基于openssl的aes_cbc加解密操作、基于libxml2的xml文件解析

基于openssl的aes_cbc加解密操作、基于libxml2的xml文件解析

基于aes的数据加解密需要提供两个额外的数据：密钥、初始向量

aes cbc加解密原理

cbc加密

CBC的加密从左往右看，初始化IV只有在第一个块加密的时候才会用到，而第N个块的加密IV则是用的N-1(N>1)个加密后的二进制数组。

cbc解密

CBC的解密则也是从左往右看，但是加密时IV在解密时候，只会用于对第一个块进行解密，其他块的解密则是使用上一块的加密二进制作为IV进行解密操作。
ps：通过加解密图解可知，初始向量IV在加密时针对整个待加密数据都起作用，但在解密时IV向量只针对第一个数据块起作用，因此在解密时，IV向量的重要度较低。

加解密源码

切记，在每次调用完加解密函数后，对应发IV向量的值会同步被修改

#include 
#include 
#include 
#include 
#include 
 
#define AESKEY "df98b715d5c6ed2b25817b6f255411a1"	//HEX密钥
#define AESIV "2841ae97419c2973296a0d4bdfe19a4f"	//HEX初始向量
 
//将文本形式的HEX串进行转换
unsigned char* str2hex(char *str)	
 {
    unsigned char *ret = NULL;
    int str_len = strlen(str);
    int i = 0;
    assert((str_len%2) == 0);
    ret = (char *)malloc(str_len/2);
    for (i =0;i < str_len; i = i+2 ) 
    {
        sscanf(str+i,"%2hhx",&ret[i/2]);
    }
    return ret;
}
 
int main()
{
    AES_KEY encryptkey;
    AES_KEY decryptkey;
 
    unsigned char *key;
    unsigned char *stdiv;
 
    key = str2hex(AESKEY);
    stdiv = str2hex(AESIV);
    AES_set_encrypt_key(key,128,&encryptkey);
    AES_set_decrypt_key(key,128,&decryptkey);
 
    unsigned char plain_text [32];
 
    memcpy(plain_text, "AES encrypt in openssl demo", 27);
    memset(plain_text + 27, 0, 5);
    //需要将加密区块长度填充为16字节整数倍，此处使用zero-padding，即末尾全用0填充
    printf("raw_text: ");
    for(int i = 0; i < 32; i++)
    {
        printf("%02X ", plain_text[i]);
    }
    printf("\n" );
 
    unsigned char encrypted_text [32];
    memset(1, 0, 32);
    unsigned char tmpiv[16];
    memcpy(tmpiv, stdiv, 16);
    AES_cbc_encrypt(plain_text, encrypted_text, 32, &encryptkey, tmpiv, AES_ENCRYPT);
    //初始向量这个参数每次使用都会将其改变，所以如果要多次加密且每次使用固定的初始向量，可以先用tmpiv接收
 
    printf("encrypted_text: " );
    for(int i = 0; i < 32; i++)
    {
        printf("%02X ", encrypted_text[i]);
    }
    printf("\n" );
 
    unsigned char decrypted_text [32];
    memset(decrypted_text, 0, 32);
    memcpy(tmpiv, stdiv, 16);
    AES_cbc_encrypt(encrypted_text, decrypted_text, 32, &decryptkey, tmpiv, AES_DECRYPT);
 
    printf("decrypted_text:");
    for(int i = 0; i < 32; i++)
    {
        printf("%02X ", decrypted_text[i]);
    }
    printf("\n");
    return 0;
}

编译及运行结果

@ubuntu:~/aes_source$ gcc test.c -o test -lssl -lcrypto
@ubuntu:~/aes_source$ ./test 
raw_text: 41 45 53 20 65 6E 63 72 79 70 74 20 69 6E 20 6F 70 65 6E 73 73 6C 20 64 65 6D 6F 00 00 00 00 00 
encrypted_text: 33 B7 65 49 2C 7E AB 0B 9C 90 2B 3A 0F 64 DF D3 60 A9 B6 7E 4D 9A 6F E0 08 19 EC AC E7 50 86 36 
decrypted_text:41 45 53 20 65 6E 63 72 79 70 74 20 69 6E 20 6F 70 65 6E 73 73 6C 20 64 65 6D 6F 00 00 00 00 00 
@ubuntu:~/aes_source$ 

基于libxml2的xml文件解析

libxml2 安装及环境配置

参考link

xml文件

<?xml version="1.0" encoding="UTF-8"?>
<bmp_para>
  <para id="1">
     <width>1920</width>
     <height>1080</height>
     <bit>3</bit>
     <blue>0</blue>
     <green>0</green>
     <red>255</red>     
  </para>
</bmp_para>

xml解析源码

#include 
#include 
 
#include 
#include 
 
#define DEFAULT_XML_FILE "test.xml"
 
//解析para字段，提取出width,height,bit,red,green,blue参数
static int parse_bmp(xmlDocPtr doc, xmlNodePtr cur)
{
    assert(doc || cur);
    xmlChar *key;
 
    cur = cur->xmlChildrenNode;
    while (cur != NULL) {
	    //获取width
	    if ((!xmlStrcmp(cur->name, (const xmlChar *)"width"))) {
	        key = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
	        printf("width: %s\r\n", key);
	        xmlFree(key);
	    }
	    //获取height
	    if ((!xmlStrcmp(cur->name, (const xmlChar *)"height"))) {
	        key = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
	        printf("height: %s\r\n", key);
	        xmlFree(key);
	    }
	    //获取bit
	    if ((!xmlStrcmp(cur->name, (const xmlChar *)"bit"))) {
	        key = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
	        printf("bit: %s\r\n", key);
	        xmlFree(key);
	    }
	    //获取 blue
	    if ((!xmlStrcmp(cur->name, (const xmlChar *)"blue"))) {
	        key = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
	        printf("blue: %s\r\n", key);
	        xmlFree(key);
	    }
	    //获取 green
	    if ((!xmlStrcmp(cur->name, (const xmlChar *)"green"))) {
	        key = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
	        printf("green: %s\r\n", key);
	        xmlFree(key);
	    }
	    //获取 red
	    if ((!xmlStrcmp(cur->name, (const xmlChar *)"red"))) {
	        key = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
	        printf("red: %s\r\n", key);
	        xmlFree(key);
	    }

	    cur = cur->next;
    }
    return 0;
}
 
static int parse_para(const char *file_name)
{
	assert(file_name);

	xmlDocPtr doc;   //xml整个文档的树形结构
	xmlNodePtr cur;  //xml节点
	xmlChar *id;     //phone id

	//获取树形结构
	doc = xmlParseFile(file_name);
	if (doc == NULL) {
		fprintf(stderr, "Failed to parse xml file:%s\n", file_name);
		goto FAILED;
	}

	//获取根节点
	cur = xmlDocGetRootElement(doc);
	if (cur == NULL) {
		fprintf(stderr, "Root is empty.\n");
		goto FAILED;
	}

	if ((xmlStrcmp(cur->name, (const xmlChar *)"bmp_para"))) {
		fprintf(stderr, "The root is not bmp_para.\n");
		goto FAILED;
	}

	//遍历处理根节点的每一个子节点
	cur = cur->xmlChildrenNode;
	while (cur != NULL) {
		if ((!xmlStrcmp(cur->name, (const xmlChar *)"para"))) {
			id = xmlGetProp(cur, "id");
			printf("id:%s\r\n",id);
			parse_bmp(doc, cur);
		}
		cur = cur->next;
	}
	xmlFreeDoc(doc);
	return 0;
	FAILED:
	if (doc) {
		xmlFreeDoc(doc);
	}
	return -1;
}
 
int main(int argc, char*argv[])
{
    char cFileNameRead[64] = {0}; 

	if(argc < 2)
	{
		printf("please input like this:\r\n");
		printf("./testReadXml.bin test.xml \r\n");
		printf("test.xml --------------- input xml file \r\n");
		return -1;
	}

    sprintf(cFileNameRead,"%s",argv[1]);
	printf("cFileNameRead=%s\r\n",cFileNameRead);

	if (parse_para(cFileNameRead) != 0) {
		fprintf(stderr, "Failed to parse bmp para.\n");
		return -1;
	}

	return 0;
}

编译并运行xml解析结果：

@ubuntu:~/xml$ gcc test.c -o test.bin -I /mnt/lib2xml/output/include/libxml2/ -L /mnt/lib2xml/output/lib/ -lxml2
@ubuntu:~/xml$ ./test.bin test.xml 
cFileNameRead=test.xml
id:1
width: 1920
height: 1080
bit: 3
blue: 0
green: 0
red: 255