from_resp_wallet(cls, mint_quote_resp, mint: str, amount: int, unit: str):
             mint=mint,
             expiry=mint_quote_resp.expiry,
             created_time=int(time.time()),
+            pubkey=mint_quote_resp.pubkey,
         )
 
     @property

cashu/core/errors.py

@@ -96,3 +96,19 @@ class QuoteNotPaidError(CashuError):
 
     def __init__(self):
         super().__init__(self.detail, code=2001)
+
+
+class QuoteSignatureInvalidError(CashuError):
+    detail = "Signature for mint request invalid"
+    code = 20008
+
+    def __init__(self):
+        super().__init__(self.detail, code=20008)
+
+
+class QuoteRequiresPubkeyError(CashuError):
+    detail = "Pubkey required for mint quote"
+    code = 20009
+
+    def __init__(self):
+        super().__init__(self.detail, code=20009)

cashu/core/models.py

@@ -128,21 +128,25 @@ class PostMintQuoteRequest(BaseModel):
     description: Optional[str] = Field(
         default=None, max_length=settings.mint_max_request_length
     )  # invoice description
+    pubkey: Optional[str] = Field(
+        default=None, max_length=settings.mint_max_request_length
+    )  # NUT-20 quote lock pubkey
 
 
 class PostMintQuoteResponse(BaseModel):
     quote: str  # quote id
     request: str  # input payment request
-    paid: Optional[bool]  # DEPRECATED as per NUT-04 PR #141
-    state: Optional[str]  # state of the quote
+    state: Optional[str]  # state of the quote (optional for backwards compat)
     expiry: Optional[int]  # expiry of the quote
+    pubkey: Optional[str] = None  # NUT-20 quote lock pubkey
+    paid: Optional[bool] = None  # DEPRECATED as per NUT-04 PR #141
 
     @classmethod
-    def from_mint_quote(self, mint_quote: MintQuote) -> "PostMintQuoteResponse":
+    def from_mint_quote(cls, mint_quote: MintQuote) -> "PostMintQuoteResponse":
         to_dict = mint_quote.dict()
         # turn state into string
         to_dict["state"] = mint_quote.state.value
-        return PostMintQuoteResponse.parse_obj(to_dict)
+        return cls.parse_obj(to_dict)
 
 
 # ------- API: MINT -------
@@ -153,6 +157,9 @@ class PostMintRequest(BaseModel):
     outputs: List[BlindedMessage] = Field(
         ..., max_items=settings.mint_max_request_length
     )
+    signature: Optional[str] = Field(
+        default=None, max_length=settings.mint_max_request_length
+    )  # NUT-20 quote signature
 
 
 class PostMintResponse(BaseModel):

cashu/core/nuts/nut20.py

@@ -0,0 +1,41 @@
+from hashlib import sha256
+from typing import List
+
+from ..base import BlindedMessage
+from ..crypto.secp import PrivateKey, PublicKey
+
+
+def generate_keypair() -> tuple[str, str]:
+    privkey = PrivateKey()
+    assert privkey.pubkey
+    pubkey = privkey.pubkey
+    return privkey.serialize(), pubkey.serialize(True).hex()
+
+
+def construct_message(quote_id: str, outputs: List[BlindedMessage]) -> bytes:
+    serialized_outputs = b"".join([o.B_.encode("utf-8") for o in outputs])
+    msgbytes = sha256(quote_id.encode("utf-8") + serialized_outputs).digest()
+    return msgbytes
+
+
+def sign_mint_quote(
+    quote_id: str,
+    outputs: List[BlindedMessage],
+    private_key: str,
+) -> str:
+    privkey = PrivateKey(bytes.fromhex(private_key), raw=True)
+    msgbytes = construct_message(quote_id, outputs)
+    sig = privkey.schnorr_sign(msgbytes, None, raw=True)
+    return sig.hex()
+
+
+def verify_mint_quote(
+    quote_id: str,
+    outputs: List[BlindedMessage],
+    public_key: str,
+    signature: str,
+) -> bool:
+    pubkey = PublicKey(bytes.fromhex(public_key), raw=True)
+    msgbytes = construct_message(quote_id, outputs)
+    sig = bytes.fromhex(signature)
+    return pubkey.schnorr_verify(msgbytes, sig, None, raw=True)

cashu/core/nuts.py → cashu/core/nuts/nuts.py

@@ -13,3 +13,4 @@
 MPP_NUT = 15
 WEBSOCKETS_NUT = 17
 CACHE_NUT = 19
+MINT_QUOTE_SIGNATURE_NUT = 20

cashu/core/p2pk.py

@@ -50,22 +50,3 @@ def verify_schnorr_signature(
     return pubkey.schnorr_verify(
         hashlib.sha256(message).digest(), signature, None, raw=True
     )
-
-
-if __name__ == "__main__":
-    # generate keys
-    private_key_bytes = b"12300000000000000000000000000123"
-    private_key = PrivateKey(private_key_bytes, raw=True)
-    print(private_key.serialize())
-    public_key = private_key.pubkey
-    assert public_key
-    print(public_key.serialize().hex())
-
-    # sign message (=pubkey)
-    message = public_key.serialize()
-    signature = private_key.ecdsa_serialize(private_key.ecdsa_sign(message))
-    print(signature.hex())
-
-    # verify
-    pubkey_verify = PublicKey(message, raw=True)
-    print(public_key.ecdsa_verify(message, pubkey_verify.ecdsa_deserialize(signature)))

cashu/mint/crud.py

@@ -421,8 +421,8 @@ async def store_mint_quote(
         await (conn or db).execute(
             f"""
             INSERT INTO {db.table_with_schema('mint_quotes')}
-            (quote, method, request, checking_id, unit, amount, paid, issued, state, created_time, paid_time)
-            VALUES (:quote, :method, :request, :checking_id, :unit, :amount, :paid, :issued, :state, :created_time, :paid_time)
+            (quote, method, request, checking_id, unit, amount, paid, issued, state, created_time, paid_time, pubkey)
+            VALUES (:quote, :method, :request, :checking_id, :unit, :amount, :paid, :issued, :state, :created_time, :paid_time, :pubkey)
             """,
             {
                 "quote": quote.quote,
@@ -440,6 +440,7 @@ async def store_mint_quote(
                 "paid_time": db.to_timestamp(
                     db.timestamp_from_seconds(quote.paid_time) or ""
                 ),
+                "pubkey": quote.pubkey or ""
             },
         )
 

cashu/mint/features.py

@@ -5,13 +5,14 @@
     MeltMethodSetting,
     MintMethodSetting,
 )
-from ..core.nuts import (
+from ..core.nuts.nuts import (
     CACHE_NUT,
     DLEQ_NUT,
     FEE_RETURN_NUT,
     HTLC_NUT,
     MELT_NUT,
     MINT_NUT,
+    MINT_QUOTE_SIGNATURE_NUT,
     MPP_NUT,
     P2PK_NUT,
     RESTORE_NUT,
@@ -75,6 +76,7 @@ def add_supported_features(
         mint_features[P2PK_NUT] = supported_dict
         mint_features[DLEQ_NUT] = supported_dict
         mint_features[HTLC_NUT] = supported_dict
+        mint_features[MINT_QUOTE_SIGNATURE_NUT] = supported_dict
         return mint_features
 
     def add_mpp_features(

cashu/mint/ledger.py

@@ -38,6 +38,7 @@
     LightningError,
     NotAllowedError,
     QuoteNotPaidError,
+    QuoteSignatureInvalidError,
     TransactionError,
 )
 from ..core.helpers import sum_proofs
@@ -459,6 +460,7 @@ async def mint_quote(self, quote_request: PostMintQuoteRequest) -> MintQuote:
             state=MintQuoteState.unpaid,
             created_time=int(time.time()),
             expiry=expiry,
+            pubkey=quote_request.pubkey,
         )
         await self.crud.store_mint_quote(quote=quote, db=self.db)
         await self.events.submit(quote)
@@ -518,13 +520,14 @@ async def mint(
         *,
         outputs: List[BlindedMessage],
         quote_id: str,
+        signature: Optional[str] = None,
     ) -> List[BlindedSignature]:
         """Mints new coins if quote with `quote_id` was paid. Ingest blind messages `outputs` and returns blind signatures `promises`.
 
         Args:
             outputs (List[BlindedMessage]): Outputs (blinded messages) to sign.
             quote_id (str): Mint quote id.
-            keyset (Optional[MintKeyset], optional): Keyset to use. If not provided, uses active keyset. Defaults to None.
+            witness (Optional[str], optional): NUT-19 witness signature. Defaults to None.
 
         Raises:
             Exception: Validation of outputs failed.
@@ -536,7 +539,6 @@ async def mint(
         Returns:
             List[BlindedSignature]: Signatures on the outputs.
         """
-
         await self._verify_outputs(outputs)
         sum_amount_outputs = sum([b.amount for b in outputs])
         # we already know from _verify_outputs that all outputs have the same unit because they have the same keyset
@@ -549,6 +551,7 @@ async def mint(
             raise TransactionError("Mint quote already issued.")
         if not quote.paid:
             raise QuoteNotPaidError()
+
         previous_state = quote.state
         await self.db_write._set_mint_quote_pending(quote_id=quote_id)
         try:
@@ -558,6 +561,9 @@ async def mint(
                 raise TransactionError("amount to mint does not match quote amount")
             if quote.expiry and quote.expiry > int(time.time()):
                 raise TransactionError("quote expired")
+            if not self._verify_mint_quote_witness(quote, outputs, signature):
+                raise QuoteSignatureInvalidError()
+
             promises = await self._generate_promises(outputs)
         except Exception as e:
             await self.db_write._unset_mint_quote_pending(

cashu/mint/migrations.py

@@ -838,3 +838,12 @@ async def m022_quote_set_states_to_values(db: Database):
             await conn.execute(
                 f"UPDATE {db.table_with_schema('mint_quotes')} SET state = '{mint_quote_states.value}' WHERE state = '{mint_quote_states.name}'"
             )
+
+async def m023_add_key_to_mint_quote_table(db: Database):
+    async with db.connect() as conn:
+        await conn.execute(
+            f"""
+                ALTER TABLE {db.table_with_schema('mint_quotes')}
+                ADD COLUMN pubkey TEXT DEFAULT NULL
+            """
+        )

cashu/mint/router.py

@@ -174,6 +174,7 @@ async def mint_quote(
         paid=quote.paid,  # deprecated
         state=quote.state.value,
         expiry=quote.expiry,
+        pubkey=quote.pubkey,
     )
     logger.trace(f"< POST /v1/mint/quote/bolt11: {resp}")
     return resp
@@ -198,6 +199,7 @@ async def get_mint_quote(request: Request, quote: str) -> PostMintQuoteResponse:
         paid=mint_quote.paid,  # deprecated
         state=mint_quote.state.value,
         expiry=mint_quote.expiry,
+        pubkey=mint_quote.pubkey,
     )
     logger.trace(f"< GET /v1/mint/quote/bolt11/{quote}")
     return resp
@@ -251,7 +253,9 @@ async def mint(
     """
     logger.trace(f"> POST /v1/mint/bolt11: {payload}")
 
-    promises = await ledger.mint(outputs=payload.outputs, quote_id=payload.quote)
+    promises = await ledger.mint(
+        outputs=payload.outputs, quote_id=payload.quote, signature=payload.signature
+    )
     blinded_signatures = PostMintResponse(signatures=promises)
     logger.trace(f"< POST /v1/mint/bolt11: {blinded_signatures}")
     return blinded_signatures

cashu/mint/verification.py

@@ -7,6 +7,7 @@
     BlindedSignature,
     Method,
     MintKeyset,
+    MintQuote,
     Proof,
     Unit,
 )
@@ -20,6 +21,7 @@
     TransactionError,
     TransactionUnitError,
 )
+from ..core.nuts import nut20
 from ..core.settings import settings
 from ..lightning.base import LightningBackend
 from ..mint.crud import LedgerCrud
@@ -277,3 +279,16 @@ def _verify_and_get_unit_method(
             )
 
         return unit, method
+
+    def _verify_mint_quote_witness(
+        self,
+        quote: MintQuote,
+        outputs: List[BlindedMessage],
+        signature: Optional[str],
+    ) -> bool:
+        """Verify signature on quote id and outputs"""
+        if not quote.pubkey:
+            return True
+        if not signature:
+            return False
+        return nut20.verify_mint_quote(quote.quote, outputs, quote.pubkey, signature)

cashu/wallet/cli/cli.py

@@ -348,7 +348,9 @@ def mint_invoice_callback(msg: JSONRPCNotficationParams):
             try:
                 asyncio.run(
                     wallet.mint(
-                        int(amount), split=optional_split, quote_id=mint_quote.quote
+                        int(amount),
+                        split=optional_split,
+                        quote_id=mint_quote.quote,
                     )
                 )
                 # set paid so we won't react to any more callbacks
@@ -402,7 +404,9 @@ def mint_invoice_callback(msg: JSONRPCNotficationParams):
                 mint_quote_resp = await wallet.get_mint_quote(mint_quote.quote)
                 if mint_quote_resp.state == MintQuoteState.paid.value:
                     await wallet.mint(
-                        amount, split=optional_split, quote_id=mint_quote.quote
+                        amount,
+                        split=optional_split,
+                        quote_id=mint_quote.quote,
                     )
                     paid = True
                 else:
@@ -423,7 +427,14 @@ def mint_invoice_callback(msg: JSONRPCNotficationParams):
 
     # user paid invoice before and wants to check the quote id
     elif amount and id:
-        await wallet.mint(amount, split=optional_split, quote_id=id)
+        quote = await get_bolt11_mint_quote(wallet.db, quote=id)
+        if not quote:
+            raise Exception("Quote not found")
+        await wallet.mint(
+            amount,
+            split=optional_split,
+            quote_id=quote.quote,
+        )
 
     # close open subscriptions so we can exit
     try:
@@ -921,11 +932,13 @@ async def invoices(ctx, paid: bool, unpaid: bool, pending: bool, mint: bool):
         print("No invoices found.")
         return
 
-    async def _try_to_mint_pending_invoice(amount: int, id: str) -> Optional[MintQuote]:
+    async def _try_to_mint_pending_invoice(
+        amount: int, quote_id: str
+    ) -> Optional[MintQuote]:
         try:
-            proofs = await wallet.mint(amount, id)
+            proofs = await wallet.mint(amount, quote_id)
             print(f"Received {wallet.unit.str(sum_proofs(proofs))}")
-            return await get_bolt11_mint_quote(db=wallet.db, quote=id)
+            return await get_bolt11_mint_quote(db=wallet.db, quote=quote_id)
         except Exception as e:
             logger.error(f"Could not mint pending invoice: {e}")
             return None