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hsmd: add BIP86 wire scaffolding (derive/check), no behavior yet

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Here's some *foreshadowing* for what's to come. Here's what we're aiming for with our derivation flow:

Derivation split (hardened vs unhardened)
========================================

        ┌───────────────┐
        │      HSM      │  (secrets live here)
        │               │
        │  BIP39 → seed (64B)
        │       ↓
        │   m/86'/0'/0'           ← derive hardened base (private)
        │       ↓ (neuter)
        │   BIP86 base xpub       ← public-only + chain code
        │       ↓
        │  [send once over wire]
        └───────────────┘
                │
                ▼
        ┌───────────────────────┐
        │ lightningd / wallet   │
        │                       │
        │  local (unhardened) derivations:
        │    /0/i  → external
        │    /1/i  → change
        │                       │
        │  P2TR(BIP86) from pubkey_i
        │  (optionally: CHECK with HSM)
        └───────────────────────┘

We want to do part of the derivation inside hsmd and then send this base "pubkey" over the wire so our wallet can do the remaining derivation based on the address type and index. This lays the foundation for the base key wire message.
This commit is contained in:
Sangbida Chaudhuri
2025-10-24 13:57:45 +10:30
committed by Rusty Russell
parent fc981f4d30
commit 121fcfc92b
3 changed files with 34 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
hsmd/hsmd.c
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@@ -750,6 +750,8 @@ static struct io_plan *handle_client(struct io_conn *conn, struct client *c)
case WIRE_HSMD_SIGN_REMOTE_HTLC_TO_US:
case WIRE_HSMD_SIGN_DELAYED_PAYMENT_TO_US:
case WIRE_HSMD_CHECK_PUBKEY:
case WIRE_HSMD_DERIVE_BIP86_KEY:
case WIRE_HSMD_CHECK_BIP86_PUBKEY:
case WIRE_HSMD_SIGN_ANY_PENALTY_TO_US:
case WIRE_HSMD_SIGN_ANY_DELAYED_PAYMENT_TO_US:
case WIRE_HSMD_SIGN_ANY_REMOTE_HTLC_TO_US:
@@ -797,6 +799,8 @@ static struct io_plan *handle_client(struct io_conn *conn, struct client *c)
case WIRE_HSMD_PREAPPROVE_INVOICE_CHECK_REPLY:
case WIRE_HSMD_PREAPPROVE_KEYSEND_CHECK_REPLY:
case WIRE_HSMD_CHECK_PUBKEY_REPLY:
case WIRE_HSMD_DERIVE_BIP86_KEY_REPLY:
case WIRE_HSMD_CHECK_BIP86_PUBKEY_REPLY:
case WIRE_HSMD_SIGN_ANCHORSPEND_REPLY:
case WIRE_HSMD_SIGN_HTLC_TX_MINGLE_REPLY:
case WIRE_HSMD_SIGN_ANY_CANNOUNCEMENT_REPLY:

16
hsmd/hsmd_wire.csv
View File

@@ -196,6 +196,14 @@ msgdata,hsmd_preapprove_keysend_check,check_only,bool,
msgtype,hsmd_preapprove_keysend_check_reply,152
msgdata,hsmd_preapprove_keysend_check_reply,approved,bool,
# Derive BIP86 key using path m/86'/0'/0'/change/address_index
msgtype,hsmd_derive_bip86_key,54
msgdata,hsmd_derive_bip86_key,index,u32,
msgdata,hsmd_derive_bip86_key,is_change,bool,
msgtype,hsmd_derive_bip86_key_reply,154
msgdata,hsmd_derive_bip86_key_reply,bip86_base,ext_key,
# Give me ECDH(node-id-secret,point)
msgtype,hsmd_ecdh_req,1
msgdata,hsmd_ecdh_req,point,pubkey,
@@ -447,6 +455,14 @@ msgdata,hsmd_check_pubkey,pubkey,pubkey,
msgtype,hsmd_check_pubkey_reply,128
msgdata,hsmd_check_pubkey_reply,ok,bool,
# Sanity check this BIP86 pubkey derivation is correct (unhardened only)
msgtype,hsmd_check_bip86_pubkey,56
msgdata,hsmd_check_bip86_pubkey,index,u32,
msgdata,hsmd_check_bip86_pubkey,pubkey,pubkey,
msgtype,hsmd_check_bip86_pubkey_reply,156
msgdata,hsmd_check_bip86_pubkey_reply,ok,bool,
msgtype,hsmd_sign_anchorspend,147
msgdata,hsmd_sign_anchorspend,peerid,node_id,
msgdata,hsmd_sign_anchorspend,channel_dbid,u64,
Can't render this file because it contains an unexpected character in line 179 and column 43.

14
hsmd/libhsmd.c
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@@ -154,6 +154,8 @@ bool hsmd_check_client_capabilities(struct hsmd_client *client,
case WIRE_HSMD_PREAPPROVE_KEYSEND_CHECK:
case WIRE_HSMD_DERIVE_SECRET:
case WIRE_HSMD_CHECK_PUBKEY:
case WIRE_HSMD_DERIVE_BIP86_KEY:
case WIRE_HSMD_CHECK_BIP86_PUBKEY:
case WIRE_HSMD_SIGN_ANY_PENALTY_TO_US:
case WIRE_HSMD_SIGN_ANY_DELAYED_PAYMENT_TO_US:
case WIRE_HSMD_SIGN_ANY_REMOTE_HTLC_TO_US:
@@ -202,6 +204,8 @@ bool hsmd_check_client_capabilities(struct hsmd_client *client,
case WIRE_HSMD_PREAPPROVE_KEYSEND_CHECK_REPLY:
case WIRE_HSMD_DERIVE_SECRET_REPLY:
case WIRE_HSMD_CHECK_PUBKEY_REPLY:
case WIRE_HSMD_DERIVE_BIP86_KEY_REPLY:
case WIRE_HSMD_CHECK_BIP86_PUBKEY_REPLY:
case WIRE_HSMD_SIGN_ANCHORSPEND_REPLY:
case WIRE_HSMD_SIGN_HTLC_TX_MINGLE_REPLY:
case WIRE_HSMD_SIGN_ANY_CANNOUNCEMENT_REPLY:
@@ -2283,6 +2287,13 @@ u8 *hsmd_handle_client_message(const tal_t *ctx, struct hsmd_client *client,
return handle_derive_secret(client, msg);
case WIRE_HSMD_CHECK_PUBKEY:
return handle_check_pubkey(client, msg);
case WIRE_HSMD_DERIVE_BIP86_KEY:
case WIRE_HSMD_CHECK_BIP86_PUBKEY:
/* Not implemented yet */
return hsmd_status_bad_request_fmt(
client, msg,
"Message of type %s not implemented yet",
hsmd_wire_name(fromwire_peektype(msg)));
case WIRE_HSMD_SIGN_ANY_DELAYED_PAYMENT_TO_US:
return handle_sign_any_delayed_payment_to_us(client, msg);
case WIRE_HSMD_SIGN_ANY_REMOTE_HTLC_TO_US:
@@ -2332,7 +2343,9 @@ u8 *hsmd_handle_client_message(const tal_t *ctx, struct hsmd_client *client,
case WIRE_HSMD_PREAPPROVE_KEYSEND_REPLY:
case WIRE_HSMD_PREAPPROVE_INVOICE_CHECK_REPLY:
case WIRE_HSMD_PREAPPROVE_KEYSEND_CHECK_REPLY:
case WIRE_HSMD_DERIVE_BIP86_KEY_REPLY:
case WIRE_HSMD_CHECK_PUBKEY_REPLY:
case WIRE_HSMD_CHECK_BIP86_PUBKEY_REPLY:
case WIRE_HSMD_SIGN_ANCHORSPEND_REPLY:
case WIRE_HSMD_SIGN_HTLC_TX_MINGLE_REPLY:
case WIRE_HSMD_SIGN_ANY_CANNOUNCEMENT_REPLY:
@@ -2351,6 +2364,7 @@ u8 *hsmd_init(const u8 *secret_data, size_t secret_len, const u64 hsmd_version,
struct node_id node_id;
static const u32 capabilities[] = {
WIRE_HSMD_CHECK_PUBKEY,
WIRE_HSMD_CHECK_BIP86_PUBKEY,
WIRE_HSMD_SIGN_ANY_DELAYED_PAYMENT_TO_US,
WIRE_HSMD_SIGN_ANCHORSPEND,
WIRE_HSMD_SIGN_HTLC_TX_MINGLE,