feat(core): Implement SLIP-0025 CoinJoin accounts.

common/protob/messages-management.proto

@@ -441,6 +441,7 @@ message DoPreauthorized {
  * @start
  * @next SignTx
  * @next GetOwnershipProof
+ * @next GetPublicKey
  */
 message PreauthorizedRequest {
 }

core/.changelog.d/2289.added

@@ -0,0 +1 @@
+Add SLIP-0025 CoinJoin accounts.

core/src/apps/bitcoin/authorization.py

@@ -2,7 +2,7 @@ from micropython import const
 from typing import TYPE_CHECKING
 
 from trezor import utils, wire
-from trezor.messages import AuthorizeCoinJoin
+from trezor.messages import AuthorizeCoinJoin, GetPublicKey
 
 from apps.common import authorization
 
@@ -26,6 +26,10 @@ class CoinJoinAuthorization:
     def __init__(self, params: AuthorizeCoinJoin) -> None:
         self.params = params
 
+    def check_get_public_key(self, msg: GetPublicKey) -> bool:
+        # Check whether the current params matches the parameters of the XPUB request.
+        return self.params.address_n == msg.address_n
+
     def check_get_ownership_proof(self, msg: GetOwnershipProof) -> bool:
         # Check whether the current params matches the parameters of the request.
         coordinator = utils.empty_bytearray(1 + len(self.params.coordinator.encode()))

core/src/apps/bitcoin/authorize_coinjoin.py

@@ -2,17 +2,17 @@ from micropython import const
 from typing import TYPE_CHECKING
 
 from trezor import ui, wire
-from trezor.enums import ButtonRequestType
+from trezor.enums import ButtonRequestType, InputScriptType
 from trezor.messages import AuthorizeCoinJoin, Success
 from trezor.strings import format_amount
 from trezor.ui.layouts import confirm_action, confirm_coinjoin, confirm_metadata
 
 from apps.common import authorization, safety_checks
-from apps.common.paths import validate_path
+from apps.common.paths import PathSchema, validate_path
 
 from .authorization import FEE_RATE_DECIMALS
 from .common import BIP32_WALLET_DEPTH
-from .keychain import validate_path_against_script_type, with_keychain
+from .keychain import PATTERN_SLIP25, with_keychain
 
 if TYPE_CHECKING:
     from apps.common.coininfo import CoinInfo
@@ -47,6 +47,13 @@ async def authorize_coinjoin(
     if not msg.address_n:
         raise wire.DataError("Empty path not allowed.")
 
+    validation_path = msg.address_n + [0] * BIP32_WALLET_DEPTH
+    if (
+        not PathSchema.parse(PATTERN_SLIP25, coin.slip44).match(validation_path)
+        or msg.script_type != InputScriptType.SPENDTAPROOT
+    ) and safety_checks.is_strict():
+        raise wire.DataError("Forbidden path.")
+
     await confirm_action(
         ctx,
         "coinjoin_coordinator",
@@ -60,14 +67,12 @@ async def authorize_coinjoin(
     max_fee_per_vbyte = format_amount(msg.max_fee_per_kvbyte, 3)
     await confirm_coinjoin(ctx, coin.coin_name, msg.max_rounds, max_fee_per_vbyte)
 
-    validation_path = msg.address_n + [0] * BIP32_WALLET_DEPTH
     await validate_path(
         ctx,
         keychain,
         validation_path,
-        validate_path_against_script_type(
+        PathSchema.parse(PATTERN_SLIP25, coin.slip44).match(validation_path),
-            coin, address_n=validation_path, script_type=msg.script_type
+        msg.script_type == InputScriptType.SPENDTAPROOT,
-        ),
     )
 
     if msg.max_fee_per_kvbyte > coin.maxfee_kb:

core/src/apps/bitcoin/get_public_key.py

@@ -2,21 +2,42 @@ from typing import TYPE_CHECKING
 
 from trezor import wire
 from trezor.enums import InputScriptType
-from trezor.messages import HDNodeType, PublicKey
+from trezor.messages import AuthorizeCoinJoin, HDNodeType, PublicKey
+from trezor.ui.layouts import confirm_action
 
 from apps.common import coininfo, paths
 from apps.common.keychain import get_keychain
 
+from . import authorization
+
 if TYPE_CHECKING:
     from trezor.messages import GetPublicKey
 
+_SLIP25_PURPOSE = 10025 | paths.HARDENED
+
 
-async def get_public_key(ctx: wire.Context, msg: GetPublicKey) -> PublicKey:
+async def get_public_key(
+    ctx: wire.Context,
+    msg: GetPublicKey,
+    auth_msg: AuthorizeCoinJoin | None = None,
+) -> PublicKey:
     coin_name = msg.coin_name or "Bitcoin"
     script_type = msg.script_type or InputScriptType.SPENDADDRESS
     coin = coininfo.by_name(coin_name)
     curve_name = msg.ecdsa_curve_name or coin.curve_name
 
+    # Require confirmation to access SLIP25 paths unless already authorized.
+    if auth_msg:
+        if not authorization.from_cached_message(auth_msg).check_get_public_key(msg):
+            raise wire.ProcessError("Unauthorized operation")
+    elif msg.address_n and msg.address_n[0] == _SLIP25_PURPOSE:
+        await confirm_action(
+            ctx,
+            "confirm_coinjoin_xpub",
+            title="CoinJoin XPUB",
+            description="Do you want to allow access to your CoinJoin account?",
+        )
+
     keychain = await get_keychain(ctx, curve_name, [paths.AlwaysMatchingSchema])
 
     node = keychain.derive(msg.address_n)

core/src/apps/bitcoin/keychain.py

@@ -4,6 +4,7 @@ from typing import TYPE_CHECKING
 
 from trezor import wire
 from trezor.enums import InputScriptType
+from trezor.messages import AuthorizeCoinJoin, SignTx
 
 from apps.common import coininfo
 from apps.common.keychain import get_keychain
@@ -19,13 +20,11 @@ if TYPE_CHECKING:
     from trezor.protobuf import MessageType
 
     from trezor.messages import (
-        AuthorizeCoinJoin,
         GetAddress,
         GetOwnershipId,
         GetOwnershipProof,
         GetPublicKey,
         SignMessage,
-        SignTx,
         VerifyMessage,
     )
 
@@ -66,6 +65,10 @@ PATTERN_BIP49 = "m/49'/coin_type'/account'/change/address_index"
 PATTERN_BIP84 = "m/84'/coin_type'/account'/change/address_index"
 # BIP-86 for taproot: https://github.com/bitcoin/bips/blob/master/bip-0086.mediawiki
 PATTERN_BIP86 = "m/86'/coin_type'/account'/change/address_index"
+# SLIP-25 for CoinJoin: https://github.com/satoshilabs/slips/blob/master/slip-0025.md
+# Only account=0 and script_type=1 are supported for now.
+PATTERN_SLIP25 = "m/10025'/coin_type'/0'/1'/change/address_index"
+PATTERN_SLIP25_EXTERNAL = "m/10025'/coin_type'/0'/1'/0/address_index"
 
 # compatibility patterns, will be removed in the future
 PATTERN_GREENADDRESS_A = "m/[1,4]/address_index"
@@ -151,13 +154,16 @@ def validate_path_against_script_type(
 
     elif coin.taproot and script_type == InputScriptType.SPENDTAPROOT:
         patterns.append(PATTERN_BIP86)
+        patterns.append(PATTERN_SLIP25)
 
     return any(
         PathSchema.parse(pattern, coin.slip44).match(address_n) for pattern in patterns
     )
 
 
-def get_schemas_for_coin(coin: coininfo.CoinInfo) -> Iterable[PathSchema]:
+def get_schemas_for_coin(
+    coin: coininfo.CoinInfo, allow_slip25_internal: bool = False
+) -> Iterable[PathSchema]:
     # basic patterns
     patterns = [
         PATTERN_BIP44,
@@ -205,6 +211,10 @@ def get_schemas_for_coin(coin: coininfo.CoinInfo) -> Iterable[PathSchema]:
     # taproot patterns
     if coin.taproot:
         patterns.append(PATTERN_BIP86)
+        if allow_slip25_internal:
+            patterns.append(PATTERN_SLIP25)
+        else:
+            patterns.append(PATTERN_SLIP25_EXTERNAL)
 
     schemas = [PathSchema.parse(pattern, coin.slip44) for pattern in patterns]
 
@@ -234,10 +244,12 @@ def get_coin_by_name(coin_name: str | None) -> coininfo.CoinInfo:
 
 
 async def get_keychain_for_coin(
-    ctx: wire.Context, coin_name: str | None
+    ctx: wire.Context,
+    coin_name: str | None,
+    allow_slip25_internal: bool = False,
 ) -> tuple[Keychain, coininfo.CoinInfo]:
     coin = get_coin_by_name(coin_name)
-    schemas = get_schemas_for_coin(coin)
+    schemas = get_schemas_for_coin(coin, allow_slip25_internal)
     slip21_namespaces = [[b"SLIP-0019"], [b"SLIP-0024"]]
     keychain = await get_keychain(ctx, coin.curve_name, schemas, slip21_namespaces)
     return keychain, coin
@@ -249,7 +261,13 @@ def with_keychain(func: HandlerWithCoinInfo[MsgOut]) -> Handler[MsgIn, MsgOut]:
         msg: MsgIn,
         auth_msg: MessageType | None = None,
     ) -> MsgOut:
-        keychain, coin = await get_keychain_for_coin(ctx, msg.coin_name)
+        # Allow access to the SLIP25 internal chain (CoinJoin) for SignTx and preauthorized CoinJoin operations.
+        allow_slip25_internal = SignTx.is_type_of(msg) or (
+            auth_msg is not None and AuthorizeCoinJoin.is_type_of(auth_msg)
+        )
+        keychain, coin = await get_keychain_for_coin(
+            ctx, msg.coin_name, allow_slip25_internal
+        )
         if auth_msg:
             auth_obj = authorization.from_cached_message(auth_msg)
             return await func(ctx, msg, keychain, coin, auth_obj)

core/src/apps/common/authorization.py

@@ -6,7 +6,11 @@ from trezor.enums import MessageType
 from trezor.utils import ensure
 
 WIRE_TYPES: dict[int, tuple[int, ...]] = {
-    MessageType.AuthorizeCoinJoin: (MessageType.SignTx, MessageType.GetOwnershipProof),
+    MessageType.AuthorizeCoinJoin: (
+        MessageType.SignTx,
+        MessageType.GetOwnershipProof,
+        MessageType.GetPublicKey,
+    ),
 }