Client-Server communication using OPENSSL (using Certificate)

Question

I'm using http://simplestcodings.blogspot.com.br/2010/08/secure-server-client-using-openssl-in-c.html to generate client-server that communicate with each other using OPENSSL.

I generate the certificate using same way as mention in the site and then I did run server part successfully.

I did the client part too.But when i run,i got several error mention below(From Server side).

Usage: 5000 LoadCertificates Compleate Successfully..... 139761812350824:error:140C5042:SSL routines:SSL_UNDEFINED_FUNCTION:called a function you should not call:ssl_lib.c:2421: Connection: 127.0.0.1:57320 139761812350824:error:140C5042:SSL routines:SSL_UNDEFINED_FUNCTION:called a function you should not call:ssl_lib.c:2421: 139761812350824:error:140C5042:SSL routines:SSL_UNDEFINED_FUNCTION:called a function you should not call:ssl_lib.c:2421: 139761812350824:error:140780E5:SSL routines:SSL23_READ:ssl handshake failure:s23_lib.c:138: Connection: 127.0.0.1:57402 No certificates.

My code is slightly modified................

//client

#include <stdio.h>
#include <errno.h>
#include <unistd.h>
#include <malloc.h>
#include <string.h>
#include <sys/socket.h>
#include <resolv.h>
#include <netdb.h>
#include <openssl/ssl.h>
#include <openssl/err.h>

#define FAIL    -1

int OpenConnection(const char *hostname, int port)
{   int sd;
struct hostent *host;
struct sockaddr_in addr;

if ( (host = gethostbyname(hostname)) == NULL )
{
    printf('Eroor: %s\n',hostname);
    perror(hostname);
    abort();
}
sd = socket(PF_INET, SOCK_STREAM, 0);
bzero(&addr, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_port = htons(port);
addr.sin_addr.s_addr = *(long*)(host->h_addr);
if ( connect(sd, (struct sockaddr*)&addr, sizeof(addr)) != 0 )
{
    close(sd);
    perror(hostname);
    abort();
}
return sd;
}

SSL_CTX* InitCTX(void)
{   SSL_METHOD *method;
SSL_CTX *ctx;

OpenSSL_add_all_algorithms();  /* Load cryptos, et.al. */
SSL_load_error_strings();   /* Bring in and register error messages */
method = SSLv2_client_method();  /* Create new client-method instance */
ctx = SSL_CTX_new(method);   /* Create new context */
if ( ctx == NULL )
{
    ERR_print_errors_fp(stderr);
    printf('Eroor: %s\n',stderr);
    abort();
}
return ctx;
}

void ShowCerts(SSL* ssl)
{   X509 *cert;
    char *line;

    cert = SSL_get_peer_certificate(ssl); /* get the server's certificate */
    if ( cert != NULL )
    {
    printf("Server certificates:\n");
    line = X509_NAME_oneline(X509_get_subject_name(cert), 0, 0);
    printf("Subject: %s\n", line);
    free(line);       /* free the malloc'ed string */
    line = X509_NAME_oneline(X509_get_issuer_name(cert), 0, 0);
    printf("Issuer: %s\n", line);
    free(line);       /* free the malloc'ed string */
    X509_free(cert);     /* free the malloc'ed certificate copy */
}
else
    printf("No certificates.\n");
}

int main(int count, char *strings[])
{   SSL_CTX *ctx;
int server;
SSL *ssl;
char buf[1024];
int bytes;
char *hostname, *portnum;

if ( count != 3 )
{
    printf("usage: %s <hostname> <portnum>\n", strings[0]);
    exit(0);
}


SSL_library_init();
hostname=strings[1];
portnum=strings[2];

ctx = InitCTX();
server = OpenConnection(hostname, atoi(portnum));
ssl = SSL_new(ctx);      /* create new SSL connection state */
SSL_set_fd(ssl, server);    /* attach the socket descriptor */
if ( SSL_connect(ssl) == FAIL )   /* perform the connection */
{
    printf('Eroor: %s\n',stderr);
    ERR_print_errors_fp(stderr);
}
else
{   char *msg = "Hello???";

    printf("Connected with %s encryption\n", SSL_get_cipher(ssl));
    ShowCerts(ssl);        /* get any certs */
    SSL_write(ssl, msg, strlen(msg));   /* encrypt & send message */
    bytes = SSL_read(ssl, buf, sizeof(buf)); /* get reply & decrypt */
    buf[bytes] = 0;
    printf("Received: \"%s\"\n", buf);
    SSL_free(ssl);        /* release connection state */
}
close(server);         /* close socket */
SSL_CTX_free(ctx);        /* release context */
return 0;
}

---

#include <errno.h>
#include <unistd.h>
#include <malloc.h>
#include <string.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <resolv.h>
#include "openssl/ssl.h"
#include "openssl/err.h"

#define FAIL    -1
using namespace std;

int OpenListener(int port)
{   int sd;
struct sockaddr_in addr;

sd = socket(PF_INET, SOCK_STREAM, 0);
bzero(&addr, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_port = htons(port);
addr.sin_addr.s_addr = INADDR_ANY;
if ( bind(sd, (struct sockaddr*)&addr, sizeof(addr)) != 0 )
{
    perror("can't bind port");
    abort();
}
if ( listen(sd, 10) != 0 )
{
    perror("Can't configure listening port");
    abort();
}
return sd;
}

SSL_CTX* InitServerCTX(void)
{
SSL_CTX *ctx = NULL;

    #if OPENSSL_VERSION_NUMBER >= 0x10000000L
           const SSL_METHOD *method;
    #else
            SSL_METHOD *method;
    #endif

    SSL_library_init();
    OpenSSL_add_all_algorithms();  /* load & register all cryptos, etc. */
    SSL_load_error_strings();   /* load all error messages */



    method = SSLv23_client_method(); /* create new server-method instance */
    ctx = SSL_CTX_new(method);   /* create new context from method */
    if ( ctx == NULL )
    {
        ERR_print_errors_fp(stderr);
        abort();
    }
    return ctx;
}

void LoadCertificates(SSL_CTX* ctx, char* CertFile, char* KeyFile)
{
//New lines
    if (SSL_CTX_load_verify_locations(ctx, CertFile, KeyFile) != 1)
        ERR_print_errors_fp(stderr);

    if (SSL_CTX_set_default_verify_paths(ctx) != 1)
        ERR_print_errors_fp(stderr);
    //End new lines
/* set the local certificate from CertFile */
if ( SSL_CTX_use_certificate_file(ctx, CertFile, SSL_FILETYPE_PEM) <= 0 )
{
    ERR_print_errors_fp(stderr);
    abort();
}
/* set the private key from KeyFile (may be the same as CertFile) */
if ( SSL_CTX_use_PrivateKey_file(ctx, KeyFile, SSL_FILETYPE_PEM) <= 0 )
{
    ERR_print_errors_fp(stderr);
    abort();
}
/* verify private key */
if ( !SSL_CTX_check_private_key(ctx) )
{
    fprintf(stderr, "Private key does not match the public certificate\n");
    abort();
}
printf("LoadCertificates Compleate Successfully.....\n");
}

void ShowCerts(SSL* ssl)
{   X509 *cert;
char *line;

cert = SSL_get_peer_certificate(ssl); /* Get certificates (if available) */
if ( cert != NULL )
{
    printf("Server certificates:\n");
    line = X509_NAME_oneline(X509_get_subject_name(cert), 0, 0);
    printf("Subject: %s\n", line);
    free(line);
    line = X509_NAME_oneline(X509_get_issuer_name(cert), 0, 0);
    printf("Issuer: %s\n", line);
    free(line);
    X509_free(cert);
}
else
    printf("No certificates.\n");
}

void Servlet(SSL* ssl) /* Serve the connection -- threadable */
{   char buf[1024];
char reply[1024];
int sd, bytes;
const char* HTMLecho="<html><body><pre>%s</pre></body></html>\n\n";

if ( SSL_accept(ssl) == FAIL )     /* do SSL-protocol accept */
    ERR_print_errors_fp(stderr);
else
{
    ShowCerts(ssl);        /* get any certificates */
    bytes = SSL_read(ssl, buf, sizeof(buf)); /* get request */
    if ( bytes > 0 )
    {
        buf[bytes] = 0;
        printf("Client msg: \"%s\"\n", buf);
        sprintf(reply, HTMLecho, buf);   /* construct reply */
        SSL_write(ssl, reply, strlen(reply)); /* send reply */
    }
    else
        ERR_print_errors_fp(stderr);
}
sd = SSL_get_fd(ssl);       /* get socket connection */
SSL_free(ssl);         /* release SSL state */
close(sd);          /* close connection */
}

int main(int count, char *strings[])
{   SSL_CTX *ctx;
int server;
char *portnum;

if ( count != 2 )
{
    printf("Usage: %s <portnum>\n", strings[0]);
    exit(0);
}
else
{
    printf("Usage: %s <portnum>\n", strings[1]);
}
SSL_library_init();

portnum = strings[1];
ctx = InitServerCTX();        /* initialize SSL */
LoadCertificates(ctx, "/home/stud/kawsar/mycert.pem", "/home/stud/kawsar/mycert.pem");  /* load certs */
server = OpenListener(atoi(portnum));    /* create server socket */
while (1)
{   struct sockaddr_in addr;
    socklen_t len = sizeof(addr);
    SSL *ssl;

    int client = accept(server, (struct sockaddr*)&addr, &len);  /* accept connection   as usual */
    printf("Connection: %s:%d\n",inet_ntoa(addr.sin_addr), ntohs(addr.sin_port));
    ssl = SSL_new(ctx);              /* get new SSL state with context */
    SSL_set_fd(ssl, client);      /* set connection socket to SSL state */
    Servlet(ssl);         /* service connection */
}
close(server);          /* close server socket */
SSL_CTX_free(ctx);         /* release context */
}

Solution

You are using the wrong method in InitServerContext

SSLv23_client_method.

It should be SSLv23_method