zebra_state/

error.rs

//! Error types for Zebra's state.

use std::{path::PathBuf, sync::Arc};

use chrono::{DateTime, Utc};
use derive_new::new;
use thiserror::Error;

use tokio::sync::broadcast::error::RecvError;
use zebra_chain::{
    amount::{self, NegativeAllowed, NonNegative},
    block,
    history_tree::HistoryTreeError,
    ironwood, orchard, sapling, sprout, transaction, transparent,
    value_balance::{ValueBalance, ValueBalanceError},
    work::difficulty::CompactDifficulty,
};

use crate::{constants::MIN_TRANSPARENT_COINBASE_MATURITY, HashOrHeight, KnownBlock};

/// A wrapper for type erased errors that is itself clonable and implements the
/// Error trait
#[derive(Debug, Error, Clone)]
#[error(transparent)]
pub struct CloneError {
    source: Arc<dyn std::error::Error + Send + Sync + 'static>,
}

impl From<CommitSemanticallyVerifiedError> for CloneError {
    fn from(source: CommitSemanticallyVerifiedError) -> Self {
        let source = Arc::new(source);
        Self { source }
    }
}

impl From<BoxError> for CloneError {
    fn from(source: BoxError) -> Self {
        let source = Arc::from(source);
        Self { source }
    }
}

/// A boxed [`std::error::Error`].
pub type BoxError = Box<dyn std::error::Error + Send + Sync + 'static>;

/// An error describing why opening the finalized state database failed.
///
/// These errors are recoverable open-time failures that the caller can report,
/// as opposed to invariant violations that indicate a bug.
#[derive(Debug, Error)]
#[non_exhaustive]
pub enum StateInitError {
    /// A read-only state was requested, but the configured cache directory is
    /// missing or unreadable.
    ///
    /// A read-only secondary instance must never create the primary's cache
    /// directory, so a missing or unreadable directory is a fatal configuration
    /// error rather than something to be created.
    #[error(
        "cannot open read-only state: cache directory {path:?} is missing or unreadable. \
         Hint: a read-only state requires an existing Zebra cache directory; check that the \
         state cache_dir in the Zebra config points at a running Zebra node's cache directory"
    )]
    ReadOnlyCacheDirUnreadable {
        /// The configured cache directory that could not be read.
        path: PathBuf,
        /// The underlying I/O error returned while reading the directory.
        source: std::io::Error,
    },

    /// A read-only state was requested, but no database exists at the expected
    /// path.
    ///
    /// A read-only secondary instance cannot create a database, so the absence
    /// of an existing database is a fatal configuration error.
    #[error(
        "cannot open read-only state: no database found at {path:?}. \
         Hint: a read-only state requires an existing finalized database created by a running \
         Zebra node; check that the state cache_dir in the Zebra config points at that node's \
         cache directory"
    )]
    ReadOnlyDatabaseNotFound {
        /// The database path at which no database was found.
        path: PathBuf,
    },

    /// A read-only state was requested together with an ephemeral database.
    ///
    /// A read-only secondary follows another process's primary database and must
    /// never delete it, whereas an ephemeral database deletes its files on drop. The
    /// two are mutually exclusive, so requesting both is a fatal configuration error.
    #[error(
        "cannot open read-only state: an ephemeral database was also requested. \
         Hint: a read-only state follows an existing Zebra node's database and must not \
         delete it; set `ephemeral = false`, or do not request a read-only state"
    )]
    ReadOnlyEphemeralConflict,
}

/// An error describing why a block could not be queued to be committed to the state.
#[derive(Debug, Error, Clone, PartialEq, Eq, new)]
pub enum CommitBlockError {
    #[error("block hash is a duplicate: already in {location}")]
    /// The block is a duplicate: it is already queued or committed in the state.
    Duplicate {
        /// Hash or height of the duplicated block.
        hash_or_height: Option<HashOrHeight>,
        /// Location in the state where the block can be found.
        location: KnownBlock,
    },

    /// Contextual validation failed.
    #[error("could not contextually validate semantically verified block")]
    ValidateContextError(#[from] Box<ValidateContextError>),

    /// The write task exited (likely during shutdown).
    #[error("block commit task exited. Is Zebra shutting down?")]
    #[non_exhaustive]
    WriteTaskExited,
}

impl CommitBlockError {
    /// Returns `true` if this is definitely a duplicate commit request.
    /// Some duplicate requests might not be detected, and therefore return `false`.
    pub fn is_duplicate_request(&self) -> bool {
        matches!(self, CommitBlockError::Duplicate { .. })
    }

    /// Returns `true` if the block's authorizing data doesn't match the commitment in
    /// its header.
    ///
    /// See [`ValidateContextError::is_auth_commitment_mismatch()`] for why this is
    /// tracked separately from the misbehaviour score: the served body is invalid, but
    /// the block hash is still valid and still wanted, so the syncer re-requests it
    /// instead of restarting the sync round.
    pub fn is_auth_commitment_mismatch(&self) -> bool {
        match self {
            CommitBlockError::ValidateContextError(err) => err.is_auth_commitment_mismatch(),
            CommitBlockError::Duplicate { .. } | CommitBlockError::WriteTaskExited => false,
        }
    }

    /// Returns `true` if the block was rejected only because an ancestor's authorizing
    /// data didn't match the commitment in its header.
    ///
    /// See [`ValidateContextError::is_descendant_of_auth_commitment_mismatch()`].
    pub fn is_descendant_of_auth_commitment_mismatch(&self) -> bool {
        match self {
            CommitBlockError::ValidateContextError(err) => {
                err.is_descendant_of_auth_commitment_mismatch()
            }
            CommitBlockError::Duplicate { .. } | CommitBlockError::WriteTaskExited => false,
        }
    }

    /// Returns a suggested misbehaviour score increment for a certain error.
    ///
    /// Consensus-invalid subsidies and authorizing-data commitments score 100.
    /// Duplicate requests, shutdowns, and rejected-ancestor descendants score 0.
    pub fn misbehavior_score(&self) -> u32 {
        match self {
            CommitBlockError::ValidateContextError(err) => err.misbehavior_score(),
            CommitBlockError::Duplicate { .. } | CommitBlockError::WriteTaskExited => 0,
        }
    }
}

/// An error describing why a `CommitSemanticallyVerified` request failed.
#[derive(Debug, Error, Clone, PartialEq, Eq)]
#[error("could not commit semantically-verified block")]
pub struct CommitSemanticallyVerifiedError(#[from] CommitBlockError);

impl CommitSemanticallyVerifiedError {
    /// Returns the [`CommitBlockError`] describing why the commit failed.
    pub fn inner(&self) -> &CommitBlockError {
        &self.0
    }
}

impl From<ValidateContextError> for CommitSemanticallyVerifiedError {
    fn from(value: ValidateContextError) -> Self {
        Self(CommitBlockError::ValidateContextError(Box::new(value)))
    }
}

#[derive(Debug, Error)]
pub enum LayeredStateError<E: std::error::Error + std::fmt::Display> {
    #[error("{0}")]
    State(E),
    #[error("{0}")]
    Layer(BoxError),
}

impl<E: std::error::Error + 'static> From<BoxError> for LayeredStateError<E> {
    fn from(err: BoxError) -> Self {
        match err.downcast::<E>() {
            Ok(state_err) => Self::State(*state_err),
            Err(layer_error) => Self::Layer(layer_error),
        }
    }
}

/// An error describing why a `CommitCheckpointVerifiedBlock` request failed.
#[derive(Debug, Error, Clone)]
#[error("could not commit checkpoint-verified block")]
pub struct CommitCheckpointVerifiedError(#[from] CommitBlockError);

impl CommitCheckpointVerifiedError {
    /// Returns the [`CommitBlockError`] describing why the commit failed.
    pub fn inner(&self) -> &CommitBlockError {
        &self.0
    }
}

impl From<ValidateContextError> for CommitCheckpointVerifiedError {
    fn from(value: ValidateContextError) -> Self {
        Self(CommitBlockError::ValidateContextError(Box::new(value)))
    }
}

/// An error describing why a `InvalidateBlock` request failed.
#[derive(Debug, Error)]
#[non_exhaustive]
pub enum InvalidateError {
    /// The state is currently checkpointing blocks and cannot accept invalidation requests.
    #[error("cannot invalidate blocks while still committing checkpointed blocks")]
    ProcessingCheckpointedBlocks,

    /// Sending the invalidate request to the block write task failed.
    #[error("failed to send invalidate block request to block write task")]
    SendInvalidateRequestFailed,

    /// The invalidate request was dropped before processing.
    #[error("invalidate block request was unexpectedly dropped")]
    InvalidateRequestDropped,

    /// The block hash was not found in any non-finalized chain.
    #[error("block hash {0} not found in any non-finalized chain")]
    BlockNotFound(block::Hash),

    /// Invalidating this root would remove the only non-finalized chain.
    #[error("cannot invalidate block {0}: it is the root of the only non-finalized chain")]
    OnlyChainRoot(block::Hash),
}

/// An error describing why a `ReconsiderBlock` request failed.
#[derive(Debug, Error)]
#[non_exhaustive]
pub enum ReconsiderError {
    /// The block is not found in the list of invalidated blocks.
    #[error("Block with hash {0} was not previously invalidated")]
    MissingInvalidatedBlock(block::Hash),

    /// The block's parent is missing from the non-finalized state.
    #[error("Parent chain not found for block {0}")]
    ParentChainNotFound(block::Hash),

    /// There were no invalidated blocks when at least one was expected.
    #[error("Invalidated blocks list is empty when it should contain at least one block")]
    InvalidatedBlocksEmpty,

    /// The state is currently checkpointing blocks and cannot accept reconsider requests.
    #[error("cannot reconsider blocks while still committing checkpointed blocks")]
    CheckpointCommitInProgress,

    /// Sending the reconsider request to the block write task failed.
    #[error("failed to send reconsider block request to block write task")]
    ReconsiderSendFailed,

    /// The reconsider request was dropped before processing.
    #[error("reconsider block request was unexpectedly dropped")]
    ReconsiderResponseDropped,

    /// Replaying an invalidated block into the restored chain failed contextual
    /// validation.
    #[error("replaying a previously invalidated block failed contextual validation: {0}")]
    ReplayFailed(#[source] ValidateContextError),
}

/// An error describing why an `AwaitUtxo` request failed.
#[derive(Debug, Error)]
#[non_exhaustive]
pub enum AwaitUtxoError {
    /// The state stopped responding, for example because it was dropped
    /// during shutdown, before the UTXO could be found.
    #[error("the state stopped responding before the UTXO arrived")]
    Cancelled,

    /// An internal channel error occurred while waiting for the UTXO.
    #[error("internal channel error while waiting for the UTXO: receiver lagged by {0}")]
    Lagged(u64),

    /// The `ReadStateService` returned an error while looking up the UTXO.
    #[error("the read state service returned an error: {0}")]
    ReadStateFailed(#[source] BoxError),
}

impl From<RecvError> for AwaitUtxoError {
    fn from(err: RecvError) -> Self {
        match err {
            RecvError::Closed => AwaitUtxoError::Cancelled,
            RecvError::Lagged(skipped) => AwaitUtxoError::Lagged(skipped),
        }
    }
}

/// An error describing why a block failed contextual validation.
#[derive(Debug, Error, Clone, PartialEq, Eq)]
#[non_exhaustive]
#[allow(missing_docs)]
pub enum ValidateContextError {
    #[error("block hash {block_hash} was previously invalidated")]
    #[non_exhaustive]
    BlockPreviouslyInvalidated { block_hash: block::Hash },

    #[error("block parent not found in any chain, or not enough blocks in chain")]
    #[non_exhaustive]
    NotReadyToBeCommitted,

    #[error("block height {candidate_height:?} is lower than the current finalized height {finalized_tip_height:?}")]
    #[non_exhaustive]
    OrphanedBlock {
        candidate_height: block::Height,
        finalized_tip_height: block::Height,
    },

    #[error("block height {candidate_height:?} is not one greater than its parent block's height {parent_height:?}")]
    #[non_exhaustive]
    NonSequentialBlock {
        candidate_height: block::Height,
        parent_height: block::Height,
    },

    #[error("block time {candidate_time:?} is less than or equal to the median-time-past for the block {median_time_past:?}")]
    #[non_exhaustive]
    TimeTooEarly {
        candidate_time: DateTime<Utc>,
        median_time_past: DateTime<Utc>,
    },

    #[error("block time {candidate_time:?} is greater than the median-time-past for the block plus 90 minutes {block_time_max:?}")]
    #[non_exhaustive]
    TimeTooLate {
        candidate_time: DateTime<Utc>,
        block_time_max: DateTime<Utc>,
    },

    #[error("block difficulty threshold {difficulty_threshold:?} is not equal to the expected difficulty for the block {expected_difficulty:?}")]
    #[non_exhaustive]
    InvalidDifficultyThreshold {
        difficulty_threshold: CompactDifficulty,
        expected_difficulty: CompactDifficulty,
    },

    #[error("transparent double-spend: {outpoint:?} is spent twice in {location:?}")]
    #[non_exhaustive]
    DuplicateTransparentSpend {
        outpoint: transparent::OutPoint,
        location: &'static str,
    },

    #[error("missing transparent output: possible double-spend of {outpoint:?} in {location:?}")]
    #[non_exhaustive]
    MissingTransparentOutput {
        outpoint: transparent::OutPoint,
        location: &'static str,
    },

    #[error("out-of-order transparent spend: {outpoint:?} is created by a later transaction in the same block")]
    #[non_exhaustive]
    EarlyTransparentSpend { outpoint: transparent::OutPoint },

    #[error(
        "unshielded transparent coinbase spend: {outpoint:?} \
         must be spent in a transaction which only has shielded outputs"
    )]
    #[non_exhaustive]
    UnshieldedTransparentCoinbaseSpend { outpoint: transparent::OutPoint },

    #[error(
        "immature transparent coinbase spend: \
        attempt to spend {outpoint:?} at {spend_height:?}, \
        but spends are invalid before {min_spend_height:?}, \
        which is {MIN_TRANSPARENT_COINBASE_MATURITY:?} blocks \
        after it was created at {created_height:?}"
    )]
    #[non_exhaustive]
    ImmatureTransparentCoinbaseSpend {
        outpoint: transparent::OutPoint,
        spend_height: block::Height,
        min_spend_height: block::Height,
        created_height: block::Height,
    },

    #[error("sprout double-spend: duplicate nullifier: {nullifier:?}, in finalized state: {in_finalized_state:?}")]
    #[non_exhaustive]
    DuplicateSproutNullifier {
        nullifier: sprout::Nullifier,
        in_finalized_state: bool,
    },

    #[error("sapling double-spend: duplicate nullifier: {nullifier:?}, in finalized state: {in_finalized_state:?}")]
    #[non_exhaustive]
    DuplicateSaplingNullifier {
        nullifier: sapling::Nullifier,
        in_finalized_state: bool,
    },

    #[error("orchard double-spend: duplicate nullifier: {nullifier:?}, in finalized state: {in_finalized_state:?}")]
    #[non_exhaustive]
    DuplicateOrchardNullifier {
        nullifier: orchard::Nullifier,
        in_finalized_state: bool,
    },

    #[error("ironwood double-spend: duplicate nullifier: {nullifier:?}, in finalized state: {in_finalized_state:?}")]
    #[non_exhaustive]
    DuplicateIronwoodNullifier {
        nullifier: ironwood::Nullifier,
        in_finalized_state: bool,
    },

    #[error(
        "the remaining value in the transparent transaction value pool MUST be nonnegative:\n\
         {amount_error:?},\n\
         {height:?}, index in block: {tx_index_in_block:?}, {transaction_hash:?}"
    )]
    #[non_exhaustive]
    NegativeRemainingTransactionValue {
        amount_error: amount::Error,
        height: block::Height,
        tx_index_in_block: usize,
        transaction_hash: transaction::Hash,
    },

    #[error(
        "error calculating the remaining value in the transaction value pool:\n\
         {amount_error:?},\n\
         {height:?}, index in block: {tx_index_in_block:?}, {transaction_hash:?}"
    )]
    #[non_exhaustive]
    CalculateRemainingTransactionValue {
        amount_error: amount::Error,
        height: block::Height,
        tx_index_in_block: usize,
        transaction_hash: transaction::Hash,
    },

    #[error(
        "error calculating value balances for the remaining value in the transaction value pool:\n\
         {value_balance_error:?},\n\
         {height:?}, index in block: {tx_index_in_block:?}, {transaction_hash:?}"
    )]
    #[non_exhaustive]
    CalculateTransactionValueBalances {
        value_balance_error: ValueBalanceError,
        height: block::Height,
        tx_index_in_block: usize,
        transaction_hash: transaction::Hash,
    },

    #[error(
        "error calculating the block chain value pool change:\n\
         {value_balance_error:?},\n\
         {height:?}, {block_hash:?},\n\
         transactions: {transaction_count:?}, spent UTXOs: {spent_utxo_count:?}"
    )]
    #[non_exhaustive]
    CalculateBlockChainValueChange {
        value_balance_error: ValueBalanceError,
        height: block::Height,
        block_hash: block::Hash,
        transaction_count: usize,
        spent_utxo_count: usize,
    },

    #[error(
        "error adding value balances to the chain value pool:\n\
         {value_balance_error:?},\n\
         {chain_value_pools:?},\n\
         {block_value_pool_change:?},\n\
         {height:?}"
    )]
    #[non_exhaustive]
    AddValuePool {
        value_balance_error: ValueBalanceError,
        chain_value_pools: Box<ValueBalance<NonNegative>>,
        block_value_pool_change: Box<ValueBalance<NegativeAllowed>>,
        height: Option<block::Height>,
    },

    #[error(
        "invalid block subsidy, funding stream, or miner fee payment in block {block_hash:?} at \
         {height:?}: {subsidy_error}"
    )]
    #[non_exhaustive]
    InvalidSubsidy {
        subsidy_error: zebra_chain::parameters::subsidy::CoinbaseTransactionError,
        height: block::Height,
        block_hash: block::Hash,
    },

    #[error("error updating a note commitment tree: {0}")]
    NoteCommitmentTreeError(#[from] zebra_chain::parallel::tree::NoteCommitmentTreeError),

    #[error("error building the history tree: {0}")]
    HistoryTreeError(#[from] Arc<HistoryTreeError>),

    #[error("block contains an invalid commitment: {0}")]
    InvalidBlockCommitment(#[from] block::CommitmentError),

    #[error(
        "unknown Sprout anchor: {anchor:?},\n\
         {height:?}, index in block: {tx_index_in_block:?}, {transaction_hash:?}"
    )]
    #[non_exhaustive]
    UnknownSproutAnchor {
        anchor: sprout::tree::Root,
        height: Option<block::Height>,
        tx_index_in_block: Option<usize>,
        transaction_hash: transaction::Hash,
    },

    #[error(
        "unknown Sapling anchor: {anchor:?},\n\
         {height:?}, index in block: {tx_index_in_block:?}, {transaction_hash:?}"
    )]
    #[non_exhaustive]
    UnknownSaplingAnchor {
        anchor: sapling::tree::Root,
        height: Option<block::Height>,
        tx_index_in_block: Option<usize>,
        transaction_hash: transaction::Hash,
    },

    #[error(
        "unknown Orchard anchor: {anchor:?},\n\
         {height:?}, index in block: {tx_index_in_block:?}, {transaction_hash:?}"
    )]
    #[non_exhaustive]
    UnknownOrchardAnchor {
        anchor: orchard::tree::Root,
        height: Option<block::Height>,
        tx_index_in_block: Option<usize>,
        transaction_hash: transaction::Hash,
    },

    #[error(
        "unknown Ironwood anchor: {anchor:?},\n\
         {height:?}, index in block: {tx_index_in_block:?}, {transaction_hash:?}"
    )]
    #[non_exhaustive]
    UnknownIronwoodAnchor {
        // Ironwood reuses the Orchard tree root type.
        anchor: orchard::tree::Root,
        height: Option<block::Height>,
        tx_index_in_block: Option<usize>,
        transaction_hash: transaction::Hash,
    },

    /// The block was not validated because an ancestor in the same queued chain
    /// failed contextual validation.
    ///
    /// This is a distinct variant, rather than a copy of the ancestor's error, so the
    /// peer that served this block isn't scored or classified for the ancestor's
    /// failure.
    #[error("ancestor block {ancestor_hash} failed contextual validation")]
    #[non_exhaustive]
    AncestorRejected {
        ancestor_hash: block::Hash,
        source: Box<ValidateContextError>,
    },
}

impl ValidateContextError {
    /// Returns `true` if the block's authorizing data doesn't match the commitment in
    /// its header.
    ///
    /// From NU5 onward, the block header hash and merkle root don't commit to the
    /// authorizing data, so a peer can serve a forged body for a canonical header
    /// without changing the block hash. A mismatched authorizing data commitment proves
    /// the served body doesn't belong to its header, and an honest peer never serves
    /// such a body, so the serving peer is misbehaving and the hash is still wanted.
    pub fn is_auth_commitment_mismatch(&self) -> bool {
        matches!(
            self,
            ValidateContextError::InvalidBlockCommitment(
                block::CommitmentError::InvalidChainHistoryBlockTxAuthCommitment { .. },
            )
        )
    }

    /// Returns `true` if the block was rejected only because an ancestor's authorizing
    /// data didn't match the commitment in its header.
    ///
    /// The ancestor's served body was forged, but its hash is still wanted, so this
    /// block's hash is still wanted too. The peer that served this block isn't the one
    /// that forged the ancestor, so it must not be scored.
    pub fn is_descendant_of_auth_commitment_mismatch(&self) -> bool {
        matches!(
            self,
            ValidateContextError::AncestorRejected { source, .. }
                if source.is_auth_commitment_mismatch()
        )
    }

    /// Wraps `self`, the error of a rejected ancestor block, into the error for one of
    /// its descendants, so the descendant carries neither the ancestor's misbehaviour
    /// score nor its classification.
    pub fn for_descendant(&self, ancestor_hash: block::Hash) -> Self {
        match self {
            // Keep the original failing ancestor, so deep descendants don't nest errors.
            ValidateContextError::AncestorRejected { .. } => self.clone(),
            _ => ValidateContextError::AncestorRejected {
                ancestor_hash,
                source: Box::new(self.clone()),
            },
        }
    }

    /// Returns a suggested misbehaviour score increment for a certain error.
    pub fn misbehavior_score(&self) -> u32 {
        match self {
            // A forged body proves the serving peer misbehaved, see
            // `is_auth_commitment_mismatch()`.
            ValidateContextError::InvalidBlockCommitment(
                block::CommitmentError::InvalidChainHistoryBlockTxAuthCommitment { .. },
            ) => 100,
            // A wrong block subsidy, funding stream, or miner fee payment is invalid given only
            // the block and its parent, so the peer that sent it is misbehaving.
            ValidateContextError::InvalidSubsidy { .. } => 100,
            _other => 0,
        }
    }
}

impl From<sprout::tree::NoteCommitmentTreeError> for ValidateContextError {
    fn from(value: sprout::tree::NoteCommitmentTreeError) -> Self {
        ValidateContextError::NoteCommitmentTreeError(value.into())
    }
}

/// Trait for creating the corresponding duplicate nullifier error from a nullifier.
pub trait DuplicateNullifierError {
    /// Returns the corresponding duplicate nullifier error for `self`.
    fn duplicate_nullifier_error(&self, in_finalized_state: bool) -> ValidateContextError;
}

impl DuplicateNullifierError for sprout::Nullifier {
    fn duplicate_nullifier_error(&self, in_finalized_state: bool) -> ValidateContextError {
        ValidateContextError::DuplicateSproutNullifier {
            nullifier: *self,
            in_finalized_state,
        }
    }
}

impl DuplicateNullifierError for sapling::Nullifier {
    fn duplicate_nullifier_error(&self, in_finalized_state: bool) -> ValidateContextError {
        ValidateContextError::DuplicateSaplingNullifier {
            nullifier: *self,
            in_finalized_state,
        }
    }
}

impl DuplicateNullifierError for orchard::Nullifier {
    fn duplicate_nullifier_error(&self, in_finalized_state: bool) -> ValidateContextError {
        ValidateContextError::DuplicateOrchardNullifier {
            nullifier: *self,
            in_finalized_state,
        }
    }
}

impl DuplicateNullifierError for ironwood::Nullifier {
    fn duplicate_nullifier_error(&self, in_finalized_state: bool) -> ValidateContextError {
        ValidateContextError::DuplicateIronwoodNullifier {
            nullifier: *self,
            in_finalized_state,
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use zebra_chain::block::Height;

    #[test]
    fn commit_block_error_misbehavior_scores() {
        let context_err = CommitBlockError::ValidateContextError(Box::new(
            ValidateContextError::NonSequentialBlock {
                candidate_height: Height(5),
                parent_height: Height(3),
            },
        ));
        assert_eq!(context_err.misbehavior_score(), 0);

        let dup_err = CommitBlockError::Duplicate {
            hash_or_height: None,
            location: KnownBlock::BestChain,
        };
        assert_eq!(dup_err.misbehavior_score(), 0);

        // A mismatched authorizing data commitment means the served body doesn't
        // belong to its header, so the serving peer must be scored.
        let auth_commitment_err = CommitBlockError::ValidateContextError(Box::new(
            ValidateContextError::InvalidBlockCommitment(
                block::CommitmentError::InvalidChainHistoryBlockTxAuthCommitment {
                    expected: [1; 32],
                    actual: [2; 32],
                },
            ),
        ));
        assert_eq!(auth_commitment_err.misbehavior_score(), 100);
    }

    /// The state rejects queued descendants along with a failed block, but the peers that
    /// served them didn't serve the failed block, so they must not inherit its score or
    /// classification.
    #[test]
    fn descendant_errors_are_not_scored() {
        let auth_commitment_err = ValidateContextError::InvalidBlockCommitment(
            block::CommitmentError::InvalidChainHistoryBlockTxAuthCommitment {
                expected: [1; 32],
                actual: [2; 32],
            },
        );
        let forged_hash = block::Hash([1; 32]);

        let child_err = auth_commitment_err.for_descendant(forged_hash);
        assert_eq!(child_err.misbehavior_score(), 0);
        assert!(!child_err.is_auth_commitment_mismatch());
        assert!(child_err.is_descendant_of_auth_commitment_mismatch());

        // Deeper descendants keep pointing at the block that actually failed.
        let grandchild_err = child_err.for_descendant(block::Hash([2; 32]));
        assert_eq!(grandchild_err, child_err);

        let commit_err = CommitBlockError::ValidateContextError(Box::new(child_err));
        assert_eq!(commit_err.misbehavior_score(), 0);
        assert!(!commit_err.is_auth_commitment_mismatch());
        assert!(commit_err.is_descendant_of_auth_commitment_mismatch());

        // Descendants of other contextual failures aren't re-requested.
        let other_child_err = ValidateContextError::NonSequentialBlock {
            candidate_height: Height(5),
            parent_height: Height(3),
        }
        .for_descendant(forged_hash);
        assert_eq!(other_child_err.misbehavior_score(), 0);
        assert!(!other_child_err.is_descendant_of_auth_commitment_mismatch());
    }

    #[test]
    fn invalid_subsidy_commit_error_misbehavior_score() {
        use zebra_chain::parameters::subsidy::{CoinbaseTransactionError, SubsidyError};

        let invalid_subsidy = ValidateContextError::InvalidSubsidy {
            subsidy_error: CoinbaseTransactionError::Subsidy(SubsidyError::InvalidMinerFees),
            height: Height(5),
            block_hash: zebra_chain::block::Hash([0; 32]),
        };
        let descendant = invalid_subsidy.for_descendant(block::Hash([1; 32]));
        assert_eq!(descendant.misbehavior_score(), 0);
        assert!(!descendant.is_descendant_of_auth_commitment_mismatch());
        let subsidy_err = CommitBlockError::ValidateContextError(Box::new(invalid_subsidy));
        assert_eq!(subsidy_err.misbehavior_score(), 100);
    }
}