Use `crate::prelude::*` rather than specific imports
[rust-lightning] / lightning / src / ln / inbound_payment.rs
index 8ed77e5a615afe44e352d2fc5c12a0186c9bcc50..f27d8aab1195284a0a03c74e9af2e093e8482a65 100644 (file)
@@ -9,24 +9,25 @@
 
 //! Utilities to generate inbound payment information in service of invoice creation.
 
-use alloc::string::ToString;
 use bitcoin::hashes::{Hash, HashEngine};
 use bitcoin::hashes::cmp::fixed_time_eq;
 use bitcoin::hashes::hmac::{Hmac, HmacEngine};
 use bitcoin::hashes::sha256::Hash as Sha256;
-use chain::keysinterface::{KeyMaterial, KeysInterface, Sign};
-use ln::{PaymentHash, PaymentPreimage, PaymentSecret};
-use ln::msgs;
-use ln::msgs::MAX_VALUE_MSAT;
-use util::chacha20::ChaCha20;
-use util::crypto::hkdf_extract_expand_thrice;
-use util::errors::APIError;
-use util::logger::Logger;
-
-use core::convert::TryInto;
+use crate::sign::{KeyMaterial, EntropySource};
+use crate::ln::{PaymentHash, PaymentPreimage, PaymentSecret};
+use crate::ln::msgs;
+use crate::ln::msgs::MAX_VALUE_MSAT;
+use crate::crypto::chacha20::ChaCha20;
+use crate::crypto::utils::hkdf_extract_expand_5x;
+use crate::util::errors::APIError;
+use crate::util::logger::Logger;
+
+#[allow(unused_imports)]
+use crate::prelude::*;
+
 use core::ops::Deref;
 
-const IV_LEN: usize = 16;
+pub(crate) const IV_LEN: usize = 16;
 const METADATA_LEN: usize = 16;
 const METADATA_KEY_LEN: usize = 32;
 const AMT_MSAT_LEN: usize = 8;
@@ -35,9 +36,9 @@ const AMT_MSAT_LEN: usize = 8;
 const METHOD_TYPE_OFFSET: usize = 5;
 
 /// A set of keys that were HKDF-expanded from an initial call to
-/// [`KeysInterface::get_inbound_payment_key_material`].
+/// [`NodeSigner::get_inbound_payment_key_material`].
 ///
-/// [`KeysInterface::get_inbound_payment_key_material`]: crate::chain::keysinterface::KeysInterface::get_inbound_payment_key_material
+/// [`NodeSigner::get_inbound_payment_key_material`]: crate::sign::NodeSigner::get_inbound_payment_key_material
 pub struct ExpandedKey {
        /// The key used to encrypt the bytes containing the payment metadata (i.e. the amount and
        /// expiry, included for payment verification on decryption).
@@ -48,6 +49,10 @@ pub struct ExpandedKey {
        /// The key used to authenticate a user-provided payment hash and metadata as previously
        /// registered with LDK.
        user_pmt_hash_key: [u8; 32],
+       /// The base key used to derive signing keys and authenticate messages for BOLT 12 Offers.
+       offers_base_key: [u8; 32],
+       /// The key used to encrypt message metadata for BOLT 12 Offers.
+       offers_encryption_key: [u8; 32],
 }
 
 impl ExpandedKey {
@@ -55,19 +60,94 @@ impl ExpandedKey {
        ///
        /// It is recommended to cache this value and not regenerate it for each new inbound payment.
        pub fn new(key_material: &KeyMaterial) -> ExpandedKey {
-               let (metadata_key, ldk_pmt_hash_key, user_pmt_hash_key) =
-                       hkdf_extract_expand_thrice(b"LDK Inbound Payment Key Expansion", &key_material.0);
+               let (
+                       metadata_key,
+                       ldk_pmt_hash_key,
+                       user_pmt_hash_key,
+                       offers_base_key,
+                       offers_encryption_key,
+               ) = hkdf_extract_expand_5x(b"LDK Inbound Payment Key Expansion", &key_material.0);
                Self {
                        metadata_key,
                        ldk_pmt_hash_key,
                        user_pmt_hash_key,
+                       offers_base_key,
+                       offers_encryption_key,
+               }
+       }
+
+       /// Returns an [`HmacEngine`] used to construct [`Offer::metadata`].
+       ///
+       /// [`Offer::metadata`]: crate::offers::offer::Offer::metadata
+       pub(crate) fn hmac_for_offer(
+               &self, nonce: Nonce, iv_bytes: &[u8; IV_LEN]
+       ) -> HmacEngine<Sha256> {
+               let mut hmac = HmacEngine::<Sha256>::new(&self.offers_base_key);
+               hmac.input(iv_bytes);
+               hmac.input(&nonce.0);
+               hmac
+       }
+
+       /// Encrypts or decrypts the given `bytes`. Used for data included in an offer message's
+       /// metadata (e.g., payment id).
+       pub(crate) fn crypt_for_offer(&self, mut bytes: [u8; 32], nonce: Nonce) -> [u8; 32] {
+               ChaCha20::encrypt_single_block_in_place(&self.offers_encryption_key, &nonce.0, &mut bytes);
+               bytes
+       }
+}
+
+/// A 128-bit number used only once.
+///
+/// Needed when constructing [`Offer::metadata`] and deriving [`Offer::signing_pubkey`] from
+/// [`ExpandedKey`]. Must not be reused for any other derivation without first hashing.
+///
+/// [`Offer::metadata`]: crate::offers::offer::Offer::metadata
+/// [`Offer::signing_pubkey`]: crate::offers::offer::Offer::signing_pubkey
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub(crate) struct Nonce(pub(crate) [u8; Self::LENGTH]);
+
+impl Nonce {
+       /// Number of bytes in the nonce.
+       pub const LENGTH: usize = 16;
+
+       /// Creates a `Nonce` from the given [`EntropySource`].
+       pub fn from_entropy_source<ES: Deref>(entropy_source: ES) -> Self
+       where
+               ES::Target: EntropySource,
+       {
+               let mut bytes = [0u8; Self::LENGTH];
+               let rand_bytes = entropy_source.get_secure_random_bytes();
+               bytes.copy_from_slice(&rand_bytes[..Self::LENGTH]);
+
+               Nonce(bytes)
+       }
+
+       /// Returns a slice of the underlying bytes of size [`Nonce::LENGTH`].
+       pub fn as_slice(&self) -> &[u8] {
+               &self.0
+       }
+}
+
+impl TryFrom<&[u8]> for Nonce {
+       type Error = ();
+
+       fn try_from(bytes: &[u8]) -> Result<Self, ()> {
+               if bytes.len() != Self::LENGTH {
+                       return Err(());
                }
+
+               let mut copied_bytes = [0u8; Self::LENGTH];
+               copied_bytes.copy_from_slice(bytes);
+
+               Ok(Self(copied_bytes))
        }
 }
 
 enum Method {
        LdkPaymentHash = 0,
        UserPaymentHash = 1,
+       LdkPaymentHashCustomFinalCltv = 2,
+       UserPaymentHashCustomFinalCltv = 3,
 }
 
 impl Method {
@@ -75,37 +155,54 @@ impl Method {
                match bits {
                        bits if bits == Method::LdkPaymentHash as u8 => Ok(Method::LdkPaymentHash),
                        bits if bits == Method::UserPaymentHash as u8 => Ok(Method::UserPaymentHash),
+                       bits if bits == Method::LdkPaymentHashCustomFinalCltv as u8 => Ok(Method::LdkPaymentHashCustomFinalCltv),
+                       bits if bits == Method::UserPaymentHashCustomFinalCltv as u8 => Ok(Method::UserPaymentHashCustomFinalCltv),
                        unknown => Err(unknown),
                }
        }
 }
 
+fn min_final_cltv_expiry_delta_from_metadata(bytes: [u8; METADATA_LEN]) -> u16 {
+       let expiry_bytes = &bytes[AMT_MSAT_LEN..];
+       u16::from_be_bytes([expiry_bytes[0], expiry_bytes[1]])
+}
+
 /// Equivalent to [`crate::ln::channelmanager::ChannelManager::create_inbound_payment`], but no
 /// `ChannelManager` is required. Useful for generating invoices for [phantom node payments] without
 /// a `ChannelManager`.
 ///
-/// `keys` is generated by calling [`KeysInterface::get_inbound_payment_key_material`] and then
+/// `keys` is generated by calling [`NodeSigner::get_inbound_payment_key_material`] and then
 /// calling [`ExpandedKey::new`] with its result. It is recommended to cache this value and not
 /// regenerate it for each new inbound payment.
 ///
 /// `current_time` is a Unix timestamp representing the current time.
 ///
-/// [phantom node payments]: crate::chain::keysinterface::PhantomKeysManager
-pub fn create<Signer: Sign, K: Deref>(keys: &ExpandedKey, min_value_msat: Option<u64>, invoice_expiry_delta_secs: u32, keys_manager: &K, current_time: u64) -> Result<(PaymentHash, PaymentSecret), ()>
-       where K::Target: KeysInterface<Signer = Signer>
+/// Note that if `min_final_cltv_expiry_delta` is set to some value, then the payment will not be receivable
+/// on versions of LDK prior to 0.0.114.
+///
+/// [phantom node payments]: crate::sign::PhantomKeysManager
+/// [`NodeSigner::get_inbound_payment_key_material`]: crate::sign::NodeSigner::get_inbound_payment_key_material
+pub fn create<ES: Deref>(keys: &ExpandedKey, min_value_msat: Option<u64>,
+       invoice_expiry_delta_secs: u32, entropy_source: &ES, current_time: u64,
+       min_final_cltv_expiry_delta: Option<u16>) -> Result<(PaymentHash, PaymentSecret), ()>
+       where ES::Target: EntropySource
 {
-       let metadata_bytes = construct_metadata_bytes(min_value_msat, Method::LdkPaymentHash, invoice_expiry_delta_secs, current_time)?;
+       let metadata_bytes = construct_metadata_bytes(min_value_msat, if min_final_cltv_expiry_delta.is_some() {
+                       Method::LdkPaymentHashCustomFinalCltv
+               } else {
+                       Method::LdkPaymentHash
+               }, invoice_expiry_delta_secs, current_time, min_final_cltv_expiry_delta)?;
 
        let mut iv_bytes = [0 as u8; IV_LEN];
-       let rand_bytes = keys_manager.get_secure_random_bytes();
+       let rand_bytes = entropy_source.get_secure_random_bytes();
        iv_bytes.copy_from_slice(&rand_bytes[..IV_LEN]);
 
        let mut hmac = HmacEngine::<Sha256>::new(&keys.ldk_pmt_hash_key);
        hmac.input(&iv_bytes);
        hmac.input(&metadata_bytes);
-       let payment_preimage_bytes = Hmac::from_engine(hmac).into_inner();
+       let payment_preimage_bytes = Hmac::from_engine(hmac).to_byte_array();
 
-       let ldk_pmt_hash = PaymentHash(Sha256::hash(&payment_preimage_bytes).into_inner());
+       let ldk_pmt_hash = PaymentHash(Sha256::hash(&payment_preimage_bytes).to_byte_array());
        let payment_secret = construct_payment_secret(&iv_bytes, &metadata_bytes, &keys.metadata_key);
        Ok((ldk_pmt_hash, payment_secret))
 }
@@ -116,14 +213,22 @@ pub fn create<Signer: Sign, K: Deref>(keys: &ExpandedKey, min_value_msat: Option
 ///
 /// See [`create`] for information on the `keys` and `current_time` parameters.
 ///
-/// [phantom node payments]: crate::chain::keysinterface::PhantomKeysManager
-pub fn create_from_hash(keys: &ExpandedKey, min_value_msat: Option<u64>, payment_hash: PaymentHash, invoice_expiry_delta_secs: u32, current_time: u64) -> Result<PaymentSecret, ()> {
-       let metadata_bytes = construct_metadata_bytes(min_value_msat, Method::UserPaymentHash, invoice_expiry_delta_secs, current_time)?;
+/// Note that if `min_final_cltv_expiry_delta` is set to some value, then the payment will not be receivable
+/// on versions of LDK prior to 0.0.114.
+///
+/// [phantom node payments]: crate::sign::PhantomKeysManager
+pub fn create_from_hash(keys: &ExpandedKey, min_value_msat: Option<u64>, payment_hash: PaymentHash,
+       invoice_expiry_delta_secs: u32, current_time: u64, min_final_cltv_expiry_delta: Option<u16>) -> Result<PaymentSecret, ()> {
+       let metadata_bytes = construct_metadata_bytes(min_value_msat, if min_final_cltv_expiry_delta.is_some() {
+                       Method::UserPaymentHashCustomFinalCltv
+               } else {
+                       Method::UserPaymentHash
+               }, invoice_expiry_delta_secs, current_time, min_final_cltv_expiry_delta)?;
 
        let mut hmac = HmacEngine::<Sha256>::new(&keys.user_pmt_hash_key);
        hmac.input(&metadata_bytes);
        hmac.input(&payment_hash.0);
-       let hmac_bytes = Hmac::from_engine(hmac).into_inner();
+       let hmac_bytes = Hmac::from_engine(hmac).to_byte_array();
 
        let mut iv_bytes = [0 as u8; IV_LEN];
        iv_bytes.copy_from_slice(&hmac_bytes[..IV_LEN]);
@@ -131,7 +236,8 @@ pub fn create_from_hash(keys: &ExpandedKey, min_value_msat: Option<u64>, payment
        Ok(construct_payment_secret(&iv_bytes, &metadata_bytes, &keys.metadata_key))
 }
 
-fn construct_metadata_bytes(min_value_msat: Option<u64>, payment_type: Method, invoice_expiry_delta_secs: u32, highest_seen_timestamp: u64) -> Result<[u8; METADATA_LEN], ()> {
+fn construct_metadata_bytes(min_value_msat: Option<u64>, payment_type: Method,
+       invoice_expiry_delta_secs: u32, highest_seen_timestamp: u64, min_final_cltv_expiry_delta: Option<u16>) -> Result<[u8; METADATA_LEN], ()> {
        if min_value_msat.is_some() && min_value_msat.unwrap() > MAX_VALUE_MSAT {
                return Err(());
        }
@@ -147,9 +253,27 @@ fn construct_metadata_bytes(min_value_msat: Option<u64>, payment_type: Method, i
        // than two hours in the future.  Thus, we add two hours here as a buffer to ensure we
        // absolutely never fail a payment too early.
        // Note that we assume that received blocks have reasonably up-to-date timestamps.
-       let expiry_bytes = (highest_seen_timestamp + invoice_expiry_delta_secs as u64 + 7200).to_be_bytes();
+       let expiry_timestamp = highest_seen_timestamp + invoice_expiry_delta_secs as u64 + 7200;
+       let mut expiry_bytes = expiry_timestamp.to_be_bytes();
+
+       // `min_value_msat` should fit in (64 bits - 3 payment type bits =) 61 bits as an unsigned integer.
+       // This should leave us with a maximum value greater than the 21M BTC supply cap anyway.
+       if min_value_msat.is_some() && min_value_msat.unwrap() > ((1u64 << 61) - 1) { return Err(()); }
+
+       // `expiry_timestamp` should fit in (64 bits - 2 delta bytes =) 48 bits as an unsigned integer.
+       // Bitcoin's block header timestamps are actually `u32`s, so we're technically already limited to
+       // the much smaller maximum timestamp of `u32::MAX` for now, but we check the u64 `expiry_timestamp`
+       // for future-proofing.
+       if min_final_cltv_expiry_delta.is_some() && expiry_timestamp > ((1u64 << 48) - 1) { return Err(()); }
+
+       if let Some(min_final_cltv_expiry_delta) = min_final_cltv_expiry_delta {
+               let bytes = min_final_cltv_expiry_delta.to_be_bytes();
+               expiry_bytes[0] |= bytes[0];
+               expiry_bytes[1] |= bytes[1];
+       }
 
        let mut metadata_bytes: [u8; METADATA_LEN] = [0; METADATA_LEN];
+
        metadata_bytes[..AMT_MSAT_LEN].copy_from_slice(&min_amt_msat_bytes);
        metadata_bytes[AMT_MSAT_LEN..].copy_from_slice(&expiry_bytes);
 
@@ -161,10 +285,9 @@ fn construct_payment_secret(iv_bytes: &[u8; IV_LEN], metadata_bytes: &[u8; METAD
        let (iv_slice, encrypted_metadata_slice) = payment_secret_bytes.split_at_mut(IV_LEN);
        iv_slice.copy_from_slice(iv_bytes);
 
-       let chacha_block = ChaCha20::get_single_block(metadata_key, iv_bytes);
-       for i in 0..METADATA_LEN {
-               encrypted_metadata_slice[i] = chacha_block[i] ^ metadata_bytes[i];
-       }
+       ChaCha20::encrypt_single_block(
+               metadata_key, iv_bytes, encrypted_metadata_slice, metadata_bytes
+       );
        PaymentSecret(payment_secret_bytes)
 }
 
@@ -174,9 +297,13 @@ fn construct_payment_secret(iv_bytes: &[u8; IV_LEN], metadata_bytes: &[u8; METAD
 /// secret (and, if supplied by LDK, our payment preimage) to include encrypted metadata about the
 /// payment.
 ///
-/// The metadata is constructed as:
+/// For payments without a custom `min_final_cltv_expiry_delta`, the metadata is constructed as:
 ///   payment method (3 bits) || payment amount (8 bytes - 3 bits) || expiry (8 bytes)
-/// and encrypted using a key derived from [`KeysInterface::get_inbound_payment_key_material`].
+///
+/// For payments including a custom `min_final_cltv_expiry_delta`, the metadata is constructed as:
+///   payment method (3 bits) || payment amount (8 bytes - 3 bits) || min_final_cltv_expiry_delta (2 bytes) || expiry (6 bytes)
+///
+/// In both cases the result is then encrypted using a key derived from [`NodeSigner::get_inbound_payment_key_material`].
 ///
 /// Then on payment receipt, we verify in this method that the payment preimage and payment secret
 /// match what was constructed.
@@ -197,74 +324,90 @@ fn construct_payment_secret(iv_bytes: &[u8; IV_LEN], metadata_bytes: &[u8; METAD
 ///
 /// See [`ExpandedKey`] docs for more info on the individual keys used.
 ///
-/// [`KeysInterface::get_inbound_payment_key_material`]: crate::chain::keysinterface::KeysInterface::get_inbound_payment_key_material
+/// [`NodeSigner::get_inbound_payment_key_material`]: crate::sign::NodeSigner::get_inbound_payment_key_material
 /// [`create_inbound_payment`]: crate::ln::channelmanager::ChannelManager::create_inbound_payment
 /// [`create_inbound_payment_for_hash`]: crate::ln::channelmanager::ChannelManager::create_inbound_payment_for_hash
-pub(super) fn verify<L: Deref>(payment_hash: PaymentHash, payment_data: msgs::FinalOnionHopData, highest_seen_timestamp: u64, keys: &ExpandedKey, logger: &L) -> Result<Option<PaymentPreimage>, ()>
+pub(super) fn verify<L: Deref>(payment_hash: PaymentHash, payment_data: &msgs::FinalOnionHopData,
+       highest_seen_timestamp: u64, keys: &ExpandedKey, logger: &L) -> Result<
+       (Option<PaymentPreimage>, Option<u16>), ()>
        where L::Target: Logger
 {
        let (iv_bytes, metadata_bytes) = decrypt_metadata(payment_data.payment_secret, keys);
 
        let payment_type_res = Method::from_bits((metadata_bytes[0] & 0b1110_0000) >> METHOD_TYPE_OFFSET);
        let mut amt_msat_bytes = [0; AMT_MSAT_LEN];
+       let mut expiry_bytes = [0; METADATA_LEN - AMT_MSAT_LEN];
        amt_msat_bytes.copy_from_slice(&metadata_bytes[..AMT_MSAT_LEN]);
+       expiry_bytes.copy_from_slice(&metadata_bytes[AMT_MSAT_LEN..]);
        // Zero out the bits reserved to indicate the payment type.
        amt_msat_bytes[0] &= 0b00011111;
-       let min_amt_msat: u64 = u64::from_be_bytes(amt_msat_bytes.into());
-       let expiry = u64::from_be_bytes(metadata_bytes[AMT_MSAT_LEN..].try_into().unwrap());
+       let mut min_final_cltv_expiry_delta = None;
 
-       // Make sure to check to check the HMAC before doing the other checks below, to mitigate timing
-       // attacks.
+       // Make sure to check the HMAC before doing the other checks below, to mitigate timing attacks.
        let mut payment_preimage = None;
+
        match payment_type_res {
-               Ok(Method::UserPaymentHash) => {
+               Ok(Method::UserPaymentHash) | Ok(Method::UserPaymentHashCustomFinalCltv) => {
                        let mut hmac = HmacEngine::<Sha256>::new(&keys.user_pmt_hash_key);
                        hmac.input(&metadata_bytes[..]);
                        hmac.input(&payment_hash.0);
-                       if !fixed_time_eq(&iv_bytes, &Hmac::from_engine(hmac).into_inner().split_at_mut(IV_LEN).0) {
-                               log_trace!(logger, "Failing HTLC with user-generated payment_hash {}: unexpected payment_secret", log_bytes!(payment_hash.0));
+                       if !fixed_time_eq(&iv_bytes, &Hmac::from_engine(hmac).to_byte_array().split_at_mut(IV_LEN).0) {
+                               log_trace!(logger, "Failing HTLC with user-generated payment_hash {}: unexpected payment_secret", &payment_hash);
                                return Err(())
                        }
                },
-               Ok(Method::LdkPaymentHash) => {
+               Ok(Method::LdkPaymentHash) | Ok(Method::LdkPaymentHashCustomFinalCltv) => {
                        match derive_ldk_payment_preimage(payment_hash, &iv_bytes, &metadata_bytes, keys) {
                                Ok(preimage) => payment_preimage = Some(preimage),
                                Err(bad_preimage_bytes) => {
-                                       log_trace!(logger, "Failing HTLC with payment_hash {} due to mismatching preimage {}", log_bytes!(payment_hash.0), log_bytes!(bad_preimage_bytes));
+                                       log_trace!(logger, "Failing HTLC with payment_hash {} due to mismatching preimage {}", &payment_hash, log_bytes!(bad_preimage_bytes));
                                        return Err(())
                                }
                        }
                },
                Err(unknown_bits) => {
-                       log_trace!(logger, "Failing HTLC with payment hash {} due to unknown payment type {}", log_bytes!(payment_hash.0), unknown_bits);
+                       log_trace!(logger, "Failing HTLC with payment hash {} due to unknown payment type {}", &payment_hash, unknown_bits);
                        return Err(());
                }
        }
 
+       match payment_type_res {
+               Ok(Method::UserPaymentHashCustomFinalCltv) | Ok(Method::LdkPaymentHashCustomFinalCltv) => {
+                       min_final_cltv_expiry_delta = Some(min_final_cltv_expiry_delta_from_metadata(metadata_bytes));
+                       // Zero out first two bytes of expiry reserved for `min_final_cltv_expiry_delta`.
+                       expiry_bytes[0] &= 0;
+                       expiry_bytes[1] &= 0;
+               }
+               _ => {}
+       }
+
+       let min_amt_msat: u64 = u64::from_be_bytes(amt_msat_bytes.into());
+       let expiry = u64::from_be_bytes(expiry_bytes.try_into().unwrap());
+
        if payment_data.total_msat < min_amt_msat {
-               log_trace!(logger, "Failing HTLC with payment_hash {} due to total_msat {} being less than the minimum amount of {} msat", log_bytes!(payment_hash.0), payment_data.total_msat, min_amt_msat);
+               log_trace!(logger, "Failing HTLC with payment_hash {} due to total_msat {} being less than the minimum amount of {} msat", &payment_hash, payment_data.total_msat, min_amt_msat);
                return Err(())
        }
 
        if expiry < highest_seen_timestamp {
-               log_trace!(logger, "Failing HTLC with payment_hash {}: expired payment", log_bytes!(payment_hash.0));
+               log_trace!(logger, "Failing HTLC with payment_hash {}: expired payment", &payment_hash);
                return Err(())
        }
 
-       Ok(payment_preimage)
+       Ok((payment_preimage, min_final_cltv_expiry_delta))
 }
 
 pub(super) fn get_payment_preimage(payment_hash: PaymentHash, payment_secret: PaymentSecret, keys: &ExpandedKey) -> Result<PaymentPreimage, APIError> {
        let (iv_bytes, metadata_bytes) = decrypt_metadata(payment_secret, keys);
 
        match Method::from_bits((metadata_bytes[0] & 0b1110_0000) >> METHOD_TYPE_OFFSET) {
-               Ok(Method::LdkPaymentHash) => {
+               Ok(Method::LdkPaymentHash) | Ok(Method::LdkPaymentHashCustomFinalCltv) => {
                        derive_ldk_payment_preimage(payment_hash, &iv_bytes, &metadata_bytes, keys)
                                .map_err(|bad_preimage_bytes| APIError::APIMisuseError {
-                                       err: format!("Payment hash {} did not match decoded preimage {}", log_bytes!(payment_hash.0), log_bytes!(bad_preimage_bytes))
+                                       err: format!("Payment hash {} did not match decoded preimage {}", &payment_hash, log_bytes!(bad_preimage_bytes))
                                })
                },
-               Ok(Method::UserPaymentHash) => Err(APIError::APIMisuseError {
+               Ok(Method::UserPaymentHash) | Ok(Method::UserPaymentHashCustomFinalCltv) => Err(APIError::APIMisuseError {
                        err: "Expected payment type to be LdkPaymentHash, instead got UserPaymentHash".to_string()
                }),
                Err(other) => Err(APIError::APIMisuseError { err: format!("Unknown payment type: {}", other) }),
@@ -276,11 +419,10 @@ fn decrypt_metadata(payment_secret: PaymentSecret, keys: &ExpandedKey) -> ([u8;
        let (iv_slice, encrypted_metadata_bytes) = payment_secret.0.split_at(IV_LEN);
        iv_bytes.copy_from_slice(iv_slice);
 
-       let chacha_block = ChaCha20::get_single_block(&keys.metadata_key, &iv_bytes);
        let mut metadata_bytes: [u8; METADATA_LEN] = [0; METADATA_LEN];
-       for i in 0..METADATA_LEN {
-               metadata_bytes[i] = chacha_block[i] ^ encrypted_metadata_bytes[i];
-       }
+       ChaCha20::encrypt_single_block(
+               &keys.metadata_key, &iv_bytes, &mut metadata_bytes, encrypted_metadata_bytes
+       );
 
        (iv_bytes, metadata_bytes)
 }
@@ -291,8 +433,8 @@ fn derive_ldk_payment_preimage(payment_hash: PaymentHash, iv_bytes: &[u8; IV_LEN
        let mut hmac = HmacEngine::<Sha256>::new(&keys.ldk_pmt_hash_key);
        hmac.input(iv_bytes);
        hmac.input(metadata_bytes);
-       let decoded_payment_preimage = Hmac::from_engine(hmac).into_inner();
-       if !fixed_time_eq(&payment_hash.0, &Sha256::hash(&decoded_payment_preimage).into_inner()) {
+       let decoded_payment_preimage = Hmac::from_engine(hmac).to_byte_array();
+       if !fixed_time_eq(&payment_hash.0, &Sha256::hash(&decoded_payment_preimage).to_byte_array()) {
                return Err(decoded_payment_preimage);
        }
        return Ok(PaymentPreimage(decoded_payment_preimage))