harding · March 6, 2024 19:55 · Mar 6, 2024
diff --git a/casa-helper.sh b/casa-helper.sh
@@ -0,0 +1,164 @@
+#!/bin/bash -eu
+
+# NO WARRANTY PROVIDED OR IMPLIED.  USE AT YOUR OWN RISK.
+
+###########
+## Paths ##
+###########
+# This is the keypath provided in the Casa recovery email minus the "m"
+KEYPATH="/49/0/0"
+
+# Sub-paths.  This not provided by Casa in their recovery
+# instructions but seems to follow the Electrum v4 default, which is
+# - External: /0/*
+# - Internal (change): /1/*
+EXTERNAL_SUBPATH="/0/*"
+INTERNAL_SUBPATH="/1/*"
+
+###########
+## Xpubs ##
+###########
+# All operations with this script require you to enter the extended
+# pubkeys (xpubs) for all five signing keys.  If you want to use the
+# descriptors for address verification or signing, you will also need to
+# provide their fingerprints (FPs).
+#
+# The Casa recovery email includes ypubs (not xpubs) for the mobile and
+# recovery keys.  You will need to convert those ypubs to xpubs, which
+# can be done with the following tool:
+#
+#     https://jlopp.github.io/xpub-converter/
+#
+# Note: you can use that page offline for additional privacy, although
+# the operator of that website is currently Casa's CTO, so I ran it
+# online
+
+MOBILE_FP=FILL_THIS_IN
+MOBILE_XPUB=FILL_THIS_IN
+
+RECOVERY_FP=FILL_THIS_IN
+RECOVERY_XPUB=FILL_THIS_IN
+
+# For HW wallets, use HWI to get the xpubs.  E.g., plug in the device,
+# enter its pin (or use `hwi promptpin`), use `hwi enumerate` to get
+# it's fingerprint, and use something like this to get its xpub:
+#    hwi -t ledger getxpub m$KEYPATH
+
+HW1_FP=FILL_THIS_IN
+HW1_XPUB=FILL_THIS_IN
+
+HW2_FP=FILL_THIS_IN
+HW2_XPUB=FILL_THIS_IN
+
+HW3_FP=FILL_THIS_IN
+HW3_XPUB=FILL_THIS_IN
+
+############################## END CONFIGURATION ###################################
+## You shouldn't need to edit anything below this point, except for special cases ##
+####################################################################################
+
+# sh: P2SH, wsh: witness script hash, sortedmulti: multisig with keys in
+# BIP67 order, 3: 3-of-n multisig
+external_descriptor="sh(wsh(sortedmulti(3,"
+internal_descriptor="sh(wsh(sortedmulti(3,"
+
+# The five fingerprints and xpubs
+external_descriptor="${external_descriptor}[$MOBILE_FP$KEYPATH]$MOBILE_XPUB$EXTERNAL_SUBPATH,"
+internal_descriptor="${internal_descriptor}[$MOBILE_FP$KEYPATH]$MOBILE_XPUB$INTERNAL_SUBPATH,"
+
+external_descriptor="${external_descriptor}[$RECOVERY_FP$KEYPATH]$RECOVERY_XPUB$EXTERNAL_SUBPATH,"
+internal_descriptor="${internal_descriptor}[$RECOVERY_FP$KEYPATH]$RECOVERY_XPUB$INTERNAL_SUBPATH,"
+
+external_descriptor="${external_descriptor}[$HW1_FP$KEYPATH]$HW1_XPUB$EXTERNAL_SUBPATH,"
+internal_descriptor="${internal_descriptor}[$HW1_FP$KEYPATH]$HW1_XPUB$INTERNAL_SUBPATH,"
+
+external_descriptor="${external_descriptor}[$HW2_FP$KEYPATH]$HW2_XPUB$EXTERNAL_SUBPATH,"
+internal_descriptor="${internal_descriptor}[$HW2_FP$KEYPATH]$HW2_XPUB$INTERNAL_SUBPATH,"
+
+external_descriptor="${external_descriptor}[$HW3_FP$KEYPATH]$HW3_XPUB$EXTERNAL_SUBPATH"
+internal_descriptor="${internal_descriptor}[$HW3_FP$KEYPATH]$HW3_XPUB$INTERNAL_SUBPATH"
+
+# Close the sh/wsh/sortedmulti parens
+external_descriptor="${external_descriptor})))"
+internal_descriptor="${internal_descriptor})))"
+
+# Validate the descriptors and update them to include a checksum
+external_descriptor=$( bitcoin-cli getdescriptorinfo "$external_descriptor" | jq -r .descriptor )
+if [ "$external_descriptor" == "" ]; then
+  echo "Error parsing external descriptor.  Check fingerprints and keys for typos.  Terminating script..."
+  exit 1
+fi
+internal_descriptor=$( bitcoin-cli getdescriptorinfo "$internal_descriptor" | jq -r .descriptor )
+if [ "$internal_descriptor" == "" ]; then
+  echo "Error parsing internal descriptor.  Check fingerprints and keys for typos.  Terminating script..."
+  exit 1
+fi
+
+case "$1" in
+  get_descriptors)
+    echo "$external_descriptor"
+    echo "$internal_descriptor"
+  ;;
+
+  derive_receiving_addresses)
+    # Only derive receiving (external) addresses
+    bitcoin-cli deriveaddresses "$external_descriptor" 1000
+  ;;
+
+  # Note, if you get a "ripemd160 not supported error", see https://github.com/bitcoin-core/HWI/issues/656
+  verify_receive_address)
+    shift
+    if [ $# -lt 1 ] ; then
+      echo "$0 verify_receive_address <address> <hwi_arguments>"
+      exit 1
+    fi
+    ADDRESS="$1" ; shift
+
+    index=$( $0 derive_receiving_addresses | jq 'index("'$ADDRESS'")' )
+    if ! echo "$index" | grep -q '^[0-9]\+$' ; then
+      echo "Address not found: $ADDRESS"
+      exit 1
+    fi
+
+    # Our original ranged descriptor looks like:
+    #    sh(wsh(sortedmulti(3,[.../49/0/0]xpub.../0/*,....
+    # We need a single-address descriptor that looks like:
+    #    sh(wsh(sortedmulti(3,[.../49/0/0/]xpub.../0/$index,....
+    address_descriptor=$( echo "$external_descriptor" | sed """
+       # Remove the checksum
+       s/#.*//;
+       # Replace the range "*" with the particular index
+       s/\*/$index/g;
+    """ )
+    # Give the individual descriptor a checksum
+    address_descriptor=$( bitcoin-cli getdescriptorinfo "$address_descriptor" | jq -r .descriptor )
+
+    derived_address=$( bitcoin-cli deriveaddresses "$address_descriptor" | jq -r '.[]' )
+    if [ "$ADDRESS" != "$derived_address" ] ; then
+      echo "Something went wrong.  Provided address $ADDRESS not the same as computed address $derived_address.  Exiting..."
+      exit 1
+    fi
+
+    echo "Press enter to run the following command to verify address $ADDRESS:"
+    echo
+    echo "    hwi" "$@" displayaddress --desc "$address_descriptor"
+    echo
+    echo "Press CTRL-C if any necessary parameters to hwi, like -t and -d, are missing"
+    echo "Also remember to unlock your device with its pin before pressing enter"
+    read
+
+    hwi "$@" displayaddress --desc "$address_descriptor"
+
+  ;;
+
+  scan_utxos)
+    # NB: increase the ranges if you've sent or received more than that
+    # number of payments using your Casa wallet.
+    bitcoin-cli scantxoutset start '[{"desc": "'"$internal_descriptor"'", "range": 1000}, {"desc": "'"$external_descriptor"'", "range": 1000}]'
+  ;;
+
+  *)
+    echo "Unknown command: $1"
+    exit 1
+  ;;
+esac