ssl.c

SSL加密库源码

/*
 *   stunnel       Universal SSL tunnel
 *   Copyright (c) 1998-2004 Michal Trojnara <[e-mail]>
 *                 All Rights Reserved
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 *   In addition, as a special exception, Michal Trojnara gives
 *   permission to link the code of this program with the OpenSSL
 *   library (or with modified versions of OpenSSL that use the same
 *   license as OpenSSL), and distribute linked combinations including
 *   the two.  You must obey the GNU General Public License in all
 *   respects for all of the code used other than OpenSSL.  If you modify
 *   this file, you may extend this exception to your version of the
 *   file, but you are not obligated to do so.  If you do not wish to
 *   do so, delete this exception statement from your version.
 */
#ifdef __vms
#include <starlet.h>
#endif /* __vms */

#ifndef NO_RSA

/* Cache temporary keys up to 2048 bits */
#define KEY_CACHE_LENGTH 2049

/* Cache temporary keys up to 1 hour */
#define KEY_CACHE_TIME 3600

#endif /* NO_RSA */

#include "common.h"
#include "prototypes.h"

    /* SSL functions */
static int init_dh(void);
static int init_prng(void);
static int prng_seeded(int);
static int add_rand_file(char *);
#ifndef NO_RSA
static RSA *tmp_rsa_cb(SSL *, int, int);
static RSA *make_temp_key(int);
#endif /* NO_RSA */
static void verify_init(void);
static int verify_callback(int, X509_STORE_CTX *);
static int crl_callback(X509_STORE_CTX *);
#if SSLEAY_VERSION_NUMBER >= 0x00907000L
static void info_callback(const SSL *, int, int);
#else
static void info_callback(SSL *, int, int);
#endif
static void print_stats(void);
static void sslerror_stack(void);

SSL_CTX *ctx; /* global SSL context */
static X509_STORE *revocation_store=NULL;

void context_init(void) { /* init SSL */
    int i;

#if SSLEAY_VERSION_NUMBER >= 0x00907000L
    /* Load all bundled ENGINEs into memory and make them visible */
    ENGINE_load_builtin_engines();
    /* Register all of them for every algorithm they collectively implement */
    ENGINE_register_all_complete();
#endif
    if(!init_prng())
        log(LOG_INFO, "PRNG seeded successfully");
    SSLeay_add_ssl_algorithms();
    SSL_load_error_strings();
    if(options.option.client) {
        ctx=SSL_CTX_new(SSLv3_client_method());
    } else { /* Server mode */
        ctx=SSL_CTX_new(SSLv23_server_method());
#ifndef NO_RSA
        SSL_CTX_set_tmp_rsa_callback(ctx, tmp_rsa_cb);
#endif /* NO_RSA */
        if(init_dh())
            log(LOG_WARNING, "Diffie-Hellman initialization failed");
    }
    if(options.ssl_options) {
        log(LOG_DEBUG, "Configuration SSL options: 0x%08lX",
            options.ssl_options);
        log(LOG_DEBUG, "SSL options set: 0x%08lX", 
            SSL_CTX_set_options(ctx, options.ssl_options));
    }
#if SSLEAY_VERSION_NUMBER >= 0x00906000L
    SSL_CTX_set_mode(ctx,
        SSL_MODE_ENABLE_PARTIAL_WRITE|SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER);
#endif /* OpenSSL-0.9.6 */

    SSL_CTX_set_session_cache_mode(ctx, SSL_SESS_CACHE_BOTH);
    SSL_CTX_set_timeout(ctx, options.session_timeout);
    if(options.option.cert) {
        if(!SSL_CTX_use_certificate_chain_file(ctx, options.cert)) {
            log(LOG_ERR, "Error reading certificate file: %s", options.cert);
            sslerror("SSL_CTX_use_certificate_chain_file");
            exit(1);
        }
        log(LOG_DEBUG, "Certificate: %s", options.cert);
        log(LOG_DEBUG, "Key file: %s", options.key);
#ifdef USE_WIN32
        SSL_CTX_set_default_passwd_cb(ctx, pem_passwd_cb);
#endif
        for(i=0; i<3; i++) {
#ifdef NO_RSA
            if(SSL_CTX_use_PrivateKey_file(ctx, options.key,
                    SSL_FILETYPE_PEM))
#else /* NO_RSA */
            if(SSL_CTX_use_RSAPrivateKey_file(ctx, options.key,
                    SSL_FILETYPE_PEM))
#endif /* NO_RSA */
                break;
            if(i<2 && ERR_GET_REASON(ERR_peek_error())==EVP_R_BAD_DECRYPT) {
                sslerror_stack(); /* dump the error stack */
                log(LOG_ERR, "Wrong pass phrase: retrying");
                continue;
            }
#ifdef NO_RSA
            sslerror("SSL_CTX_use_PrivateKey_file");
#else /* NO_RSA */
            sslerror("SSL_CTX_use_RSAPrivateKey_file");
#endif /* NO_RSA */
            exit(1);
        }
        if(!SSL_CTX_check_private_key(ctx)) {
            sslerror("Private key does not match the certificate");
            exit(1);
        }
    }

    verify_init(); /* Initialize certificate verification */

    SSL_CTX_set_info_callback(ctx, info_callback);

    if(options.cipher_list) {
        if (!SSL_CTX_set_cipher_list(ctx, options.cipher_list)) {
            sslerror("SSL_CTX_set_cipher_list");
            exit(1);
        }
    }
}

void context_free(void) { /* free SSL */
    SSL_CTX_free(ctx);
}

static int init_prng(void) {
    int totbytes=0;
    char filename[STRLEN];
    int bytes;
    
    bytes=0; /* avoid warning if #ifdef'd out for windows */

    filename[0]='\0';

    /* If they specify a rand file on the command line we
       assume that they really do want it, so try it first */
    if(options.rand_file) {
        totbytes+=add_rand_file(options.rand_file);
        if(prng_seeded(totbytes))
            return 0;
    }

    /* try the $RANDFILE or $HOME/.rnd files */
    RAND_file_name(filename, STRLEN);
    if(filename[0]) {
        filename[STRLEN-1]='\0';        /* just in case */
        totbytes+=add_rand_file(filename);
        if(prng_seeded(totbytes))
            return 0;
    }

#ifdef RANDOM_FILE
    totbytes += add_rand_file( RANDOM_FILE );
    if(prng_seeded(totbytes))
        return 0;
#endif

#ifdef USE_WIN32
    RAND_screen();
    if(prng_seeded(totbytes)) {
        log(LOG_DEBUG, "Seeded PRNG with RAND_screen");
        return 0;
    }
    log(LOG_DEBUG, "RAND_screen failed to sufficiently seed PRNG");
#else

#if SSLEAY_VERSION_NUMBER >= 0x0090581fL
    if(options.egd_sock) {
        if((bytes=RAND_egd(options.egd_sock))==-1) {
            log(LOG_WARNING, "EGD Socket %s failed", options.egd_sock);
            bytes=0;
        } else {
            totbytes += bytes;
            log(LOG_DEBUG, "Snagged %d random bytes from EGD Socket %s",
                bytes, options.egd_sock);
            return 0; /* OpenSSL always gets what it needs or fails,
                         so no need to check if seeded sufficiently */
        }
    }
#ifdef EGD_SOCKET
    if((bytes=RAND_egd(EGD_SOCKET))==-1) {
        log(LOG_WARNING, "EGD Socket %s failed", EGD_SOCKET);
    } else {
        totbytes += bytes;
        log(LOG_DEBUG, "Snagged %d random bytes from EGD Socket %s",
            bytes, EGD_SOCKET);
        return 0;
    }
#endif /* EGD_SOCKET */

#endif /* OpenSSL-0.9.5a */
#endif /* USE_WIN32 */

    /* Try the good-old default /dev/urandom, if available  */
    totbytes+=add_rand_file( "/dev/urandom" );
    if(prng_seeded(totbytes))
        return 0;

    /* Random file specified during configure */
    log(LOG_INFO, "PRNG seeded with %d bytes total", totbytes);
    log(LOG_WARNING, "PRNG may not have been seeded with enough random bytes");
    return -1; /* FAILED */
}

static int init_dh(void) {
#ifdef USE_DH
    FILE *fp;
    DH *dh;
    BIO *bio;

    fp=fopen(options.cert, "r");
    if(!fp) {
#ifdef USE_WIN32
        /* Win32 doesn't seem to set errno in fopen() */
        log(LOG_ERR, "Failed to open %s", options.cert);
#else
        ioerror(options.cert);
#endif
        return -1; /* FAILED */
    }
    bio=BIO_new_fp(fp, BIO_CLOSE|BIO_FP_TEXT);
    if(!bio) {
        log(LOG_ERR, "BIO_new_fp failed");
        return -1; /* FAILED */
    }
    if((dh=PEM_read_bio_DHparams(bio, NULL, NULL
#if SSLEAY_VERSION_NUMBER >= 0x00904000L
            , NULL
#endif
            ))) {
        BIO_free(bio);
        log(LOG_DEBUG, "Using Diffie-Hellman parameters from %s",
            options.cert);
    } else { /* Failed to load DH parameters from file */
        BIO_free(bio);
        log(LOG_NOTICE, "Could not load DH parameters from %s", options.cert);
        return -1; /* FAILED */
    }
    SSL_CTX_set_tmp_dh(ctx, dh);
    log(LOG_INFO, "Diffie-Hellman initialized with %d bit key",
        8*DH_size(dh));
    DH_free(dh);
#endif /* USE_DH */
    return 0; /* OK */
}

/* shortcut to determine if sufficient entropy for PRNG is present */
static int prng_seeded(int bytes) {
#if SSLEAY_VERSION_NUMBER >= 0x0090581fL
    if(RAND_status()){
        log(LOG_DEBUG, "RAND_status claims sufficient entropy for the PRNG");
        return 1;
    }
#else
    if(bytes>=options.random_bytes) {
        log(LOG_INFO, "Sufficient entropy in PRNG assumed (>= %d)", options.random_bytes);
        return 1;
    }
#endif
    return 0;        /* assume we don't have enough */
}

static int add_rand_file(char *filename) {
    int readbytes;
    int writebytes;
    struct stat sb;

    if(stat(filename, &sb))
        return 0;
    if((readbytes=RAND_load_file(filename, options.random_bytes)))
        log(LOG_DEBUG, "Snagged %d random bytes from %s", readbytes, filename);
    else
        log(LOG_INFO, "Unable to retrieve any random data from %s", filename);
    /* Write new random data for future seeding if it's a regular file */
    if(options.option.rand_write && (sb.st_mode & S_IFREG)){
        writebytes = RAND_write_file(filename);
        if(writebytes==-1)
            log(LOG_WARNING, "Failed to write strong random data to %s - "
                "may be a permissions or seeding problem", filename);
        else
            log(LOG_DEBUG, "Wrote %d new random bytes to %s", writebytes, filename);
    }
    return readbytes;
}

#ifndef NO_RSA

static RSA *tmp_rsa_cb(SSL *s, int export, int keylen) {
    static int initialized=0;
    static struct keytabstruct {
        RSA *key;
        time_t timeout;
    } keytable[KEY_CACHE_LENGTH];
    static RSA *longkey=NULL;
    static int longlen=0;
    static time_t longtime=0;
    RSA *oldkey, *retval;
    time_t now;
    int i;

    enter_critical_section(CRIT_KEYGEN); /* Only one make_temp_key() at a time */
    if(!initialized) {
        for(i=0; i<KEY_CACHE_LENGTH; i++) {
            keytable[i].key=NULL;
            keytable[i].timeout=0;
        }
        initialized=1;
    }
    time(&now);
    if(keylen<KEY_CACHE_LENGTH) {
        if(keytable[keylen].timeout<now) {