/*

 *  Entropy accumulator implementation

 *

 *  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_ENTROPY_C)

#include "mbedtls/entropy.h"

#include "entropy_poll.h"

#include "mbedtls/platform_util.h"

#include "mbedtls/error.h"

#include <string.h>

#if defined(MBEDTLS_FS_IO)

#include <stdio.h>

#endif

#include "mbedtls/platform.h"

#include "mbedtls/platform.h"

#define ENTROPY_MAX_LOOP    256     /**< Maximum amount to loop before error */

void mbedtls_entropy_init(mbedtls_entropy_context *ctx)

{

    ctx->source_count = 0;

    memset(ctx->source, 0, sizeof(ctx->source));

#if defined(MBEDTLS_THREADING_C)

    mbedtls_mutex_init(&ctx->mutex);

#endif

    ctx->accumulator_started = 0;

#if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)

    mbedtls_sha512_init(&ctx->accumulator);

#else

    mbedtls_sha256_init(&ctx->accumulator);

#endif

    /* Reminder: Update ENTROPY_HAVE_STRONG in the test files

     *           when adding more strong entropy sources here. */

#if !defined(MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES)

#if !defined(MBEDTLS_NO_PLATFORM_ENTROPY)

    mbedtls_entropy_add_source(ctx, mbedtls_platform_entropy_poll, NULL,

                               MBEDTLS_ENTROPY_MIN_PLATFORM,

                               MBEDTLS_ENTROPY_SOURCE_STRONG);

#endif

#if defined(MBEDTLS_ENTROPY_HARDWARE_ALT)

    mbedtls_entropy_add_source(ctx, mbedtls_hardware_poll, NULL,

                               MBEDTLS_ENTROPY_MIN_HARDWARE,

                               MBEDTLS_ENTROPY_SOURCE_STRONG);

#endif

#if defined(MBEDTLS_ENTROPY_NV_SEED)

    mbedtls_entropy_add_source(ctx, mbedtls_nv_seed_poll, NULL,

                               MBEDTLS_ENTROPY_BLOCK_SIZE,

                               MBEDTLS_ENTROPY_SOURCE_STRONG);

    ctx->initial_entropy_run = 0;

#endif

#endif /* MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES */

}

void mbedtls_entropy_free(mbedtls_entropy_context *ctx)

{

    /* If the context was already free, don't call free() again.

     * This is important for mutexes which don't allow double-free. */

    if (ctx->accumulator_started == -1) {

        return;

    }

#if defined(MBEDTLS_THREADING_C)

    mbedtls_mutex_free(&ctx->mutex);

#endif

#if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)

    mbedtls_sha512_free(&ctx->accumulator);

#else

    mbedtls_sha256_free(&ctx->accumulator);

#endif

#if defined(MBEDTLS_ENTROPY_NV_SEED)

    ctx->initial_entropy_run = 0;

#endif

    ctx->source_count = 0;

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

    ctx->accumulator_started = -1;

}

int mbedtls_entropy_add_source(mbedtls_entropy_context *ctx,

                               mbedtls_entropy_f_source_ptr f_source, void *p_source,

                               size_t threshold, int strong)

{

    int idx, ret = 0;

#if defined(MBEDTLS_THREADING_C)

    if ((ret = mbedtls_mutex_lock(&ctx->mutex)) != 0) {

        return ret;

    }

#endif

    idx = ctx->source_count;

    if (idx >= MBEDTLS_ENTROPY_MAX_SOURCES) {

        ret = MBEDTLS_ERR_ENTROPY_MAX_SOURCES;

        goto exit;

    }

    ctx->source[idx].f_source  = f_source;

    ctx->source[idx].p_source  = p_source;

    ctx->source[idx].threshold = threshold;

    ctx->source[idx].strong    = strong;

    ctx->source_count++;

exit:

#if defined(MBEDTLS_THREADING_C)

    if (mbedtls_mutex_unlock(&ctx->mutex) != 0) {

        return MBEDTLS_ERR_THREADING_MUTEX_ERROR;

    }

#endif

    return ret;

}

/*

 * Entropy accumulator update

 */

static int entropy_update(mbedtls_entropy_context *ctx, unsigned char source_id,

                          const unsigned char *data, size_t len)

{

    unsigned char header[2];

    unsigned char tmp[MBEDTLS_ENTROPY_BLOCK_SIZE];

    size_t use_len = len;

    const unsigned char *p = data;

    int ret = 0;

    if (use_len > MBEDTLS_ENTROPY_BLOCK_SIZE) {

#if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)

        if ((ret = mbedtls_sha512(data, len, tmp, 0)) != 0) {

            goto cleanup;

        }

#else

        if ((ret = mbedtls_sha256(data, len, tmp, 0)) != 0) {

            goto cleanup;

        }

#endif

        p = tmp;

        use_len = MBEDTLS_ENTROPY_BLOCK_SIZE;

    }

    header[0] = source_id;

    header[1] = use_len & 0xFF;

    /*

     * Start the accumulator if this has not already happened. Note that

     * it is sufficient to start the accumulator here only because all calls to

     * gather entropy eventually execute this code.

     */

#if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)

    if (ctx->accumulator_started == 0 &&

        (ret = mbedtls_sha512_starts(&ctx->accumulator, 0)) != 0) {

        goto cleanup;

    } else {

        ctx->accumulator_started = 1;

    }

    if ((ret = mbedtls_sha512_update(&ctx->accumulator, header, 2)) != 0) {

        goto cleanup;

    }

    ret = mbedtls_sha512_update(&ctx->accumulator, p, use_len);

#else

    if (ctx->accumulator_started == 0 &&

        (ret = mbedtls_sha256_starts(&ctx->accumulator, 0)) != 0) {

        goto cleanup;

    } else {

        ctx->accumulator_started = 1;

    }

    if ((ret = mbedtls_sha256_update(&ctx->accumulator, header, 2)) != 0) {

        goto cleanup;

    }

    ret = mbedtls_sha256_update(&ctx->accumulator, p, use_len);

#endif

cleanup:

    mbedtls_platform_zeroize(tmp, sizeof(tmp));

    return ret;

}

int mbedtls_entropy_update_manual(mbedtls_entropy_context *ctx,

                                  const unsigned char *data, size_t len)

{

    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

#if defined(MBEDTLS_THREADING_C)

    if ((ret = mbedtls_mutex_lock(&ctx->mutex)) != 0) {

        return ret;

    }

#endif

    ret = entropy_update(ctx, MBEDTLS_ENTROPY_SOURCE_MANUAL, data, len);

#if defined(MBEDTLS_THREADING_C)

    if (mbedtls_mutex_unlock(&ctx->mutex) != 0) {

        return MBEDTLS_ERR_THREADING_MUTEX_ERROR;

    }

#endif

    return ret;

}

/*

 * Run through the different sources to add entropy to our accumulator

 */

static int entropy_gather_internal(mbedtls_entropy_context *ctx)

{

    int ret = MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;

    int i;

    int have_one_strong = 0;

    unsigned char buf[MBEDTLS_ENTROPY_MAX_GATHER];

    size_t olen;

    if (ctx->source_count == 0) {

        return MBEDTLS_ERR_ENTROPY_NO_SOURCES_DEFINED;

    }

    /*

     * Run through our entropy sources

     */

    for (i = 0; i < ctx->source_count; i++) {

        if (ctx->source[i].strong == MBEDTLS_ENTROPY_SOURCE_STRONG) {

            have_one_strong = 1;

        }

        olen = 0;

        if ((ret = ctx->source[i].f_source(ctx->source[i].p_source,

                                           buf, MBEDTLS_ENTROPY_MAX_GATHER, &olen)) != 0) {

            goto cleanup;

        }

        /*

         * Add if we actually gathered something

         */

        if (olen > 0) {

            if ((ret = entropy_update(ctx, (unsigned char) i,

                                      buf, olen)) != 0) {

                return ret;

            }

            ctx->source[i].size += olen;

        }

    }

    if (have_one_strong == 0) {

        ret = MBEDTLS_ERR_ENTROPY_NO_STRONG_SOURCE;

    }

cleanup:

    mbedtls_platform_zeroize(buf, sizeof(buf));

    return ret;

}

/*

 * Thread-safe wrapper for entropy_gather_internal()

 */

int mbedtls_entropy_gather(mbedtls_entropy_context *ctx)

{

    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

#if defined(MBEDTLS_THREADING_C)

    if ((ret = mbedtls_mutex_lock(&ctx->mutex)) != 0) {

        return ret;

    }

#endif

    ret = entropy_gather_internal(ctx);

#if defined(MBEDTLS_THREADING_C)

    if (mbedtls_mutex_unlock(&ctx->mutex) != 0) {

        return MBEDTLS_ERR_THREADING_MUTEX_ERROR;

    }

#endif

    return ret;

}

int mbedtls_entropy_func(void *data, unsigned char *output, size_t len)

{

    int ret, count = 0, i, thresholds_reached;

    size_t strong_size;

    mbedtls_entropy_context *ctx = (mbedtls_entropy_context *) data;

    unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];

    if (len > MBEDTLS_ENTROPY_BLOCK_SIZE) {

        return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;

    }

#if defined(MBEDTLS_ENTROPY_NV_SEED)

    /* Update the NV entropy seed before generating any entropy for outside

     * use.

     */

    if (ctx->initial_entropy_run == 0) {

        ctx->initial_entropy_run = 1;

        if ((ret = mbedtls_entropy_update_nv_seed(ctx)) != 0) {

            return ret;

        }

    }

#endif

#if defined(MBEDTLS_THREADING_C)

    if ((ret = mbedtls_mutex_lock(&ctx->mutex)) != 0) {

        return ret;

    }

#endif

    /*

     * Always gather extra entropy before a call

     */

    do {

        if (count++ > ENTROPY_MAX_LOOP) {

            ret = MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;

            goto exit;

        }

        if ((ret = entropy_gather_internal(ctx)) != 0) {

            goto exit;

        }

        thresholds_reached = 1;

        strong_size = 0;

        for (i = 0; i < ctx->source_count; i++) {

            if (ctx->source[i].size < ctx->source[i].threshold) {

                thresholds_reached = 0;

            }

            if (ctx->source[i].strong == MBEDTLS_ENTROPY_SOURCE_STRONG) {

                strong_size += ctx->source[i].size;

            }

        }

    } while (!thresholds_reached || strong_size < MBEDTLS_ENTROPY_BLOCK_SIZE);

    memset(buf, 0, MBEDTLS_ENTROPY_BLOCK_SIZE);

#if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)

    /*

     * Note that at this stage it is assumed that the accumulator was started

     * in a previous call to entropy_update(). If this is not guaranteed, the

     * code below will fail.

     */

    if ((ret = mbedtls_sha512_finish(&ctx->accumulator, buf)) != 0) {

        goto exit;

    }

    /*

     * Reset accumulator and counters and recycle existing entropy

     */

    mbedtls_sha512_free(&ctx->accumulator);

    mbedtls_sha512_init(&ctx->accumulator);

    if ((ret = mbedtls_sha512_starts(&ctx->accumulator, 0)) != 0) {

        goto exit;

    }

    if ((ret = mbedtls_sha512_update(&ctx->accumulator, buf,

                                     MBEDTLS_ENTROPY_BLOCK_SIZE)) != 0) {

        goto exit;

    }

    /*

     * Perform second SHA-512 on entropy

     */

    if ((ret = mbedtls_sha512(buf, MBEDTLS_ENTROPY_BLOCK_SIZE,

                              buf, 0)) != 0) {

        goto exit;

    }

#else /* MBEDTLS_ENTROPY_SHA512_ACCUMULATOR */

    if ((ret = mbedtls_sha256_finish(&ctx->accumulator, buf)) != 0) {

        goto exit;

    }

    /*

     * Reset accumulator and counters and recycle existing entropy

     */

    mbedtls_sha256_free(&ctx->accumulator);

    mbedtls_sha256_init(&ctx->accumulator);

    if ((ret = mbedtls_sha256_starts(&ctx->accumulator, 0)) != 0) {

        goto exit;

    }

    if ((ret = mbedtls_sha256_update(&ctx->accumulator, buf,

                                     MBEDTLS_ENTROPY_BLOCK_SIZE)) != 0) {

        goto exit;

    }

    /*

     * Perform second SHA-256 on entropy

     */

    if ((ret = mbedtls_sha256(buf, MBEDTLS_ENTROPY_BLOCK_SIZE,

                              buf, 0)) != 0) {

        goto exit;

    }

#endif /* MBEDTLS_ENTROPY_SHA512_ACCUMULATOR */

    for (i = 0; i < ctx->source_count; i++) {

        ctx->source[i].size = 0;

    }

    memcpy(output, buf, len);

    ret = 0;

exit:

    mbedtls_platform_zeroize(buf, sizeof(buf));

#if defined(MBEDTLS_THREADING_C)

    if (mbedtls_mutex_unlock(&ctx->mutex) != 0) {

        return MBEDTLS_ERR_THREADING_MUTEX_ERROR;

    }

#endif

    return ret;

}

#if defined(MBEDTLS_ENTROPY_NV_SEED)

int mbedtls_entropy_update_nv_seed(mbedtls_entropy_context *ctx)

{

    int ret = MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR;

    unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];

    /* Read new seed  and write it to NV */

    if ((ret = mbedtls_entropy_func(ctx, buf, MBEDTLS_ENTROPY_BLOCK_SIZE)) != 0) {

        return ret;

    }

    if (mbedtls_nv_seed_write(buf, MBEDTLS_ENTROPY_BLOCK_SIZE) < 0) {

        return MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR;

    }

    /* Manually update the remaining stream with a separator value to diverge */

    memset(buf, 0, MBEDTLS_ENTROPY_BLOCK_SIZE);

    ret = mbedtls_entropy_update_manual(ctx, buf, MBEDTLS_ENTROPY_BLOCK_SIZE);

    return ret;

}

#endif /* MBEDTLS_ENTROPY_NV_SEED */

#if defined(MBEDTLS_FS_IO)

int mbedtls_entropy_write_seed_file(mbedtls_entropy_context *ctx, const char *path)

{

    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

    FILE *f = NULL;

    unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];

    if ((ret = mbedtls_entropy_func(ctx, buf, MBEDTLS_ENTROPY_BLOCK_SIZE)) != 0) {

        ret = MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;

        goto exit;

    }

    if ((f = fopen(path, "wb")) == NULL) {

        ret = MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR;

        goto exit;

    }

    /* Ensure no stdio buffering of secrets, as such buffers cannot be wiped. */

    mbedtls_setbuf(f, NULL);

    if (fwrite(buf, 1, MBEDTLS_ENTROPY_BLOCK_SIZE, f) != MBEDTLS_ENTROPY_BLOCK_SIZE) {

        ret = MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR;

        goto exit;

    }

    ret = 0;

exit:

    mbedtls_platform_zeroize(buf, sizeof(buf));

    if (f != NULL) {

        fclose(f);

    }

    return ret;

}

int mbedtls_entropy_update_seed_file(mbedtls_entropy_context *ctx, const char *path)

{

    int ret = 0;

    FILE *f;

    size_t n;

    unsigned char buf[MBEDTLS_ENTROPY_MAX_SEED_SIZE];

    if ((f = fopen(path, "rb")) == NULL) {

        return MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR;

    }

    /* Ensure no stdio buffering of secrets, as such buffers cannot be wiped. */

    mbedtls_setbuf(f, NULL);

    fseek(f, 0, SEEK_END);

    n = (size_t) ftell(f);

    fseek(f, 0, SEEK_SET);

    if (n > MBEDTLS_ENTROPY_MAX_SEED_SIZE) {

        n = MBEDTLS_ENTROPY_MAX_SEED_SIZE;

    }

    if (fread(buf, 1, n, f) != n) {

        ret = MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR;

    } else {

        ret = mbedtls_entropy_update_manual(ctx, buf, n);

    }

    fclose(f);

    mbedtls_platform_zeroize(buf, sizeof(buf));

    if (ret != 0) {

        return ret;

    }

    return mbedtls_entropy_write_seed_file(ctx, path);

}

#endif /* MBEDTLS_FS_IO */

#if defined(MBEDTLS_SELF_TEST)

/*

 * Dummy source function

 */

static int entropy_dummy_source(void *data, unsigned char *output,

                                size_t len, size_t *olen)

{

    ((void) data);

    memset(output, 0x2a, len);

    *olen = len;

    return 0;

}

#if defined(MBEDTLS_ENTROPY_HARDWARE_ALT)

static int mbedtls_entropy_source_self_test_gather(unsigned char *buf, size_t buf_len)

{

    int ret = 0;

    size_t entropy_len = 0;

    size_t olen = 0;

    size_t attempts = buf_len;

    while (attempts > 0 && entropy_len < buf_len) {

        if ((ret = mbedtls_hardware_poll(NULL, buf + entropy_len,

                                         buf_len - entropy_len, &olen)) != 0) {

            return ret;

        }

        entropy_len += olen;

        attempts--;

    }

    if (entropy_len < buf_len) {

        ret = 1;

    }

    return ret;

}

static int mbedtls_entropy_source_self_test_check_bits(const unsigned char *buf,

                                                       size_t buf_len)

{

    unsigned char set = 0xFF;

    unsigned char unset = 0x00;

    size_t i;

    for (i = 0; i < buf_len; i++) {

        set &= buf[i];

        unset |= buf[i];

    }

    return set == 0xFF || unset == 0x00;

}

/*

 * A test to ensure that the entropy sources are functioning correctly

 * and there is no obvious failure. The test performs the following checks:

 *  - The entropy source is not providing only 0s (all bits unset) or 1s (all

 *    bits set).

 *  - The entropy source is not providing values in a pattern. Because the

 *    hardware could be providing data in an arbitrary length, this check polls

 *    the hardware entropy source twice and compares the result to ensure they

 *    are not equal.

 *  - The error code returned by the entropy source is not an error.

 */

int mbedtls_entropy_source_self_test(int verbose)

{

    int ret = 0;

    unsigned char buf0[2 * sizeof(unsigned long long int)];

    unsigned char buf1[2 * sizeof(unsigned long long int)];

    if (verbose != 0) {

        mbedtls_printf("  ENTROPY_BIAS test: ");

    }

    memset(buf0, 0x00, sizeof(buf0));

    memset(buf1, 0x00, sizeof(buf1));

    if ((ret = mbedtls_entropy_source_self_test_gather(buf0, sizeof(buf0))) != 0) {

        goto cleanup;

    }

    if ((ret = mbedtls_entropy_source_self_test_gather(buf1, sizeof(buf1))) != 0) {

        goto cleanup;

    }

    /* Make sure that the returned values are not all 0 or 1 */

    if ((ret = mbedtls_entropy_source_self_test_check_bits(buf0, sizeof(buf0))) != 0) {

        goto cleanup;

    }

    if ((ret = mbedtls_entropy_source_self_test_check_bits(buf1, sizeof(buf1))) != 0) {

        goto cleanup;

    }

    /* Make sure that the entropy source is not returning values in a

     * pattern */

    ret = memcmp(buf0, buf1, sizeof(buf0)) == 0;

cleanup:

    if (verbose != 0) {

        if (ret != 0) {

            mbedtls_printf("failed\n");

        } else {

            mbedtls_printf("passed\n");

        }

        mbedtls_printf("\n");

    }

    return ret != 0;

}

#endif /* MBEDTLS_ENTROPY_HARDWARE_ALT */

/*

 * The actual entropy quality is hard to test, but we can at least

 * test that the functions don't cause errors and write the correct

 * amount of data to buffers.

 */

int mbedtls_entropy_self_test(int verbose)

{

    int ret = 1;

    mbedtls_entropy_context ctx;

    unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE] = { 0 };

    unsigned char acc[MBEDTLS_ENTROPY_BLOCK_SIZE] = { 0 };

    size_t i, j;

    if (verbose != 0) {

        mbedtls_printf("  ENTROPY test: ");

    }

    mbedtls_entropy_init(&ctx);

    /* First do a gather to make sure we have default sources */

    if ((ret = mbedtls_entropy_gather(&ctx)) != 0) {

        goto cleanup;

    }

    ret = mbedtls_entropy_add_source(&ctx, entropy_dummy_source, NULL, 16,

                                     MBEDTLS_ENTROPY_SOURCE_WEAK);

    if (ret != 0) {

        goto cleanup;

    }

    if ((ret = mbedtls_entropy_update_manual(&ctx, buf, sizeof buf)) != 0) {

        goto cleanup;

    }

    /*

     * To test that mbedtls_entropy_func writes correct number of bytes:

     * - use the whole buffer and rely on ASan to detect overruns

     * - collect entropy 8 times and OR the result in an accumulator:

     *   any byte should then be 0 with probably 2^(-64), so requiring

     *   each of the 32 or 64 bytes to be non-zero has a false failure rate

     *   of at most 2^(-58) which is acceptable.

     */

    for (i = 0; i < 8; i++) {

        if ((ret = mbedtls_entropy_func(&ctx, buf, sizeof(buf))) != 0) {

            goto cleanup;

        }

        for (j = 0; j < sizeof(buf); j++) {

            acc[j] |= buf[j];

        }

    }

    for (j = 0; j < sizeof(buf); j++) {

        if (acc[j] == 0) {

            ret = 1;

            goto cleanup;

        }

    }

#if defined(MBEDTLS_ENTROPY_HARDWARE_ALT)

    if ((ret = mbedtls_entropy_source_self_test(0)) != 0) {

        goto cleanup;

    }

#endif

cleanup:

    mbedtls_entropy_free(&ctx);

    if (verbose != 0) {

        if (ret != 0) {

            mbedtls_printf("failed\n");

        } else {

            mbedtls_printf("passed\n");

        }

        mbedtls_printf("\n");

    }

    return ret != 0;

}

#endif /* MBEDTLS_SELF_TEST */

#endif /* MBEDTLS_ENTROPY_C */