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

//! sha256-rs
//!
//! Implementation of the SHA256 hash made using Rust

/// Initializing Variables
/// First 32 bits of fractional parts of the square roots of the first eight primes
const H0: u32 = 0x6a09e667;
const H1: u32 = 0xbb67ae85;
const H2: u32 = 0x3c6ef372;
const H3: u32 = 0xa54ff53a;
const H4: u32 = 0x510e527f;
const H5: u32 = 0x9b05688c;
const H6: u32 = 0x1f83d9ab;
const H7: u32 = 0x5be0cd19;

/// Constants table
/// First 32 bits of the fractional parts of the cube roots of the first 64 primes
const K: [u32; 64] = [
    0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
    0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
    0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
    0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
    0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
    0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
    0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
    0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2,
];

/// SHA256 digest bytes
///
/// # Example
///
/// ```rust
/// let bytes = b"hello";
/// let result = sha256_rs::sha256(bytes);
/// assert_eq!(result, [44, 242, 77, 186, 95, 176, 163, 14, 38, 232, 59, 42, 197, 185, 226, 158, 27, 22, 30, 92, 31, 167, 66, 94, 115, 4, 51, 98, 147, 139, 152, 36])
/// ```
///
pub fn sha256(bytes: &[u8]) -> [u8; 32] {
    let mut bytes = bytes.to_vec();
    let bytes_len = bytes.len() * 8;
    bytes.push(0x80);

    while (bytes.len() % 64) != 56 {
        bytes.push(0);
    }

    for i in bytes_len.to_be_bytes().iter() {
        bytes.push(*i);
    }

    let mut temp = vec![];

    for chunk in bytes.as_slice().chunks(64) {
        let mut w = [0; 64];

        for (w, d) in w.iter_mut().zip(chunk.iter().step_by(4)).take(16) {
            *w = u32::from_be_bytes(unsafe { *(d as *const u8 as *const [u8; 4]) });
        }

        for i in 16..64 {
            let s0: u32 = w[i - 15].rotate_right(7) ^ w[i - 15].rotate_right(18) ^ (w[i - 15] >> 3);
            let s1: u32 = w[i - 2].rotate_right(17) ^ w[i - 2].rotate_right(19) ^ (w[i - 2] >> 10);
            w[i] = w[i - 16]
                .wrapping_add(s0)
                .wrapping_add(w[i - 7])
                .wrapping_add(s1);
        }

        let mut a = H0;
        let mut b = H1;
        let mut c = H2;
        let mut d = H3;
        let mut e = H4;
        let mut f = H5;
        let mut g = H6;
        let mut h = H7;

        for i in 0..64 {
            let s1 = e.rotate_right(6) ^ e.rotate_right(11) ^ e.rotate_right(25);
            let ch = (e & f) ^ (!e & g);
            let temp1 = h
                .wrapping_add(s1)
                .wrapping_add(ch)
                .wrapping_add(K[i])
                .wrapping_add(w[i]);
            let s0 = a.rotate_right(2) ^ a.rotate_right(13) ^ a.rotate_right(22);
            let maj = (a & b) ^ (a & c) ^ (b & c);
            let temp2 = s0.wrapping_add(maj);

            h = g;
            g = f;
            f = e;
            e = d.wrapping_add(temp1);
            d = c;
            c = b;
            b = a;
            a = temp1.wrapping_add(temp2);
        }

        temp.push(H0.wrapping_add(a).to_be_bytes());
        temp.push(H1.wrapping_add(b).to_be_bytes());
        temp.push(H2.wrapping_add(c).to_be_bytes());
        temp.push(H3.wrapping_add(d).to_be_bytes());
        temp.push(H4.wrapping_add(e).to_be_bytes());
        temp.push(H5.wrapping_add(f).to_be_bytes());
        temp.push(H6.wrapping_add(g).to_be_bytes());
        temp.push(H7.wrapping_add(h).to_be_bytes());
    }

    let mut result = [0u8; 32];
    result.copy_from_slice(temp.concat().as_slice());
    result
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn it_works() {
        assert_eq!(
            sha256("Test".as_bytes()),
            [
                83, 46, 170, 189, 149, 116, 136, 13, 191, 118, 185, 184, 204, 0, 131, 44, 32, 166,
                236, 17, 61, 104, 34, 153, 85, 13, 122, 110, 15, 52, 94, 37
            ]
        );

        assert_eq!(
            sha256("Rust".as_bytes()),
            [
                217, 170, 137, 253, 209, 90, 213, 196, 29, 156, 18, 143, 239, 254, 158, 7, 220,
                130, 139, 131, 248, 82, 150, 247, 244, 43, 218, 80, 104, 33, 48, 14
            ]
        );

        assert_eq!(
            sha256("hello world".as_bytes()),
            [
                185, 77, 39, 185, 147, 77, 62, 8, 165, 46, 82, 215, 218, 125, 171, 250, 196, 132,
                239, 227, 122, 83, 128, 238, 144, 136, 247, 172, 226, 239, 205, 233
            ]
        );

        assert_eq!(
            sha256("Lorem ipsum dolor sit amet, consectetur adipiscing elit".as_bytes()),
            [
                7, 254, 77, 74, 37, 113, 130, 65, 175, 20, 90, 147, 248, 144, 235, 84, 105, 5, 46,
                37, 29, 25, 157, 23, 59, 211, 189, 80, 195, 187, 77, 162
            ]
        );
    }
}