lilcrypto/cipher_chacha20.c

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/*
* Copyright (c) 2024 Lucas Gabriel Vuotto <lucas@lgv5.net>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <limits.h>
#include <stdlib.h>
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#include "lilcrypto.h"
#include "cipher.h"
#include "impl_chacha20.h"
#include "util.h"
/*
* Implements ChaCha20 according to RFC 8439, XChaCha20 according to
* draft-irtf-cfrg-xchacha-03.
*/
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static int
chacha20_anycrypt_init(void *arg, const void *initparams)
{
const struct lc_chacha20_params *params = initparams;
struct chacha20_ctx *ctx = arg;
size_t i;
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for (i = 0; i < CHACHA20_BLOCKLEN_WORDS; i++)
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ctx->s[i] = 0;
for (i = 0; i < CHACHA20_KEY_WORDS; i++)
ctx->k[i] = load32le(&params->key[i * 4]);
ctx->n[0] = params->counter;
for (i = 1; i < CHACHA20_NONCE_WORDS; i++)
ctx->n[i] = load32le(&params->nonce[(i - 1) * 4]);
ctx->mlen = 0;
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return 1;
}
static int
xchacha20_anycrypt_init(void *arg, const void *initparams)
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{
const struct lc_xchacha20_params *params = initparams;
struct chacha20_ctx *ctx = arg;
size_t i;
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for (i = 0; i < CHACHA20_BLOCKLEN_WORDS; i++)
ctx->s[i] = 0;
for (i = 0; i < CHACHA20_KEY_WORDS; i++)
ctx->k[i] = load32le(&params->key[i * 4]);
for (i = 0; i < CHACHA20_NONCE_WORDS; i++)
ctx->n[i] = load32le(&params->nonce[i * 4]);
ctx->mlen = 0;
hchacha20_block(ctx);
ctx->k[0] = ctx->s[0];
ctx->k[1] = ctx->s[1];
ctx->k[2] = ctx->s[2];
ctx->k[3] = ctx->s[3];
ctx->k[4] = ctx->s[12];
ctx->k[5] = ctx->s[13];
ctx->k[6] = ctx->s[14];
ctx->k[7] = ctx->s[15];
ctx->n[0] = params->counter;
ctx->n[1] = 0;
ctx->n[2] = load32le(&params->nonce[16]);
ctx->n[3] = load32le(&params->nonce[20]);
return 1;
}
static int
chacha20_anycrypt_update(void *arg, uint8_t *out, size_t *outlen,
const uint8_t *in, size_t inlen)
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{
struct chacha20_ctx *ctx = arg;
size_t i, blocks;
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uint32_t h;
*outlen = 0;
if (inlen > SIZE_MAX - (LC_CHACHA20_BLOCKLEN - 1) - ctx->mlen)
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return 0;
blocks = (inlen + ctx->mlen + LC_CHACHA20_BLOCKLEN - 1) /
LC_CHACHA20_BLOCKLEN;
if (blocks + ctx->n[0] > CHACHA20_CTRMAX)
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return 0;
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*outlen = ctx->mlen + inlen -
((ctx->mlen + inlen) % LC_CHACHA20_BLOCKLEN);
if (out == NULL)
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return 1;
for (i = 0; i + ctx->mlen < LC_CHACHA20_BLOCKLEN && i < inlen; i++)
ctx->m[i + ctx->mlen] = in[i];
ctx->mlen += i;
in += i;
inlen -= i;
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if (ctx->mlen == LC_CHACHA20_BLOCKLEN) {
chacha20_block(ctx);
ctx->n[0]++;
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for (i = 0; i < CHACHA20_BLOCKLEN_WORDS; i++) {
h = load32le(&ctx->m[i * 4]);
h ^= ctx->s[i];
store32le(&out[i * 4], h);
}
out += LC_CHACHA20_BLOCKLEN;
ctx->mlen = 0;
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}
if (inlen == 0)
return 1;
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while (inlen >= LC_CHACHA20_BLOCKLEN) {
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chacha20_block(ctx);
ctx->n[0]++;
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for (i = 0; i < CHACHA20_BLOCKLEN_WORDS; i++) {
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h = load32le(&in[i * 4]);
h ^= ctx->s[i];
store32le(&out[i * 4], h);
}
out += LC_CHACHA20_BLOCKLEN;
in += LC_CHACHA20_BLOCKLEN;
inlen -= LC_CHACHA20_BLOCKLEN;
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}
for (i = 0; i < inlen; i++)
ctx->m[i] = in[i];
ctx->mlen = inlen;
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return 1;
}
static int
chacha20_anycrypt_final(void *arg, uint8_t *out, size_t *outlen)
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{
struct chacha20_ctx *ctx = arg;
size_t i, off;
uint32_t h;
uint8_t s[4];
*outlen = ctx->mlen;
if (out == NULL)
return 1;
if (ctx->mlen > 0)
chacha20_block(ctx);
for (i = 0; i < ctx->mlen / 4; i++) {
h = load32le(&ctx->m[i * 4]);
h ^= ctx->s[i];
store32le(&out[i * 4], h);
}
off = i * 4;
ctx->mlen -= off;
out += off;
store32le(&s[0], ctx->s[i]);
for (i = 0; i < ctx->mlen; i++)
out[i] = ctx->m[i + off] ^ s[i];
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lc_scrub(ctx, sizeof(*ctx));
return 1;
}
static int
chacha20_anycrypt(uint8_t *out, size_t *outlen, const void *initparams,
const uint8_t *in, size_t inlen)
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{
struct chacha20_ctx ctx;
size_t l0, l1;
int rc;
*outlen = 0;
if (inlen > SIZE_MAX - (LC_CHACHA20_BLOCKLEN - 1) ||
(inlen + LC_CHACHA20_BLOCKLEN - 1) / LC_CHACHA20_BLOCKLEN >
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CHACHA20_CTRMAX)
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return 0;
if (out == NULL) {
*outlen = inlen;
return 1;
}
rc = chacha20_anycrypt_init(&ctx, initparams) &&
chacha20_anycrypt_update(&ctx, out, &l0, in, inlen) &&
chacha20_anycrypt_final(&ctx, out + l0, &l1);
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if (rc)
*outlen = l0 + l1;
return rc;
}
static void *
chacha20_ctx_new(void)
{
return malloc(sizeof(struct chacha20_ctx));
}
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static struct lc_cipher_impl chacha20_impl = {
.encrypt_init = &chacha20_anycrypt_init,
.encrypt_update = &chacha20_anycrypt_update,
.encrypt_final = &chacha20_anycrypt_final,
.encrypt = &chacha20_anycrypt,
.decrypt_init = &chacha20_anycrypt_init,
.decrypt_update = &chacha20_anycrypt_update,
.decrypt_final = &chacha20_anycrypt_final,
.decrypt = &chacha20_anycrypt,
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.ctx_new = &chacha20_ctx_new,
.ctx_free = NULL,
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};
static struct lc_cipher_impl xchacha20_impl = {
.encrypt_init = &xchacha20_anycrypt_init,
.encrypt_update = &chacha20_anycrypt_update,
.encrypt_final = &chacha20_anycrypt_final,
.encrypt = &chacha20_anycrypt,
.decrypt_init = &xchacha20_anycrypt_init,
.decrypt_update = &chacha20_anycrypt_update,
.decrypt_final = &chacha20_anycrypt_final,
.decrypt = &chacha20_anycrypt,
.ctx_new = &chacha20_ctx_new,
.ctx_free = NULL,
};
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const struct lc_cipher_impl *
lc_cipher_impl_chacha20(void)
{
return &chacha20_impl;
}
const struct lc_cipher_impl *
lc_cipher_impl_xchacha20(void)
{
return &xchacha20_impl;
}