Implement parsing & resolving lnurls

benthecarman · benthecarman · commit 097f645431f7 · 2025-05-20T15:21:39.000-05:00
diff --git a/fuzz/src/parse.rs b/fuzz/src/parse.rs
@@ -43,7 +43,16 @@ impl HrnResolver for Resolver<'_> {
 		})
 	}
 
-	fn resolve_lnurl<'a>(&'a self, _: String, _: Amount, _: [u8; 32]) -> LNURLResolutionFuture<'a> {
+	fn resolve_lnurl<'a>(&'a self, _: &'a str) -> HrnResolutionFuture<'a> {
+		Box::pin(async {
+			let mut us = self.0.lock().unwrap();
+			us.0.take().unwrap()
+		})
+	}
+
+	fn resolve_lnurl_to_invoice<'a>(
+		&'a self, _: String, _: Amount, _: [u8; 32],
+	) -> LNURLResolutionFuture<'a> {
 		Box::pin(async {
 			let mut us = self.0.lock().unwrap();
 			if let Ok(s) = std::str::from_utf8(us.1.take().unwrap()) {
diff --git a/src/dns_resolver.rs b/src/dns_resolver.rs
@@ -39,8 +39,16 @@ impl HrnResolver for DNSHrnResolver {
 		Box::pin(async move { self.resolve_dns(hrn).await })
 	}
 
-	fn resolve_lnurl<'a>(&'a self, _: String, _: Amount, _: [u8; 32]) -> LNURLResolutionFuture<'a> {
-		let err = "resolve_lnurl shouldn't be called when we don't reoslve LNURL";
+	fn resolve_lnurl<'a>(&'a self, _url: &'a str) -> HrnResolutionFuture<'a> {
+		let err = "resolve_lnurl shouldn't be called when we don't resolve LNURL";
+		debug_assert!(false, "{}", err);
+		Box::pin(async move { Err(err) })
+	}
+
+	fn resolve_lnurl_to_invoice<'a>(
+		&'a self, _: String, _: Amount, _: [u8; 32],
+	) -> LNURLResolutionFuture<'a> {
+		let err = "resolve_lnurl shouldn't be called when we don't resolve LNURL";
 		debug_assert!(false, "{}", err);
 		Box::pin(async move { Err(err) })
 	}
diff --git a/src/hrn_resolution.rs b/src/hrn_resolution.rs
@@ -111,10 +111,14 @@ pub trait HrnResolver {
 	/// can be further parsed as payment instructions.
 	fn resolve_hrn<'a>(&'a self, hrn: &'a HumanReadableName) -> HrnResolutionFuture<'a>;
 
+	/// Resolves the given Lnurl into a [`HrnResolution`] containing a result which
+	/// can be further parsed as payment instructions.
+	fn resolve_lnurl<'a>(&'a self, url: &'a str) -> HrnResolutionFuture<'a>;
+
 	/// Resolves the LNURL callback (from a [`HrnResolution::LNURLPay`]) into a [`Bolt11Invoice`].
 	///
 	/// This shall only be called if [`Self::resolve_hrn`] returns an [`HrnResolution::LNURLPay`].
-	fn resolve_lnurl<'a>(
+	fn resolve_lnurl_to_invoice<'a>(
 		&'a self, callback_url: String, amount: Amount, expected_description_hash: [u8; 32],
 	) -> LNURLResolutionFuture<'a>;
 }
@@ -128,7 +132,13 @@ impl HrnResolver for DummyHrnResolver {
 		Box::pin(async { Err("Human Readable Name resolution not supported") })
 	}
 
-	fn resolve_lnurl<'a>(&'a self, _: String, _: Amount, _: [u8; 32]) -> LNURLResolutionFuture<'a> {
+	fn resolve_lnurl<'a>(&'a self, _lnurl: &'a str) -> HrnResolutionFuture<'a> {
+		Box::pin(async { Err("LNURL resolution not supported") })
+	}
+
+	fn resolve_lnurl_to_invoice<'a>(
+		&'a self, _: String, _: Amount, _: [u8; 32],
+	) -> LNURLResolutionFuture<'a> {
 		Box::pin(async { Err("LNURL resolution not supported") })
 	}
 }
diff --git a/src/http_resolver.rs b/src/http_resolver.rs
@@ -134,17 +134,16 @@ impl HTTPHrnResolver {
 		resolve_proof(&dns_name, proof)
 	}
 
-	async fn resolve_lnurl(&self, hrn: &HumanReadableName) -> Result<HrnResolution, &'static str> {
-		let init_url = format!("https://{}/.well-known/lnurlp/{}", hrn.domain(), hrn.user());
+	async fn resolve_lnurl_impl(&self, lnurl_url: &str) -> Result<HrnResolution, &'static str> {
 		let err = "Failed to fetch LN-Address initial well-known endpoint";
 		let init: LNURLInitResponse =
-			reqwest::get(init_url).await.map_err(|_| err)?.json().await.map_err(|_| err)?;
+			reqwest::get(lnurl_url).await.map_err(|_| err)?.json().await.map_err(|_| err)?;
 
 		if init.tag != "payRequest" {
-			return Err("LNURL initial init_responseponse had an incorrect tag value");
+			return Err("LNURL initial init_response had an incorrect tag value");
 		}
 		if init.min_sendable > init.max_sendable {
-			return Err("LNURL initial init_responseponse had no sendable amounts");
+			return Err("LNURL initial init_response had no sendable amounts");
 		}
 
 		let err = "LNURL metadata was not in the correct format";
@@ -176,14 +175,20 @@ impl HrnResolver for HTTPHrnResolver {
 				Err(e) if e == DNS_ERR => {
 					// If we got an error that might indicate the recipient doesn't support BIP
 					// 353, try LN-Address via LNURL
-					self.resolve_lnurl(hrn).await
+					let init_url =
+						format!("https://{}/.well-known/lnurlp/{}", hrn.domain(), hrn.user());
+					self.resolve_lnurl(&init_url).await
 				},
 				Err(e) => Err(e),
 			}
 		})
 	}
 
-	fn resolve_lnurl<'a>(
+	fn resolve_lnurl<'a>(&'a self, url: &'a str) -> HrnResolutionFuture<'a> {
+		Box::pin(async move { self.resolve_lnurl_impl(url).await })
+	}
+
+	fn resolve_lnurl_to_invoice<'a>(
 		&'a self, mut callback: String, amt: Amount, expected_description_hash: [u8; 32],
 	) -> LNURLResolutionFuture<'a> {
 		Box::pin(async move {
@@ -308,7 +313,8 @@ mod tests {
 		.unwrap();
 
 		let resolved = if let PaymentInstructions::ConfigurableAmount(instr) = instructions {
-			// min_amt and max_amt may or may not be set by the LNURL server
+			assert!(instr.min_amt().is_some());
+			assert!(instr.max_amt().is_some());
 
 			assert_eq!(instr.pop_callback(), None);
 			assert!(instr.bip_353_dnssec_proof().is_none());
@@ -339,4 +345,42 @@ mod tests {
 			}
 		}
 	}
+
+	#[tokio::test]
+	async fn test_http_lnurl_resolver() {
+		let instructions = PaymentInstructions::parse(
+			// lnurl encoding for lnurltest@bitcoin.ninja
+			"lnurl1dp68gurn8ghj7cnfw33k76tw9ehxjmn2vyhjuam9d3kz66mwdamkutmvde6hymrs9akxuatjd36x2um5ahcq39",
+			Network::Bitcoin,
+			&HTTPHrnResolver,
+			true,
+		)
+		.await
+		.unwrap();
+
+		let resolved = if let PaymentInstructions::ConfigurableAmount(instr) = instructions {
+			assert!(instr.min_amt().is_some());
+			assert!(instr.max_amt().is_some());
+
+			assert_eq!(instr.pop_callback(), None);
+			assert!(instr.bip_353_dnssec_proof().is_none());
+
+			instr.set_amount(Amount::from_sats(100_000).unwrap(), &HTTPHrnResolver).await.unwrap()
+		} else {
+			panic!();
+		};
+
+		assert_eq!(resolved.pop_callback(), None);
+		assert!(resolved.bip_353_dnssec_proof().is_none());
+
+		for method in resolved.methods() {
+			match method {
+				PaymentMethod::LightningBolt11(invoice) => {
+					assert_eq!(invoice.amount_milli_satoshis(), Some(100_000_000));
+				},
+				PaymentMethod::LightningBolt12(_) => panic!("Should only resolve to BOLT 11"),
+				PaymentMethod::OnChain(_) => panic!("Should only resolve to BOLT 11"),
+			}
+		}
+	}
 }
diff --git a/src/lib.rs b/src/lib.rs
@@ -347,7 +347,8 @@ impl ConfigurableAmountPaymentInstructions {
 			debug_assert!(inner.onchain_amt.is_none());
 			debug_assert!(inner.pop_callback.is_none());
 			debug_assert!(inner.hrn_proof.is_none());
-			let bolt11 = resolver.resolve_lnurl(callback, amount, expected_desc_hash).await?;
+			let bolt11 =
+				resolver.resolve_lnurl_to_invoice(callback, amount, expected_desc_hash).await?;
 			if bolt11.amount_milli_satoshis() != Some(amount.milli_sats()) {
 				return Err("LNURL resolution resulted in a BOLT 11 invoice with the wrong amount");
 			}
@@ -428,6 +429,8 @@ pub enum ParseError {
 	InvalidBolt12(Bolt12ParseError),
 	/// An invalid on-chain address was encountered
 	InvalidOnChain(address::ParseError),
+	/// An invalid lnurl was encountered
+	InvalidLnurl(&'static str),
 	/// The payment instructions encoded instructions for a network other than the one specified.
 	WrongNetwork,
 	/// Different parts of the payment instructions were inconsistent.
@@ -944,6 +947,47 @@ impl PaymentInstructions {
 					))
 				},
 			}
+		} else if let Some(idx) = instructions.to_lowercase().rfind("lnurl") {
+			let lnurl_str = &instructions[idx..];
+			if let Ok((_, data)) = bitcoin::bech32::decode(lnurl_str) {
+				let url = String::from_utf8(data)
+					.map_err(|_| ParseError::InvalidLnurl("Not utf-8 encoded string"))?;
+				let resolution = hrn_resolver.resolve_lnurl(&url).await;
+				let resolution = resolution.map_err(ParseError::HrnResolutionError)?;
+				match resolution {
+					HrnResolution::DNSSEC { .. } => Err(ParseError::HrnResolutionError(
+						"Unexpected return when resolving lnurl",
+					)),
+					HrnResolution::LNURLPay {
+						min_value,
+						max_value,
+						expected_description_hash,
+						recipient_description,
+						callback,
+					} => {
+						let inner = PaymentInstructionsImpl {
+							description: recipient_description,
+							methods: Vec::new(),
+							lnurl: Some((
+								callback,
+								expected_description_hash,
+								min_value,
+								max_value,
+							)),
+							onchain_amt: None,
+							ln_amt: None,
+							pop_callback: None,
+							hrn: None,
+							hrn_proof: None,
+						};
+						Ok(PaymentInstructions::ConfigurableAmount(
+							ConfigurableAmountPaymentInstructions { inner },
+						))
+					},
+				}
+			} else {
+				parse_resolved_instructions(instructions, network, supports_pops, None, None)
+			}
 		} else {
 			parse_resolved_instructions(instructions, network, supports_pops, None, None)
 		}
@@ -966,6 +1010,13 @@ mod tests {
 	const SAMPLE_OFFER: &str = "lno1qgs0v8hw8d368q9yw7sx8tejk2aujlyll8cp7tzzyh5h8xyppqqqqqqgqvqcdgq2qenxzatrv46pvggrv64u366d5c0rr2xjc3fq6vw2hh6ce3f9p7z4v4ee0u7avfynjw9q";
 	const SAMPLE_BIP21: &str = "bitcoin:1andreas3batLhQa2FawWjeyjCqyBzypd?amount=50&label=Luke-Jr&message=Donation%20for%20project%20xyz";
 
+	#[cfg(feature = "http")]
+	const SAMPLE_LNURL: &str = "LNURL1DP68GURN8GHJ7MRWW4EXCTNDW46XJMNEDEJHGTNRDAKJ7TNHV4KXCTTTDEHHWM30D3H82UNVWQHHYETXW4HXG0AH8NK";
+	#[cfg(feature = "http")]
+	const SAMPLE_LNURL_LN_PREFIX: &str = "lightning:LNURL1DP68GURN8GHJ7MRWW4EXCTNDW46XJMNEDEJHGTNRDAKJ7TNHV4KXCTTTDEHHWM30D3H82UNVWQHHYETXW4HXG0AH8NK";
+	#[cfg(feature = "http")]
+	const SAMPLE_LNURL_FALLBACK: &str = "https://service.com/giftcard/redeem?id=123&lightning=LNURL1DP68GURN8GHJ7MRWW4EXCTNDW46XJMNEDEJHGTNRDAKJ7TNHV4KXCTTTDEHHWM30D3H82UNVWQHHYETXW4HXG0AH8NK";
+
 	const SAMPLE_BIP21_WITH_INVOICE: &str = "bitcoin:BC1QYLH3U67J673H6Y6ALV70M0PL2YZ53TZHVXGG7U?amount=0.00001&label=sbddesign%3A%20For%20lunch%20Tuesday&message=For%20lunch%20Tuesday&lightning=LNBC10U1P3PJ257PP5YZTKWJCZ5FTL5LAXKAV23ZMZEKAW37ZK6KMV80PK4XAEV5QHTZ7QDPDWD3XGER9WD5KWM36YPRX7U3QD36KUCMGYP282ETNV3SHJCQZPGXQYZ5VQSP5USYC4LK9CHSFP53KVCNVQ456GANH60D89REYKDNGSMTJ6YW3NHVQ9QYYSSQJCEWM5CJWZ4A6RFJX77C490YCED6PEMK0UPKXHY89CMM7SCT66K8GNEANWYKZGDRWRFJE69H9U5U0W57RRCSYSAS7GADWMZXC8C6T0SPJAZUP6";
 	#[cfg(not(feature = "std"))]
 	const SAMPLE_BIP21_WITH_INVOICE_ADDR: &str = "bc1qylh3u67j673h6y6alv70m0pl2yz53tzhvxgg7u";
@@ -1277,4 +1328,33 @@ mod tests {
 			Err(ParseError::InstructionsExpired),
 		);
 	}
+
+	#[cfg(feature = "http")]
+	async fn test_lnurl(str: &str) {
+		let parsed = PaymentInstructions::parse(
+			str,
+			Network::Signet,
+			&http_resolver::HTTPHrnResolver,
+			false,
+		)
+		.await
+		.unwrap();
+
+		let parsed = match parsed {
+			PaymentInstructions::ConfigurableAmount(parsed) => parsed,
+			_ => panic!(),
+		};
+
+		assert_eq!(parsed.methods().count(), 1);
+		assert_eq!(parsed.min_amt(), Some(Amount::from_milli_sats(1000).unwrap()));
+		assert_eq!(parsed.max_amt(), Some(Amount::from_milli_sats(11000000000).unwrap()));
+	}
+
+	#[cfg(feature = "http")]
+	#[tokio::test]
+	async fn parse_lnurl() {
+		test_lnurl(SAMPLE_LNURL).await;
+		test_lnurl(SAMPLE_LNURL_LN_PREFIX).await;
+		test_lnurl(SAMPLE_LNURL_FALLBACK).await;
+	}
 }
