crypto/
mac.rs

1// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
2// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
3// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
4// option. This file may not be copied, modified, or distributed
5// except according to those terms.
6
7/*!
8 * The mac module defines the Message Authentication Code (Mac) trait.
9 */
10
11use util::fixed_time_eq;
12
13/**
14 * The Mac trait defines methods for a Message Authentication function.
15 */
16pub trait Mac {
17    /**
18     * Process input data.
19     *
20     * # Arguments
21     * * data - The input data to process.
22     *
23     */
24    fn input(&mut self, data: &[u8]);
25
26    /**
27     * Reset the Mac state to begin processing another input stream.
28     */
29    fn reset(&mut self);
30
31    /**
32     * Obtain the result of a Mac computation as a MacResult.
33     */
34    fn result(&mut self) -> MacResult;
35
36    /**
37     * Obtain the result of a Mac computation as [u8]. This method should be used very carefully
38     * since incorrect use of the Mac code could result in permitting a timing attack which defeats
39     * the security provided by a Mac function.
40     */
41    fn raw_result(&mut self, output: &mut [u8]);
42
43    /**
44     * Get the size of the Mac code, in bytes.
45     */
46    fn output_bytes(&self) -> usize;
47}
48
49/**
50 * A MacResult wraps a Mac code and provides a safe Eq implementation that runs in fixed time.
51 */
52pub struct MacResult {
53    code: Vec<u8>
54}
55
56impl MacResult {
57    /**
58     * Create a new MacResult.
59     */
60    pub fn new(code: &[u8]) -> MacResult {
61        MacResult {
62            code: code.to_vec()
63        }
64    }
65
66    /**
67     * Create a new MacResult taking ownership of the specified code value.
68     */
69    pub fn new_from_owned(code: Vec<u8>) -> MacResult {
70        MacResult {
71            code: code
72        }
73    }
74
75    /**
76     * Get the code value. Be very careful using this method, since incorrect use of the code value
77     * may permit timing attacks which defeat the security provided by the Mac function.
78     */
79    pub fn code<'s>(&'s self) -> &'s [u8] {
80        &self.code[..]
81    }
82}
83
84impl PartialEq for MacResult {
85    fn eq(&self, x: &MacResult) -> bool {
86        let lhs = self.code();
87        let rhs = x.code();
88        fixed_time_eq(lhs, rhs)
89    }
90}
91
92impl Eq for MacResult { }
crypto/mac.rs

crypto/
mac.rs
