TaggedHash for BOLT 12 signing function
[rust-lightning] / lightning / src / offers / invoice_request.rs
index 43ae18d2c00d4c92da0318434fb907247e68eea7..1dea6503f58fd23913874d0aa33c234cc3d50bce 100644 (file)
 // licenses.
 
 //! Data structures and encoding for `invoice_request` messages.
+//!
+//! An [`InvoiceRequest`] can be built from a parsed [`Offer`] as an "offer to be paid". It is
+//! typically constructed by a customer and sent to the merchant who had published the corresponding
+//! offer. The recipient of the request responds with a [`Bolt12Invoice`].
+//!
+//! For an "offer for money" (e.g., refund, ATM withdrawal), where an offer doesn't exist as a
+//! precursor, see [`Refund`].
+//!
+//! [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
+//! [`Refund`]: crate::offers::refund::Refund
+//!
+//! ```
+//! extern crate bitcoin;
+//! extern crate lightning;
+//!
+//! use bitcoin::network::constants::Network;
+//! use bitcoin::secp256k1::{KeyPair, PublicKey, Secp256k1, SecretKey};
+//! use core::convert::Infallible;
+//! use lightning::ln::features::OfferFeatures;
+//! use lightning::offers::offer::Offer;
+//! use lightning::util::ser::Writeable;
+//!
+//! # fn parse() -> Result<(), lightning::offers::parse::Bolt12ParseError> {
+//! let secp_ctx = Secp256k1::new();
+//! let keys = KeyPair::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32])?);
+//! let pubkey = PublicKey::from(keys);
+//! let mut buffer = Vec::new();
+//!
+//! "lno1qcp4256ypq"
+//!     .parse::<Offer>()?
+//!     .request_invoice(vec![42; 64], pubkey)?
+//!     .chain(Network::Testnet)?
+//!     .amount_msats(1000)?
+//!     .quantity(5)?
+//!     .payer_note("foo".to_string())
+//!     .build()?
+//!     .sign::<_, Infallible>(
+//!         |message| Ok(secp_ctx.sign_schnorr_no_aux_rand(message.as_ref().as_digest(), &keys))
+//!     )
+//!     .expect("failed verifying signature")
+//!     .write(&mut buffer)
+//!     .unwrap();
+//! # Ok(())
+//! # }
+//! ```
 
 use bitcoin::blockdata::constants::ChainHash;
-use bitcoin::secp256k1::PublicKey;
+use bitcoin::network::constants::Network;
+use bitcoin::secp256k1::{KeyPair, PublicKey, Secp256k1, self};
 use bitcoin::secp256k1::schnorr::Signature;
+use core::convert::{AsRef, Infallible, TryFrom};
+use core::ops::Deref;
+use crate::sign::EntropySource;
+use crate::io;
+use crate::blinded_path::BlindedPath;
+use crate::ln::PaymentHash;
 use crate::ln::features::InvoiceRequestFeatures;
-use crate::offers::offer::OfferContents;
-use crate::offers::payer::PayerContents;
+use crate::ln::inbound_payment::{ExpandedKey, IV_LEN, Nonce};
+use crate::ln::msgs::DecodeError;
+use crate::offers::invoice::{BlindedPayInfo, DerivedSigningPubkey, ExplicitSigningPubkey, InvoiceBuilder};
+use crate::offers::merkle::{SignError, SignatureTlvStream, SignatureTlvStreamRef, TaggedHash, self};
+use crate::offers::offer::{Offer, OfferContents, OfferTlvStream, OfferTlvStreamRef};
+use crate::offers::parse::{Bolt12ParseError, ParsedMessage, Bolt12SemanticError};
+use crate::offers::payer::{PayerContents, PayerTlvStream, PayerTlvStreamRef};
+use crate::offers::signer::{Metadata, MetadataMaterial};
+use crate::util::ser::{HighZeroBytesDroppedBigSize, SeekReadable, WithoutLength, Writeable, Writer};
 use crate::util::string::PrintableString;
 
 use crate::prelude::*;
 
-/// An `InvoiceRequest` is a request for an `Invoice` formulated from an [`Offer`].
+/// Tag for the hash function used when signing an [`InvoiceRequest`]'s merkle root.
+pub const SIGNATURE_TAG: &'static str = concat!("lightning", "invoice_request", "signature");
+
+pub(super) 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.
+///
+/// This is not exported to bindings users as builder patterns don't map outside of move semantics.
+///
+/// [module-level documentation]: self
+pub struct InvoiceRequestBuilder<'a, 'b, P: PayerIdStrategy, T: secp256k1::Signing> {
+       offer: &'a Offer,
+       invoice_request: InvoiceRequestContentsWithoutPayerId,
+       payer_id: Option<PublicKey>,
+       payer_id_strategy: core::marker::PhantomData<P>,
+       secp_ctx: Option<&'b Secp256k1<T>>,
+}
+
+/// Indicates how [`InvoiceRequest::payer_id`] will be set.
+///
+/// This is not exported to bindings users as builder patterns don't map outside of move semantics.
+pub trait PayerIdStrategy {}
+
+/// [`InvoiceRequest::payer_id`] will be explicitly set.
+///
+/// This is not exported to bindings users as builder patterns don't map outside of move semantics.
+pub struct ExplicitPayerId {}
+
+/// [`InvoiceRequest::payer_id`] will be derived.
+///
+/// This is not exported to bindings users as builder patterns don't map outside of move semantics.
+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: 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,
+               }
+       }
+
+       /// Sets the [`InvoiceRequest::chain`] of the given [`Network`] for paying an invoice. If not
+       /// called, [`Network::Bitcoin`] is assumed. Errors if the chain for `network` is not supported
+       /// by the offer.
+       ///
+       /// Successive calls to this method will override the previous setting.
+       pub fn chain(mut self, network: Network) -> Result<Self, Bolt12SemanticError> {
+               let chain = ChainHash::using_genesis_block(network);
+               if !self.offer.supports_chain(chain) {
+                       return Err(Bolt12SemanticError::UnsupportedChain);
+               }
+
+               self.invoice_request.chain = Some(chain);
+               Ok(self)
+       }
+
+       /// Sets the [`InvoiceRequest::amount_msats`] for paying an invoice. Errors if `amount_msats` is
+       /// not at least the expected invoice amount (i.e., [`Offer::amount`] times [`quantity`]).
+       ///
+       /// Successive calls to this method will override the previous setting.
+       ///
+       /// [`quantity`]: Self::quantity
+       pub fn amount_msats(mut self, amount_msats: u64) -> Result<Self, Bolt12SemanticError> {
+               self.invoice_request.offer.check_amount_msats_for_quantity(
+                       Some(amount_msats), self.invoice_request.quantity
+               )?;
+               self.invoice_request.amount_msats = Some(amount_msats);
+               Ok(self)
+       }
+
+       /// Sets [`InvoiceRequest::quantity`] of items. If not set, `1` is assumed. Errors if `quantity`
+       /// does not conform to [`Offer::is_valid_quantity`].
+       ///
+       /// Successive calls to this method will override the previous setting.
+       pub fn quantity(mut self, quantity: u64) -> Result<Self, Bolt12SemanticError> {
+               self.invoice_request.offer.check_quantity(Some(quantity))?;
+               self.invoice_request.quantity = Some(quantity);
+               Ok(self)
+       }
+
+       /// Sets the [`InvoiceRequest::payer_note`].
+       ///
+       /// Successive calls to this method will override the previous setting.
+       pub fn payer_note(mut self, payer_note: String) -> Self {
+               self.invoice_request.payer_note = Some(payer_note);
+               self
+       }
+
+       fn build_with_checks(mut self) -> Result<
+               (UnsignedInvoiceRequest, Option<KeyPair>, Option<&'b Secp256k1<T>>),
+               Bolt12SemanticError
+       > {
+               #[cfg(feature = "std")] {
+                       if self.offer.is_expired() {
+                               return Err(Bolt12SemanticError::AlreadyExpired);
+                       }
+               }
+
+               let chain = self.invoice_request.chain();
+               if !self.offer.supports_chain(chain) {
+                       return Err(Bolt12SemanticError::UnsupportedChain);
+               }
+
+               if chain == self.offer.implied_chain() {
+                       self.invoice_request.chain = None;
+               }
+
+               if self.offer.amount().is_none() && self.invoice_request.amount_msats.is_none() {
+                       return Err(Bolt12SemanticError::MissingAmount);
+               }
+
+               self.invoice_request.offer.check_quantity(self.invoice_request.quantity)?;
+               self.invoice_request.offer.check_amount_msats_for_quantity(
+                       self.invoice_request.amount_msats, self.invoice_request.quantity
+               )?;
+
+               Ok(self.build_without_checks())
+       }
+
+       fn build_without_checks(mut self) ->
+               (UnsignedInvoiceRequest, Option<KeyPair>, Option<&'b Secp256k1<T>>)
+       {
+               // Create the metadata for stateless verification of a Bolt12Invoice.
+               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 invoice_request = InvoiceRequestContents {
+                       inner: self.invoice_request,
+                       payer_id,
+               };
+               let unsigned_invoice_request = UnsignedInvoiceRequest::new(self.offer, invoice_request);
+
+               (unsigned_invoice_request, 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, Bolt12SemanticError> {
+               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, Bolt12SemanticError> {
+               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>(
+                               |message| Ok(secp_ctx.sign_schnorr_no_aux_rand(message.as_ref().as_digest(), &keys))
+                       )
+                       .unwrap();
+               Ok(invoice_request)
+       }
+}
+
+#[cfg(test)]
+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);
+               self
+       }
+
+       fn amount_msats_unchecked(mut self, amount_msats: u64) -> Self {
+               self.invoice_request.amount_msats = Some(amount_msats);
+               self
+       }
+
+       fn features_unchecked(mut self, features: InvoiceRequestFeatures) -> Self {
+               self.invoice_request.features = features;
+               self
+       }
+
+       fn quantity_unchecked(mut self, quantity: u64) -> Self {
+               self.invoice_request.quantity = Some(quantity);
+               self
+       }
+
+       pub(super) fn build_unchecked(self) -> UnsignedInvoiceRequest {
+               self.build_without_checks().0
+       }
+}
+
+/// A semantically valid [`InvoiceRequest`] that hasn't been signed.
+pub struct UnsignedInvoiceRequest {
+       bytes: Vec<u8>,
+       invoice_request: InvoiceRequestContents,
+       tagged_hash: TaggedHash,
+}
+
+impl UnsignedInvoiceRequest {
+       fn new(offer: &Offer, invoice_request: InvoiceRequestContents) -> Self {
+               // Use the offer bytes instead of the offer TLV stream as the offer may have contained
+               // unknown TLV records, which are not stored in `OfferContents`.
+               let (payer_tlv_stream, _offer_tlv_stream, invoice_request_tlv_stream) =
+                       invoice_request.as_tlv_stream();
+               let offer_bytes = WithoutLength(&offer.bytes);
+               let unsigned_tlv_stream = (payer_tlv_stream, offer_bytes, invoice_request_tlv_stream);
+
+               let mut bytes = Vec::new();
+               unsigned_tlv_stream.write(&mut bytes).unwrap();
+
+               let tagged_hash = TaggedHash::new(SIGNATURE_TAG, &bytes);
+
+               Self { bytes, invoice_request, tagged_hash }
+       }
+
+       /// Signs the invoice request using the given function.
+       ///
+       /// This is not exported to bindings users as functions are not yet mapped.
+       pub fn sign<F, E>(mut self, sign: F) -> Result<InvoiceRequest, SignError<E>>
+       where
+               F: FnOnce(&Self) -> Result<Signature, E>
+       {
+               let pubkey = self.invoice_request.payer_id;
+               let signature = merkle::sign_message(sign, &self, pubkey)?;
+
+               // Append the signature TLV record to the bytes.
+               let signature_tlv_stream = SignatureTlvStreamRef {
+                       signature: Some(&signature),
+               };
+               signature_tlv_stream.write(&mut self.bytes).unwrap();
+
+               Ok(InvoiceRequest {
+                       bytes: self.bytes,
+                       contents: self.invoice_request,
+                       signature,
+               })
+       }
+}
+
+impl AsRef<TaggedHash> for UnsignedInvoiceRequest {
+       fn as_ref(&self) -> &TaggedHash {
+               &self.tagged_hash
+       }
+}
+
+/// An `InvoiceRequest` is a request for a [`Bolt12Invoice`] formulated from an [`Offer`].
 ///
 /// An offer may provide choices such as quantity, amount, chain, features, etc. An invoice request
 /// specifies these such that its recipient can send an invoice for payment.
 ///
+/// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
 /// [`Offer`]: crate::offers::offer::Offer
 #[derive(Clone, Debug)]
+#[cfg_attr(test, derive(PartialEq))]
 pub struct InvoiceRequest {
-       bytes: Vec<u8>,
-       contents: InvoiceRequestContents,
-       signature: Option<Signature>,
+       pub(super) bytes: Vec<u8>,
+       pub(super) contents: InvoiceRequestContents,
+       signature: Signature,
 }
 
-/// The contents of an [`InvoiceRequest`], which may be shared with an `Invoice`.
+/// The contents of an [`InvoiceRequest`], which may be shared with an [`Bolt12Invoice`].
+///
+/// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
 #[derive(Clone, Debug)]
-pub(crate) struct InvoiceRequestContents {
+#[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,
-       offer: OfferContents,
+       pub(super) offer: OfferContents,
        chain: Option<ChainHash>,
        amount_msats: Option<u64>,
        features: InvoiceRequestFeatures,
        quantity: Option<u64>,
-       payer_id: PublicKey,
        payer_note: Option<String>,
 }
 
@@ -51,35 +440,30 @@ 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.
-       ///
-       /// [`Offer::chains`]: crate::offers::offer::Offer::chains
        pub fn chain(&self) -> ChainHash {
-               self.contents.chain.unwrap_or_else(|| self.contents.offer.implied_chain())
+               self.contents.chain()
        }
 
        /// The amount to pay in msats (i.e., the minimum lightning-payable unit for [`chain`]), which
        /// must be greater than or equal to [`Offer::amount`], converted if necessary.
        ///
        /// [`chain`]: Self::chain
-       /// [`Offer::amount`]: crate::offers::offer::Offer::amount
        pub fn amount_msats(&self) -> Option<u64> {
-               self.contents.amount_msats
+               self.contents.inner.amount_msats
        }
 
-       /// Features for paying the invoice.
+       /// 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::supported_quantity`].
-       ///
-       /// [`Offer::supported_quantity`]: crate::offers::offer::Offer::supported_quantity
+       /// 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.
@@ -87,15 +471,1332 @@ impl InvoiceRequest {
                self.contents.payer_id
        }
 
-       /// Payer provided note to include in the invoice.
+       /// 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`].
        ///
        /// [`payer_id`]: Self::payer_id
-       pub fn signature(&self) -> Option<Signature> {
+       pub fn signature(&self) -> Signature {
                self.signature
        }
+
+       /// Creates an [`InvoiceBuilder`] for the request with the given required fields and using the
+       /// [`Duration`] since [`std::time::SystemTime::UNIX_EPOCH`] as the creation time.
+       ///
+       /// See [`InvoiceRequest::respond_with_no_std`] for further details where the aforementioned
+       /// creation time is used for the `created_at` parameter.
+       ///
+       /// This is not exported to bindings users as builder patterns don't map outside of move semantics.
+       ///
+       /// [`Duration`]: core::time::Duration
+       #[cfg(feature = "std")]
+       pub fn respond_with(
+               &self, payment_paths: Vec<(BlindedPayInfo, BlindedPath)>, payment_hash: PaymentHash
+       ) -> Result<InvoiceBuilder<ExplicitSigningPubkey>, Bolt12SemanticError> {
+               let created_at = std::time::SystemTime::now()
+                       .duration_since(std::time::SystemTime::UNIX_EPOCH)
+                       .expect("SystemTime::now() should come after SystemTime::UNIX_EPOCH");
+
+               self.respond_with_no_std(payment_paths, payment_hash, created_at)
+       }
+
+       /// Creates an [`InvoiceBuilder`] for the request with the given required fields.
+       ///
+       /// Unless [`InvoiceBuilder::relative_expiry`] is set, the invoice will expire two hours after
+       /// `created_at`, which is used to set [`Bolt12Invoice::created_at`]. Useful for `no-std` builds
+       /// where [`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 `payment_paths` parameter is useful for maintaining the payment recipient's privacy. It
+       /// must contain one or more elements ordered from most-preferred to least-preferred, if there's
+       /// a preference. Note, however, that any privacy is lost if a public node id was used for
+       /// [`Offer::signing_pubkey`].
+       ///
+       /// Errors if the request contains unknown required features.
+       ///
+       /// This is not exported to bindings users as builder patterns don't map outside of move semantics.
+       ///
+       /// [`Bolt12Invoice::created_at`]: crate::offers::invoice::Bolt12Invoice::created_at
+       pub fn respond_with_no_std(
+               &self, payment_paths: Vec<(BlindedPayInfo, BlindedPath)>, payment_hash: PaymentHash,
+               created_at: core::time::Duration
+       ) -> Result<InvoiceBuilder<ExplicitSigningPubkey>, Bolt12SemanticError> {
+               if self.features().requires_unknown_bits() {
+                       return Err(Bolt12SemanticError::UnknownRequiredFeatures);
+               }
+
+               InvoiceBuilder::for_offer(self, payment_paths, created_at, payment_hash)
+       }
+
+       /// Creates an [`InvoiceBuilder`] for the request using the given required fields and that uses
+       /// derived signing keys from the originating [`Offer`] to sign the [`Bolt12Invoice`]. Must use
+       /// the same [`ExpandedKey`] as the one used to create the offer.
+       ///
+       /// See [`InvoiceRequest::respond_with`] for further details.
+       ///
+       /// This is not exported to bindings users as builder patterns don't map outside of move semantics.
+       ///
+       /// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
+       #[cfg(feature = "std")]
+       pub fn verify_and_respond_using_derived_keys<T: secp256k1::Signing>(
+               &self, payment_paths: Vec<(BlindedPayInfo, BlindedPath)>, payment_hash: PaymentHash,
+               expanded_key: &ExpandedKey, secp_ctx: &Secp256k1<T>
+       ) -> Result<InvoiceBuilder<DerivedSigningPubkey>, Bolt12SemanticError> {
+               let created_at = std::time::SystemTime::now()
+                       .duration_since(std::time::SystemTime::UNIX_EPOCH)
+                       .expect("SystemTime::now() should come after SystemTime::UNIX_EPOCH");
+
+               self.verify_and_respond_using_derived_keys_no_std(
+                       payment_paths, payment_hash, created_at, expanded_key, secp_ctx
+               )
+       }
+
+       /// Creates an [`InvoiceBuilder`] for the request using the given required fields and that uses
+       /// derived signing keys from the originating [`Offer`] to sign the [`Bolt12Invoice`]. Must use
+       /// the same [`ExpandedKey`] as the one used to create the offer.
+       ///
+       /// See [`InvoiceRequest::respond_with_no_std`] for further details.
+       ///
+       /// This is not exported to bindings users as builder patterns don't map outside of move semantics.
+       ///
+       /// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
+       pub fn verify_and_respond_using_derived_keys_no_std<T: secp256k1::Signing>(
+               &self, payment_paths: Vec<(BlindedPayInfo, BlindedPath)>, payment_hash: PaymentHash,
+               created_at: core::time::Duration, expanded_key: &ExpandedKey, secp_ctx: &Secp256k1<T>
+       ) -> Result<InvoiceBuilder<DerivedSigningPubkey>, Bolt12SemanticError> {
+               if self.features().requires_unknown_bits() {
+                       return Err(Bolt12SemanticError::UnknownRequiredFeatures);
+               }
+
+               let keys = match self.verify(expanded_key, secp_ctx) {
+                       Err(()) => return Err(Bolt12SemanticError::InvalidMetadata),
+                       Ok(None) => return Err(Bolt12SemanticError::InvalidMetadata),
+                       Ok(Some(keys)) => keys,
+               };
+
+               InvoiceBuilder::for_offer_using_keys(self, payment_paths, created_at, payment_hash, keys)
+       }
+
+       /// Verifies that the request was for an offer created using the given key. Returns the derived
+       /// keys need to sign an [`Bolt12Invoice`] for the request if they could be extracted from the
+       /// metadata.
+       ///
+       /// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
+       pub fn verify<T: secp256k1::Signing>(
+               &self, key: &ExpandedKey, secp_ctx: &Secp256k1<T>
+       ) -> Result<Option<KeyPair>, ()> {
+               self.contents.inner.offer.verify(&self.bytes, key, secp_ctx)
+       }
+
+       #[cfg(test)]
+       fn as_tlv_stream(&self) -> FullInvoiceRequestTlvStreamRef {
+               let (payer_tlv_stream, offer_tlv_stream, invoice_request_tlv_stream) =
+                       self.contents.as_tlv_stream();
+               let signature_tlv_stream = SignatureTlvStreamRef {
+                       signature: Some(&self.signature),
+               };
+               (payer_tlv_stream, offer_tlv_stream, invoice_request_tlv_stream, signature_tlv_stream)
+       }
+}
+
+impl InvoiceRequestContents {
+       pub(super) fn metadata(&self) -> &[u8] {
+               self.inner.metadata()
+       }
+
+       pub(super) fn derives_keys(&self) -> bool {
+               self.inner.payer.0.derives_keys()
+       }
+
+       pub(super) fn chain(&self) -> ChainHash {
+               self.inner.chain()
+       }
+
+       pub(super) fn payer_id(&self) -> PublicKey {
+               self.payer_id
+       }
+
+       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: self.payer.0.as_bytes(),
+               };
+
+               let offer = self.offer.as_tlv_stream();
+
+               let features = {
+                       if self.features == InvoiceRequestFeatures::empty() { None }
+                       else { Some(&self.features) }
+               };
+
+               let invoice_request = InvoiceRequestTlvStreamRef {
+                       chain: self.chain.as_ref(),
+                       amount: self.amount_msats,
+                       features,
+                       quantity: self.quantity,
+                       payer_id: None,
+                       payer_note: self.payer_note.as_ref(),
+               };
+
+               (payer, offer, invoice_request)
+       }
+}
+
+impl Writeable for InvoiceRequest {
+       fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
+               WithoutLength(&self.bytes).write(writer)
+       }
+}
+
+impl Writeable for InvoiceRequestContents {
+       fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
+               self.as_tlv_stream().write(writer)
+       }
+}
+
+/// Valid type range for invoice_request TLV records.
+pub(super) const INVOICE_REQUEST_TYPES: core::ops::Range<u64> = 80..160;
+
+/// TLV record type for [`InvoiceRequest::payer_id`] and [`Refund::payer_id`].
+///
+/// [`Refund::payer_id`]: crate::offers::refund::Refund::payer_id
+pub(super) const INVOICE_REQUEST_PAYER_ID_TYPE: u64 = 88;
+
+tlv_stream!(InvoiceRequestTlvStream, InvoiceRequestTlvStreamRef, INVOICE_REQUEST_TYPES, {
+       (80, chain: ChainHash),
+       (82, amount: (u64, HighZeroBytesDroppedBigSize)),
+       (84, features: (InvoiceRequestFeatures, WithoutLength)),
+       (86, quantity: (u64, HighZeroBytesDroppedBigSize)),
+       (INVOICE_REQUEST_PAYER_ID_TYPE, payer_id: PublicKey),
+       (89, payer_note: (String, WithoutLength)),
+});
+
+type FullInvoiceRequestTlvStream =
+       (PayerTlvStream, OfferTlvStream, InvoiceRequestTlvStream, SignatureTlvStream);
+
+#[cfg(test)]
+type FullInvoiceRequestTlvStreamRef<'a> = (
+       PayerTlvStreamRef<'a>,
+       OfferTlvStreamRef<'a>,
+       InvoiceRequestTlvStreamRef<'a>,
+       SignatureTlvStreamRef<'a>,
+);
+
+impl SeekReadable for FullInvoiceRequestTlvStream {
+       fn read<R: io::Read + io::Seek>(r: &mut R) -> Result<Self, DecodeError> {
+               let payer = SeekReadable::read(r)?;
+               let offer = SeekReadable::read(r)?;
+               let invoice_request = SeekReadable::read(r)?;
+               let signature = SeekReadable::read(r)?;
+
+               Ok((payer, offer, invoice_request, signature))
+       }
+}
+
+type PartialInvoiceRequestTlvStream = (PayerTlvStream, OfferTlvStream, InvoiceRequestTlvStream);
+
+type PartialInvoiceRequestTlvStreamRef<'a> = (
+       PayerTlvStreamRef<'a>,
+       OfferTlvStreamRef<'a>,
+       InvoiceRequestTlvStreamRef<'a>,
+);
+
+impl TryFrom<Vec<u8>> for InvoiceRequest {
+       type Error = Bolt12ParseError;
+
+       fn try_from(bytes: Vec<u8>) -> Result<Self, Self::Error> {
+               let invoice_request = ParsedMessage::<FullInvoiceRequestTlvStream>::try_from(bytes)?;
+               let ParsedMessage { bytes, tlv_stream } = invoice_request;
+               let (
+                       payer_tlv_stream, offer_tlv_stream, invoice_request_tlv_stream,
+                       SignatureTlvStream { signature },
+               ) = tlv_stream;
+               let contents = InvoiceRequestContents::try_from(
+                       (payer_tlv_stream, offer_tlv_stream, invoice_request_tlv_stream)
+               )?;
+
+               let signature = match signature {
+                       None => return Err(Bolt12ParseError::InvalidSemantics(Bolt12SemanticError::MissingSignature)),
+                       Some(signature) => signature,
+               };
+               merkle::verify_signature(&signature, SIGNATURE_TAG, &bytes, contents.payer_id)?;
+
+               Ok(InvoiceRequest { bytes, contents, signature })
+       }
+}
+
+impl TryFrom<PartialInvoiceRequestTlvStream> for InvoiceRequestContents {
+       type Error = Bolt12SemanticError;
+
+       fn try_from(tlv_stream: PartialInvoiceRequestTlvStream) -> Result<Self, Self::Error> {
+               let (
+                       PayerTlvStream { metadata },
+                       offer_tlv_stream,
+                       InvoiceRequestTlvStream { chain, amount, features, quantity, payer_id, payer_note },
+               ) = tlv_stream;
+
+               let payer = match metadata {
+                       None => return Err(Bolt12SemanticError::MissingPayerMetadata),
+                       Some(metadata) => PayerContents(Metadata::Bytes(metadata)),
+               };
+               let offer = OfferContents::try_from(offer_tlv_stream)?;
+
+               if !offer.supports_chain(chain.unwrap_or_else(|| offer.implied_chain())) {
+                       return Err(Bolt12SemanticError::UnsupportedChain);
+               }
+
+               if offer.amount().is_none() && amount.is_none() {
+                       return Err(Bolt12SemanticError::MissingAmount);
+               }
+
+               offer.check_quantity(quantity)?;
+               offer.check_amount_msats_for_quantity(amount, quantity)?;
+
+               let features = features.unwrap_or_else(InvoiceRequestFeatures::empty);
+
+               let payer_id = match payer_id {
+                       None => return Err(Bolt12SemanticError::MissingPayerId),
+                       Some(payer_id) => payer_id,
+               };
+
+               Ok(InvoiceRequestContents {
+                       inner: InvoiceRequestContentsWithoutPayerId {
+                               payer, offer, chain, amount_msats: amount, features, quantity, payer_note,
+                       },
+                       payer_id,
+               })
+       }
+}
+
+#[cfg(test)]
+mod tests {
+       use super::{InvoiceRequest, InvoiceRequestTlvStreamRef, SIGNATURE_TAG};
+
+       use bitcoin::blockdata::constants::ChainHash;
+       use bitcoin::network::constants::Network;
+       use bitcoin::secp256k1::{KeyPair, Secp256k1, SecretKey, self};
+       use core::convert::{Infallible, TryFrom};
+       use core::num::NonZeroU64;
+       #[cfg(feature = "std")]
+       use core::time::Duration;
+       use crate::sign::KeyMaterial;
+       use crate::ln::features::InvoiceRequestFeatures;
+       use crate::ln::inbound_payment::ExpandedKey;
+       use crate::ln::msgs::{DecodeError, MAX_VALUE_MSAT};
+       use crate::offers::invoice::{Bolt12Invoice, SIGNATURE_TAG as INVOICE_SIGNATURE_TAG};
+       use crate::offers::merkle::{SignError, SignatureTlvStreamRef, TaggedHash, self};
+       use crate::offers::offer::{Amount, OfferBuilder, OfferTlvStreamRef, Quantity};
+       use crate::offers::parse::{Bolt12ParseError, Bolt12SemanticError};
+       use crate::offers::payer::PayerTlvStreamRef;
+       use crate::offers::test_utils::*;
+       use crate::util::ser::{BigSize, Writeable};
+       use crate::util::string::PrintableString;
+
+       #[test]
+       fn builds_invoice_request_with_defaults() {
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .build().unwrap()
+                       .sign(payer_sign).unwrap();
+
+               let mut buffer = Vec::new();
+               invoice_request.write(&mut buffer).unwrap();
+
+               assert_eq!(invoice_request.bytes, buffer.as_slice());
+               assert_eq!(invoice_request.metadata(), &[1; 32]);
+               assert_eq!(invoice_request.chain(), ChainHash::using_genesis_block(Network::Bitcoin));
+               assert_eq!(invoice_request.amount_msats(), None);
+               assert_eq!(invoice_request.features(), &InvoiceRequestFeatures::empty());
+               assert_eq!(invoice_request.quantity(), None);
+               assert_eq!(invoice_request.payer_id(), payer_pubkey());
+               assert_eq!(invoice_request.payer_note(), None);
+               assert!(
+                       merkle::verify_signature(
+                               &invoice_request.signature, SIGNATURE_TAG, &invoice_request.bytes, payer_pubkey()
+                       ).is_ok()
+               );
+
+               assert_eq!(
+                       invoice_request.as_tlv_stream(),
+                       (
+                               PayerTlvStreamRef { metadata: Some(&vec![1; 32]) },
+                               OfferTlvStreamRef {
+                                       chains: None,
+                                       metadata: None,
+                                       currency: None,
+                                       amount: Some(1000),
+                                       description: Some(&String::from("foo")),
+                                       features: None,
+                                       absolute_expiry: None,
+                                       paths: None,
+                                       issuer: None,
+                                       quantity_max: None,
+                                       node_id: Some(&recipient_pubkey()),
+                               },
+                               InvoiceRequestTlvStreamRef {
+                                       chain: None,
+                                       amount: None,
+                                       features: None,
+                                       quantity: None,
+                                       payer_id: Some(&payer_pubkey()),
+                                       payer_note: None,
+                               },
+                               SignatureTlvStreamRef { signature: Some(&invoice_request.signature()) },
+                       ),
+               );
+
+               if let Err(e) = InvoiceRequest::try_from(buffer) {
+                       panic!("error parsing invoice request: {:?}", e);
+               }
+       }
+
+       #[cfg(feature = "std")]
+       #[test]
+       fn builds_invoice_request_from_offer_with_expiration() {
+               let future_expiry = Duration::from_secs(u64::max_value());
+               let past_expiry = Duration::from_secs(0);
+
+               if let Err(e) = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .absolute_expiry(future_expiry)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .build()
+               {
+                       panic!("error building invoice_request: {:?}", e);
+               }
+
+               match OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .absolute_expiry(past_expiry)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .build()
+               {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => assert_eq!(e, Bolt12SemanticError::AlreadyExpired),
+               }
+       }
+
+       #[test]
+       fn builds_invoice_request_with_derived_metadata() {
+               let payer_id = payer_pubkey();
+               let expanded_key = ExpandedKey::new(&KeyMaterial([42; 32]));
+               let entropy = FixedEntropy {};
+               let secp_ctx = Secp256k1::new();
+
+               let offer = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .build().unwrap();
+               let invoice_request = offer
+                       .request_invoice_deriving_metadata(payer_id, &expanded_key, &entropy)
+                       .unwrap()
+                       .build().unwrap()
+                       .sign(payer_sign).unwrap();
+               assert_eq!(invoice_request.payer_id(), payer_pubkey());
+
+               let invoice = invoice_request.respond_with_no_std(payment_paths(), payment_hash(), now())
+                       .unwrap()
+                       .build().unwrap()
+                       .sign(recipient_sign).unwrap();
+               assert!(invoice.verify(&expanded_key, &secp_ctx));
+
+               // Fails verification with altered fields
+               let (
+                       payer_tlv_stream, offer_tlv_stream, mut invoice_request_tlv_stream,
+                       mut invoice_tlv_stream, mut signature_tlv_stream
+               ) = invoice.as_tlv_stream();
+               invoice_request_tlv_stream.amount = Some(2000);
+               invoice_tlv_stream.amount = Some(2000);
+
+               let tlv_stream =
+                       (payer_tlv_stream, offer_tlv_stream, invoice_request_tlv_stream, invoice_tlv_stream);
+               let mut bytes = Vec::new();
+               tlv_stream.write(&mut bytes).unwrap();
+
+               let message = TaggedHash::new(INVOICE_SIGNATURE_TAG, &bytes);
+               let signature = merkle::sign_message(recipient_sign, &message, recipient_pubkey()).unwrap();
+               signature_tlv_stream.signature = Some(&signature);
+
+               let mut encoded_invoice = bytes;
+               signature_tlv_stream.write(&mut encoded_invoice).unwrap();
+
+               let invoice = Bolt12Invoice::try_from(encoded_invoice).unwrap();
+               assert!(!invoice.verify(&expanded_key, &secp_ctx));
+
+               // Fails verification with altered metadata
+               let (
+                       mut payer_tlv_stream, offer_tlv_stream, invoice_request_tlv_stream, invoice_tlv_stream,
+                       mut signature_tlv_stream
+               ) = invoice.as_tlv_stream();
+               let metadata = payer_tlv_stream.metadata.unwrap().iter().copied().rev().collect();
+               payer_tlv_stream.metadata = Some(&metadata);
+
+               let tlv_stream =
+                       (payer_tlv_stream, offer_tlv_stream, invoice_request_tlv_stream, invoice_tlv_stream);
+               let mut bytes = Vec::new();
+               tlv_stream.write(&mut bytes).unwrap();
+
+               let message = TaggedHash::new(INVOICE_SIGNATURE_TAG, &bytes);
+               let signature = merkle::sign_message(recipient_sign, &message, recipient_pubkey()).unwrap();
+               signature_tlv_stream.signature = Some(&signature);
+
+               let mut encoded_invoice = bytes;
+               signature_tlv_stream.write(&mut encoded_invoice).unwrap();
+
+               let invoice = Bolt12Invoice::try_from(encoded_invoice).unwrap();
+               assert!(!invoice.verify(&expanded_key, &secp_ctx));
+       }
+
+       #[test]
+       fn builds_invoice_request_with_derived_payer_id() {
+               let expanded_key = ExpandedKey::new(&KeyMaterial([42; 32]));
+               let entropy = FixedEntropy {};
+               let secp_ctx = Secp256k1::new();
+
+               let offer = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .build().unwrap();
+               let invoice_request = offer
+                       .request_invoice_deriving_payer_id(&expanded_key, &entropy, &secp_ctx)
+                       .unwrap()
+                       .build_and_sign()
+                       .unwrap();
+
+               let invoice = invoice_request.respond_with_no_std(payment_paths(), payment_hash(), now())
+                       .unwrap()
+                       .build().unwrap()
+                       .sign(recipient_sign).unwrap();
+               assert!(invoice.verify(&expanded_key, &secp_ctx));
+
+               // Fails verification with altered fields
+               let (
+                       payer_tlv_stream, offer_tlv_stream, mut invoice_request_tlv_stream,
+                       mut invoice_tlv_stream, mut signature_tlv_stream
+               ) = invoice.as_tlv_stream();
+               invoice_request_tlv_stream.amount = Some(2000);
+               invoice_tlv_stream.amount = Some(2000);
+
+               let tlv_stream =
+                       (payer_tlv_stream, offer_tlv_stream, invoice_request_tlv_stream, invoice_tlv_stream);
+               let mut bytes = Vec::new();
+               tlv_stream.write(&mut bytes).unwrap();
+
+               let message = TaggedHash::new(INVOICE_SIGNATURE_TAG, &bytes);
+               let signature = merkle::sign_message(recipient_sign, &message, recipient_pubkey()).unwrap();
+               signature_tlv_stream.signature = Some(&signature);
+
+               let mut encoded_invoice = bytes;
+               signature_tlv_stream.write(&mut encoded_invoice).unwrap();
+
+               let invoice = Bolt12Invoice::try_from(encoded_invoice).unwrap();
+               assert!(!invoice.verify(&expanded_key, &secp_ctx));
+
+               // Fails verification with altered payer id
+               let (
+                       payer_tlv_stream, offer_tlv_stream, mut invoice_request_tlv_stream, invoice_tlv_stream,
+                       mut signature_tlv_stream
+               ) = invoice.as_tlv_stream();
+               let payer_id = pubkey(1);
+               invoice_request_tlv_stream.payer_id = Some(&payer_id);
+
+               let tlv_stream =
+                       (payer_tlv_stream, offer_tlv_stream, invoice_request_tlv_stream, invoice_tlv_stream);
+               let mut bytes = Vec::new();
+               tlv_stream.write(&mut bytes).unwrap();
+
+               let message = TaggedHash::new(INVOICE_SIGNATURE_TAG, &bytes);
+               let signature = merkle::sign_message(recipient_sign, &message, recipient_pubkey()).unwrap();
+               signature_tlv_stream.signature = Some(&signature);
+
+               let mut encoded_invoice = bytes;
+               signature_tlv_stream.write(&mut encoded_invoice).unwrap();
+
+               let invoice = Bolt12Invoice::try_from(encoded_invoice).unwrap();
+               assert!(!invoice.verify(&expanded_key, &secp_ctx));
+       }
+
+       #[test]
+       fn builds_invoice_request_with_chain() {
+               let mainnet = ChainHash::using_genesis_block(Network::Bitcoin);
+               let testnet = ChainHash::using_genesis_block(Network::Testnet);
+
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .chain(Network::Bitcoin).unwrap()
+                       .build().unwrap()
+                       .sign(payer_sign).unwrap();
+               let (_, _, tlv_stream, _) = invoice_request.as_tlv_stream();
+               assert_eq!(invoice_request.chain(), mainnet);
+               assert_eq!(tlv_stream.chain, None);
+
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .chain(Network::Testnet)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .chain(Network::Testnet).unwrap()
+                       .build().unwrap()
+                       .sign(payer_sign).unwrap();
+               let (_, _, tlv_stream, _) = invoice_request.as_tlv_stream();
+               assert_eq!(invoice_request.chain(), testnet);
+               assert_eq!(tlv_stream.chain, Some(&testnet));
+
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .chain(Network::Bitcoin)
+                       .chain(Network::Testnet)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .chain(Network::Bitcoin).unwrap()
+                       .build().unwrap()
+                       .sign(payer_sign).unwrap();
+               let (_, _, tlv_stream, _) = invoice_request.as_tlv_stream();
+               assert_eq!(invoice_request.chain(), mainnet);
+               assert_eq!(tlv_stream.chain, None);
+
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .chain(Network::Bitcoin)
+                       .chain(Network::Testnet)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .chain(Network::Bitcoin).unwrap()
+                       .chain(Network::Testnet).unwrap()
+                       .build().unwrap()
+                       .sign(payer_sign).unwrap();
+               let (_, _, tlv_stream, _) = invoice_request.as_tlv_stream();
+               assert_eq!(invoice_request.chain(), testnet);
+               assert_eq!(tlv_stream.chain, Some(&testnet));
+
+               match OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .chain(Network::Testnet)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .chain(Network::Bitcoin)
+               {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => assert_eq!(e, Bolt12SemanticError::UnsupportedChain),
+               }
+
+               match OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .chain(Network::Testnet)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .build()
+               {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => assert_eq!(e, Bolt12SemanticError::UnsupportedChain),
+               }
+       }
+
+       #[test]
+       fn builds_invoice_request_with_amount() {
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .amount_msats(1000).unwrap()
+                       .build().unwrap()
+                       .sign(payer_sign).unwrap();
+               let (_, _, tlv_stream, _) = invoice_request.as_tlv_stream();
+               assert_eq!(invoice_request.amount_msats(), Some(1000));
+               assert_eq!(tlv_stream.amount, Some(1000));
+
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .amount_msats(1001).unwrap()
+                       .amount_msats(1000).unwrap()
+                       .build().unwrap()
+                       .sign(payer_sign).unwrap();
+               let (_, _, tlv_stream, _) = invoice_request.as_tlv_stream();
+               assert_eq!(invoice_request.amount_msats(), Some(1000));
+               assert_eq!(tlv_stream.amount, Some(1000));
+
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .amount_msats(1001).unwrap()
+                       .build().unwrap()
+                       .sign(payer_sign).unwrap();
+               let (_, _, tlv_stream, _) = invoice_request.as_tlv_stream();
+               assert_eq!(invoice_request.amount_msats(), Some(1001));
+               assert_eq!(tlv_stream.amount, Some(1001));
+
+               match OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .amount_msats(999)
+               {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => assert_eq!(e, Bolt12SemanticError::InsufficientAmount),
+               }
+
+               match OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .supported_quantity(Quantity::Unbounded)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .quantity(2).unwrap()
+                       .amount_msats(1000)
+               {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => assert_eq!(e, Bolt12SemanticError::InsufficientAmount),
+               }
+
+               match OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .amount_msats(MAX_VALUE_MSAT + 1)
+               {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => assert_eq!(e, Bolt12SemanticError::InvalidAmount),
+               }
+
+               match OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .supported_quantity(Quantity::Unbounded)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .amount_msats(1000).unwrap()
+                       .quantity(2).unwrap()
+                       .build()
+               {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => assert_eq!(e, Bolt12SemanticError::InsufficientAmount),
+               }
+
+               match OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .build()
+               {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => assert_eq!(e, Bolt12SemanticError::MissingAmount),
+               }
+
+               match OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .supported_quantity(Quantity::Unbounded)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .quantity(u64::max_value()).unwrap()
+                       .build()
+               {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => assert_eq!(e, Bolt12SemanticError::InvalidAmount),
+               }
+       }
+
+       #[test]
+       fn builds_invoice_request_with_features() {
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .features_unchecked(InvoiceRequestFeatures::unknown())
+                       .build().unwrap()
+                       .sign(payer_sign).unwrap();
+               let (_, _, tlv_stream, _) = invoice_request.as_tlv_stream();
+               assert_eq!(invoice_request.features(), &InvoiceRequestFeatures::unknown());
+               assert_eq!(tlv_stream.features, Some(&InvoiceRequestFeatures::unknown()));
+
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .features_unchecked(InvoiceRequestFeatures::unknown())
+                       .features_unchecked(InvoiceRequestFeatures::empty())
+                       .build().unwrap()
+                       .sign(payer_sign).unwrap();
+               let (_, _, tlv_stream, _) = invoice_request.as_tlv_stream();
+               assert_eq!(invoice_request.features(), &InvoiceRequestFeatures::empty());
+               assert_eq!(tlv_stream.features, None);
+       }
+
+       #[test]
+       fn builds_invoice_request_with_quantity() {
+               let one = NonZeroU64::new(1).unwrap();
+               let ten = NonZeroU64::new(10).unwrap();
+
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .supported_quantity(Quantity::One)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .build().unwrap()
+                       .sign(payer_sign).unwrap();
+               let (_, _, tlv_stream, _) = invoice_request.as_tlv_stream();
+               assert_eq!(invoice_request.quantity(), None);
+               assert_eq!(tlv_stream.quantity, None);
+
+               match OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .supported_quantity(Quantity::One)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .amount_msats(2_000).unwrap()
+                       .quantity(2)
+               {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => assert_eq!(e, Bolt12SemanticError::UnexpectedQuantity),
+               }
+
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .supported_quantity(Quantity::Bounded(ten))
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .amount_msats(10_000).unwrap()
+                       .quantity(10).unwrap()
+                       .build().unwrap()
+                       .sign(payer_sign).unwrap();
+               let (_, _, tlv_stream, _) = invoice_request.as_tlv_stream();
+               assert_eq!(invoice_request.amount_msats(), Some(10_000));
+               assert_eq!(tlv_stream.amount, Some(10_000));
+
+               match OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .supported_quantity(Quantity::Bounded(ten))
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .amount_msats(11_000).unwrap()
+                       .quantity(11)
+               {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => assert_eq!(e, Bolt12SemanticError::InvalidQuantity),
+               }
+
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .supported_quantity(Quantity::Unbounded)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .amount_msats(2_000).unwrap()
+                       .quantity(2).unwrap()
+                       .build().unwrap()
+                       .sign(payer_sign).unwrap();
+               let (_, _, tlv_stream, _) = invoice_request.as_tlv_stream();
+               assert_eq!(invoice_request.amount_msats(), Some(2_000));
+               assert_eq!(tlv_stream.amount, Some(2_000));
+
+               match OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .supported_quantity(Quantity::Unbounded)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .build()
+               {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => assert_eq!(e, Bolt12SemanticError::MissingQuantity),
+               }
+
+               match OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .supported_quantity(Quantity::Bounded(one))
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .build()
+               {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => assert_eq!(e, Bolt12SemanticError::MissingQuantity),
+               }
+       }
+
+       #[test]
+       fn builds_invoice_request_with_payer_note() {
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .payer_note("bar".into())
+                       .build().unwrap()
+                       .sign(payer_sign).unwrap();
+               let (_, _, tlv_stream, _) = invoice_request.as_tlv_stream();
+               assert_eq!(invoice_request.payer_note(), Some(PrintableString("bar")));
+               assert_eq!(tlv_stream.payer_note, Some(&String::from("bar")));
+
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .payer_note("bar".into())
+                       .payer_note("baz".into())
+                       .build().unwrap()
+                       .sign(payer_sign).unwrap();
+               let (_, _, tlv_stream, _) = invoice_request.as_tlv_stream();
+               assert_eq!(invoice_request.payer_note(), Some(PrintableString("baz")));
+               assert_eq!(tlv_stream.payer_note, Some(&String::from("baz")));
+       }
+
+       #[test]
+       fn fails_signing_invoice_request() {
+               match OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .build().unwrap()
+                       .sign(|_| Err(()))
+               {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => assert_eq!(e, SignError::Signing(())),
+               }
+
+               match OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .build().unwrap()
+                       .sign(recipient_sign)
+               {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => assert_eq!(e, SignError::Verification(secp256k1::Error::InvalidSignature)),
+               }
+       }
+
+       #[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, Bolt12SemanticError::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![1; 32], payer_pubkey()).unwrap()
+                       .build().unwrap()
+                       .sign(payer_sign).unwrap();
+
+               let mut buffer = Vec::new();
+               invoice_request.write(&mut buffer).unwrap();
+
+               if let Err(e) = InvoiceRequest::try_from(buffer) {
+                       panic!("error parsing invoice_request: {:?}", e);
+               }
+       }
+
+       #[test]
+       fn parses_invoice_request_with_chain() {
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .chain(Network::Bitcoin).unwrap()
+                       .build().unwrap()
+                       .sign(payer_sign).unwrap();
+
+               let mut buffer = Vec::new();
+               invoice_request.write(&mut buffer).unwrap();
+
+               if let Err(e) = InvoiceRequest::try_from(buffer) {
+                       panic!("error parsing invoice_request: {:?}", e);
+               }
+
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .chain_unchecked(Network::Testnet)
+                       .build_unchecked()
+                       .sign(payer_sign).unwrap();
+
+               let mut buffer = Vec::new();
+               invoice_request.write(&mut buffer).unwrap();
+
+               match InvoiceRequest::try_from(buffer) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => assert_eq!(e, Bolt12ParseError::InvalidSemantics(Bolt12SemanticError::UnsupportedChain)),
+               }
+       }
+
+       #[test]
+       fn parses_invoice_request_with_amount() {
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .build().unwrap()
+                       .sign(payer_sign).unwrap();
+
+               let mut buffer = Vec::new();
+               invoice_request.write(&mut buffer).unwrap();
+
+               if let Err(e) = InvoiceRequest::try_from(buffer) {
+                       panic!("error parsing invoice_request: {:?}", e);
+               }
+
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .amount_msats(1000).unwrap()
+                       .build().unwrap()
+                       .sign(payer_sign).unwrap();
+
+               let mut buffer = Vec::new();
+               invoice_request.write(&mut buffer).unwrap();
+
+               if let Err(e) = InvoiceRequest::try_from(buffer) {
+                       panic!("error parsing invoice_request: {:?}", e);
+               }
+
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .build_unchecked()
+                       .sign(payer_sign).unwrap();
+
+               let mut buffer = Vec::new();
+               invoice_request.write(&mut buffer).unwrap();
+
+               match InvoiceRequest::try_from(buffer) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => assert_eq!(e, Bolt12ParseError::InvalidSemantics(Bolt12SemanticError::MissingAmount)),
+               }
+
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .amount_msats_unchecked(999)
+                       .build_unchecked()
+                       .sign(payer_sign).unwrap();
+
+               let mut buffer = Vec::new();
+               invoice_request.write(&mut buffer).unwrap();
+
+               match InvoiceRequest::try_from(buffer) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => assert_eq!(e, Bolt12ParseError::InvalidSemantics(Bolt12SemanticError::InsufficientAmount)),
+               }
+
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount(Amount::Currency { iso4217_code: *b"USD", amount: 1000 })
+                       .build_unchecked()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .build_unchecked()
+                       .sign(payer_sign).unwrap();
+
+               let mut buffer = Vec::new();
+               invoice_request.write(&mut buffer).unwrap();
+
+               match InvoiceRequest::try_from(buffer) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => {
+                               assert_eq!(e, Bolt12ParseError::InvalidSemantics(Bolt12SemanticError::UnsupportedCurrency));
+                       },
+               }
+
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .supported_quantity(Quantity::Unbounded)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .quantity(u64::max_value()).unwrap()
+                       .build_unchecked()
+                       .sign(payer_sign).unwrap();
+
+               let mut buffer = Vec::new();
+               invoice_request.write(&mut buffer).unwrap();
+
+               match InvoiceRequest::try_from(buffer) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => assert_eq!(e, Bolt12ParseError::InvalidSemantics(Bolt12SemanticError::InvalidAmount)),
+               }
+       }
+
+       #[test]
+       fn parses_invoice_request_with_quantity() {
+               let one = NonZeroU64::new(1).unwrap();
+               let ten = NonZeroU64::new(10).unwrap();
+
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .supported_quantity(Quantity::One)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .build().unwrap()
+                       .sign(payer_sign).unwrap();
+
+               let mut buffer = Vec::new();
+               invoice_request.write(&mut buffer).unwrap();
+
+               if let Err(e) = InvoiceRequest::try_from(buffer) {
+                       panic!("error parsing invoice_request: {:?}", e);
+               }
+
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .supported_quantity(Quantity::One)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .amount_msats(2_000).unwrap()
+                       .quantity_unchecked(2)
+                       .build_unchecked()
+                       .sign(payer_sign).unwrap();
+
+               let mut buffer = Vec::new();
+               invoice_request.write(&mut buffer).unwrap();
+
+               match InvoiceRequest::try_from(buffer) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => {
+                               assert_eq!(e, Bolt12ParseError::InvalidSemantics(Bolt12SemanticError::UnexpectedQuantity));
+                       },
+               }
+
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .supported_quantity(Quantity::Bounded(ten))
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .amount_msats(10_000).unwrap()
+                       .quantity(10).unwrap()
+                       .build().unwrap()
+                       .sign(payer_sign).unwrap();
+
+               let mut buffer = Vec::new();
+               invoice_request.write(&mut buffer).unwrap();
+
+               if let Err(e) = InvoiceRequest::try_from(buffer) {
+                       panic!("error parsing invoice_request: {:?}", e);
+               }
+
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .supported_quantity(Quantity::Bounded(ten))
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .amount_msats(11_000).unwrap()
+                       .quantity_unchecked(11)
+                       .build_unchecked()
+                       .sign(payer_sign).unwrap();
+
+               let mut buffer = Vec::new();
+               invoice_request.write(&mut buffer).unwrap();
+
+               match InvoiceRequest::try_from(buffer) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => assert_eq!(e, Bolt12ParseError::InvalidSemantics(Bolt12SemanticError::InvalidQuantity)),
+               }
+
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .supported_quantity(Quantity::Unbounded)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .amount_msats(2_000).unwrap()
+                       .quantity(2).unwrap()
+                       .build().unwrap()
+                       .sign(payer_sign).unwrap();
+
+               let mut buffer = Vec::new();
+               invoice_request.write(&mut buffer).unwrap();
+
+               if let Err(e) = InvoiceRequest::try_from(buffer) {
+                       panic!("error parsing invoice_request: {:?}", e);
+               }
+
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .supported_quantity(Quantity::Unbounded)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .build_unchecked()
+                       .sign(payer_sign).unwrap();
+
+               let mut buffer = Vec::new();
+               invoice_request.write(&mut buffer).unwrap();
+
+               match InvoiceRequest::try_from(buffer) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => assert_eq!(e, Bolt12ParseError::InvalidSemantics(Bolt12SemanticError::MissingQuantity)),
+               }
+
+               let invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .supported_quantity(Quantity::Bounded(one))
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .build_unchecked()
+                       .sign(payer_sign).unwrap();
+
+               let mut buffer = Vec::new();
+               invoice_request.write(&mut buffer).unwrap();
+
+               match InvoiceRequest::try_from(buffer) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => assert_eq!(e, Bolt12ParseError::InvalidSemantics(Bolt12SemanticError::MissingQuantity)),
+               }
+       }
+
+       #[test]
+       fn fails_parsing_invoice_request_without_metadata() {
+               let offer = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .build().unwrap();
+               let unsigned_invoice_request = offer.request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .build().unwrap();
+               let mut tlv_stream = unsigned_invoice_request.invoice_request.as_tlv_stream();
+               tlv_stream.0.metadata = None;
+
+               let mut buffer = Vec::new();
+               tlv_stream.write(&mut buffer).unwrap();
+
+               match InvoiceRequest::try_from(buffer) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => {
+                               assert_eq!(e, Bolt12ParseError::InvalidSemantics(Bolt12SemanticError::MissingPayerMetadata));
+                       },
+               }
+       }
+
+       #[test]
+       fn fails_parsing_invoice_request_without_payer_id() {
+               let offer = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .build().unwrap();
+               let unsigned_invoice_request = offer.request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .build().unwrap();
+               let mut tlv_stream = unsigned_invoice_request.invoice_request.as_tlv_stream();
+               tlv_stream.2.payer_id = None;
+
+               let mut buffer = Vec::new();
+               tlv_stream.write(&mut buffer).unwrap();
+
+               match InvoiceRequest::try_from(buffer) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => assert_eq!(e, Bolt12ParseError::InvalidSemantics(Bolt12SemanticError::MissingPayerId)),
+               }
+       }
+
+       #[test]
+       fn fails_parsing_invoice_request_without_node_id() {
+               let offer = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .build().unwrap();
+               let unsigned_invoice_request = offer.request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .build().unwrap();
+               let mut tlv_stream = unsigned_invoice_request.invoice_request.as_tlv_stream();
+               tlv_stream.1.node_id = None;
+
+               let mut buffer = Vec::new();
+               tlv_stream.write(&mut buffer).unwrap();
+
+               match InvoiceRequest::try_from(buffer) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => {
+                               assert_eq!(e, Bolt12ParseError::InvalidSemantics(Bolt12SemanticError::MissingSigningPubkey));
+                       },
+               }
+       }
+
+       #[test]
+       fn fails_parsing_invoice_request_without_signature() {
+               let mut buffer = Vec::new();
+               OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .build().unwrap()
+                       .invoice_request
+                       .write(&mut buffer).unwrap();
+
+               match InvoiceRequest::try_from(buffer) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => assert_eq!(e, Bolt12ParseError::InvalidSemantics(Bolt12SemanticError::MissingSignature)),
+               }
+       }
+
+       #[test]
+       fn fails_parsing_invoice_request_with_invalid_signature() {
+               let mut invoice_request = OfferBuilder::new("foo".into(), recipient_pubkey())
+                       .amount_msats(1000)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], payer_pubkey()).unwrap()
+                       .build().unwrap()
+                       .sign(payer_sign).unwrap();
+               let last_signature_byte = invoice_request.bytes.last_mut().unwrap();
+               *last_signature_byte = last_signature_byte.wrapping_add(1);
+
+               let mut buffer = Vec::new();
+               invoice_request.write(&mut buffer).unwrap();
+
+               match InvoiceRequest::try_from(buffer) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => {
+                               assert_eq!(e, Bolt12ParseError::InvalidSignature(secp256k1::Error::InvalidSignature));
+                       },
+               }
+       }
+
+       #[test]
+       fn fails_parsing_invoice_request_with_extra_tlv_records() {
+               let secp_ctx = Secp256k1::new();
+               let keys = KeyPair::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32]).unwrap());
+               let invoice_request = OfferBuilder::new("foo".into(), keys.public_key())
+                       .amount_msats(1000)
+                       .build().unwrap()
+                       .request_invoice(vec![1; 32], keys.public_key()).unwrap()
+                       .build().unwrap()
+                       .sign::<_, Infallible>(
+                               |message| Ok(secp_ctx.sign_schnorr_no_aux_rand(message.as_ref().as_digest(), &keys))
+                       )
+                       .unwrap();
+
+               let mut encoded_invoice_request = Vec::new();
+               invoice_request.write(&mut encoded_invoice_request).unwrap();
+               BigSize(1002).write(&mut encoded_invoice_request).unwrap();
+               BigSize(32).write(&mut encoded_invoice_request).unwrap();
+               [42u8; 32].write(&mut encoded_invoice_request).unwrap();
+
+               match InvoiceRequest::try_from(encoded_invoice_request) {
+                       Ok(_) => panic!("expected error"),
+                       Err(e) => assert_eq!(e, Bolt12ParseError::Decode(DecodeError::InvalidValue)),
+               }
+       }
 }