Botan 3.3.0
Crypto and TLS for C&
scrypt.cpp
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1/**
2* (C) 2018 Jack Lloyd
3* (C) 2018 Ribose Inc
4*
5* Botan is released under the Simplified BSD License (see license.txt)
6*/
7
8#include <botan/scrypt.h>
9
10#include <botan/exceptn.h>
11#include <botan/pbkdf2.h>
12#include <botan/internal/bit_ops.h>
13#include <botan/internal/fmt.h>
14#include <botan/internal/loadstor.h>
15#include <botan/internal/salsa20.h>
16#include <botan/internal/timer.h>
17
18namespace Botan {
19
20namespace {
21
22size_t scrypt_memory_usage(size_t N, size_t r, size_t p) {
23 return 128 * r * (N + p);
24}
25
26} // namespace
27
28std::string Scrypt_Family::name() const {
29 return "Scrypt";
30}
31
32std::unique_ptr<PasswordHash> Scrypt_Family::default_params() const {
33 return std::make_unique<Scrypt>(32768, 8, 1);
34}
35
36std::unique_ptr<PasswordHash> Scrypt_Family::tune(size_t output_length,
37 std::chrono::milliseconds msec,
38 size_t max_memory_usage_mb,
39 std::chrono::milliseconds tune_time) const {
40 BOTAN_UNUSED(output_length);
41
42 /*
43 * Some rough relations between scrypt parameters and runtime.
44 * Denote here by stime(N,r,p) the msec it takes to run scrypt.
45 *
46 * Emperically for smaller sizes:
47 * stime(N,8*r,p) / stime(N,r,p) is ~ 6-7
48 * stime(N,r,8*p) / stime(N,r,8*p) is ~ 7
49 * stime(2*N,r,p) / stime(N,r,p) is ~ 2
50 *
51 * Compute stime(8192,1,1) as baseline and extrapolate
52 */
53
54 // We include a bit of slop here (the + 512) to handle the fact that scrypt's
55 // memory consumption is modified by all three parameters, and otherwise we
56 // stop before hitting the desired target.
57
58 const size_t max_memory_usage = max_memory_usage_mb * 1024 * 1024 + 512;
59 // Starting parameters
60 size_t N = 8 * 1024;
61 size_t r = 1;
62 size_t p = 1;
63
64 Timer timer("Scrypt");
65
66 auto pwdhash = this->from_params(N, r, p);
67
68 timer.run_until_elapsed(tune_time, [&]() {
69 uint8_t output[32] = {0};
70 pwdhash->derive_key(output, sizeof(output), "test", 4, nullptr, 0);
71 });
72
73 // No timer events seems strange, perhaps something is wrong - give
74 // up on this and just return default params
75 if(timer.events() == 0) {
76 return default_params();
77 }
78
79 // nsec per eval of scrypt with initial params
80 const uint64_t measured_time = timer.value() / timer.events();
81
82 const uint64_t target_nsec = msec.count() * static_cast<uint64_t>(1000000);
83
84 uint64_t est_nsec = measured_time;
85
86 // First move increase r by 8x if possible
87
88 if(max_memory_usage == 0 || scrypt_memory_usage(N, r * 8, p) <= max_memory_usage) {
89 if(target_nsec / est_nsec >= 5) {
90 r *= 8;
91 est_nsec *= 5;
92 }
93 }
94
95 // Now double N as many times as we can
96
97 while(max_memory_usage == 0 || scrypt_memory_usage(N * 2, r, p) <= max_memory_usage) {
98 if(target_nsec / est_nsec >= 2) {
99 N *= 2;
100 est_nsec *= 2;
101 } else {
102 break;
103 }
104 }
105
106 // If we have extra runtime budget, increment p
107
108 if(target_nsec / est_nsec > 2) {
109 p *= std::min<size_t>(1024, static_cast<size_t>(target_nsec / est_nsec));
110 }
111
112 return std::make_unique<Scrypt>(N, r, p);
113}
114
115std::unique_ptr<PasswordHash> Scrypt_Family::from_params(size_t N, size_t r, size_t p) const {
116 return std::make_unique<Scrypt>(N, r, p);
117}
118
119std::unique_ptr<PasswordHash> Scrypt_Family::from_iterations(size_t iter) const {
120 const size_t r = 8;
121 const size_t p = 1;
122
123 size_t N = 8192;
124
125 if(iter > 50000) {
126 N = 16384;
127 }
128 if(iter > 100000) {
129 N = 32768;
130 }
131 if(iter > 150000) {
132 N = 65536;
133 }
134
135 return std::make_unique<Scrypt>(N, r, p);
136}
137
138Scrypt::Scrypt(size_t N, size_t r, size_t p) : m_N(N), m_r(r), m_p(p) {
139 if(!is_power_of_2(N)) {
140 throw Invalid_Argument("Scrypt N parameter must be a power of 2");
141 }
142
143 if(p == 0 || p > 1024) {
144 throw Invalid_Argument("Invalid or unsupported scrypt p");
145 }
146 if(r == 0 || r > 256) {
147 throw Invalid_Argument("Invalid or unsupported scrypt r");
148 }
149 if(N < 1 || N > 4194304) {
150 throw Invalid_Argument("Invalid or unsupported scrypt N");
151 }
152}
153
154std::string Scrypt::to_string() const {
155 return fmt("Scrypt({},{},{})", m_N, m_r, m_p);
156}
157
159 const size_t N = memory_param();
160 const size_t p = parallelism();
161 const size_t r = iterations();
162
163 return scrypt_memory_usage(N, r, p);
164}
165
166namespace {
167
168void scryptBlockMix(size_t r, uint8_t* B, uint8_t* Y) {
169 uint32_t B32[16];
171 copy_mem(X.data(), &B[(2 * r - 1) * 64], 64);
172
173 for(size_t i = 0; i != 2 * r; i++) {
174 xor_buf(X.data(), &B[64 * i], 64);
175 load_le<uint32_t>(B32, X.data(), 16);
176 Salsa20::salsa_core(X.data(), B32, 8);
177 copy_mem(&Y[64 * i], X.data(), 64);
178 }
179
180 for(size_t i = 0; i < r; ++i) {
181 copy_mem(&B[i * 64], &Y[(i * 2) * 64], 64);
182 }
183
184 for(size_t i = 0; i < r; ++i) {
185 copy_mem(&B[(i + r) * 64], &Y[(i * 2 + 1) * 64], 64);
186 }
187}
188
189void scryptROMmix(size_t r, size_t N, uint8_t* B, secure_vector<uint8_t>& V) {
190 const size_t S = 128 * r;
191
192 for(size_t i = 0; i != N; ++i) {
193 copy_mem(&V[S * i], B, S);
194 scryptBlockMix(r, B, &V[N * S]);
195 }
196
197 for(size_t i = 0; i != N; ++i) {
198 // compiler doesn't know here that N is power of 2
199 const size_t j = load_le<uint32_t>(&B[(2 * r - 1) * 64], 0) & (N - 1);
200 xor_buf(B, &V[j * S], S);
201 scryptBlockMix(r, B, &V[N * S]);
202 }
203}
204
205} // namespace
206
207void Scrypt::derive_key(uint8_t output[],
208 size_t output_len,
209 const char* password,
210 size_t password_len,
211 const uint8_t salt[],
212 size_t salt_len) const {
213 const size_t N = memory_param();
214 const size_t p = parallelism();
215 const size_t r = iterations();
216
217 const size_t S = 128 * r;
218 secure_vector<uint8_t> B(p * S);
219 // temp space
220 secure_vector<uint8_t> V((N + 1) * S);
221
222 auto hmac_sha256 = MessageAuthenticationCode::create_or_throw("HMAC(SHA-256)");
223
224 try {
225 hmac_sha256->set_key(cast_char_ptr_to_uint8(password), password_len);
226 } catch(Invalid_Key_Length&) {
227 throw Invalid_Argument("Scrypt cannot accept passphrases of the provided length");
228 }
229
230 pbkdf2(*hmac_sha256, B.data(), B.size(), salt, salt_len, 1);
231
232 // these can be parallel
233 for(size_t i = 0; i != p; ++i) {
234 scryptROMmix(r, N, &B[128 * r * i], V);
235 }
236
237 pbkdf2(*hmac_sha256, output, output_len, B.data(), B.size(), 1);
238}
239
240} // namespace Botan
#define BOTAN_UNUSED
Definition assert.h:118
static std::unique_ptr< MessageAuthenticationCode > create_or_throw(std::string_view algo_spec, std::string_view provider="")
Definition mac.cpp:148
static void salsa_core(uint8_t output[64], const uint32_t input[16], size_t rounds)
Definition salsa20.cpp:62
std::unique_ptr< PasswordHash > from_params(size_t N, size_t r, size_t p) const override
Definition scrypt.cpp:115
std::unique_ptr< PasswordHash > tune(size_t output_length, std::chrono::milliseconds msec, size_t max_memory, std::chrono::milliseconds tune_msec) const override
Definition scrypt.cpp:36
std::unique_ptr< PasswordHash > from_iterations(size_t iter) const override
Definition scrypt.cpp:119
std::string name() const override
Definition scrypt.cpp:28
std::unique_ptr< PasswordHash > default_params() const override
Definition scrypt.cpp:32
std::string to_string() const override
Definition scrypt.cpp:154
size_t memory_param() const override
Definition scrypt.h:44
size_t iterations() const override
Definition scrypt.h:40
size_t parallelism() const override
Definition scrypt.h:42
size_t total_memory_usage() const override
Definition scrypt.cpp:158
Scrypt(size_t N, size_t r, size_t p)
Definition scrypt.cpp:138
void derive_key(uint8_t out[], size_t out_len, const char *password, size_t password_len, const uint8_t salt[], size_t salt_len) const override
Definition scrypt.cpp:207
uint64_t value() const
Definition timer.h:66
uint64_t events() const
Definition timer.h:81
void run_until_elapsed(std::chrono::milliseconds msec, F f)
Definition timer.h:60
FE_25519 Y
Definition ge.cpp:26
FE_25519 X
Definition ge.cpp:25
constexpr bool is_power_of_2(T arg)
Definition bit_ops.h:45
std::string fmt(std::string_view format, const T &... args)
Definition fmt.h:53
constexpr void xor_buf(ranges::contiguous_output_range< uint8_t > auto &&out, ranges::contiguous_range< uint8_t > auto &&in)
Definition mem_ops.h:340
std::vector< T, secure_allocator< T > > secure_vector
Definition secmem.h:61
size_t pbkdf2(MessageAuthenticationCode &prf, uint8_t out[], size_t out_len, std::string_view password, const uint8_t salt[], size_t salt_len, size_t iterations, std::chrono::milliseconds msec)
Definition pbkdf2.cpp:78
constexpr void copy_mem(T *out, const T *in, size_t n)
Definition mem_ops.h:146
const uint8_t * cast_char_ptr_to_uint8(const char *s)
Definition mem_ops.h:272