openssl3.2 - 官方demo学习 - cipher - aesccm.c
概述
aesccm.c 是 AES-192-CCM 的加解密应用例子, 用的EVP接口.
看到不仅仅要用到key, iv, data, 在此之前还要设置 nonce, tag, 认证数据.
为啥需要设置tag和认证数据啊? 普通的对称加解密, 有key, iv, data不就足够了么? 问题先放这里, 看看往后实验是否能有答案?
笔记
/*! \file aesccm.c */
/*
* Copyright 2013-2023 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the Apache License 2.0 (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
/*
* Simple AES CCM authenticated encryption with additional data (AEAD)
* demonstration program.
*/
#include <stdio.h>
#include <openssl/err.h>
#include <openssl/bio.h>
#include <openssl/evp.h>
#include <openssl/core_names.h>
#include "my_openSSL_lib.h"
/* AES-CCM test data obtained from NIST public test vectors */
/* AES key */
static const unsigned char ccm_key[] = {
0xce, 0xb0, 0x09, 0xae, 0xa4, 0x45, 0x44, 0x51, 0xfe, 0xad, 0xf0, 0xe6,
0xb3, 0x6f, 0x45, 0x55, 0x5d, 0xd0, 0x47, 0x23, 0xba, 0xa4, 0x48, 0xe8
};
/* Unique nonce to be used for this message */
static const unsigned char ccm_nonce[] = {
0x76, 0x40, 0x43, 0xc4, 0x94, 0x60, 0xb7
};
/*
* Example of Additional Authenticated Data (AAD), i.e. unencrypted data
* which can be authenticated using the generated Tag value.
*/
static const unsigned char ccm_adata[] = {
0x6e, 0x80, 0xdd, 0x7f, 0x1b, 0xad, 0xf3, 0xa1, 0xc9, 0xab, 0x25, 0xc7,
0x5f, 0x10, 0xbd, 0xe7, 0x8c, 0x23, 0xfa, 0x0e, 0xb8, 0xf9, 0xaa, 0xa5,
0x3a, 0xde, 0xfb, 0xf4, 0xcb, 0xf7, 0x8f, 0xe4
};
/* Example plaintext to encrypt */
static const unsigned char ccm_pt[] = {
0xc8, 0xd2, 0x75, 0xf9, 0x19, 0xe1, 0x7d, 0x7f, 0xe6, 0x9c, 0x2a, 0x1f,
0x58, 0x93, 0x9d, 0xfe, 0x4d, 0x40, 0x37, 0x91, 0xb5, 0xdf, 0x13, 0x10
};
/* Expected ciphertext value */
static const unsigned char ccm_ct[] = {
0x8a, 0x0f, 0x3d, 0x82, 0x29, 0xe4, 0x8e, 0x74, 0x87, 0xfd, 0x95, 0xa2,
0x8a, 0xd3, 0x92, 0xc8, 0x0b, 0x36, 0x81, 0xd4, 0xfb, 0xc7, 0xbb, 0xfd
};
/* Expected AEAD Tag value */
static const unsigned char ccm_tag[] = {
0x2d, 0xd6, 0xef, 0x1c, 0x45, 0xd4, 0xcc, 0xb7, 0x23, 0xdc, 0x07, 0x44,
0x14, 0xdb, 0x50, 0x6d
};
/*
* A library context and property query can be used to select & filter
* algorithm implementations. If they are NULL then the default library
* context and properties are used.
*/
OSSL_LIB_CTX *libctx = NULL;
const char *propq = NULL;
int aes_ccm_encrypt(void)
{
int ret = 0;
EVP_CIPHER_CTX *ctx;
EVP_CIPHER *cipher = NULL;
int outlen, tmplen;
size_t ccm_nonce_len = sizeof(ccm_nonce);
size_t ccm_tag_len = sizeof(ccm_tag);
unsigned char outbuf[1024];
unsigned char outtag[16];
OSSL_PARAM params[3] = {
OSSL_PARAM_END, OSSL_PARAM_END, OSSL_PARAM_END
};
printf("AES CCM Encrypt:\n");
printf("Plaintext:\n");
BIO_dump_fp(stdout, ccm_pt, sizeof(ccm_pt)); /*!< 对给定的buffer[len], 进行16进制的格式打印, 类似于 winhex */
/*!
0000 - c8 d2 75 f9 19 e1 7d 7f-e6 9c 2a 1f 58 93 9d fe ..u...}...*.X...
0010 - 4d 40 37 91 b5 df 13 10- M@7.....
*/
/* Create a context for the encrypt operation */
if ((ctx = EVP_CIPHER_CTX_new()) == NULL)
goto err;
/* Fetch the cipher implementation */
if ((cipher = EVP_CIPHER_fetch(libctx, "AES-192-CCM", propq)) == NULL)
goto err;
/* Set nonce length if default 96 bits is not appropriate */
params[0] = OSSL_PARAM_construct_size_t(OSSL_CIPHER_PARAM_AEAD_IVLEN,
&ccm_nonce_len);
/* Set tag length */
params[1] = OSSL_PARAM_construct_octet_string(OSSL_CIPHER_PARAM_AEAD_TAG,
NULL, ccm_tag_len);
/*
* Initialise encrypt operation with the cipher & mode,
* nonce length and tag length parameters.
*/
if (!EVP_EncryptInit_ex2(ctx, cipher, NULL, NULL, params))
goto err;
/* Initialise key and nonce */
if (!EVP_EncryptInit_ex(ctx, NULL, NULL, ccm_key, ccm_nonce))
goto err;
/* Set plaintext length: only needed if AAD is used */
/*!
参数4是NULL ? 那加密啥数据 ?
内部调用 ccm_set_iv(ctx, len), 设置向量, 用的是ctx中的向量和sizeof(ccm_pt)
* 跟到内部, 发现 ((out == NULL) && (in == NULL)) 时, 设置向量
*/
if (!EVP_EncryptUpdate(ctx, NULL, &outlen, NULL, sizeof(ccm_pt)))
goto err;
/* Zero or one call to specify any AAD */
/*! 参数2为空, 是输出为空. 应该也是设置一个参数
* 看给出的后2个参数, 是设置未加密的附加认证数据.
* 跟到内部, 发现 ((out == NULL) && (in != NULL)) 时, 设置认证数据
*/
if (!EVP_EncryptUpdate(ctx, NULL, &outlen, ccm_adata, sizeof(ccm_adata)))
goto err;
/* Encrypt plaintext: can only be called once */
/*! EVP_EncryptUpdate 可以调用多次, 为啥官方注释(上面一行)说只能调用一次? 等一会试试, 将明文拆成2块, 加密update2次试试 */
/*! 跟到内部, 发现 ((out != NULL) && (in != NULL)) 时, 是加密明文 */
if (!EVP_EncryptUpdate(ctx, outbuf, &outlen, ccm_pt, sizeof(ccm_pt)))
goto err;
/* Output encrypted block */
printf("Ciphertext:\n");
BIO_dump_fp(stdout, outbuf, outlen);
/* Finalise: note get no output for CCM */
if (!EVP_EncryptFinal_ex(ctx, NULL, &tmplen))
goto err;
/* Get tag */
params[0] = OSSL_PARAM_construct_octet_string(OSSL_CIPHER_PARAM_AEAD_TAG,
outtag, ccm_tag_len);
params[1] = OSSL_PARAM_construct_end();
if (!EVP_CIPHER_CTX_get_params(ctx, params))
goto err;
/* Output tag */
printf("Tag:\n");
BIO_dump_fp(stdout, outtag, ccm_tag_len);
ret = 1;
err:
if (!ret)
ERR_print_errors_fp(stderr);
EVP_CIPHER_free(cipher); /*! EVP_CIPHER_fetch() 出来的东西要释放 */
EVP_CIPHER_CTX_free(ctx); /*! EVP_CIPHER_CTX_new() 出来的东西要释放 */
return ret;
}
int aes_ccm_decrypt(void)
{
int ret = 0;
EVP_CIPHER_CTX *ctx;
EVP_CIPHER *cipher = NULL;
int outlen, rv;
unsigned char outbuf[1024];
size_t ccm_nonce_len = sizeof(ccm_nonce);
OSSL_PARAM params[3] = {
OSSL_PARAM_END, OSSL_PARAM_END, OSSL_PARAM_END
};
printf("AES CCM Decrypt:\n");
printf("Ciphertext:\n");
BIO_dump_fp(stdout, ccm_ct, sizeof(ccm_ct));
if ((ctx = EVP_CIPHER_CTX_new()) == NULL)
goto err;
/* Fetch the cipher implementation */
if ((cipher = EVP_CIPHER_fetch(libctx, "AES-192-CCM", propq)) == NULL)
goto err;
/* Set nonce length if default 96 bits is not appropriate */
params[0] = OSSL_PARAM_construct_size_t(OSSL_CIPHER_PARAM_AEAD_IVLEN,
&ccm_nonce_len);
/* Set tag length */
params[1] = OSSL_PARAM_construct_octet_string(OSSL_CIPHER_PARAM_AEAD_TAG,
(unsigned char *)ccm_tag,
sizeof(ccm_tag));
/*
* Initialise decrypt operation with the cipher & mode,
* nonce length and expected tag parameters.
*/
if (!EVP_DecryptInit_ex2(ctx, cipher, NULL, NULL, params))
goto err;
/* Specify key and IV */
if (!EVP_DecryptInit_ex(ctx, NULL, NULL, ccm_key, ccm_nonce))
goto err;
/* Set ciphertext length: only needed if we have AAD */
if (!EVP_DecryptUpdate(ctx, NULL, &outlen, NULL, sizeof(ccm_ct)))
goto err;
/* Zero or one call to specify any AAD */
if (!EVP_DecryptUpdate(ctx, NULL, &outlen, ccm_adata, sizeof(ccm_adata)))
goto err;
/* Decrypt plaintext, verify tag: can only be called once */
rv = EVP_DecryptUpdate(ctx, outbuf, &outlen, ccm_ct, sizeof(ccm_ct));
/* Output decrypted block: if tag verify failed we get nothing */
if (rv > 0) {
printf("Tag verify successful!\nPlaintext:\n");
BIO_dump_fp(stdout, outbuf, outlen);
} else {
printf("Tag verify failed!\nPlaintext not available\n");
goto err;
}
ret = 1;
err:
if (!ret)
ERR_print_errors_fp(stderr);
EVP_CIPHER_free(cipher);
EVP_CIPHER_CTX_free(ctx);
return ret;
}
int main(int argc, char **argv)
{
if (!aes_ccm_encrypt())
return EXIT_FAILURE;
if (!aes_ccm_decrypt())
return EXIT_FAILURE;
return EXIT_SUCCESS;
}
