ssl_engine_kernel.c

Apache HTTP Server 是一个功能强大的灵活的与HTTP/1.1相兼容的web服务器.这里给出的是Apache HTTP服务器的源码。

/* Copyright 2001-2005 The Apache Software Foundation or its licensors, as
 * applicable.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*                      _             _
 *  _ __ ___   ___   __| |    ___ ___| |  mod_ssl
 * | '_ ` _ \ / _ \ / _` |   / __/ __| |  Apache Interface to OpenSSL
 * | | | | | | (_) | (_| |   \__ \__ \ |
 * |_| |_| |_|\___/ \__,_|___|___/___/_|
 *                      |_____|
 *  ssl_engine_kernel.c
 *  The SSL engine kernel
 */
                             /* ``It took me fifteen years to discover
                                  I had no talent for programming, but
                                  I couldn't give it up because by that
                                  time I was too famous.''
                                            -- Unknown                */
#include "mod_ssl.h"

/*
 *  Post Read Request Handler
 */
int ssl_hook_ReadReq(request_rec *r)
{
    SSLConnRec *sslconn = myConnConfig(r->connection);
    SSL *ssl;

    if (!sslconn) {
        return DECLINED;
    }

    if (sslconn->non_ssl_request) {
        const char *errmsg;
        char *thisurl;
        char *thisport = "";
        int port = ap_get_server_port(r);

        if (!ap_is_default_port(port, r)) {
            thisport = apr_psprintf(r->pool, ":%u", port);
        }

        thisurl = ap_escape_html(r->pool,
                                 apr_psprintf(r->pool, "https://%s%s/",
                                              ap_get_server_name(r),
                                              thisport));

        errmsg = apr_psprintf(r->pool,
                              "Reason: You're speaking plain HTTP "
                              "to an SSL-enabled server port.<br />\n"
                              "Instead use the HTTPS scheme to access "
                              "this URL, please.<br />\n"
                              "<blockquote>Hint: "
                              "<a href=\"%s\"><b>%s</b></a></blockquote>",
                              thisurl, thisurl);

        apr_table_setn(r->notes, "error-notes", errmsg);

        /* Now that we have caught this error, forget it. we are done
         * with using SSL on this request.
         */
        sslconn->non_ssl_request = 0;
        

        return HTTP_BAD_REQUEST;
    }

    /*
     * Get the SSL connection structure and perform the
     * delayed interlinking from SSL back to request_rec
     */
    if ((ssl = sslconn->ssl)) {
        SSL_set_app_data2(ssl, r);
    }

    return DECLINED;
}

/*
 * Move SetEnvIf information from request_rec to conn_rec/BUFF
 * to allow the close connection handler to use them.
 */

static void ssl_configure_env(request_rec *r, SSLConnRec *sslconn)
{
    int i;
    const apr_array_header_t *arr = apr_table_elts(r->subprocess_env);
    const apr_table_entry_t *elts = (const apr_table_entry_t *)arr->elts;

    sslconn->shutdown_type = SSL_SHUTDOWN_TYPE_STANDARD;

    for (i = 0; i < arr->nelts; i++) {
        const char *key = elts[i].key;

        switch (*key) {
          case 's':
            /* being case-sensitive here.
             * and not checking for the -shutdown since these are the only
             * SetEnvIf "flags" we support
             */
            if (!strncmp(key+1, "sl-", 3)) {
                key += 4;
                if (!strncmp(key, "unclean", 7)) {
                    sslconn->shutdown_type = SSL_SHUTDOWN_TYPE_UNCLEAN;
                }
                else if (!strncmp(key, "accurate", 8)) {
                    sslconn->shutdown_type = SSL_SHUTDOWN_TYPE_ACCURATE;
                }
                return; /* should only ever be one ssl-*-shutdown */
            }
            break;
        }
    }
}

/*
 *  URL Translation Handler
 */
int ssl_hook_Translate(request_rec *r)
{
    SSLConnRec *sslconn = myConnConfig(r->connection);

    if (!(sslconn && sslconn->ssl)) {
        return DECLINED;
    }

    /*
     * Log information about incoming HTTPS requests
     */
    if (r->server->loglevel >= APLOG_INFO && ap_is_initial_req(r)) {
        ap_log_error(APLOG_MARK, APLOG_INFO, 0, r->server,
                     "%s HTTPS request received for child %ld (server %s)",
                     (r->connection->keepalives <= 0 ?
                     "Initial (No.1)" :
                     apr_psprintf(r->pool, "Subsequent (No.%d)",
                                  r->connection->keepalives+1)),
                     r->connection->id,
                     ssl_util_vhostid(r->pool, r->server));
    }

    /* SetEnvIf ssl-*-shutdown flags can only be per-server,
     * so they won't change across keepalive requests
     */
    if (sslconn->shutdown_type == SSL_SHUTDOWN_TYPE_UNSET) {
        ssl_configure_env(r, sslconn);
    }

    return DECLINED;
}

/*
 *  Access Handler
 */
int ssl_hook_Access(request_rec *r)
{
    SSLDirConfigRec *dc = myDirConfig(r);
    SSLSrvConfigRec *sc = mySrvConfig(r->server);
    SSLConnRec *sslconn = myConnConfig(r->connection);
    SSL *ssl            = sslconn ? sslconn->ssl : NULL;
    SSL_CTX *ctx = NULL;
    apr_array_header_t *requires;
    ssl_require_t *ssl_requires;
    char *cp;
    int ok, i;
    BOOL renegotiate = FALSE, renegotiate_quick = FALSE;
    X509 *cert;
    X509 *peercert;
    X509_STORE *cert_store = NULL;
    X509_STORE_CTX cert_store_ctx;
    STACK_OF(SSL_CIPHER) *cipher_list_old = NULL, *cipher_list = NULL;
    SSL_CIPHER *cipher = NULL;
    int depth, verify_old, verify, n;

    if (ssl) {
        ctx = SSL_get_SSL_CTX(ssl);
    }

    /*
     * Support for SSLRequireSSL directive
     */
    if (dc->bSSLRequired && !ssl) {
        ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, 
                      "access to %s failed, reason: %s",
                      r->filename, "SSL connection required");

        /* remember forbidden access for strict require option */
        apr_table_setn(r->notes, "ssl-access-forbidden", "1");

        return HTTP_FORBIDDEN;
    }

    /*
     * Check to see if SSL protocol is on
     */
    if (!(sc->enabled || ssl)) {
        return DECLINED;
    }
    /*
     * Support for per-directory reconfigured SSL connection parameters.
     *
     * This is implemented by forcing an SSL renegotiation with the
     * reconfigured parameter suite. But Apache's internal API processing
     * makes our life very hard here, because when internal sub-requests occur
     * we nevertheless should avoid multiple unnecessary SSL handshakes (they
     * require extra network I/O and especially time to perform). 
     * 
     * But the optimization for filtering out the unnecessary handshakes isn't
     * obvious and trivial.  Especially because while Apache is in its
     * sub-request processing the client could force additional handshakes,
     * too. And these take place perhaps without our notice. So the only
     * possibility is to explicitly _ask_ OpenSSL whether the renegotiation
     * has to be performed or not. It has to performed when some parameters
     * which were previously known (by us) are not those we've now
     * reconfigured (as known by OpenSSL) or (in optimized way) at least when
     * the reconfigured parameter suite is stronger (more restrictions) than
     * the currently active one.
     */

    /*
     * Override of SSLCipherSuite
     *
     * We provide two options here:
     *
     * o The paranoid and default approach where we force a renegotiation when
     *   the cipher suite changed in _any_ way (which is straight-forward but
     *   often forces renegotiations too often and is perhaps not what the
     *   user actually wanted).
     *
     * o The optimized and still secure way where we force a renegotiation
     *   only if the currently active cipher is no longer contained in the
     *   reconfigured/new cipher suite. Any other changes are not important
     *   because it's the servers choice to select a cipher from the ones the
     *   client supports. So as long as the current cipher is still in the new
     *   cipher suite we're happy. Because we can assume we would have
     *   selected it again even when other (better) ciphers exists now in the
     *   new cipher suite. This approach is fine because the user explicitly
     *   has to enable this via ``SSLOptions +OptRenegotiate''. So we do no
     *   implicit optimizations.
     */
    if (dc->szCipherSuite) {
        /* remember old state */

        if (dc->nOptions & SSL_OPT_OPTRENEGOTIATE) {
            cipher = SSL_get_current_cipher(ssl);
        }
        else {
            cipher_list_old = (STACK_OF(SSL_CIPHER) *)SSL_get_ciphers(ssl);

            if (cipher_list_old) {
                cipher_list_old = sk_SSL_CIPHER_dup(cipher_list_old);
            }
        }

        /* configure new state */
        if (!modssl_set_cipher_list(ssl, dc->szCipherSuite)) {
            ap_log_error(APLOG_MARK, APLOG_WARNING, 0,
                         r->server,
                         "Unable to reconfigure (per-directory) "
                         "permitted SSL ciphers");
            ssl_log_ssl_error(APLOG_MARK, APLOG_ERR, r->server);

            if (cipher_list_old) {
                sk_SSL_CIPHER_free(cipher_list_old);
            }

            return HTTP_FORBIDDEN;
        }

        /* determine whether a renegotiation has to be forced */
        cipher_list = (STACK_OF(SSL_CIPHER) *)SSL_get_ciphers(ssl);

        if (dc->nOptions & SSL_OPT_OPTRENEGOTIATE) {
            /* optimized way */
            if ((!cipher && cipher_list) ||
                (cipher && !cipher_list))
            {
                renegotiate = TRUE;
            }
            else if (cipher && cipher_list &&
                     (sk_SSL_CIPHER_find(cipher_list, cipher) < 0))
            {
                renegotiate = TRUE;
            }
        }
        else {
            /* paranoid way */
            if ((!cipher_list_old && cipher_list) ||
                (cipher_list_old && !cipher_list))
            {
                renegotiate = TRUE;
            }
            else if (cipher_list_old && cipher_list) {
                for (n = 0;
                     !renegotiate && (n < sk_SSL_CIPHER_num(cipher_list));
                     n++)
                {
                    SSL_CIPHER *value = sk_SSL_CIPHER_value(cipher_list, n);

                    if (sk_SSL_CIPHER_find(cipher_list_old, value) < 0) {
                        renegotiate = TRUE;
                    }
                }

                for (n = 0;
                     !renegotiate && (n < sk_SSL_CIPHER_num(cipher_list_old));
                     n++)
                {
                    SSL_CIPHER *value = sk_SSL_CIPHER_value(cipher_list_old, n);

                    if (sk_SSL_CIPHER_find(cipher_list, value) < 0) {
                        renegotiate = TRUE;
                    }
                }
            }
        }

        /* cleanup */
        if (cipher_list_old) {
            sk_SSL_CIPHER_free(cipher_list_old);
        }

        /* tracing */
        if (renegotiate) {
            ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
                         "Reconfigured cipher suite will force renegotiation");
        }
    }

    /*
     * override of SSLVerifyDepth
     *
     * The depth checks are handled by us manually inside the verify callback
     * function and not by OpenSSL internally (and our function is aware of
     * both the per-server and per-directory contexts). So we cannot ask
     * OpenSSL about the currently verify depth. Instead we remember it in our
     * ap_ctx attached to the SSL* of OpenSSL.  We've to force the
     * renegotiation if the reconfigured/new verify depth is less than the
     * currently active/remembered verify depth (because this means more
     * restriction on the certificate chain).
     */
    if (dc->nVerifyDepth != UNSET) {
        /* XXX: doesnt look like sslconn->verify_depth is actually used */
        if (!(n = sslconn->verify_depth)) {
            sslconn->verify_depth = n = sc->server->auth.verify_depth;
        }

        /* determine whether a renegotiation has to be forced */
        if (dc->nVerifyDepth < n) {
            renegotiate = TRUE;
            ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
                         "Reduced client verification depth will force "
                         "renegotiation");
        }
    }