InvoiceRequest metadata and payer id derivation
[rust-lightning] / lightning / src / offers / invoice_request.rs
index 8364814ede3061f460192572bb282aaa27da5c23..26151dfbd18500bf2392c89a2b900c945d9896a6 100644 (file)
 
 use bitcoin::blockdata::constants::ChainHash;
 use bitcoin::network::constants::Network;
-use bitcoin::secp256k1::{Message, PublicKey};
+use bitcoin::secp256k1::{KeyPair, Message, PublicKey, Secp256k1, self};
 use bitcoin::secp256k1::schnorr::Signature;
-use core::convert::TryFrom;
+use core::convert::{Infallible, TryFrom};
+use core::ops::Deref;
+use crate::chain::keysinterface::EntropySource;
 use crate::io;
 use crate::ln::PaymentHash;
 use crate::ln::features::InvoiceRequestFeatures;
+use crate::ln::inbound_payment::{ExpandedKey, IV_LEN, Nonce};
 use crate::ln::msgs::DecodeError;
 use crate::offers::invoice::{BlindedPayInfo, InvoiceBuilder};
-use crate::offers::merkle::{SignError, SignatureTlvStream, SignatureTlvStreamRef, self};
+use crate::offers::merkle::{SignError, SignatureTlvStream, SignatureTlvStreamRef, TlvStream, self};
 use crate::offers::offer::{Offer, OfferContents, OfferTlvStream, OfferTlvStreamRef};
 use crate::offers::parse::{ParseError, ParsedMessage, SemanticError};
 use crate::offers::payer::{PayerContents, PayerTlvStream, PayerTlvStreamRef};
+use crate::offers::signer::{Metadata, MetadataMaterial};
 use crate::onion_message::BlindedPath;
 use crate::util::ser::{HighZeroBytesDroppedBigSize, SeekReadable, WithoutLength, Writeable, Writer};
 use crate::util::string::PrintableString;
@@ -74,25 +78,83 @@ use crate::prelude::*;
 
 const SIGNATURE_TAG: &'static str = concat!("lightning", "invoice_request", "signature");
 
+const IV_BYTES: &[u8; IV_LEN] = b"LDK Invreq ~~~~~";
+
 /// Builds an [`InvoiceRequest`] from an [`Offer`] for the "offer to be paid" flow.
 ///
 /// See [module-level documentation] for usage.
 ///
 /// [module-level documentation]: self
-pub struct InvoiceRequestBuilder<'a> {
+pub struct InvoiceRequestBuilder<'a, 'b, P: PayerIdStrategy, T: secp256k1::Signing> {
        offer: &'a Offer,
-       invoice_request: InvoiceRequestContents,
+       invoice_request: InvoiceRequestContentsWithoutPayerId,
+       payer_id: Option<PublicKey>,
+       payer_id_strategy: core::marker::PhantomData<P>,
+       secp_ctx: Option<&'b Secp256k1<T>>,
 }
 
-impl<'a> InvoiceRequestBuilder<'a> {
+/// Indicates how [`InvoiceRequest::payer_id`] will be set.
+pub trait PayerIdStrategy {}
+
+/// [`InvoiceRequest::payer_id`] will be explicitly set.
+pub struct ExplicitPayerId {}
+
+/// [`InvoiceRequest::payer_id`] will be derived.
+pub struct DerivedPayerId {}
+
+impl PayerIdStrategy for ExplicitPayerId {}
+impl PayerIdStrategy for DerivedPayerId {}
+
+impl<'a, 'b, T: secp256k1::Signing> InvoiceRequestBuilder<'a, 'b, ExplicitPayerId, T> {
        pub(super) fn new(offer: &'a Offer, metadata: Vec<u8>, payer_id: PublicKey) -> Self {
                Self {
                        offer,
-                       invoice_request: InvoiceRequestContents {
-                               payer: PayerContents(metadata), offer: offer.contents.clone(), chain: None,
-                               amount_msats: None, features: InvoiceRequestFeatures::empty(), quantity: None,
-                               payer_id, payer_note: None,
-                       },
+                       invoice_request: Self::create_contents(offer, Metadata::Bytes(metadata)),
+                       payer_id: Some(payer_id),
+                       payer_id_strategy: core::marker::PhantomData,
+                       secp_ctx: None,
+               }
+       }
+
+       pub(super) fn deriving_metadata<ES: Deref>(
+               offer: &'a Offer, payer_id: PublicKey, expanded_key: &ExpandedKey, entropy_source: ES
+       ) -> Self where ES::Target: EntropySource {
+               let nonce = Nonce::from_entropy_source(entropy_source);
+               let derivation_material = MetadataMaterial::new(nonce, expanded_key, IV_BYTES);
+               let metadata = Metadata::Derived(derivation_material);
+               Self {
+                       offer,
+                       invoice_request: Self::create_contents(offer, metadata),
+                       payer_id: Some(payer_id),
+                       payer_id_strategy: core::marker::PhantomData,
+                       secp_ctx: None,
+               }
+       }
+}
+
+impl<'a, 'b, T: secp256k1::Signing> InvoiceRequestBuilder<'a, 'b, DerivedPayerId, T> {
+       pub(super) fn deriving_payer_id<ES: Deref>(
+               offer: &'a Offer, expanded_key: &ExpandedKey, entropy_source: ES, secp_ctx: &'b Secp256k1<T>
+       ) -> Self where ES::Target: EntropySource {
+               let nonce = Nonce::from_entropy_source(entropy_source);
+               let derivation_material = MetadataMaterial::new(nonce, expanded_key, IV_BYTES);
+               let metadata = Metadata::DerivedSigningPubkey(derivation_material);
+               Self {
+                       offer,
+                       invoice_request: Self::create_contents(offer, metadata),
+                       payer_id: None,
+                       payer_id_strategy: core::marker::PhantomData,
+                       secp_ctx: Some(secp_ctx),
+               }
+       }
+}
+
+impl<'a, 'b, P: PayerIdStrategy, T: secp256k1::Signing> InvoiceRequestBuilder<'a, 'b, P, T> {
+       fn create_contents(offer: &Offer, metadata: Metadata) -> InvoiceRequestContentsWithoutPayerId {
+               let offer = offer.contents.clone();
+               InvoiceRequestContentsWithoutPayerId {
+                       payer: PayerContents(metadata), offer, chain: None, amount_msats: None,
+                       features: InvoiceRequestFeatures::empty(), quantity: None, payer_note: None,
                }
        }
 
@@ -143,9 +205,10 @@ impl<'a> InvoiceRequestBuilder<'a> {
                self
        }
 
-       /// Builds an unsigned [`InvoiceRequest`] after checking for valid semantics. It can be signed
-       /// by [`UnsignedInvoiceRequest::sign`].
-       pub fn build(mut self) -> Result<UnsignedInvoiceRequest<'a>, SemanticError> {
+       fn build_with_checks(mut self) -> Result<
+               (UnsignedInvoiceRequest<'a>, Option<KeyPair>, Option<&'b Secp256k1<T>>),
+               SemanticError
+       > {
                #[cfg(feature = "std")] {
                        if self.offer.is_expired() {
                                return Err(SemanticError::AlreadyExpired);
@@ -170,13 +233,79 @@ impl<'a> InvoiceRequestBuilder<'a> {
                        self.invoice_request.amount_msats, self.invoice_request.quantity
                )?;
 
-               let InvoiceRequestBuilder { offer, invoice_request } = self;
-               Ok(UnsignedInvoiceRequest { offer, invoice_request })
+               Ok(self.build_without_checks())
+       }
+
+       fn build_without_checks(mut self) ->
+               (UnsignedInvoiceRequest<'a>, Option<KeyPair>, Option<&'b Secp256k1<T>>)
+       {
+               // Create the metadata for stateless verification of an Invoice.
+               let mut keys = None;
+               let secp_ctx = self.secp_ctx.clone();
+               if self.invoice_request.payer.0.has_derivation_material() {
+                       let mut metadata = core::mem::take(&mut self.invoice_request.payer.0);
+
+                       let mut tlv_stream = self.invoice_request.as_tlv_stream();
+                       debug_assert!(tlv_stream.2.payer_id.is_none());
+                       tlv_stream.0.metadata = None;
+                       if !metadata.derives_keys() {
+                               tlv_stream.2.payer_id = self.payer_id.as_ref();
+                       }
+
+                       let (derived_metadata, derived_keys) = metadata.derive_from(tlv_stream, self.secp_ctx);
+                       metadata = derived_metadata;
+                       keys = derived_keys;
+                       if let Some(keys) = keys {
+                               debug_assert!(self.payer_id.is_none());
+                               self.payer_id = Some(keys.public_key());
+                       }
+
+                       self.invoice_request.payer.0 = metadata;
+               }
+
+               debug_assert!(self.invoice_request.payer.0.as_bytes().is_some());
+               debug_assert!(self.payer_id.is_some());
+               let payer_id = self.payer_id.unwrap();
+
+               let unsigned_invoice = UnsignedInvoiceRequest {
+                       offer: self.offer,
+                       invoice_request: InvoiceRequestContents {
+                               inner: self.invoice_request,
+                               payer_id,
+                       },
+               };
+
+               (unsigned_invoice, keys, secp_ctx)
+       }
+}
+
+impl<'a, 'b, T: secp256k1::Signing> InvoiceRequestBuilder<'a, 'b, ExplicitPayerId, T> {
+       /// Builds an unsigned [`InvoiceRequest`] after checking for valid semantics. It can be signed
+       /// by [`UnsignedInvoiceRequest::sign`].
+       pub fn build(self) -> Result<UnsignedInvoiceRequest<'a>, SemanticError> {
+               let (unsigned_invoice_request, keys, _) = self.build_with_checks()?;
+               debug_assert!(keys.is_none());
+               Ok(unsigned_invoice_request)
+       }
+}
+
+impl<'a, 'b, T: secp256k1::Signing> InvoiceRequestBuilder<'a, 'b, DerivedPayerId, T> {
+       /// Builds a signed [`InvoiceRequest`] after checking for valid semantics.
+       pub fn build_and_sign(self) -> Result<InvoiceRequest, SemanticError> {
+               let (unsigned_invoice_request, keys, secp_ctx) = self.build_with_checks()?;
+               debug_assert!(keys.is_some());
+
+               let secp_ctx = secp_ctx.unwrap();
+               let keys = keys.unwrap();
+               let invoice_request = unsigned_invoice_request
+                       .sign::<_, Infallible>(|digest| Ok(secp_ctx.sign_schnorr_no_aux_rand(digest, &keys)))
+                       .unwrap();
+               Ok(invoice_request)
        }
 }
 
 #[cfg(test)]
-impl<'a> InvoiceRequestBuilder<'a> {
+impl<'a, 'b, P: PayerIdStrategy, T: secp256k1::Signing> InvoiceRequestBuilder<'a, 'b, P, T> {
        fn chain_unchecked(mut self, network: Network) -> Self {
                let chain = ChainHash::using_genesis_block(network);
                self.invoice_request.chain = Some(chain);
@@ -199,8 +328,7 @@ impl<'a> InvoiceRequestBuilder<'a> {
        }
 
        pub(super) fn build_unchecked(self) -> UnsignedInvoiceRequest<'a> {
-               let InvoiceRequestBuilder { offer, invoice_request } = self;
-               UnsignedInvoiceRequest { offer, invoice_request }
+               self.build_without_checks().0
        }
 }
 
@@ -250,7 +378,8 @@ impl<'a> UnsignedInvoiceRequest<'a> {
 ///
 /// [`Invoice`]: crate::offers::invoice::Invoice
 /// [`Offer`]: crate::offers::offer::Offer
-#[derive(Clone, Debug, PartialEq)]
+#[derive(Clone, Debug)]
+#[cfg_attr(test, derive(PartialEq))]
 pub struct InvoiceRequest {
        pub(super) bytes: Vec<u8>,
        pub(super) contents: InvoiceRequestContents,
@@ -260,15 +389,22 @@ pub struct InvoiceRequest {
 /// The contents of an [`InvoiceRequest`], which may be shared with an [`Invoice`].
 ///
 /// [`Invoice`]: crate::offers::invoice::Invoice
-#[derive(Clone, Debug, PartialEq)]
+#[derive(Clone, Debug)]
+#[cfg_attr(test, derive(PartialEq))]
 pub(super) struct InvoiceRequestContents {
+       pub(super) inner: InvoiceRequestContentsWithoutPayerId,
+       payer_id: PublicKey,
+}
+
+#[derive(Clone, Debug)]
+#[cfg_attr(test, derive(PartialEq))]
+pub(super) struct InvoiceRequestContentsWithoutPayerId {
        payer: PayerContents,
        pub(super) offer: OfferContents,
        chain: Option<ChainHash>,
        amount_msats: Option<u64>,
        features: InvoiceRequestFeatures,
        quantity: Option<u64>,
-       payer_id: PublicKey,
        payer_note: Option<String>,
 }
 
@@ -278,7 +414,7 @@ impl InvoiceRequest {
        ///
        /// [`payer_id`]: Self::payer_id
        pub fn metadata(&self) -> &[u8] {
-               &self.contents.payer.0[..]
+               self.contents.metadata()
        }
 
        /// A chain from [`Offer::chains`] that the offer is valid for.
@@ -291,17 +427,17 @@ impl InvoiceRequest {
        ///
        /// [`chain`]: Self::chain
        pub fn amount_msats(&self) -> Option<u64> {
-               self.contents.amount_msats
+               self.contents.inner.amount_msats
        }
 
        /// Features pertaining to requesting an invoice.
        pub fn features(&self) -> &InvoiceRequestFeatures {
-               &self.contents.features
+               &self.contents.inner.features
        }
 
        /// The quantity of the offer's item conforming to [`Offer::is_valid_quantity`].
        pub fn quantity(&self) -> Option<u64> {
-               self.contents.quantity
+               self.contents.inner.quantity
        }
 
        /// A possibly transient pubkey used to sign the invoice request.
@@ -312,7 +448,8 @@ impl InvoiceRequest {
        /// A payer-provided note which will be seen by the recipient and reflected back in the invoice
        /// response.
        pub fn payer_note(&self) -> Option<PrintableString> {
-               self.contents.payer_note.as_ref().map(|payer_note| PrintableString(payer_note.as_str()))
+               self.contents.inner.payer_note.as_ref()
+                       .map(|payer_note| PrintableString(payer_note.as_str()))
        }
 
        /// Signature of the invoice request using [`payer_id`].
@@ -370,6 +507,13 @@ impl InvoiceRequest {
                InvoiceBuilder::for_offer(self, payment_paths, created_at, payment_hash)
        }
 
+       /// Verifies that the request was for an offer created using the given key.
+       pub fn verify<T: secp256k1::Signing>(
+               &self, key: &ExpandedKey, secp_ctx: &Secp256k1<T>
+       ) -> bool {
+               self.contents.inner.offer.verify(TlvStream::new(&self.bytes), key, secp_ctx)
+       }
+
        #[cfg(test)]
        fn as_tlv_stream(&self) -> FullInvoiceRequestTlvStreamRef {
                let (payer_tlv_stream, offer_tlv_stream, invoice_request_tlv_stream) =
@@ -382,13 +526,33 @@ impl InvoiceRequest {
 }
 
 impl InvoiceRequestContents {
+       pub fn metadata(&self) -> &[u8] {
+               self.inner.metadata()
+       }
+
+       pub(super) fn chain(&self) -> ChainHash {
+               self.inner.chain()
+       }
+
+       pub(super) fn as_tlv_stream(&self) -> PartialInvoiceRequestTlvStreamRef {
+               let (payer, offer, mut invoice_request) = self.inner.as_tlv_stream();
+               invoice_request.payer_id = Some(&self.payer_id);
+               (payer, offer, invoice_request)
+       }
+}
+
+impl InvoiceRequestContentsWithoutPayerId {
+       pub(super) fn metadata(&self) -> &[u8] {
+               self.payer.0.as_bytes().map(|bytes| bytes.as_slice()).unwrap_or(&[])
+       }
+
        pub(super) fn chain(&self) -> ChainHash {
                self.chain.unwrap_or_else(|| self.offer.implied_chain())
        }
 
        pub(super) fn as_tlv_stream(&self) -> PartialInvoiceRequestTlvStreamRef {
                let payer = PayerTlvStreamRef {
-                       metadata: Some(&self.payer.0),
+                       metadata: self.payer.0.as_bytes(),
                };
 
                let offer = self.offer.as_tlv_stream();
@@ -403,7 +567,7 @@ impl InvoiceRequestContents {
                        amount: self.amount_msats,
                        features,
                        quantity: self.quantity,
-                       payer_id: Some(&self.payer_id),
+                       payer_id: None,
                        payer_note: self.payer_note.as_ref(),
                };
 
@@ -498,7 +662,7 @@ impl TryFrom<PartialInvoiceRequestTlvStream> for InvoiceRequestContents {
 
                let payer = match metadata {
                        None => return Err(SemanticError::MissingPayerMetadata),
-                       Some(metadata) => PayerContents(metadata),
+                       Some(metadata) => PayerContents(Metadata::Bytes(metadata)),
                };
                let offer = OfferContents::try_from(offer_tlv_stream)?;
 
@@ -521,7 +685,10 @@ impl TryFrom<PartialInvoiceRequestTlvStream> for InvoiceRequestContents {
                };
 
                Ok(InvoiceRequestContents {
-                       payer, offer, chain, amount_msats: amount, features, quantity, payer_id, payer_note,
+                       inner: InvoiceRequestContentsWithoutPayerId {
+                               payer, offer, chain, amount_msats: amount, features, quantity, payer_note,
+                       },
+                       payer_id,
                })
        }
 }
@@ -982,12 +1149,28 @@ mod tests {
                }
        }
 
+       #[test]
+       fn fails_responding_with_unknown_required_features() {
+               match OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .build().unwrap()
+                       .request_invoice(vec![42; 32], payer_pubkey()).unwrap()
+                       .features_unchecked(InvoiceRequestFeatures::unknown())
+                       .build().unwrap()
+                       .sign(payer_sign).unwrap()
+                       .respond_with_no_std(payment_paths(), payment_hash(), now())
+               {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => assert_eq!(e, SemanticError::UnknownRequiredFeatures),
+               }
+       }
+
        #[test]
        fn parses_invoice_request_with_metadata() {
                let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
                        .amount_msats(1000)
                        .build().unwrap()
-                       .request_invoice(vec![42; 32], payer_pubkey()).unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
                        .build().unwrap()
                        .sign(payer_sign).unwrap();