library/chacha20.c

/**
 * \file chacha20.c
 *
 * \brief ChaCha20 cipher.
 *
 * \author Daniel King <damaki.gh@gmail.com>
 *
 *  Copyright The Mbed TLS Contributors
 *  SPDX-License-Identifier: Apache-2.0
 *
 *  Licensed under the Apache License, Version 2.0 (the "License"); you may
 *  not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

#include "common.h"

#if defined(MBEDTLS_CHACHA20_C)

#    include "mbedtls/chacha20.h"
#    include "mbedtls/platform_util.h"
#    include "mbedtls/error.h"

#    include <stddef.h>
#    include <string.h>

#    if defined(MBEDTLS_SELF_TEST)
#        if defined(MBEDTLS_PLATFORM_C)
#            include "mbedtls/platform.h"
#        else
#            include <stdio.h>
#            define mbedtls_printf printf
#        endif /* MBEDTLS_PLATFORM_C */
#    endif /* MBEDTLS_SELF_TEST */

#    if !defined(MBEDTLS_CHACHA20_ALT)

#        if (defined(__ARMCC_VERSION) || defined(_MSC_VER)) && \
            !defined(inline) && !defined(__cplusplus)
#            define inline __inline
#        endif

/* Parameter validation macros */
#        define CHACHA20_VALIDATE_RET(cond)     \
            MBEDTLS_INTERNAL_VALIDATE_RET(cond, \
                                          MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA)
#        define CHACHA20_VALIDATE(cond) MBEDTLS_INTERNAL_VALIDATE(cond)

#        define BYTES_TO_U32_LE(data, offset)                   \
            ((uint32_t)(data)[offset] |                         \
             (uint32_t)((uint32_t)(data)[(offset) + 1] << 8) |  \
             (uint32_t)((uint32_t)(data)[(offset) + 2] << 16) | \
             (uint32_t)((uint32_t)(data)[(offset) + 3] << 24))

#        define ROTL32(value, amount) \
            ((uint32_t)((value) << (amount)) | ((value) >> (32 - (amount))))

#        define CHACHA20_CTR_INDEX (12U)

#        define CHACHA20_BLOCK_SIZE_BYTES (4U * 16U)

/**
 * \brief           ChaCha20 quarter round operation.
 *
 *                  The quarter round is defined as follows (from RFC 7539):
 *                      1.  a += b; d ^= a; d <<<= 16;
 *                      2.  c += d; b ^= c; b <<<= 12;
 *                      3.  a += b; d ^= a; d <<<= 8;
 *                      4.  c += d; b ^= c; b <<<= 7;
 *
 * \param state     ChaCha20 state to modify.
 * \param a         The index of 'a' in the state.
 * \param b         The index of 'b' in the state.
 * \param c         The index of 'c' in the state.
 * \param d         The index of 'd' in the state.
 */
static inline void chacha20_quarter_round(uint32_t state[16],
                                          size_t a,
                                          size_t b,
                                          size_t c,
                                          size_t d)
{
    /* a += b; d ^= a; d <<<= 16; */
    state[a] += state[b];
    state[d] ^= state[a];
    state[d] = ROTL32(state[d], 16);

    /* c += d; b ^= c; b <<<= 12 */
    state[c] += state[d];
    state[b] ^= state[c];
    state[b] = ROTL32(state[b], 12);

    /* a += b; d ^= a; d <<<= 8; */
    state[a] += state[b];
    state[d] ^= state[a];
    state[d] = ROTL32(state[d], 8);

    /* c += d; b ^= c; b <<<= 7; */
    state[c] += state[d];
    state[b] ^= state[c];
    state[b] = ROTL32(state[b], 7);
}

/**
 * \brief           Perform the ChaCha20 inner block operation.
 *
 *                  This function performs two rounds: the column round and the
 *                  diagonal round.
 *
 * \param state     The ChaCha20 state to update.
 */
static void chacha20_inner_block(uint32_t state[16])
{
    chacha20_quarter_round(state, 0, 4, 8, 12);
    chacha20_quarter_round(state, 1, 5, 9, 13);
    chacha20_quarter_round(state, 2, 6, 10, 14);
    chacha20_quarter_round(state, 3, 7, 11, 15);

    chacha20_quarter_round(state, 0, 5, 10, 15);
    chacha20_quarter_round(state, 1, 6, 11, 12);
    chacha20_quarter_round(state, 2, 7, 8, 13);
    chacha20_quarter_round(state, 3, 4, 9, 14);
}

/**
 * \brief               Generates a keystream block.
 *
 * \param initial_state The initial ChaCha20 state (key, nonce, counter).
 * \param keystream     Generated keystream bytes are written to this buffer.
 */
static void chacha20_block(const uint32_t initial_state[16],
                           unsigned char keystream[64])
{
    uint32_t working_state[16];
    size_t i;

    memcpy(working_state, initial_state, CHACHA20_BLOCK_SIZE_BYTES);

    for (i = 0U; i < 10U; i++)
        chacha20_inner_block(working_state);

    working_state[0] += initial_state[0];
    working_state[1] += initial_state[1];
    working_state[2] += initial_state[2];
    working_state[3] += initial_state[3];
    working_state[4] += initial_state[4];
    working_state[5] += initial_state[5];
    working_state[6] += initial_state[6];
    working_state[7] += initial_state[7];
    working_state[8] += initial_state[8];
    working_state[9] += initial_state[9];
    working_state[10] += initial_state[10];
    working_state[11] += initial_state[11];
    working_state[12] += initial_state[12];
    working_state[13] += initial_state[13];
    working_state[14] += initial_state[14];
    working_state[15] += initial_state[15];

    for (i = 0U; i < 16; i++) {
        size_t offset = i * 4U;

        keystream[offset] = (unsigned char)(working_state[i]);
        keystream[offset + 1U] = (unsigned char)(working_state[i] >> 8);
        keystream[offset + 2U] = (unsigned char)(working_state[i] >> 16);
        keystream[offset + 3U] = (unsigned char)(working_state[i] >> 24);
    }

    mbedtls_platform_zeroize(working_state, sizeof(working_state));
}

void mbedtls_chacha20_init(mbedtls_chacha20_context *ctx)
{
    CHACHA20_VALIDATE(ctx != NULL);

    mbedtls_platform_zeroize(ctx->state, sizeof(ctx->state));
    mbedtls_platform_zeroize(ctx->keystream8, sizeof(ctx->keystream8));

    /* Initially, there's no keystream bytes available */
    ctx->keystream_bytes_used = CHACHA20_BLOCK_SIZE_BYTES;
}

void mbedtls_chacha20_free(mbedtls_chacha20_context *ctx)
{
    if (ctx != NULL) {
        mbedtls_platform_zeroize(ctx, sizeof(mbedtls_chacha20_context));
    }
}

int mbedtls_chacha20_setkey(mbedtls_chacha20_context *ctx,
                            const unsigned char key[32])
{
    CHACHA20_VALIDATE_RET(ctx != NULL);
    CHACHA20_VALIDATE_RET(key != NULL);

    /* ChaCha20 constants - the string "expand 32-byte k" */
    ctx->state[0] = 0x61707865;
    ctx->state[1] = 0x3320646e;
    ctx->state[2] = 0x79622d32;
    ctx->state[3] = 0x6b206574;

    /* Set key */
    ctx->state[4] = BYTES_TO_U32_LE(key, 0);
    ctx->state[5] = BYTES_TO_U32_LE(key, 4);
    ctx->state[6] = BYTES_TO_U32_LE(key, 8);
    ctx->state[7] = BYTES_TO_U32_LE(key, 12);
    ctx->state[8] = BYTES_TO_U32_LE(key, 16);
    ctx->state[9] = BYTES_TO_U32_LE(key, 20);
    ctx->state[10] = BYTES_TO_U32_LE(key, 24);
    ctx->state[11] = BYTES_TO_U32_LE(key, 28);

    return 0;
}

int mbedtls_chacha20_starts(mbedtls_chacha20_context *ctx,
                            const unsigned char nonce[12],
                            uint32_t counter)
{
    CHACHA20_VALIDATE_RET(ctx != NULL);
    CHACHA20_VALIDATE_RET(nonce != NULL);

    /* Counter */
    ctx->state[12] = counter;

    /* Nonce */
    ctx->state[13] = BYTES_TO_U32_LE(nonce, 0);
    ctx->state[14] = BYTES_TO_U32_LE(nonce, 4);
    ctx->state[15] = BYTES_TO_U32_LE(nonce, 8);

    mbedtls_platform_zeroize(ctx->keystream8, sizeof(ctx->keystream8));

    /* Initially, there's no keystream bytes available */
    ctx->keystream_bytes_used = CHACHA20_BLOCK_SIZE_BYTES;

    return 0;
}

int mbedtls_chacha20_update(mbedtls_chacha20_context *ctx,
                            size_t size,
                            const unsigned char *input,
                            unsigned char *output)
{
    size_t offset = 0U;
    size_t i;

    CHACHA20_VALIDATE_RET(ctx != NULL);
    CHACHA20_VALIDATE_RET(size == 0 || input != NULL);
    CHACHA20_VALIDATE_RET(size == 0 || output != NULL);

    /* Use leftover keystream bytes, if available */
    while (size > 0U && ctx->keystream_bytes_used < CHACHA20_BLOCK_SIZE_BYTES) {
        output[offset] = input[offset] ^
                         ctx->keystream8[ctx->keystream_bytes_used];

        ctx->keystream_bytes_used++;
        offset++;
        size--;
    }

    /* Process full blocks */
    while (size >= CHACHA20_BLOCK_SIZE_BYTES) {
        /* Generate new keystream block and increment counter */
        chacha20_block(ctx->state, ctx->keystream8);
        ctx->state[CHACHA20_CTR_INDEX]++;

        for (i = 0U; i < 64U; i += 8U) {
            output[offset + i] = input[offset + i] ^ ctx->keystream8[i];
            output[offset + i + 1] = input[offset + i + 1] ^
                                     ctx->keystream8[i + 1];
            output[offset + i + 2] = input[offset + i + 2] ^
                                     ctx->keystream8[i + 2];
            output[offset + i + 3] = input[offset + i + 3] ^
                                     ctx->keystream8[i + 3];
            output[offset + i + 4] = input[offset + i + 4] ^
                                     ctx->keystream8[i + 4];
            output[offset + i + 5] = input[offset + i + 5] ^
                                     ctx->keystream8[i + 5];
            output[offset + i + 6] = input[offset + i + 6] ^
                                     ctx->keystream8[i + 6];
            output[offset + i + 7] = input[offset + i + 7] ^
                                     ctx->keystream8[i + 7];
        }

        offset += CHACHA20_BLOCK_SIZE_BYTES;
        size -= CHACHA20_BLOCK_SIZE_BYTES;
    }

    /* Last (partial) block */
    if (size > 0U) {
        /* Generate new keystream block and increment counter */
        chacha20_block(ctx->state, ctx->keystream8);
        ctx->state[CHACHA20_CTR_INDEX]++;

        for (i = 0U; i < size; i++) {
            output[offset + i] = input[offset + i] ^ ctx->keystream8[i];
        }

        ctx->keystream_bytes_used = size;
    }

    return 0;
}

int mbedtls_chacha20_crypt(const unsigned char key[32],
                           const unsigned char nonce[12],
                           uint32_t counter,
                           size_t data_len,
                           const unsigned char *input,
                           unsigned char *output)
{
    mbedtls_chacha20_context ctx;
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

    CHACHA20_VALIDATE_RET(key != NULL);
    CHACHA20_VALIDATE_RET(nonce != NULL);
    CHACHA20_VALIDATE_RET(data_len == 0 || input != NULL);
    CHACHA20_VALIDATE_RET(data_len == 0 || output != NULL);

    mbedtls_chacha20_init(&ctx);

    ret = mbedtls_chacha20_setkey(&ctx, key);
    if (ret != 0)
        goto cleanup;

    ret = mbedtls_chacha20_starts(&ctx, nonce, counter);
    if (ret != 0)
        goto cleanup;

    ret = mbedtls_chacha20_update(&ctx, data_len, input, output);

cleanup:
    mbedtls_chacha20_free(&ctx);
    return ret;
}

#    endif /* !MBEDTLS_CHACHA20_ALT */

#    if defined(MBEDTLS_SELF_TEST)

static const unsigned char test_keys[2][32] = {
    { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 },
    { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01 }
};

static const unsigned char test_nonces[2][12] = {
    { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 },
    { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02 }
};

static const uint32_t test_counters[2] = { 0U, 1U };

static const unsigned char test_input[2][375] = {
    { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 },
    { 0x41, 0x6e, 0x79, 0x20, 0x73, 0x75, 0x62, 0x6d, 0x69, 0x73, 0x73, 0x69,
      0x6f, 0x6e, 0x20, 0x74, 0x6f, 0x20, 0x74, 0x68, 0x65, 0x20, 0x49, 0x45,
      0x54, 0x46, 0x20, 0x69, 0x6e, 0x74, 0x65, 0x6e, 0x64, 0x65, 0x64, 0x20,
      0x62, 0x79, 0x20, 0x74, 0x68, 0x65, 0x20, 0x43, 0x6f, 0x6e, 0x74, 0x72,
      0x69, 0x62, 0x75, 0x74, 0x6f, 0x72, 0x20, 0x66, 0x6f, 0x72, 0x20, 0x70,
      0x75, 0x62, 0x6c, 0x69, 0x63, 0x61, 0x74, 0x69, 0x6f, 0x6e, 0x20, 0x61,
      0x73, 0x20, 0x61, 0x6c, 0x6c, 0x20, 0x6f, 0x72, 0x20, 0x70, 0x61, 0x72,
      0x74, 0x20, 0x6f, 0x66, 0x20, 0x61, 0x6e, 0x20, 0x49, 0x45, 0x54, 0x46,
      0x20, 0x49, 0x6e, 0x74, 0x65, 0x72, 0x6e, 0x65, 0x74, 0x2d, 0x44, 0x72,
      0x61, 0x66, 0x74, 0x20, 0x6f, 0x72, 0x20, 0x52, 0x46, 0x43, 0x20, 0x61,
      0x6e, 0x64, 0x20, 0x61, 0x6e, 0x79, 0x20, 0x73, 0x74, 0x61, 0x74, 0x65,
      0x6d, 0x65, 0x6e, 0x74, 0x20, 0x6d, 0x61, 0x64, 0x65, 0x20, 0x77, 0x69,
      0x74, 0x68, 0x69, 0x6e, 0x20, 0x74, 0x68, 0x65, 0x20, 0x63, 0x6f, 0x6e,
      0x74, 0x65, 0x78, 0x74, 0x20, 0x6f, 0x66, 0x20, 0x61, 0x6e, 0x20, 0x49,
      0x45, 0x54, 0x46, 0x20, 0x61, 0x63, 0x74, 0x69, 0x76, 0x69, 0x74, 0x79,
      0x20, 0x69, 0x73, 0x20, 0x63, 0x6f, 0x6e, 0x73, 0x69, 0x64, 0x65, 0x72,
      0x65, 0x64, 0x20, 0x61, 0x6e, 0x20, 0x22, 0x49, 0x45, 0x54, 0x46, 0x20,
      0x43, 0x6f, 0x6e, 0x74, 0x72, 0x69, 0x62, 0x75, 0x74, 0x69, 0x6f, 0x6e,
      0x22, 0x2e, 0x20, 0x53, 0x75, 0x63, 0x68, 0x20, 0x73, 0x74, 0x61, 0x74,
      0x65, 0x6d, 0x65, 0x6e, 0x74, 0x73, 0x20, 0x69, 0x6e, 0x63, 0x6c, 0x75,
      0x64, 0x65, 0x20, 0x6f, 0x72, 0x61, 0x6c, 0x20, 0x73, 0x74, 0x61, 0x74,
      0x65, 0x6d, 0x65, 0x6e, 0x74, 0x73, 0x20, 0x69, 0x6e, 0x20, 0x49, 0x45,
      0x54, 0x46, 0x20, 0x73, 0x65, 0x73, 0x73, 0x69, 0x6f, 0x6e, 0x73, 0x2c,
      0x20, 0x61, 0x73, 0x20, 0x77, 0x65, 0x6c, 0x6c, 0x20, 0x61, 0x73, 0x20,
      0x77, 0x72, 0x69, 0x74, 0x74, 0x65, 0x6e, 0x20, 0x61, 0x6e, 0x64, 0x20,
      0x65, 0x6c, 0x65, 0x63, 0x74, 0x72, 0x6f, 0x6e, 0x69, 0x63, 0x20, 0x63,
      0x6f, 0x6d, 0x6d, 0x75, 0x6e, 0x69, 0x63, 0x61, 0x74, 0x69, 0x6f, 0x6e,
      0x73, 0x20, 0x6d, 0x61, 0x64, 0x65, 0x20, 0x61, 0x74, 0x20, 0x61, 0x6e,
      0x79, 0x20, 0x74, 0x69, 0x6d, 0x65, 0x20, 0x6f, 0x72, 0x20, 0x70, 0x6c,
      0x61, 0x63, 0x65, 0x2c, 0x20, 0x77, 0x68, 0x69, 0x63, 0x68, 0x20, 0x61,
      0x72, 0x65, 0x20, 0x61, 0x64, 0x64, 0x72, 0x65, 0x73, 0x73, 0x65, 0x64,
      0x20, 0x74, 0x6f }
};

static const unsigned char test_output[2][375] = {
    { 0x76, 0xb8, 0xe0, 0xad, 0xa0, 0xf1, 0x3d, 0x90, 0x40, 0x5d, 0x6a,
      0xe5, 0x53, 0x86, 0xbd, 0x28, 0xbd, 0xd2, 0x19, 0xb8, 0xa0, 0x8d,
      0xed, 0x1a, 0xa8, 0x36, 0xef, 0xcc, 0x8b, 0x77, 0x0d, 0xc7, 0xda,
      0x41, 0x59, 0x7c, 0x51, 0x57, 0x48, 0x8d, 0x77, 0x24, 0xe0, 0x3f,
      0xb8, 0xd8, 0x4a, 0x37, 0x6a, 0x43, 0xb8, 0xf4, 0x15, 0x18, 0xa1,
      0x1c, 0xc3, 0x87, 0xb6, 0x69, 0xb2, 0xee, 0x65, 0x86 },
    { 0xa3, 0xfb, 0xf0, 0x7d, 0xf3, 0xfa, 0x2f, 0xde, 0x4f, 0x37, 0x6c, 0xa2,
      0x3e, 0x82, 0x73, 0x70, 0x41, 0x60, 0x5d, 0x9f, 0x4f, 0x4f, 0x57, 0xbd,
      0x8c, 0xff, 0x2c, 0x1d, 0x4b, 0x79, 0x55, 0xec, 0x2a, 0x97, 0x94, 0x8b,
      0xd3, 0x72, 0x29, 0x15, 0xc8, 0xf3, 0xd3, 0x37, 0xf7, 0xd3, 0x70, 0x05,
      0x0e, 0x9e, 0x96, 0xd6, 0x47, 0xb7, 0xc3, 0x9f, 0x56, 0xe0, 0x31, 0xca,
      0x5e, 0xb6, 0x25, 0x0d, 0x40, 0x42, 0xe0, 0x27, 0x85, 0xec, 0xec, 0xfa,
      0x4b, 0x4b, 0xb5, 0xe8, 0xea, 0xd0, 0x44, 0x0e, 0x20, 0xb6, 0xe8, 0xdb,
      0x09, 0xd8, 0x81, 0xa7, 0xc6, 0x13, 0x2f, 0x42, 0x0e, 0x52, 0x79, 0x50,
      0x42, 0xbd, 0xfa, 0x77, 0x73, 0xd8, 0xa9, 0x05, 0x14, 0x47, 0xb3, 0x29,
      0x1c, 0xe1, 0x41, 0x1c, 0x68, 0x04, 0x65, 0x55, 0x2a, 0xa6, 0xc4, 0x05,
      0xb7, 0x76, 0x4d, 0x5e, 0x87, 0xbe, 0xa8, 0x5a, 0xd0, 0x0f, 0x84, 0x49,
      0xed, 0x8f, 0x72, 0xd0, 0xd6, 0x62, 0xab, 0x05, 0x26, 0x91, 0xca, 0x66,
      0x42, 0x4b, 0xc8, 0x6d, 0x2d, 0xf8, 0x0e, 0xa4, 0x1f, 0x43, 0xab, 0xf9,
      0x37, 0xd3, 0x25, 0x9d, 0xc4, 0xb2, 0xd0, 0xdf, 0xb4, 0x8a, 0x6c, 0x91,
      0x39, 0xdd, 0xd7, 0xf7, 0x69, 0x66, 0xe9, 0x28, 0xe6, 0x35, 0x55, 0x3b,
      0xa7, 0x6c, 0x5c, 0x87, 0x9d, 0x7b, 0x35, 0xd4, 0x9e, 0xb2, 0xe6, 0x2b,
      0x08, 0x71, 0xcd, 0xac, 0x63, 0x89, 0x39, 0xe2, 0x5e, 0x8a, 0x1e, 0x0e,
      0xf9, 0xd5, 0x28, 0x0f, 0xa8, 0xca, 0x32, 0x8b, 0x35, 0x1c, 0x3c, 0x76,
      0x59, 0x89, 0xcb, 0xcf, 0x3d, 0xaa, 0x8b, 0x6c, 0xcc, 0x3a, 0xaf, 0x9f,
      0x39, 0x79, 0xc9, 0x2b, 0x37, 0x20, 0xfc, 0x88, 0xdc, 0x95, 0xed, 0x84,
      0xa1, 0xbe, 0x05, 0x9c, 0x64, 0x99, 0xb9, 0xfd, 0xa2, 0x36, 0xe7, 0xe8,
      0x18, 0xb0, 0x4b, 0x0b, 0xc3, 0x9c, 0x1e, 0x87, 0x6b, 0x19, 0x3b, 0xfe,
      0x55, 0x69, 0x75, 0x3f, 0x88, 0x12, 0x8c, 0xc0, 0x8a, 0xaa, 0x9b, 0x63,
      0xd1, 0xa1, 0x6f, 0x80, 0xef, 0x25, 0x54, 0xd7, 0x18, 0x9c, 0x41, 0x1f,
      0x58, 0x69, 0xca, 0x52, 0xc5, 0xb8, 0x3f, 0xa3, 0x6f, 0xf2, 0x16, 0xb9,
      0xc1, 0xd3, 0x00, 0x62, 0xbe, 0xbc, 0xfd, 0x2d, 0xc5, 0xbc, 0xe0, 0x91,
      0x19, 0x34, 0xfd, 0xa7, 0x9a, 0x86, 0xf6, 0xe6, 0x98, 0xce, 0xd7, 0x59,
      0xc3, 0xff, 0x9b, 0x64, 0x77, 0x33, 0x8f, 0x3d, 0xa4, 0xf9, 0xcd, 0x85,
      0x14, 0xea, 0x99, 0x82, 0xcc, 0xaf, 0xb3, 0x41, 0xb2, 0x38, 0x4d, 0xd9,
      0x02, 0xf3, 0xd1, 0xab, 0x7a, 0xc6, 0x1d, 0xd2, 0x9c, 0x6f, 0x21, 0xba,
      0x5b, 0x86, 0x2f, 0x37, 0x30, 0xe3, 0x7c, 0xfd, 0xc4, 0xfd, 0x80, 0x6c,
      0x22, 0xf2, 0x21 }
};

static const size_t test_lengths[2] = { 64U, 375U };

/* Make sure no other definition is already present. */
#        undef ASSERT

#        define ASSERT(cond, args)           \
            do {                             \
                if (!(cond)) {               \
                    if (verbose != 0)        \
                        mbedtls_printf args; \
                                             \
                    return -1;               \
                }                            \
            } while (0)

int mbedtls_chacha20_self_test(int verbose)
{
    unsigned char output[381];
    unsigned i;
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

    for (i = 0U; i < 2U; i++) {
        if (verbose != 0)
            mbedtls_printf("  ChaCha20 test %u ", i);

        ret = mbedtls_chacha20_crypt(test_keys[i], test_nonces[i],
                                     test_counters[i], test_lengths[i],
                                     test_input[i], output);

        ASSERT(0 == ret, ("error code: %i\n", ret));

        ASSERT(0 == memcmp(output, test_output[i], test_lengths[i]),
               ("failed (output)\n"));

        if (verbose != 0)
            mbedtls_printf("passed\n");
    }

    if (verbose != 0)
        mbedtls_printf("\n");

    return 0;
}

#    endif /* MBEDTLS_SELF_TEST */

#endif /* !MBEDTLS_CHACHA20_C */