state_machine.c

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/* ====================================================================
 * Copyright (c) 2000 The OpenSSL Project.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer. 
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. All advertising materials mentioning features or use of this
 *    software must display the following acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
 *
 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For written permission, please contact
 *    [email protected].
 *
 * 5. Products derived from this software may not be called "OpenSSL"
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 *    acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
 *
 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
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 * ====================================================================
 *
 * This product includes cryptographic software written by Eric Young
 * ([email protected]).  This product includes software written by Tim
 * Hudson ([email protected]).
 *
 */

/*
 * Nuron, a leader in hardware encryption technology, generously
 * sponsored the development of this demo by Ben Laurie.
 *
 * See http://www.nuron.com/.
 */

/*
 * the aim of this demo is to provide a fully working state-machine
 * style SSL implementation, i.e. one where the main loop acquires
 * some data, then converts it from or to SSL by feeding it into the
 * SSL state machine. It then does any I/O required by the state machine
 * and loops.
 *
 * In order to keep things as simple as possible, this implementation
 * listens on a TCP socket, which it expects to get an SSL connection
 * on (for example, from s_client) and from then on writes decrypted
 * data to stdout and encrypts anything arriving on stdin. Verbose
 * commentary is written to stderr.
 *
 * This implementation acts as a server, but it can also be done for a client.  */

#include <openssl/ssl.h>
#include <assert.h>
#include <unistd.h>
#include <string.h>
#include <openssl/err.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>

/* die_unless is intended to work like assert, except that it happens
   always, even if NDEBUG is defined. Use assert as a stopgap. */

#define die_unless(x)   assert(x)

typedef struct
    {
    SSL_CTX *pCtx;
    BIO *pbioRead;
    BIO *pbioWrite;
    SSL *pSSL;
    } SSLStateMachine;

void SSLStateMachine_print_error(SSLStateMachine *pMachine,const char *szErr)
    {
    unsigned long l;

    fprintf(stderr,"%s\n",szErr);
    while((l=ERR_get_error()))
    {
    char buf[1024];

    ERR_error_string_n(l,buf,sizeof buf);
    fprintf(stderr,"Error %lx: %s\n",l,buf);
    }
    }

SSLStateMachine *SSLStateMachine_new(const char *szCertificateFile,
                     const char *szKeyFile)
    {
    SSLStateMachine *pMachine=malloc(sizeof *pMachine);
    int n;

    die_unless(pMachine);

    pMachine->pCtx=SSL_CTX_new(SSLv23_server_method());
    die_unless(pMachine->pCtx);

    n=SSL_CTX_use_certificate_file(pMachine->pCtx,szCertificateFile,
                   SSL_FILETYPE_PEM);
    die_unless(n > 0);

    n=SSL_CTX_use_PrivateKey_file(pMachine->pCtx,szKeyFile,SSL_FILETYPE_PEM);
    die_unless(n > 0);

    pMachine->pSSL=SSL_new(pMachine->pCtx);
    die_unless(pMachine->pSSL);

    pMachine->pbioRead=BIO_new(BIO_s_mem());

    pMachine->pbioWrite=BIO_new(BIO_s_mem());

    SSL_set_bio(pMachine->pSSL,pMachine->pbioRead,pMachine->pbioWrite);

    SSL_set_accept_state(pMachine->pSSL);

    return pMachine;
    }

void SSLStateMachine_read_inject(SSLStateMachine *pMachine,
                 const unsigned char *aucBuf,int nBuf)
    {
    int n=BIO_write(pMachine->pbioRead,aucBuf,nBuf);
    /* If it turns out this assert fails, then buffer the data here
     * and just feed it in in churn instead. Seems to me that it
     * should be guaranteed to succeed, though.
     */
    assert(n == nBuf);
    fprintf(stderr,"%d bytes of encrypted data fed to state machine\n",n);
    }

int SSLStateMachine_read_extract(SSLStateMachine *pMachine,
                 unsigned char *aucBuf,int nBuf)
    {
    int n;

    if(!SSL_is_init_finished(pMachine->pSSL))
    {
    fprintf(stderr,"Doing SSL_accept\n");
    n=SSL_accept(pMachine->pSSL);
    if(n == 0)
        fprintf(stderr,"SSL_accept returned zero\n");
    if(n < 0)
        {
        int err;

        if((err=SSL_get_error(pMachine->pSSL,n)) == SSL_ERROR_WANT_READ)
        {
        fprintf(stderr,"SSL_accept wants more data\n");
        return 0;
        }

        SSLStateMachine_print_error(pMachine,"SSL_accept error");
        exit(7);
        }
    return 0;
    }

    n=SSL_read(pMachine->pSSL,aucBuf,nBuf);
    if(n < 0)
    {
    int err=SSL_get_error(pMachine->pSSL,n);

    if(err == SSL_ERROR_WANT_READ)
        {
        fprintf(stderr,"SSL_read wants more data\n");
        return 0;
        }

    SSLStateMachine_print_error(pMachine,"SSL_read error");
    exit(8);
    }

    fprintf(stderr,"%d bytes of decrypted data read from state machine\n",n);
    return n;
    }

int SSLStateMachine_write_can_extract(SSLStateMachine *pMachine)
    {
    int n=BIO_pending(pMachine->pbioWrite);
    if(n)
    fprintf(stderr,"There is encrypted data available to write\n");
    else
    fprintf(stderr,"There is no encrypted data available to write\n");

    return n;
    }

int SSLStateMachine_write_extract(SSLStateMachine *pMachine,
                  unsigned char *aucBuf,int nBuf)
    {
    int n;

    n=BIO_read(pMachine->pbioWrite,aucBuf,nBuf);
    fprintf(stderr,"%d bytes of encrypted data read from state machine\n",n);
    return n;
    }

void SSLStateMachine_write_inject(SSLStateMachine *pMachine,
                  const unsigned char *aucBuf,int nBuf)
    {
    int n=SSL_write(pMachine->pSSL,aucBuf,nBuf);
    /* If it turns out this assert fails, then buffer the data here
     * and just feed it in in churn instead. Seems to me that it
     * should be guaranteed to succeed, though.
     */
    assert(n == nBuf);
    fprintf(stderr,"%d bytes of unencrypted data fed to state machine\n",n);
    }

int OpenSocket(int nPort)
    {
    int nSocket;
    struct sockaddr_in saServer;
    struct sockaddr_in saClient;
    int one=1;
    int nSize;
    int nFD;
    int nLen;

    nSocket=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);
    if(nSocket < 0)
    {
    perror("socket");
    exit(1);
    }

    if(setsockopt(nSocket,SOL_SOCKET,SO_REUSEADDR,(char *)&one,sizeof one) < 0)
    {
    perror("setsockopt");
        exit(2);
    }

    memset(&saServer,0,sizeof saServer);
    saServer.sin_family=AF_INET;
    saServer.sin_port=htons(nPort);
    nSize=sizeof saServer;
    if(bind(nSocket,(struct sockaddr *)&saServer,nSize) < 0)
    {
    perror("bind");
    exit(3);
    }

    if(listen(nSocket,512) < 0)
    {
    perror("listen");
    exit(4);
    }

    nLen=sizeof saClient;
    nFD=accept(nSocket,(struct sockaddr *)&saClient,&nLen);
    if(nFD < 0)
    {
    perror("accept");
    exit(5);
    }

    fprintf(stderr,"Incoming accepted on port %d\n",nPort);

    return nFD;
    }

int main(int argc,char **argv)
    {
    SSLStateMachine *pMachine;
    int nPort;
    int nFD;
    const char *szCertificateFile;
    const char *szKeyFile;
    char rbuf[1];
    int nrbuf=0;

    if(argc != 4)
    {
    fprintf(stderr,"%s <port> <certificate file> <key file>\n",argv[0]);
    exit(6);
    }

    nPort=atoi(argv[1]);
    szCertificateFile=argv[2];
    szKeyFile=argv[3];

    SSL_library_init();
    OpenSSL_add_ssl_algorithms();
    SSL_load_error_strings();
    ERR_load_crypto_strings();

    nFD=OpenSocket(nPort);

    pMachine=SSLStateMachine_new(szCertificateFile,szKeyFile);

    for( ; ; )
    {
    fd_set rfds,wfds;
    unsigned char buf[1024];
    int n;

    FD_ZERO(&rfds);
    FD_ZERO(&wfds);

    /* Select socket for input */
    FD_SET(nFD,&rfds);

    /* check whether there's decrypted data */
    if(!nrbuf)
        nrbuf=SSLStateMachine_read_extract(pMachine,rbuf,1);

    /* if there's decrypted data, check whether we can write it */
    if(nrbuf)
        FD_SET(1,&wfds);

    /* Select socket for output */
    if(SSLStateMachine_write_can_extract(pMachine))
        FD_SET(nFD,&wfds);

    /* Select stdin for input */
    FD_SET(0,&rfds);

    /* Wait for something to do something */
    n=select(nFD+1,&rfds,&wfds,NULL,NULL);
    assert(n > 0);

    /* Socket is ready for input */
    if(FD_ISSET(nFD,&rfds))
        {
        n=read(nFD,buf,sizeof buf);
        if(n == 0)
        {
        fprintf(stderr,"Got EOF on socket\n");
        exit(0);
        }
        assert(n > 0);

        SSLStateMachine_read_inject(pMachine,buf,n);
        }

    /* stdout is ready for output (and hence we have some to send it) */
    if(FD_ISSET(1,&wfds))
        {
        assert(nrbuf == 1);
        buf[0]=rbuf[0];
        nrbuf=0;

        n=SSLStateMachine_read_extract(pMachine,buf+1,sizeof buf-1);
        if(n < 0)
        {
        SSLStateMachine_print_error(pMachine,"read extract failed");
        break;
        }
        assert(n >= 0);
        ++n;
        if(n > 0) /* FIXME: has to be true now */
        {
        int w;
        
        w=write(1,buf,n);
        /* FIXME: we should push back any unwritten data */
        assert(w == n);
        }
        }

    /* Socket is ready for output (and therefore we have output to send) */
    if(FD_ISSET(nFD,&wfds))
        {
        int w;

        n=SSLStateMachine_write_extract(pMachine,buf,sizeof buf);
        assert(n > 0);

        w=write(nFD,buf,n);
        /* FIXME: we should push back any unwritten data */
        assert(w == n);
        }

    /* Stdin is ready for input */
    if(FD_ISSET(0,&rfds))
        {
        n=read(0,buf,sizeof buf);
        if(n == 0)
        {
        fprintf(stderr,"Got EOF on stdin\n");
        exit(0);
        }
        assert(n > 0);

        SSLStateMachine_write_inject(pMachine,buf,n);
        }
    }
    /* not reached */
    return 0;
    }