/src/botan/src/lib/kdf/hkdf/hkdf.cpp
Line | Count | Source (jump to first uncovered line) |
1 | | /* |
2 | | * HKDF |
3 | | * (C) 2013,2015,2017 Jack Lloyd |
4 | | * (C) 2016 René Korthaus, Rohde & Schwarz Cybersecurity |
5 | | * |
6 | | * Botan is released under the Simplified BSD License (see license.txt) |
7 | | */ |
8 | | |
9 | | #include <botan/hkdf.h> |
10 | | #include <botan/loadstor.h> |
11 | | |
12 | | namespace Botan { |
13 | | |
14 | | size_t HKDF::kdf(uint8_t key[], size_t key_len, |
15 | | const uint8_t secret[], size_t secret_len, |
16 | | const uint8_t salt[], size_t salt_len, |
17 | | const uint8_t label[], size_t label_len) const |
18 | 0 | { |
19 | 0 | HKDF_Extract extract(m_prf->clone()); |
20 | 0 | HKDF_Expand expand(m_prf->clone()); |
21 | 0 | secure_vector<uint8_t> prk(m_prf->output_length()); |
22 | 0 |
|
23 | 0 | extract.kdf(prk.data(), prk.size(), secret, secret_len, salt, salt_len, nullptr, 0); |
24 | 0 | return expand.kdf(key, key_len, prk.data(), prk.size(), nullptr, 0, label, label_len); |
25 | 0 | } |
26 | | |
27 | | size_t HKDF_Extract::kdf(uint8_t key[], size_t key_len, |
28 | | const uint8_t secret[], size_t secret_len, |
29 | | const uint8_t salt[], size_t salt_len, |
30 | | const uint8_t[], size_t) const |
31 | 0 | { |
32 | 0 | secure_vector<uint8_t> prk; |
33 | 0 | if(salt_len == 0) |
34 | 0 | { |
35 | 0 | m_prf->set_key(std::vector<uint8_t>(m_prf->output_length())); |
36 | 0 | } |
37 | 0 | else |
38 | 0 | { |
39 | 0 | m_prf->set_key(salt, salt_len); |
40 | 0 | } |
41 | 0 |
|
42 | 0 | m_prf->update(secret, secret_len); |
43 | 0 | m_prf->final(prk); |
44 | 0 |
|
45 | 0 | const size_t written = std::min(prk.size(), key_len); |
46 | 0 | copy_mem(&key[0], prk.data(), written); |
47 | 0 | return written; |
48 | 0 | } |
49 | | |
50 | | size_t HKDF_Expand::kdf(uint8_t key[], size_t key_len, |
51 | | const uint8_t secret[], size_t secret_len, |
52 | | const uint8_t salt[], size_t salt_len, |
53 | | const uint8_t label[], size_t label_len) const |
54 | 0 | { |
55 | 0 | m_prf->set_key(secret, secret_len); |
56 | 0 |
|
57 | 0 | uint8_t counter = 1; |
58 | 0 | secure_vector<uint8_t> h; |
59 | 0 | size_t offset = 0; |
60 | 0 |
|
61 | 0 | while(offset != key_len && counter != 0) |
62 | 0 | { |
63 | 0 | m_prf->update(h); |
64 | 0 | m_prf->update(label, label_len); |
65 | 0 | m_prf->update(salt, salt_len); |
66 | 0 | m_prf->update(counter++); |
67 | 0 | m_prf->final(h); |
68 | 0 |
|
69 | 0 | const size_t written = std::min(h.size(), key_len - offset); |
70 | 0 | copy_mem(&key[offset], h.data(), written); |
71 | 0 | offset += written; |
72 | 0 | } |
73 | 0 |
|
74 | 0 | return offset; |
75 | 0 | } |
76 | | |
77 | | secure_vector<uint8_t> |
78 | | hkdf_expand_label(const std::string& hash_fn, |
79 | | const uint8_t secret[], size_t secret_len, |
80 | | const std::string& label, |
81 | | const uint8_t hash_val[], size_t hash_val_len, |
82 | | size_t length) |
83 | 0 | { |
84 | 0 | BOTAN_ARG_CHECK(length <= 0xFFFF, "HKDF-Expand-Label requested output too large"); |
85 | 0 | BOTAN_ARG_CHECK(label.size() <= 0xFF, "HKDF-Expand-Label label too long"); |
86 | 0 | BOTAN_ARG_CHECK(hash_val_len <= 0xFF, "HKDF-Expand-Label hash too long"); |
87 | 0 |
|
88 | 0 | const uint16_t length16 = static_cast<uint16_t>(length); |
89 | 0 |
|
90 | 0 | auto mac = MessageAuthenticationCode::create_or_throw("HMAC(" + hash_fn + ")"); |
91 | 0 |
|
92 | 0 | HKDF_Expand hkdf(mac.release()); |
93 | 0 |
|
94 | 0 | secure_vector<uint8_t> output(length16); |
95 | 0 | std::vector<uint8_t> prefix(3 + label.size() + 1); |
96 | 0 |
|
97 | 0 | prefix[0] = get_byte(0, length16); |
98 | 0 | prefix[1] = get_byte(1, length16); |
99 | 0 | prefix[2] = static_cast<uint8_t>(label.size()); |
100 | 0 |
|
101 | 0 | copy_mem(prefix.data() + 3, |
102 | 0 | cast_char_ptr_to_uint8(label.data()), |
103 | 0 | label.size()); |
104 | 0 |
|
105 | 0 | prefix[3 + label.size()] = static_cast<uint8_t>(hash_val_len); |
106 | 0 |
|
107 | 0 | /* |
108 | 0 | * We do something a little dirty here to avoid copying the hash_val, |
109 | 0 | * making use of the fact that Botan's KDF interface supports label+salt, |
110 | 0 | * and knowing that our HKDF hashes first param label then param salt. |
111 | 0 | */ |
112 | 0 | hkdf.kdf(output.data(), output.size(), |
113 | 0 | secret, secret_len, |
114 | 0 | hash_val, hash_val_len, |
115 | 0 | prefix.data(), prefix.size()); |
116 | 0 |
|
117 | 0 | return output; |
118 | 0 | } |
119 | | |
120 | | } |