Expand invoice module docs and include an example
[rust-lightning] / lightning / src / offers / refund.rs
index 9448f8fffc66d3d51ae3b8e9e90c651dc3dc912c..48be9774aec2f7bc5e220db29935654119c3e9b0 100644 (file)
 //! Data structures and encoding for refunds.
 //!
 //! A [`Refund`] is an "offer for money" and is typically constructed by a merchant and presented
-//! directly to the customer. The recipient responds with an `Invoice` to be paid.
+//! directly to the customer. The recipient responds with an [`Invoice`] to be paid.
 //!
 //! This is an [`InvoiceRequest`] produced *not* in response to an [`Offer`].
 //!
+//! [`Invoice`]: crate::offers::invoice::Invoice
 //! [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
 //! [`Offer`]: crate::offers::offer::Offer
 //!
@@ -77,8 +78,10 @@ use core::convert::TryFrom;
 use core::str::FromStr;
 use core::time::Duration;
 use crate::io;
+use crate::ln::PaymentHash;
 use crate::ln::features::InvoiceRequestFeatures;
 use crate::ln::msgs::{DecodeError, MAX_VALUE_MSAT};
+use crate::offers::invoice::{BlindedPayInfo, InvoiceBuilder};
 use crate::offers::invoice_request::{InvoiceRequestTlvStream, InvoiceRequestTlvStreamRef};
 use crate::offers::offer::{OfferTlvStream, OfferTlvStreamRef};
 use crate::offers::parse::{Bech32Encode, ParseError, ParsedMessage, SemanticError};
@@ -102,8 +105,8 @@ pub struct RefundBuilder {
 }
 
 impl RefundBuilder {
-       /// Creates a new builder for a refund using the [`Refund::payer_id`] for signing invoices. Use
-       /// a different pubkey per refund to avoid correlating refunds.
+       /// Creates a new builder for a refund using the [`Refund::payer_id`] for the public node id to
+       /// send to if no [`Refund::paths`] are set. Otherwise, it may be a transient pubkey.
        ///
        /// Additionally, sets the required [`Refund::description`], [`Refund::metadata`], and
        /// [`Refund::amount_msats`].
@@ -183,22 +186,33 @@ impl RefundBuilder {
        }
 }
 
-/// A `Refund` is a request to send an `Invoice` without a preceding [`Offer`].
+#[cfg(test)]
+impl RefundBuilder {
+       fn features_unchecked(mut self, features: InvoiceRequestFeatures) -> Self {
+               self.refund.features = features;
+               self
+       }
+}
+
+/// A `Refund` is a request to send an [`Invoice`] without a preceding [`Offer`].
 ///
 /// Typically, after an invoice is paid, the recipient may publish a refund allowing the sender to
 /// recoup their funds. A refund may be used more generally as an "offer for money", such as with a
 /// bitcoin ATM.
 ///
+/// [`Invoice`]: crate::offers::invoice::Invoice
 /// [`Offer`]: crate::offers::offer::Offer
 #[derive(Clone, Debug)]
 pub struct Refund {
-       bytes: Vec<u8>,
-       contents: RefundContents,
+       pub(super) bytes: Vec<u8>,
+       pub(super) contents: RefundContents,
 }
 
-/// The contents of a [`Refund`], which may be shared with an `Invoice`.
+/// The contents of a [`Refund`], which may be shared with an [`Invoice`].
+///
+/// [`Invoice`]: crate::offers::invoice::Invoice
 #[derive(Clone, Debug)]
-struct RefundContents {
+pub(super) struct RefundContents {
        payer: PayerContents,
        // offer fields
        metadata: Option<Vec<u8>>,
@@ -231,13 +245,7 @@ impl Refund {
        /// Whether the refund has expired.
        #[cfg(feature = "std")]
        pub fn is_expired(&self) -> bool {
-               match self.absolute_expiry() {
-                       Some(seconds_from_epoch) => match SystemTime::UNIX_EPOCH.elapsed() {
-                               Ok(elapsed) => elapsed > seconds_from_epoch,
-                               Err(_) => false,
-                       },
-                       None => false,
-               }
+               self.contents.is_expired()
        }
 
        /// The issuer of the refund, possibly beginning with `user@domain` or `domain`. Intended to be
@@ -277,7 +285,10 @@ impl Refund {
                &self.contents.features
        }
 
-       /// A possibly transient pubkey used to sign the refund.
+       /// A public node id to send to in the case where there are no [`paths`]. Otherwise, a possibly
+       /// transient pubkey.
+       ///
+       /// [`paths`]: Self::paths
        pub fn payer_id(&self) -> PublicKey {
                self.contents.payer_id
        }
@@ -287,6 +298,44 @@ impl Refund {
                self.contents.payer_note.as_ref().map(|payer_note| PrintableString(payer_note.as_str()))
        }
 
+       /// Creates an [`Invoice`] for the refund with the given required fields.
+       ///
+       /// Unless [`InvoiceBuilder::relative_expiry`] is set, the invoice will expire two hours after
+       /// calling this method in `std` builds. For `no-std` builds, a final [`Duration`] parameter
+       /// must be given, which is used to set [`Invoice::created_at`] since [`std::time::SystemTime`]
+       /// is not available.
+       ///
+       /// The caller is expected to remember the preimage of `payment_hash` in order to
+       /// claim a payment for the invoice.
+       ///
+       /// The `signing_pubkey` is required to sign the invoice since refunds are not in response to an
+       /// offer, which does have a `signing_pubkey`.
+       ///
+       /// The `payment_paths` parameter is useful for maintaining the payment recipient's privacy. It
+       /// must contain one or more elements.
+       ///
+       /// Errors if the request contains unknown required features.
+       ///
+       /// [`Invoice`]: crate::offers::invoice::Invoice
+       /// [`Invoice::created_at`]: crate::offers::invoice::Invoice::created_at
+       pub fn respond_with(
+               &self, payment_paths: Vec<(BlindedPath, BlindedPayInfo)>, payment_hash: PaymentHash,
+               signing_pubkey: PublicKey,
+               #[cfg(not(feature = "std"))]
+               created_at: Duration
+       ) -> Result<InvoiceBuilder, SemanticError> {
+               if self.features().requires_unknown_bits() {
+                       return Err(SemanticError::UnknownRequiredFeatures);
+               }
+
+               #[cfg(feature = "std")]
+               let created_at = std::time::SystemTime::now()
+                       .duration_since(std::time::SystemTime::UNIX_EPOCH)
+                       .expect("SystemTime::now() should come after SystemTime::UNIX_EPOCH");
+
+               InvoiceBuilder::for_refund(self, payment_paths, created_at, payment_hash, signing_pubkey)
+       }
+
        #[cfg(test)]
        fn as_tlv_stream(&self) -> RefundTlvStreamRef {
                self.contents.as_tlv_stream()
@@ -300,7 +349,18 @@ impl AsRef<[u8]> for Refund {
 }
 
 impl RefundContents {
-       fn chain(&self) -> ChainHash {
+       #[cfg(feature = "std")]
+       pub(super) fn is_expired(&self) -> bool {
+               match self.absolute_expiry {
+                       Some(seconds_from_epoch) => match SystemTime::UNIX_EPOCH.elapsed() {
+                               Ok(elapsed) => elapsed > seconds_from_epoch,
+                               Err(_) => false,
+                       },
+                       None => false,
+               }
+       }
+
+       pub(super) fn chain(&self) -> ChainHash {
                self.chain.unwrap_or_else(|| self.implied_chain())
        }
 
@@ -480,21 +540,21 @@ impl core::fmt::Display for Refund {
 
 #[cfg(test)]
 mod tests {
-       use super::{Refund, RefundBuilder};
+       use super::{Refund, RefundBuilder, RefundTlvStreamRef};
 
        use bitcoin::blockdata::constants::ChainHash;
        use bitcoin::network::constants::Network;
        use bitcoin::secp256k1::{KeyPair, PublicKey, Secp256k1, SecretKey};
        use core::convert::TryFrom;
        use core::time::Duration;
-       use crate::ln::features::InvoiceRequestFeatures;
-       use crate::ln::msgs::MAX_VALUE_MSAT;
+       use crate::ln::features::{InvoiceRequestFeatures, OfferFeatures};
+       use crate::ln::msgs::{DecodeError, MAX_VALUE_MSAT};
        use crate::offers::invoice_request::InvoiceRequestTlvStreamRef;
        use crate::offers::offer::OfferTlvStreamRef;
-       use crate::offers::parse::SemanticError;
+       use crate::offers::parse::{ParseError, SemanticError};
        use crate::offers::payer::PayerTlvStreamRef;
        use crate::onion_message::{BlindedHop, BlindedPath};
-       use crate::util::ser::Writeable;
+       use crate::util::ser::{BigSize, Writeable};
        use crate::util::string::PrintableString;
 
        fn payer_pubkey() -> PublicKey {
@@ -511,6 +571,18 @@ mod tests {
                SecretKey::from_slice(&[byte; 32]).unwrap()
        }
 
+       trait ToBytes {
+               fn to_bytes(&self) -> Vec<u8>;
+       }
+
+       impl<'a> ToBytes for RefundTlvStreamRef<'a> {
+               fn to_bytes(&self) -> Vec<u8> {
+                       let mut buffer = Vec::new();
+                       self.write(&mut buffer).unwrap();
+                       buffer
+               }
+       }
+
        #[test]
        fn builds_refund_with_defaults() {
                let refund = RefundBuilder::new("foo".into(), vec![1; 32], payer_pubkey(), 1000).unwrap()
@@ -700,4 +772,229 @@ mod tests {
                assert_eq!(refund.payer_note(), Some(PrintableString("baz")));
                assert_eq!(tlv_stream.payer_note, Some(&String::from("baz")));
        }
+
+       #[test]
+       fn parses_refund_with_metadata() {
+               let refund = RefundBuilder::new("foo".into(), vec![1; 32], payer_pubkey(), 1000).unwrap()
+                       .build().unwrap();
+               if let Err(e) = refund.to_string().parse::<Refund>() {
+                       panic!("error parsing refund: {:?}", e);
+               }
+
+               let mut tlv_stream = refund.as_tlv_stream();
+               tlv_stream.0.metadata = None;
+
+               match Refund::try_from(tlv_stream.to_bytes()) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => {
+                               assert_eq!(e, ParseError::InvalidSemantics(SemanticError::MissingPayerMetadata));
+                       },
+               }
+       }
+
+       #[test]
+       fn parses_refund_with_description() {
+               let refund = RefundBuilder::new("foo".into(), vec![1; 32], payer_pubkey(), 1000).unwrap()
+                       .build().unwrap();
+               if let Err(e) = refund.to_string().parse::<Refund>() {
+                       panic!("error parsing refund: {:?}", e);
+               }
+
+               let mut tlv_stream = refund.as_tlv_stream();
+               tlv_stream.1.description = None;
+
+               match Refund::try_from(tlv_stream.to_bytes()) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => {
+                               assert_eq!(e, ParseError::InvalidSemantics(SemanticError::MissingDescription));
+                       },
+               }
+       }
+
+       #[test]
+       fn parses_refund_with_amount() {
+               let refund = RefundBuilder::new("foo".into(), vec![1; 32], payer_pubkey(), 1000).unwrap()
+                       .build().unwrap();
+               if let Err(e) = refund.to_string().parse::<Refund>() {
+                       panic!("error parsing refund: {:?}", e);
+               }
+
+               let mut tlv_stream = refund.as_tlv_stream();
+               tlv_stream.2.amount = None;
+
+               match Refund::try_from(tlv_stream.to_bytes()) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => {
+                               assert_eq!(e, ParseError::InvalidSemantics(SemanticError::MissingAmount));
+                       },
+               }
+
+               let mut tlv_stream = refund.as_tlv_stream();
+               tlv_stream.2.amount = Some(MAX_VALUE_MSAT + 1);
+
+               match Refund::try_from(tlv_stream.to_bytes()) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => {
+                               assert_eq!(e, ParseError::InvalidSemantics(SemanticError::InvalidAmount));
+                       },
+               }
+       }
+
+       #[test]
+       fn parses_refund_with_payer_id() {
+               let refund = RefundBuilder::new("foo".into(), vec![1; 32], payer_pubkey(), 1000).unwrap()
+                       .build().unwrap();
+               if let Err(e) = refund.to_string().parse::<Refund>() {
+                       panic!("error parsing refund: {:?}", e);
+               }
+
+               let mut tlv_stream = refund.as_tlv_stream();
+               tlv_stream.2.payer_id = None;
+
+               match Refund::try_from(tlv_stream.to_bytes()) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => {
+                               assert_eq!(e, ParseError::InvalidSemantics(SemanticError::MissingPayerId));
+                       },
+               }
+       }
+
+       #[test]
+       fn parses_refund_with_optional_fields() {
+               let past_expiry = Duration::from_secs(0);
+               let paths = vec![
+                       BlindedPath {
+                               introduction_node_id: pubkey(40),
+                               blinding_point: pubkey(41),
+                               blinded_hops: vec![
+                                       BlindedHop { blinded_node_id: pubkey(43), encrypted_payload: vec![0; 43] },
+                                       BlindedHop { blinded_node_id: pubkey(44), encrypted_payload: vec![0; 44] },
+                               ],
+                       },
+                       BlindedPath {
+                               introduction_node_id: pubkey(40),
+                               blinding_point: pubkey(41),
+                               blinded_hops: vec![
+                                       BlindedHop { blinded_node_id: pubkey(45), encrypted_payload: vec![0; 45] },
+                                       BlindedHop { blinded_node_id: pubkey(46), encrypted_payload: vec![0; 46] },
+                               ],
+                       },
+               ];
+
+               let refund = RefundBuilder::new("foo".into(), vec![1; 32], payer_pubkey(), 1000).unwrap()
+                       .absolute_expiry(past_expiry)
+                       .issuer("bar".into())
+                       .path(paths[0].clone())
+                       .path(paths[1].clone())
+                       .chain(Network::Testnet)
+                       .features_unchecked(InvoiceRequestFeatures::unknown())
+                       .payer_note("baz".into())
+                       .build()
+                       .unwrap();
+               match refund.to_string().parse::<Refund>() {
+                       Ok(refund) => {
+                               assert_eq!(refund.absolute_expiry(), Some(past_expiry));
+                               #[cfg(feature = "std")]
+                               assert!(refund.is_expired());
+                               assert_eq!(refund.paths(), &paths[..]);
+                               assert_eq!(refund.issuer(), Some(PrintableString("bar")));
+                               assert_eq!(refund.chain(), ChainHash::using_genesis_block(Network::Testnet));
+                               assert_eq!(refund.features(), &InvoiceRequestFeatures::unknown());
+                               assert_eq!(refund.payer_note(), Some(PrintableString("baz")));
+                       },
+                       Err(e) => panic!("error parsing refund: {:?}", e),
+               }
+       }
+
+       #[test]
+       fn fails_parsing_refund_with_unexpected_fields() {
+               let refund = RefundBuilder::new("foo".into(), vec![1; 32], payer_pubkey(), 1000).unwrap()
+                       .build().unwrap();
+               if let Err(e) = refund.to_string().parse::<Refund>() {
+                       panic!("error parsing refund: {:?}", e);
+               }
+
+               let chains = vec![ChainHash::using_genesis_block(Network::Testnet)];
+               let mut tlv_stream = refund.as_tlv_stream();
+               tlv_stream.1.chains = Some(&chains);
+
+               match Refund::try_from(tlv_stream.to_bytes()) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => {
+                               assert_eq!(e, ParseError::InvalidSemantics(SemanticError::UnexpectedChain));
+                       },
+               }
+
+               let mut tlv_stream = refund.as_tlv_stream();
+               tlv_stream.1.currency = Some(&b"USD");
+               tlv_stream.1.amount = Some(1000);
+
+               match Refund::try_from(tlv_stream.to_bytes()) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => {
+                               assert_eq!(e, ParseError::InvalidSemantics(SemanticError::UnexpectedAmount));
+                       },
+               }
+
+               let features = OfferFeatures::unknown();
+               let mut tlv_stream = refund.as_tlv_stream();
+               tlv_stream.1.features = Some(&features);
+
+               match Refund::try_from(tlv_stream.to_bytes()) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => {
+                               assert_eq!(e, ParseError::InvalidSemantics(SemanticError::UnexpectedFeatures));
+                       },
+               }
+
+               let mut tlv_stream = refund.as_tlv_stream();
+               tlv_stream.1.quantity_max = Some(10);
+
+               match Refund::try_from(tlv_stream.to_bytes()) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => {
+                               assert_eq!(e, ParseError::InvalidSemantics(SemanticError::UnexpectedQuantity));
+                       },
+               }
+
+               let node_id = payer_pubkey();
+               let mut tlv_stream = refund.as_tlv_stream();
+               tlv_stream.1.node_id = Some(&node_id);
+
+               match Refund::try_from(tlv_stream.to_bytes()) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => {
+                               assert_eq!(e, ParseError::InvalidSemantics(SemanticError::UnexpectedSigningPubkey));
+                       },
+               }
+
+               let mut tlv_stream = refund.as_tlv_stream();
+               tlv_stream.2.quantity = Some(10);
+
+               match Refund::try_from(tlv_stream.to_bytes()) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => {
+                               assert_eq!(e, ParseError::InvalidSemantics(SemanticError::UnexpectedQuantity));
+                       },
+               }
+       }
+
+       #[test]
+       fn fails_parsing_refund_with_extra_tlv_records() {
+               let secp_ctx = Secp256k1::new();
+               let keys = KeyPair::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32]).unwrap());
+               let refund = RefundBuilder::new("foo".into(), vec![1; 32], keys.public_key(), 1000).unwrap()
+                       .build().unwrap();
+
+               let mut encoded_refund = Vec::new();
+               refund.write(&mut encoded_refund).unwrap();
+               BigSize(1002).write(&mut encoded_refund).unwrap();
+               BigSize(32).write(&mut encoded_refund).unwrap();
+               [42u8; 32].write(&mut encoded_refund).unwrap();
+
+               match Refund::try_from(encoded_refund) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => assert_eq!(e, ParseError::Decode(DecodeError::InvalidValue)),
+               }
+       }
 }