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fix(zkevm-circuits/begin_tx): add missing constraints #1776

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3 changes: 2 additions & 1 deletion bus-mapping/src/circuit_input_builder/block.rs
Original file line number Diff line number Diff line change
Expand Up @@ -84,7 +84,8 @@ pub struct Block {
pub block_steps: BlockSteps,
/// Copy events in this block.
pub copy_events: Vec<CopyEvent>,
/// Inputs to the SHA3 opcode
/// Inputs to the SHA3 opcode as well as data hashed during the EVM execution like init code
/// and address creation inputs.
pub sha3_inputs: Vec<Vec<u8>>,
/// Exponentiation events in the block.
pub exp_events: Vec<ExpEvent>,
Expand Down
26 changes: 25 additions & 1 deletion bus-mapping/src/evm/opcodes/begin_end_tx.rs
Original file line number Diff line number Diff line change
@@ -1,6 +1,8 @@
use super::TxExecSteps;
use crate::{
circuit_input_builder::{Call, CircuitInputStateRef, ExecState, ExecStep},
circuit_input_builder::{
Call, CircuitInputStateRef, CopyDataType, CopyEvent, ExecState, ExecStep, NumberOrHash,
},
operation::{AccountField, AccountOp, CallContextField, TxReceiptField, TxRefundOp, RW},
state_db::CodeDB,
Error,
Expand Down Expand Up @@ -148,6 +150,28 @@ fn gen_begin_tx_steps(state: &mut CircuitInputStateRef) -> Result<ExecStep, Erro
stream.append(&nonce_prev);
stream.out().to_vec()
});
// We also hash the call_data as it will be used as init code, and the
// call_context.code_hash needs to be checked against the hash of this call_data.
state.block.sha3_inputs.push(state.tx.call_data.to_vec());

// Append the copy for the CopyCircuit to calculate RLC(call_data) for the keccack lookup
if state.tx.call_data.len() > 0 {
state.push_copy(
&mut exec_step,
CopyEvent {
src_addr: 0,
src_addr_end: state.tx.call_data.len() as u64,
src_type: CopyDataType::TxCalldata,
src_id: NumberOrHash::Number(state.tx.id as usize),
dst_addr: 0,
dst_type: CopyDataType::RlcAcc,
dst_id: NumberOrHash::Number(0),
log_id: None,
rw_counter_start: state.block_ctx.rwc,
bytes: state.tx.call_data.iter().map(|b| (*b, false)).collect(),
},
);
}
}

// There are 4 branches from here.
Expand Down
80 changes: 67 additions & 13 deletions zkevm-circuits/src/evm_circuit/execution/begin_tx.rs
Original file line number Diff line number Diff line change
Expand Up @@ -12,21 +12,22 @@ use crate::{
},
is_precompiled,
math_gadget::{
ContractCreateGadget, IsEqualWordGadget, IsZeroWordGadget, RangeCheckGadget,
ContractCreateGadget, IsEqualWordGadget, IsZeroGadget, IsZeroWordGadget,
RangeCheckGadget,
},
not,
not, rlc,
tx::{BeginTxHelperGadget, TxDataGadget},
AccountAddress, CachedRegion, Cell, StepRws,
},
witness::{Block, Call, ExecStep, Transaction},
},
table::{AccountFieldTag, BlockContextFieldTag, CallContextFieldTag},
table::{AccountFieldTag, BlockContextFieldTag, CallContextFieldTag, TxContextFieldTag},
util::{
word::{Word32Cell, WordExpr, WordLoHi, WordLoHiCell},
Expr,
},
};
use bus_mapping::state_db::CodeDB;
use bus_mapping::{circuit_input_builder::CopyDataType, state_db::CodeDB};
use eth_types::{evm_types::PRECOMPILE_COUNT, keccak256, Field, OpsIdentity, ToWord, U256};
use halo2_proofs::{
circuit::Value,
Expand All @@ -45,6 +46,9 @@ pub(crate) struct BeginTxGadget<F> {
code_hash: WordLoHiCell<F>,
is_empty_code_hash: IsEqualWordGadget<F, WordLoHi<Expression<F>>, WordLoHi<Expression<F>>>,
caller_nonce_hash_bytes: Word32Cell<F>,
calldata_length: Cell<F>,
calldata_length_is_zero: IsZeroGadget<F>,
calldata_rlc: Cell<F>,
create: ContractCreateGadget<F, false>,
callee_not_exists: IsZeroWordGadget<F, WordLoHiCell<F>>,
is_caller_callee_equal: Cell<F>,
Expand Down Expand Up @@ -183,12 +187,23 @@ impl<F: Field> ExecutionGadget<F> for BeginTxGadget<F> {
);

let caller_nonce_hash_bytes = cb.query_word32();
let calldata_length = cb.query_cell();
let calldata_length_is_zero = cb.is_zero(calldata_length.expr());
let calldata_rlc = cb.query_cell_phase2();
let create = ContractCreateGadget::construct(cb);
cb.require_equal_word(
"tx caller address equivalence",
tx.caller_address.to_word(),
create.caller_address(),
);

cb.require_equal(
"tx nonce equivalence",
tx.nonce.expr(),
create.caller_nonce(),
);

// 1. Handle contract creation transaction.
cb.condition(tx.is_create.expr(), |cb| {
cb.require_equal_word(
"call callee address equivalence",
Expand All @@ -201,21 +216,45 @@ impl<F: Field> ExecutionGadget<F> for BeginTxGadget<F> {
)
.to_word(),
);
});
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I removed this; before there were two separate cb.condition with the same condition (that tx.is_create). I think we can merge them.
And actually in the #1475 it is stated that we need to check if callee address is equal to keccak(rlp(sender, nonce)) - but we actually have this constraint already, right? - call callee address equivalence constraint and keccak table lookup for caller_nonce_hash_bytes seems to be enough. Am I missing something?

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I think this is needed. Notice that here we're checking against call_callee_address:

cb.require_equal_word(
"call callee address equivalence",
call_callee_address.to_word(),
AccountAddress::<F>::new(
caller_nonce_hash_bytes.limbs[0..N_BYTES_ACCOUNT_ADDRESS]
.to_vec()
.try_into()
.unwrap(),
)
.to_word(),
);

And caller_nonce_hash_bytes is constrained via:

cb.keccak_table_lookup(
create.input_rlc(cb),
create.input_length(),
caller_nonce_hash_bytes.to_word(),
);

which calls:
pub(crate) fn input_rlc(&self, cb: &EVMConstraintBuilder<F>) -> Expression<F> {

Now notice how input_rlc uses:

So we must check that they are correct.

This checks the nonce (your deleted code):

        cb.require_equal(
            "tx nonce equivalence",
            tx.nonce.expr(),
            create.caller_nonce(),
        );

And this checks the address:

cb.require_equal_word(
"tx caller address equivalence",
tx.caller_address.to_word(),
create.caller_address(),
);

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Sorry I just saw that the removed nonce check was moved to

cb.require_equal(
"tx nonce equivalence",
tx.nonce.expr(),
create.caller_nonce(),
);

So I'm a bit confused.

Are you talking about the removal of the nonce check? Or something else?

I think it would be cleaner if all the create fields equality checks are inside the condition:

// 1. Handle contract creation transaction.
cb.condition(tx.is_create.expr(), |cb| {

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There were two cb.condition(tx.is_create.expr()):

cb.condition(tx.is_create.expr(), |cb| {

and the other one:
cb.condition(tx.is_create.expr(), |cb| {

I think it would be cleaner if all the create fields equality checks are inside the condition:
I think that's what I wanted to do as well, that's why I merged them.


But the second thing I asked is do we still need the constraint from here: #1475 (comment)

The callee address of the new context should be the keccak(RLP([sender_address, sender_nonce]))

I think we already have that, right?
cc. @ed255

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There were two cb.condition(tx.is_create.expr()):

cb.condition(tx.is_create.expr(), |cb| {

and the other one:

cb.condition(tx.is_create.expr(), |cb| {

I think it would be cleaner if all the create fields equality checks are inside the condition:
I think that's what I wanted to do as well, that's why I merged them.

Ah, thanks for the clarification! On the constraint level it's the same, but I think in the code level it looks cleaner.

But the second thing I asked is do we still need the constraint from here: #1475 (comment)

The callee address of the new context should be the keccak(RLP([sender_address, sender_nonce]))

I think we already have that, right? cc. @ed255

Ah yes, I see now that this point was already done. I think I just missed this
https://github.com/privacy-scaling-explorations/zkevm-circuits/blob/3bbc757a20d9d9f7759db47c096d5395361bee74/zkevm-circuits/src/evm_circuit/execution/begin_tx.rs#L193C1-L205C12
Due to it being apart from all the logic of the is_create case. So yeah, all is good regarding this point :)

cb.require_equal(
"tx nonce equivalence",
tx.nonce.expr(),
create.caller_nonce(),
);

// 1. Handle contract creation transaction.
cb.condition(tx.is_create.expr(), |cb| {
cb.keccak_table_lookup(
create.input_rlc(cb),
create.input_length(),
caller_nonce_hash_bytes.to_word(),
);

cb.tx_context_lookup(
tx_id.expr(),
TxContextFieldTag::CallDataLength,
None,
WordLoHi::from_lo_unchecked(calldata_length.expr()),
);
// If calldata_length > 0 we use the copy circuit to calculate the calldata_rlc for the
// keccack input.
cb.condition(not::expr(calldata_length_is_zero.expr()), |cb| {
cb.copy_table_lookup(
WordLoHi::from_lo_unchecked(tx_id.expr()),
CopyDataType::TxCalldata.expr(),
WordLoHi::zero(),
CopyDataType::RlcAcc.expr(),
0.expr(),
calldata_length.expr(),
0.expr(),
calldata_length.expr(),
calldata_rlc.expr(),
0.expr(),
)
});
// If calldata_length == 0, the copy circuit will not contain any entry, so we skip the
// lookup and instead force calldata_rlc to be 0 for the keccack input.
cb.condition(calldata_length_is_zero.expr(), |cb| {
cb.require_equal("calldata_rlc = 0", calldata_rlc.expr(), 0.expr());
});
cb.keccak_table_lookup(
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Is this how we should add a constraint for cb.curr.state.code_hash = keccak(tx.calldata)?

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Hm, I don't think this is correct.
The length should be something like this (via lookup to TxTable):

let length = cb.tx_context(tx_id, TxContextFieldTag::CallDataLength, None);

The input should be the rlc of the TxCalldata, which is dynamic length. Take a look at the SHA3 opcode to see how it calculates the keccak of memory:

cb.copy_table_lookup(
WordLoHi::from_lo_unchecked(cb.curr.state.call_id.expr()),
CopyDataType::Memory.expr(),
WordLoHi::from_lo_unchecked(cb.curr.state.call_id.expr()),
CopyDataType::RlcAcc.expr(),
memory_address.offset(),
memory_address.address(),
0.expr(), // dst_addr for CopyDataType::RlcAcc is 0.
memory_address.length(),
rlc_acc.expr(),
copy_rwc_inc.expr(),
);

An then CALLDATACOPY to see how it uses the copy circuit with TxCalldata as input:

And from understanding those you should make a copy event that has TxCalldata as input and RLC as ouput. Something like this:

            let copy_rwc_inc = cb.query_cell();
            let rlc_acc = cb.query_cell_phase2();
            cb.copy_table_lookup(
                WordLoHi::from_lo_unchecked(tx_id.expr()),
                CopyDataType::TxCalldata.expr(),
                WordLoHi::zero(),
                CopyDataType::RlcAcc.expr(),
                zero,
                length, // The TxCalldata length calculated previously
                0.expr(), // dst_addr for CopyDataType::RlcAcc is 0.
                length, // The TxCalldata length calculated previously
                rlc_acc.expr(),
                copy_rwc_inc.expr(),
            );

Now you can use rlc_acc as input to keccak_table_lookup

calldata_rlc.expr(),
calldata_length.expr(),
cb.curr.state.code_hash.to_word(),
);

cb.account_write(
call_callee_address.to_word(),
AccountFieldTag::Nonce,
Expand Down Expand Up @@ -434,6 +473,9 @@ impl<F: Field> ExecutionGadget<F> for BeginTxGadget<F> {
code_hash,
is_empty_code_hash,
caller_nonce_hash_bytes,
calldata_length,
calldata_length_is_zero,
calldata_rlc,
create,
callee_not_exists,
is_caller_callee_equal,
Expand Down Expand Up @@ -522,6 +564,18 @@ impl<F: Field> ExecutionGadget<F> for BeginTxGadget<F> {
offset,
U256::from_big_endian(&untrimmed_contract_addr),
)?;
self.calldata_length.assign(
region,
offset,
Value::known(F::from(tx.call_data.len() as u64)),
)?;
self.calldata_length_is_zero
.assign(region, offset, F::from(tx.call_data.len() as u64))?;
let calldata_rlc = region
.challenges()
.keccak_input()
.map(|randomness| rlc::value(tx.call_data.iter().rev(), randomness));
self.calldata_rlc.assign(region, offset, calldata_rlc)?;
self.create.assign(
region,
offset,
Expand Down
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