mirror of
https://github.com/trezor/trezor-firmware.git
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331 lines
10 KiB
C
331 lines
10 KiB
C
/**
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* Copyright (c) 2023 Andrew Kozlik
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included
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* in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
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* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES
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* OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
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* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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* OTHER DEALINGS IN THE SOFTWARE.
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*/
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/*
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* For a specification of AES-CCM see one of the following:
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* https://datatracker.ietf.org/doc/html/rfc3610
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* https://doi.org/10.6028/NIST.SP.800-38C
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*/
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#include <string.h>
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#include "aesccm.h"
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#include "memzero.h"
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typedef struct {
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const aes_encrypt_ctx *encrypt_ctx;
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union {
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// Ensure 32-bit alignment.
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uint8_t state[AES_BLOCK_SIZE];
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uint32_t state32[AES_BLOCK_SIZE / 4];
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};
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// Next position in the state where data will be added.
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// Valid values are 0 to 15.
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uint8_t pos;
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} cbc_mac_context;
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// WARNING: Caller must ensure that encrypt_ctx remains valid for the lifetime
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// of ctx.
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static void cbc_mac_init(cbc_mac_context *ctx,
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const aes_encrypt_ctx *encrypt_ctx) {
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memzero(ctx, sizeof(cbc_mac_context));
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ctx->encrypt_ctx = encrypt_ctx;
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}
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static AES_RETURN cbc_mac_update(cbc_mac_context *ctx, const uint8_t *data,
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size_t size) {
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if (ctx->pos != 0) {
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while (size > 0 && ctx->pos < AES_BLOCK_SIZE) {
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ctx->state[ctx->pos] ^= *data;
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ctx->pos++;
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data++;
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size--;
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}
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if (ctx->pos != AES_BLOCK_SIZE) {
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return EXIT_SUCCESS;
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}
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if (aes_encrypt(ctx->state, ctx->state, ctx->encrypt_ctx) != EXIT_SUCCESS) {
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memzero(ctx, sizeof(*ctx));
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return EXIT_FAILURE;
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}
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ctx->pos = 0;
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}
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size_t block_count = size >> AES_BLOCK_SIZE_P2;
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size %= AES_BLOCK_SIZE;
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if (!ALIGN_OFFSET(data, 4)) {
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while (block_count != 0) {
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ctx->state32[0] ^= ((uint32_t *)data)[0];
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ctx->state32[1] ^= ((uint32_t *)data)[1];
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ctx->state32[2] ^= ((uint32_t *)data)[2];
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ctx->state32[3] ^= ((uint32_t *)data)[3];
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if (aes_encrypt(ctx->state, ctx->state, ctx->encrypt_ctx) !=
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EXIT_SUCCESS) {
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memzero(ctx, sizeof(*ctx));
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return EXIT_FAILURE;
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}
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data += AES_BLOCK_SIZE;
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block_count--;
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}
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} else {
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while (block_count != 0) {
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ctx->state[0] ^= data[0];
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ctx->state[1] ^= data[1];
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ctx->state[2] ^= data[2];
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ctx->state[3] ^= data[3];
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ctx->state[4] ^= data[4];
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ctx->state[5] ^= data[5];
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ctx->state[6] ^= data[6];
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ctx->state[7] ^= data[7];
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ctx->state[8] ^= data[8];
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ctx->state[9] ^= data[9];
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ctx->state[10] ^= data[10];
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ctx->state[11] ^= data[11];
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ctx->state[12] ^= data[12];
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ctx->state[13] ^= data[13];
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ctx->state[14] ^= data[14];
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ctx->state[15] ^= data[15];
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if (aes_encrypt(ctx->state, ctx->state, ctx->encrypt_ctx) !=
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EXIT_SUCCESS) {
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memzero(ctx, sizeof(*ctx));
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return EXIT_FAILURE;
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}
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data += AES_BLOCK_SIZE;
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block_count--;
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}
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}
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while (size > 0) {
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ctx->state[ctx->pos] ^= *data;
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ctx->pos++;
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data++;
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size--;
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}
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return EXIT_SUCCESS;
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}
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static AES_RETURN cbc_mac_update_zero_padding(cbc_mac_context *ctx) {
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if (ctx->pos != 0) {
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if (aes_encrypt(ctx->state, ctx->state, ctx->encrypt_ctx) != EXIT_SUCCESS) {
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memzero(ctx, sizeof(*ctx));
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return EXIT_FAILURE;
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}
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ctx->pos = 0;
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}
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return EXIT_SUCCESS;
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}
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static AES_RETURN cbc_mac_final(cbc_mac_context *ctx, uint8_t *mac,
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size_t mac_len) {
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if (ctx->pos != 0 || mac_len > AES_BLOCK_SIZE) {
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memzero(ctx, sizeof(*ctx));
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return EXIT_FAILURE;
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}
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memcpy(mac, ctx->state, mac_len);
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memzero(ctx, sizeof(*ctx));
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return EXIT_SUCCESS;
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}
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static AES_RETURN aes_ccm_init(aes_encrypt_ctx *encrypt_ctx,
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const uint8_t *nonce, size_t nonce_len,
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const uint8_t *adata, size_t adata_len,
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size_t plaintext_len, size_t mac_len,
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cbc_mac_context *cbc_ctx, uint8_t *ctr_block) {
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if (mac_len < 4 || mac_len > AES_BLOCK_SIZE || mac_len % 2 != 0) {
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return EXIT_FAILURE;
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}
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if (nonce_len < 7 || nonce_len > 13) {
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return EXIT_FAILURE;
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}
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// Length of the binary representation of plaintext_len.
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const size_t q = 15 - nonce_len;
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uint8_t flags = (adata_len != 0) << 6;
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flags |= ((mac_len - 2) / 2) << 3;
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flags |= q - 1;
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// Encode the first block.
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uint8_t block[AES_BLOCK_SIZE] = {0};
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block[0] = flags;
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memcpy(&block[1], nonce, nonce_len);
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size_t shifted_len = plaintext_len;
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for (size_t i = 0; i < q; ++i) {
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block[15 - i] = shifted_len & 0xff;
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shifted_len >>= 8;
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}
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if (shifted_len != 0) {
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// plaintext_len does not fit into q octets.
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return EXIT_FAILURE;
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}
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aes_mode_reset(encrypt_ctx);
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cbc_mac_init(cbc_ctx, encrypt_ctx);
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if (cbc_mac_update(cbc_ctx, block, sizeof(block)) != EXIT_SUCCESS) {
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return EXIT_FAILURE;
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}
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// Format the associated data length.
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if (adata_len != 0) {
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size_t block_size = 0;
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if (adata_len < 65536 - 256) {
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block[0] = adata_len >> 8;
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block[1] = adata_len & 0xff;
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block_size = 2;
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} else {
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shifted_len = adata_len;
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block[5] = shifted_len & 0xff;
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shifted_len >>= 8;
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block[4] = shifted_len & 0xff;
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shifted_len >>= 8;
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block[3] = shifted_len & 0xff;
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shifted_len >>= 8;
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block[2] = shifted_len & 0xff;
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block[1] = 0xfe;
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block[0] = 0xff;
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block_size = 6;
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if ((shifted_len >> 8) != 0) {
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// Associated data over 4 GB not supported.
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return EXIT_FAILURE;
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}
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}
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if (cbc_mac_update(cbc_ctx, block, block_size) != EXIT_SUCCESS ||
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cbc_mac_update(cbc_ctx, adata, adata_len) != EXIT_SUCCESS ||
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cbc_mac_update_zero_padding(cbc_ctx) != EXIT_SUCCESS) {
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return EXIT_FAILURE;
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}
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}
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// Initialize counter.
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memzero(ctr_block, AES_BLOCK_SIZE);
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ctr_block[0] = q - 1;
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memcpy(&ctr_block[1], nonce, nonce_len);
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return EXIT_SUCCESS;
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}
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// The length of data written to the ciphertext array is plaintext_len +
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// mac_len.
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AES_RETURN aes_ccm_encrypt(aes_encrypt_ctx *encrypt_ctx, const uint8_t *nonce,
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size_t nonce_len, const uint8_t *adata,
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size_t adata_len, const uint8_t *plaintext,
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size_t plaintext_len, size_t mac_len,
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uint8_t *ciphertext) {
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cbc_mac_context cbc_ctx = {0};
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uint8_t ctr_block[AES_BLOCK_SIZE] = {0};
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if (aes_ccm_init(encrypt_ctx, nonce, nonce_len, adata, adata_len,
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plaintext_len, mac_len, &cbc_ctx,
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ctr_block) != EXIT_SUCCESS) {
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return EXIT_FAILURE;
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}
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if (cbc_mac_update(&cbc_ctx, plaintext, plaintext_len) != EXIT_SUCCESS ||
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cbc_mac_update_zero_padding(&cbc_ctx) != EXIT_SUCCESS ||
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cbc_mac_final(&cbc_ctx, &ciphertext[plaintext_len], mac_len) !=
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EXIT_SUCCESS) {
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return EXIT_FAILURE;
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}
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uint8_t s0[AES_BLOCK_SIZE] = {0};
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if (aes_ecb_encrypt(ctr_block, s0, AES_BLOCK_SIZE, encrypt_ctx) !=
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EXIT_SUCCESS) {
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memzero(s0, sizeof(s0));
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return EXIT_FAILURE;
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}
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for (size_t i = 0; i < mac_len; ++i) {
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ciphertext[plaintext_len + i] ^= s0[i];
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}
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memzero(s0, sizeof(s0));
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ctr_block[AES_BLOCK_SIZE - 1] = 1;
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if (aes_ctr_crypt(plaintext, ciphertext, plaintext_len, ctr_block,
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aes_ctr_cbuf_inc, encrypt_ctx) != EXIT_SUCCESS) {
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memzero(ciphertext, plaintext_len + mac_len);
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return EXIT_FAILURE;
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}
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return EXIT_SUCCESS;
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}
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// The length of data written to the plaintext array is ciphertext_len -
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// mac_len.
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AES_RETURN aes_ccm_decrypt(aes_encrypt_ctx *encrypt_ctx, const uint8_t *nonce,
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size_t nonce_len, const uint8_t *adata,
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size_t adata_len, const uint8_t *ciphertext,
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size_t ciphertext_len, size_t mac_len,
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uint8_t *plaintext) {
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cbc_mac_context cbc_ctx = {0};
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uint8_t ctr_block[AES_BLOCK_SIZE] = {0};
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size_t plaintext_len = ciphertext_len - mac_len;
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if (ciphertext_len < mac_len ||
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aes_ccm_init(encrypt_ctx, nonce, nonce_len, adata, adata_len,
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plaintext_len, mac_len, &cbc_ctx,
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ctr_block) != EXIT_SUCCESS) {
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return EXIT_FAILURE;
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}
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uint8_t s0[AES_BLOCK_SIZE] = {0};
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if (aes_ecb_encrypt(ctr_block, s0, AES_BLOCK_SIZE, encrypt_ctx) !=
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EXIT_SUCCESS) {
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memzero(&cbc_ctx, sizeof(cbc_ctx));
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return EXIT_FAILURE;
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}
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ctr_block[AES_BLOCK_SIZE - 1] = 1;
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if (aes_ctr_crypt(ciphertext, plaintext, plaintext_len, ctr_block,
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aes_ctr_cbuf_inc, encrypt_ctx) != EXIT_SUCCESS) {
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memzero(&cbc_ctx, sizeof(cbc_ctx));
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memzero(s0, sizeof(s0));
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memzero(plaintext, plaintext_len);
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return EXIT_FAILURE;
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}
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uint8_t cbc_mac[AES_BLOCK_SIZE] = {0};
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if (cbc_mac_update(&cbc_ctx, plaintext, plaintext_len) != EXIT_SUCCESS ||
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cbc_mac_update_zero_padding(&cbc_ctx) != EXIT_SUCCESS ||
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cbc_mac_final(&cbc_ctx, cbc_mac, mac_len) != EXIT_SUCCESS) {
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memzero(s0, sizeof(s0));
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memzero(plaintext, plaintext_len);
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return EXIT_FAILURE;
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}
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uint8_t diff = 0;
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for (size_t i = 0; i < mac_len; ++i) {
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diff |= ciphertext[plaintext_len + i] ^ s0[i] ^ cbc_mac[i];
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}
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memzero(cbc_mac, sizeof(cbc_mac));
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memzero(s0, sizeof(s0));
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if (diff != 0) {
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memzero(plaintext, plaintext_len);
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return EXIT_FAILURE;
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}
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return EXIT_SUCCESS;
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}
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