pirate-librustzcash/zcash_primitives/src/transaction/components.rs

use byteorder::{LittleEndian, ReadBytesExt, WriteBytesExt};
use ff::{PrimeField, PrimeFieldRepr};
use pairing::bls12_381::{Bls12, Fr, FrRepr};
use sapling_crypto::{
    jubjub::{edwards, Unknown},
    redjubjub::{PublicKey, Signature},
};
use std::io::{self, Read, Write};

use serialize::Vector;
use JUBJUB;

// π_A + π_B + π_C
const GROTH_PROOF_SIZE: usize = (48 + 96 + 48);
// π_A + π_A' + π_B + π_B' + π_C + π_C' + π_K + π_H
const PHGR_PROOF_SIZE: usize = (33 + 33 + 65 + 33 + 33 + 33 + 33 + 33);

const ZC_NUM_JS_INPUTS: usize = 2;
const ZC_NUM_JS_OUTPUTS: usize = 2;

const COIN: i64 = 1_0000_0000;
const MAX_MONEY: i64 = 21_000_000 * COIN;

#[derive(Clone, Copy, Debug, PartialEq)]
pub struct Amount(pub i64);

impl Amount {
    // Read an Amount from a signed 64-bit little-endian integer.
    pub fn read_i64<R: Read>(mut reader: R, allow_negative: bool) -> io::Result<Self> {
        let amount = reader.read_i64::<LittleEndian>()?;
        if 0 <= amount && amount <= MAX_MONEY {
            Ok(Amount(amount))
        } else if allow_negative && -MAX_MONEY <= amount && amount < 0 {
            Ok(Amount(amount))
        } else {
            Err(io::Error::new(
                io::ErrorKind::InvalidData,
                if allow_negative {
                    "Amount not in {-MAX_MONEY..MAX_MONEY}"
                } else {
                    "Amount not in {0..MAX_MONEY}"
                },
            ))
        }
    }

    // Read an Amount from an unsigned 64-bit little-endian integer.
    pub fn read_u64<R: Read>(mut reader: R) -> io::Result<Self> {
        let amount = reader.read_u64::<LittleEndian>()?;
        if amount <= MAX_MONEY as u64 {
            Ok(Amount(amount as i64))
        } else {
            Err(io::Error::new(
                io::ErrorKind::InvalidData,
                "Amount not in {0..MAX_MONEY}",
            ))
        }
    }
}

pub struct Script(pub Vec<u8>);

impl Script {
    pub fn read<R: Read>(mut reader: R) -> io::Result<Self> {
        let script = Vector::read(&mut reader, |r| r.read_u8())?;
        Ok(Script(script))
    }

    pub fn write<W: Write>(&self, mut writer: W) -> io::Result<()> {
        Vector::write(&mut writer, &self.0, |w, e| w.write_u8(*e))
    }
}

pub struct OutPoint {
    hash: [u8; 32],
    n: u32,
}

impl OutPoint {
    pub fn read<R: Read>(mut reader: R) -> io::Result<Self> {
        let mut hash = [0; 32];
        reader.read_exact(&mut hash)?;
        let n = reader.read_u32::<LittleEndian>()?;
        Ok(OutPoint { hash, n })
    }

    pub fn write<W: Write>(&self, mut writer: W) -> io::Result<()> {
        writer.write_all(&self.hash)?;
        writer.write_u32::<LittleEndian>(self.n)
    }
}

pub struct TxIn {
    pub prevout: OutPoint,
    script_sig: Script,
    pub sequence: u32,
}

impl TxIn {
    pub fn read<R: Read>(mut reader: &mut R) -> io::Result<Self> {
        let prevout = OutPoint::read(&mut reader)?;
        let script_sig = Script::read(&mut reader)?;
        let sequence = reader.read_u32::<LittleEndian>()?;

        Ok(TxIn {
            prevout,
            script_sig,
            sequence,
        })
    }

    pub fn write<W: Write>(&self, mut writer: W) -> io::Result<()> {
        self.prevout.write(&mut writer)?;
        self.script_sig.write(&mut writer)?;
        writer.write_u32::<LittleEndian>(self.sequence)
    }
}

pub struct TxOut {
    value: Amount,
    script_pubkey: Script,
}

impl TxOut {
    pub fn read<R: Read>(mut reader: &mut R) -> io::Result<Self> {
        let value = Amount::read_i64(&mut reader, false)?;
        let script_pubkey = Script::read(&mut reader)?;

        Ok(TxOut {
            value,
            script_pubkey,
        })
    }

    pub fn write<W: Write>(&self, mut writer: W) -> io::Result<()> {
        writer.write_i64::<LittleEndian>(self.value.0)?;
        self.script_pubkey.write(&mut writer)
    }
}

pub struct SpendDescription {
    pub cv: edwards::Point<Bls12, Unknown>,
    pub anchor: Fr,
    pub nullifier: [u8; 32],
    pub rk: PublicKey<Bls12>,
    pub zkproof: [u8; GROTH_PROOF_SIZE],
    pub spend_auth_sig: Signature,
}

impl SpendDescription {
    pub fn read<R: Read>(mut reader: &mut R) -> io::Result<Self> {
        // Consensus rules (§4.4):
        // - Canonical encoding is enforced here.
        // - "Not small order" is enforced in SaplingVerificationContext::check_spend()
        //   (located in zcash_proofs::sapling::verifier).
        let cv = edwards::Point::<Bls12, Unknown>::read(&mut reader, &JUBJUB)?;

        // Consensus rule (§7.3): Canonical encoding is enforced here
        let anchor = {
            let mut f = FrRepr::default();
            f.read_le(&mut reader)?;
            Fr::from_repr(f).map_err(|e| io::Error::new(io::ErrorKind::InvalidInput, e))?
        };

        let mut nullifier = [0; 32];
        reader.read_exact(&mut nullifier)?;

        // Consensus rules (§4.4):
        // - Canonical encoding is enforced here.
        // - "Not small order" is enforced in SaplingVerificationContext::check_spend()
        let rk = PublicKey::<Bls12>::read(&mut reader, &JUBJUB)?;

        // Consensus rules (§4.4):
        // - Canonical encoding is enforced by the API of SaplingVerificationContext::check_spend()
        //   due to the need to parse this into a bellman::groth16::Proof.
        // - Proof validity is enforced in SaplingVerificationContext::check_spend()
        let mut zkproof = [0; GROTH_PROOF_SIZE];
        reader.read_exact(&mut zkproof)?;

        // Consensus rules (§4.4):
        // - Canonical encoding is enforced here.
        // - Signature validity is enforced in SaplingVerificationContext::check_spend()
        let spend_auth_sig = Signature::read(&mut reader)?;

        Ok(SpendDescription {
            cv,
            anchor,
            nullifier,
            rk,
            zkproof,
            spend_auth_sig,
        })
    }

    pub fn write<W: Write>(&self, mut writer: W) -> io::Result<()> {
        self.cv.write(&mut writer)?;
        self.anchor.into_repr().write_le(&mut writer)?;
        writer.write_all(&self.nullifier)?;
        self.rk.write(&mut writer)?;
        writer.write_all(&self.zkproof)?;
        self.spend_auth_sig.write(&mut writer)
    }
}

pub struct OutputDescription {
    pub cv: edwards::Point<Bls12, Unknown>,
    pub cmu: Fr,
    pub ephemeral_key: edwards::Point<Bls12, Unknown>,
    pub enc_ciphertext: [u8; 580],
    pub out_ciphertext: [u8; 80],
    pub zkproof: [u8; GROTH_PROOF_SIZE],
}

impl OutputDescription {
    pub fn read<R: Read>(mut reader: &mut R) -> io::Result<Self> {
        // Consensus rules (§4.5):
        // - Canonical encoding is enforced here.
        // - "Not small order" is enforced in SaplingVerificationContext::check_output()
        //   (located in zcash_proofs::sapling::verifier).
        let cv = edwards::Point::<Bls12, Unknown>::read(&mut reader, &JUBJUB)?;

        // Consensus rule (§7.4): Canonical encoding is enforced here
        let cmu = {
            let mut f = FrRepr::default();
            f.read_le(&mut reader)?;
            Fr::from_repr(f).map_err(|e| io::Error::new(io::ErrorKind::InvalidInput, e))?
        };

        // Consensus rules (§4.5):
        // - Canonical encoding is enforced here.
        // - "Not small order" is enforced in SaplingVerificationContext::check_output()
        let ephemeral_key = edwards::Point::<Bls12, Unknown>::read(&mut reader, &JUBJUB)?;

        let mut enc_ciphertext = [0; 580];
        let mut out_ciphertext = [0; 80];
        reader.read_exact(&mut enc_ciphertext)?;
        reader.read_exact(&mut out_ciphertext)?;

        // Consensus rules (§4.5):
        // - Canonical encoding is enforced by the API of SaplingVerificationContext::check_output()
        //   due to the need to parse this into a bellman::groth16::Proof.
        // - Proof validity is enforced in SaplingVerificationContext::check_output()
        let mut zkproof = [0; GROTH_PROOF_SIZE];
        reader.read_exact(&mut zkproof)?;

        Ok(OutputDescription {
            cv,
            cmu,
            ephemeral_key,
            enc_ciphertext,
            out_ciphertext,
            zkproof,
        })
    }

    pub fn write<W: Write>(&self, mut writer: W) -> io::Result<()> {
        self.cv.write(&mut writer)?;
        self.cmu.into_repr().write_le(&mut writer)?;
        self.ephemeral_key.write(&mut writer)?;
        writer.write_all(&self.enc_ciphertext)?;
        writer.write_all(&self.out_ciphertext)?;
        writer.write_all(&self.zkproof)
    }
}

enum SproutProof {
    Groth([u8; GROTH_PROOF_SIZE]),
    PHGR([u8; PHGR_PROOF_SIZE]),
}

pub struct JSDescription {
    vpub_old: Amount,
    vpub_new: Amount,
    anchor: [u8; 32],
    nullifiers: [[u8; 32]; ZC_NUM_JS_INPUTS],
    commitments: [[u8; 32]; ZC_NUM_JS_OUTPUTS],
    ephemeral_key: [u8; 32],
    random_seed: [u8; 32],
    macs: [[u8; 32]; ZC_NUM_JS_INPUTS],
    proof: SproutProof,
    ciphertexts: [[u8; 601]; ZC_NUM_JS_OUTPUTS],
}

impl JSDescription {
    pub fn read<R: Read>(mut reader: R, use_groth: bool) -> io::Result<Self> {
        // Consensus rule (§4.3): Canonical encoding is enforced here
        let vpub_old = Amount::read_u64(&mut reader)?;

        // Consensus rule (§4.3): Canonical encoding is enforced here
        let vpub_new = Amount::read_u64(&mut reader)?;

        // Consensus rule (§4.3): One of vpub_old and vpub_new being zero is
        // enforced by CheckTransactionWithoutProofVerification() in zcashd.

        let mut anchor = [0; 32];
        reader.read_exact(&mut anchor)?;

        let mut nullifiers = [[0; 32]; ZC_NUM_JS_INPUTS];
        nullifiers
            .iter_mut()
            .map(|nf| reader.read_exact(nf))
            .collect::<io::Result<()>>()?;

        let mut commitments = [[0; 32]; ZC_NUM_JS_OUTPUTS];
        commitments
            .iter_mut()
            .map(|cm| reader.read_exact(cm))
            .collect::<io::Result<()>>()?;

        // Consensus rule (§4.3): Canonical encoding is enforced by
        // ZCNoteDecryption::decrypt() in zcashd
        let mut ephemeral_key = [0; 32];
        reader.read_exact(&mut ephemeral_key)?;

        let mut random_seed = [0; 32];
        reader.read_exact(&mut random_seed)?;

        let mut macs = [[0; 32]; ZC_NUM_JS_INPUTS];
        macs.iter_mut()
            .map(|mac| reader.read_exact(mac))
            .collect::<io::Result<()>>()?;

        let proof = match use_groth {
            true => {
                // Consensus rules (§4.3):
                // - Canonical encoding is enforced in librustzcash_sprout_verify()
                // - Proof validity is enforced in librustzcash_sprout_verify()
                let mut proof = [0; GROTH_PROOF_SIZE];
                reader.read_exact(&mut proof)?;
                SproutProof::Groth(proof)
            }
            false => {
                // Consensus rules (§4.3):
                // - Canonical encoding is enforced by PHGRProof in zcashd
                // - Proof validity is enforced by JSDescription::Verify() in zcashd
                let mut proof = [0; PHGR_PROOF_SIZE];
                reader.read_exact(&mut proof)?;
                SproutProof::PHGR(proof)
            }
        };

        let mut ciphertexts = [[0; 601]; ZC_NUM_JS_OUTPUTS];
        ciphertexts
            .iter_mut()
            .map(|ct| reader.read_exact(ct))
            .collect::<io::Result<()>>()?;

        Ok(JSDescription {
            vpub_old,
            vpub_new,
            anchor,
            nullifiers,
            commitments,
            ephemeral_key,
            random_seed,
            macs,
            proof,
            ciphertexts,
        })
    }

    pub fn write<W: Write>(&self, mut writer: W) -> io::Result<()> {
        writer.write_i64::<LittleEndian>(self.vpub_old.0)?;
        writer.write_i64::<LittleEndian>(self.vpub_new.0)?;
        writer.write_all(&self.anchor)?;
        writer.write_all(&self.nullifiers[0])?;
        writer.write_all(&self.nullifiers[1])?;
        writer.write_all(&self.commitments[0])?;
        writer.write_all(&self.commitments[1])?;
        writer.write_all(&self.ephemeral_key)?;
        writer.write_all(&self.random_seed)?;
        writer.write_all(&self.macs[0])?;
        writer.write_all(&self.macs[1])?;

        match &self.proof {
            SproutProof::Groth(p) => writer.write_all(p)?,
            SproutProof::PHGR(p) => writer.write_all(p)?,
        }

        writer.write_all(&self.ciphertexts[0])?;
        writer.write_all(&self.ciphertexts[1])
    }
}

#[cfg(test)]
mod tests {
    use super::{Amount, MAX_MONEY};

    #[test]
    fn amount_in_range() {
        let zero = b"\x00\x00\x00\x00\x00\x00\x00\x00";
        assert_eq!(Amount::read_u64(&zero[..]).unwrap(), Amount(0));
        assert_eq!(Amount::read_i64(&zero[..], false).unwrap(), Amount(0));
        assert_eq!(Amount::read_i64(&zero[..], true).unwrap(), Amount(0));

        let neg_one = b"\xff\xff\xff\xff\xff\xff\xff\xff";
        assert!(Amount::read_u64(&neg_one[..]).is_err());
        assert!(Amount::read_i64(&neg_one[..], false).is_err());
        assert_eq!(Amount::read_i64(&neg_one[..], true).unwrap(), Amount(-1));

        let max_money = b"\x00\x40\x07\x5a\xf0\x75\x07\x00";
        assert_eq!(Amount::read_u64(&max_money[..]).unwrap(), Amount(MAX_MONEY));
        assert_eq!(
            Amount::read_i64(&max_money[..], false).unwrap(),
            Amount(MAX_MONEY)
        );
        assert_eq!(
            Amount::read_i64(&max_money[..], true).unwrap(),
            Amount(MAX_MONEY)
        );

        let max_money_p1 = b"\x01\x40\x07\x5a\xf0\x75\x07\x00";
        assert!(Amount::read_u64(&max_money_p1[..]).is_err());
        assert!(Amount::read_i64(&max_money_p1[..], false).is_err());
        assert!(Amount::read_i64(&max_money_p1[..], true).is_err());

        let neg_max_money = b"\x00\xc0\xf8\xa5\x0f\x8a\xf8\xff";
        assert!(Amount::read_u64(&neg_max_money[..]).is_err());
        assert!(Amount::read_i64(&neg_max_money[..], false).is_err());
        assert_eq!(
            Amount::read_i64(&neg_max_money[..], true).unwrap(),
            Amount(-MAX_MONEY)
        );

        let neg_max_money_m1 = b"\xff\xbf\xf8\xa5\x0f\x8a\xf8\xff";
        assert!(Amount::read_u64(&neg_max_money_m1[..]).is_err());
        assert!(Amount::read_i64(&neg_max_money_m1[..], false).is_err());
        assert!(Amount::read_i64(&neg_max_money_m1[..], true).is_err());
    }
}