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260 lines
8.3 KiB
C
260 lines
8.3 KiB
C
/**
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* Cipher API multi-part AEAD demonstration.
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*
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* This program AEAD-encrypts a message, using the algorithm and key size
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* specified on the command line, using the multi-part API.
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*
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* It comes with a companion program psa/aead_demo.c, which does the same
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* operations with the PSA Crypto API. The goal is that comparing the two
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* programs will help people migrating to the PSA Crypto API.
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*
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* When used with multi-part AEAD operations, the `mbedtls_cipher_context`
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* serves a triple purpose (1) hold the key, (2) store the algorithm when no
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* operation is active, and (3) save progress information for the current
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* operation. With PSA those roles are held by disinct objects: (1) a
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* psa_key_id_t to hold the key, a (2) psa_algorithm_t to represent the
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* algorithm, and (3) a psa_operation_t for multi-part progress.
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*
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* On the other hand, with PSA, the algorithms encodes the desired tag length;
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* with Cipher the desired tag length needs to be tracked separately.
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*
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* This program and its companion psa/aead_demo.c illustrate this by doing the
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* same sequence of multi-part AEAD computation with both APIs; looking at the
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* two side by side should make the differences and similarities clear.
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*/
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/*
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* Copyright The Mbed TLS Contributors
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* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
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*/
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/* First include Mbed TLS headers to get the Mbed TLS configuration and
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* platform definitions that we'll use in this program. Also include
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* standard C headers for functions we'll use here. */
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#include "mbedtls/build_info.h"
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#include "mbedtls/cipher.h"
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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/* If the build options we need are not enabled, compile a placeholder. */
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#if !defined(MBEDTLS_CIPHER_C) || \
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!defined(MBEDTLS_AES_C) || !defined(MBEDTLS_GCM_C) || \
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!defined(MBEDTLS_CHACHAPOLY_C)
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int main(void)
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{
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printf("MBEDTLS_MD_C and/or "
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"MBEDTLS_AES_C and/or MBEDTLS_GCM_C and/or "
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"MBEDTLS_CHACHAPOLY_C not defined\r\n");
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return 0;
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}
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#else
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/* The real program starts here. */
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const char usage[] =
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"Usage: cipher_aead_demo [aes128-gcm|aes256-gcm|aes128-gcm_8|chachapoly]";
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/* Dummy data for encryption: IV/nonce, additional data, 2-part message */
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const unsigned char iv1[12] = { 0x00 };
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const unsigned char add_data1[] = { 0x01, 0x02 };
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const unsigned char msg1_part1[] = { 0x03, 0x04 };
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const unsigned char msg1_part2[] = { 0x05, 0x06, 0x07 };
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/* Dummy data (2nd message) */
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const unsigned char iv2[12] = { 0x10 };
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const unsigned char add_data2[] = { 0x11, 0x12 };
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const unsigned char msg2_part1[] = { 0x13, 0x14 };
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const unsigned char msg2_part2[] = { 0x15, 0x16, 0x17 };
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/* Maximum total size of the messages */
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#define MSG1_SIZE (sizeof(msg1_part1) + sizeof(msg1_part2))
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#define MSG2_SIZE (sizeof(msg2_part1) + sizeof(msg2_part2))
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#define MSG_MAX_SIZE (MSG1_SIZE > MSG2_SIZE ? MSG1_SIZE : MSG2_SIZE)
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/* Dummy key material - never do this in production!
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* 32-byte is enough to all the key size supported by this program. */
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const unsigned char key_bytes[32] = { 0x2a };
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/* Print the contents of a buffer in hex */
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void print_buf(const char *title, unsigned char *buf, size_t len)
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{
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printf("%s:", title);
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for (size_t i = 0; i < len; i++) {
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printf(" %02x", buf[i]);
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}
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printf("\n");
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}
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/* Run an Mbed TLS function and bail out if it fails.
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* A string description of the error code can be recovered with:
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* programs/util/strerror <value> */
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#define CHK(expr) \
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do \
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{ \
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ret = (expr); \
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if (ret != 0) \
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{ \
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printf("Error %d at line %d: %s\n", \
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ret, \
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__LINE__, \
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#expr); \
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goto exit; \
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} \
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} while (0)
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/*
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* Prepare encryption material:
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* - interpret command-line argument
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* - set up key
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* - outputs: context and tag length, which together hold all the information
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*/
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static int aead_prepare(const char *info,
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mbedtls_cipher_context_t *ctx,
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size_t *tag_len)
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{
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int ret;
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/* Convert arg to type + tag_len */
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mbedtls_cipher_type_t type;
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if (strcmp(info, "aes128-gcm") == 0) {
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type = MBEDTLS_CIPHER_AES_128_GCM;
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*tag_len = 16;
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} else if (strcmp(info, "aes256-gcm") == 0) {
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type = MBEDTLS_CIPHER_AES_256_GCM;
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*tag_len = 16;
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} else if (strcmp(info, "aes128-gcm_8") == 0) {
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type = MBEDTLS_CIPHER_AES_128_GCM;
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*tag_len = 8;
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} else if (strcmp(info, "chachapoly") == 0) {
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type = MBEDTLS_CIPHER_CHACHA20_POLY1305;
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*tag_len = 16;
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} else {
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puts(usage);
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return MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA;
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}
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/* Prepare context for the given type */
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CHK(mbedtls_cipher_setup(ctx,
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mbedtls_cipher_info_from_type(type)));
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/* Import key */
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int key_len = mbedtls_cipher_get_key_bitlen(ctx);
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CHK(mbedtls_cipher_setkey(ctx, key_bytes, key_len, MBEDTLS_ENCRYPT));
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exit:
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return ret;
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}
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/*
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* Print out some information.
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*
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* All of this information was present in the command line argument, but his
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* function demonstrates how each piece can be recovered from (ctx, tag_len).
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*/
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static void aead_info(const mbedtls_cipher_context_t *ctx, size_t tag_len)
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{
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mbedtls_cipher_type_t type = mbedtls_cipher_get_type(ctx);
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const mbedtls_cipher_info_t *info = mbedtls_cipher_info_from_type(type);
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const char *ciph = mbedtls_cipher_info_get_name(info);
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int key_bits = mbedtls_cipher_get_key_bitlen(ctx);
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mbedtls_cipher_mode_t mode = mbedtls_cipher_get_cipher_mode(ctx);
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const char *mode_str = mode == MBEDTLS_MODE_GCM ? "GCM"
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: mode == MBEDTLS_MODE_CHACHAPOLY ? "ChachaPoly"
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: "???";
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printf("%s, %d, %s, %u\n",
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ciph, key_bits, mode_str, (unsigned) tag_len);
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}
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/*
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* Encrypt a 2-part message.
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*/
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static int aead_encrypt(mbedtls_cipher_context_t *ctx, size_t tag_len,
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const unsigned char *iv, size_t iv_len,
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const unsigned char *ad, size_t ad_len,
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const unsigned char *part1, size_t part1_len,
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const unsigned char *part2, size_t part2_len)
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{
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int ret;
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size_t olen;
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#define MAX_TAG_LENGTH 16
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unsigned char out[MSG_MAX_SIZE + MAX_TAG_LENGTH];
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unsigned char *p = out;
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CHK(mbedtls_cipher_set_iv(ctx, iv, iv_len));
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CHK(mbedtls_cipher_reset(ctx));
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CHK(mbedtls_cipher_update_ad(ctx, ad, ad_len));
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CHK(mbedtls_cipher_update(ctx, part1, part1_len, p, &olen));
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p += olen;
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CHK(mbedtls_cipher_update(ctx, part2, part2_len, p, &olen));
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p += olen;
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CHK(mbedtls_cipher_finish(ctx, p, &olen));
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p += olen;
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CHK(mbedtls_cipher_write_tag(ctx, p, tag_len));
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p += tag_len;
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olen = p - out;
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print_buf("out", out, olen);
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exit:
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return ret;
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}
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/*
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* AEAD demo: set up key/alg, print out info, encrypt messages.
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*/
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static int aead_demo(const char *info)
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{
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int ret = 0;
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mbedtls_cipher_context_t ctx;
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size_t tag_len;
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mbedtls_cipher_init(&ctx);
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CHK(aead_prepare(info, &ctx, &tag_len));
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aead_info(&ctx, tag_len);
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CHK(aead_encrypt(&ctx, tag_len,
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iv1, sizeof(iv1), add_data1, sizeof(add_data1),
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msg1_part1, sizeof(msg1_part1),
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msg1_part2, sizeof(msg1_part2)));
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CHK(aead_encrypt(&ctx, tag_len,
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iv2, sizeof(iv2), add_data2, sizeof(add_data2),
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msg2_part1, sizeof(msg2_part1),
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msg2_part2, sizeof(msg2_part2)));
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exit:
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mbedtls_cipher_free(&ctx);
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return ret;
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}
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/*
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* Main function
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*/
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int main(int argc, char **argv)
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{
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/* Check usage */
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if (argc != 2) {
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puts(usage);
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return 1;
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}
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int ret;
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/* Run the demo */
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CHK(aead_demo(argv[1]));
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exit:
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return ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
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}
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#endif
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