feat(applying): add remaining validations for Byron era (#325)

pallas-applying/Cargo.toml

@@ -13,8 +13,12 @@ authors = ["Maico Leberle <[email protected]>"]
 doctest = false
 
 [dependencies]
+pallas-addresses = { path = "../pallas-addresses" }
 pallas-codec = { path = "../pallas-codec" }
 pallas-crypto = { path = "../pallas-crypto" }
 pallas-primitives = { path = "../pallas-primitives" }
 pallas-traverse = { path = "../pallas-traverse" }
 rand = "0.8"
+
+[dev-dependencies]
+hex = "0.4"

pallas-applying/src/byron.rs

@@ -1,19 +1,43 @@
 //! Utilities required for Byron-era transaction validation.
 
-use crate::types::{ByronProtParams, MultiEraInput, UTxOs, ValidationError, ValidationResult};
+use std::borrow::Cow;
 
-use pallas_primitives::byron::{MintedTxPayload, Tx};
+use crate::types::{
+    ByronProtParams, MultiEraInput, MultiEraOutput, SigningTag, UTxOs, ValidationError,
+    ValidationResult,
+};
+
+use pallas_addresses::byron::{
+    AddrAttrs, AddrType, AddressId, AddressPayload, ByronAddress, SpendingData,
+};
+use pallas_codec::{
+    minicbor::{encode, Encoder},
+    utils::CborWrap,
+};
+use pallas_crypto::{
+    hash::Hash,
+    key::ed25519::{PublicKey, Signature},
+};
+use pallas_primitives::byron::{
+    Address, MintedTxPayload, PubKey, Signature as ByronSignature, Twit, Tx, TxIn, TxOut,
+};
+use pallas_traverse::OriginalHash;
 
-// TODO: implement missing validation rules.
 pub fn validate_byron_tx(
     mtxp: &MintedTxPayload,
     utxos: &UTxOs,
-    _prot_pps: &ByronProtParams,
+    prot_pps: &ByronProtParams,
+    prot_magic: &u32,
 ) -> ValidationResult {
     let tx: &Tx = &mtxp.transaction;
+    let size: u64 = get_tx_size(tx)?;
     check_ins_not_empty(tx)?;
     check_outs_not_empty(tx)?;
-    check_ins_in_utxos(tx, utxos)
+    check_ins_in_utxos(tx, utxos)?;
+    check_outs_have_lovelace(tx)?;
+    check_fees(tx, &size, utxos, prot_pps)?;
+    check_size(&size, prot_pps)?;
+    check_witnesses(mtxp, utxos, prot_magic)
 }
 
 fn check_ins_not_empty(tx: &Tx) -> ValidationResult {
@@ -38,3 +62,192 @@ fn check_ins_in_utxos(tx: &Tx, utxos: &UTxOs) -> ValidationResult {
     }
     Ok(())
 }
+
+fn check_outs_have_lovelace(tx: &Tx) -> ValidationResult {
+    for output in tx.outputs.iter() {
+        if output.amount == 0 {
+            return Err(ValidationError::OutputWithoutLovelace);
+        }
+    }
+    Ok(())
+}
+
+fn check_fees(tx: &Tx, size: &u64, utxos: &UTxOs, prot_pps: &ByronProtParams) -> ValidationResult {
+    let mut inputs_balance: u64 = 0;
+    for input in tx.inputs.iter() {
+        match utxos
+            .get(&MultiEraInput::from_byron(input))
+            .and_then(MultiEraOutput::as_byron)
+        {
+            Some(byron_utxo) => inputs_balance += byron_utxo.amount,
+            None => return Err(ValidationError::UnableToComputeFees),
+        }
+    }
+    let mut outputs_balance: u64 = 0;
+    for output in tx.outputs.iter() {
+        outputs_balance += output.amount
+    }
+    let total_balance: u64 = inputs_balance - outputs_balance;
+    let min_fees: u64 = prot_pps.min_fees_const + prot_pps.min_fees_factor * size;
+    if total_balance < min_fees {
+        return Err(ValidationError::FeesBelowMin);
+    }
+    Ok(())
+}
+
+fn check_size(size: &u64, prot_pps: &ByronProtParams) -> ValidationResult {
+    if *size > prot_pps.max_tx_size {
+        return Err(ValidationError::MaxTxSizeExceeded);
+    }
+    Ok(())
+}
+
+fn get_tx_size(tx: &Tx) -> Result<u64, ValidationError> {
+    let mut buff: Vec<u8> = Vec::new();
+    match encode(tx, &mut buff) {
+        Ok(()) => Ok(buff.len() as u64),
+        Err(_) => Err(ValidationError::UnknownTxSize),
+    }
+}
+
+pub enum TaggedSignature<'a> {
+    PkWitness(&'a ByronSignature),
+    RedeemWitness(&'a ByronSignature),
+}
+
+fn check_witnesses(mtxp: &MintedTxPayload, utxos: &UTxOs, prot_magic: &u32) -> ValidationResult {
+    let tx: &Tx = &mtxp.transaction;
+    let tx_hash: Hash<32> = mtxp.transaction.original_hash();
+    let witnesses: Vec<(&PubKey, TaggedSignature)> = tag_witnesses(&mtxp.witness)?;
+    let tx_inputs: &Vec<TxIn> = &tx.inputs;
+    for input in tx_inputs {
+        let tx_out: &TxOut = find_tx_out(input, utxos)?;
+        let (pub_key, sign): (&PubKey, &TaggedSignature) = find_raw_witness(tx_out, &witnesses)?;
+        let public_key: PublicKey = get_verification_key(pub_key);
+        let data_to_verify: Vec<u8> = get_data_to_verify(sign, prot_magic, &tx_hash)?;
+        let signature: Signature = get_signature(sign);
+        if !public_key.verify(data_to_verify, &signature) {
+            return Err(ValidationError::WrongSignature);
+        }
+    }
+    Ok(())
+}
+
+fn tag_witnesses(wits: &[Twit]) -> Result<Vec<(&PubKey, TaggedSignature)>, ValidationError> {
+    let mut res: Vec<(&PubKey, TaggedSignature)> = Vec::new();
+    for wit in wits.iter() {
+        match wit {
+            Twit::PkWitness(CborWrap((pk, sig))) => {
+                res.push((pk, TaggedSignature::PkWitness(sig)));
+            }
+            Twit::RedeemWitness(CborWrap((pk, sig))) => {
+                res.push((pk, TaggedSignature::RedeemWitness(sig)));
+            }
+            _ => return Err(ValidationError::UnableToProcessWitnesses),
+        }
+    }
+    Ok(res)
+}
+
+fn find_tx_out<'a>(input: &'a TxIn, utxos: &'a UTxOs) -> Result<&'a TxOut, ValidationError> {
+    let key: MultiEraInput = MultiEraInput::Byron(Box::new(Cow::Borrowed(input)));
+    utxos
+        .get(&key)
+        .ok_or(ValidationError::InputMissingInUTxO)?
+        .as_byron()
+        .ok_or(ValidationError::InputMissingInUTxO)
+}
+
+fn find_raw_witness<'a>(
+    tx_out: &TxOut,
+    witnesses: &'a Vec<(&'a PubKey, TaggedSignature<'a>)>,
+) -> Result<(&'a PubKey, &'a TaggedSignature<'a>), ValidationError> {
+    let address: ByronAddress = mk_byron_address(&tx_out.address);
+    let addr_payload: AddressPayload = address
+        .decode()
+        .map_err(|_| ValidationError::UnableToProcessWitnesses)?;
+    let root: AddressId = addr_payload.root;
+    let attr: AddrAttrs = addr_payload.attributes;
+    let addr_type: AddrType = addr_payload.addrtype;
+    for (pub_key, sign) in witnesses {
+        if redeems(pub_key, sign, &root, &attr, &addr_type) {
+            match addr_type {
+                AddrType::PubKey | AddrType::Redeem => return Ok((pub_key, sign)),
+                _ => return Err(ValidationError::UnableToProcessWitnesses),
+            }
+        }
+    }
+    Err(ValidationError::MissingWitness)
+}
+
+fn mk_byron_address(addr: &Address) -> ByronAddress {
+    ByronAddress::new((*addr.payload.0).as_slice(), addr.crc)
+}
+
+fn redeems(
+    pub_key: &PubKey,
+    sign: &TaggedSignature,
+    root: &AddressId,
+    attrs: &AddrAttrs,
+    addr_type: &AddrType,
+) -> bool {
+    let spending_data: SpendingData = mk_spending_data(pub_key, addr_type);
+    let hash_to_check: AddressId =
+        AddressPayload::hash_address_id(addr_type, &spending_data, attrs);
+    hash_to_check == *root && convert_to_addr_type(sign) == *addr_type
+}
+
+fn convert_to_addr_type(sign: &TaggedSignature) -> AddrType {
+    match sign {
+        TaggedSignature::PkWitness(_) => AddrType::PubKey,
+        TaggedSignature::RedeemWitness(_) => AddrType::Redeem,
+    }
+}
+
+fn mk_spending_data(pub_key: &PubKey, addr_type: &AddrType) -> SpendingData {
+    match addr_type {
+        AddrType::PubKey => SpendingData::PubKey(pub_key.clone()),
+        AddrType::Redeem => SpendingData::Redeem(pub_key.clone()),
+        _ => unreachable!(),
+    }
+}
+
+fn get_verification_key(pk: &PubKey) -> PublicKey {
+    let mut trunc_len: [u8; PublicKey::SIZE] = [0; PublicKey::SIZE];
+    trunc_len.copy_from_slice(&pk.as_slice()[0..PublicKey::SIZE]);
+    From::<[u8; PublicKey::SIZE]>::from(trunc_len)
+}
+
+fn get_data_to_verify(
+    sign: &TaggedSignature,
+    prot_magic: &u32,
+    tx_hash: &Hash<32>,
+) -> Result<Vec<u8>, ValidationError> {
+    let buff: &mut Vec<u8> = &mut Vec::new();
+    let mut enc: Encoder<&mut Vec<u8>> = Encoder::new(buff);
+    match sign {
+        TaggedSignature::PkWitness(_) => {
+            enc.encode(SigningTag::Tx as u64)
+                .map_err(|_| ValidationError::UnableToProcessWitnesses)?;
+        }
+        TaggedSignature::RedeemWitness(_) => {
+            enc.encode(SigningTag::RedeemTx as u64)
+                .map_err(|_| ValidationError::UnableToProcessWitnesses)?;
+        }
+    }
+    enc.encode(prot_magic)
+        .map_err(|_| ValidationError::UnableToProcessWitnesses)?;
+    enc.encode(tx_hash)
+        .map_err(|_| ValidationError::UnableToProcessWitnesses)?;
+    Ok(enc.into_writer().clone())
+}
+
+fn get_signature(tagged_signature: &TaggedSignature<'_>) -> Signature {
+    let inner_sig = match tagged_signature {
+        TaggedSignature::PkWitness(sign) => sign,
+        TaggedSignature::RedeemWitness(sign) => sign,
+    };
+    let mut trunc_len: [u8; Signature::SIZE] = [0; Signature::SIZE];
+    trunc_len.copy_from_slice(inner_sig.as_slice());
+    From::<[u8; Signature::SIZE]>::from(trunc_len)
+}

pallas-applying/src/lib.rs

@@ -7,17 +7,17 @@ use byron::validate_byron_tx;
 
 use pallas_traverse::{MultiEraTx, MultiEraTx::Byron as ByronTxPayload};
 
-pub use types::{
-    MultiEraProtParams, MultiEraProtParams::Byron as ByronProtParams, UTxOs, ValidationResult,
-};
+pub use types::{Environment, MultiEraProtParams, UTxOs, ValidationResult};
 
-pub fn validate(
-    metx: &MultiEraTx,
-    utxos: &UTxOs,
-    prot_pps: &MultiEraProtParams,
-) -> ValidationResult {
-    match (metx, prot_pps) {
-        (ByronTxPayload(mtxp), ByronProtParams(bpp)) => validate_byron_tx(mtxp, utxos, bpp),
+pub fn validate(metx: &MultiEraTx, utxos: &UTxOs, env: &Environment) -> ValidationResult {
+    match (metx, env) {
+        (
+            ByronTxPayload(mtxp),
+            Environment {
+                prot_params: MultiEraProtParams::Byron(bpp),
+                prot_magic,
+            },
+        ) => validate_byron_tx(mtxp, utxos, bpp, prot_magic),
         // TODO: implement the rest of the eras.
         _ => Ok(()),
     }

pallas-applying/src/types.rs

@@ -1,29 +1,51 @@
 //! Base types used for validating transactions in each era.
 
-use std::{borrow::Cow, collections::HashMap};
+use std::collections::HashMap;
 
 pub use pallas_traverse::{MultiEraInput, MultiEraOutput};
 
 pub type UTxOs<'b> = HashMap<MultiEraInput<'b>, MultiEraOutput<'b>>;
 
-// TODO: add a field for each protocol parameter in the Byron era.
 #[derive(Debug, Clone)]
-pub struct ByronProtParams;
+pub struct ByronProtParams {
+    pub min_fees_const: u64,
+    pub min_fees_factor: u64,
+    pub max_tx_size: u64,
+}
 
 // TODO: add variants for the other eras.
 #[derive(Debug)]
 #[non_exhaustive]
-pub enum MultiEraProtParams<'b> {
-    Byron(Box<Cow<'b, ByronProtParams>>),
+pub enum MultiEraProtParams {
+    Byron(ByronProtParams),
+}
+
+#[derive(Debug)]
+pub struct Environment {
+    pub prot_params: MultiEraProtParams,
+    pub prot_magic: u32,
+}
+
+#[non_exhaustive]
+pub enum SigningTag {
+    Tx = 0x01,
+    RedeemTx = 0x02,
 }
 
-// TODO: replace this generic variant with validation-rule-specific ones.
 #[derive(Debug)]
 #[non_exhaustive]
 pub enum ValidationError {
     InputMissingInUTxO,
     TxInsEmpty,
     TxOutsEmpty,
+    OutputWithoutLovelace,
+    UnknownTxSize,
+    UnableToComputeFees,
+    FeesBelowMin,
+    MaxTxSizeExceeded,
+    UnableToProcessWitnesses,
+    MissingWitness,
+    WrongSignature,
 }
 
 pub type ValidationResult = Result<(), ValidationError>;

pallas-applying/tests/README.md

@@ -0,0 +1,20 @@
+# Testing framework documentation
+
+## Execution
+Starting at the root of the repository, simply go to *pallas-applying* and run `cargo test`.
+
+
+## Explanations
+*pallas-applying/tests/byron.rs* contains multiple unit tests for validation on the Byron era.
+
+The first one, **suceessful_mainnet_tx**, is a positive unit test. It takes the CBOR of a mainnet transaction. Namely, the one whose hash is `a06e5a0150e09f8983be2deafab9e04afc60d92e7110999eb672c903343f1e26`, which can be viewed on Cardano Explorer [here](https://cexplorer.io/tx/a06e5a0150e09f8983be2deafab9e04afc60d92e7110999eb672c903343f1e26). Such a transaction has a single input which is added to the UTxO, prior to validation, by associating it to a transaction output sitting at its real (mainnet) address. This information was taken from Cardano Explorer as well, following the address link of the only input to the transaction, and taking its raw address CBOR content.
+
+Then comes a series of negative unit tests, namely:
+- **empty_ins** takes the mainnet transaction, removes its input, and calls validation on it.
+- **empty_outs** is analogous to the **empty_ins** test, removing all outputs instead.
+- **unfound_utxo** takes the mainnet transaction and calls validation on it without a proper UTxO containing an entry for its input.
+- **output_without_lovelace** takes the mainnet transaction and modifies its output by removing all of its lovelace.
+- **not_enough_fees** takes the mainnet transaction and calls validation on it using wrong protocol parameters, which requiere that the transaction pay a higher fee than the one actually paid.
+- **tx_size_exceeds_max** takes the mainnet transaction and calls validation on it using wrong protocol parameters, which only allow transactions of a size smaller than that of the transaction.
+- **missing_witness** takes the mainnet transaction, removes its witness, and calls validation on it.
+- **wrong_signature** takes the mainnet transaction, alters the content of its witness, and calls validation on it.