1/*
2 * Copyright 2019-2021 The OpenSSL Project Authors. All Rights Reserved.
3 *
4 * Licensed under the Apache License 2.0 (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/* chacha20 cipher implementation */
11
12#include "cipher_chacha20.h"
13
14static int chacha20_initkey(PROV_CIPHER_CTX *bctx, const uint8_t *key,
15                            size_t keylen)
16{
17    PROV_CHACHA20_CTX *ctx = (PROV_CHACHA20_CTX *)bctx;
18    unsigned int i;
19
20    if (key != NULL) {
21        for (i = 0; i < CHACHA_KEY_SIZE; i += 4)
22            ctx->key.d[i / 4] = CHACHA_U8TOU32(key + i);
23    }
24    ctx->partial_len = 0;
25    return 1;
26}
27
28static int chacha20_initiv(PROV_CIPHER_CTX *bctx)
29{
30    PROV_CHACHA20_CTX *ctx = (PROV_CHACHA20_CTX *)bctx;
31    unsigned int i;
32
33    if (bctx->iv_set) {
34        for (i = 0; i < CHACHA_CTR_SIZE; i += 4)
35            ctx->counter[i / 4] = CHACHA_U8TOU32(bctx->oiv + i);
36    }
37    ctx->partial_len = 0;
38    return 1;
39}
40
41static int chacha20_cipher(PROV_CIPHER_CTX *bctx, unsigned char *out,
42                           const unsigned char *in, size_t inl)
43{
44    PROV_CHACHA20_CTX *ctx = (PROV_CHACHA20_CTX *)bctx;
45    unsigned int n, rem, ctr32;
46
47    n = ctx->partial_len;
48    if (n > 0) {
49        while (inl > 0 && n < CHACHA_BLK_SIZE) {
50            *out++ = *in++ ^ ctx->buf[n++];
51            inl--;
52        }
53        ctx->partial_len = n;
54
55        if (inl == 0)
56            return 1;
57
58        if (n == CHACHA_BLK_SIZE) {
59            ctx->partial_len = 0;
60            ctx->counter[0]++;
61            if (ctx->counter[0] == 0)
62                ctx->counter[1]++;
63        }
64    }
65
66    rem = (unsigned int)(inl % CHACHA_BLK_SIZE);
67    inl -= rem;
68    ctr32 = ctx->counter[0];
69    while (inl >= CHACHA_BLK_SIZE) {
70        size_t blocks = inl / CHACHA_BLK_SIZE;
71
72        /*
73         * 1<<28 is just a not-so-small yet not-so-large number...
74         * Below condition is practically never met, but it has to
75         * be checked for code correctness.
76         */
77        if (sizeof(size_t) > sizeof(unsigned int) && blocks > (1U << 28))
78            blocks = (1U << 28);
79
80        /*
81         * As ChaCha20_ctr32 operates on 32-bit counter, caller
82         * has to handle overflow. 'if' below detects the
83         * overflow, which is then handled by limiting the
84         * amount of blocks to the exact overflow point...
85         */
86        ctr32 += (unsigned int)blocks;
87        if (ctr32 < blocks) {
88            blocks -= ctr32;
89            ctr32 = 0;
90        }
91        blocks *= CHACHA_BLK_SIZE;
92        ChaCha20_ctr32(out, in, blocks, ctx->key.d, ctx->counter);
93        inl -= blocks;
94        in += blocks;
95        out += blocks;
96
97        ctx->counter[0] = ctr32;
98        if (ctr32 == 0) ctx->counter[1]++;
99    }
100
101    if (rem > 0) {
102        memset(ctx->buf, 0, sizeof(ctx->buf));
103        ChaCha20_ctr32(ctx->buf, ctx->buf, CHACHA_BLK_SIZE,
104                       ctx->key.d, ctx->counter);
105        for (n = 0; n < rem; n++)
106            out[n] = in[n] ^ ctx->buf[n];
107        ctx->partial_len = rem;
108    }
109
110    return 1;
111}
112
113static const PROV_CIPHER_HW_CHACHA20 chacha20_hw = {
114    { chacha20_initkey, chacha20_cipher },
115    chacha20_initiv
116};
117
118const PROV_CIPHER_HW *ossl_prov_cipher_hw_chacha20(size_t keybits)
119{
120    return (PROV_CIPHER_HW *)&chacha20_hw;
121}
122
123