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feat(lnurlverify): send the payer's IP on a checkout's rail and token requests - #160
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… requests Every LNURL callback the plugin made came from this server's IP, so an LNURL service's per-IP limits (lnurl-server: 30 a minute on its destination and offline-swap callbacks) throttled a busy store on every rail. A checkout's rail activation and token quote now send X-Forwarded-For: the IP BTCPay resolved for the checkout request (HttpContext.Connection.RemoteIpAddress), as one value, and nothing for a missing, unspecified or loopback IP. An IPv4-mapped address is mapped to IPv4 first, so ::ffff:0.0.0.0 counts as unspecified and a payer is sent as a plain IPv4 address. Core's InvoiceActivator stands between the checkout controller and the payment handlers and passes nothing through, so the controller sets an AsyncLocal that the rail and token handlers read when they create their per-activation client. Nothing else reads it: Lightning invoice requests, the connection's lookup and save probe, and verify/verifyBatch polling never send the header. The recorder's re-issue after a partial payment runs on its own event loop and carries none. Not covered: a rail that core's own checkout page activates because a store or invoice makes it the default payment method (UIInvoiceController.GetCheckoutModel). Reaching it would need a filter on core's checkout actions. Tests: a rail activation through RailActivationGate and a token quote through TokenActivations carry exactly the payer's IP (IPv4, IPv6, IPv4-mapped); missing, unspecified and loopback IPs send nothing; the setup lookup with the save probe, and the poller, send nothing while a payer IP is ambient, and both fail when the connection handler or the poller forwards it. 368 -> 381. Docs: what is sent and when; that the lnurl-server operator must list this server in TRUSTED_FORWARDERS; that BTCPay takes X-Forwarded-For from any sender, so a listed server needs a proxy that sets it; the privacy cost; a live check.
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📝 WalkthroughWalkthroughCheckout rail and token requests now forward eligible payer IP addresses in ChangesPayer IP forwarding
Priority: ⬇️ Low Estimated code review effort: 3 (Moderate) | ~20 minutes Change: Feature Sequence Diagram(s)sequenceDiagram
participant CheckoutController as LnurlRailCheckoutController
participant PayerIp
participant RailHandler as LnurlRailPaymentHandler
participant HttpClient
participant LNURLService
CheckoutController->>PayerIp: Set Current from request RemoteIpAddress
CheckoutController->>RailHandler: Process checkout activation
RailHandler->>PayerIp: Forward(http)
PayerIp->>HttpClient: Add X-Forwarded-For for eligible address
RailHandler->>LNURLService: Send LNURL request
Merge Risk: 🟡 Moderate · up to Confirm that a trusted proxy controls the payer IP before merging; otherwise payers may evade IP-based limits at a trusting LNURL service. 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
Full details: Docstring CoverageExplanation Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 19 functions across 9 files. (2 skipped: 2 unsupported.)
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🧪 Generate unit tests (beta)
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@Plugins/BTCPayServer.Plugins.LNURLVerify/LnurlRailCheckoutController.cs:
- Line 45: Update both checkout actions that assign PayerIp.Current to use the
payer IP only when it comes from a trusted proxy that replaces incoming
forwarding headers and prevents direct access; otherwise use the socket peer
address, so untrusted forwarded values are never sent to the LNURL handlers.
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📒 Files selected for processing (11)
BTCPayServer.Plugins.LNURLVerify.Tests/ConnectionStringBuildTests.csBTCPayServer.Plugins.LNURLVerify.Tests/FakeHttp.csBTCPayServer.Plugins.LNURLVerify.Tests/LNURLVerifyPollerTests.csBTCPayServer.Plugins.LNURLVerify.Tests/LnurlRailPaymentHandlerTests.csBTCPayServer.Plugins.LNURLVerify.Tests/LnurlTokenPaymentHandlerTests.csPlugins/BTCPayServer.Plugins.LNURLVerify/CheckoutRails.csPlugins/BTCPayServer.Plugins.LNURLVerify/LnurlRailCheckoutController.csPlugins/BTCPayServer.Plugins.LNURLVerify/LnurlRailPaymentHandler.csPlugins/BTCPayServer.Plugins.LNURLVerify/LnurlTokenPaymentHandler.csPlugins/BTCPayServer.Plugins.LNURLVerify/README.mdPlugins/BTCPayServer.Plugins.LNURLVerify/VERIFICATION.md
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BTCPay applies X-Forwarded-For from any sender (Startup.cs clears KnownProxies). A payer who reaches BTCPay without a sanitising proxy in front could therefore choose the IP the checkout forwarded, and so dodge an LNURL service's per-payer limits. CodeRabbit raised this on #160. PayerIp.Resolve now reads X-Original-For, which ForwardedHeadersMiddleware overwrites with the TCP peer it replaced: - no header: nothing was forwarded, so RemoteIpAddress is the peer itself; - a loopback or private peer (a local proxy such as Docker nginx): its X-Forwarded-For is believed; - a public or unreadable peer: nothing is sent, and the payer shares the store's own limit as before. Forward also skips private addresses, which name no one to an outside service. The tests run BTCPay's own ForwardedHeadersMiddleware setup, including a forged X-Original-For with and without X-Forwarded-For. 381 -> 401.
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…taps a network (#159) * test(lnurlverify): pin that a stock install offers FixedFloat's USDT and USDC rails lnurl-server's FixedFloat rails advertise USDT and USDC under the plain coin tickers precisely so that LNURLVERIFY_ASSETS' default ("USDT,USDC") offers them with no configuration. This checks it against the server's canned payRequest instead of assuming it. * test(lnurlverify): pin that every FixedFloat chain is named and links its deposits The fixture is lnurl-server's FF_ASSETS chain list. A chain added there first fails here rather than reaching a payer as a raw CAIP-2 id. It also checks the explorer link for a chain-native deposit transaction id, which the server reports as the paymentReference. * feat(lnurlverify): name the provider a token network pays through A payment option may name a provider, the third party that holds its deposit address (lnurl-server's FixedFloat rails send "provider": "FixedFloat"). It is carried from the option through TokenOption to the network's prompt state and the checkout model. The network chip and the amount line then read "Arbitrum One via FixedFloat". An option that names none shows no attribution. The provider is a short display string from the LNURL, so it gets the bound the plugin already applies to unit names (1-64 characters); anything else is ignored. * feat(lnurlverify): refuse a token answer that needs a destination tag lnurl-server's callback answer can carry paymentDestinationTag, the memo a memo-bearing currency's deposit needs. Neither the checkout nor any of its payment URIs can attach one, so a payer would send funds the provider cannot credit. The network is refused instead, and the invoice log names the tag and the option. This is the one change to LnurlTokenRequester in this series, ruled in by the coordinator: it is an additive refusal and leaves every other answer as it was. The server's default allowlist advertises no memo-bearing currency, so the guard is dormant today. * test(lnurlverify): pin that a USDTTRC quote renders without a payment URI FixedFloat's USDT on Tron has no URI builder (TokenNamespaces returns null for tron), so the checkout must show the deposit address and the amount with no deeplink rather than fail. Checked on the mainnet asset lnurl-server advertises. * feat(lnurlverify): tell the payer whose deposit address a provider's network uses On a network whose option names a provider, the checkout states next to the QR three things the payer must know before sending: - the deposit address belongs to that third party, not the merchant; - the quote expires; - a late, short or excess deposit is resolved with the provider, not with the merchant or BTCPay. On lnurl-server's FixedFloat rails, neither BTCPay nor the LNURL service can refund such a deposit. The README and the verification runbook say the same, and the runbook's unit count is updated to 363. * test(lnurlverify): settle a FixedFloat-shaped USDT quote end to end in the checkout The stub LNURL gains a second address answering as lnurl-server's FixedFloat rails do: - options name provider "FixedFloat" on mainnet chain ids; - each callback is a new order with its own deposit address and verify id; - a quote carries only paymentQuote.expiresAt, with no top-level expiresAt; - verify and verifyBatch answer in the destination shape, with the payer's deposit transaction as paymentReference. The browser test checks four things on a stock install: - it provisions USDT and USDC; - the chips, amount and notice name FixedFloat; - the countdown runs out and the re-quote lands at a new deposit address; - the invoice settles through verifyBatch alone, with the deposit transaction linked on Arbiscan. It runs against the in-process stub, not lnurl-server's simulated provider, which needs the Arkade regtest stack. * test(lnurlverify): stop the FixedFloat checkout test depending on load The test assumed the first Arbitrum quote on screen was the stub's order 1, with a 20 s lifetime. On a loaded machine it showed order 2. Reproduced by slowing each FixedFloat callback by 2 s and logging the stub's orders: - opening the tab quotes every network, which made order 1; - the test's tap landed while the page still held Arbitrum as unrequested, so the tap asked for it again; - an explicit network is re-quoted even when it already holds a live quote, so that request made order 2. The page's busy flag cannot reveal the tap's request either, because the open-time request's finally clears it. A first fix that waited on it failed under the same slowdown. The test now: - waits until the page's own model has no unrequested network before tapping, so a tap sends no request; - reads which order the QR shows from the stub, checks no newer one exists, and expects the re-quote to be exactly the next order; - keeps Arbitrum quotes at 60 s only until it has watched one expire, so the re-quote lasts ten minutes. Every assertion keeps its intent: the provider label, the notice, the short countdown, the re-quote, settling on the deposit transaction through verifyBatch alone, and the Arbiscan link. * fix(lnurlverify): quote a token network only when the payer taps it A token quote can be a real order with a third party plus a solver swap. On lnurl-server's FixedFloat rails, opening the USDC tab used to place seven FixedFloat orders at once. "Request every rail when the checkout opens" is on by default, and the tab asked for every network. That is more than FixedFloat's whole per-minute budget of five orders. Now: - a token network is requested only when the payer taps it. The setting governs the Bitcoin rails alone, and the checkout no longer sends an activation when the tab opens; - a tap on a network that already holds a live quote for the amount due asks for nothing. Before, a tap the page had not yet caught up with placed a second order; - "live" is the same state the checkout shows, now kept on TokenNetworkState, so the guard can never refuse a network the checkout offers a new quote for. The cost is one round trip before the first QR. The FixedFloat browser test now taps and waits for the QR. It asserts that the untapped Tron network has no order and the tapped one exactly one, and keeps every earlier assertion. * fix(lnurlverify): refuse a destination tag of any JSON type The guard read paymentDestinationTag as a string only, so a numeric tag (an XRP destination tag is an integer) slipped through: the payer would be shown an address with no way to attach the memo the provider needs to credit the deposit. Any value that is present and not JSON null now refuses the network, and the log line names the tag's string form. A JSON null tag is no tag. Found by CodeRabbit on #159. * fix(lnurlverify): ask again when the payer taps a network with no live quote Under quote-on-tap a tap is the payer's request. Yet a tap on a network whose quote had expired, failed or was for an old amount only selected it, leaving the payer to find the refresh button. A tap now asks the LNURL for any network that is not live. A tap on a live quote still asks for nothing, and the server still refuses to re-quote a live one. "Live" is one definition in the component, client time included, so a chip whose countdown has run out counts as expired before the page refetches. The FixedFloat browser test now re-quotes the expired network by tapping it. It also asserts that opening the tab placed no order on either network before the first tap, and none for Tron after the Arbitrum re-quote. Found by CodeRabbit on #159. * feat(lnurlverify): send the payer's IP on a checkout's rail and token requests (#160) * feat(lnurlverify): send the payer's IP on a checkout's rail and token requests Every LNURL callback the plugin made came from this server's IP, so an LNURL service's per-IP limits (lnurl-server: 30 a minute on its destination and offline-swap callbacks) throttled a busy store on every rail. A checkout's rail activation and token quote now send X-Forwarded-For: the IP BTCPay resolved for the checkout request (HttpContext.Connection.RemoteIpAddress), as one value, and nothing for a missing, unspecified or loopback IP. An IPv4-mapped address is mapped to IPv4 first, so ::ffff:0.0.0.0 counts as unspecified and a payer is sent as a plain IPv4 address. Core's InvoiceActivator stands between the checkout controller and the payment handlers and passes nothing through, so the controller sets an AsyncLocal that the rail and token handlers read when they create their per-activation client. Nothing else reads it: Lightning invoice requests, the connection's lookup and save probe, and verify/verifyBatch polling never send the header. The recorder's re-issue after a partial payment runs on its own event loop and carries none. Not covered: a rail that core's own checkout page activates because a store or invoice makes it the default payment method (UIInvoiceController.GetCheckoutModel). Reaching it would need a filter on core's checkout actions. Tests: a rail activation through RailActivationGate and a token quote through TokenActivations carry exactly the payer's IP (IPv4, IPv6, IPv4-mapped); missing, unspecified and loopback IPs send nothing; the setup lookup with the save probe, and the poller, send nothing while a payer IP is ambient, and both fail when the connection handler or the poller forwards it. 368 -> 381. Docs: what is sent and when; that the lnurl-server operator must list this server in TRUSTED_FORWARDERS; that BTCPay takes X-Forwarded-For from any sender, so a listed server needs a proxy that sets it; the privacy cost; a live check. * fix(lnurlverify): forward a payer IP only when BTCPay can vouch for it BTCPay applies X-Forwarded-For from any sender (Startup.cs clears KnownProxies). A payer who reaches BTCPay without a sanitising proxy in front could therefore choose the IP the checkout forwarded, and so dodge an LNURL service's per-payer limits. CodeRabbit raised this on #160. PayerIp.Resolve now reads X-Original-For, which ForwardedHeadersMiddleware overwrites with the TCP peer it replaced: - no header: nothing was forwarded, so RemoteIpAddress is the peer itself; - a loopback or private peer (a local proxy such as Docker nginx): its X-Forwarded-For is believed; - a public or unreadable peer: nothing is sent, and the payer shares the store's own limit as before. Forward also skips private addresses, which name no one to an outside service. The tests run BTCPay's own ForwardedHeadersMiddleware setup, including a forged X-Original-For with and without X-Forwarded-For. 381 -> 401.
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Oct 8, 2026
Brings in #159 (FixedFloat rails) and #160 (payer IP). - StubLnurl: both sides' members are kept. The callback counter runs before the FixedFloat branch, so token orders count as callbacks too. - TokenCheckoutBrowserTests: keeps this branch's static Start(test) and #159's Invoice(tester, payUrl, assets...); #159's FixedFloat test now calls Start(this). - ConnectionStringBuildTests: #160's save-probe test answered with a placeholder mainnet "lnbc1". This branch's Save now decodes the invoice and refuses a network mismatch, so the fixture answers with a real regtest invoice instead. - VERIFICATION: the descriptions of both sides are kept, and the count is 415, the suite after the merge.
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Stacked on #159.
Every LNURL callback the plugin makes comes from this server's IP. An LNURL service that limits requests per IP therefore limits the whole store as one client. lnurl-server allows 30 a minute on its destination and offline-swap callbacks, so a busy store was throttled on every rail.
What changes. When a checkout activates a rail or asks for a token quote, those LNURL requests now carry the payer's IP in
X-Forwarded-For. It is the address BTCPay resolved for the checkout request (HttpContext.Connection.RemoteIpAddress), sent as a single value. A missing, unspecified, loopback or private address is not sent, and an IPv4-mapped address goes out as plain IPv4.How it gets there. Core's
InvoiceActivatorsits between the checkout controller and the payment handlers and passes nothing through. So the two checkout actions set a request-scopedAsyncLocal(PayerIp), and the rail and token handlers read it when they create their per-activationHttpClient. Nothing else reads it.verify/verifyBatchpolling.For it to matter, the LNURL service has to believe this server. On lnurl-server that is the new
TRUSTED_FORWARDERSsetting in ArkLabsHQ/lnurl-server#69.BTCPay applies
X-Forwarded-Forfrom any sender (Startup.cs:327-330clears the known proxies), so the plugin only forwards an IP it can vouch for. It readsX-Original-For, which the middleware overwrites with the TCP peer it replaced. With no header, nothing was forwarded and the peer is the payer. A loopback or private peer, meaning a local proxy such as Docker nginx, has itsX-Forwarded-Forbelieved. A public or unreadable peer gets nothing sent, and the payer shares the store's own limit, as before this PR. A payer therefore can't choose the IP they are limited as. CodeRabbit raised this, and45defaffixes it.Privacy. The payer's IP reaches the LNURL service, as it would if the payer's own wallet had contacted it directly. If you'd rather this be a per-store opt-in, it's a small change.
Not covered. A rail that core's own checkout page activates, because the store or invoice makes it the default payment method (
UIInvoiceController.GetCheckoutModel), sends no header. Reaching it would need a filter on core's checkout actions.Tests. The unit project goes from 368 to 401.
ForwardedHeadersMiddlewaresetup. They cover a direct connection, local proxies (loopback, Docker, ULA, link-local, IPv4-mapped), public peers, and a forgedX-Original-Forwith and withoutX-Forwarded-For.RailActivationGateand a token quote throughTokenActivationscarry exactly the payer's IP, for IPv4, IPv6 and IPv4-mapped addresses.Summary by CodeRabbit
X-Forwarded-Forwhen it is available and valid.