diff options
Diffstat (limited to 'meltguard.ts')
| -rw-r--r-- | meltguard.ts | 110 |
1 files changed, 110 insertions, 0 deletions
diff --git a/meltguard.ts b/meltguard.ts new file mode 100644 index 00000000..c7195bb0 --- /dev/null +++ b/meltguard.ts @@ -0,0 +1,110 @@ +// meltguard — out-of-band spend limiter for the panic-mode mint. +// +// Sits INLINE between the mint and cl's CLNRest: the mint is pointed at +// MINT_CLNREST_URL=http://meltguard:3011 instead of http://cl:3010. Every melt +// is a POST /v1/pay or /v1/xpay; the guard decodes the invoice amount (via cl's own /v1/decode, +// so no hand-rolled bolt11 parsing) and enforces two caps the mint cannot bypass — +// even if panic mode has a bug or the mint is compromised, it physically cannot +// move money except through this guard: +// +// 1. PER-MELT CAP — reject any single pay over MELT_MAX_SAT (default 1,000,000). +// 2. CUMULATIVE FREEZE — track total successfully paid; once it would exceed +// MELT_CUM_MAX_SAT (default 3,000,000), write a STICKY freeze flag and reject +// ALL further pays until an operator reviews and clears it. +// +// State lives in plain files OUTSIDE any db (like the nobal failsafe), so a db +// compromise can't move them and a restart can't forget them. +// +// Everything that is not POST /v1/pay|/v1/xpay is proxied through untouched, so mint +// startup (getinfo, listinvoices, waitanyinvoice, invoice, listpays…) works normally. +// +// Env: CL_URL (http://cl:3010), MELT_MAX_SAT, MELT_CUM_MAX_SAT, GUARD_DIR (/guard), +// PORT (3011). Run: GUARD_DIR=./guard bun meltguard.ts +import { readFileSync, writeFileSync, existsSync, appendFileSync, mkdirSync } from "fs"; + +const CL = process.env.CL_URL || "http://cl:3010"; +const PER = Number(process.env.MELT_MAX_SAT || 1_000_000); +const CUM = Number(process.env.MELT_CUM_MAX_SAT || 3_000_000); +const DIR = process.env.GUARD_DIR || "/guard"; +const PORT = Number(process.env.PORT || 3011); +mkdirSync(DIR, { recursive: true }); +const CUM_FILE = `${DIR}/cumulative_sat`; +const FROZEN_FILE = `${DIR}/FROZEN`; +const LOG = `${DIR}/meltguard.log`; + +const readCum = () => (existsSync(CUM_FILE) ? Number(readFileSync(CUM_FILE, "utf8").trim()) || 0 : 0); +const writeCum = (n: number) => writeFileSync(CUM_FILE, String(n)); +const isFrozen = () => existsSync(FROZEN_FILE); +const log = (m: string) => { try { appendFileSync(LOG, `${new Date().toISOString()} ${m}\n`); } catch {} console.error("meltguard:", m); }; +const freeze = (why: string) => { writeFileSync(FROZEN_FILE, why + "\n"); log(`FROZEN — ${why} — operator must review and clear ${FROZEN_FILE}`); }; +const err = (status: number, message: string) => new Response(JSON.stringify({ error: message }), { status, headers: { "content-type": "application/json" } }); + +async function decodeSat(bolt11: string, rune: string | null): Promise<number | null> { + try { + const r = await fetch(`${CL}/v1/decode`, { method: "POST", headers: { "content-type": "application/json", ...(rune ? { Rune: rune } : {}) }, body: JSON.stringify({ string: bolt11 }) }); + const j: any = await r.json(); + if (j.amount_msat != null) return Math.ceil(Number(j.amount_msat) / 1000); + return null; // amountless invoice — no embedded amount to cap on; treat as undecidable + } catch { return null; } +} + +console.log(`meltguard on :${PORT} -> ${CL} | per-melt<=${PER} sat, cumulative freeze at ${CUM} sat | state ${DIR} | frozen=${isFrozen()} cum=${readCum()}`); + +Bun.serve({ + port: PORT, hostname: "0.0.0.0", idleTimeout: 0, + async fetch(req) { + const url = new URL(req.url); + const rune = req.headers.get("Rune"); + // nutshell >= 0.20.3.1 CLNRestWallet pays via /v1/xpay (form field `invstring`, + // `maxfee`); older versions used /v1/pay (`bolt11`/`invoice`). Guard both, so a + // backend switch can never route a melt around the caps. + const isXpay = req.method === "POST" && url.pathname === "/v1/xpay"; + const isPay = isXpay || (req.method === "POST" && url.pathname === "/v1/pay"); + + if (isPay) { + if (isFrozen()) return err(403, "meltguard: FROZEN — operator review required"); + // nutshell's CoreLightningRestWallet (mint-old) posts /v1/pay FORM-encoded + // with the invoice under `invoice` (old c-lightning-REST dialect); the newer + // CLNRestWallet uses `bolt11`. Parse form first, fall back to JSON, and + // accept either field name. (Prior code did req.json()+body.bolt11 only, so + // it never parsed the mint's form body -> every old-ecash melt was rejected + // at the amount check.) + const raw = await req.text(); + let invoice = ""; + const extra: Record<string, string> = {}; + try { + const p = new URLSearchParams(raw); + if ([...p.keys()].length) { + invoice = p.get("invstring") || p.get("invoice") || p.get("bolt11") || ""; + for (const [k, v] of p) if (k !== "invoice" && k !== "bolt11" && k !== "invstring") extra[k] = v; + } + } catch {} + if (!invoice) { + try { + const j = JSON.parse(raw); + invoice = j.invstring || j.bolt11 || j.invoice || ""; + for (const k of Object.keys(j)) if (k !== "invoice" && k !== "bolt11" && k !== "invstring") extra[k] = String(j[k]); + } catch {} + } + const amt = await decodeSat(invoice, rune); + if (amt == null) return err(400, "meltguard: could not determine invoice amount — refusing to forward"); + if (amt > PER) { log(`REJECT per-melt ${amt} > ${PER}`); return err(403, `meltguard: per-melt cap ${PER} sat exceeded (${amt})`); } + const cum = readCum(); + if (cum + amt > CUM) { freeze(`cumulative ${cum}+${amt} > ${CUM}`); return err(403, `meltguard: cumulative cap ${CUM} sat — FROZEN, operator review required`); } + // forward to cl (official CLNREST) as FORM on the SAME endpoint the mint + // called (`invstring` for xpay, `bolt11` for pay), preserving the mint's + // other params (maxfee / maxfeepercent / exemptfee). Count cumulative only + // on cl-reported success. + const fwd = new URLSearchParams(isXpay ? { invstring: invoice, ...extra } : { bolt11: invoice, ...extra }); + const resp = await fetch(`${CL}${isXpay ? "/v1/xpay" : "/v1/pay"}`, { method: "POST", headers: { "content-type": "application/x-www-form-urlencoded", ...(rune ? { Rune: rune } : {}) }, body: fwd.toString() }); + const text = await resp.text(); + if (resp.ok) { writeCum(cum + amt); log(`PAID ${amt} sat via ${isXpay ? "xpay" : "pay"} (cumulative ${cum + amt}/${CUM})`); } + return new Response(text, { status: resp.status, headers: { "content-type": "application/json" } }); + } + + // transparent proxy for all other CLNRest calls + const body = req.method === "GET" || req.method === "HEAD" ? undefined : await req.arrayBuffer(); + const resp = await fetch(`${CL}${url.pathname}${url.search}`, { method: req.method, headers: { ...(req.headers.get("content-type") ? { "content-type": req.headers.get("content-type")! } : {}), ...(rune ? { Rune: rune } : {}) }, body }); + return new Response(await resp.arrayBuffer(), { status: resp.status, headers: { "content-type": resp.headers.get("content-type") || "application/json" } }); + }, +}); |