Implement parsing & resolving lnurls #2

benthecarman · 2025-04-25T00:35:53Z

No description provided.

TheBlueMatt

Ugh, found some comments I had still pending :(

TheBlueMatt · 2025-05-01T00:42:14Z

src/lib.rs

@@ -944,6 +947,38 @@ impl PaymentInstructions {
 					))
 				},
 			}
+		} else if let Some((_, data)) =


Isn't this supposed to support decoding any part of the string that contains lnurl* rather than only if the full string is lnurl*? I saw a checkout not long ago that used a QR code to display, eg https://a.website/to-visit?lnurl=lnurlasdfwerqwer so that users who just scan the QR code go to their website but if a wallet scans it it will resolve the lnurl.

just learned thats a thing, will add

https://github.com/lnurl/luds/blob/luds/01.md#fallback-scheme

TheBlueMatt · 2025-05-01T00:43:21Z

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


An Lnurl isn't a well-defined thing, I believe? This needs to specify what, exactly, the url parameter is (a URL for an LNURL endpoint, and not the encoded LNURL...... strings).

An lnurl is just a bech32 encoded url https://github.com/lnurl/luds/blob/luds/01.md

Everything works off of calling the first first URL as a GET request and then seeing which kind it is and handling it from there. This function is that first GET request

TheBlueMatt · 2025-05-01T00:44:03Z

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>;


Should we rename the trait now that its resolving more than HRNs? I think I'm fine with no, because we really want this to be about HRNs, we just happen to support LNURL too, but still.

Yeah I figured it was simpler to keep the name. At this point basically every lnurl-pay is a lightning address, for most cases this is just splitting out the 2 lnurl calls into separate functions instead of a single one

benthecarman · 2025-05-20T20:17:17Z

Added support for the fallback lnurl stuff and added tests for the lnurl parsing

TheBlueMatt · 2025-06-28T21:25:41Z

src/dns_resolver.rs

-		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);


This still gets called, it just returns a failure. and that's fine, we shouldn't panic :)

ah was just keeping what it was before

The error message is wrong, too, though. The previous resolve_lnurl/now resolve_lnurl_to_invoice method is not called by the code in lib.rs (and shouldn't be, per the API), but this code is called. Instead, the error message should be around not supporting LNURL, and resolve_lnurl_to_invoice should presumably retain its debug_assert.

ah i see now, good call out

TheBlueMatt · 2025-06-28T21:29:17Z

src/lib.rs

@@ -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) {


Does it need to be from lnurl to the end of the string, or can it be a substring?

Made it so it'll handle relevant sub strings

TheBlueMatt · 2025-06-30T22:35:15Z

src/lib.rs

+			// first try to decode as a bech32-encoded lnurl, if that fails, try to drop a
+			// trailing `&` and decode again, this could a http query param
+			let decode = bitcoin::bech32::decode(lnurl_str).or_else(|e| {
+				if let Some(idx) = lnurl_str.find('&') {


I believe we'll also want to split by #. Might as well just do this always rather than trying to decode twice?

Added, when would # be used though?

URLs can be https://example.com?lightning=LNURL#section, which jumps to the HTML object section on load.

TheBlueMatt

Gonna go ahead and land this but will swap the lowercase call in a followup.

TheBlueMatt · 2025-07-02T16:25:52Z

src/lib.rs

+		} else if let Some(idx) = instructions.to_lowercase().rfind("lnurl") {
+			let mut lnurl_str = &instructions[idx..];


This assumes that unicode lowercasing will always keep the char the same length. I assume that's probably true in practice, but its a weird assumption to take. Instead, using to_ascii_lowercase only assumes that for ASCII chars (which is trivially true).

benthecarman force-pushed the lnurl branch 2 times, most recently from 3acd077 to a8644fe Compare April 26, 2025 21:19

TheBlueMatt reviewed May 14, 2025

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benthecarman force-pushed the lnurl branch from a8644fe to 965ec75 Compare May 20, 2025 20:16

benthecarman force-pushed the lnurl branch from 965ec75 to 097f645 Compare May 20, 2025 20:21

TheBlueMatt reviewed Jun 28, 2025

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TheBlueMatt force-pushed the main branch from dfa2b00 to 64a45f2 Compare June 29, 2025 01:48

benthecarman force-pushed the lnurl branch 2 times, most recently from 282f844 to 0562fac Compare June 30, 2025 01:07

TheBlueMatt reviewed Jun 30, 2025

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benthecarman force-pushed the lnurl branch from 0562fac to b3caf01 Compare June 30, 2025 23:51

Implement parsing & resolving lnurls

09e000f

benthecarman force-pushed the lnurl branch from b3caf01 to 09e000f Compare July 1, 2025 01:30

TheBlueMatt approved these changes Jul 2, 2025

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TheBlueMatt merged commit d6ef87c into rust-bitcoin:main Jul 2, 2025
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benthecarman deleted the lnurl branch July 2, 2025 16:28

		} else if let Some(idx) = instructions.to_lowercase().rfind("lnurl") {
		let mut lnurl_str = &instructions[idx..];

Implement parsing & resolving lnurls #2

Implement parsing & resolving lnurls #2

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benthecarman commented Apr 25, 2025

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benthecarman commented May 20, 2025

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