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Catch possible subtraction error in QUAD_BIT & DI_BIT hints #1185

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merged 4 commits into from
May 29, 2023
Merged

Catch possible subtraction error in QUAD_BIT & DI_BIT hints #1185

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f2b078a
Catch possible sustraction error in QUAD_BIT & DI_BIT hints
fmoletta May 29, 2023
2c9ae6f
Fix changelog entry
fmoletta May 29, 2023
b242702
Typo
fmoletta May 29, 2023
4b2cd40
Fix changelog entry
fmoletta May 29, 2023
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4 changes: 4 additions & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,10 @@

#### Upcoming Changes

* Fix possible subtraction overflow in `QUAD_BIT` & `DI_BIT` hints [#1185](https://github.com/lambdaclass/cairo-rs/pull/1185)

* These hints now return an error when ids.m equals zero

* Add `CairoRunner::run_until_pc_with_steps_limit method` [#1181](https://github.com/lambdaclass/cairo-rs/pull/1181)

* fix: felt_from_number not properly returning parse errors [#1012](https://github.com/lambdaclass/cairo-rs/pull/1012)
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26 changes: 26 additions & 0 deletions src/hint_processor/builtin_hint_processor/secp/ec_utils.rs
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Expand Up @@ -487,6 +487,9 @@ pub fn n_pair_bits(
if m >= 253 {
return insert_value_from_var_name("quad_bit", 0, vm, ids_data, ap_tracking);
}
if m.is_zero() {
return Err(HintError::NPairBitsMZero);
}

let one = &Felt252::one();
let two = &Felt252::from(2);
Expand Down Expand Up @@ -1281,6 +1284,29 @@ mod tests {
check_memory![vm.segments.memory, ((1, 3), 2)];
}

#[test]
fn run_di_bit_m_zero() {
let hint_code = hint_code::DI_BIT;
let mut vm = vm_with_range_check!();

let scalar_u = 0b10101111001110000;
let scalar_v = 0b101101000111011111100;
let m = 0;
// Insert ids.scalar into memory
vm.segments = segments![((1, 0), scalar_u), ((1, 1), scalar_v), ((1, 2), m)];

// Initialize RunContext
run_context!(vm, 0, 4, 4);

let ids_data = ids_data!["scalar_u", "scalar_v", "m", "dibit"];

// Execute the hint
assert_matches!(
run_hint!(vm, ids_data, hint_code),
Err(HintError::NPairBitsMZero)
);
}

#[test]
#[cfg_attr(target_arch = "wasm32", wasm_bindgen_test)]
fn run_import_secp256r1_alpha() {
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2 changes: 2 additions & 0 deletions src/vm/errors/hint_errors.rs
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Expand Up @@ -179,4 +179,6 @@ pub enum HintError {
RecoverYPointNotOnCurve(Felt252),
#[error("Invalid value for {0}. Got: {1}. Expected: {2}")]
InvalidValue(&'static str, Felt252, Felt252),
#[error("Attempt to subtract with overflow: ids.m - 1")]
NPairBitsMZero,
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Maybe we should use a more descriptive name to this new error

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I chose this name as it is more useful when debugging, as it has the name of the function that fails and the failure case, while leaving the error string useful for users, a more descriptive name could be NPairBitsMMinusOneSubtractioOverflow or MMinusOneSubtractionOverflow but it doesn't sound that much useful

}