Validate InputPair to rm SelectionErr::PrevTxOut

Validated pairs will not produce a mismatched TxOut error.

Author: DanGould

payjoin-cli/src/app/mod.rs

@@ -7,9 +7,8 @@ use bitcoin::TxIn;
 use bitcoincore_rpc::bitcoin::Amount;
 use bitcoincore_rpc::RpcApi;
 use payjoin::bitcoin::psbt::Psbt;
-use payjoin::psbt::InputPair;
 use payjoin::send::Sender;
-use payjoin::{bitcoin, PjUri};
+use payjoin::{bitcoin, InputPair, PjUri};
 
 pub mod config;
 use crate::app::config::AppConfig;

payjoin-cli/src/app/v2.rs

@@ -1,4 +1,3 @@
-use std::collections::HashMap;
 use std::str::FromStr;
 use std::sync::Arc;
 

payjoin/src/lib.rs

@@ -38,7 +38,7 @@ pub use crate::ohttp::OhttpKeys;
 pub mod io;
 
 #[cfg(any(feature = "send", feature = "receive"))]
-pub mod psbt;
+pub(crate) mod psbt;
 #[cfg(any(feature = "send", all(feature = "receive", feature = "v2")))]
 mod request;
 #[cfg(any(feature = "send", all(feature = "receive", feature = "v2")))]
@@ -48,5 +48,6 @@ mod uri;
 
 #[cfg(feature = "base64")]
 pub use bitcoin::base64;
+pub use psbt::InputPair;
 pub use uri::{PjParseError, PjUri, PjUriBuilder, Uri, UriExt};
 pub use url::{ParseError, Url};

payjoin/src/psbt.rs

@@ -115,13 +115,32 @@ pub struct InputPair {
 impl InputPair {
     pub fn new(txin: TxIn, psbtin: psbt::Input) -> Result<Self, PsbtInputError> {
         let input_pair = Self { txin, psbtin };
+        // TODO validate and document Input details required for Input Contribution fee estimation
+        // TODO Validate AddressType will return valid AddressType or an error
+        // TODO consider whether or not this should live in receive module since it's a baby of that state machine
         InternalInputPair::from(&input_pair).validate_utxo(true)?;
         Ok(input_pair)
     }
+
+    pub(crate) fn txin(&self) -> &TxIn { &self.txin }
+
+    pub(crate) fn psbtin(&self) -> &psbt::Input { &self.psbtin }
+
+    pub(crate) fn address_type(&self) -> Result<AddressType, AddressTypeError> {
+        let raw = InternalInputPair { txin: &self.txin, psbtin: &self.psbtin };
+        raw.address_type()
+    }
+
+    pub(crate) fn previous_txout(&self) -> TxOut {
+        InternalInputPair::from(self)
+            .previous_txout()
+            .expect("missing UTXO information should have been validated in InputPair::new")
+            .clone()
+    }
 }
 
 #[derive(Clone, Debug)]
-pub(crate) struct InternalInputPair<'a> {
+pub struct InternalInputPair<'a> {
     pub txin: &'a TxIn,
     pub psbtin: &'a psbt::Input,
 }

payjoin/src/receive/error.rs

@@ -260,8 +260,6 @@ pub(crate) enum InternalSelectionError {
     TooManyOutputs,
     /// No selection candidates improve privacy
     NotFound,
-    /// Missing previous txout information
-    PrevTxOut(crate::psbt::PrevTxOutError),
 }
 
 impl fmt::Display for SelectionError {
@@ -274,8 +272,6 @@ impl fmt::Display for SelectionError {
             ),
             InternalSelectionError::NotFound =>
                 write!(f, "No selection candidates improve privacy"),
-            InternalSelectionError::PrevTxOut(e) =>
-                write!(f, "Missing previous txout information: {}", e),
         }
     }
 }
@@ -293,8 +289,6 @@ pub struct InputContributionError(InternalInputContributionError);
 
 #[derive(Debug)]
 pub(crate) enum InternalInputContributionError {
-    /// Missing previous txout information
-    PrevTxOut(crate::psbt::PrevTxOutError),
     /// The address type could not be determined
     AddressType(crate::psbt::AddressTypeError),
     /// The original PSBT has no inputs
@@ -308,8 +302,6 @@ pub(crate) enum InternalInputContributionError {
 impl fmt::Display for InputContributionError {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match &self.0 {
-            InternalInputContributionError::PrevTxOut(e) =>
-                write!(f, "Missing previous txout information: {}", e),
             InternalInputContributionError::AddressType(e) =>
                 write!(f, "The address type could not be determined: {}", e),
             InternalInputContributionError::NoSenderInputs =>

payjoin/src/receive/mod.rs

@@ -47,7 +47,7 @@ use error::{
 };
 use optional_parameters::Params;
 
-use crate::psbt::{InputPair, InternalInputPair, PsbtExt};
+use crate::psbt::{InputPair, PsbtExt};
 
 pub trait Headers {
     fn get_header(&self, key: &str) -> Option<&str>;
@@ -507,16 +507,14 @@ impl WantsInputs {
         let prior_payment_sats = self.payjoin_psbt.unsigned_tx.output[self.change_vout].value;
 
         for input_pair in candidate_inputs {
-            let input_pair = InternalInputPair::from(&input_pair);
-            let candidate_sats =
-                input_pair.previous_txout().map_err(InternalSelectionError::PrevTxOut)?.value;
+            let candidate_sats = input_pair.previous_txout().value;
             let candidate_min_out = min(min_original_out_sats, prior_payment_sats + candidate_sats);
             let candidate_min_in = min(min_original_in_sats, candidate_sats);
 
             if candidate_min_in > candidate_min_out {
                 // The candidate avoids UIH2 but conforms to UIH1: Optimal change heuristic.
                 // It implies the smallest output is the sender's change address.
-                return Ok(InputPair::from(&input_pair));
+                return Ok(input_pair);
             }
         }
 
@@ -555,7 +553,6 @@ impl WantsInputs {
         let mut rng = rand::thread_rng();
         let mut receiver_input_amount = Amount::ZERO;
         for input_pair in inputs.into_iter() {
-            let input_pair = InternalInputPair::from(&input_pair);
             let input_type =
                 input_pair.address_type().map_err(InternalInputContributionError::AddressType)?;
 
@@ -564,16 +561,13 @@ impl WantsInputs {
                 self.check_mixed_input_types(input_type, uniform_sender_input_type)?;
             }
 
-            receiver_input_amount += input_pair
-                .previous_txout()
-                .map_err(InternalInputContributionError::PrevTxOut)?
-                .value;
+            receiver_input_amount += input_pair.previous_txout().value;
             let index = rng.gen_range(0..=self.payjoin_psbt.unsigned_tx.input.len());
-            payjoin_psbt.inputs.insert(index, input_pair.psbtin.clone());
+            payjoin_psbt.inputs.insert(index, input_pair.psbtin().clone());
             payjoin_psbt
                 .unsigned_tx
                 .input
-                .insert(index, TxIn { sequence: original_sequence, ..input_pair.txin.clone() });
+                .insert(index, TxIn { sequence: original_sequence, ..input_pair.txin().clone() });
         }
 
         // Add the receiver change amount to the receiver change output, if applicable

payjoin/src/receive/v2/mod.rs

@@ -3,8 +3,8 @@ use std::time::{Duration, SystemTime};
 
 use bitcoin::base64::prelude::BASE64_URL_SAFE_NO_PAD;
 use bitcoin::base64::Engine;
-use bitcoin::psbt::{Input as PsbtInput, Psbt};
-use bitcoin::{Address, Amount, FeeRate, OutPoint, Script, TxIn, TxOut};
+use bitcoin::psbt::Psbt;
+use bitcoin::{Address, FeeRate, OutPoint, Script, TxOut};
 use serde::de::Deserializer;
 use serde::{Deserialize, Serialize};
 use url::Url;

payjoin/tests/integration.rs

@@ -12,9 +12,8 @@ mod integration {
     use bitcoind::bitcoincore_rpc::{self, RpcApi};
     use log::{log_enabled, Level};
     use once_cell::sync::{Lazy, OnceCell};
-    use payjoin::psbt::InputPair;
     use payjoin::send::SenderBuilder;
-    use payjoin::{PjUri, PjUriBuilder, Request, Uri};
+    use payjoin::{InputPair, PjUri, PjUriBuilder, Request, Uri};
     use tracing_subscriber::{EnvFilter, FmtSubscriber};
     use url::Url;