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
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
use hmac::Hmac;
use clear_on_drop::clear;
use options::ShaVariantOption;
pub struct Hkdf {
pub salt: Vec<u8>,
pub ikm: Vec<u8>,
pub info: Vec<u8>,
pub hmac: ShaVariantOption,
pub length: usize,
}
impl Drop for Hkdf {
fn drop(&mut self) {
self.salt.clear();
self.ikm.clear();
self.info.clear()
}
}
impl Hkdf {
pub fn hkdf_extract(&self, ikm: &[u8], salt: &[u8]) -> Vec<u8> {
let hmac_res = Hmac {
secret_key: salt.to_vec(),
message: ikm.to_vec(),
sha2: self.hmac
};
hmac_res.hmac_compute()
}
pub fn hkdf_expand(&self, prk: &[u8]) -> Vec<u8> {
if self.length > (255 * self.hmac.return_value() / 8) {
panic!("Derived key length above max. 255 * (HMAC OUTPUT LENGTH IN BYTES)");
}
let n_iter = (self.length as f32 / (self.hmac.return_value() / 8) as f32).ceil() as usize;
let mut con_step: Vec<u8> = vec![];
let mut hmac_hash_step: Vec<u8> = vec![];
let mut hkdf_final: Vec<u8> = vec![];
for x in 1..n_iter+1 {
con_step.append(&mut hmac_hash_step);
con_step.extend_from_slice(&self.info);
con_step.push(x as u8);
hmac_hash_step.extend_from_slice(&self.hkdf_extract(&con_step, prk));
con_step.clear();
hkdf_final.extend_from_slice(&hmac_hash_step);
}
hkdf_final.truncate(self.length);
hkdf_final
}
}
#[cfg(test)]
mod test {
extern crate hex;
use self::hex::decode;
use hkdf::Hkdf;
use options::ShaVariantOption;
#[test]
fn rfc5869_test_case_1() {
let hkdf_256 = Hkdf {
salt: decode("000102030405060708090a0b0c").unwrap(),
ikm: decode("0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b").unwrap(),
info: decode("f0f1f2f3f4f5f6f7f8f9").unwrap(),
hmac: ShaVariantOption::SHA256,
length: 42,
};
let expected_prk_256 = decode(
"077709362c2e32df0ddc3f0dc47bba6390b6c73bb50f9c3122ec844ad7c2b3e5").unwrap();
let expected_okm_256 = decode(
"3cb25f25faacd57a90434f64d0362f2a2d2d0a90cf1a5a4c5db02d56ecc4c5bf\
34007208d5b887185865").unwrap();
let actual_extract_256 = hkdf_256.hkdf_extract(&hkdf_256.ikm, &hkdf_256.salt);
assert_eq!(actual_extract_256, expected_prk_256);
assert_eq!(hkdf_256.hkdf_expand(&actual_extract_256), expected_okm_256);
}
#[test]
fn rfc5869_test_case_2() {
let hkdf_256 = Hkdf {
salt: decode("606162636465666768696a6b6c6d6e6f707172737475767778797a7b7c7d7e7f\
808182838485868788898a8b8c8d8e8f909192939495969798999a9b9c9d9e9f\
a0a1a2a3a4a5a6a7a8a9aaabacadaeaf").unwrap(),
ikm: decode("000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f\
202122232425262728292a2b2c2d2e2f303132333435363738393a3b3c3d3e3f\
404142434445464748494a4b4c4d4e4f").unwrap(),
info: decode("b0b1b2b3b4b5b6b7b8b9babbbcbdbebfc0c1c2c3c4c5c6c7c8c9cacbcccdcecf\
d0d1d2d3d4d5d6d7d8d9dadbdcdddedfe0e1e2e3e4e5e6e7e8e9eaebecedeeef\
f0f1f2f3f4f5f6f7f8f9fafbfcfdfeff").unwrap(),
hmac: ShaVariantOption::SHA256,
length: 82,
};
let expected_prk_256 = decode(
"06a6b88c5853361a06104c9ceb35b45cef760014904671014a193f40c15fc244").unwrap();
let expected_okm_256 = decode(
"b11e398dc80327a1c8e7f78c596a49344f012eda2d4efad8a050cc4c19afa97c\
59045a99cac7827271cb41c65e590e09da3275600c2f09b8367793a9aca3db71\
cc30c58179ec3e87c14c01d5c1f3434f1d87").unwrap();
let actual_extract_256 = hkdf_256.hkdf_extract(&hkdf_256.ikm, &hkdf_256.salt);
assert_eq!(actual_extract_256, expected_prk_256);
assert_eq!(hkdf_256.hkdf_expand(&actual_extract_256), expected_okm_256);
}
#[test]
fn rfc5869_test_case_3() {
let hkdf_256 = Hkdf {
salt: decode("").unwrap(),
ikm: decode("0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b").unwrap(),
info: decode("").unwrap(),
hmac: ShaVariantOption::SHA256,
length: 42,
};
let expected_prk_256 = decode(
"19ef24a32c717b167f33a91d6f648bdf96596776afdb6377ac434c1c293ccb04").unwrap();
let expected_okm_256 = decode(
"8da4e775a563c18f715f802a063c5a31b8a11f5c5ee1879ec3454e5f3c738d2d\
9d201395faa4b61a96c8").unwrap();
let actual_extract_256 = hkdf_256.hkdf_extract(&hkdf_256.ikm, &hkdf_256.salt);
assert_eq!(actual_extract_256, expected_prk_256);
assert_eq!(hkdf_256.hkdf_expand(&actual_extract_256), expected_okm_256);
}
#[test]
#[should_panic]
fn hkdf_maximum_length_256() {
let hkdf_256 = Hkdf {
salt: decode("").unwrap(),
ikm: decode("0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b").unwrap(),
info: decode("").unwrap(),
hmac: ShaVariantOption::SHA256,
length: 9000,
};
let hkdf_256_extract = hkdf_256.hkdf_extract(&hkdf_256.ikm, &hkdf_256.salt);
hkdf_256.hkdf_expand(&hkdf_256_extract);
}
#[test]
#[should_panic]
fn hkdf_maximum_length_384() {
let hkdf_384 = Hkdf {
salt: decode("").unwrap(),
ikm: decode("0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b").unwrap(),
info: decode("").unwrap(),
hmac: ShaVariantOption::SHA384,
length: 13000,
};
let hkdf_384_extract = hkdf_384.hkdf_extract(&hkdf_384.ikm, &hkdf_384.salt);
hkdf_384.hkdf_expand(&hkdf_384_extract);
}
#[test]
#[should_panic]
fn hkdf_maximum_length_512() {
let hkdf_512 = Hkdf {
salt: decode("").unwrap(),
ikm: decode("0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b").unwrap(),
info: decode("").unwrap(),
hmac: ShaVariantOption::SHA512,
length: 17000,
};
let hkdf_512_extract = hkdf_512.hkdf_extract(&hkdf_512.ikm, &hkdf_512.salt);
hkdf_512.hkdf_expand(&hkdf_512_extract);
}
}