/*
 * ++
 * FACILITY:
 *
 *      Simplest SSL Client + "Socket BIO" + "client certificate verification"
 *
 * ABSTRACT:
 *
 *      This is an example of a SSL client with minimum functionality (using Socket BIO).
 *      The socket APIs are used to handle TCP/IP operations.
 *
 *      This SSL client verifies the server's certificate against the CA
 *      certificate loaded in the client.
 *
 *      This SSL client loads its own certificate and key for the
 *      client certificate verification on the SSL server.
 *
 * ENVIRONMENT:
 *
 *    OpenVMS Alpha V7.2-2
 *    TCP/IP Services V5.0A or higher
 *
 * AUTHOR:
 *
 *    Taka Shinagawa, OpenVMS Security Group
 *
 * CREATION DATE:
 *
 *    1-Jan-2002
 *
 * --
 */


/* 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, SSL1$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:SSL1$LIBCRYPTO_SHR32.EXE/SHARE
 *       SYS$LIBRARY:SSL1$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:SSL1$LIBCRYPTO_SHR.EXE/SHARE
 *       SYS$LIBRARY:SSL1$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 <string.h>
#include <errno.h>
#include <netdb.h>
#include <unistd.h>

#ifdef __VMS
#include <socket.h>
#include <inet.h>
#include <in.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 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); }

static int verify_callback(int ok, X509_STORE_CTX *ctx);

#define RSA_CLIENT_CERT	"client.crt"
#define RSA_CLIENT_KEY 	"client.key"

#define RSA_CLIENT_CA_CERT      "client_ca.crt"
#define RSA_CLIENT_CA_PATH      "sys$common:[syshlp.examples.ssl1]"

#define ON      1
#define OFF     0

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

  	int 	sock;
  	struct sockaddr_in server_addr;
  	char	*str;
  	char  	buf [4096];
  	char 	hello[80];

	SSL_CTX 	*ctx;
        SSL     	*ssl;
	const SSL_METHOD 	*meth;
	X509    	*server_cert;
	BIO		*sbio = NULL;

        EVP_PKEY        *pkey;

	short int 	s_port = 5555;
	const char	*s_ipaddr = "127.0.0.1";
       
	/*----------------------------------------------------------*/
  	printf ("Message to be sent to the SSL server: ");
  	fgets (hello, 80, stdin);
	
	/* 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 const SSL_METHOD structure (choose a SSL/TLS protocol version) */
  	meth = SSLv3_method();

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

	/*-------------------------------------------------------------------------*/
        if(verify_client == ON)
        {
		/* Load the client certificate into the SSL_CTX structure */
		if (SSL_CTX_use_certificate_file(ctx, RSA_CLIENT_CERT, SSL_FILETYPE_PEM) <= 0) {
                	ERR_print_errors_fp(stderr);
                	exit(1);
		}

		/* Load the private-key corresponding to the client certificate */
	        if (SSL_CTX_use_PrivateKey_file(ctx, RSA_CLIENT_KEY, SSL_FILETYPE_PEM) <= 0) {
        	        ERR_print_errors_fp(stderr);
                	exit(1);
        	}

		/* Check if the client 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);
        	}
	}

	/* Load the RSA CA certificate into the SSL_CTX structure */
	if (!SSL_CTX_load_verify_locations(ctx, RSA_CLIENT_CA_CERT, NULL)) {
                ERR_print_errors_fp(stderr);
                exit(1);
	}

        /* Set to require peer (server) certificate verification */
        SSL_CTX_set_verify(ctx,SSL_VERIFY_PEER,NULL);
        SSL_CTX_set_verify_depth(ctx,1);

  	/* ----------------------------------------------------------------- */
  	/* Set up a TCP socket */
 
  	sock = socket (PF_INET, SOCK_STREAM, IPPROTO_TCP);       
	RETURN_ERR(sock, "socket");

  	memset (&server_addr, '\0', sizeof(server_addr));
  	server_addr.sin_family      = AF_INET;
	server_addr.sin_port        = htons(s_port);          /* Server Port number */
  	server_addr.sin_addr.s_addr = inet_addr(s_ipaddr);   /* Server IP */

	/* Establish a TCP/IP connection to the SSL client */
  	err = connect(sock, (struct sockaddr*) &server_addr, sizeof(server_addr)); 
	RETURN_ERR(err, "connect");

  	/* ----------------------------------------------- */
  	/* A SSL structure is created */
  	ssl = SSL_new (ctx);
	RETURN_NULL(ssl);

	/* Use a socket BIO between the socket and SSL structure */
	/* Create a socket BIO */
	sbio = BIO_new_socket(sock, BIO_NOCLOSE);

	/* Assign the socket BIO to the SSL structure*/
	SSL_set_bio(ssl, sbio, sbio);

	/* Perform SSL Handshake on the SSL client */
	err = SSL_connect(ssl);
	RETURN_SSL(err);

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

  	/* Get the server's certificate (optional) */
  	server_cert = SSL_get_peer_certificate (ssl);       
	
	if (server_cert != NULL)
        {
		printf ("Server certificate:\n");

		str = X509_NAME_oneline(X509_get_subject_name(server_cert),0,0);
		RETURN_NULL(str);
		printf ("\t subject: %s\n", str);
		free (str);

		str = X509_NAME_oneline(X509_get_issuer_name(server_cert),0,0);
		RETURN_NULL(str);
		printf ("\t issuer: %s\n", str);
		free(str);

		X509_free (server_cert);
	}
        else
                printf("The SSL server does not have certificate.\n");


  	/*--------------- DATA EXCHANGE - send message and receive reply. ---------------*/

	/* Send data to the SSL server */
  	err = SSL_write(ssl, hello, strlen(hello));  
	RETURN_SSL(err);

	/* 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);

        /*--------------- SSL closure ---------------*/
        /* Shutdown this side of the SSL 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);
}