2019-2020-1 20175210 20175211 20175219 实验五 通讯协议设计

实验五 通讯协议设计-1

• 两人一组
• 基于Socket实现TCP通信，一人实现服务器，一人实现客户端
• 研究OpenSSL算法，测试对称算法中的AES，非对称算法中的RSA，Hash算法中的MD5
• 选用合适的算法，基于混合密码系统实现对TCP通信进行机密性、完整性保护
• 学有余力者，对系统进行安全性分析和改进

TCP通信

实验截图

实验代码

客户端

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/types.h>
#include <unistd.h>

#define BUFLEN 10

int main(int argc, char **argv)
{
    int sockfd;
    struct sockaddr_in s_addr;
    socklen_t len;
    unsigned int port;
    char buf[BUFLEN];    
    if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1){
        perror("socket");
        exit(errno);
    }  
    if(argv[2])
        port = atoi(argv[2]);
    else
        port = 5219;
    bzero(&s_addr, sizeof(s_addr));
    s_addr.sin_family = AF_INET;
    s_addr.sin_port = htons(port);
    if (inet_aton(argv[1], (struct in_addr *)&s_addr.sin_addr.s_addr) == 0) {
        perror(argv[1]);
        exit(errno);
    }   
    if(connect(sockfd,(struct sockaddr*)&s_addr,sizeof(struct sockaddr)) == -1){
        perror("connect");
        exit(errno);
    }
    
    while(1){
        bzero(buf,BUFLEN);
        len = recv(sockfd,buf,BUFLEN,0);
        if(len > 0)
            printf("服务器:%s\n",buf);
        bzero(buf,BUFLEN);
        fgets(buf,BUFLEN,stdin);
        if(strchr(buf,'\n'))
            len = send(sockfd,buf,strlen(buf)-1,0);   
        else
            len = send(sockfd,buf,strlen(buf),0);
    }
    close(sockfd);
    return 0;
}

服务器

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/types.h>
#include <unistd.h>

#define BUFLEN 10

int main(int argc, char **argv)
{
    int sockfd, newfd;
    struct sockaddr_in s_addr, c_addr;
    char buf[BUFLEN];
    socklen_t len;
    unsigned int port, listnum;
    if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1)
    {
        perror("socket");
        exit(errno);
    }
    if(argv[2])
        port = atoi(argv[2]);
    else
        port = 4567;
    if(argv[3])
        listnum = atoi(argv[3]);
    else
        listnum = 3;
    bzero(&s_addr, sizeof(s_addr));
    s_addr.sin_family = AF_INET;
    s_addr.sin_port = htons(port);
    if(argv[1])
        s_addr.sin_addr.s_addr = inet_addr(argv[1]);
    else
        s_addr.sin_addr.s_addr = INADDR_ANY;
    if((bind(sockfd, (struct sockaddr*) &s_addr,sizeof(struct sockaddr))) == -1)
    {
        perror("bind");
        exit(errno);
    }
    if(listen(sockfd,listnum) == -1)
    {
        perror("listen");
        exit(errno);
    }
    while(1)
    {
        len = sizeof(struct sockaddr);
        if((newfd = accept(sockfd,(struct sockaddr*) &c_addr, &len)) == -1)
        {
            perror("accept");
            exit(errno);
        }
        else
            printf("正在与您聊天的客户端是：%s: %d\n",inet_ntoa(c_addr.sin_addr),ntohs(c_addr.sin_port));
        while(1)
        {
            bzero(buf,BUFLEN);
            fgets(buf,BUFLEN,stdin);
            if(strchr(buf,'\n'))
                len = send(newfd,buf,strlen(buf)-1,0);
            else
                len = send(newfd,buf,strlen(buf),0);
            bzero(buf,BUFLEN);
            len = recv(newfd,buf,BUFLEN,0);
            if(len > 0)
                printf("客户端：%s\n",buf);
        }
        close(newfd);
        bzero(buf, BUFLEN);
        fgets(buf,BUFLEN, stdin);
        if(!strncasecmp(buf,"y",1))
        {
            printf("server 退出!\n");
            break;
        }
    }
    close(sockfd);
    return 0;
}

OpenSSL算法

AES

实验截图

实验代码

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <openssl/aes.h>

int main(int argc, char** argv) {
    AES_KEY aes;
    unsigned char key[AES_BLOCK_SIZE];        
    unsigned char iv[AES_BLOCK_SIZE];        
    unsigned char* input_string;
    unsigned char* encrypt_string;
    unsigned char* decrypt_string;
    unsigned int len;        
    unsigned int i;
    if (argc != 2) {
        fprintf(stderr, "%s <plain text>\n", argv[0]);
        exit(-1);
    }
    len = 0;
    if ((strlen(argv[1]) + 1) % AES_BLOCK_SIZE == 0) {
        len = strlen(argv[1]) + 1;
    } else {
        len = ((strlen(argv[1]) + 1) / AES_BLOCK_SIZE + 1) * AES_BLOCK_SIZE;
    }
    input_string = (unsigned char*)calloc(len, sizeof(unsigned char));
    if (input_string == NULL) {
        fprintf(stderr, "Unable to allocate memory for input_string\n");
        exit(-1);
    }
    strncpy((char*)input_string, argv[1], strlen(argv[1]));
    for (i=0; i<16; ++i) {
        key[i] = 32 + i;
    }
    for (i=0; i<AES_BLOCK_SIZE; ++i) {
        iv[i] = 0;
    }
    if (AES_set_encrypt_key(key, 128, &aes) < 0) {
        fprintf(stderr, "Unable to set encryption key in AES\n");
        exit(-1);
    }

    // alloc encrypt_string
    encrypt_string = (unsigned char*)calloc(len, sizeof(unsigned char));    
    if (encrypt_string == NULL) {
        fprintf(stderr, "Unable to allocate memory for encrypt_string\n");
        exit(-1);
    }
    AES_cbc_encrypt(input_string, encrypt_string, len, &aes, iv, AES_ENCRYPT);
    decrypt_string = (unsigned char*)calloc(len, sizeof(unsigned char));
    if (decrypt_string == NULL) {
        fprintf(stderr, "Unable to allocate memory for decrypt_string\n");
        exit(-1);
    }
    for (i=0; i<AES_BLOCK_SIZE; ++i) {
        iv[i] = 0;
    }
    if (AES_set_decrypt_key(key, 128, &aes) < 0) {
        fprintf(stderr, "Unable to set decryption key in AES\n");
        exit(-1);
    }
    AES_cbc_encrypt(encrypt_string, decrypt_string, len, &aes, iv, AES_DECRYPT);
    printf("encrypted:");
    for (i=0; i<len; ++i) {
        printf("%x%x", (encrypt_string[i] >> 4) & 0xf, encrypt_string[i] & 0xf);    
    }
    printf("\n");
    printf("decrypted:%s\n", decrypt_string);

    return 0;
}

RSA

实验截图

实验代码

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<openssl/rsa.h>
#include<openssl/pem.h>
#include<openssl/err.h>
#define OPENSSLKEY "test.key"
#define PUBLICKEY "test_pub.key"
#define BUFFSIZE 1024
char* my_encrypt(char *str,char *path_key);
char* my_decrypt(char *str,char *path_key);
int main(void){
    char *source="20175210mt20175211lyz2017519llq";
    char *ptr_en,*ptr_de;
    printf("test:%s\n",source);
    ptr_en=my_encrypt(source,PUBLICKEY);
    printf("encrypt:%s\n",ptr_en);
    ptr_de=my_decrypt(ptr_en,OPENSSLKEY);
    printf("decrypt:%s\n",ptr_de);
    if(ptr_en!=NULL){
        free(ptr_en);
    }   
    if(ptr_de!=NULL){
        free(ptr_de);
    }   
    return 0;
}
char *my_encrypt(char *str,char *path_key){
    char *p_en;
    RSA *p_rsa;
    FILE *file;
    int flen,rsa_len;
    if((file=fopen(path_key,"r"))==NULL){
        perror("open key file error");
        return NULL;    
    }   
    if((p_rsa=PEM_read_RSA_PUBKEY(file,NULL,NULL,NULL))==NULL){
        ERR_print_errors_fp(stdout);
        return NULL;
    }   
    flen=strlen(str);
    rsa_len=RSA_size(p_rsa);
    p_en=(unsigned char *)malloc(rsa_len+1);
    memset(p_en,0,rsa_len+1);
    if(RSA_public_encrypt(rsa_len,(unsigned char *)str,(unsigned char*)p_en,p_rsa,RSA_NO_PADDING)<0){
        return NULL;
    }
    RSA_free(p_rsa);
    fclose(file);
    return p_en;
}
char *my_decrypt(char *str,char *path_key){
    char *p_de;
    RSA *p_rsa;
    FILE *file;
    int rsa_len;
    if((file=fopen(path_key,"r"))==NULL){
        perror("open key file error");
        return NULL;
    }
    if((p_rsa=PEM_read_RSAPrivateKey(file,NULL,NULL,NULL))==NULL){
        ERR_print_errors_fp(stdout);
        return NULL;
    }
    rsa_len=RSA_size(p_rsa);
    p_de=(unsigned char *)malloc(rsa_len+1);
    memset(p_de,0,rsa_len+1);
    if(RSA_private_decrypt(rsa_len,(unsigned char *)str,(unsigned char*)p_de,p_rsa,RSA_NO_PADDING)<0){
        return NULL;
    }
    RSA_free(p_rsa);
    fclose(file);
    return p_de;
}

MD5

实验截图

实验代码

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <openssl/md5.h>

int main(int argc, char** argv) {
    MD5_CTX hash_ctx;
    char input_string[128];
    unsigned char hash_ret[16];
    int i;
    if (argc != 2) {
        fprintf(stderr, "%s <input string>\n", argv[0]);
        exit(-1);
    }
    snprintf(input_string, sizeof(input_string), "%s\n", argv[1]);
    MD5_Init(&hash_ctx);
    MD5_Update(&hash_ctx, input_string, strlen(input_string));
    MD5_Final(hash_ret, &hash_ctx);
    printf("Output: ");
    for (i=0; i<32; ++i) {
        if (i % 2 == 0) {
            printf("%x", (hash_ret[i/2] >> 4) & 0xf);
        } else {
            printf("%x", (hash_ret[i/2]) & 0xf);
        }
    }
    printf("\n");

    return 0;
}

实验五 通讯协议设计-2

• 在Ubuntu中实现对实验二中的“wc服务器”通过混合密码系统进行防护
• 提交测试截图

实验截图

实验代码

客户端

#include <stdio.h>  
#include <string.h>  
#include <errno.h>  
#include <sys/socket.h>  
#include <resolv.h>  
#include <stdlib.h>  
#include <netinet/in.h>  
#include <arpa/inet.h>  
#include <unistd.h>  
#include <openssl/ssl.h>  
#include <openssl/err.h>
 #include <openssl/evp.h>
  
  
#define MAXBUF 1024  
  
void ShowCerts(SSL * ssl)  
{  
    X509 *cert;  
    char *line;  
    cert = SSL_get_peer_certificate(ssl);  
    if (cert != NULL) {  
        printf("数字证书信息:\n");  
        line = X509_NAME_oneline(X509_get_subject_name(cert), 0, 0);  
        printf("证书: %s\n", line);  
        free(line);  
        line = X509_NAME_oneline(X509_get_issuer_name(cert), 0, 0);  
        printf("颁发者: %s\n", line);  
        free(line);  
       X509_free(cert);  
    } else  
        printf("无证书信息！\n");  
}  
  int main(int argc, char **argv)  
{  
    int sockfd, len;  
    struct sockaddr_in dest;  
    char buffer[MAXBUF + 1];  
    SSL_CTX *ctx;  
    SSL *ssl;   
    SSL_library_init();  
    OpenSSL_add_all_algorithms();  
    SSL_load_error_strings();  
    ctx = SSL_CTX_new(SSLv23_client_method());  
    if (ctx == NULL) {  
        ERR_print_errors_fp(stdout);  
        exit(1);  
    } 
    if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {  
        perror("Socket");  
        exit(errno);  
    }  
    printf("socket created\n");   
    bzero(&dest, sizeof(dest));  
    dest.sin_family = AF_INET;  
    dest.sin_port = htons(atoi(argv[2]));  
    if (inet_aton(argv[1], (struct in_addr *) &dest.sin_addr.s_addr) == 0) {  
        perror(argv[1]);  
        exit(errno);  
    }  
    printf("address created\n");  
    if (connect(sockfd, (struct sockaddr *) &dest, sizeof(dest)) != 0) {  
        perror("Connect ");  
        exit(errno);  
    }  
    printf("server connected\n");  
    ssl = SSL_new(ctx);  
    SSL_set_fd(ssl, sockfd);    
    if (SSL_connect(ssl) == -1)  
        ERR_print_errors_fp(stderr);  
    else {  
        printf("Connected with %s encryption\n", SSL_get_cipher(ssl));  
        ShowCerts(ssl);  
    }  
    bzero(buffer, MAXBUF + 1);  
    len = SSL_read(ssl, buffer, MAXBUF);  
    if (len > 0)  
        printf("服务器:%s\n",buffer);  
    bzero(buffer, MAXBUF + 1);  
    strcpy(buffer, "hi");  
    len = SSL_write(ssl, buffer, strlen(buffer));    
    SSL_shutdown(ssl);  
    SSL_free(ssl);  
    close(sockfd);  
    SSL_CTX_free(ctx);  
    return 0;  
}

服务器

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <openssl/ssl.h>
#include <openssl/err.h>
 #include <openssl/evp.h>


#define MAXBUF 1024

int main(int argc, char **argv)
{
    int sockfd, new_fd;
    socklen_t len;
    struct sockaddr_in my_addr, their_addr;
    unsigned int myport, lisnum;
    char buf[MAXBUF + 1];
    SSL_CTX *ctx;
    if (argv[1])
        myport = atoi(argv[1]);
    if (argv[2])
        lisnum = atoi(argv[2]);
    else
        lisnum = 2;
    SSL_library_init();
    OpenSSL_add_all_algorithms();
    SSL_load_error_strings();
    ctx = SSL_CTX_new(SSLv23_server_method());
    if (ctx == NULL) {
        ERR_print_errors_fp(stdout);
        exit(1);
    }
    if (SSL_CTX_use_certificate_file(ctx, argv[3], SSL_FILETYPE_PEM) <= 0) {
        ERR_print_errors_fp(stdout);
        exit(1);
    }
    if (SSL_CTX_use_PrivateKey_file(ctx, argv[4], SSL_FILETYPE_PEM) <= 0){
        ERR_print_errors_fp(stdout);
        exit(1);
    }
    if (!SSL_CTX_check_private_key(ctx)) {
        ERR_print_errors_fp(stdout);
        exit(1);
    }
    if ((sockfd = socket(PF_INET, SOCK_STREAM, 0)) == -1) {
        perror("socket");
        exit(1);
    }
    bzero(&my_addr, sizeof(my_addr));
    my_addr.sin_family = PF_INET;
    my_addr.sin_port = htons(myport);
    my_addr.sin_addr.s_addr = INADDR_ANY;
    if (bind(sockfd, (struct sockaddr *) &my_addr, sizeof(struct sockaddr))
        == -1) {
        perror("bind");
        exit(1);
    } ;
    if (listen(sockfd, lisnum) == -1) {
        perror("listen");
        exit(1);
    } else
    while (1) {
        SSL *ssl;
        len = sizeof(struct sockaddr);
        if ((new_fd =accept(sockfd, (struct sockaddr *) &their_addr,&len)) == -1) {
            perror("accept");
            exit(errno);
        } 
        ssl = SSL_new(ctx);
        SSL_set_fd(ssl, new_fd);
        if (SSL_accept(ssl) == -1) {
            perror("accept");
            close(new_fd);
            break;
        }
        bzero(buf, MAXBUF + 1);
        strcpy(buf, "hello");
        len = SSL_write(ssl, buf, strlen(buf));
        bzero(buf, MAXBUF + 1);
        len = SSL_read(ssl, buf, MAXBUF);
        if (len > 0)
            printf("客户端：%s\n",buf);
        SSL_shutdown(ssl);
        SSL_free(ssl);
        close(new_fd);
    }
    close(sockfd);
    SSL_CTX_free(ctx);
    return 0;
}

遇到的问题

证书的key过短

用命令自定义一个较长的key并重新生成证书