13350991407

Committed 16 Feb 2025 02:43AM UTC coverage: 79.468% (+0.2%) from 79.269%

Build # 13350991407

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Pull #538

github

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web-flow

Commit Message

Merge 0e46f80b5 into 2627ef20f

Pull Request Pull Request #538: Make payjoin-cli v1 / v2 features additive

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/payjoin/src/send/mod.rs

//! Send Payjoin
//!
//! This module contains types and methods used to implement sending via Payjoin.
//!
//! For most use cases, we recommended enabling the `v2` feature, as it is
//! backwards compatible and provides the most convenient experience for users and implementors.
//! To use version 2, refer to `send::v2` module documentation.
//!
//! If you specifically need to use
//! version 1, refer to the `send::v1` module documentation after enabling the `v1` feature.

use std::str::FromStr;

use bitcoin::psbt::Psbt;
use bitcoin::{Amount, FeeRate, Script, ScriptBuf, TxOut, Weight};
pub use error::{BuildSenderError, ResponseError, ValidationError};
pub(crate) use error::{InternalBuildSenderError, InternalProposalError, InternalValidationError};
use url::Url;

use crate::psbt::PsbtExt;

// See usize casts
#[cfg(not(any(target_pointer_width = "32", target_pointer_width = "64")))]
compile_error!("This crate currently only supports 32 bit and 64 bit architectures");

mod error;

#[cfg(feature = "v1")]
#[cfg_attr(docsrs, doc(cfg(feature = "v1")))]
pub mod v1;
#[cfg(not(feature = "v1"))]
pub(crate) mod v1;

#[cfg(feature = "v2")]
#[cfg_attr(docsrs, doc(cfg(feature = "v2")))]
pub mod v2;

type InternalResult<T> = Result<T, InternalProposalError>;

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[cfg_attr(feature = "v2", derive(serde::Serialize, serde::Deserialize))]
pub(crate) struct AdditionalFeeContribution {
    max_amount: Amount,
    vout: usize,
}

/// Data required to validate the response against the original PSBT.
#[derive(Debug, Clone)]
pub struct PsbtContext {
    original_psbt: Psbt,
    disable_output_substitution: bool,
    fee_contribution: Option<AdditionalFeeContribution>,
    min_fee_rate: FeeRate,
    payee: ScriptBuf,
}

macro_rules! check_eq {
    ($proposed:expr, $original:expr, $error:ident) => {
        match ($proposed, $original) {
            (proposed, original) if proposed != original =>
                return Err(InternalProposalError::$error { proposed, original }),
            _ => (),
        }
    };
}

macro_rules! ensure {
    ($cond:expr, $error:ident) => {
        if !($cond) {
            return Err(InternalProposalError::$error);
        }
    };
}

impl PsbtContext {
    fn process_proposal(self, mut proposal: Psbt) -> InternalResult<Psbt> {
        self.basic_checks(&proposal)?;
        self.check_inputs(&proposal)?;
        let contributed_fee = self.check_outputs(&proposal)?;
        self.restore_original_utxos(&mut proposal)?;
        self.check_fees(&proposal, contributed_fee)?;
        Ok(proposal)
    }

    fn check_fees(&self, proposal: &Psbt, contributed_fee: Amount) -> InternalResult<()> {
        let proposed_fee = proposal.fee().map_err(InternalProposalError::Psbt)?;
        let original_fee = self.original_psbt.fee().map_err(InternalProposalError::Psbt)?;
        ensure!(original_fee <= proposed_fee, AbsoluteFeeDecreased);
        ensure!(contributed_fee <= proposed_fee - original_fee, PayeeTookContributedFee);
        let original_weight = self.original_psbt.clone().extract_tx_unchecked_fee_rate().weight();
        let original_fee_rate = original_fee / original_weight;
        let original_spks = self
            .original_psbt
            .input_pairs()
            .map(|input_pair| {
                input_pair
                    .previous_txout()
                    .map_err(InternalProposalError::PrevTxOut)
                    .map(|txout| txout.script_pubkey.clone())
            })
            .collect::<InternalResult<Vec<ScriptBuf>>>()?;
        let additional_input_weight = proposal.input_pairs().try_fold(
            Weight::ZERO,
            |acc, input_pair| -> InternalResult<Weight> {
                let spk = &input_pair
                    .previous_txout()
                    .map_err(InternalProposalError::PrevTxOut)?
                    .script_pubkey;
                if original_spks.contains(spk) {
                    Ok(acc)
                } else {
                    let weight = input_pair
                        .expected_input_weight()
                        .map_err(InternalProposalError::InputWeight)?;
                    Ok(acc + weight)
                }
            },
        )?;
        ensure!(
            contributed_fee <= original_fee_rate * additional_input_weight,
            FeeContributionPaysOutputSizeIncrease
        );
        if self.min_fee_rate > FeeRate::ZERO {
            let proposed_weight = proposal.clone().extract_tx_unchecked_fee_rate().weight();
            ensure!(proposed_fee / proposed_weight >= self.min_fee_rate, FeeRateBelowMinimum);
        }
        Ok(())
    }

    /// Check that the version and lock time are the same as in the original PSBT.
    fn basic_checks(&self, proposal: &Psbt) -> InternalResult<()> {
        check_eq!(
            proposal.unsigned_tx.version,
            self.original_psbt.unsigned_tx.version,
            VersionsDontMatch
        );
        check_eq!(
            proposal.unsigned_tx.lock_time,
            self.original_psbt.unsigned_tx.lock_time,
            LockTimesDontMatch
        );
        Ok(())
    }

    fn check_inputs(&self, proposal: &Psbt) -> InternalResult<()> {
        let mut original_inputs = self.original_psbt.input_pairs().peekable();

        for proposed in proposal.input_pairs() {
            ensure!(proposed.psbtin.bip32_derivation.is_empty(), TxInContainsKeyPaths);
            ensure!(proposed.psbtin.partial_sigs.is_empty(), ContainsPartialSigs);
            match original_inputs.peek() {
                // our (sender)
                Some(original)
                    if proposed.txin.previous_output == original.txin.previous_output =>
                {
                    check_eq!(
                        proposed.txin.sequence,
                        original.txin.sequence,
                        SenderTxinSequenceChanged
                    );
                    ensure!(
                        proposed.psbtin.final_script_sig.is_none(),
                        SenderTxinContainsFinalScriptSig
                    );
                    ensure!(
                        proposed.psbtin.final_script_witness.is_none(),
                        SenderTxinContainsFinalScriptWitness
                    );
                    original_inputs.next();
                }
                // theirs (receiver)
                None | Some(_) => {
                    let original = self
                        .original_psbt
                        .input_pairs()
                        .next()
                        .ok_or(InternalProposalError::NoInputs)?;
                    // Verify the PSBT input is finalized
                    ensure!(
                        proposed.psbtin.final_script_sig.is_some()
                            || proposed.psbtin.final_script_witness.is_some(),
                        ReceiverTxinNotFinalized
                    );
                    // Verify that non_witness_utxo or witness_utxo are filled in.
                    ensure!(
                        proposed.psbtin.witness_utxo.is_some()
                            || proposed.psbtin.non_witness_utxo.is_some(),
                        ReceiverTxinMissingUtxoInfo
                    );
                    ensure!(proposed.txin.sequence == original.txin.sequence, MixedSequence);
                }
            }
        }
        ensure!(original_inputs.peek().is_none(), MissingOrShuffledInputs);
        Ok(())
    }

    /// Restore Original PSBT utxos that the receiver stripped.
    /// The BIP78 spec requires utxo information to be removed, but many wallets
    /// require it to be present to sign.
    fn restore_original_utxos(&self, proposal: &mut Psbt) -> InternalResult<()> {
        let mut original_inputs = self.original_psbt.input_pairs().peekable();
        let proposal_inputs =
            proposal.unsigned_tx.input.iter().zip(&mut proposal.inputs).peekable();

        for (proposed_txin, proposed_psbtin) in proposal_inputs {
            if let Some(original) = original_inputs.peek() {
                if proposed_txin.previous_output == original.txin.previous_output {
                    proposed_psbtin.non_witness_utxo = original.psbtin.non_witness_utxo.clone();
                    proposed_psbtin.witness_utxo = original.psbtin.witness_utxo.clone();
                    proposed_psbtin.bip32_derivation = original.psbtin.bip32_derivation.clone();
                    proposed_psbtin.tap_internal_key = original.psbtin.tap_internal_key;
                    proposed_psbtin.tap_key_origins = original.psbtin.tap_key_origins.clone();
                    original_inputs.next();
                }
            }
        }
        Ok(())
    }

    fn check_outputs(&self, proposal: &Psbt) -> InternalResult<Amount> {
        let mut original_outputs =
            self.original_psbt.unsigned_tx.output.iter().enumerate().peekable();
        let mut contributed_fee = Amount::ZERO;

        for (proposed_txout, proposed_psbtout) in
            proposal.unsigned_tx.output.iter().zip(&proposal.outputs)
        {
            ensure!(proposed_psbtout.bip32_derivation.is_empty(), TxOutContainsKeyPaths);
            match (original_outputs.peek(), self.fee_contribution) {
                // fee output
                (
                    Some((original_output_index, original_output)),
                    Some(AdditionalFeeContribution {
                        max_amount: max_fee_contrib,
                        vout: fee_contrib_idx,
                    }),
                ) if proposed_txout.script_pubkey == original_output.script_pubkey
                    && *original_output_index == fee_contrib_idx =>
                {
                    if proposed_txout.value < original_output.value {
                        contributed_fee = original_output.value - proposed_txout.value;
                        ensure!(contributed_fee <= max_fee_contrib, FeeContributionExceedsMaximum);
                        // The remaining fee checks are done in later in `check_fees`
                    }
                    original_outputs.next();
                }
                // payee output
                (Some((_original_output_index, original_output)), _)
                    if original_output.script_pubkey == self.payee =>
                {
                    ensure!(
                        !self.disable_output_substitution
                            || (proposed_txout.script_pubkey == original_output.script_pubkey
                                && proposed_txout.value >= original_output.value),
                        DisallowedOutputSubstitution
                    );
                    original_outputs.next();
                }
                // our output
                (Some((_original_output_index, original_output)), _)
                    if proposed_txout.script_pubkey == original_output.script_pubkey =>
                {
                    ensure!(proposed_txout.value >= original_output.value, OutputValueDecreased);
                    original_outputs.next();
                }
                // additional output
                _ => (),
            }
        }

        ensure!(original_outputs.peek().is_none(), MissingOrShuffledOutputs);
        Ok(contributed_fee)
    }
}

/// Ensure that the payee's output scriptPubKey appears in the list of outputs exactly once,
/// and that the payee's output amount matches the requested amount.
fn check_single_payee(
    psbt: &Psbt,
    script_pubkey: &Script,
    amount: Option<bitcoin::Amount>,
) -> Result<(), InternalBuildSenderError> {
    let mut payee_found = false;
    for output in &psbt.unsigned_tx.output {
        if output.script_pubkey == *script_pubkey {
            if let Some(amount) = amount {
                if output.value != amount {
                    return Err(InternalBuildSenderError::PayeeValueNotEqual);
                }
            }
            if payee_found {
                return Err(InternalBuildSenderError::MultiplePayeeOutputs);
            }
            payee_found = true;
        }
    }
    if payee_found {
        Ok(())
    } else {
        Err(InternalBuildSenderError::MissingPayeeOutput)
    }
}

fn clear_unneeded_fields(psbt: &mut Psbt) {
    psbt.xpub_mut().clear();
    psbt.proprietary_mut().clear();
    psbt.unknown_mut().clear();
    for input in psbt.inputs_mut() {
        input.bip32_derivation.clear();
        input.tap_internal_key = None;
        input.tap_key_origins.clear();
        input.tap_key_sig = None;
        input.tap_merkle_root = None;
        input.tap_script_sigs.clear();
        input.proprietary.clear();
        input.unknown.clear();
    }
    for output in psbt.outputs_mut() {
        output.bip32_derivation.clear();
        output.tap_internal_key = None;
        output.tap_key_origins.clear();
        output.proprietary.clear();
        output.unknown.clear();
    }
}

/// Ensure that an additional fee output is sufficient to pay for the specified additional fee
fn check_fee_output_amount(
    output: &TxOut,
    fee: bitcoin::Amount,
    clamp_fee_contribution: bool,
) -> Result<bitcoin::Amount, InternalBuildSenderError> {
    if output.value < fee {
        if clamp_fee_contribution {
            Ok(output.value)
        } else {
            Err(InternalBuildSenderError::FeeOutputValueLowerThanFeeContribution)
        }
    } else {
        Ok(fee)
    }
}

/// Find the sender's change output index by eliminating the payee's output as a candidate.
fn find_change_index(
    psbt: &Psbt,
    payee: &Script,
    fee: bitcoin::Amount,
    clamp_fee_contribution: bool,
) -> Result<Option<AdditionalFeeContribution>, InternalBuildSenderError> {
    match (psbt.unsigned_tx.output.len(), clamp_fee_contribution) {
        (0, _) => return Err(InternalBuildSenderError::NoOutputs),
        (1, false) if psbt.unsigned_tx.output[0].script_pubkey == *payee =>
            return Err(InternalBuildSenderError::FeeOutputValueLowerThanFeeContribution),
        (1, true) if psbt.unsigned_tx.output[0].script_pubkey == *payee => return Ok(None),
        (1, _) => return Err(InternalBuildSenderError::MissingPayeeOutput),
        (2, _) => (),
        _ => return Err(InternalBuildSenderError::AmbiguousChangeOutput),
    }
    let (index, output) = psbt
        .unsigned_tx
        .output
        .iter()
        .enumerate()
        .find(|(_, output)| output.script_pubkey != *payee)
        .ok_or(InternalBuildSenderError::MultiplePayeeOutputs)?;

    Ok(Some(AdditionalFeeContribution {
        max_amount: check_fee_output_amount(output, fee, clamp_fee_contribution)?,
        vout: index,
    }))
}

/// Check that the change output index is not out of bounds
/// and that the additional fee contribution is not less than specified.
fn check_change_index(
    psbt: &Psbt,
    payee: &Script,
    fee: bitcoin::Amount,
    index: usize,
    clamp_fee_contribution: bool,
) -> Result<AdditionalFeeContribution, InternalBuildSenderError> {
    let output = psbt
        .unsigned_tx
        .output
        .get(index)
        .ok_or(InternalBuildSenderError::ChangeIndexOutOfBounds)?;
    if output.script_pubkey == *payee {
        return Err(InternalBuildSenderError::ChangeIndexPointsAtPayee);
    }
    Ok(AdditionalFeeContribution {
        max_amount: check_fee_output_amount(output, fee, clamp_fee_contribution)?,
        vout: index,
    })
}

fn determine_fee_contribution(
    psbt: &Psbt,
    payee: &Script,
    fee_contribution: Option<(bitcoin::Amount, Option<usize>)>,
    clamp_fee_contribution: bool,
) -> Result<Option<AdditionalFeeContribution>, InternalBuildSenderError> {
    Ok(match fee_contribution {
        Some((fee, None)) => find_change_index(psbt, payee, fee, clamp_fee_contribution)?,
        Some((fee, Some(index))) =>
            Some(check_change_index(psbt, payee, fee, index, clamp_fee_contribution)?),
        None => None,
    })
}

fn serialize_url(
    endpoint: Url,
    disable_output_substitution: bool,
    fee_contribution: Option<AdditionalFeeContribution>,
    min_fee_rate: FeeRate,
    version: &str,
) -> Result<Url, url::ParseError> {
    let mut url = endpoint;
    url.query_pairs_mut().append_pair("v", version);
    if disable_output_substitution {
        url.query_pairs_mut().append_pair("disableoutputsubstitution", "true");
    }
    if let Some(AdditionalFeeContribution { max_amount, vout }) = fee_contribution {
        url.query_pairs_mut()
            .append_pair("additionalfeeoutputindex", &vout.to_string())
            .append_pair("maxadditionalfeecontribution", &max_amount.to_sat().to_string());
    }
    if min_fee_rate > FeeRate::ZERO {
        // TODO serialize in rust-bitcoin <https://github.com/rust-bitcoin/rust-bitcoin/pull/1787/files#diff-c2ea40075e93ccd068673873166cfa3312ec7439d6bc5a4cbc03e972c7e045c4>
        let float_fee_rate = min_fee_rate.to_sat_per_kwu() as f32 / 250.0_f32;
        url.query_pairs_mut().append_pair("minfeerate", &float_fee_rate.to_string());
    }
    Ok(url)
}

#[cfg(test)]
pub(crate) mod test {
    use std::str::FromStr;

    use bitcoin::psbt::Psbt;
    use bitcoin::FeeRate;
    use url::Url;

    use super::serialize_url;
    use crate::psbt::PsbtExt;
    use crate::send::AdditionalFeeContribution;

    pub(crate) const ORIGINAL_PSBT: &str = "cHNidP8BAHMCAAAAAY8nutGgJdyYGXWiBEb45Hoe9lWGbkxh/6bNiOJdCDuDAAAAAAD+////AtyVuAUAAAAAF6kUHehJ8GnSdBUOOv6ujXLrWmsJRDCHgIQeAAAAAAAXqRR3QJbbz0hnQ8IvQ0fptGn+votneofTAAAAAAEBIKgb1wUAAAAAF6kU3k4ekGHKWRNbA1rV5tR5kEVDVNCHAQcXFgAUx4pFclNVgo1WWAdN1SYNX8tphTABCGsCRzBEAiB8Q+A6dep+Rz92vhy26lT0AjZn4PRLi8Bf9qoB/CMk0wIgP/Rj2PWZ3gEjUkTlhDRNAQ0gXwTO7t9n+V14pZ6oljUBIQMVmsAaoNWHVMS02LfTSe0e388LNitPa1UQZyOihY+FFgABABYAFEb2Giu6c4KO5YW0pfw3lGp9jMUUAAA=";
    const PAYJOIN_PROPOSAL: &str = "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";

    pub(crate) fn create_psbt_context() -> super::PsbtContext {
        let original_psbt = Psbt::from_str(ORIGINAL_PSBT).unwrap();
        eprintln!("original: {:#?}", original_psbt);
        let payee = original_psbt.unsigned_tx.output[1].script_pubkey.clone();
        super::PsbtContext {
            original_psbt,
            disable_output_substitution: false,
            fee_contribution: Some(AdditionalFeeContribution {
                max_amount: bitcoin::Amount::from_sat(182),
                vout: 0,
            }),
            min_fee_rate: FeeRate::ZERO,
            payee,
        }
    }

    #[test]
    fn official_vectors() {
        let original_psbt = Psbt::from_str(ORIGINAL_PSBT).unwrap();
        eprintln!("original: {:#?}", original_psbt);
        let ctx = create_psbt_context();
        let mut proposal = Psbt::from_str(PAYJOIN_PROPOSAL).unwrap();
        eprintln!("proposal: {:#?}", proposal);
        for output in proposal.outputs_mut() {
            output.bip32_derivation.clear();
        }
        for input in proposal.inputs_mut() {
            input.bip32_derivation.clear();
        }
        proposal.inputs_mut()[0].witness_utxo = None;
        ctx.process_proposal(proposal).unwrap();
    }

    #[test]
    #[should_panic]
    fn test_receiver_steals_sender_change() {
        let original_psbt = Psbt::from_str(ORIGINAL_PSBT).unwrap();
        eprintln!("original: {:#?}", original_psbt);
        let ctx = create_psbt_context();
        let mut proposal = Psbt::from_str(PAYJOIN_PROPOSAL).unwrap();
        eprintln!("proposal: {:#?}", proposal);
        for output in proposal.outputs_mut() {
            output.bip32_derivation.clear();
        }
        for input in proposal.inputs_mut() {
            input.bip32_derivation.clear();
        }
        proposal.inputs_mut()[0].witness_utxo = None;
        // Steal 0.5 BTC from the sender output and add it to the receiver output
        proposal.unsigned_tx.output[0].value -= bitcoin::Amount::from_btc(0.5).unwrap();
        proposal.unsigned_tx.output[1].value += bitcoin::Amount::from_btc(0.5).unwrap();
        ctx.process_proposal(proposal).unwrap();
    }

    #[test]
    fn test_disable_output_substitution_query_param() {
        let url =
            serialize_url(Url::parse("http://localhost").unwrap(), true, None, FeeRate::ZERO, "2")
                .unwrap();
        assert_eq!(url, Url::parse("http://localhost?v=2&disableoutputsubstitution=true").unwrap());

        let url =
            serialize_url(Url::parse("http://localhost").unwrap(), false, None, FeeRate::ZERO, "2")
                .unwrap();
        assert_eq!(url, Url::parse("http://localhost?v=2").unwrap());
    }
}

1	//! Send Payjoin
2	//!
3	//! This module contains types and methods used to implement sending via Payjoin.
4	//!
5	//! For most use cases, we recommended enabling the `v2` feature, as it is
6	//! backwards compatible and provides the most convenient experience for users and implementors.
7	//! To use version 2, refer to `send::v2` module documentation.
8	//!
9	//! If you specifically need to use
10	//! version 1, refer to the `send::v1` module documentation after enabling the `v1` feature.
11
12	use std::str::FromStr;
13
14	use bitcoin::psbt::Psbt;
15	use bitcoin::{Amount, FeeRate, Script, ScriptBuf, TxOut, Weight};
16	pub use error::{BuildSenderError, ResponseError, ValidationError};
17	pub(crate) use error::{InternalBuildSenderError, InternalProposalError, InternalValidationError};
18	use url::Url;
19
20	use crate::psbt::PsbtExt;
21
22	// See usize casts
23	#[cfg(not(any(target_pointer_width = "32", target_pointer_width = "64")))]
24	compile_error!("This crate currently only supports 32 bit and 64 bit architectures");
25
26	mod error;
27
28	#[cfg(feature = "v1")]
29	#[cfg_attr(docsrs, doc(cfg(feature = "v1")))]
30	pub mod v1;
31	#[cfg(not(feature = "v1"))]
32	pub(crate) mod v1;
33
34	#[cfg(feature = "v2")]
35	#[cfg_attr(docsrs, doc(cfg(feature = "v2")))]
36	pub mod v2;
37
38	type InternalResult<T> = Result<T, InternalProposalError>;
39
40	#[derive(Debug, Clone, Copy, PartialEq, Eq)]
41	#[cfg_attr(feature = "v2", derive(serde::Serialize, serde::Deserialize))]
42	pub(crate) struct AdditionalFeeContribution {
43	max_amount: Amount,
44	vout: usize,
45	}
46
47	/// Data required to validate the response against the original PSBT.
48	#[derive(Debug, Clone)]
49	pub struct PsbtContext {
50	original_psbt: Psbt,
51	disable_output_substitution: bool,
52	fee_contribution: Option<AdditionalFeeContribution>,
53	min_fee_rate: FeeRate,
54	payee: ScriptBuf,
55	}
56
57	macro_rules! check_eq {
58	($proposed:expr, $original:expr, $error:ident) => {
59	match ($proposed, $original) {
60	(proposed, original) if proposed != original =>
61	return Err(InternalProposalError::$error { proposed, original }),
62	_ => (),
63	}
64	};
65	}
66
67	macro_rules! ensure {
68	($cond:expr, $error:ident) => {
69	if !($cond) {
70	return Err(InternalProposalError::$error);
71	}
72	};
73	}
74
75	impl PsbtContext {
76	fn process_proposal(self, mut proposal: Psbt) -> InternalResult<Psbt> {	13✔
77	self.basic_checks(&proposal)?;	13✔
78	self.check_inputs(&proposal)?;	13✔
79	let contributed_fee = self.check_outputs(&proposal)?;	13✔
80	self.restore_original_utxos(&mut proposal)?;	12✔
81	self.check_fees(&proposal, contributed_fee)?;	12✔
82	Ok(proposal)	12✔
83	}	13✔
84
85	fn check_fees(&self, proposal: &Psbt, contributed_fee: Amount) -> InternalResult<()> {	12✔
86	let proposed_fee = proposal.fee().map_err(InternalProposalError::Psbt)?;	12✔
87	let original_fee = self.original_psbt.fee().map_err(InternalProposalError::Psbt)?;	12✔
88	ensure!(original_fee <= proposed_fee, AbsoluteFeeDecreased);	12✔
89	ensure!(contributed_fee <= proposed_fee - original_fee, PayeeTookContributedFee);	12✔
90	let original_weight = self.original_psbt.clone().extract_tx_unchecked_fee_rate().weight();	12✔
91	let original_fee_rate = original_fee / original_weight;	12✔
92	let original_spks = self	12✔
93	.original_psbt	12✔
94	.input_pairs()	12✔
95	.map(\|input_pair\| {	12✔
96	input_pair	12✔
97	.previous_txout()	12✔
98	.map_err(InternalProposalError::PrevTxOut)	12✔
99	.map(\|txout\| txout.script_pubkey.clone())	12✔
100	})	12✔
101	.collect::<InternalResult<Vec<ScriptBuf>>>()?;	12✔
102	let additional_input_weight = proposal.input_pairs().try_fold(	12✔
103	Weight::ZERO,	12✔
104	\|acc, input_pair\| -> InternalResult<Weight> {	122✔
105	let spk = &input_pair	122✔
106	.previous_txout()	122✔
107	.map_err(InternalProposalError::PrevTxOut)?	122✔
108	.script_pubkey;
109	if original_spks.contains(spk) {	122✔
110	Ok(acc)	12✔
111	} else {
112	let weight = input_pair	110✔
113	.expected_input_weight()	110✔
114	.map_err(InternalProposalError::InputWeight)?;	110✔
115	Ok(acc + weight)	110✔
116	}
117	},	122✔
118	)?;	12✔
119	ensure!(	12✔
120	contributed_fee <= original_fee_rate * additional_input_weight,	12✔
121	FeeContributionPaysOutputSizeIncrease	12✔
122	);	12✔
123	if self.min_fee_rate > FeeRate::ZERO {	12✔
124	let proposed_weight = proposal.clone().extract_tx_unchecked_fee_rate().weight();	5✔
125	ensure!(proposed_fee / proposed_weight >= self.min_fee_rate, FeeRateBelowMinimum);	5✔
126	}	7✔
127	Ok(())	12✔
128	}	12✔
129
130	/// Check that the version and lock time are the same as in the original PSBT.
131	fn basic_checks(&self, proposal: &Psbt) -> InternalResult<()> {	13✔
132	check_eq!(	13✔
133	proposal.unsigned_tx.version,	13✔
134	self.original_psbt.unsigned_tx.version,	13✔
135	VersionsDontMatch	13✔
136	);	13✔
137	check_eq!(	13✔
138	proposal.unsigned_tx.lock_time,	13✔
139	self.original_psbt.unsigned_tx.lock_time,	13✔
140	LockTimesDontMatch	13✔
141	);	13✔
142	Ok(())	13✔
143	}	13✔
144
145	fn check_inputs(&self, proposal: &Psbt) -> InternalResult<()> {	13✔
146	let mut original_inputs = self.original_psbt.input_pairs().peekable();	13✔
147
148	for proposed in proposal.input_pairs() {	124✔
149	ensure!(proposed.psbtin.bip32_derivation.is_empty(), TxInContainsKeyPaths);	124✔
150	ensure!(proposed.psbtin.partial_sigs.is_empty(), ContainsPartialSigs);	124✔
151	match original_inputs.peek() {	124✔
152	// our (sender)
153	Some(original)	13✔
154	if proposed.txin.previous_output == original.txin.previous_output =>	119✔
155	{	13✔
156	check_eq!(	13✔
157	proposed.txin.sequence,	13✔
158	original.txin.sequence,	13✔
159	SenderTxinSequenceChanged	13✔
160	);	13✔
161	ensure!(	13✔
162	proposed.psbtin.final_script_sig.is_none(),	13✔
163	SenderTxinContainsFinalScriptSig	13✔
164	);	13✔
165	ensure!(	13✔
166	proposed.psbtin.final_script_witness.is_none(),	13✔
167	SenderTxinContainsFinalScriptWitness	13✔
168	);	13✔
169	original_inputs.next();	13✔
170	}
171	// theirs (receiver)
172	None \| Some(_) => {
173	let original = self	111✔
174	.original_psbt	111✔
175	.input_pairs()	111✔
176	.next()	111✔
177	.ok_or(InternalProposalError::NoInputs)?;	111✔
178	// Verify the PSBT input is finalized
179	ensure!(	111✔
180	proposed.psbtin.final_script_sig.is_some()	111✔
181	\|\| proposed.psbtin.final_script_witness.is_some(),	107✔
182	ReceiverTxinNotFinalized
183	);
184	// Verify that non_witness_utxo or witness_utxo are filled in.
185	ensure!(	111✔
186	proposed.psbtin.witness_utxo.is_some()	111✔
187	\|\| proposed.psbtin.non_witness_utxo.is_some(),	×
188	ReceiverTxinMissingUtxoInfo
189	);
190	ensure!(proposed.txin.sequence == original.txin.sequence, MixedSequence);	111✔
191	}
192	}
193	}
194	ensure!(original_inputs.peek().is_none(), MissingOrShuffledInputs);	13✔
195	Ok(())	13✔
196	}	13✔
197
198	/// Restore Original PSBT utxos that the receiver stripped.
199	/// The BIP78 spec requires utxo information to be removed, but many wallets
200	/// require it to be present to sign.
201	fn restore_original_utxos(&self, proposal: &mut Psbt) -> InternalResult<()> {	12✔
202	let mut original_inputs = self.original_psbt.input_pairs().peekable();	12✔
203	let proposal_inputs =	12✔
204	proposal.unsigned_tx.input.iter().zip(&mut proposal.inputs).peekable();	12✔
205
206	for (proposed_txin, proposed_psbtin) in proposal_inputs {	134✔
207	if let Some(original) = original_inputs.peek() {	122✔
208	if proposed_txin.previous_output == original.txin.previous_output {	118✔
209	proposed_psbtin.non_witness_utxo = original.psbtin.non_witness_utxo.clone();	12✔
210	proposed_psbtin.witness_utxo = original.psbtin.witness_utxo.clone();	12✔
211	proposed_psbtin.bip32_derivation = original.psbtin.bip32_derivation.clone();	12✔
212	proposed_psbtin.tap_internal_key = original.psbtin.tap_internal_key;	12✔
213	proposed_psbtin.tap_key_origins = original.psbtin.tap_key_origins.clone();	12✔
214	original_inputs.next();	12✔
215	}	106✔
216	}	4✔
217	}
218	Ok(())	12✔
219	}	12✔
220
221	fn check_outputs(&self, proposal: &Psbt) -> InternalResult<Amount> {	13✔
222	let mut original_outputs =	13✔
223	self.original_psbt.unsigned_tx.output.iter().enumerate().peekable();	13✔
224	let mut contributed_fee = Amount::ZERO;	13✔
225
226	for (proposed_txout, proposed_psbtout) in	25✔
227	proposal.unsigned_tx.output.iter().zip(&proposal.outputs)	13✔
228	{
229	ensure!(proposed_psbtout.bip32_derivation.is_empty(), TxOutContainsKeyPaths);	25✔
230	match (original_outputs.peek(), self.fee_contribution) {	25✔
231	// fee output
232	(
233	Some((original_output_index, original_output)),	23✔
234	Some(AdditionalFeeContribution {
235	max_amount: max_fee_contrib,	12✔
236	vout: fee_contrib_idx,	12✔
237	}),
238	) if proposed_txout.script_pubkey == original_output.script_pubkey	23✔
239	&& *original_output_index == fee_contrib_idx =>	15✔
240	{	12✔
241	if proposed_txout.value < original_output.value {	12✔
242	contributed_fee = original_output.value - proposed_txout.value;	11✔
243	ensure!(contributed_fee <= max_fee_contrib, FeeContributionExceedsMaximum);	11✔
244	// The remaining fee checks are done in later in `check_fees`
245	}	1✔
246	original_outputs.next();	11✔
247	}
248	// payee output
249	(Some((_original_output_index, original_output)), _)	12✔
250	if original_output.script_pubkey == self.payee =>	12✔
251	{	12✔
252	ensure!(	12✔
253	!self.disable_output_substitution	12✔
254	\|\| (proposed_txout.script_pubkey == original_output.script_pubkey	×
255	&& proposed_txout.value >= original_output.value),	×
256	DisallowedOutputSubstitution
257	);
258	original_outputs.next();	12✔
259	}
260	// our output
UNCOV 261	(Some((_original_output_index, original_output)), _)	×
UNCOV 262	if proposed_txout.script_pubkey == original_output.script_pubkey =>	×
263	{	×
264	ensure!(proposed_txout.value >= original_output.value, OutputValueDecreased);	×
265	original_outputs.next();	×
266	}
267	// additional output
268	_ => (),	1✔
269	}
270	}
271
272	ensure!(original_outputs.peek().is_none(), MissingOrShuffledOutputs);	12✔
273	Ok(contributed_fee)	12✔
274	}	13✔
275	}
276
277	/// Ensure that the payee's output scriptPubKey appears in the list of outputs exactly once,
278	/// and that the payee's output amount matches the requested amount.
279	fn check_single_payee(	13✔
280	psbt: &Psbt,	13✔
281	script_pubkey: &Script,	13✔
282	amount: Option<bitcoin::Amount>,	13✔
283	) -> Result<(), InternalBuildSenderError> {	13✔
284	let mut payee_found = false;	13✔
285	for output in &psbt.unsigned_tx.output {	38✔
286	if output.script_pubkey == *script_pubkey {	25✔
287	if let Some(amount) = amount {	13✔
288	if output.value != amount {	10✔
289	return Err(InternalBuildSenderError::PayeeValueNotEqual);	×
290	}	10✔
291	}	3✔
292	if payee_found {	13✔
293	return Err(InternalBuildSenderError::MultiplePayeeOutputs);	×
294	}	13✔
295	payee_found = true;	13✔
296	}	12✔
297	}
298	if payee_found {	13✔
299	Ok(())	13✔
300	} else {
301	Err(InternalBuildSenderError::MissingPayeeOutput)	×
302	}
303	}	13✔
304
305	fn clear_unneeded_fields(psbt: &mut Psbt) {	13✔
306	psbt.xpub_mut().clear();	13✔
307	psbt.proprietary_mut().clear();	13✔
308	psbt.unknown_mut().clear();	13✔
309	for input in psbt.inputs_mut() {	13✔
310	input.bip32_derivation.clear();	13✔
311	input.tap_internal_key = None;	13✔
312	input.tap_key_origins.clear();	13✔
313	input.tap_key_sig = None;	13✔
314	input.tap_merkle_root = None;	13✔
315	input.tap_script_sigs.clear();	13✔
316	input.proprietary.clear();	13✔
317	input.unknown.clear();	13✔
318	}	13✔
319	for output in psbt.outputs_mut() {	25✔
320	output.bip32_derivation.clear();	25✔
321	output.tap_internal_key = None;	25✔
322	output.tap_key_origins.clear();	25✔
323	output.proprietary.clear();	25✔
324	output.unknown.clear();	25✔
325	}	25✔
326	}	13✔
327
328	/// Ensure that an additional fee output is sufficient to pay for the specified additional fee
329	fn check_fee_output_amount(	11✔
330	output: &TxOut,	11✔
331	fee: bitcoin::Amount,	11✔
332	clamp_fee_contribution: bool,	11✔
333	) -> Result<bitcoin::Amount, InternalBuildSenderError> {	11✔
334	if output.value < fee {	11✔
335	if clamp_fee_contribution {	×
336	Ok(output.value)	×
337	} else {
338	Err(InternalBuildSenderError::FeeOutputValueLowerThanFeeContribution)	×
339	}
340	} else {
341	Ok(fee)	11✔
342	}
343	}	11✔
344
345	/// Find the sender's change output index by eliminating the payee's output as a candidate.
346	fn find_change_index(	7✔
347	psbt: &Psbt,	7✔
348	payee: &Script,	7✔
349	fee: bitcoin::Amount,	7✔
350	clamp_fee_contribution: bool,	7✔
351	) -> Result<Option<AdditionalFeeContribution>, InternalBuildSenderError> {	7✔
352	match (psbt.unsigned_tx.output.len(), clamp_fee_contribution) {	7✔
353	(0, _) => return Err(InternalBuildSenderError::NoOutputs),	×
354	(1, false) if psbt.unsigned_tx.output[0].script_pubkey == *payee =>	×
355	return Err(InternalBuildSenderError::FeeOutputValueLowerThanFeeContribution),	×
356	(1, true) if psbt.unsigned_tx.output[0].script_pubkey == *payee => return Ok(None),	×
357	(1, _) => return Err(InternalBuildSenderError::MissingPayeeOutput),	×
358	(2, _) => (),	7✔
359	_ => return Err(InternalBuildSenderError::AmbiguousChangeOutput),	×
360	}
361	let (index, output) = psbt	7✔
362	.unsigned_tx	7✔
363	.output	7✔
364	.iter()	7✔
365	.enumerate()	7✔
366	.find(\|(_, output)\| output.script_pubkey != *payee)	9✔
367	.ok_or(InternalBuildSenderError::MultiplePayeeOutputs)?;	7✔
368
369	Ok(Some(AdditionalFeeContribution {
370	max_amount: check_fee_output_amount(output, fee, clamp_fee_contribution)?,	7✔
371	vout: index,	7✔
372	}))
373	}	7✔
374
375	/// Check that the change output index is not out of bounds
376	/// and that the additional fee contribution is not less than specified.
377	fn check_change_index(	4✔
378	psbt: &Psbt,	4✔
379	payee: &Script,	4✔
380	fee: bitcoin::Amount,	4✔
381	index: usize,	4✔
382	clamp_fee_contribution: bool,	4✔
383	) -> Result<AdditionalFeeContribution, InternalBuildSenderError> {	4✔
384	let output = psbt	4✔
385	.unsigned_tx	4✔
386	.output	4✔
387	.get(index)	4✔
388	.ok_or(InternalBuildSenderError::ChangeIndexOutOfBounds)?;	4✔
389	if output.script_pubkey == *payee {	4✔
390	return Err(InternalBuildSenderError::ChangeIndexPointsAtPayee);	×
391	}	4✔
392	Ok(AdditionalFeeContribution {	4✔
393	max_amount: check_fee_output_amount(output, fee, clamp_fee_contribution)?,	4✔
394	vout: index,	4✔
395	})
396	}	4✔
397
398	fn determine_fee_contribution(	13✔
399	psbt: &Psbt,	13✔
400	payee: &Script,	13✔
401	fee_contribution: Option<(bitcoin::Amount, Option<usize>)>,	13✔
402	clamp_fee_contribution: bool,	13✔
403	) -> Result<Option<AdditionalFeeContribution>, InternalBuildSenderError> {	13✔
404	Ok(match fee_contribution {	11✔
405	Some((fee, None)) => find_change_index(psbt, payee, fee, clamp_fee_contribution)?,	7✔
406	Some((fee, Some(index))) =>	4✔
407	Some(check_change_index(psbt, payee, fee, index, clamp_fee_contribution)?),	4✔
408	None => None,	2✔
409	})
410	}	13✔
411
412	fn serialize_url(	15✔
413	endpoint: Url,	15✔
414	disable_output_substitution: bool,	15✔
415	fee_contribution: Option<AdditionalFeeContribution>,	15✔
416	min_fee_rate: FeeRate,	15✔
417	version: &str,	15✔
418	) -> Result<Url, url::ParseError> {	15✔
419	let mut url = endpoint;	15✔
420	url.query_pairs_mut().append_pair("v", version);	15✔
421	if disable_output_substitution {	15✔
422	url.query_pairs_mut().append_pair("disableoutputsubstitution", "true");	1✔
423	}	14✔
424	if let Some(AdditionalFeeContribution { max_amount, vout }) = fee_contribution {	15✔
425	url.query_pairs_mut()	12✔
426	.append_pair("additionalfeeoutputindex", &vout.to_string())	12✔
427	.append_pair("maxadditionalfeecontribution", &max_amount.to_sat().to_string());	12✔
428	}	12✔
429	if min_fee_rate > FeeRate::ZERO {	15✔
430	// TODO serialize in rust-bitcoin <https://github.com/rust-bitcoin/rust-bitcoin/pull/1787/files#diff-c2ea40075e93ccd068673873166cfa3312ec7439d6bc5a4cbc03e972c7e045c4>	6✔
431	let float_fee_rate = min_fee_rate.to_sat_per_kwu() as f32 / 250.0_f32;	6✔
432	url.query_pairs_mut().append_pair("minfeerate", &float_fee_rate.to_string());	6✔
433	}	9✔
434	Ok(url)	15✔
435	}	15✔
436
437	#[cfg(test)]
438	pub(crate) mod test {
439	use std::str::FromStr;
440
441	use bitcoin::psbt::Psbt;
442	use bitcoin::FeeRate;
443	use url::Url;
444
445	use super::serialize_url;
446	use crate::psbt::PsbtExt;
447	use crate::send::AdditionalFeeContribution;
448
449	pub(crate) const ORIGINAL_PSBT: &str = "cHNidP8BAHMCAAAAAY8nutGgJdyYGXWiBEb45Hoe9lWGbkxh/6bNiOJdCDuDAAAAAAD+////AtyVuAUAAAAAF6kUHehJ8GnSdBUOOv6ujXLrWmsJRDCHgIQeAAAAAAAXqRR3QJbbz0hnQ8IvQ0fptGn+votneofTAAAAAAEBIKgb1wUAAAAAF6kU3k4ekGHKWRNbA1rV5tR5kEVDVNCHAQcXFgAUx4pFclNVgo1WWAdN1SYNX8tphTABCGsCRzBEAiB8Q+A6dep+Rz92vhy26lT0AjZn4PRLi8Bf9qoB/CMk0wIgP/Rj2PWZ3gEjUkTlhDRNAQ0gXwTO7t9n+V14pZ6oljUBIQMVmsAaoNWHVMS02LfTSe0e388LNitPa1UQZyOihY+FFgABABYAFEb2Giu6c4KO5YW0pfw3lGp9jMUUAAA=";
450	const PAYJOIN_PROPOSAL: &str = "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";
451
452	pub(crate) fn create_psbt_context() -> super::PsbtContext {	4✔
453	let original_psbt = Psbt::from_str(ORIGINAL_PSBT).unwrap();	4✔
454	eprintln!("original: {:#?}", original_psbt);	4✔
455	let payee = original_psbt.unsigned_tx.output[1].script_pubkey.clone();	4✔
456	super::PsbtContext {	4✔
457	original_psbt,	4✔
458	disable_output_substitution: false,	4✔
459	fee_contribution: Some(AdditionalFeeContribution {	4✔
460	max_amount: bitcoin::Amount::from_sat(182),	4✔
461	vout: 0,	4✔
462	}),	4✔
463	min_fee_rate: FeeRate::ZERO,	4✔
464	payee,	4✔
465	}	4✔
466	}	4✔
467
468	#[test]
469	fn official_vectors() {	1✔
470	let original_psbt = Psbt::from_str(ORIGINAL_PSBT).unwrap();	1✔
471	eprintln!("original: {:#?}", original_psbt);	1✔
472	let ctx = create_psbt_context();	1✔
473	let mut proposal = Psbt::from_str(PAYJOIN_PROPOSAL).unwrap();	1✔
474	eprintln!("proposal: {:#?}", proposal);	1✔
475	for output in proposal.outputs_mut() {	2✔
476	output.bip32_derivation.clear();	2✔
477	}	2✔
478	for input in proposal.inputs_mut() {	2✔
479	input.bip32_derivation.clear();	2✔
480	}	2✔
481	proposal.inputs_mut()[0].witness_utxo = None;	1✔
482	ctx.process_proposal(proposal).unwrap();	1✔
483	}	1✔
484
485	#[test]
486	#[should_panic]
487	fn test_receiver_steals_sender_change() {	1✔
488	let original_psbt = Psbt::from_str(ORIGINAL_PSBT).unwrap();	1✔
489	eprintln!("original: {:#?}", original_psbt);	1✔
490	let ctx = create_psbt_context();	1✔
491	let mut proposal = Psbt::from_str(PAYJOIN_PROPOSAL).unwrap();	1✔
492	eprintln!("proposal: {:#?}", proposal);	1✔
493	for output in proposal.outputs_mut() {	2✔
494	output.bip32_derivation.clear();	2✔
495	}	2✔
496	for input in proposal.inputs_mut() {	2✔
497	input.bip32_derivation.clear();	2✔
498	}	2✔
499	proposal.inputs_mut()[0].witness_utxo = None;	1✔
500	// Steal 0.5 BTC from the sender output and add it to the receiver output	1✔
501	proposal.unsigned_tx.output[0].value -= bitcoin::Amount::from_btc(0.5).unwrap();	1✔
502	proposal.unsigned_tx.output[1].value += bitcoin::Amount::from_btc(0.5).unwrap();	1✔
503	ctx.process_proposal(proposal).unwrap();	1✔
504	}	1✔
505
506	#[test]
507	fn test_disable_output_substitution_query_param() {	1✔
508	let url =	1✔
509	serialize_url(Url::parse("http://localhost").unwrap(), true, None, FeeRate::ZERO, "2")	1✔
510	.unwrap();	1✔
511	assert_eq!(url, Url::parse("http://localhost?v=2&disableoutputsubstitution=true").unwrap());	1✔
512
513	let url =	1✔
514	serialize_url(Url::parse("http://localhost").unwrap(), false, None, FeeRate::ZERO, "2")	1✔
515	.unwrap();	1✔
516	assert_eq!(url, Url::parse("http://localhost?v=2").unwrap());	1✔
517	}	1✔
518	}

payjoin / rust-payjoin / 13350991407

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