puressh 0.0.3

A pure-Rust SSH (Secure Shell) protocol library, in the spirit of libssh, built on purecrypto.
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

//! `aes*-ctr` (RFC 4344) — non-AEAD streaming ciphers paired with a separate MAC.

use purecrypto::cipher::{Aes128, Aes192, Aes256, Ctr};

use crate::error::{Error, Result};

#[derive(Clone)]
pub enum AesCtr {
    Aes128(Ctr<Aes128>),
    Aes192(Ctr<Aes192>),
    Aes256(Ctr<Aes256>),
}

impl AesCtr {
    pub(crate) fn new_128(key: &[u8], iv: &[u8]) -> Result<Self> {
        let k: &[u8; 16] = key
            .try_into()
            .map_err(|_| Error::Format("aes128-ctr key len"))?;
        let i: &[u8; 16] = iv.try_into().map_err(|_| Error::Format("aes-ctr iv len"))?;
        Ok(AesCtr::Aes128(Ctr::new(Aes128::new(k), i)))
    }

    pub(crate) fn new_192(key: &[u8], iv: &[u8]) -> Result<Self> {
        let k: &[u8; 24] = key
            .try_into()
            .map_err(|_| Error::Format("aes192-ctr key len"))?;
        let i: &[u8; 16] = iv.try_into().map_err(|_| Error::Format("aes-ctr iv len"))?;
        Ok(AesCtr::Aes192(Ctr::new(Aes192::new(k), i)))
    }

    pub(crate) fn new_256(key: &[u8], iv: &[u8]) -> Result<Self> {
        let k: &[u8; 32] = key
            .try_into()
            .map_err(|_| Error::Format("aes256-ctr key len"))?;
        let i: &[u8; 16] = iv.try_into().map_err(|_| Error::Format("aes-ctr iv len"))?;
        Ok(AesCtr::Aes256(Ctr::new(Aes256::new(k), i)))
    }

    pub(crate) fn apply_keystream(&mut self, buf: &mut [u8]) {
        match self {
            AesCtr::Aes128(c) => c.apply_keystream(buf),
            AesCtr::Aes192(c) => c.apply_keystream(buf),
            AesCtr::Aes256(c) => c.apply_keystream(buf),
        }
    }
}

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

    fn h(s: &str) -> Vec<u8> {
        let s: String = s.chars().filter(|c| !c.is_whitespace()).collect();
        hex::decode(s).unwrap()
    }

    // NIST SP 800-38A F.5.1 CTR-AES128.
    #[test]
    fn aes128_ctr_nist() {
        let key = h("2b7e151628aed2a6abf7158809cf4f3c");
        let iv = h("f0f1f2f3f4f5f6f7f8f9fafbfcfdfeff");
        let plaintext = h("6bc1bee22e409f96e93d7e117393172a\
             ae2d8a571e03ac9c9eb76fac45af8e51\
             30c81c46a35ce411e5fbc1191a0a52ef\
             f69f2445df4f9b17ad2b417be66c3710");
        let expected = h("874d6191b620e3261bef6864990db6ce\
             9806f66b7970fdff8617187bb9fffdff\
             5ae4df3edbd5d35e5b4f09020db03eab\
             1e031dda2fbe03d1792170a0f3009cee");

        let mut buf = plaintext.clone();
        let mut c = AesCtr::new_128(&key, &iv).unwrap();
        c.apply_keystream(&mut buf);
        assert_eq!(buf, expected);

        let mut c2 = AesCtr::new_128(&key, &iv).unwrap();
        c2.apply_keystream(&mut buf);
        assert_eq!(buf, plaintext);
    }

    // NIST SP 800-38A F.5.5 CTR-AES256.
    #[test]
    fn aes256_ctr_nist() {
        let key = h("603deb1015ca71be2b73aef0857d7781\
             1f352c073b6108d72d9810a30914dff4");
        let iv = h("f0f1f2f3f4f5f6f7f8f9fafbfcfdfeff");
        let plaintext = h("6bc1bee22e409f96e93d7e117393172a\
             ae2d8a571e03ac9c9eb76fac45af8e51\
             30c81c46a35ce411e5fbc1191a0a52ef\
             f69f2445df4f9b17ad2b417be66c3710");
        let expected = h("601ec313775789a5b7a7f504bbf3d228\
             f443e3ca4d62b59aca84e990cacaf5c5\
             2b0930daa23de94ce87017ba2d84988d\
             dfc9c58db67aada613c2dd08457941a6");

        let mut buf = plaintext;
        let mut c = AesCtr::new_256(&key, &iv).unwrap();
        c.apply_keystream(&mut buf);
        assert_eq!(buf, expected);
    }

    #[test]
    fn streaming_matches_oneshot() {
        let key = h("2b7e151628aed2a6abf7158809cf4f3c");
        let iv = h("f0f1f2f3f4f5f6f7f8f9fafbfcfdfeff");
        let plaintext = h("6bc1bee22e409f96e93d7e117393172a\
             ae2d8a571e03ac9c9eb76fac45af8e51\
             30c81c46a35ce411e5fbc1191a0a52ef\
             f69f2445df4f9b17ad2b417be66c3710");

        let mut oneshot = plaintext.clone();
        AesCtr::new_128(&key, &iv)
            .unwrap()
            .apply_keystream(&mut oneshot);

        let mut chunked = plaintext;
        let mut c = AesCtr::new_128(&key, &iv).unwrap();
        let mut start = 0;
        for len in [1usize, 14, 1, 30, 18] {
            c.apply_keystream(&mut chunked[start..start + len]);
            start += len;
        }
        assert_eq!(chunked, oneshot);
    }

    #[test]
    fn bad_key_length_is_format_error() {
        let iv = [0u8; 16];
        assert!(matches!(
            AesCtr::new_128(&[0u8; 15], &iv),
            Err(Error::Format(_))
        ));
        assert!(matches!(
            AesCtr::new_256(&[0u8; 31], &iv),
            Err(Error::Format(_))
        ));
    }
}