feat(core): Support multisig_xpub_magic in GetPublicKey.

core/.changelog.d/2658.added

@@ -0,0 +1 @@
+Add multisig_xpub_magic option to GetPublicKey.

core/src/apps/bitcoin/common.py

@@ -271,3 +271,30 @@ def descriptor_checksum(desc: str) -> str:
     for j in range(0, 8):
         ret[j] = CHECKSUM_CHARSET[(c >> (5 * (7 - j))) & 31]
     return "".join(ret)
+
+
+def get_xpub_magic(
+    coin: CoinInfo,
+    script_type: InputScriptType,
+    ignore_xpub_magic: bool | None,
+    is_multisig: bool | None,
+) -> int:
+    from trezor.enums import InputScriptType
+
+    xpub_magic = None
+    if not ignore_xpub_magic:
+        # Handle SegWit v0 script types.
+        # When coin.segwit is true, cointool.py guarantees that the corresponding xpub_magic_* attributes not None.
+        if not is_multisig:
+            if script_type == InputScriptType.SPENDP2SHWITNESS:
+                xpub_magic = coin.xpub_magic_segwit_p2sh
+            elif script_type == InputScriptType.SPENDWITNESS:
+                xpub_magic = coin.xpub_magic_segwit_native
+        else:
+            if script_type == InputScriptType.SPENDWITNESS:
+                xpub_magic = coin.xpub_magic_multisig_segwit_native
+            elif script_type == InputScriptType.SPENDP2SHWITNESS:
+                xpub_magic = coin.xpub_magic_multisig_segwit_p2sh
+
+    # SPENDADDRESS, SPENDMULTISIG, SPENDTAPROOT, ignore_xpub_magic or fallback.
+    return xpub_magic or coin.xpub_magic

core/src/apps/bitcoin/get_address.py

@@ -39,6 +39,7 @@ async def get_address(msg: GetAddress, keychain: Keychain, coin: CoinInfo) -> Ad
     from apps.common.paths import address_n_to_str, validate_path
 
     from . import addresses
+    from .common import get_xpub_magic
     from .keychain import (
         address_n_to_name_or_unknown,
         validate_path_against_script_type,
@@ -72,20 +73,7 @@ async def get_address(msg: GetAddress, keychain: Keychain, coin: CoinInfo) -> Ad
         address_case_sensitive = False  # cashaddr address
 
     mac: bytes | None = None
-    multisig_xpub_magic = coin.xpub_magic
+    if not multisig:
-    if multisig:
-        if coin.segwit and not msg.ignore_xpub_magic:
-            if (
-                script_type == InputScriptType.SPENDWITNESS
-                and coin.xpub_magic_multisig_segwit_native is not None
-            ):
-                multisig_xpub_magic = coin.xpub_magic_multisig_segwit_native
-            elif (
-                script_type == InputScriptType.SPENDP2SHWITNESS
-                and coin.xpub_magic_multisig_segwit_p2sh is not None
-            ):
-                multisig_xpub_magic = coin.xpub_magic_multisig_segwit_p2sh
-    else:
         # Attach a MAC for single-sig addresses, but only if the path is standard
         # or if the user explicitly confirms a non-standard path.
         if msg.show_display or (
@@ -97,6 +85,10 @@ async def get_address(msg: GetAddress, keychain: Keychain, coin: CoinInfo) -> Ad
     if msg.show_display:
         path = address_n_to_str(address_n)
         if multisig:
+            multisig_xpub_magic = get_xpub_magic(
+                coin, script_type, msg.ignore_xpub_magic, is_multisig=True
+            )
+
             if multisig.nodes:
                 pubnodes = multisig.nodes
             else:

core/src/apps/bitcoin/get_public_key.py

@@ -10,20 +10,20 @@ if TYPE_CHECKING:
 async def get_public_key(
     msg: GetPublicKey, auth_msg: MessageType | None = None
 ) -> PublicKey:
-    from trezor import TR, wire
+    from trezor import TR
     from trezor.enums import InputScriptType
     from trezor.messages import HDNodeType, PublicKey, UnlockPath
 
     from apps.common import coininfo, paths
     from apps.common.keychain import FORBIDDEN_KEY_PATH, get_keychain
 
+    from .common import get_xpub_magic, sanitize_input_script_type
+
     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
     address_n = msg.address_n  # local_cache_attribute
-    ignore_xpub_magic = msg.ignore_xpub_magic  # local_cache_attribute
-    xpub_magic = coin.xpub_magic  # local_cache_attribute
 
     if address_n and address_n[0] == paths.SLIP25_PURPOSE:
         # UnlockPath is required to access SLIP25 paths.
@@ -38,36 +38,13 @@ async def get_public_key(
 
     node = keychain.derive(address_n)
 
-    if (
+    sanitize_input_script_type(coin, script_type)
-        script_type
+
-        in (
-            InputScriptType.SPENDADDRESS,
-            InputScriptType.SPENDMULTISIG,
-            InputScriptType.SPENDTAPROOT,
-        )
-        and xpub_magic is not None
-    ):
-        node_xpub = node.serialize_public(xpub_magic)
-    elif (
-        coin.segwit
-        and script_type == InputScriptType.SPENDP2SHWITNESS
-        and (ignore_xpub_magic or coin.xpub_magic_segwit_p2sh is not None)
-    ):
-        assert coin.xpub_magic_segwit_p2sh is not None
     node_xpub = node.serialize_public(
-            xpub_magic if ignore_xpub_magic else coin.xpub_magic_segwit_p2sh
+        get_xpub_magic(
+            coin, script_type, msg.ignore_xpub_magic, msg.multisig_xpub_magic
         )
-    elif (
-        coin.segwit
-        and script_type == InputScriptType.SPENDWITNESS
-        and (ignore_xpub_magic or coin.xpub_magic_segwit_native is not None)
-    ):
-        assert coin.xpub_magic_segwit_native is not None
-        node_xpub = node.serialize_public(
-            xpub_magic if ignore_xpub_magic else coin.xpub_magic_segwit_native
     )
-    else:
-        raise wire.DataError("Invalid combination of coin and script_type")
 
     pubkey = node.public_key()
     # For curve25519 and ed25519, the public key has the prefix 0x00, as specified by SLIP-10. However, since this prefix is non-standard, it may be removed in the future.
@@ -79,7 +56,7 @@ async def get_public_key(
         public_key=pubkey,
     )
     descriptor = _xpub_descriptor(
-        node, xpub_magic, address_n, script_type, keychain.root_fingerprint()
+        node, coin.xpub_magic, address_n, script_type, keychain.root_fingerprint()
     )
 
     if msg.show_display: