Botan: src/kdf/prf_x942/prf_x942.cpp Source File

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prf_x942.cpp
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1 /*
2 * X9.42 PRF
3 * (C) 1999-2007 Jack Lloyd
4 *
5 * Distributed under the terms of the Botan license
6 */
7
8 #include <botan/prf_x942.h>
9 #include <botan/der_enc.h>
10 #include <botan/oids.h>
11 #include <botan/sha160.h>
12 #include <botan/loadstor.h>
13 #include <algorithm>
14 #include <memory>
15
16 namespace Botan {
17
18 namespace {
19
20 /*
21 * Encode an integer as an OCTET STRING
22 */
23 MemoryVector<byte> encode_x942_int(u32bit n)
24 {
25 byte n_buf[4] = { 0 };
26 store_be(n, n_buf);
27 return DER_Encoder().encode(n_buf, 4, OCTET_STRING).get_contents();
28 }
29
30 }
31
32 /*
33 * X9.42 PRF
34 */
35 SecureVector<byte> X942_PRF::derive(size_t key_len,
36 const byte secret[], size_t secret_len,
37 const byte salt[], size_t salt_len) const
38 {
39 SHA_160 hash;
40 const OID kek_algo(key_wrap_oid);
41
42 SecureVector<byte> key;
43 u32bit counter = 1;
44
45 while(key.size() != key_len && counter)
46 {
47 hash.update(secret, secret_len);
48
49 hash.update(
50 DER_Encoder().start_cons(SEQUENCE)
51
52 .start_cons(SEQUENCE)
53 .encode(kek_algo)
54 .raw_bytes(encode_x942_int(counter))
55 .end_cons()
56
57 .encode_if(salt_len != 0,
58 DER_Encoder()
59 .start_explicit(0)
60 .encode(salt, salt_len, OCTET_STRING)
61 .end_explicit()
62 )
63
64 .start_explicit(2)
65 .raw_bytes(encode_x942_int(static_cast<u32bit>(8 * key_len)))
66 .end_explicit()
67
68 .end_cons().get_contents()
69 );
70
71 SecureVector<byte> digest = hash.final();
72 const size_t needed = std::min(digest.size(), key_len - key.size());
73 key += std::make_pair(&digest[0], needed);
74
75 ++counter;
76 }
77
78 return key;
79 }
80
81 /*
82 * X9.42 Constructor
83 */
84 X942_PRF::X942_PRF(const std::string& oid)
85 {
86 if(OIDS::have_oid(oid))
87 key_wrap_oid = OIDS::lookup(oid).as_string();
88 else
89 key_wrap_oid = oid;
90 }
91
92 }
Botan::byte
unsigned char byte
Definition: types.h:22
Botan::OCTET_STRING
Definition: asn1_int.h:31
Botan::DER_Encoder
Definition: der_enc.h:22
Botan::OIDS::lookup
std::string lookup(const OID &oid)
Definition: oids.cpp:31
Botan::Buffered_Computation::update
void update(const byte in[], size_t length)
Definition: buf_comp.h:33
Botan::SHA_160
Definition: sha160.h:18
Botan::X942_PRF::X942_PRF
X942_PRF(const std::string &oid)
Definition: prf_x942.cpp:84
Botan::SEQUENCE
Definition: asn1_int.h:35
Botan::MemoryRegion::size
size_t size() const
Definition: secmem.h:29
Botan
Definition: algo_base.h:14
Botan::Buffered_Computation::final
void final(byte out[])
Definition: buf_comp.h:80
Botan::PEM_Code::encode
std::string encode(const byte der[], size_t length, const std::string &label, size_t width)
Definition: pem.cpp:19
Botan::store_be
void store_be(u16bit in, byte out[2])
Definition: loadstor.h:412
Botan::SecureVector< byte >
Botan::OIDS::have_oid
bool have_oid(const std::string &name)
Definition: oids.cpp:61
Botan::OID
Definition: asn1_oid.h:20
Botan::X942_PRF::derive
SecureVector< byte > derive(size_t, const byte[], size_t, const byte[], size_t) const
Definition: prf_x942.cpp:35
Botan::u32bit
unsigned int u32bit
Definition: types.h:32
oid
OID oid
Definition: x509_ext.cpp:446