HP OpenVMS Systems Documentation

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HP Open Source Security for OpenVMS Volume 2: HP SSL for OpenVMS > Chapter 5 Example Programs

Simple SSL Server Program

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The following is the program listing of the SSL$SIMPLE_SERV.C example program.

/*
* ++
* FACILITY:
*
* Simplest SSL Server
*
* ABSTRACT:
*
* This is an example of a SSL server with minimum functionality.
* The socket APIs are used to handle TCP/IP operations. This SSL
* server loads its own certificate and key, but it does not verify
* the certificate of the SSL client.
*
 */
/* Assumptions, Build, Configuration, and Execution Instructions */
/*
* ASSUMPTIONS:
*
* The following are assumed to be true for the
* execution of this program to succeed:
*
* - SSL is installed and started on this system.
*
* - this server program, and its accompanying client
* program are run on the same system, but in different
* processes.
*
* - the certificate and keys referenced by this program
* reside in the same directory as this program. There
* is a command procedure, SSL$EXAMPLES_SETUP.COM, to
* help set up the certificates and keys.
*
*
* BUILD INSTRUCTIONS:
*
* To build this example program use commands of the form,
*
* For a 32-bit application using only SSL APIs needs to run the
* following commands for SSL_APP.C .
* -----------------------------------------------------------------
* $CC/POINTER_SIZE=32/PREFIX_LIBRARY_ENTRIES=ALL_ENTRIES SSL_APP.C
* $LINK SSL_APP.OBJ, VMS_DECC_OPTIONS.OPT/OPT
* -----------------------------------------------------------------
* VMS_DECC_OPTIONS.OPT should include the following lines.
* -------------------------------------------------
* SYS$LIBRARY:SSL$LIBCRYPTO_SHR32.EXE/SHARE
* SYS$LIBRARY:SSL$LIBSSL_SHR32.EXE/SHARE
* -------------------------------------------------
*
* Creating a 64-bit application of SSL_APP.C should run the
* following commands.
* -----------------------------------------------------------------
* $CC/POINTER_SIZE=64/PREFIX_LIBRARY_ENTRIES=ALL_ENTRIES SSL_APP.C
* $LINK SSL_APP.OBJ, VMS_DECC_OPTIONS.OPT/OPT
* -----------------------------------------------------------------
* VMS_DECC_OPTIONS.OPT should include the following lines.
* -------------------------------------------------
* SYS$LIBRARY:SSL$LIBCRYPTO_SHR.EXE/SHARE
* SYS$LIBRARY:SSL$LIBSSL_SHR.EXE/SHARE
* -------------------------------------------------
*
*
* CONFIGURATION INSTRUCTIONS:
*
*
* RUN INSTRUCTIONS:
*
* To run this example program:
*
* 1) Start the server program,
*
* $ run server
*
* 2) Start the client program on this same system,
*
* $ run client
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <netdb.h>
#include <unistd.h>

#ifdef __VMS
#include <types.h>
#include <socket.h>
#include <in.h>
#include <inet.h>

#else
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#endif

#include <openssl/crypto.h>
#include <openssl/ssl.h>
#include <openssl/err.h>

#define RSA_SERVER_CERT "server.crt"
#define RSA_SERVER_KEY "server.key"

#define RSA_SERVER_CA_CERT "server_ca.crt"
#define RSA_SERVER_CA_PATH "sys$common:[syshlp.examples.ssl]"

#define ON 1
#define OFF 0

#define RETURN_NULL(x) if ((x)==NULL) exit(1)
#define RETURN_ERR(err,s) if ((err)==-1) { perror(s); exit(1); }
#define RETURN_SSL(err) if ((err)==-1) { ERR_print_errors_fp(stderr); exit(1); }

void main()
{
int err;
int verify_client = OFF; /* To verify a client certificate, set ON */

int listen_sock;
int sock;
struct sockaddr_in sa_serv;
struct sockaddr_in sa_cli;
size_t client_len;
char *str;
char buf[4096];

SSL_CTX *ctx;
SSL *ssl;
SSL_METHOD *meth;
        X509            *client_cert = NULL;

short int s_port = 5555;
/*----------------------------------------------------------------*/
/* Load encryption & hashing algorithms for the SSL program */
SSL_library_init();

/* Load the error strings for SSL & CRYPTO APIs */
SSL_load_error_strings();

/* Create a SSL_METHOD structure (choose a SSL/TLS protocol version) */
meth = SSLv3_method();

/* Create a SSL_CTX structure */
ctx = SSL_CTX_new(meth);

if (!ctx) {

ERR_print_errors_fp(stderr);

exit(1);

}

/* Load the server certificate into the SSL_CTX structure */
if (SSL_CTX_use_certificate_file(ctx, RSA_SERVER_CERT, SSL_FILETYPE_PEM) <= 0) {

ERR_print_errors_fp(stderr);

exit(1);

}

/* Load the private-key corresponding to the server certificate */
if (SSL_CTX_use_PrivateKey_file(ctx, RSA_SERVER_KEY, SSL_FILETYPE_PEM) <= 0) {

ERR_print_errors_fp(stderr);
exit(1);
}

/* Check if the server certificate and private-key matches */
if (!SSL_CTX_check_private_key(ctx)) {

fprintf(stderr,"Private key does not match the certificate public key\n");
exit(1);
}

if(verify_client == ON)

{

/* Load the RSA CA certificate into the SSL_CTX structure */
if (!SSL_CTX_load_verify_locations(ctx, RSA_SERVER_CA_CERT, NULL)) {

ERR_print_errors_fp(stderr);
exit(1);
}

/* Set to require peer (client) certificate verification */
SSL_CTX_set_verify(ctx,SSL_VERIFY_PEER,NULL);

/* Set the verification depth to 1 */
SSL_CTX_set_verify_depth(ctx,1);

}
/* ----------------------------------------------- */
/* Set up a TCP socket */

listen_sock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);

RETURN_ERR(listen_sock, "socket");
memset (&sa_serv, '\0', sizeof(sa_serv));
sa_serv.sin_family = AF_INET;
sa_serv.sin_addr.s_addr = INADDR_ANY;
sa_serv.sin_port = htons (s_port); /* Server Port number */
err = bind(listen_sock, (struct sockaddr*)&sa_serv,sizeof(sa_serv));

RETURN_ERR(err, "bind");

/* Wait for an incoming TCP connection. */
err = listen(listen_sock, 5);

RETURN_ERR(err, "listen");
client_len = sizeof(sa_cli);

/* Socket for a TCP/IP connection is created */
sock = accept(listen_sock, (struct sockaddr*)&sa_cli, &client_len);

RETURN_ERR(sock, "accept");
close (listen_sock);

printf ("Connection from %lx, port %x\n", sa_cli.sin_addr.s_addr,
sa_cli.sin_port);

/* ----------------------------------------------- */
/* TCP connection is ready. */
/* A SSL structure is created */
ssl = SSL_new(ctx);

RETURN_NULL(ssl);

/* Assign the socket into the SSL structure (SSL and socket without BIO) */
SSL_set_fd(ssl, sock);

/* Perform SSL Handshake on the SSL server */
err = SSL_accept(ssl);

RETURN_SSL(err);

/* Informational output (optional) */
printf("SSL connection using %s\n", SSL_get_cipher (ssl));

if (verify_client == ON)
{

/* Get the client's certificate (optional) */
client_cert = SSL_get_peer_certificate(ssl);
if (client_cert != NULL)
{

printf ("Client certificate:\n");
str = X509_NAME_oneline(X509_get_subject_name(client_cert), 0, 0);
RETURN_NULL(str);
printf ("\t subject: %s\n", str);
free (str);
str = X509_NAME_oneline(X509_get_issuer_name(client_cert), 0, 0);
RETURN_NULL(str);
printf ("\t issuer: %s\n", str);
free (str);
X509_free(client_cert);
}

else

printf("The SSL client does not have certificate.\n");
}

/*------- DATA EXCHANGE - Receive message and send reply. -------*/
/* Receive data from the SSL client */
err = SSL_read(ssl, buf, sizeof(buf) - 1);

RETURN_SSL(err);

buf[err] = '\0';

printf ("Received %d chars:'%s'\n", err, buf);

/* Send data to the SSL client */
err = SSL_write(ssl, "This message is from the SSL server",

strlen("This message is from the SSL server"));

RETURN_SSL(err);

/*--------------- SSL closure ---------------*/
/* Shutdown this side (server) of the connection. */

err = SSL_shutdown(ssl);

RETURN_SSL(err);

/* Terminate communication on a socket */
err = close(sock);

RETURN_ERR(err, "close");

/* Free the SSL structure */
SSL_free(ssl);

/* Free the SSL_CTX structure */
SSL_CTX_free(ctx);

}