ssl_engine_io.c

/* Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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_io.c
 *  I/O Functions
 */
                             /* ``MY HACK: This universe.
                                  Just one little problem:
                                  core keeps dumping.''
                                            -- Unknown    */
#include "ssl_private.h"
#include "mod_ssl.h"
#include "mod_ssl_openssl.h"
#include "apr_date.h"

APR_IMPLEMENT_OPTIONAL_HOOK_RUN_ALL(ssl, SSL, int, proxy_post_handshake,
                                    (conn_rec *c,SSL *ssl),
                                    (c,ssl),OK,DECLINED);

/*  _________________________________________________________________
**
**  I/O Hooks
**  _________________________________________________________________
*/

/* This file is designed to be the bridge between OpenSSL and httpd.
 * However, we really don't expect anyone (let alone ourselves) to
 * remember what is in this file.  So, first, a quick overview.
 *
 * In this file, you will find:
 * - ssl_io_filter_input    (Apache input filter)
 * - ssl_io_filter_output   (Apache output filter)
 *
 * - bio_filter_in_*        (OpenSSL input filter)
 * - bio_filter_out_*       (OpenSSL output filter)
 *
 * The input chain is roughly:
 *
 * ssl_io_filter_input->ssl_io_input_read->SSL_read->...
 * ...->bio_filter_in_read->ap_get_brigade/next-httpd-filter
 *
 * In mortal terminology, we do the following:
 * - Receive a request for data to the SSL input filter
 * - Call a helper function once we know we should perform a read
 * - Call OpenSSL's SSL_read()
 * - SSL_read() will then call bio_filter_in_read
 * - bio_filter_in_read will then try to fetch data from the next httpd filter
 * - bio_filter_in_read will flatten that data and return it to SSL_read
 * - SSL_read will then decrypt the data
 * - ssl_io_input_read will then receive decrypted data as a char* and
 *   ensure that there were no read errors
 * - The char* is placed in a brigade and returned
 *
 * Since connection-level input filters in httpd need to be able to
 * handle AP_MODE_GETLINE calls (namely identifying LF-terminated strings),
 * ssl_io_input_getline which will handle this special case.
 *
 * Due to AP_MODE_GETLINE and AP_MODE_SPECULATIVE, we may sometimes have
 * 'leftover' decoded data which must be setaside for the next read.  That
 * is currently handled by the char_buffer_{read|write} functions.  So,
 * ssl_io_input_read may be able to fulfill reads without invoking
 * SSL_read().
 *
 * Note that the filter context of ssl_io_filter_input and bio_filter_in_*
 * are shared as bio_filter_in_ctx_t.
 *
 * Note that the filter is by choice limited to reading at most
 * AP_IOBUFSIZE (8192 bytes) per call.
 *
 */

/* this custom BIO allows us to hook SSL_write directly into
 * an apr_bucket_brigade and use transient buckets with the SSL
 * malloc-ed buffer, rather than copying into a mem BIO.
 * also allows us to pass the brigade as data is being written
 * rather than buffering up the entire response in the mem BIO.
 *
 * when SSL needs to flush (e.g. SSL_accept()), it will call BIO_flush()
 * which will trigger a call to bio_filter_out_ctrl() -> bio_filter_out_flush().
 * so we only need to flush the output ourselves if we receive an
 * EOS or FLUSH bucket. this was not possible with the mem BIO where we
 * had to flush all over the place not really knowing when it was required
 * to do so.
 */

typedef struct {
    SSL                *pssl;
    BIO                *pbioRead;
    BIO                *pbioWrite;
    ap_filter_t        *pInputFilter;
    ap_filter_t        *pOutputFilter;
    SSLConnRec         *config;
} ssl_filter_ctx_t;

typedef struct {
    ssl_filter_ctx_t *filter_ctx;
    conn_rec *c;
    apr_bucket_brigade *bb;    /* Brigade used as a buffer. */
    apr_status_t rc;
} bio_filter_out_ctx_t;

static bio_filter_out_ctx_t *bio_filter_out_ctx_new(ssl_filter_ctx_t *filter_ctx,
                                                    conn_rec *c)
{
    bio_filter_out_ctx_t *outctx = apr_palloc(c->pool, sizeof(*outctx));

    outctx->filter_ctx = filter_ctx;
    outctx->c = c;
    outctx->bb = apr_brigade_create(c->pool, c->bucket_alloc);

    return outctx;
}

/* Pass an output brigade down the filter stack; returns 1 on success
 * or -1 on failure. */
static int bio_filter_out_pass(bio_filter_out_ctx_t *outctx)
{
    AP_DEBUG_ASSERT(!APR_BRIGADE_EMPTY(outctx->bb));

    outctx->rc = ap_pass_brigade(outctx->filter_ctx->pOutputFilter->next,
                                 outctx->bb);
    /* Fail if the connection was reset: */
    if (outctx->rc == APR_SUCCESS && outctx->c->aborted) {
        outctx->rc = APR_ECONNRESET;
    }
    return (outctx->rc == APR_SUCCESS) ? 1 : -1;
}

/* Send a FLUSH bucket down the output filter stack; returns 1 on
 * success, -1 on failure. */
static int bio_filter_out_flush(BIO *bio)
{
    bio_filter_out_ctx_t *outctx = (bio_filter_out_ctx_t *)BIO_get_data(bio);
    apr_bucket *e;

    AP_DEBUG_ASSERT(APR_BRIGADE_EMPTY(outctx->bb));

    e = apr_bucket_flush_create(outctx->bb->bucket_alloc);
    APR_BRIGADE_INSERT_TAIL(outctx->bb, e);

    return bio_filter_out_pass(outctx);
}

static int bio_filter_create(BIO *bio)
{
    BIO_set_shutdown(bio, 1);
    BIO_set_init(bio, 1);
#if MODSSL_USE_OPENSSL_PRE_1_1_API
    /* No setter method for OpenSSL 1.1.0 available,
     * but I can't find any functional use of the
     * "num" field there either.
     */
    bio->num = -1;
#endif
    BIO_set_data(bio, NULL);

    return 1;
}

static int bio_filter_destroy(BIO *bio)
{
    if (bio == NULL) {
        return 0;
    }

    /* nothing to free here.
     * apache will destroy the bucket brigade for us
     */
    return 1;
}

static int bio_filter_out_read(BIO *bio, char *out, int outl)
{
    /* this is never called */
    return -1;
}

static int bio_filter_out_write(BIO *bio, const char *in, int inl)
{
    bio_filter_out_ctx_t *outctx = (bio_filter_out_ctx_t *)BIO_get_data(bio);
    apr_bucket *e;
    int need_flush;

    /* Abort early if the client has initiated a renegotiation. */
    if (outctx->filter_ctx->config->reneg_state == RENEG_ABORT) {
        outctx->rc = APR_ECONNABORTED;
        return -1;
    }

    /* when handshaking we'll have a small number of bytes.
     * max size SSL will pass us here is about 16k.
     * (16413 bytes to be exact)
     */
    BIO_clear_retry_flags(bio);

    /* Use a transient bucket for the output data - any downstream
     * filter must setaside if necessary. */
    e = apr_bucket_transient_create(in, inl, outctx->bb->bucket_alloc);
    APR_BRIGADE_INSERT_TAIL(outctx->bb, e);

    /* In theory, OpenSSL should flush as necessary, but it is known
     * not to do so correctly in some cases (< 0.9.8m; see PR 46952),
     * or on the proxy/client side (after ssl23_client_hello(), e.g.
     * ssl/proxy.t test suite).
     *
     * Historically, this flush call was performed only for an SSLv2
     * connection or for a proxy connection.  Calling _out_flush can
     * be expensive in cases where requests/responses are pipelined,
     * so limit the performance impact to handshake time.
     */
#if OPENSSL_VERSION_NUMBER < 0x0009080df
     need_flush = !SSL_is_init_finished(outctx->filter_ctx->pssl);
#else
     need_flush = SSL_in_connect_init(outctx->filter_ctx->pssl);
#endif
    if (need_flush) {
        e = apr_bucket_flush_create(outctx->bb->bucket_alloc);
        APR_BRIGADE_INSERT_TAIL(outctx->bb, e);
    }

    if (bio_filter_out_pass(outctx) < 0) {
        return -1;
    }

    return inl;
}

static long bio_filter_out_ctrl(BIO *bio, int cmd, long num, void *ptr)
{
    long ret = 1;
    bio_filter_out_ctx_t *outctx = (bio_filter_out_ctx_t *)BIO_get_data(bio);

    switch (cmd) {
    case BIO_CTRL_RESET:
    case BIO_CTRL_EOF:
    case BIO_C_SET_BUF_MEM_EOF_RETURN:
        ap_log_cerror(APLOG_MARK, APLOG_TRACE4, 0, outctx->c,
                      "output bio: unhandled control %d", cmd);
        ret = 0;
        break;
    case BIO_CTRL_WPENDING:
    case BIO_CTRL_PENDING:
    case BIO_CTRL_INFO:
        ret = 0;
        break;
    case BIO_CTRL_GET_CLOSE:
        ret = (long)BIO_get_shutdown(bio);
        break;
      case BIO_CTRL_SET_CLOSE:
        BIO_set_shutdown(bio, (int)num);
        break;
      case BIO_CTRL_FLUSH:
        ret = bio_filter_out_flush(bio);
        break;
      case BIO_CTRL_DUP:
        ret = 1;
        break;
        /* N/A */
      case BIO_C_SET_BUF_MEM:
      case BIO_C_GET_BUF_MEM_PTR:
        /* we don't care */
      case BIO_CTRL_PUSH:
      case BIO_CTRL_POP:
      default:
        ret = 0;
        break;
    }

    return ret;
}

static int bio_filter_out_gets(BIO *bio, char *buf, int size)
{
    /* this is never called */
    return -1;
}

static int bio_filter_out_puts(BIO *bio, const char *str)
{
    /* this is never called */
    return -1;
}

typedef struct {
    int length;
    char *value;
} char_buffer_t;

typedef struct {
    SSL *ssl;
    BIO *bio_out;
    ap_filter_t *f;
    apr_status_t rc;
    ap_input_mode_t mode;
    apr_read_type_e block;
    apr_bucket_brigade *bb;
    char_buffer_t cbuf;
    apr_pool_t *pool;
    char buffer[AP_IOBUFSIZE];
    ssl_filter_ctx_t *filter_ctx;
} bio_filter_in_ctx_t;

/*
 * this char_buffer api might seem silly, but we don't need to copy
 * any of this data and we need to remember the length.
 */

/* Copy up to INL bytes from the char_buffer BUFFER into IN.  Note
 * that due to the strange way this API is designed/used, the
 * char_buffer object is used to cache a segment of inctx->buffer, and
 * then this function called to copy (part of) that segment to the
 * beginning of inctx->buffer.  So the segments to copy cannot be
 * presumed to be non-overlapping, and memmove must be used. */
static int char_buffer_read(char_buffer_t *buffer, char *in, int inl)
{
    if (!buffer->length) {
        return 0;
    }

    if (buffer->length > inl) {
        /* we have enough to fill the caller's buffer */
        memmove(in, buffer->value, inl);
        buffer->value += inl;
        buffer->length -= inl;
    }
    else {
        /* swallow remainder of the buffer */
        memmove(in, buffer->value, buffer->length);
        inl = buffer->length;
        buffer->value = NULL;
        buffer->length = 0;
    }

    return inl;
}

static int char_buffer_write(char_buffer_t *buffer, char *in, int inl)
{
    buffer->value = in;
    buffer->length = inl;
    return inl;
}

/* This function will read from a brigade and discard the read buckets as it
 * proceeds.  It will read at most *len bytes.
 */
static apr_status_t brigade_consume(apr_bucket_brigade *bb,
                                    apr_read_type_e block,
                                    char *c, apr_size_t *len)
{
    apr_size_t actual = 0;
    apr_status_t status = APR_SUCCESS;

    while (!APR_BRIGADE_EMPTY(bb)) {
        apr_bucket *b = APR_BRIGADE_FIRST(bb);
        const char *str;
        apr_size_t str_len;
        apr_size_t consume;

        /* Justin points out this is an http-ism that might
         * not fit if brigade_consume is added to APR.  Perhaps
         * apr_bucket_read(eos_bucket) should return APR_EOF?
         * Then this becomes mainline instead of a one-off.
         */
        if (APR_BUCKET_IS_EOS(b)) {
            status = APR_EOF;
            break;
        }

        /* The reason I'm not offering brigade_consume yet
         * across to apr-util is that the following call
         * illustrates how borked that API really is.  For
         * this sort of case (caller provided buffer) it
         * would be much more trivial for apr_bucket_consume
         * to do all the work that follows, based on the
         * particular characteristics of the bucket we are
         * consuming here.
         */
        status = apr_bucket_read(b, &str, &str_len, block);

        if (status != APR_SUCCESS) {
            if (APR_STATUS_IS_EOF(status)) {
                /* This stream bucket was consumed */
                apr_bucket_delete(b);
                continue;
            }
            break;
        }

        if (str_len > 0) {
            /* Do not block once some data has been consumed */
            block = APR_NONBLOCK_READ;

            /* Assure we don't overflow. */
            consume = (str_len + actual > *len) ? *len - actual : str_len;

            memcpy(c, str, consume);

            c += consume;
            actual += consume;

            if (consume >= b->length) {
                /* This physical bucket was consumed */
                apr_bucket_delete(b);
            }
            else {
                /* Only part of this physical bucket was consumed */
                b->start += consume;
                b->length -= consume;
            }
        }
        else if (b->length == 0) {
            apr_bucket_delete(b);
        }

        /* This could probably be actual == *len, but be safe from stray
         * photons. */
        if (actual >= *len) {
            break;
        }
    }

    *len = actual;
    return status;
}

/*
 * this is the function called by SSL_read()
 */
static int bio_filter_in_read(BIO *bio, char *in, int inlen)
{
    apr_size_t inl = inlen;
    bio_filter_in_ctx_t *inctx = (bio_filter_in_ctx_t *)BIO_get_data(bio);
    apr_read_type_e block = inctx->block;

    inctx->rc = APR_SUCCESS;

    /* OpenSSL catches this case, so should we. */
    if (!in)
        return 0;

    /* Abort early if the client has initiated a renegotiation. */
    if (inctx->filter_ctx->config->reneg_state == RENEG_ABORT) {
        inctx->rc = APR_ECONNABORTED;
        return -1;
    }

    BIO_clear_retry_flags(bio);

    if (!inctx->bb) {
        inctx->rc = APR_EOF;
        return -1;
    }

    if (APR_BRIGADE_EMPTY(inctx->bb)) {

        inctx->rc = ap_get_brigade(inctx->f->next, inctx->bb,
                                   AP_MODE_READBYTES, block,
                                   inl);

        /* If the read returns EAGAIN or success with an empty
         * brigade, return an error after setting the retry flag;
         * SSL_read() will then return -1, and SSL_get_error() will
         * indicate SSL_ERROR_WANT_READ. */
        if (APR_STATUS_IS_EAGAIN(inctx->rc) || APR_STATUS_IS_EINTR(inctx->rc)
               || (inctx->rc == APR_SUCCESS && APR_BRIGADE_EMPTY(inctx->bb))) {
            BIO_set_retry_read(bio);
            return -1;
        }

        if (block == APR_BLOCK_READ 
            && APR_STATUS_IS_TIMEUP(inctx->rc)
            && APR_BRIGADE_EMPTY(inctx->bb)) {
            /* don't give up, just return the timeout */
            return -1;
        }
        if (inctx->rc != APR_SUCCESS) {
            /* Unexpected errors discard the brigade */
            apr_brigade_cleanup(inctx->bb);
            inctx->bb = NULL;
            return -1;
        }
    }

    inctx->rc = brigade_consume(inctx->bb, block, in, &inl);

    if (inctx->rc == APR_SUCCESS) {
        return (int)inl;
    }

    if (APR_STATUS_IS_EAGAIN(inctx->rc)
            || APR_STATUS_IS_EINTR(inctx->rc)) {
        BIO_set_retry_read(bio);
        return (int)inl;
    }

    /* Unexpected errors and APR_EOF clean out the brigade.
     * Subsequent calls will return APR_EOF.
     */
    apr_brigade_cleanup(inctx->bb);
    inctx->bb = NULL;

    if (APR_STATUS_IS_EOF(inctx->rc) && inl) {
        /* Provide the results of this read pass,
         * without resetting the BIO retry_read flag
         */
        return (int)inl;
    }

    return -1;
}

static int bio_filter_in_write(BIO *bio, const char *in, int inl)
{
    return -1;
}

static int bio_filter_in_puts(BIO *bio, const char *str)
{
    return -1;
}

static int bio_filter_in_gets(BIO *bio, char *buf, int size)
{
    return -1;
}

static long bio_filter_in_ctrl(BIO *bio, int cmd, long num, void *ptr)
{
    return -1;
}

#if MODSSL_USE_OPENSSL_PRE_1_1_API
        
static BIO_METHOD bio_filter_out_method = {
    BIO_TYPE_MEM,
    "APR output filter",
    bio_filter_out_write,
    bio_filter_out_read,     /* read is never called */
    bio_filter_out_puts,     /* puts is never called */
    bio_filter_out_gets,     /* gets is never called */
    bio_filter_out_ctrl,
    bio_filter_create,
    bio_filter_destroy,
    NULL
};

static BIO_METHOD bio_filter_in_method = {
    BIO_TYPE_MEM,
    "APR input filter",
    bio_filter_in_write,        /* write is never called */
    bio_filter_in_read,
    bio_filter_in_puts,         /* puts is never called */
    bio_filter_in_gets,         /* gets is never called */
    bio_filter_in_ctrl,         /* ctrl is never called */
    bio_filter_create,
    bio_filter_destroy,
    NULL
};

#else

static BIO_METHOD *bio_filter_out_method = NULL;
static BIO_METHOD *bio_filter_in_method = NULL;

void init_bio_methods(void)
{
    bio_filter_out_method = BIO_meth_new(BIO_TYPE_MEM, "APR output filter");
    BIO_meth_set_write(bio_filter_out_method, &bio_filter_out_write);
    BIO_meth_set_read(bio_filter_out_method, &bio_filter_out_read); /* read is never called */
    BIO_meth_set_puts(bio_filter_out_method, &bio_filter_out_puts); /* puts is never called */
    BIO_meth_set_gets(bio_filter_out_method, &bio_filter_out_gets); /* gets is never called */
    BIO_meth_set_ctrl(bio_filter_out_method, &bio_filter_out_ctrl);
    BIO_meth_set_create(bio_filter_out_method, &bio_filter_create);
    BIO_meth_set_destroy(bio_filter_out_method, &bio_filter_destroy);

    bio_filter_in_method = BIO_meth_new(BIO_TYPE_MEM, "APR input filter");
    BIO_meth_set_write(bio_filter_in_method, &bio_filter_in_write); /* write is never called */
    BIO_meth_set_read(bio_filter_in_method, &bio_filter_in_read);
    BIO_meth_set_puts(bio_filter_in_method, &bio_filter_in_puts);   /* puts is never called */
    BIO_meth_set_gets(bio_filter_in_method, &bio_filter_in_gets);   /* gets is never called */
    BIO_meth_set_ctrl(bio_filter_in_method, &bio_filter_in_ctrl);   /* ctrl is never called */
    BIO_meth_set_create(bio_filter_in_method, &bio_filter_create);
    BIO_meth_set_destroy(bio_filter_in_method, &bio_filter_destroy);
}

void free_bio_methods(void)
{
    BIO_meth_free(bio_filter_out_method);
    BIO_meth_free(bio_filter_in_method);
}
#endif

static apr_status_t ssl_io_input_read(bio_filter_in_ctx_t *inctx,
                                      char *buf,
                                      apr_size_t *len)
{
    apr_size_t wanted = *len;
    apr_size_t bytes = 0;
    int rc;

    *len = 0;

    /* If we have something leftover from last time, try that first. */
    if ((bytes = char_buffer_read(&inctx->cbuf, buf, wanted))) {
        *len = bytes;
        if (inctx->mode == AP_MODE_SPECULATIVE) {
            /* We want to rollback this read. */
            if (inctx->cbuf.length > 0) {
                inctx->cbuf.value -= bytes;
                inctx->cbuf.length += bytes;
            } else {
                char_buffer_write(&inctx->cbuf, buf, (int)bytes);
            }
            return APR_SUCCESS;
        }
        /* This could probably be *len == wanted, but be safe from stray
         * photons.
         */
        if (*len >= wanted) {
            return APR_SUCCESS;
        }
        if (inctx->mode == AP_MODE_GETLINE) {
            if (memchr(buf, APR_ASCII_LF, *len)) {
                return APR_SUCCESS;
            }
        }
        else {
            /* Down to a nonblock pattern as we have some data already
             */
            inctx->block = APR_NONBLOCK_READ;
        }
    }

    while (1) {

        if (!inctx->filter_ctx->pssl) {
            /* Ensure a non-zero error code is returned */
            if (inctx->rc == APR_SUCCESS) {
                inctx->rc = APR_EGENERAL;
            }
            break;
        }

        /* We rely on SSL_get_error() after the read, which requires an empty
         * error queue before the read in order to work properly.
         */
        ERR_clear_error();

        /* SSL_read may not read because we haven't taken enough data
         * from the stack.  This is where we want to consider all of
         * the blocking and SPECULATIVE semantics
         */
        rc = SSL_read(inctx->filter_ctx->pssl, buf + bytes, wanted - bytes);

        if (rc > 0) {
            *len += rc;
            if (inctx->mode == AP_MODE_SPECULATIVE) {
                /* We want to rollback this read. */
                char_buffer_write(&inctx->cbuf, buf, rc);
            }
            return inctx->rc;
        }
        else if (rc == 0) {
            /* If EAGAIN, we will loop given a blocking read,
             * otherwise consider ourselves at EOF.
             */
            if (APR_STATUS_IS_EAGAIN(inctx->rc)
                    || APR_STATUS_IS_EINTR(inctx->rc)) {
                /* Already read something, return APR_SUCCESS instead.
                 * On win32 in particular, but perhaps on other kernels,
                 * a blocking call isn't 'always' blocking.
                 */
                if (*len > 0) {
                    inctx->rc = APR_SUCCESS;
                    break;
                }
                if (inctx->block == APR_NONBLOCK_READ) {
                    break;
                }
            }
            else {
                if (*len > 0) {
                    inctx->rc = APR_SUCCESS;
                }
                else {
                    inctx->rc = APR_EOF;
                }
                break;
            }
        }
        else /* (rc < 0) */ {
            int ssl_err = SSL_get_error(inctx->filter_ctx->pssl, rc);
            conn_rec *c = (conn_rec*)SSL_get_app_data(inctx->filter_ctx->pssl);

            if (ssl_err == SSL_ERROR_WANT_READ) {
                /*
                 * If OpenSSL wants to read more, and we were nonblocking,
                 * report as an EAGAIN.  Otherwise loop, pulling more
                 * data from network filter.
                 *
                 * (This is usually the case when the client forces an SSL
                 * renegotiation which is handled implicitly by OpenSSL.)
                 */
                inctx->rc = APR_EAGAIN;

                if (*len > 0) {
                    inctx->rc = APR_SUCCESS;
                    break;
                }
                if (inctx->block == APR_NONBLOCK_READ) {
                    break;
                }
                continue;  /* Blocking and nothing yet?  Try again. */
            }
            else if (ssl_err == SSL_ERROR_SYSCALL) {
                if (APR_STATUS_IS_EAGAIN(inctx->rc)
                        || APR_STATUS_IS_EINTR(inctx->rc)) {
                    /* Already read something, return APR_SUCCESS instead. */
                    if (*len > 0) {
                        inctx->rc = APR_SUCCESS;
                        break;
                    }
                    if (inctx->block == APR_NONBLOCK_READ) {
                        break;
                    }
                    continue;  /* Blocking and nothing yet?  Try again. */
                }
                else if (APR_STATUS_IS_TIMEUP(inctx->rc)) {
                    /* just return it, the calling layer might be fine with it,
                       and we do not want to bloat the log. */
                }
                else {
                    ap_log_cerror(APLOG_MARK, APLOG_INFO, inctx->rc, c, APLOGNO(01991)
                                  "SSL input filter read failed.");
                }
            }
            else /* if (ssl_err == SSL_ERROR_SSL) */ {
                /*
                 * Log SSL errors and any unexpected conditions.
                 */
                ap_log_cerror(APLOG_MARK, APLOG_INFO, inctx->rc, c, APLOGNO(01992)
                              "SSL library error %d reading data", ssl_err);
                ssl_log_ssl_error(SSLLOG_MARK, APLOG_INFO, mySrvFromConn(c));

            }
            if (inctx->rc == APR_SUCCESS) {
                inctx->rc = APR_EGENERAL;
            }
            break;
        }
    }
    return inctx->rc;
}

/* Read a line of input from the SSL input layer into buffer BUF of
 * length *LEN; updating *len to reflect the length of the line
 * including the LF character. */
static apr_status_t ssl_io_input_getline(bio_filter_in_ctx_t *inctx,
                                         char *buf,
                                         apr_size_t *len)
{
    const char *pos = NULL;
    apr_status_t status;
    apr_size_t tmplen = *len, buflen = *len, offset = 0;

    *len = 0;

    /*
     * in most cases we get all the headers on the first SSL_read.
     * however, in certain cases SSL_read will only get a partial
     * chunk of the headers, so we try to read until LF is seen.
     */

    while (tmplen > 0) {
        status = ssl_io_input_read(inctx, buf + offset, &tmplen);

        if (status != APR_SUCCESS) {
            if (APR_STATUS_IS_EAGAIN(status) && (*len > 0)) {
                /* Save the part of the line we already got */
                char_buffer_write(&inctx->cbuf, buf, *len);
            }
            return status;
        }

        *len += tmplen;

        if ((pos = memchr(buf, APR_ASCII_LF, *len))) {
            break;
        }

        offset += tmplen;
        tmplen = buflen - offset;
    }

    if (pos) {
        char *value;
        int length;
        apr_size_t bytes = pos - buf;

        bytes += 1;
        value = buf + bytes;
        length = *len - bytes;

        char_buffer_write(&inctx->cbuf, value, length);

        *len = bytes;
    }

    return APR_SUCCESS;
}


static apr_status_t ssl_filter_write(ap_filter_t *f,
                                     const char *data,
                                     apr_size_t len)
{
    ssl_filter_ctx_t *filter_ctx = f->ctx;
    bio_filter_out_ctx_t *outctx;
    int res;

    /* write SSL */
    if (filter_ctx->pssl == NULL) {
        return APR_EGENERAL;
    }

    /* We rely on SSL_get_error() after the write, which requires an empty error
     * queue before the write in order to work properly.
     */
    ERR_clear_error();

    outctx = (bio_filter_out_ctx_t *)BIO_get_data(filter_ctx->pbioWrite);
    res = SSL_write(filter_ctx->pssl, (unsigned char *)data, len);

    if (res < 0) {
        int ssl_err = SSL_get_error(filter_ctx->pssl, res);
        conn_rec *c = (conn_rec*)SSL_get_app_data(outctx->filter_ctx->pssl);

        if (ssl_err == SSL_ERROR_WANT_WRITE) {
            /*
             * If OpenSSL wants to write more, and we were nonblocking,
             * report as an EAGAIN.  Otherwise loop, pushing more
             * data at the network filter.
             *
             * (This is usually the case when the client forces an SSL
             * renegotiation which is handled implicitly by OpenSSL.)
             */
            outctx->rc = APR_EAGAIN;
        }
        else if (ssl_err == SSL_ERROR_WANT_READ) {
            /*
             * If OpenSSL wants to read during write, and we were
             * nonblocking, set the sense explicitly to read and
             * report as an EAGAIN.
             *
             * (This is usually the case when the client forces an SSL
             * renegotiation which is handled implicitly by OpenSSL.)
             */
            outctx->c->cs->sense = CONN_SENSE_WANT_READ;
            outctx->rc = APR_EAGAIN;
        }
        else if (ssl_err == SSL_ERROR_SYSCALL) {
            ap_log_cerror(APLOG_MARK, APLOG_INFO, outctx->rc, c, APLOGNO(01993)
                          "SSL output filter write failed.");
        }
        else /* if (ssl_err == SSL_ERROR_SSL) */ {
            /*
             * Log SSL errors
             */
            ap_log_cerror(APLOG_MARK, APLOG_INFO, outctx->rc, c, APLOGNO(01994)
                          "SSL library error %d writing data", ssl_err);
            ssl_log_ssl_error(SSLLOG_MARK, APLOG_INFO, mySrvFromConn(c));
        }
        if (outctx->rc == APR_SUCCESS) {
            outctx->rc = APR_EGENERAL;
        }
    }
    else if ((apr_size_t)res != len) {
        conn_rec *c = f->c;
        char *reason = "reason unknown";

        /* XXX: probably a better way to determine this */
        if (SSL_total_renegotiations(filter_ctx->pssl)) {
            reason = "likely due to failed renegotiation";
        }

        ap_log_cerror(APLOG_MARK, APLOG_INFO, outctx->rc, c, APLOGNO(01995)
                      "failed to write %" APR_SSIZE_T_FMT
                      " of %" APR_SIZE_T_FMT " bytes (%s)",
                      len - (apr_size_t)res, len, reason);

        outctx->rc = APR_EGENERAL;
    }
    return outctx->rc;
}

/* Just use a simple request.  Any request will work for this, because
 * we use a flag in the conn_rec->conn_vector now.  The fake request just
 * gets the request back to the Apache core so that a response can be sent.
 * Since we use an HTTP/1.x request, we also have to inject the empty line
 * that terminates the headers, or the core will read more data from the
 * socket.
 */
#define HTTP_ON_HTTPS_PORT \
    "GET / HTTP/1.0" CRLF

#define HTTP_ON_HTTPS_PORT_BUCKET(alloc) \
    apr_bucket_immortal_create(HTTP_ON_HTTPS_PORT, \
                               sizeof(HTTP_ON_HTTPS_PORT) - 1, \
                               alloc)

/* Custom apr_status_t error code, used when a plain HTTP request is
 * recevied on an SSL port. */
#define MODSSL_ERROR_HTTP_ON_HTTPS (APR_OS_START_USERERR + 0)

/* Custom apr_status_t error code, used when the proxy cannot
 * establish an outgoing SSL connection. */
#define MODSSL_ERROR_BAD_GATEWAY (APR_OS_START_USERERR + 1)

static void ssl_io_filter_disable(SSLConnRec *sslconn,
                                  bio_filter_in_ctx_t *inctx)
{
    SSL_free(inctx->ssl);
    sslconn->ssl = NULL;
    inctx->ssl = NULL;
    inctx->filter_ctx->pssl = NULL;
}

static apr_status_t ssl_io_filter_error(bio_filter_in_ctx_t *inctx,
                                        apr_bucket_brigade *bb,
                                        apr_status_t status,
                                        int is_init)
{
    ap_filter_t *f = inctx->f;
    SSLConnRec *sslconn = myConnConfig(f->c);
    apr_bucket *bucket;
    int send_eos = 1;

    switch (status) {
    case MODSSL_ERROR_HTTP_ON_HTTPS:
            /* log the situation */
            ap_log_cerror(APLOG_MARK, APLOG_INFO, 0, f->c, APLOGNO(01996)
                         "SSL handshake failed: HTTP spoken on HTTPS port; "
                         "trying to send HTML error page");
            ssl_log_ssl_error(SSLLOG_MARK, APLOG_INFO, sslconn->server);

            ssl_io_filter_disable(sslconn, inctx);
            f->c->keepalive = AP_CONN_CLOSE;
            if (is_init) {
                sslconn->non_ssl_request = NON_SSL_SEND_REQLINE;
                return APR_EGENERAL;
            }
            sslconn->non_ssl_request = NON_SSL_SEND_HDR_SEP;

            /* fake the request line */
            bucket = HTTP_ON_HTTPS_PORT_BUCKET(f->c->bucket_alloc);
            send_eos = 0;
            break;

    case MODSSL_ERROR_BAD_GATEWAY:
        bucket = ap_bucket_error_create(HTTP_BAD_REQUEST, NULL,
                                        f->c->pool,
                                        f->c->bucket_alloc);
        ap_log_cerror(APLOG_MARK, APLOG_INFO, 0, f->c, APLOGNO(01997)
                      "SSL handshake failed: sending 502");
        break;

    default:
        return status;
    }

    APR_BRIGADE_INSERT_TAIL(bb, bucket);
    if (send_eos) {
        bucket = apr_bucket_eos_create(f->c->bucket_alloc);
        APR_BRIGADE_INSERT_TAIL(bb, bucket);
    }
    return APR_SUCCESS;
}

static const char ssl_io_filter[] = "SSL/TLS Filter";
static const char ssl_io_buffer[] = "SSL/TLS Buffer";