Merge pull request 'feat(cash-in): secure create_withdraw nostr-transport RPC (#31)' (#32) from feat/secure-cashin-rpc into main

Reviewed-on: #32

__init__.py

@@ -4,6 +4,7 @@ from fastapi import APIRouter
 from lnbits.tasks import create_permanent_unique_task
 from loguru import logger
 
+from .cashin_transport import register_create_withdraw_rpc
 from .crud import db
 from .nostr_transport_roster import register_with_lnbits as register_roster_with_lnbits
 from .tasks import wait_for_cassette_state_events, wait_for_paid_invoices
@@ -13,9 +14,7 @@ from .views_api import spirekeeper_api_router
 logger.info("spirekeeper v2 loaded")
 
 
-spirekeeper_ext: APIRouter = APIRouter(
+spirekeeper_ext: APIRouter = APIRouter(prefix="/spirekeeper", tags=["DCA Admin"])
-    prefix="/spirekeeper", tags=["DCA Admin"]
-)
 spirekeeper_ext.include_router(spirekeeper_generic_router)
 spirekeeper_ext.include_router(spirekeeper_api_router)
 
@@ -57,6 +56,12 @@ def spirekeeper_start():
     # wallet, not an auto-created machine wallet. Soft-fails on lnbits
     # versions that don't yet expose `register_roster_resolver`.
     register_roster_with_lnbits()
+    # Secure cash-in (#31): register the `create_withdraw` nostr-transport RPC
+    # so the ATM requests a server-priced, server-stamped cash-in withdraw link
+    # over the bunker-signed transport — amount/fee/attribution derived
+    # server-side, never client-supplied. Soft-fails if `register_rpc` isn't
+    # exposed by this lnbits.
+    register_create_withdraw_rpc()
 
 
 __all__ = [

cashin_transport.py

@@ -0,0 +1,135 @@
+"""
+Secure cash-in: a `create_withdraw` nostr-transport RPC (aiolabs/spirekeeper#31).
+
+Mirrors withdraw's `lnurlw_create_link`, but cash-in-semantic. The ATM sends the
+gross `principal_sats` (the hardware-attested fiat value) over the bunker-signed
+kind-21000 transport; the operator side derives the fee, the NET withdraw
+amount, and the attribution **server-side** — none of it client-supplied. The
+customer claims the NET link; the payout carries the stamped `extra`
+(aiolabs/withdraw#3) so `_handle_payment` records the `cash_in` settlement with
+cryptographic attribution (the verified transport sender), exactly like the
+cash-out path.
+
+Why this exists: `lnurlw_create_link` takes `min/max_withdrawable` and `extra`
+straight from the client body, so an authenticated-but-malicious/buggy ATM could
+set the gross amount (no fee), forge `nostr_sender_pubkey`, or request an
+arbitrary amount. This RPC closes that by computing everything server-side.
+"""
+
+from __future__ import annotations
+
+from loguru import logger
+
+from .crud import get_machine_by_atm_pubkey_hex, get_super_config
+
+_RPC_NAME = "create_withdraw"
+
+
+async def handle_create_withdraw(auth, request) -> dict:
+    """nostr-transport RPC handler. `auth` is a WalletTypeInfo (the operator
+    wallet, roster-resolved from the verified sender); `request` is a
+    NostrRpcRequest with `body`, `sender_pubkey` (verified), and `event_id`."""
+    # Import withdraw lazily so registration never hard-depends on the withdraw
+    # extension being importable at startup; a missing dep fails the request,
+    # not the daemon.
+    try:
+        from withdraw.crud import create_withdraw_link
+        from withdraw.helpers import create_lnurl_from_baseurl
+        from withdraw.models import CreateWithdrawData
+    except ImportError as exc:
+        raise ValueError(
+            "withdraw extension unavailable; cannot mint a cash-in link"
+        ) from exc
+
+    body = request.body or {}
+
+    principal_sats = body.get("principal_sats")
+    if not isinstance(principal_sats, int) or principal_sats <= 0:
+        raise ValueError("principal_sats must be a positive integer")
+
+    # Attribution is the VERIFIED transport sender — never read it from the body.
+    sender = (request.sender_pubkey or "").lower()
+    if not sender:
+        raise ValueError("missing verified sender_pubkey")
+
+    machine = await get_machine_by_atm_pubkey_hex(sender)
+    if machine is None:
+        raise ValueError("no active machine for this signer")
+    # Defence in depth: the roster already resolved `auth.wallet` from `sender`;
+    # confirm it's the machine's own wallet before minting a payout link on it.
+    if machine.wallet_id != auth.wallet.id:
+        raise ValueError("machine wallet does not match the authenticated wallet")
+
+    super_config = await get_super_config()
+    if super_config is None:
+        raise ValueError("super_config not initialised")
+
+    # Per-tx cap (server-side; the bunker ACL / usage caps cannot see sats).
+    cap = getattr(super_config, "max_cash_in_sats", None)
+    if cap is not None and principal_sats > cap:
+        raise ValueError(
+            f"principal_sats {principal_sats} exceeds max_cash_in_sats {cap}"
+        )
+
+    # Round each leg independently so the split matches parse_settlement exactly
+    # (platform_fee + operator_fee == fee_sats → fee_mismatch_sats = 0).
+    platform_fee = round(
+        principal_sats * float(super_config.super_cash_in_fee_fraction)
+    )
+    operator_fee = round(principal_sats * float(machine.operator_cash_in_fee_fraction))
+    fee_sats = platform_fee + operator_fee
+    net_sats = principal_sats - fee_sats
+    if net_sats <= 0:
+        raise ValueError("fee >= principal; nothing to withdraw")
+
+    data = CreateWithdrawData(
+        title=body.get("title") or f"bitSpire Cash-In {machine.id}",
+        min_withdrawable=net_sats,
+        max_withdrawable=net_sats,
+        uses=1,
+        wait_time=int(body.get("wait_time") or 1),
+        is_unique=False,
+        extra={
+            "source": "bitspire",
+            "type": "cash_in",
+            "principal_sats": principal_sats,
+            "fee_sats": fee_sats,
+            "nostr_sender_pubkey": sender,
+            "nostr_event_id": body.get("client_ref") or request.event_id,
+        },
+    )
+    link = await create_withdraw_link(data, auth.wallet.id)
+    lnurl = create_lnurl_from_baseurl(link)
+    logger.info(
+        f"spirekeeper: create_withdraw machine={machine.id} "
+        f"principal={principal_sats} fee={fee_sats} (super={platform_fee} "
+        f"op={operator_fee}) net={net_sats} link={link.id}"
+    )
+    return {
+        "link_id": link.id,
+        # `Lnurl.__str__` is the raw URL — wallets need the bech32 LNURL1…
+        # (lud01). Mirror withdraw's `_populate_lnurl` field convention.
+        "lnurl": str(lnurl.bech32),
+        "lnurl_url": str(lnurl.url),
+        "net_sats": net_sats,
+        "principal_sats": principal_sats,
+        "fee_sats": fee_sats,
+    }
+
+
+def register_create_withdraw_rpc() -> None:
+    """Register `create_withdraw` with the lnbits nostr transport. Soft-fails if
+    the transport doesn't expose `register_rpc` (older lnbits)."""
+    try:
+        from lnbits.core.services.nostr_transport.dispatcher import (  # type: ignore
+            AUTH_WALLET,
+            register_rpc,
+        )
+    except ImportError:
+        logger.warning(
+            "spirekeeper: nostr-transport register_rpc unavailable; "
+            "'create_withdraw' not registered (secure cash-in over RPC disabled)"
+        )
+        return
+    register_rpc(_RPC_NAME, handle_create_withdraw, AUTH_WALLET)
+    logger.info("spirekeeper: registered nostr-transport RPC 'create_withdraw'")

migrations.py

@@ -845,3 +845,18 @@ async def m011_machine_npub_nullable(db):
         "CREATE UNIQUE INDEX IF NOT EXISTS dca_machines_wallet_id_uq "
         "ON dca_machines (wallet_id)"
     )
+
+
+async def m012_add_max_cash_in_sats(db):
+    """Server-side per-transaction cash-in ceiling (aiolabs/spirekeeper#31).
+
+    The secure `create_withdraw` RPC derives fee/net/attribution server-side,
+    but `principal_sats` is necessarily ATM-attested (only the hardware knows
+    how much cash went in). The bunker ACL / usage caps gate call *rate*, not
+    *sats*, so a single in-rate call could request an arbitrarily large payout.
+    `max_cash_in_sats` bounds that: the handler rejects a cash-in whose
+    principal exceeds it. NULL = no cap.
+    """
+    await db.execute(
+        "ALTER TABLE spirekeeper.super_config ADD COLUMN max_cash_in_sats INTEGER"
+    )

models.py

@@ -482,6 +482,10 @@ class SuperConfig(BaseModel):
     super_cash_in_fee_fraction: float = 0.0
     super_cash_out_fee_fraction: float = 0.0
     super_fee_wallet_id: str | None
+    # Per-transaction cash-in ceiling in sats (#31). The bunker ACL gates call
+    # rate, not sats, so this bounds a single ATM-attested principal. NULL = no
+    # cap.
+    max_cash_in_sats: int | None = None
     updated_at: datetime
 
 
@@ -489,6 +493,7 @@ class UpdateSuperConfigData(BaseModel):
     super_cash_in_fee_fraction: float | None = None
     super_cash_out_fee_fraction: float | None = None
     super_fee_wallet_id: str | None = None
+    max_cash_in_sats: int | None = None
 
     @validator(
         "super_cash_in_fee_fraction",
@@ -501,6 +506,14 @@ class UpdateSuperConfigData(BaseModel):
             raise ValueError("super fee fraction must be between 0 and 1")
         return round(float(v), 4)
 
+    @validator("max_cash_in_sats")
+    def _cap_non_negative(cls, v):
+        if v is None:
+            return v
+        if v < 0:
+            raise ValueError("max_cash_in_sats must be >= 0")
+        return int(v)
+
 
 # =============================================================================
 # Operator UX action carriers — partial-tx and balance-settlement features.

static/js/index.js

@@ -103,7 +103,8 @@ window.app = Vue.createApp({
         data: {
           super_cash_in_fee_fraction: 0,
           super_cash_out_fee_fraction: 0,
-          super_fee_wallet_id: ''
+          super_fee_wallet_id: '',
+          max_cash_in_sats: null
         }
       },
 
@@ -576,7 +577,8 @@ window.app = Vue.createApp({
           this.superConfig?.super_cash_in_fee_fraction ?? 0,
         super_cash_out_fee_fraction:
           this.superConfig?.super_cash_out_fee_fraction ?? 0,
-        super_fee_wallet_id: this.superConfig?.super_fee_wallet_id || ''
+        super_fee_wallet_id: this.superConfig?.super_fee_wallet_id || '',
+        max_cash_in_sats: this.superConfig?.max_cash_in_sats ?? null
       }
       this.superFeeDialog.show = true
     },
@@ -604,6 +606,21 @@ window.app = Vue.createApp({
         Number(d.super_cash_in_fee_fraction),
         Number(d.super_cash_out_fee_fraction)
       )) return
+      // Blank cap field -> null (the PUT skips null, so the existing value is
+      // preserved rather than cleared — set 0 to reject every cash-in).
+      const cap =
+        d.max_cash_in_sats === '' ||
+        d.max_cash_in_sats === null ||
+        d.max_cash_in_sats === undefined
+          ? null
+          : Number(d.max_cash_in_sats)
+      if (cap !== null && (!Number.isInteger(cap) || cap < 0)) {
+        Quasar.Notify.create({
+          type: 'negative',
+          message: 'Max cash-in must be a non-negative whole number of sats'
+        })
+        return
+      }
       this.superFeeDialog.saving = true
       try {
         const {data} = await LNbits.api.request(
@@ -611,7 +628,8 @@ window.app = Vue.createApp({
           {
             super_cash_in_fee_fraction: Number(d.super_cash_in_fee_fraction),
             super_cash_out_fee_fraction: Number(d.super_cash_out_fee_fraction),
-            super_fee_wallet_id: (d.super_fee_wallet_id || '').trim() || null
+            super_fee_wallet_id: (d.super_fee_wallet_id || '').trim() || null,
+            max_cash_in_sats: cap
           }
         )
         this.superConfig = data

templates/spirekeeper/index.html

@@ -1381,6 +1381,11 @@
             label="Super fee destination wallet_id"
             hint="LNbits wallet that collects the platform fee"
             class="q-mb-md" dense outlined></q-input>
+          <q-input v-model.number="superFeeDialog.data.max_cash_in_sats"
+            label="Max cash-in per transaction (sats — blank = no cap)"
+            hint="Server-side ceiling on a single cash-in's principal. The ATM attests the amount; this bounds a compromised/buggy machine to one capped tx."
+            type="number" step="1" min="0"
+            class="q-mb-md" dense outlined></q-input>
         </q-card-section>
         <q-card-actions align="right">
           <q-btn flat label="Cancel" v-close-popup></q-btn>