otp-simple 0.1.0

A simple implementation of the TOTP and HOTP algorithms.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163

//! Implementatations of [TOTP (RFC6238)](https://www.rfc-editor.org/rfc/rfc6238) and [HOTP (RFC4226)](https://www.rfc-editor.org/rfc/rfc4226).

use hmac::{
    digest::{
        block_buffer::Eager,
        core_api::{BufferKindUser, CoreProxy, FixedOutputCore, UpdateCore},
        crypto_common::BlockSizeUser,
        typenum::{IsLess, Le, NonZero, U256},
        HashMarker,
    },
    Hmac, Mac,
};

/// The standard step length for TOTP.
pub const DEFAULT_STEP: u64 = 30;
/// The standard number of output digits for TOTP and HOTP.
pub const DEFAULT_DIGITS: u8 = 6;

/// Create a Time-Based One-Time Password, wrapped to a specific number of digits.
#[inline]
pub fn totp<D>(time: u64, step: u64, secret: &[u8], digits: u32) -> u32
where
    D: CoreProxy,
    D::Core: HashMarker
        + UpdateCore
        + FixedOutputCore
        + BufferKindUser<BufferKind = Eager>
        + Default
        + Clone,
    <D::Core as BlockSizeUser>::BlockSize: IsLess<U256>,
    Le<<D::Core as BlockSizeUser>::BlockSize, U256>: NonZero,
{
    truncate_code(totp_raw::<D>(time, step, secret), digits)
}

/// Create a Time-Based One-Time Password.
#[inline]
pub fn totp_raw<D>(time: u64, step: u64, secret: &[u8]) -> u32
where
    D: CoreProxy,
    D::Core: HashMarker
        + UpdateCore
        + FixedOutputCore
        + BufferKindUser<BufferKind = Eager>
        + Default
        + Clone,
    <D::Core as BlockSizeUser>::BlockSize: IsLess<U256>,
    Le<<D::Core as BlockSizeUser>::BlockSize, U256>: NonZero,
{
    hotp_raw::<D>(time / step, secret)
}

/// Create an HMAC-Based One-Time Password, wrapped to a specific number of digits.
#[inline]
pub fn hotp<D>(count: u64, secret: &[u8], digits: u32) -> u32
where
    D: CoreProxy,
    D::Core: HashMarker
        + UpdateCore
        + FixedOutputCore
        + BufferKindUser<BufferKind = Eager>
        + Default
        + Clone,
    <D::Core as BlockSizeUser>::BlockSize: IsLess<U256>,
    Le<<D::Core as BlockSizeUser>::BlockSize, U256>: NonZero,
{
    truncate_code(hotp_raw::<D>(count, secret), digits)
}

/// Create an HMAC-Based One-Time Password.
pub fn hotp_raw<D>(count: u64, secret: &[u8]) -> u32
where
    D: CoreProxy,
    D::Core: HashMarker
        + UpdateCore
        + FixedOutputCore
        + BufferKindUser<BufferKind = Eager>
        + Default
        + Clone,
    <D::Core as BlockSizeUser>::BlockSize: IsLess<U256>,
    Le<<D::Core as BlockSizeUser>::BlockSize, U256>: NonZero,
{
    let mut mac = Hmac::<D>::new_from_slice(secret).expect("HMAC can take key of any size");

    mac.update(&count.to_be_bytes());

    let signature = &mac.finalize().into_bytes()[..];

    twist_bytes(signature)
}

fn truncate_code(code: u32, digits: u32) -> u32 {
    code % 10u32.pow(digits)
}

fn twist_bytes(input: &[u8]) -> u32 {
    assert!(input.len() >= 16, "input length must be at least 16");

    let offset = input.last().unwrap() & 0xf;
    let offset = offset as usize;

    let binary = &input[offset..=offset + 3];
    let binary = u32::from_be_bytes([binary[0], binary[1], binary[2], binary[3]]);
    let binary = binary & 0x7fffffff;

    binary
}

#[cfg(test)]
mod test {
    use sha1::Sha1;
    use sha2::{Sha256, Sha512};

    use super::*;

    #[test]
    fn test_hotp() {
        const DIGITS: u32 = 6;

        let secret = "12345678901234567890".as_bytes();

        let values = [
            (0x4c93cf18, 755224),
            (0x41397eea, 287082),
            (0x082fef30, 359152),
            (0x66ef7655, 969429),
            (0x61c5938a, 338314),
            (0x33c083d4, 254676),
            (0x7256c032, 287922),
            (0x04e5b397, 162583),
            (0x2823443f, 399871),
            (0x2679dc69, 520489),
        ];

        for (i, value) in values.into_iter().enumerate() {
            assert_eq!(hotp_raw::<Sha1>(i as u64, secret), value.0);
            assert_eq!(hotp::<Sha1>(i as u64, secret, DIGITS), value.1);
        }
    }

    #[test]
    fn test_totp() {
        const STEP: u64 = DEFAULT_STEP;
        const DIGITS: u32 = 8;
        
        let secrets = (b"12345678901234567890", b"12345678901234567890123456789012", b"1234567890123456789012345678901234567890123456789012345678901234");

        let values = [
            (59, (94287082, 46119246, 90693936)),
            (1111111109, (07081804, 68084774, 25091201)),
            (1111111111, (14050471, 67062674, 99943326)),
            (1234567890, (89005924, 91819424, 93441116)),
            (2000000000, (69279037, 90698825, 38618901)),
            (20000000000u64, (65353130, 77737706, 47863826)),
        ];

        for (time, codes) in values {
            assert_eq!(totp::<Sha1>(time, STEP, secrets.0, DIGITS), codes.0);
            assert_eq!(totp::<Sha256>(time, STEP, secrets.1, DIGITS), codes.1);
            assert_eq!(totp::<Sha512>(time, STEP, secrets.2, DIGITS), codes.2);
        }
    }
}