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// Copyright 2015-2016 Brian Smith. // // 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 AUTHORS DISCLAIM ALL WARRANTIES // WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF // MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHORS 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. //! Constant-time operations. use crate::{c, error}; /// Returns `Ok(())` if `a == b` and `Err(error::Unspecified)` otherwise. /// The comparison of `a` and `b` is done in constant time with respect to the /// contents of each, but NOT in constant time with respect to the lengths of /// `a` and `b`. pub fn verify_slices_are_equal(a: &[u8], b: &[u8]) -> Result<(), error::Unspecified> { if a.len() != b.len() { return Err(error::Unspecified); } let result = unsafe { GFp_memcmp(a.as_ptr(), b.as_ptr(), a.len()) }; match result { 0 => Ok(()), _ => Err(error::Unspecified), } } extern "C" { fn GFp_memcmp(a: *const u8, b: *const u8, len: c::size_t) -> c::int; } #[cfg(test)] mod tests { use crate::{bssl, error}; #[test] fn test_constant_time() -> Result<(), error::Unspecified> { extern "C" { fn bssl_constant_time_test_main() -> bssl::Result; } Result::from(unsafe { bssl_constant_time_test_main() }) } }