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Fix direct execute calldata parsing (#9) #60

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Fix direct execute calldata parsing (#9) #60

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148 changes: 125 additions & 23 deletions crates/paymaster-execution/src/execution/execute.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -99,35 +99,77 @@ impl ExecutableDirectInvokeParameters {
/// Extract gas transfer from a raw execute_from_outside call
///
/// The execute_from_outside_call has calldata structure:
/// [caller, nonce, execute_after, execute_before, calls_array...]
/// where calls_array is [num_calls, ...encoded_calls]
/// and each call is [to, selector, calldata_len, ...calldata]
/// [caller, nonce..., execute_after, execute_before, calls_len, ...calls, sig_len, sig...]
/// where each call is [to, selector, calldata_len, ...calldata] and the nonce may be one or two felts.
///
/// For non-sponsored transactions, the last call should be a transfer of gas token to the forwarder.
fn find_gas_token_transfer(&self, forwarder: Felt) -> Result<TokenTransfer, Error> {
let calls: Vec<Felt> = self.execute_from_outside_call.calldata.iter().skip(5).cloned().collect();

let decoder = SequentialCalldataDecoder::new(&calls)?;
let last_call = decoder.last().ok_or(Error::InvalidTypedData)?;

// Validate the last call is a transfer to the forwarder
if last_call.selector != selector!("transfer") {
return Err(Error::InvalidTypedData);
fn extract_calls_segment<'a>(calldata: &'a [Felt], calls_len_index: usize) -> Option<&'a [Felt]> {
let calls_len_felt = calldata.get(calls_len_index)?;
let calls_len: usize = (*calls_len_felt).try_into().ok()?;
if calls_len == 0 {
return None;
}

let mut offset = calls_len_index + 1;
for _ in 0..calls_len {
let length_index = offset.checked_add(2)?;
let length_felt = calldata.get(length_index)?;
let length: usize = (*length_felt).try_into().ok()?;
let next_offset = offset.checked_add(3)?.checked_add(length)?;
if calldata.len() < next_offset {
return None;
}
offset = next_offset;
}

let sig_len_felt = calldata.get(offset)?;
let sig_len: usize = (*sig_len_felt).try_into().ok()?;
let expected_end = offset.checked_add(1)?.checked_add(sig_len)?;
if expected_end != calldata.len() {
return None;
}

calldata.get((calls_len_index + 1)..offset)
}

if last_call.calldata.len() != 3 {
return Err(Error::InvalidTypedData);
let calldata = &self.execute_from_outside_call.calldata;
for calls_len_index in [4usize, 5] {
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@florian-bellotti florian-bellotti Feb 10, 2026

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I think you could refactor this to make it more Rust-idiomatic

let Some(calls) = extract_calls_segment(calldata, calls_len_index) else {
continue;
};
let Ok(decoder) = SequentialCalldataDecoder::new(calls) else {
continue;
};
let Some(last_call) = decoder.last() else {
continue;
};

// Validate the last call is a transfer to the forwarder.
if last_call.selector != selector!("transfer") {
continue;
}

if last_call.calldata.len() != 3 {
continue;
}

let Some(recipient) = last_call.calldata.first() else {
continue;
};

if *recipient != forwarder {
continue;
}

let Some(amount) = last_call.calldata.get(1) else {
continue;
};

return Ok(TokenTransfer::new(last_call.to, forwarder, *amount));
}

let recipient = last_call.calldata.first().ok_or(Error::InvalidTypedData)?;

if *recipient != forwarder {
return Err(Error::InvalidTypedData);
}

let amount = last_call.calldata.get(1).ok_or(Error::InvalidTypedData)?;

Ok(TokenTransfer::new(last_call.to, forwarder, *amount))
Err(Error::InvalidTypedData)
}
}

Expand Down Expand Up @@ -303,7 +345,7 @@ mod tests {
let amount = felt!("0x789");

// Build a simple execute_from_outside call with one user call + gas transfer
// Structure: [caller, nonce, execute_after, execute_before, num_calls, call1..., call2...]
// Structure: [caller, nonce, execute_after, execute_before, num_calls, call1..., call2..., sig_len, sig...]
let calldata = vec![
felt!("0x1"), // caller
felt!("0x2"), // nonce
Expand All @@ -324,6 +366,9 @@ mod tests {
forwarder, // recipient (forwarder)
amount, // amount_low
Felt::ZERO, // amount_high
Felt::TWO, // signature length
felt!("0xDEAD"), // signature part 1
felt!("0xBEEF"), // signature part 2
];

let parameters = ExecutableDirectInvokeParameters {
Expand All @@ -344,6 +389,57 @@ mod tests {
assert_eq!(transfer.amount(), amount);
}

#[test]
fn extract_gas_transfer_from_raw_call_v3_with_signature_works() {
let forwarder = felt!("0x123");
let token = felt!("0x456");
let amount = felt!("0x789");

// Structure: [caller, nonce_low, nonce_high, execute_after, execute_before, num_calls, call1..., call2..., sig_len, sig...]
let calldata = vec![
felt!("0x1"), // caller
felt!("0x2"), // nonce_low
felt!("0x3"), // nonce_high
felt!("0x4"), // execute_after
felt!("0x5"), // execute_before
Felt::TWO, // num_calls = 2
// First call (user's transfer)
felt!("0xAAA"), // to
selector!("transfer"), // selector
Felt::THREE, // calldata_len
felt!("0xBBB"), // recipient
felt!("0xCCC"), // amount_low
Felt::ZERO, // amount_high
// Second call (gas transfer to forwarder)
token, // to (token address)
selector!("transfer"), // selector
Felt::THREE, // calldata_len
forwarder, // recipient (forwarder)
amount, // amount_low
Felt::ZERO, // amount_high
Felt::TWO, // signature length
felt!("0xDEAD"), // signature part 1
felt!("0xBEEF"), // signature part 2
];

let parameters = ExecutableDirectInvokeParameters {
user: Felt::ZERO,
execute_from_outside_call: Call {
to: felt!("0x999"),
selector: selector!("execute_from_outside_v3"),
calldata,
},
};

let result = parameters.find_gas_token_transfer(forwarder);
assert!(result.is_ok());

let transfer = result.unwrap();
assert_eq!(transfer.token(), token);
assert_eq!(transfer.recipient(), forwarder);
assert_eq!(transfer.amount(), amount);
}

#[test]
fn extract_gas_transfer_fails_when_last_call_not_transfer() {
let forwarder = felt!("0x123");
Expand All @@ -361,6 +457,9 @@ mod tests {
forwarder, // recipient
felt!("0x789"), // amount_low
Felt::ZERO, // amount_high
Felt::TWO, // signature length
felt!("0xDEAD"), // signature part 1
felt!("0xBEEF"), // signature part 2
];

let parameters = ExecutableDirectInvokeParameters {
Expand Down Expand Up @@ -394,6 +493,9 @@ mod tests {
wrong_recipient, // wrong recipient
felt!("0xAAA"), // amount_low
Felt::ZERO, // amount_high
Felt::TWO, // signature length
felt!("0xDEAD"), // signature part 1
felt!("0xBEEF"), // signature part 2
];

let parameters = ExecutableDirectInvokeParameters {
Expand Down
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