From 4baab751a43338ef9c0d7a3eb78a85c02f25f020 Mon Sep 17 00:00:00 2001
From: "Peter D. Gray" <peter@conalgo.com>
Date: Tue, 3 Sep 2019 16:50:47 +0200
Subject: [PATCH] Add multisig support for Coldcard plugin

-----

Squashed commit of the following:

commit 69c0d48108314db6f0e100bea2ce5a9a3a0e9a1f
Author: Peter D. Gray <peter@conalgo.com>
Date:   Fri Aug 2 14:51:33 2019 -0400

    deterministic-build/requirements-hw.txt: update to version 0.7.9 of ckcc-protocol for Coldcard

commit 5cd2c528698dfb4ad248844be3c741c25aa33e38
Merge: 5e2a36a3e 537b35586
Author: Peter D. Gray <peter@conalgo.com>
Date:   Fri Aug 2 14:41:59 2019 -0400

    Merge branch 'multisig' of github.com:Coldcard/electrum into multisig

commit 5e2a36a3ee28780a11f789f69896e6e795621bfc
Author: Peter D. Gray <peter@conalgo.com>
Date:   Fri Aug 2 14:41:49 2019 -0400

    Some fixes for p2wsh-p2sh and p2wsh cases

commit 537b35586e0b1e11622a8e7d718b6fd37d47f952
Merge: a9e3ca47e 2a80f6a3a
Author: nvk <rodolfo@rnvk.org>
Date:   Tue Jul 23 11:40:39 2019 -0400

    Merge branch 'master' into multisig

commit a9e3ca47e189bcf0556703a4f2ca0c084638eb73
Author: Peter D. Gray <peter@conalgo.com>
Date:   Mon Jun 24 13:36:41 2019 -0400

    Bugfix: not all keystores have labels

commit 57783ec158af5ca8d63d596638bc3b6ee63b053f
Author: Peter D. Gray <peter@conalgo.com>
Date:   Mon Jun 24 13:36:04 2019 -0400

    Add address format to export data, and bugfix: use xfp_for_keystore()

commit 6f1f7673eaa340d14497b11c2453f03a73b38850
Author: Peter D. Gray <peter@conalgo.com>
Date:   Fri Jun 21 09:06:49 2019 -0400

    Revert "bugfix: P2SH inputs can be signed with extra signatures, more than required"

    This reverts commit 75b6b663eca9e7b5edc9a463f7acd8f1c0f0a61a.

commit c322fb6dd2783e1103f5bf69ce60a365fbaf4bfe
Author: Peter D. Gray <peter@conalgo.com>
Date:   Thu Jun 20 12:57:19 2019 -0400

    Require latest CKCC protocol

commit 69a5b781ebc182851d2e25319b549ec58ea23eb1
Author: Peter D. Gray <peter@conalgo.com>
Date:   Thu Jun 20 12:40:27 2019 -0400

    gui/qt/main_window.py: add co-signer keystore label to wallet info display, and a hook for different buttons

commit 55d506d264dbb341602630c3429134e493995272
Author: Peter D. Gray <peter@conalgo.com>
Date:   Thu Jun 20 12:36:10 2019 -0400

    PSBT Combining/cleanup

commit 75b6b663eca9e7b5edc9a463f7acd8f1c0f0a61a
Author: Peter D. Gray <peter@conalgo.com>
Date:   Thu Jun 20 10:18:02 2019 -0400

    bugfix: P2SH inputs can be signed with extra signatures, more than required

commit 1bde362ddbbfd86520a7cb7bc51e0bcef06be078
Author: Peter D. Gray <peter@conalgo.com>
Date:   Wed Jun 19 09:47:26 2019 -0400

    Combines signed PSBT files

commit cc5c0532e52fbe282e862e20c250cc88ed435cad
Author: Peter D. Gray <peter@conalgo.com>
Date:   Fri Jun 14 13:04:32 2019 -0400

    Working towards multisig

commit cb20da5428ba97237006683133e10b0758999966
Author: Peter D. Gray <peter@conalgo.com>
Date:   Fri Jun 14 13:04:18 2019 -0400

    Refactor/import PSBT handling code into own files

commit 558ef82bb0a8c16fb4e8bd0a6a80190498f1ce57
Author: Peter D. Gray <peter@conalgo.com>
Date:   Tue May 28 13:26:10 2019 -0400

    plugins/hw_wallet/qt.py: show keystore label in tooltip

commit 269299df4a9eb5960b6c6ec0afcbf3ef69ad0be3
Author: Peter D. Gray <peter@conalgo.com>
Date:   Mon May 27 09:32:43 2019 -0400

    Swap endian of xpub fingprint values, so they are shown as BE32 in capitalized hex, rather than 0x%08x (LE32)
---
 contrib/requirements/requirements-hw.txt |   2 +-
 electrum/gui/qt/main_window.py           |  22 +-
 electrum/plugins/coldcard/basic_psbt.py  | 312 ++++++++++++++++++
 electrum/plugins/coldcard/build_psbt.py  | 391 +++++++++++++++++++++++
 electrum/plugins/coldcard/coldcard.py    | 361 ++++++++++-----------
 electrum/plugins/coldcard/qt.py          | 210 ++++++++++--
 electrum/plugins/hw_wallet/qt.py         |   2 +-
 7 files changed, 1068 insertions(+), 232 deletions(-)
 create mode 100644 electrum/plugins/coldcard/basic_psbt.py
 create mode 100644 electrum/plugins/coldcard/build_psbt.py

diff --git a/contrib/requirements/requirements-hw.txt b/contrib/requirements/requirements-hw.txt
index 7a6dad679..9f10a1f3a 100644
--- a/contrib/requirements/requirements-hw.txt
+++ b/contrib/requirements/requirements-hw.txt
@@ -2,5 +2,5 @@ trezor[hidapi]>=0.11.0
 safet[hidapi]>=0.1.0
 keepkey>=6.0.3
 btchip-python>=0.1.26
-ckcc-protocol>=0.7.2
+ckcc-protocol>=0.7.7
 hidapi
diff --git a/electrum/gui/qt/main_window.py b/electrum/gui/qt/main_window.py
index 7cbb98383..4cc9d097f 100644
--- a/electrum/gui/qt/main_window.py
+++ b/electrum/gui/qt/main_window.py
@@ -2390,29 +2390,39 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
             ks_type = str(keystore_types[0]) if keystore_types else _('No keystore')
             grid.addWidget(QLabel(ks_type), 4, 1)
         vbox.addLayout(grid)
+
         if self.wallet.is_deterministic():
             mpk_text = ShowQRTextEdit()
             mpk_text.setMaximumHeight(150)
             mpk_text.addCopyButton(self.app)
+
             def show_mpk(index):
                 mpk_text.setText(mpk_list[index])
                 mpk_text.repaint()  # macOS hack for #4777
+                
             # only show the combobox in case multiple accounts are available
             if len(mpk_list) > 1:
-                def label(key):
-                    if isinstance(self.wallet, Multisig_Wallet):
-                        return _("cosigner") + f' {key+1} ( keystore: {keystore_types[key]} )'
-                    return ''
-                labels = [label(i) for i in range(len(mpk_list))]
+                # only show the combobox if multiple master keys are defined
+                def label(idx, ks):
+                    if isinstance(self.wallet, Multisig_Wallet) and hasattr(ks, 'label'):
+                        return _("cosigner") + f' {idx+1}: {ks.get_type_text()} {ks.label}'
+                    else:
+                        return _("keystore") + f' {idx+1}'
+
+                labels = [label(idx, ks) for idx, ks in enumerate(self.wallet.get_keystores())]
+
                 on_click = lambda clayout: show_mpk(clayout.selected_index())
                 labels_clayout = ChoicesLayout(_("Master Public Keys"), labels, on_click)
                 vbox.addLayout(labels_clayout.layout())
             else:
                 vbox.addWidget(QLabel(_("Master Public Key")))
+
             show_mpk(0)
             vbox.addWidget(mpk_text)
+
         vbox.addStretch(1)
-        vbox.addLayout(Buttons(CloseButton(dialog)))
+        btns = run_hook('wallet_info_buttons', self, dialog) or Buttons(CloseButton(dialog))
+        vbox.addLayout(btns)
         dialog.setLayout(vbox)
         dialog.exec_()
 
diff --git a/electrum/plugins/coldcard/basic_psbt.py b/electrum/plugins/coldcard/basic_psbt.py
new file mode 100644
index 000000000..d220fad6b
--- /dev/null
+++ b/electrum/plugins/coldcard/basic_psbt.py
@@ -0,0 +1,312 @@
+#
+# basic_psbt.py - yet another PSBT parser/serializer but used only for test cases.
+#
+# - history: taken from coldcard-firmware/testing/psbt.py
+# - trying to minimize electrum code in here, and generally, dependancies.
+#
+import io, struct
+from base64 import b64decode
+from binascii import a2b_hex, b2a_hex
+from struct import pack, unpack
+
+from electrum.transaction import Transaction
+
+# BIP-174 (aka PSBT) defined values
+#
+PSBT_GLOBAL_UNSIGNED_TX 	= (0)
+PSBT_GLOBAL_XPUB         	= (1)
+
+PSBT_IN_NON_WITNESS_UTXO 	= (0)
+PSBT_IN_WITNESS_UTXO 	    = (1)
+PSBT_IN_PARTIAL_SIG 	    = (2)
+PSBT_IN_SIGHASH_TYPE 	    = (3)
+PSBT_IN_REDEEM_SCRIPT 	    = (4)
+PSBT_IN_WITNESS_SCRIPT 	    = (5)
+PSBT_IN_BIP32_DERIVATION 	= (6)
+PSBT_IN_FINAL_SCRIPTSIG 	= (7)
+PSBT_IN_FINAL_SCRIPTWITNESS = (8)
+
+PSBT_OUT_REDEEM_SCRIPT 	    = (0)
+PSBT_OUT_WITNESS_SCRIPT 	= (1)
+PSBT_OUT_BIP32_DERIVATION 	= (2)
+
+# Serialization/deserialization tools
+def ser_compact_size(l):
+    r = b""
+    if l < 253:
+        r = struct.pack("B", l)
+    elif l < 0x10000:
+        r = struct.pack("<BH", 253, l)
+    elif l < 0x100000000:
+        r = struct.pack("<BI", 254, l)
+    else:
+        r = struct.pack("<BQ", 255, l)
+    return r
+
+def deser_compact_size(f):
+    try:
+        nit = f.read(1)[0]
+    except IndexError:
+        return None     # end of file
+    
+    if nit == 253:
+        nit = struct.unpack("<H", f.read(2))[0]
+    elif nit == 254:
+        nit = struct.unpack("<I", f.read(4))[0]
+    elif nit == 255:
+        nit = struct.unpack("<Q", f.read(8))[0]
+    return nit
+
+def my_var_int(l):
+    # Bitcoin serialization of integers... directly into binary!
+    if l < 253:
+        return pack("B", l)
+    elif l < 0x10000:
+        return pack("<BH", 253, l)
+    elif l < 0x100000000:
+        return pack("<BI", 254, l)
+    else:
+        return pack("<BQ", 255, l)
+
+
+class PSBTSection:
+
+    def __init__(self, fd=None, idx=None):
+        self.defaults()
+        self.my_index = idx
+
+        if not fd: return
+
+        while 1:
+            ks = deser_compact_size(fd)
+            if ks is None: break
+            if ks == 0: break
+
+            key = fd.read(ks)
+            vs = deser_compact_size(fd)
+            val = fd.read(vs)
+
+            kt = key[0]
+            self.parse_kv(kt, key[1:], val)
+
+    def serialize(self, fd, my_idx):
+
+        def wr(ktype, val, key=b''):
+            fd.write(ser_compact_size(1 + len(key)))
+            fd.write(bytes([ktype]) + key)
+            fd.write(ser_compact_size(len(val)))
+            fd.write(val)
+
+        self.serialize_kvs(wr)
+
+        fd.write(b'\0')
+
+class BasicPSBTInput(PSBTSection):
+    def defaults(self):
+        self.utxo = None
+        self.witness_utxo = None
+        self.part_sigs = {}
+        self.sighash = None
+        self.bip32_paths = {}
+        self.redeem_script = None
+        self.witness_script = None
+        self.others = {}
+
+    def __eq__(a, b):
+        if a.sighash != b.sighash:
+            if a.sighash is not None and b.sighash is not None:
+                return False
+
+        rv =  a.utxo == b.utxo and \
+                a.witness_utxo == b.witness_utxo and \
+                a.redeem_script == b.redeem_script and \
+                a.witness_script == b.witness_script and \
+                a.my_index == b.my_index and \
+                a.bip32_paths == b.bip32_paths and \
+                sorted(a.part_sigs.keys()) == sorted(b.part_sigs.keys())
+
+        # NOTE: equality test on signatures requires parsing DER stupidness
+        #       and some maybe understanding of R/S values on curve that I don't have.
+
+        return rv
+
+    def parse_kv(self, kt, key, val):
+        if kt == PSBT_IN_NON_WITNESS_UTXO:
+            self.utxo = val
+            assert not key
+        elif kt == PSBT_IN_WITNESS_UTXO:
+            self.witness_utxo = val
+            assert not key
+        elif kt == PSBT_IN_PARTIAL_SIG:
+            self.part_sigs[key] = val
+        elif kt == PSBT_IN_SIGHASH_TYPE:
+            assert len(val) == 4
+            self.sighash = struct.unpack("<I", val)[0]
+            assert not key
+        elif kt == PSBT_IN_BIP32_DERIVATION:
+            self.bip32_paths[key] = val
+        elif kt == PSBT_IN_REDEEM_SCRIPT:
+            self.redeem_script = val
+            assert not key
+        elif kt == PSBT_IN_WITNESS_SCRIPT:
+            self.witness_script = val
+            assert not key
+        elif kt in ( PSBT_IN_REDEEM_SCRIPT,
+                     PSBT_IN_WITNESS_SCRIPT, 
+                     PSBT_IN_FINAL_SCRIPTSIG, 
+                     PSBT_IN_FINAL_SCRIPTWITNESS):
+            assert not key
+            self.others[kt] = val
+        else:
+            raise KeyError(kt)
+
+    def serialize_kvs(self, wr):
+        if self.utxo:
+            wr(PSBT_IN_NON_WITNESS_UTXO, self.utxo)
+        if self.witness_utxo:
+            wr(PSBT_IN_WITNESS_UTXO, self.witness_utxo)
+        if self.redeem_script:
+            wr(PSBT_IN_REDEEM_SCRIPT, self.redeem_script)
+        if self.witness_script:
+            wr(PSBT_IN_WITNESS_SCRIPT, self.witness_script)
+        for pk, val in sorted(self.part_sigs.items()):
+            wr(PSBT_IN_PARTIAL_SIG, val, pk)
+        if self.sighash is not None:
+            wr(PSBT_IN_SIGHASH_TYPE, struct.pack('<I', self.sighash))
+        for k in self.bip32_paths:
+            wr(PSBT_IN_BIP32_DERIVATION, self.bip32_paths[k], k)
+        for k in self.others:
+            wr(k, self.others[k])
+
+class BasicPSBTOutput(PSBTSection):
+    def defaults(self):
+        self.redeem_script = None
+        self.witness_script = None
+        self.bip32_paths = {}
+
+    def __eq__(a, b):
+        return  a.redeem_script == b.redeem_script and \
+                a.witness_script == b.witness_script and \
+                a.my_index == b.my_index and \
+                a.bip32_paths == b.bip32_paths
+
+    def parse_kv(self, kt, key, val):
+        if kt == PSBT_OUT_REDEEM_SCRIPT:
+            self.redeem_script = val
+            assert not key
+        elif kt == PSBT_OUT_WITNESS_SCRIPT:
+            self.witness_script = val
+            assert not key
+        elif kt == PSBT_OUT_BIP32_DERIVATION:
+            self.bip32_paths[key] = val
+        else:
+            raise ValueError(kt)
+
+    def serialize_kvs(self, wr):
+        if self.redeem_script:
+            wr(PSBT_OUT_REDEEM_SCRIPT, self.redeem_script)
+        if self.witness_script:
+            wr(PSBT_OUT_WITNESS_SCRIPT, self.witness_script)
+        for k in self.bip32_paths:
+            wr(PSBT_OUT_BIP32_DERIVATION, self.bip32_paths[k], k)
+
+
+class BasicPSBT:
+    "Just? parse and store"
+
+    def __init__(self):
+
+        self.txn = None
+        self.filename = None
+        self.parsed_txn = None
+        self.xpubs = []
+
+        self.inputs = []
+        self.outputs = []
+
+    def __eq__(a, b):
+        return a.txn == b.txn and \
+            len(a.inputs) == len(b.inputs) and \
+            len(a.outputs) == len(b.outputs) and \
+            all(a.inputs[i] == b.inputs[i] for i in range(len(a.inputs))) and \
+            all(a.outputs[i] == b.outputs[i] for i in range(len(a.outputs))) and \
+            sorted(a.xpubs) == sorted(b.xpubs)
+
+    def parse(self, raw, filename=None):
+        # auto-detect and decode Base64 and Hex.
+        if raw[0:10].lower() == b'70736274ff':
+            raw = a2b_hex(raw.strip())
+        if raw[0:6] == b'cHNidP':
+            raw = b64decode(raw)
+        assert raw[0:5] == b'psbt\xff', "bad magic"
+
+        self.filename = filename
+
+        with io.BytesIO(raw[5:]) as fd:
+            
+            # globals
+            while 1:
+                ks = deser_compact_size(fd)
+                if ks is None: break
+
+                if ks == 0: break
+
+                key = fd.read(ks)
+                vs = deser_compact_size(fd)
+                val = fd.read(vs)
+
+                kt = key[0]
+                if kt == PSBT_GLOBAL_UNSIGNED_TX:
+                    self.txn = val
+
+                    self.parsed_txn = Transaction(val.hex())
+                    num_ins = len(self.parsed_txn.inputs())
+                    num_outs = len(self.parsed_txn.outputs())
+
+                elif kt == PSBT_GLOBAL_XPUB:
+                    # key=(xpub) => val=(path)
+                    self.xpubs.append( (key, val) )
+                else:
+                    raise ValueError('unknown global key type: 0x%02x' % kt)
+
+            assert self.txn, 'missing reqd section'
+
+            self.inputs = [BasicPSBTInput(fd, idx) for idx in range(num_ins)]
+            self.outputs = [BasicPSBTOutput(fd, idx) for idx in range(num_outs)]
+
+            sep = fd.read(1)
+            assert sep == b''
+
+        return self
+
+    def serialize(self, fd):
+
+        def wr(ktype, val, key=b''):
+            fd.write(ser_compact_size(1 + len(key)))
+            fd.write(bytes([ktype]) + key)
+            fd.write(ser_compact_size(len(val)))
+            fd.write(val)
+
+        fd.write(b'psbt\xff')
+
+        wr(PSBT_GLOBAL_UNSIGNED_TX, self.txn)
+
+        for k,v in self.xpubs:
+            wr(PSBT_GLOBAL_XPUB, v, key=k)
+
+        # sep
+        fd.write(b'\0')
+
+        for idx, inp in enumerate(self.inputs):
+            inp.serialize(fd, idx)
+
+        for idx, outp in enumerate(self.outputs):
+            outp.serialize(fd, idx)
+
+    def as_bytes(self):
+        with io.BytesIO() as fd:
+            self.serialize(fd)
+            return fd.getvalue()
+
+# EOF
+
diff --git a/electrum/plugins/coldcard/build_psbt.py b/electrum/plugins/coldcard/build_psbt.py
new file mode 100644
index 000000000..31b98b583
--- /dev/null
+++ b/electrum/plugins/coldcard/build_psbt.py
@@ -0,0 +1,391 @@
+#
+# build_psbt.py - create a PSBT from (unsigned) transaction and keystore data.
+#
+import io, struct
+from base64 import b64decode
+from binascii import a2b_hex, b2a_hex
+from struct import pack, unpack
+
+from electrum.transaction import (Transaction, multisig_script, parse_redeemScript_multisig,
+                                    NotRecognizedRedeemScript)
+
+from electrum.logging import get_logger
+from electrum.wallet import Standard_Wallet, Multisig_Wallet, Wallet
+from electrum.keystore import xpubkey_to_pubkey, Xpub
+from electrum.util import bfh, bh2u
+from electrum.crypto import hash_160
+from electrum.bitcoin import DecodeBase58Check
+
+from .basic_psbt import (
+        PSBT_GLOBAL_UNSIGNED_TX, PSBT_GLOBAL_XPUB, PSBT_IN_NON_WITNESS_UTXO, PSBT_IN_WITNESS_UTXO,
+        PSBT_IN_SIGHASH_TYPE, PSBT_IN_REDEEM_SCRIPT, PSBT_IN_WITNESS_SCRIPT, PSBT_IN_PARTIAL_SIG,
+        PSBT_IN_BIP32_DERIVATION, PSBT_OUT_BIP32_DERIVATION, PSBT_OUT_REDEEM_SCRIPT)
+from .basic_psbt import BasicPSBT
+
+from electrum.logging import get_logger
+from electrum.wallet import Standard_Wallet, Multisig_Wallet, Wallet
+from electrum.util import bfh, bh2u
+from electrum.crypto import hash_160
+from electrum.bitcoin import DecodeBase58Check
+
+
+_logger = get_logger(__name__)
+
+def xfp2str(xfp):
+    # Standardized way to show an xpub's fingerprint... it's a 4-byte string
+    # and not really an integer. Used to show as '0x%08x' but that's wrong endian.
+    return b2a_hex(pack('<I', xfp)).decode('ascii').upper()
+
+def xfp_from_xpub(xpub):
+    # sometime we need to BIP32 fingerprint value: 4 bytes of ripemd(sha256(pubkey))
+    kk = bfh(Xpub.get_pubkey_from_xpub(xpub, []))
+    assert len(kk) == 33
+    xfp, = unpack('<I', hash_160(kk)[0:4])
+    return xfp
+
+def packed_xfp_path(xfp, text_path, int_path=[]):
+    # Convert text subkey derivation path into binary format needed for PSBT
+    # - binary LE32 values, first one is the fingerprint
+    rv = pack('<I', xfp)
+
+    for x in text_path.split('/'):
+        if x == 'm': continue
+        if x.endswith("'"):
+            x = int(x[:-1]) | 0x80000000
+        else:
+            x = int(x)
+        rv += pack('<I', x)
+
+    for x in int_path:
+        rv += pack('<I', x)
+
+    return rv
+
+def unpacked_xfp_path(xfp, text_path):
+    # Convert text subkey derivation path into format needed for PSBT
+    # - binary LE32 values, first one is the fingerprint
+    # - but as ints, not bytes yet
+    rv = [xfp]
+    for x in text_path.split('/'):
+        if x == 'm': continue
+        if x.endswith("'"):
+            x = int(x[:-1]) | 0x80000000
+        else:
+            x = int(x)
+        rv.append(x)
+    return rv
+
+def xfp_for_keystore(ks):
+    # Need the fingerprint of the MASTER key for a keystore we're playing with.
+    xfp = getattr(ks, 'ckcc_xfp', None)
+
+    if xfp is None:
+        xfp = xfp_from_xpub(ks.get_master_public_key())
+        setattr(ks, 'ckcc_xfp', xfp)
+
+    return xfp
+
+
+# Serialization/deserialization tools
+def ser_compact_size(l):
+    r = b""
+    if l < 253:
+        r = struct.pack("B", l)
+    elif l < 0x10000:
+        r = struct.pack("<BH", 253, l)
+    elif l < 0x100000000:
+        r = struct.pack("<BI", 254, l)
+    else:
+        r = struct.pack("<BQ", 255, l)
+    return r
+
+def deser_compact_size(f):
+    try:
+        nit = f.read(1)[0]
+    except IndexError:
+        return None     # end of file
+    
+    if nit == 253:
+        nit = struct.unpack("<H", f.read(2))[0]
+    elif nit == 254:
+        nit = struct.unpack("<I", f.read(4))[0]
+    elif nit == 255:
+        nit = struct.unpack("<Q", f.read(8))[0]
+    return nit
+
+def my_var_int(l):
+    # Bitcoin serialization of integers... directly into binary!
+    if l < 253:
+        return pack("B", l)
+    elif l < 0x10000:
+        return pack("<BH", 253, l)
+    elif l < 0x100000000:
+        return pack("<BI", 254, l)
+    else:
+        return pack("<BQ", 255, l)
+
+def build_psbt(tx: Transaction, wallet: Wallet):
+    # Render a PSBT file, for possible upload to Coldcard.
+    # 
+    # TODO this should be part of Wallet object, or maybe Transaction?
+
+    if getattr(tx, 'raw_psbt', False):
+        _logger.info('PSBT cache hit')
+        return tx.raw_psbt
+
+    inputs = tx.inputs()
+    if 'prev_tx' not in inputs[0]:
+        # fetch info about inputs, if needed?
+        # - needed during export PSBT flow, not normal online signing
+        wallet.add_hw_info(tx)
+
+    # wallet.add_hw_info installs this attr
+    assert tx.output_info is not None, 'need data about outputs'
+
+    # Build a map of all pubkeys needed as derivation from master XFP, in PSBT binary format
+    # 1) binary version of the common subpath for all keys
+    #       m/ => fingerprint LE32
+    #       a/b/c => ints
+    #
+    # 2) all used keys in transaction:
+    #    - for all inputs and outputs (when its change back)
+    #    - for all keystores, if multisig
+    #
+    subkeys = {}
+    for ks in wallet.get_keystores():
+
+        # XFP + fixed prefix for this keystore
+        ks_prefix = packed_xfp_path(xfp_for_keystore(ks), ks.get_derivation()[2:])
+
+        # all pubkeys needed for input signing
+        for xpubkey, derivation in ks.get_tx_derivations(tx).items():
+            pubkey = xpubkey_to_pubkey(xpubkey)
+
+            # assuming depth two, non-harded: change + index
+            aa, bb = derivation
+            assert 0 <= aa < 0x80000000 and 0 <= bb < 0x80000000
+
+            subkeys[bfh(pubkey)] = ks_prefix + pack('<II', aa, bb)
+
+        # all keys related to change outputs
+        for o in tx.outputs():
+            if o.address in tx.output_info:
+                # this address "is_mine" but might not be change (if I send funds to myself)
+                chg_path = tx.output_info.get(o.address).address_index
+
+                if chg_path[0] != 1 or len(chg_path) != 2:
+                    # not change.
+                    continue
+
+                pubkey = ks.derive_pubkey(True, chg_path[1])
+                subkeys[bfh(pubkey)] = ks_prefix + pack('<II', *chg_path)
+        
+    for txin in inputs:
+        assert txin['type'] != 'coinbase', _("Coinbase not supported")
+
+        if txin['type'] in ['p2sh', 'p2wsh-p2sh', 'p2wsh']:
+            assert type(wallet) is Multisig_Wallet
+
+    # Construct PSBT from start to finish.
+    out_fd = io.BytesIO()
+    out_fd.write(b'psbt\xff')
+
+    def write_kv(ktype, val, key=b''):
+        # serialize helper: write w/ size and key byte
+        out_fd.write(my_var_int(1 + len(key)))
+        out_fd.write(bytes([ktype]) + key)
+
+        if isinstance(val, str):
+            val = bfh(val)
+
+        out_fd.write(my_var_int(len(val)))
+        out_fd.write(val)
+
+
+    # global section: just the unsigned txn
+    class CustomTXSerialization(Transaction):
+        @classmethod
+        def input_script(cls, txin, estimate_size=False):
+            return ''
+
+    unsigned = bfh(CustomTXSerialization(tx.serialize()).serialize_to_network(witness=False))
+    write_kv(PSBT_GLOBAL_UNSIGNED_TX, unsigned)
+
+    if type(wallet) is Multisig_Wallet:
+
+        # always put the xpubs into the PSBT, useful at least for checking
+        for xp, ks in zip(wallet.get_master_public_keys(), wallet.get_keystores()):
+            xfp = xfp_for_keystore(ks)
+
+            dd = getattr(ks, 'derivation', 'm')
+
+            write_kv(PSBT_GLOBAL_XPUB, packed_xfp_path(xfp, dd), DecodeBase58Check(xp))
+
+    # end globals section
+    out_fd.write(b'\x00')
+
+    # inputs section
+    for txin in inputs:
+        if Transaction.is_segwit_input(txin):
+            utxo = txin['prev_tx'].outputs()[txin['prevout_n']]
+            spendable = txin['prev_tx'].serialize_output(utxo)
+            write_kv(PSBT_IN_WITNESS_UTXO, spendable)
+        else:
+            write_kv(PSBT_IN_NON_WITNESS_UTXO, str(txin['prev_tx']))
+
+        pubkeys, x_pubkeys = tx.get_sorted_pubkeys(txin)
+
+        pubkeys = [bfh(k) for k in pubkeys]
+
+        if type(wallet) is Multisig_Wallet:
+            # always need a redeem script for multisig
+            scr = Transaction.get_preimage_script(txin)
+
+            if 'p2wsh' in txin['type']:
+                # needed for both p2wsh-p2sh and p2wsh
+                write_kv(PSBT_IN_WITNESS_SCRIPT, bfh(scr))
+            else:
+                write_kv(PSBT_IN_REDEEM_SCRIPT, bfh(scr))
+
+        sigs = txin.get('signatures')
+
+        for pk_pos, (pubkey, x_pubkey) in enumerate(zip(pubkeys, x_pubkeys)):
+            if pubkey in subkeys:
+                # faster? case ... calculated above
+                write_kv(PSBT_IN_BIP32_DERIVATION, subkeys[pubkey], pubkey)
+            else:
+                # when an input is partly signed, tx.get_tx_derivations()
+                # doesn't include that keystore's value and yet we need it
+                # because we need to show a correct keypath... 
+                assert x_pubkey[0:2] == 'ff', x_pubkey
+
+                for ks in wallet.get_keystores():
+                    d = ks.get_pubkey_derivation(x_pubkey)
+                    if d is not None:
+                        ks_path = packed_xfp_path(xfp_for_keystore(ks), ks.get_derivation()[2:], d)
+                        write_kv(PSBT_IN_BIP32_DERIVATION, ks_path, pubkey)
+                        break
+                else:
+                    raise AssertionError("no keystore for: %s" % x_pubkey)
+
+            if txin['type'] == 'p2wpkh-p2sh':
+                assert len(pubkeys) == 1, 'can be only one redeem script per input'
+                pa = hash_160(k)
+                assert len(pa) == 20
+                write_kv(PSBT_IN_REDEEM_SCRIPT, b'\x00\x14'+pa)
+
+            # optional? insert (partial) signatures that we already have
+            if sigs and sigs[pk_pos]:
+                write_kv(PSBT_IN_PARTIAL_SIG, bfh(sigs[pk_pos]), pubkey)
+
+        out_fd.write(b'\x00')
+
+    # outputs section
+    for o in tx.outputs():
+        # can be empty, but must be present, and helpful to show change inputs
+        # wallet.add_hw_info() adds some data about change outputs into tx.output_info
+        if o.address in tx.output_info:
+            # this address "is_mine" but might not be change (if I send funds to myself)
+            output_info = tx.output_info.get(o.address)
+            chg_path, master_xpubs = output_info.address_index, output_info.sorted_xpubs
+
+            if chg_path[0] == 1 and len(chg_path) == 2:
+                # it is a change output (based on our standard derivation path)
+                pubkeys = [bfh(i) for i in wallet.get_public_keys(o.address)]
+
+                # always need a redeem script for multisig
+                if type(wallet) is Multisig_Wallet:
+                    scr = multisig_script([bh2u(i) for i in sorted(pubkeys)], wallet.m)
+                    write_kv(PSBT_OUT_REDEEM_SCRIPT, bfh(scr))
+
+                # document change output's bip32 derivation(s)
+                for pubkey in pubkeys:
+                    sk = subkeys[pubkey]
+                    write_kv(PSBT_OUT_BIP32_DERIVATION, sk, pubkey)
+
+                    if output_info.script_type == 'p2wpkh-p2sh':
+                        assert len(pa) == 20
+                        assert len(pubkeys) == 1
+                        pa = hash_160(pubkey)
+                        write_kv(PSBT_OUT_REDEEM_SCRIPT, b'\x00\x14' + pa)
+
+        out_fd.write(b'\x00')
+
+    # capture for later use
+    tx.raw_psbt = out_fd.getvalue()
+
+    return tx.raw_psbt
+
+
+def recover_tx_from_psbt(first: BasicPSBT, wallet: Wallet) -> Transaction:
+    # Take a PSBT object and re-construct the Electrum transaction object.
+    # - does not include signatures, see merge_sigs_from_psbt
+    # - any PSBT in the group could be used for this purpose; all must share tx details
+    
+    tx = Transaction(first.txn.hex())
+    tx.deserialize(force_full_parse=True)
+
+    # .. add back some data that's been preserved in the PSBT, but isn't part of
+    # of the unsigned bitcoin txn
+    tx.is_partial_originally = True
+
+    for idx, inp in enumerate(tx.inputs()):
+        scr = first.inputs[idx].redeem_script or first.inputs[idx].witness_script
+
+        # XXX should use transaction.py parse_scriptSig() here!
+        if scr:
+            try:
+                M, N, __, pubkeys, __ = parse_redeemScript_multisig(scr)
+            except NotRecognizedRedeemScript:
+                # limitation: we can only handle M-of-N multisig here
+                raise ValueError("Cannot handle non M-of-N multisig input")
+
+            inp['pubkeys'] = pubkeys
+            inp['x_pubkeys'] = pubkeys
+            inp['num_sig'] = M
+            inp['type'] = 'p2wsh' if first.inputs[idx].witness_script else 'p2sh'
+
+            # bugfix: transaction.py:parse_input() puts empty dict here, but need a list
+            inp['signatures'] = [None] * N
+
+        if 'prev_tx' not in inp:
+            # fetch info about inputs' previous txn
+            wallet.add_hw_info(tx)
+
+        if 'value' not in inp:
+            # we'll need to know the value of the outpts used as part
+            # of the witness data, much later...
+            inp['value'] = inp['prev_tx'].outputs()[inp['prevout_n']].value
+
+    return tx
+
+def merge_sigs_from_psbt(tx: Transaction, psbt: BasicPSBT):
+    # Take new signatures from PSBT, and merge into in-memory transaction object.
+    # - "we trust everyone here" ... no validation/checks
+
+    count = 0
+    for inp_idx, inp in enumerate(psbt.inputs):
+        if not inp.part_sigs:
+            continue
+
+        scr = inp.redeem_script or inp.witness_script
+
+        # need to map from pubkey to signing position in redeem script
+        M, N, _, pubkeys, _ = parse_redeemScript_multisig(scr)
+        #assert (M, N) == (wallet.m, wallet.n)
+
+        for sig_pk in inp.part_sigs:
+            pk_pos = pubkeys.index(sig_pk.hex())
+            tx.add_signature_to_txin(inp_idx, pk_pos, inp.part_sigs[sig_pk].hex())
+            count += 1
+
+        #print("#%d: sigs = %r" % (inp_idx, tx.inputs()[inp_idx]['signatures']))
+    
+    # reset serialization of TX
+    tx.raw = tx.serialize()
+    tx.raw_psbt = None
+
+    return count
+
+# EOF
+
diff --git a/electrum/plugins/coldcard/coldcard.py b/electrum/plugins/coldcard/coldcard.py
index b14c6a1ec..4b37660ad 100644
--- a/electrum/plugins/coldcard/coldcard.py
+++ b/electrum/plugins/coldcard/coldcard.py
@@ -8,18 +8,22 @@ import traceback
 
 from electrum.bip32 import BIP32Node, InvalidMasterKeyVersionBytes
 from electrum.i18n import _
-from electrum.plugin import Device
-from electrum.keystore import Hardware_KeyStore, xpubkey_to_pubkey, Xpub
-from electrum.transaction import Transaction
-from electrum.wallet import Standard_Wallet
+from electrum.plugin import Device, hook
+from electrum.keystore import Hardware_KeyStore
+from electrum.transaction import Transaction, multisig_script
+from electrum.wallet import Standard_Wallet, Multisig_Wallet, Wallet
 from electrum.crypto import hash_160
 from electrum.util import bfh, bh2u, versiontuple, UserFacingException
 from electrum.base_wizard import ScriptTypeNotSupported
 from electrum.logging import get_logger
+from electrum.bitcoin import DecodeBase58Check
 
 from ..hw_wallet import HW_PluginBase
-from ..hw_wallet.plugin import LibraryFoundButUnusable
+from ..hw_wallet.plugin import LibraryFoundButUnusable, only_hook_if_libraries_available
 
+from .basic_psbt import BasicPSBT
+from .build_psbt import (build_psbt, xfp2str, unpacked_xfp_path,
+                            merge_sigs_from_psbt, xfp_for_keystore)
 
 _logger = get_logger(__name__)
 
@@ -30,10 +34,10 @@ try:
     from ckcc.protocol import CCProtoError, CCUserRefused, CCBusyError
     from ckcc.constants import (MAX_MSG_LEN, MAX_BLK_LEN, MSG_SIGNING_MAX_LENGTH, MAX_TXN_LEN,
         AF_CLASSIC, AF_P2SH, AF_P2WPKH, AF_P2WSH, AF_P2WPKH_P2SH, AF_P2WSH_P2SH)
-    from ckcc.constants import (
-        PSBT_GLOBAL_UNSIGNED_TX, PSBT_IN_NON_WITNESS_UTXO, PSBT_IN_WITNESS_UTXO,
-        PSBT_IN_SIGHASH_TYPE, PSBT_IN_REDEEM_SCRIPT, PSBT_IN_WITNESS_SCRIPT,
-        PSBT_IN_BIP32_DERIVATION, PSBT_OUT_BIP32_DERIVATION, PSBT_OUT_REDEEM_SCRIPT)
+    #from ckcc.constants import (
+        #PSBT_GLOBAL_UNSIGNED_TX, PSBT_GLOBAL_XPUB, PSBT_IN_NON_WITNESS_UTXO, PSBT_IN_WITNESS_UTXO,
+        #PSBT_IN_SIGHASH_TYPE, PSBT_IN_REDEEM_SCRIPT, PSBT_IN_WITNESS_SCRIPT,
+        #PSBT_IN_BIP32_DERIVATION, PSBT_OUT_BIP32_DERIVATION, PSBT_OUT_REDEEM_SCRIPT)
 
     from ckcc.client import ColdcardDevice, COINKITE_VID, CKCC_PID, CKCC_SIMULATOR_PATH
 
@@ -60,26 +64,6 @@ except ImportError:
 
 CKCC_SIMULATED_PID = CKCC_PID ^ 0x55aa
 
-def my_var_int(l):
-    # Bitcoin serialization of integers... directly into binary!
-    if l < 253:
-        return pack("B", l)
-    elif l < 0x10000:
-        return pack("<BH", 253, l)
-    elif l < 0x100000000:
-        return pack("<BI", 254, l)
-    else:
-        return pack("<BQ", 255, l)
-
-def xfp_from_xpub(xpub):
-    # sometime we need to BIP32 fingerprint value: 4 bytes of ripemd(sha256(pubkey))
-    # UNTESTED
-    kk = bfh(Xpub.get_pubkey_from_xpub(xpub, []))
-    assert len(kk) == 33
-    xfp, = unpack('<I', hash_160(kk)[0:4])
-    return xfp
-
-
 class CKCCClient:
     # Challenge: I haven't found anywhere that defines a base class for this 'client',
     # nor an API (interface) to be met. Winging it. Gets called from lib/plugins.py mostly?
@@ -105,24 +89,27 @@ class CKCCClient:
         # should expect. It's also kinda slow.
 
     def __repr__(self):
-        return '<CKCCClient: xfp=%08x label=%r>' % (self.dev.master_fingerprint,
+        return '<CKCCClient: xfp=%s label=%r>' % (xfp2str(self.dev.master_fingerprint),
                                                         self.label())
 
-    def verify_connection(self, expected_xfp, expected_xpub):
+    def verify_connection(self, expected_xfp, expected_xpub=None):
         ex = (expected_xfp, expected_xpub)
 
         if self._expected_device == ex:
             # all is as expected
             return
 
+        if expected_xpub is None:
+            expected_xpub = self.dev.master_xpub
+
         if ( (self._expected_device is not None) 
                 or (self.dev.master_fingerprint != expected_xfp)
                 or (self.dev.master_xpub != expected_xpub)):
             # probably indicating programing error, not hacking
             _logger.info(f"xpubs. reported by device: {self.dev.master_xpub}. "
                          f"stored in file: {expected_xpub}")
-            raise RuntimeError("Expecting 0x%08x but that's not what's connected?!" %
-                               expected_xfp)
+            raise RuntimeError("Expecting %s but that's not what's connected?!" %
+                               xfp2str(expected_xfp))
 
         # check signature over session key
         # - mitm might have lied about xfp and xpub up to here
@@ -132,10 +119,13 @@ class CKCCClient:
 
         self._expected_device = ex
 
+        if not getattr(self, 'ckcc_xpub', None):
+            self.ckcc_xpub = expected_xpub
+
         _logger.info("Successfully verified against MiTM")
 
     def is_pairable(self):
-        # can't do anything w/ devices that aren't setup (but not normally reachable)
+        # can't do anything w/ devices that aren't setup (this code not normally reachable)
         return bool(self.dev.master_xpub)
 
     def timeout(self, cutoff):
@@ -155,12 +145,12 @@ class CKCCClient:
         # not be encrypted, so better for privacy if based on xpub/fingerprint rather than
         # USB serial number.
         if self.dev.is_simulator:
-            lab = 'Coldcard Simulator 0x%08x' % self.dev.master_fingerprint
+            lab = 'Coldcard Simulator ' + xfp2str(self.dev.master_fingerprint)
         elif not self.dev.master_fingerprint:
             # failback; not expected
             lab = 'Coldcard #' + self.dev.serial
         else:
-            lab = 'Coldcard 0x%08x' % self.dev.master_fingerprint
+            lab = 'Coldcard ' + xfp2str(self.dev.master_fingerprint)
 
         # Hack zone: during initial setup I need the xfp and master xpub but 
         # very few objects are passed between the various steps of base_wizard.
@@ -210,9 +200,13 @@ class CKCCClient:
             raise RuntimeError("Communication trouble with Coldcard")
 
     def show_address(self, path, addr_fmt):
-        # prompt user w/ addres, also returns it immediately.
+        # prompt user w/ address, also returns it immediately.
         return self.dev.send_recv(CCProtocolPacker.show_address(path, addr_fmt), timeout=None)
 
+    def show_p2sh_address(self, *args, **kws):
+        # prompt user w/ p2sh address, also returns it immediately.
+        return self.dev.send_recv(CCProtocolPacker.show_p2sh_address(*args, **kws), timeout=None)
+
     def get_version(self):
         # gives list of strings
         return self.dev.send_recv(CCProtocolPacker.version(), timeout=1000).split('\n')
@@ -262,22 +256,27 @@ class Coldcard_KeyStore(Hardware_KeyStore):
         self.force_watching_only = False
         self.ux_busy = False
 
+        # for multisig I need to know what wallet this keystore is part of
+        # this is captured by hooling  make_unsigned_transaction
+        self.my_wallet = None
+
         # Seems like only the derivation path and resulting **derived** xpub is stored in
         # the wallet file... however, we need to know at least the fingerprint of the master
         # xpub to verify against MiTM, and also so we can put the right value into the subkey paths
         # of PSBT files that might be generated offline. 
         # - save the fingerprint of the master xpub, as "xfp"
-        # - it's a LE32 int, but hex more natural way to see it
+        # - it's a LE32 int, but hex BE32 is more natural way to view it
         # - device reports these value during encryption setup process
+        # - full xpub value now optional
         lab = d['label']
         if hasattr(lab, 'xfp'):
             # initial setup
             self.ckcc_xfp = lab.xfp
-            self.ckcc_xpub = lab.xpub
+            self.ckcc_xpub = getattr(lab, 'xpub', None)
         else:
             # wallet load: fatal if missing, we need them!
             self.ckcc_xfp = d['ckcc_xfp']
-            self.ckcc_xpub = d['ckcc_xpub']
+            self.ckcc_xpub = d.get('ckcc_xpub', None)
 
     def dump(self):
         # our additions to the stored data about keystore -- only during creation?
@@ -294,6 +293,7 @@ class Coldcard_KeyStore(Hardware_KeyStore):
     def get_client(self):
         # called when user tries to do something like view address, sign somthing.
         # - not called during probing/setup
+        # - will fail if indicated device can't produce the xpub (at derivation) expected
         rv = self.plugin.get_client(self)
         if rv:
             rv.verify_connection(self.ckcc_xfp, self.ckcc_xpub)
@@ -377,162 +377,35 @@ class Coldcard_KeyStore(Hardware_KeyStore):
         # give empty bytes for error cases; it seems to clear the old signature box
         return b''
 
-    def build_psbt(self, tx: Transaction, wallet=None, xfp=None):
-        # Render a PSBT file, for upload to Coldcard.
-        # 
-        if xfp is None:
-            # need fingerprint of MASTER xpub, not the derived key
-            xfp = self.ckcc_xfp
-
-        inputs = tx.inputs()
-
-        if 'prev_tx' not in inputs[0]:
-            # fetch info about inputs, if needed?
-            # - needed during export PSBT flow, not normal online signing
-            assert wallet, 'need wallet reference'
-            wallet.add_hw_info(tx)
-
-        # wallet.add_hw_info installs this attr
-        assert tx.output_info is not None, 'need data about outputs'
-
-        # Build map of pubkey needed as derivation from master, in PSBT binary format
-        # 1) binary version of the common subpath for all keys
-        #       m/ => fingerprint LE32
-        #       a/b/c => ints
-        base_path = pack('<I', xfp)
-        for x in self.get_derivation()[2:].split('/'):
-            if x.endswith("'"):
-                x = int(x[:-1]) | 0x80000000
-            else:
-                x = int(x)
-            base_path += pack('<I', x)
-
-        # 2) all used keys in transaction
-        subkeys = {}
-        derivations = self.get_tx_derivations(tx)
-        for xpubkey in derivations:
-            pubkey = xpubkey_to_pubkey(xpubkey)
-
-            # assuming depth two, non-harded: change + index
-            aa, bb = derivations[xpubkey]
-            assert 0 <= aa < 0x80000000
-            assert 0 <= bb < 0x80000000
-
-            subkeys[bfh(pubkey)] = base_path + pack('<II', aa, bb)
-            
-        for txin in inputs:
-            if txin['type'] == 'coinbase':
-                self.give_error("Coinbase not supported")
-
-            if txin['type'] in ['p2sh', 'p2wsh-p2sh', 'p2wsh']:
-                self.give_error('No support yet for inputs of type: ' + txin['type'])
-
-        # Construct PSBT from start to finish.
-        out_fd = io.BytesIO()
-        out_fd.write(b'psbt\xff')
-
-        def write_kv(ktype, val, key=b''):
-            # serialize helper: write w/ size and key byte
-            out_fd.write(my_var_int(1 + len(key)))
-            out_fd.write(bytes([ktype]) + key)
-
-            if isinstance(val, str):
-                val = bfh(val)
-
-            out_fd.write(my_var_int(len(val)))
-            out_fd.write(val)
-
-
-        # global section: just the unsigned txn
-        class CustomTXSerialization(Transaction):
-            @classmethod
-            def input_script(cls, txin, estimate_size=False):
-                return ''
-
-        unsigned = bfh(CustomTXSerialization(tx.serialize()).serialize_to_network(witness=False))
-        write_kv(PSBT_GLOBAL_UNSIGNED_TX, unsigned)
-
-        # end globals section
-        out_fd.write(b'\x00')
-
-        # inputs section
-        for txin in inputs:
-            if Transaction.is_segwit_input(txin):
-                utxo = txin['prev_tx'].outputs()[txin['prevout_n']]
-                spendable = txin['prev_tx'].serialize_output(utxo)
-                write_kv(PSBT_IN_WITNESS_UTXO, spendable)
-            else:
-                write_kv(PSBT_IN_NON_WITNESS_UTXO, str(txin['prev_tx']))
-
-            pubkeys, x_pubkeys = tx.get_sorted_pubkeys(txin)
-
-            pubkeys = [bfh(k) for k in pubkeys]
-
-            for k in pubkeys:
-                write_kv(PSBT_IN_BIP32_DERIVATION, subkeys[k], k)
-
-                if txin['type'] == 'p2wpkh-p2sh':
-                    assert len(pubkeys) == 1, 'can be only one redeem script per input'
-                    pa = hash_160(k)
-                    assert len(pa) == 20
-                    write_kv(PSBT_IN_REDEEM_SCRIPT, b'\x00\x14'+pa)
-
-            out_fd.write(b'\x00')
-
-        # outputs section
-        for o in tx.outputs():
-            # can be empty, but must be present, and helpful to show change inputs
-            # wallet.add_hw_info() adds some data about change outputs into tx.output_info
-            if o.address in tx.output_info:
-                # this address "is_mine" but might not be change (I like to sent to myself)
-                output_info = tx.output_info.get(o.address)
-                index, xpubs = output_info.address_index, output_info.sorted_xpubs
-
-                if index[0] == 1 and len(index) == 2:
-                    # it is a change output (based on our standard derivation path)
-                    assert len(xpubs) == 1      # not expecting multisig
-                    xpubkey = xpubs[0]
-
-                    # document its bip32 derivation in output section
-                    aa, bb = index
-                    assert 0 <= aa < 0x80000000
-                    assert 0 <= bb < 0x80000000
-
-                    deriv = base_path + pack('<II', aa, bb)
-                    pubkey = bfh(self.get_pubkey_from_xpub(xpubkey, index))
-
-                    write_kv(PSBT_OUT_BIP32_DERIVATION, deriv, pubkey)
-
-                    if output_info.script_type == 'p2wpkh-p2sh':
-                        pa = hash_160(pubkey)
-                        assert len(pa) == 20
-                        write_kv(PSBT_OUT_REDEEM_SCRIPT, b'\x00\x14' + pa)
-
-            out_fd.write(b'\x00')
-
-        return out_fd.getvalue()
-
-
     @wrap_busy
-    def sign_transaction(self, tx, password):
+    def sign_transaction(self, tx: Transaction, password):
         # Build a PSBT in memory, upload it for signing.
         # - we can also work offline (without paired device present)
         if tx.is_complete():
             return
 
+        assert self.my_wallet, "Not clear which wallet associated with this Coldcard"
+
         client = self.get_client()
 
+        if 0:
+            from pprint import pprint
+            for n,i in enumerate(tx.inputs()):
+                print('[%d]: ' % n, end='')
+                pprint(i)
+
         assert client.dev.master_fingerprint == self.ckcc_xfp
 
-        raw_psbt = self.build_psbt(tx)
+        # makes PSBT required
+        raw_psbt = build_psbt(tx, self.my_wallet)
 
-        #open('debug.psbt', 'wb').write(out_fd.getvalue())
+        cc_finalize = not (type(self.my_wallet) is Multisig_Wallet)
 
         try:
             try:
                 self.handler.show_message("Authorize Transaction...")
 
-                client.sign_transaction_start(raw_psbt, True)
+                client.sign_transaction_start(raw_psbt, cc_finalize)
 
                 while 1:
                     # How to kill some time, without locking UI?
@@ -545,7 +418,7 @@ class Coldcard_KeyStore(Hardware_KeyStore):
                 rlen, rsha = resp
             
                 # download the resulting txn.
-                new_raw = client.download_file(rlen, rsha)
+                raw_resp = client.download_file(rlen, rsha)
 
             finally:
                 self.handler.finished()
@@ -559,8 +432,18 @@ class Coldcard_KeyStore(Hardware_KeyStore):
             self.give_error(e, True)
             return
 
-        # trust the coldcard to re-searilize final product right?
-        tx.update(bh2u(new_raw))
+        if cc_finalize:
+            # We trust the coldcard to re-serialize final transaction ready to go
+            tx.update(bh2u(raw_resp))
+        else:
+            # apply partial signatures back into txn
+            psbt = BasicPSBT()
+            psbt.parse(raw_resp, client.label())
+
+            merge_sigs_from_psbt(tx, psbt)
+
+            # caller's logic looks at tx now and if it's sufficiently signed,
+            # will send it if that's the user's intent.
 
     @staticmethod
     def _encode_txin_type(txin_type):
@@ -593,11 +476,30 @@ class Coldcard_KeyStore(Hardware_KeyStore):
             self.logger.exception('')
             self.handler.show_error(exc)
 
+    @wrap_busy
+    def show_p2sh_address(self, M, script, xfp_paths, txin_type):
+        client = self.get_client()
+        addr_fmt = self._encode_txin_type(txin_type)
+        try:
+            try:
+                self.handler.show_message(_("Showing address ..."))
+                dev_addr = client.show_p2sh_address(M, xfp_paths, script, addr_fmt=addr_fmt)
+                # we could double check address here
+            finally:
+                self.handler.finished()
+        except CCProtoError as exc:
+            self.logger.exception('Error showing address')
+            self.handler.show_error('{}\n\n{}'.format(
+                _('Error showing address') + ':', str(exc)))
+        except BaseException as exc:
+            self.logger.exception('')
+            self.handler.show_error(exc)
+
 
 
 class ColdcardPlugin(HW_PluginBase):
     keystore_class = Coldcard_KeyStore
-    minimum_library = (0, 7, 2)
+    minimum_library = (0, 7, 7)
     client = None
 
     DEVICE_IDS = [
@@ -605,8 +507,7 @@ class ColdcardPlugin(HW_PluginBase):
         (COINKITE_VID, CKCC_SIMULATED_PID)
     ]
 
-    #SUPPORTED_XTYPES = ('standard', 'p2wpkh-p2sh', 'p2wpkh', 'p2wsh-p2sh', 'p2wsh')
-    SUPPORTED_XTYPES = ('standard', 'p2wpkh', 'p2wpkh-p2sh')
+    SUPPORTED_XTYPES = ('standard', 'p2wpkh-p2sh', 'p2wpkh', 'p2wsh-p2sh', 'p2wsh')
 
     def __init__(self, parent, config, name):
         HW_PluginBase.__init__(self, parent, config, name)
@@ -682,31 +583,103 @@ class ColdcardPlugin(HW_PluginBase):
         return xpub
 
     def get_client(self, keystore, force_pair=True):
-        # All client interaction should not be in the main GUI thread
+        # Acquire a connection to the hardware device (via USB)
         devmgr = self.device_manager()
         handler = keystore.handler
         with devmgr.hid_lock:
             client = devmgr.client_for_keystore(self, handler, keystore, force_pair)
-        # returns the client for a given keystore. can use xpub
-        #if client:
-        #    client.used()
+
         if client is not None:
             client.ping_check()
+
         return client
 
+    @staticmethod
+    def export_ms_wallet(wallet, fp, name):
+        # Build the text file Coldcard needs to understand the multisig wallet
+        # it is participating in. All involved Coldcards can share same file.
+
+        print('# Exported from Electrum', file=fp)
+        print(f'Name: {name:.20s}', file=fp)
+        print(f'Policy: {wallet.m} of {wallet.n}', file=fp)
+        print(f'Format: {wallet.txin_type.upper()}' , file=fp)
+
+        xpubs = []
+        derivs = set()
+        for xp, ks in zip(wallet.get_master_public_keys(), wallet.get_keystores()):
+            xfp = xfp_for_keystore(ks)
+            dd = getattr(ks, 'derivation', 'm')
+
+            xpubs.append( (xfp2str(xfp), xp, dd) )
+            derivs.add(dd)
+
+        # Derivation doesn't matter too much to the Coldcard, since it
+        # uses key path data from PSBT or USB request as needed. However,
+        # if there is a clear value, provide it.
+        if len(derivs) == 1:
+            print("Derivation: " + derivs.pop(), file=fp)
+
+        print('', file=fp)
+
+        assert len(xpubs) == wallet.n
+        for xfp, xp, dd in xpubs:
+            if derivs:
+                # show as a comment if unclear
+                print(f'# derivation: {dd}', file=fp)
+
+            print(f'{xfp}: {xp}\n', file=fp)
+
     def show_address(self, wallet, address, keystore=None):
         if keystore is None:
             keystore = wallet.get_keystore()
         if not self.show_address_helper(wallet, address, keystore):
             return
 
+        txin_type = wallet.get_txin_type(address)
+
         # Standard_Wallet => not multisig, must be bip32
-        if type(wallet) is not Standard_Wallet:
+        if type(wallet) is Standard_Wallet:
+            sequence = wallet.get_address_index(address)
+            keystore.show_address(sequence, txin_type)
+        elif type(wallet) is Multisig_Wallet:
+            # More involved for P2SH/P2WSH addresses: need M, and all public keys, and their
+            # derivation paths. Must construct script, and track fingerprints+paths for
+            # all those keys
+
+            pubkeys = wallet.get_public_keys(address)
+
+            xfps = []
+            for xp, ks in zip(wallet.get_master_public_keys(), wallet.get_keystores()):
+                path = "%s/%d/%d" % (getattr(ks, 'derivation', 'm'),
+                                        *wallet.get_address_index(address))
+
+                # need master XFP for each co-signers
+                ks_xfp = xfp_for_keystore(ks)
+                xfps.append(unpacked_xfp_path(ks_xfp, path))
+
+            # put into BIP45 (sorted) order
+            pkx = list(sorted(zip(pubkeys, xfps)))
+
+            script = bfh(multisig_script([pk for pk,xfp in pkx], wallet.m))
+
+            keystore.show_p2sh_address(wallet.m, script, [xfp for pk,xfp in pkx], txin_type)
+
+        else:
             keystore.handler.show_error(_('This function is only available for standard wallets when using {}.').format(self.device))
             return
 
-        sequence = wallet.get_address_index(address)
-        txin_type = wallet.get_txin_type(address)
-        keystore.show_address(sequence, txin_type)
+    @classmethod
+    def link_wallet(cls, wallet):
+        # PROBLEM: wallet.sign_transaction() does not pass in the wallet to the individual
+        # keystores, and we need to know about our co-signers at that time.
+        for ks in wallet.get_keystores():
+            if type(ks) == Coldcard_KeyStore:
+                if not ks.my_wallet:
+                    ks.my_wallet = wallet
+
+    @hook
+    def make_unsigned_transaction(self, wallet, tx):
+        # - capture wallet containing each keystore early in the process
+        self.link_wallet(wallet)
 
 # EOF
diff --git a/electrum/plugins/coldcard/qt.py b/electrum/plugins/coldcard/qt.py
index 28801f433..294c89f5b 100644
--- a/electrum/plugins/coldcard/qt.py
+++ b/electrum/plugins/coldcard/qt.py
@@ -1,18 +1,27 @@
-import time
+import time, os
 from functools import partial
 
 from PyQt5.QtCore import Qt, pyqtSignal
 from PyQt5.QtWidgets import QPushButton, QLabel, QVBoxLayout, QWidget, QGridLayout
+from PyQt5.QtWidgets import QFileDialog
 
 from electrum.i18n import _
 from electrum.plugin import hook
-from electrum.wallet import Standard_Wallet
-from electrum.gui.qt.util import WindowModalDialog, CloseButton, get_parent_main_window
+from electrum.wallet import Standard_Wallet, Multisig_Wallet
+from electrum.gui.qt.util import WindowModalDialog, CloseButton, get_parent_main_window, Buttons
+from electrum.transaction import Transaction
 
-from .coldcard import ColdcardPlugin
+from .coldcard import ColdcardPlugin, xfp2str
 from ..hw_wallet.qt import QtHandlerBase, QtPluginBase
 from ..hw_wallet.plugin import only_hook_if_libraries_available
 
+from binascii import a2b_hex
+from base64 import b64encode, b64decode
+
+from .basic_psbt import BasicPSBT
+from .build_psbt import build_psbt, merge_sigs_from_psbt, recover_tx_from_psbt
+
+CC_DEBUG = False
 
 class Plugin(ColdcardPlugin, QtPluginBase):
     icon_unpaired = "coldcard_unpaired.png"
@@ -24,22 +33,62 @@ class Plugin(ColdcardPlugin, QtPluginBase):
     @only_hook_if_libraries_available
     @hook
     def receive_menu(self, menu, addrs, wallet):
-        if type(wallet) is not Standard_Wallet:
-            return
-        keystore = wallet.get_keystore()
+        # Context menu on each address in the Addresses Tab, right click...
+
+        if type(wallet) is Standard_Wallet:
+            keystore = wallet.get_keystore()
+        else:
+            # find if any devices are connected and ready to go, use first of those.
+            for ks in wallet.get_keystores():
+                if ks.has_usable_connection_with_device():
+                    keystore = ks
+                    break
+            else:
+                # don't hook into menu
+                return
+
         if type(keystore) == self.keystore_class and len(addrs) == 1:
             def show_address():
-                keystore.thread.add(partial(self.show_address, wallet, addrs[0]))
-            menu.addAction(_("Show on Coldcard"), show_address)
+                keystore.thread.add(partial(self.show_address, wallet, addrs[0], keystore=keystore))
+            menu.addAction(_("Show on Coldcard ({})").format(keystore.label), show_address)
+
+    @only_hook_if_libraries_available
+    @hook
+    def wallet_info_buttons(self, main_window, dialog):
+        # user is about to see the "Wallet Information" dialog
+        # - add a button if multisig wallet, and a Coldcard is a cosigner.
+        wallet = main_window.wallet
+
+        if type(wallet) is not Multisig_Wallet:
+            return
+
+        if not any(type(ks) == self.keystore_class for ks in wallet.get_keystores()):
+            # doesn't involve a Coldcard wallet, hide feature
+            return
+
+        btn = QPushButton(_("Export for Coldcard"))
+        btn.clicked.connect(lambda unused: self.export_multisig_setup(main_window, wallet))
+
+        return Buttons(btn, CloseButton(dialog))
+
+    def export_multisig_setup(self, main_window, wallet):
+
+        basename = wallet.basename().rsplit('.', 1)[0]        # trim .json
+        name = f'{basename}-cc-export.txt'.replace(' ', '-')
+        fileName = main_window.getSaveFileName(_("Select where to save the setup file"),
+                                                        name, "*.txt")
+        if fileName:
+            with open(fileName, "wt") as f:
+                ColdcardPlugin.export_ms_wallet(wallet, f, basename)
+            main_window.show_message(_("Wallet setup file exported successfully"))
 
     @only_hook_if_libraries_available
     @hook
     def transaction_dialog(self, dia):
         # see gui/qt/transaction_dialog.py
 
-        keystore = dia.wallet.get_keystore()
-        if type(keystore) != self.keystore_class:
-            # not a Coldcard wallet, hide feature
+        # if not a Coldcard wallet, hide feature
+        if not any(type(ks) == self.keystore_class for ks in dia.wallet.get_keystores()):
             return
 
         # - add a new button, near "export"
@@ -65,23 +114,110 @@ class Plugin(ColdcardPlugin, QtPluginBase):
         assert type(keystore) == self.keystore_class
 
         # convert to PSBT
-        raw_psbt = keystore.build_psbt(tx, wallet=dia.wallet)
+        build_psbt(tx, dia.wallet)
 
-        name = (dia.wallet.basename() + time.strftime('-%y%m%d-%H%M.psbt')).replace(' ', '-')
+        name = (dia.wallet.basename() + time.strftime('-%y%m%d-%H%M.psbt'))\
+                    .replace(' ', '-').replace('.json', '')
         fileName = dia.main_window.getSaveFileName(_("Select where to save the PSBT file"),
                                                         name, "*.psbt")
         if fileName:
             with open(fileName, "wb+") as f:
-                f.write(raw_psbt)
+                f.write(tx.raw_psbt)
             dia.show_message(_("Transaction exported successfully"))
             dia.saved = True
 
     def show_settings_dialog(self, window, keystore):
         # When they click on the icon for CC we come here.
-        device_id = self.choose_device(window, keystore)
-        if device_id:
-            CKCCSettingsDialog(window, self, keystore, device_id).exec_()
+        # - doesn't matter if device not connected, continue
+        CKCCSettingsDialog(window, self, keystore).exec_()
 
+    @hook
+    def init_menubar_tools(self, main_window, tools_menu):
+        # add some PSBT-related tools to the "Load Transaction" menu.
+        rt = main_window.raw_transaction_menu
+        wallet = main_window.wallet
+        rt.addAction(_("From &PSBT File or Files"), lambda: self.psbt_combiner(main_window, wallet))
+
+    def psbt_combiner(self, window, wallet):
+        title = _("Select the PSBT file to load or PSBT files to combine")
+        directory = ''
+        fnames, __ = QFileDialog.getOpenFileNames(window, title, directory, "PSBT Files (*.psbt)")
+
+        psbts = []
+        for fn in fnames:
+            try:
+                with open(fn, "rb") as f:
+                    raw = f.read()
+
+                    psbt = BasicPSBT()
+                    psbt.parse(raw, fn)
+
+                    psbts.append(psbt)
+            except (AssertionError, ValueError, IOError, os.error) as reason:
+                window.show_critical(_("Electrum was unable to open your PSBT file") + "\n" + str(reason), title=_("Unable to read file"))
+                return
+
+        warn = []
+        if not psbts: return        # user picked nothing
+
+        # Consistency checks and warnings.
+        try:
+            first = psbts[0]
+            for p in psbts:
+                fn = os.path.split(p.filename)[1]
+
+                assert (p.txn == first.txn), \
+                    "All must relate to the same unsigned transaction."
+
+                for idx, inp in enumerate(p.inputs):
+                    if not inp.part_sigs:
+                        warn.append(fn + ':\n  ' + _("No partial signatures found for input #%d") % idx)
+
+                    assert first.inputs[idx].redeem_script == inp.redeem_script, "Mismatched redeem scripts"
+                    assert first.inputs[idx].witness_script == inp.witness_script, "Mismatched witness"
+                    
+        except AssertionError as exc:
+            # Fatal errors stop here.
+            window.show_critical(str(exc),
+                    title=_("Unable to combine PSBT files, check: ")+p.filename)
+            return
+
+        if warn:
+            # Lots of potential warnings...
+            window.show_warning('\n\n'.join(warn), title=_("PSBT warnings"))
+
+        # Construct an Electrum transaction object from data in first PSBT file.
+        try:
+            tx = recover_tx_from_psbt(first, wallet)
+        except BaseException as exc:
+            if CC_DEBUG:
+                from PyQt5.QtCore import pyqtRemoveInputHook; pyqtRemoveInputHook()
+                import pdb; pdb.post_mortem()
+            window.show_critical(str(exc), title=_("Unable to understand PSBT file"))
+            return
+
+        # Combine the signatures from all the PSBTS (may do nothing if unsigned PSBTs)
+        for p in psbts:
+            try:
+                merge_sigs_from_psbt(tx, p)
+            except BaseException as exc:
+                if CC_DEBUG:
+                    from PyQt5.QtCore import pyqtRemoveInputHook; pyqtRemoveInputHook()
+                    import pdb; pdb.post_mortem()
+                window.show_critical("Unable to merge signatures: " + str(exc), 
+                    title=_("Unable to combine PSBT file: ") + p.filename)
+                return
+
+        # Display result, might not be complete yet, but hopefully it's ready to transmit!
+        if len(psbts) == 1:
+            desc = _("From PSBT file: ") + fn
+        else:
+            desc = _("Combined from %d PSBT files") % len(psbts)
+
+        # need to associated our pluging to this wallet
+        ColdcardPlugin.link_wallet(wallet)
+
+        window.show_transaction(tx, desc)
 
 class Coldcard_Handler(QtHandlerBase):
     setup_signal = pyqtSignal()
@@ -112,21 +248,25 @@ class Coldcard_Handler(QtHandlerBase):
         return
 
 class CKCCSettingsDialog(WindowModalDialog):
-    '''This dialog doesn't require a device be paired with a wallet.
-    We want users to be able to wipe a device even if they've forgotten
-    their PIN.'''
 
-    def __init__(self, window, plugin, keystore, device_id):
+    def __init__(self, window, plugin, keystore):
         title = _("{} Settings").format(plugin.device)
         super(CKCCSettingsDialog, self).__init__(window, title)
         self.setMaximumWidth(540)
 
+        # Note: Coldcard may **not** be connected at present time. Keep working!
+
         devmgr = plugin.device_manager()
-        config = devmgr.config
-        handler = keystore.handler
+        #config = devmgr.config
+        #handler = keystore.handler
         self.thread = thread = keystore.thread
+        self.keystore = keystore
 
         def connect_and_doit():
+            # Attempt connection to device, or raise.
+            device_id = plugin.choose_device(window, keystore)
+            if not device_id:
+                raise RuntimeError("Device not connected")
             client = devmgr.client_by_id(device_id)
             if not client:
                 raise RuntimeError("Device not connected")
@@ -148,13 +288,14 @@ class CKCCSettingsDialog(WindowModalDialog):
         y = 3
 
         rows = [
+            ('xfp', _("Master Fingerprint")),
+            ('serial', _("USB Serial")),
             ('fw_version', _("Firmware Version")),
             ('fw_built', _("Build Date")),
             ('bl_version', _("Bootloader")),
-            ('xfp', _("Master Fingerprint")),
-            ('serial', _("USB Serial")),
         ]
         for row_num, (member_name, label) in enumerate(rows):
+            # XXX we know xfp already, even if not connected
             widget = QLabel('<tt>000000000000')
             widget.setTextInteractionFlags(Qt.TextSelectableByMouse | Qt.TextSelectableByKeyboard)
 
@@ -164,7 +305,7 @@ class CKCCSettingsDialog(WindowModalDialog):
             y += 1
         body_layout.addLayout(grid)
 
-        upg_btn = QPushButton('Upgrade')
+        upg_btn = QPushButton(_('Upgrade'))
         #upg_btn.setDefault(False)
         def _start_upgrade():
             thread.add(connect_and_doit, on_success=self.start_upgrade)
@@ -177,13 +318,22 @@ class CKCCSettingsDialog(WindowModalDialog):
         dialog_vbox = QVBoxLayout(self)
         dialog_vbox.addWidget(body)
 
-        # Fetch values and show them
-        thread.add(connect_and_doit, on_success=self.show_values)
+        # Fetch firmware/versions values and show them.
+        thread.add(connect_and_doit, on_success=self.show_values, on_error=self.show_placeholders)
+
+    def show_placeholders(self, unclear_arg):
+        # device missing, so hide lots of detail.
+        self.xfp.setText('<tt>%s' % xfp2str(self.keystore.ckcc_xfp))
+        self.serial.setText('(not connected)')
+        self.fw_version.setText('')
+        self.fw_built.setText('')
+        self.bl_version.setText('')
 
     def show_values(self, client):
+
         dev = client.dev
 
-        self.xfp.setText('<tt>0x%08x' % dev.master_fingerprint)
+        self.xfp.setText('<tt>%s' % xfp2str(dev.master_fingerprint))
         self.serial.setText('<tt>%s' % dev.serial)
 
         # ask device for versions: allow extras for future
diff --git a/electrum/plugins/hw_wallet/qt.py b/electrum/plugins/hw_wallet/qt.py
index f99cb0281..b348c7adc 100644
--- a/electrum/plugins/hw_wallet/qt.py
+++ b/electrum/plugins/hw_wallet/qt.py
@@ -265,4 +265,4 @@ class QtPluginBase(object):
             else:
                 addr = uri.get('address')
             keystore.thread.add(partial(plugin.show_address, wallet, addr, keystore))
-        receive_address_e.addButton("eye1.png", show_address, _("Show on {}").format(plugin.device))
+        receive_address_e.addButton("eye1.png", show_address, _("Show on {}").format(keystore.label))