1/*
2 * Copyright 2015-2016 The OpenSSL Project Authors. All Rights Reserved.
3 *
4 * Licensed under the OpenSSL license (the "License"). You may not use
5 * this file except in compliance with the License. You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
8 */
9
10#include <openssl/evp.h>
11
12#include <assert.h>
13
14#include <openssl/err.h>
15#include <openssl/mem.h>
16#include <openssl/type_check.h>
17
18#include "../internal.h"
19
20
21// This file implements scrypt, described in RFC 7914.
22//
23// Note scrypt refers to both "blocks" and a "block size" parameter, r. These
24// are two different notions of blocks. A Salsa20 block is 64 bytes long,
25// represented in this implementation by 16 |uint32_t|s. |r| determines the
26// number of 64-byte Salsa20 blocks in a scryptBlockMix block, which is 2 * |r|
27// Salsa20 blocks. This implementation refers to them as Salsa20 blocks and
28// scrypt blocks, respectively.
29
30// A block_t is a Salsa20 block.
31typedef struct { uint32_t words[16]; } block_t;
32
33OPENSSL_STATIC_ASSERT(sizeof(block_t) == 64, "block_t has padding");
34
35#define R(a, b) (((a) << (b)) | ((a) >> (32 - (b))))
36
37// salsa208_word_specification implements the Salsa20/8 core function, also
38// described in RFC 7914, section 3. It modifies the block at |inout|
39// in-place.
40static void salsa208_word_specification(block_t *inout) {
41 block_t x;
42 OPENSSL_memcpy(&x, inout, sizeof(x));
43
44 for (int i = 8; i > 0; i -= 2) {
45 x.words[4] ^= R(x.words[0] + x.words[12], 7);
46 x.words[8] ^= R(x.words[4] + x.words[0], 9);
47 x.words[12] ^= R(x.words[8] + x.words[4], 13);
48 x.words[0] ^= R(x.words[12] + x.words[8], 18);
49 x.words[9] ^= R(x.words[5] + x.words[1], 7);
50 x.words[13] ^= R(x.words[9] + x.words[5], 9);
51 x.words[1] ^= R(x.words[13] + x.words[9], 13);
52 x.words[5] ^= R(x.words[1] + x.words[13], 18);
53 x.words[14] ^= R(x.words[10] + x.words[6], 7);
54 x.words[2] ^= R(x.words[14] + x.words[10], 9);
55 x.words[6] ^= R(x.words[2] + x.words[14], 13);
56 x.words[10] ^= R(x.words[6] + x.words[2], 18);
57 x.words[3] ^= R(x.words[15] + x.words[11], 7);
58 x.words[7] ^= R(x.words[3] + x.words[15], 9);
59 x.words[11] ^= R(x.words[7] + x.words[3], 13);
60 x.words[15] ^= R(x.words[11] + x.words[7], 18);
61 x.words[1] ^= R(x.words[0] + x.words[3], 7);
62 x.words[2] ^= R(x.words[1] + x.words[0], 9);
63 x.words[3] ^= R(x.words[2] + x.words[1], 13);
64 x.words[0] ^= R(x.words[3] + x.words[2], 18);
65 x.words[6] ^= R(x.words[5] + x.words[4], 7);
66 x.words[7] ^= R(x.words[6] + x.words[5], 9);
67 x.words[4] ^= R(x.words[7] + x.words[6], 13);
68 x.words[5] ^= R(x.words[4] + x.words[7], 18);
69 x.words[11] ^= R(x.words[10] + x.words[9], 7);
70 x.words[8] ^= R(x.words[11] + x.words[10], 9);
71 x.words[9] ^= R(x.words[8] + x.words[11], 13);
72 x.words[10] ^= R(x.words[9] + x.words[8], 18);
73 x.words[12] ^= R(x.words[15] + x.words[14], 7);
74 x.words[13] ^= R(x.words[12] + x.words[15], 9);
75 x.words[14] ^= R(x.words[13] + x.words[12], 13);
76 x.words[15] ^= R(x.words[14] + x.words[13], 18);
77 }
78
79 for (int i = 0; i < 16; ++i) {
80 inout->words[i] += x.words[i];
81 }
82}
83
84// xor_block sets |*out| to be |*a| XOR |*b|.
85static void xor_block(block_t *out, const block_t *a, const block_t *b) {
86 for (size_t i = 0; i < 16; i++) {
87 out->words[i] = a->words[i] ^ b->words[i];
88 }
89}
90
91// scryptBlockMix implements the function described in RFC 7914, section 4. B'
92// is written to |out|. |out| and |B| may not alias and must be each one scrypt
93// block (2 * |r| Salsa20 blocks) long.
94static void scryptBlockMix(block_t *out, const block_t *B, uint64_t r) {
95 assert(out != B);
96
97 block_t X;
98 OPENSSL_memcpy(&X, &B[r * 2 - 1], sizeof(X));
99 for (uint64_t i = 0; i < r * 2; i++) {
100 xor_block(&X, &X, &B[i]);
101 salsa208_word_specification(&X);
102
103 // This implements the permutation in step 3.
104 OPENSSL_memcpy(&out[i / 2 + (i & 1) * r], &X, sizeof(X));
105 }
106}
107
108// scryptROMix implements the function described in RFC 7914, section 5. |B| is
109// an scrypt block (2 * |r| Salsa20 blocks) and is modified in-place. |T| and
110// |V| are scratch space allocated by the caller. |T| must have space for one
111// scrypt block (2 * |r| Salsa20 blocks). |V| must have space for |N| scrypt
112// blocks (2 * |r| * |N| Salsa20 blocks).
113static void scryptROMix(block_t *B, uint64_t r, uint64_t N, block_t *T,
114 block_t *V) {
115 // Steps 1 and 2.
116 OPENSSL_memcpy(V, B, 2 * r * sizeof(block_t));
117 for (uint64_t i = 1; i < N; i++) {
118 scryptBlockMix(&V[2 * r * i /* scrypt block i */],
119 &V[2 * r * (i - 1) /* scrypt block i-1 */], r);
120 }
121 scryptBlockMix(B, &V[2 * r * (N - 1) /* scrypt block N-1 */], r);
122
123 // Step 3.
124 for (uint64_t i = 0; i < N; i++) {
125 // Note this assumes |N| <= 2^32 and is a power of 2.
126 uint32_t j = B[2 * r - 1].words[0] & (N - 1);
127 for (size_t k = 0; k < 2 * r; k++) {
128 xor_block(&T[k], &B[k], &V[2 * r * j + k]);
129 }
130 scryptBlockMix(B, T, r);
131 }
132}
133
134// SCRYPT_PR_MAX is the maximum value of p * r. This is equivalent to the
135// bounds on p in section 6:
136//
137// p <= ((2^32-1) * hLen) / MFLen iff
138// p <= ((2^32-1) * 32) / (128 * r) iff
139// p * r <= (2^30-1)
140#define SCRYPT_PR_MAX ((1 << 30) - 1)
141
142// SCRYPT_MAX_MEM is the default maximum memory that may be allocated by
143// |EVP_PBE_scrypt|.
144#define SCRYPT_MAX_MEM (1024 * 1024 * 32)
145
146int EVP_PBE_scrypt(const char *password, size_t password_len,
147 const uint8_t *salt, size_t salt_len, uint64_t N, uint64_t r,
148 uint64_t p, size_t max_mem, uint8_t *out_key,
149 size_t key_len) {
150 if (r == 0 || p == 0 || p > SCRYPT_PR_MAX / r ||
151 // |N| must be a power of two.
152 N < 2 || (N & (N - 1)) ||
153 // We only support |N| <= 2^32 in |scryptROMix|.
154 N > UINT64_C(1) << 32 ||
155 // Check that |N| < 2^(128×r / 8).
156 (16 * r <= 63 && N >= UINT64_C(1) << (16 * r))) {
157 OPENSSL_PUT_ERROR(EVP, EVP_R_INVALID_PARAMETERS);
158 return 0;
159 }
160
161 // Determine the amount of memory needed. B, T, and V are |p|, 1, and |N|
162 // scrypt blocks, respectively. Each scrypt block is 2*|r| |block_t|s.
163 if (max_mem == 0) {
164 max_mem = SCRYPT_MAX_MEM;
165 }
166
167 size_t max_scrypt_blocks = max_mem / (2 * r * sizeof(block_t));
168 if (max_scrypt_blocks < p + 1 ||
169 max_scrypt_blocks - p - 1 < N) {
170 OPENSSL_PUT_ERROR(EVP, EVP_R_MEMORY_LIMIT_EXCEEDED);
171 return 0;
172 }
173
174 // Allocate and divide up the scratch space. |max_mem| fits in a size_t, which
175 // is no bigger than uint64_t, so none of these operations may overflow.
176 OPENSSL_STATIC_ASSERT(UINT64_MAX >= ((size_t)-1), "size_t exceeds uint64_t");
177 size_t B_blocks = p * 2 * r;
178 size_t B_bytes = B_blocks * sizeof(block_t);
179 size_t T_blocks = 2 * r;
180 size_t V_blocks = N * 2 * r;
181 block_t *B = OPENSSL_malloc((B_blocks + T_blocks + V_blocks) * sizeof(block_t));
182 if (B == NULL) {
183 OPENSSL_PUT_ERROR(EVP, ERR_R_MALLOC_FAILURE);
184 return 0;
185 }
186
187 int ret = 0;
188 block_t *T = B + B_blocks;
189 block_t *V = T + T_blocks;
190
191 // NOTE: PKCS5_PBKDF2_HMAC can only fail due to allocation failure
192 // or |iterations| of 0 (we pass 1 here). This is consistent with
193 // the documented failure conditions of EVP_PBE_scrypt.
194 if (!PKCS5_PBKDF2_HMAC(password, password_len, salt, salt_len, 1,
195 EVP_sha256(), B_bytes, (uint8_t *)B)) {
196 goto err;
197 }
198
199 for (uint64_t i = 0; i < p; i++) {
200 scryptROMix(B + 2 * r * i, r, N, T, V);
201 }
202
203 if (!PKCS5_PBKDF2_HMAC(password, password_len, (const uint8_t *)B, B_bytes, 1,
204 EVP_sha256(), key_len, out_key)) {
205 goto err;
206 }
207
208 ret = 1;
209
210err:
211 OPENSSL_free(B);
212 return ret;
213}
214