blob: a9031c4e15f99f74bfb334df3eb24db60d94101d [file] [log] [blame]
/* Copyright (c) 2023, Google Inc.
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/// Returns true iff `a` and `b` contain the same bytes. It takes an amount of time dependent on the
/// lengths, but independent of the contents of the slices `a` and `b`. The return type is a `bool`,
/// since unlike `memcmp` in C this function cannot be used to put elements into a defined order.
pub fn crypto_memcmp(a: &[u8], b: &[u8]) -> bool {
if a.len() != b.len() {
return false;
}
if a.is_empty() && b.is_empty() {
// Avoid FFI issues with empty slices that may potentially cause UB
return true;
}
// Safety:
// - The lengths of a and b are checked above.
let result =
unsafe { bssl_sys::CRYPTO_memcmp(a.as_ptr() as *const _, b.as_ptr() as *const _, a.len()) };
result == 0
}
#[cfg(test)]
mod test {
use super::*;
#[test]
fn test_different_length() {
assert!(!crypto_memcmp(&[0, 1, 2], &[0]))
}
#[test]
fn test_same_length_different_content() {
assert!(!crypto_memcmp(&[0, 1, 2], &[1, 2, 3]))
}
#[test]
fn test_same_content() {
assert!(crypto_memcmp(&[0, 1, 2], &[0, 1, 2]))
}
#[test]
fn test_empty_slices() {
assert!(crypto_memcmp(&[], &[]))
}
#[test]
fn test_empty_slices_different() {
assert!(!crypto_memcmp(&[], &[0, 1, 2]))
}
}