Commit be0e83c9 authored by Alex Crichton's avatar Alex Crichton
Browse files

Add bindings to CRYPTO_memcmp 

This should help other projects use a constant-time memory comparison.
parent 73885dad

src/crypto/memcmp.rs

0 → 100644
+39 −0
Original line number Diff line number Diff line 
use libc::size_t;

use ffi;



/// Returns `true` iff `a` and `b` contain the same bytes.

///

/// This operation takes an amount of time dependent on the length of the two

/// arrays given, but is independent of the contents of a and b.

///

/// # Failure

///

/// This function will fail the current task if `a` and `b` do not have the same

/// length.

pub fn eq(a: &[u8], b: &[u8]) -> bool {

    assert!(a.len() == b.len());

    let ret = unsafe {

        ffi::CRYPTO_memcmp(a.as_ptr() as *const _,

                           b.as_ptr() as *const _,

                           a.len() as size_t)

    };

    ret == 0

}



#[cfg(test)]

mod tests {

    use super::eq;



    #[test]

    fn test_eq() {

        assert!(eq([], []));

        assert!(eq([1], [1]));

        assert!(!eq([1, 2, 3], [1, 2, 4]));

    }



    #[test]

    #[should_fail]

    fn test_diff_lens() {

        eq([], [1]);

    }

}

src/crypto/mod.rs

+1 −0
Original line number Diff line number Diff line
@@ -21,3 +21,4 @@ pub mod pkcs5; 
pub mod pkey;

pub mod rand;

pub mod symm;

pub mod memcmp;

src/ffi.rs

+3 −1
Original line number Diff line number Diff line 
#![allow(non_camel_case_types)]

#![allow(dead_code)]

use libc::{c_void, c_int, c_char, c_ulong, c_long, c_uint, c_uchar};

use libc::{c_void, c_int, c_char, c_ulong, c_long, c_uint, c_uchar, size_t};



pub type ASN1_INTEGER = c_void;

pub type ASN1_STRING = c_void;
@@ -265,6 +265,8 @@ extern "C" { 
                                                           file: *const c_char,

                                                           line: c_int));

    pub fn CRYPTO_free(buf: *const c_char);

    pub fn CRYPTO_memcmp(a: *const c_void, b: *const c_void,

                         len: size_t) -> c_int;



    pub fn ERR_get_error() -> c_ulong;