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httpd using mctls version 0.1
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/*      Copyright (c) 2003-11, WebThing Ltd
 *      Copyright (c) 2011-, The Apache Software Foundation
 *
 * 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.
 */

/*      GO_FASTER
        You can #define GO_FASTER to disable trace logging.
*/

#ifdef GO_FASTER
#define VERBOSE(x)
#define VERBOSEB(x)
#else
#define VERBOSE(x) if (verbose) x
#define VERBOSEB(x) if (verbose) {x}
#endif

/* libxml2 */
#include <libxml/HTMLparser.h>

#include "http_protocol.h"
#include "http_config.h"
#include "http_log.h"
#include "apr_strings.h"
#include "apr_hash.h"
#include "apr_strmatch.h"
#include "apr_lib.h"

#include "apr_optional.h"
#include "mod_xml2enc.h"
#include "http_request.h"
#include "ap_expr.h"

/* globals set once at startup */
static ap_rxplus_t *old_expr;
static ap_regex_t *seek_meta;
static const apr_strmatch_pattern* seek_content;
static apr_status_t (*xml2enc_charset)(request_rec*, xmlCharEncoding*, const char**) = NULL;
static apr_status_t (*xml2enc_filter)(request_rec*, const char*, unsigned int) = NULL;

module AP_MODULE_DECLARE_DATA proxy_html_module;

#define M_HTML                  0x01
#define M_EVENTS                0x02
#define M_CDATA                 0x04
#define M_REGEX                 0x08
#define M_ATSTART               0x10
#define M_ATEND                 0x20
#define M_LAST                  0x40
#define M_NOTLAST               0x80
#define M_INTERPOLATE_TO        0x100
#define M_INTERPOLATE_FROM      0x200

typedef struct {
    const char *val;
} tattr;
typedef struct {
    unsigned int start;
    unsigned int end;
} meta;
typedef struct urlmap {
    struct urlmap *next;
    unsigned int flags;
    unsigned int regflags;
    union {
        const char *c;
        ap_regex_t *r;
    } from;
    const char *to;
    ap_expr_info_t *cond;
} urlmap;
typedef struct {
    urlmap *map;
    const char *doctype;
    const char *etag;
    unsigned int flags;
    size_t bufsz;
    apr_hash_t *links;
    apr_array_header_t *events;
    const char *charset_out;
    int extfix;
    int metafix;
    int strip_comments;
    int interp;
    int enabled;
} proxy_html_conf;
typedef struct {
    ap_filter_t *f;
    proxy_html_conf *cfg;
    htmlParserCtxtPtr parser;
    apr_bucket_brigade *bb;
    char *buf;
    size_t offset;
    size_t avail;
    const char *encoding;
    urlmap *map;
} saxctxt;


#define NORM_LC 0x1
#define NORM_MSSLASH 0x2
#define NORM_RESET 0x4
static htmlSAXHandler sax;

typedef enum { ATTR_IGNORE, ATTR_URI, ATTR_EVENT } rewrite_t;

static const char *const fpi_html =
        "<!DOCTYPE html PUBLIC \"-//W3C//DTD HTML 4.01//EN\">\n";
static const char *const fpi_html_legacy =
        "<!DOCTYPE html PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">\n";
static const char *const fpi_xhtml =
        "<!DOCTYPE html PUBLIC \"-//W3C//DTD XHTML 1.0 Strict//EN\" \"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd\">\n";
static const char *const fpi_xhtml_legacy =
        "<!DOCTYPE html PUBLIC \"-//W3C//DTD XHTML 1.0 Transitional//EN\" \"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd\">\n";
static const char *const html_etag = ">";
static const char *const xhtml_etag = " />";
/*#define DEFAULT_DOCTYPE fpi_html */
static const char *const DEFAULT_DOCTYPE = "";
#define DEFAULT_ETAG html_etag

static void normalise(unsigned int flags, char *str)
{
    char *p;
    if (flags & NORM_LC)
        for (p = str; *p; ++p)
            if (isupper(*p))
                *p = tolower(*p);

    if (flags & NORM_MSSLASH)
        for (p = ap_strchr(str, '\\'); p; p = ap_strchr(p+1, '\\'))
            *p = '/';

}
#define consume_buffer(ctx,inbuf,bytes,flag) \
        htmlParseChunk(ctx->parser, inbuf, bytes, flag)

#define AP_fwrite(ctx,inbuf,bytes,flush) \
        ap_fwrite(ctx->f->next, ctx->bb, inbuf, bytes);

/* This is always utf-8 on entry.  We can convert charset within FLUSH */
#define FLUSH AP_fwrite(ctx, (chars+begin), (i-begin), 0); begin = i+1
static void pcharacters(void *ctxt, const xmlChar *uchars, int length)
{
    const char *chars = (const char*) uchars;
    saxctxt *ctx = (saxctxt*) ctxt;
    int i;
    int begin;
    for (begin=i=0; i<length; i++) {
        switch (chars[i]) {
        case '&' : FLUSH; ap_fputs(ctx->f->next, ctx->bb, "&amp;"); break;
        case '<' : FLUSH; ap_fputs(ctx->f->next, ctx->bb, "&lt;"); break;
        case '>' : FLUSH; ap_fputs(ctx->f->next, ctx->bb, "&gt;"); break;
        case '"' : FLUSH; ap_fputs(ctx->f->next, ctx->bb, "&quot;"); break;
        default : break;
        }
    }
    FLUSH;
}

static void preserve(saxctxt *ctx, const size_t len)
{
    char *newbuf;
    if (len <= (ctx->avail - ctx->offset))
        return;
    else while (len > (ctx->avail - ctx->offset))
        ctx->avail += ctx->cfg->bufsz;

    newbuf = realloc(ctx->buf, ctx->avail);
    if (newbuf != ctx->buf) {
        if (ctx->buf)
            apr_pool_cleanup_kill(ctx->f->r->pool, ctx->buf,
                                  (int(*)(void*))free);
        apr_pool_cleanup_register(ctx->f->r->pool, newbuf,
                                  (int(*)(void*))free, apr_pool_cleanup_null);
        ctx->buf = newbuf;
    }
}

static void pappend(saxctxt *ctx, const char *buf, const size_t len)
{
    preserve(ctx, len);
    memcpy(ctx->buf+ctx->offset, buf, len);
    ctx->offset += len;
}

static void dump_content(saxctxt *ctx)
{
    urlmap *m;
    char *found;
    size_t s_from, s_to;
    size_t match;
    char c = 0;
    int nmatch;
    ap_regmatch_t pmatch[10];
    char *subs;
    size_t len, offs;
    urlmap *themap = ctx->map;
#ifndef GO_FASTER
    int verbose = APLOGrtrace1(ctx->f->r);
#endif

    pappend(ctx, &c, 1);        /* append null byte */
        /* parse the text for URLs */
    for (m = themap; m; m = m->next) {
        if (!(m->flags & M_CDATA))
            continue;
        if (m->flags & M_REGEX) {
            nmatch = 10;
            offs = 0;
            while (!ap_regexec(m->from.r, ctx->buf+offs, nmatch, pmatch, 0)) {
                match = pmatch[0].rm_so;
                s_from = pmatch[0].rm_eo - match;
                subs = ap_pregsub(ctx->f->r->pool, m->to, ctx->buf+offs,
                                  nmatch, pmatch);
                s_to = strlen(subs);
                len = strlen(ctx->buf);
                offs += match;
                VERBOSEB(
                    const char *f = apr_pstrndup(ctx->f->r->pool,
                    ctx->buf + offs, s_from);
                    ap_log_rerror(APLOG_MARK, APLOG_TRACE3, 0, ctx->f->r,
                                  "C/RX: match at %s, substituting %s", f, subs);
                )
                if (s_to > s_from) {
                    preserve(ctx, s_to - s_from);
                    memmove(ctx->buf+offs+s_to, ctx->buf+offs+s_from,
                            len + 1 - s_from - offs);
                    memcpy(ctx->buf+offs, subs, s_to);
                }
                else {
                    memcpy(ctx->buf + offs, subs, s_to);
                    memmove(ctx->buf+offs+s_to, ctx->buf+offs+s_from,
                            len + 1 - s_from - offs);
                }
                offs += s_to;
            }
        }
        else {
            s_from = strlen(m->from.c);
            s_to = strlen(m->to);
            for (found = strstr(ctx->buf, m->from.c); found;
                 found = strstr(ctx->buf+match+s_to, m->from.c)) {
                match = found - ctx->buf;
                if ((m->flags & M_ATSTART) && (match != 0))
                    break;
                len = strlen(ctx->buf);
                if ((m->flags & M_ATEND) && (match < (len - s_from)))
                    continue;
                VERBOSE(ap_log_rerror(APLOG_MARK, APLOG_TRACE3, 0, ctx->f->r,
                                      "C: matched %s, substituting %s",
                                      m->from.c, m->to));
                if (s_to > s_from) {
                    preserve(ctx, s_to - s_from);
                    memmove(ctx->buf+match+s_to, ctx->buf+match+s_from,
                            len + 1 - s_from - match);
                    memcpy(ctx->buf+match, m->to, s_to);
                }
                else {
                    memcpy(ctx->buf+match, m->to, s_to);
                    memmove(ctx->buf+match+s_to, ctx->buf+match+s_from,
                            len + 1 - s_from - match);
                }
            }
        }
    }
    AP_fwrite(ctx, ctx->buf, strlen(ctx->buf), 1);
}
static void pcdata(void *ctxt, const xmlChar *uchars, int length)
{
    const char *chars = (const char*) uchars;
    saxctxt *ctx = (saxctxt*) ctxt;
    if (ctx->cfg->extfix) {
        pappend(ctx, chars, length);
    }
    else {
        /* not sure if this should force-flush
         * (i.e. can one cdata section come in multiple calls?)
         */
        AP_fwrite(ctx, chars, length, 0);
    }
}
static void pcomment(void *ctxt, const xmlChar *uchars)
{
    const char *chars = (const char*) uchars;
    saxctxt *ctx = (saxctxt*) ctxt;
    if (ctx->cfg->strip_comments)
        return;

    if (ctx->cfg->extfix) {
        pappend(ctx, "<!--", 4);
        pappend(ctx, chars, strlen(chars));
        pappend(ctx, "-->", 3);
    }
    else {
        ap_fputs(ctx->f->next, ctx->bb, "<!--");
        AP_fwrite(ctx, chars, strlen(chars), 1);
        ap_fputs(ctx->f->next, ctx->bb, "-->");
    }
}
static void pendElement(void *ctxt, const xmlChar *uname)
{
    saxctxt *ctx = (saxctxt*) ctxt;
    const char *name = (const char*) uname;
    const htmlElemDesc* desc = htmlTagLookup(uname);

    if ((ctx->cfg->doctype == fpi_html) || (ctx->cfg->doctype == fpi_xhtml)) {
        /* enforce html */
        if (!desc || desc->depr)
            return;
    
    }
    else if ((ctx->cfg->doctype == fpi_html)
             || (ctx->cfg->doctype == fpi_xhtml)) {
        /* enforce html legacy */
        if (!desc)
            return;
    }
    /* TODO - implement HTML "allowed here" using the stack */
    /* nah.  Keeping the stack is too much overhead */

    if (ctx->offset > 0) {
        dump_content(ctx);
        ctx->offset = 0;        /* having dumped it, we can re-use the memory */
    }
    if (!desc || !desc->empty) {
        ap_fprintf(ctx->f->next, ctx->bb, "</%s>", name);
    }
}

static void pstartElement(void *ctxt, const xmlChar *uname,
                          const xmlChar** uattrs)
{
    int required_attrs;
    int num_match;
    size_t offs, len;
    char *subs;
    rewrite_t is_uri;
    const char** a;
    urlmap *m;
    size_t s_to, s_from, match;
    char *found;
    saxctxt *ctx = (saxctxt*) ctxt;
    size_t nmatch;
    ap_regmatch_t pmatch[10];
#ifndef GO_FASTER
    int verbose = APLOGrtrace1(ctx->f->r);
#endif
    apr_array_header_t *linkattrs;
    int i;
    const char *name = (const char*) uname;
    const char** attrs = (const char**) uattrs;
    const htmlElemDesc* desc = htmlTagLookup(uname);
    urlmap *themap = ctx->map;
#ifdef HAVE_STACK
    const void** descp;
#endif
    int enforce = 0;
    if ((ctx->cfg->doctype == fpi_html) || (ctx->cfg->doctype == fpi_xhtml)) {
        /* enforce html */
        enforce = 2;
        if (!desc || desc->depr)
            return;
    
    }
    else if ((ctx->cfg->doctype == fpi_html)
             || (ctx->cfg->doctype == fpi_xhtml)) {
        enforce = 1;
        /* enforce html legacy */
        if (!desc) {
            return;
        }
    }
    if (!desc && enforce) {
        ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, ctx->f->r, APLOGNO(01416)
                      "Bogus HTML element %s dropped", name);
        return;
    }
    if (desc && desc->depr && (enforce == 2)) {
        ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, ctx->f->r, APLOGNO(01417)
                      "Deprecated HTML element %s dropped", name);
        return;
    }
#ifdef HAVE_STACK
    descp = apr_array_push(ctx->stack);
    *descp = desc;
    /* TODO - implement HTML "allowed here" */
#endif

    ap_fputc(ctx->f->next, ctx->bb, '<');
    ap_fputs(ctx->f->next, ctx->bb, name);

    required_attrs = 0;
    if ((enforce > 0) && (desc != NULL) && (desc->attrs_req != NULL))
        for (a = desc->attrs_req; *a; a++)
            ++required_attrs;

    if (attrs) {
        linkattrs = apr_hash_get(ctx->cfg->links, name, APR_HASH_KEY_STRING);
        for (a = attrs; *a; a += 2) {
            if (desc && enforce > 0) {
                switch (htmlAttrAllowed(desc, (xmlChar*)*a, 2-enforce)) {
                case HTML_INVALID:
                    ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, ctx->f->r, APLOGNO(01418)
                                  "Bogus HTML attribute %s of %s dropped",
                                  *a, name);
                    continue;
                case HTML_DEPRECATED:
                    ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, ctx->f->r, APLOGNO(01419)
                                  "Deprecated HTML attribute %s of %s dropped",
                                  *a, name);
                    continue;
                case HTML_REQUIRED:
                    required_attrs--;   /* cross off the number still needed */
                /* fallthrough - required implies valid */
                default:
                    break;
                }
            }
            ctx->offset = 0;
            if (a[1]) {
                pappend(ctx, a[1], strlen(a[1])+1);
                is_uri = ATTR_IGNORE;
                if (linkattrs) {
                    tattr *attrs = (tattr*) linkattrs->elts;
                    for (i=0; i < linkattrs->nelts; ++i) {
                        if (!strcmp(*a, attrs[i].val)) {
                            is_uri = ATTR_URI;
                            break;
                        }
                    }
                }
                if ((is_uri == ATTR_IGNORE) && ctx->cfg->extfix
                    && (ctx->cfg->events != NULL)) {
                    for (i=0; i < ctx->cfg->events->nelts; ++i) {
                        tattr *attrs = (tattr*) ctx->cfg->events->elts;
                        if (!strcmp(*a, attrs[i].val)) {
                            is_uri = ATTR_EVENT;
                            break;
                        }
                    }
                }
                switch (is_uri) {
                case ATTR_URI:
                    num_match = 0;
                    for (m = themap; m; m = m->next) {
                        if (!(m->flags & M_HTML))
                            continue;
                        if (m->flags & M_REGEX) {
                            nmatch = 10;
                            if (!ap_regexec(m->from.r, ctx->buf, nmatch,
                                            pmatch, 0)) {
                                ++num_match;
                                offs = match = pmatch[0].rm_so;
                                s_from = pmatch[0].rm_eo - match;
                                subs = ap_pregsub(ctx->f->r->pool, m->to,
                                                  ctx->buf, nmatch, pmatch);
                                VERBOSE({
                                    const char *f;
                                    f = apr_pstrndup(ctx->f->r->pool,
                                                     ctx->buf + offs, s_from);
                                    ap_log_rerror(APLOG_MARK, APLOG_TRACE3, 0,
                                                  ctx->f->r,
                                         "H/RX: match at %s, substituting %s",
                                                  f, subs);
                                })
                                s_to = strlen(subs);
                                len = strlen(ctx->buf);
                                if (s_to > s_from) {
                                    preserve(ctx, s_to - s_from);
                                    memmove(ctx->buf+offs+s_to,
                                            ctx->buf+offs+s_from,
                                            len + 1 - s_from - offs);
                                    memcpy(ctx->buf+offs, subs, s_to);
                                }
                                else {
                                    memcpy(ctx->buf + offs, subs, s_to);
                                    memmove(ctx->buf+offs+s_to,
                                            ctx->buf+offs+s_from,
                                            len + 1 - s_from - offs);
                                }
                            }
                        } else {
                            s_from = strlen(m->from.c);
                            if (!strncasecmp(ctx->buf, m->from.c, s_from)) {
                                ++num_match;
                                s_to = strlen(m->to);
                                len = strlen(ctx->buf);
                                VERBOSE(ap_log_rerror(APLOG_MARK, APLOG_TRACE3,
                                                      0, ctx->f->r,
                                              "H: matched %s, substituting %s",
                                                      m->from.c, m->to));
                                if (s_to > s_from) {
                                    preserve(ctx, s_to - s_from);
                                    memmove(ctx->buf+s_to, ctx->buf+s_from,
                                            len + 1 - s_from);
                                    memcpy(ctx->buf, m->to, s_to);
                                }
                                else {     /* it fits in the existing space */
                                    memcpy(ctx->buf, m->to, s_to);
                                    memmove(ctx->buf+s_to, ctx->buf+s_from,
                                            len + 1 - s_from);
                                }
                                break;
                            }
                        }
                        /* URIs only want one match unless overridden in the config */
                        if ((num_match > 0) && !(m->flags & M_NOTLAST))
                            break;
                    }
                    break;
                case ATTR_EVENT:
                    for (m = themap; m; m = m->next) {
                        num_match = 0;        /* reset here since we're working per-rule */
                        if (!(m->flags & M_EVENTS))
                            continue;
                        if (m->flags & M_REGEX) {
                            nmatch = 10;
                            offs = 0;
                            while (!ap_regexec(m->from.r, ctx->buf+offs,
                                               nmatch, pmatch, 0)) {
                                match = pmatch[0].rm_so;
                                s_from = pmatch[0].rm_eo - match;
                                subs = ap_pregsub(ctx->f->r->pool, m->to, ctx->buf+offs,
                                                    nmatch, pmatch);
                                VERBOSE({
                                    const char *f;
                                    f = apr_pstrndup(ctx->f->r->pool,
                                                     ctx->buf + offs, s_from);
                                    ap_log_rerror(APLOG_MARK, APLOG_TRACE3, 0,
                                                  ctx->f->r,
                                           "E/RX: match at %s, substituting %s",
                                                  f, subs);
                                })
                                s_to = strlen(subs);
                                offs += match;
                                len = strlen(ctx->buf);
                                if (s_to > s_from) {
                                    preserve(ctx, s_to - s_from);
                                    memmove(ctx->buf+offs+s_to,
                                            ctx->buf+offs+s_from,
                                            len + 1 - s_from - offs);
                                    memcpy(ctx->buf+offs, subs, s_to);
                                }
                                else {
                                    memcpy(ctx->buf + offs, subs, s_to);
                                    memmove(ctx->buf+offs+s_to,
                                            ctx->buf+offs+s_from,
                                            len + 1 - s_from - offs);
                                }
                                offs += s_to;
                                ++num_match;
                            }
                        }
                        else {
                            found = strstr(ctx->buf, m->from.c);
                            if ((m->flags & M_ATSTART) && (found != ctx->buf))
                                continue;
                            while (found) {
                                s_from = strlen(m->from.c);
                                s_to = strlen(m->to);
                                match = found - ctx->buf;
                                if ((s_from < strlen(found))
                                    && (m->flags & M_ATEND)) {
                                    found = strstr(ctx->buf+match+s_from,
                                                   m->from.c);
                                    continue;
                                }
                                else {
                                    found = strstr(ctx->buf+match+s_to,
                                                   m->from.c);
                                }
                                VERBOSE(ap_log_rerror(APLOG_MARK, APLOG_TRACE3,
                                                      0, ctx->f->r,
                                              "E: matched %s, substituting %s",
                                                      m->from.c, m->to));
                                len = strlen(ctx->buf);
                                if (s_to > s_from) {
                                    preserve(ctx, s_to - s_from);
                                    memmove(ctx->buf+match+s_to,
                                            ctx->buf+match+s_from,
                                            len + 1 - s_from - match);
                                    memcpy(ctx->buf+match, m->to, s_to);
                                }
                                else {
                                    memcpy(ctx->buf+match, m->to, s_to);
                                    memmove(ctx->buf+match+s_to,
                                            ctx->buf+match+s_from,
                                            len + 1 - s_from - match);
                                }
                                ++num_match;
                            }
                        }
                        if (num_match && (m->flags & M_LAST))
                            break;
                    }
                    break;
                case ATTR_IGNORE:
                    break;
                }
            }
            if (!a[1])
                ap_fputstrs(ctx->f->next, ctx->bb, " ", a[0], NULL);
            else {

                if (ctx->cfg->flags != 0)
                    normalise(ctx->cfg->flags, ctx->buf);

                /* write the attribute, using pcharacters to html-escape
                   anything that needs it in the value.
                */
                ap_fputstrs(ctx->f->next, ctx->bb, " ", a[0], "=\"", NULL);
                pcharacters(ctx, (const xmlChar*)ctx->buf, strlen(ctx->buf));
                ap_fputc(ctx->f->next, ctx->bb, '"');
            }
        }
    }
    ctx->offset = 0;
    if (desc && desc->empty)
        ap_fputs(ctx->f->next, ctx->bb, ctx->cfg->etag);
    else
        ap_fputc(ctx->f->next, ctx->bb, '>');

    if ((enforce > 0) && (required_attrs > 0)) {
        /* if there are more required attributes than we found then complain */
        ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, ctx->f->r, APLOGNO(01420)
                      "HTML element %s is missing %d required attributes",
                      name, required_attrs);
    }
}

static meta *metafix(request_rec *r, const char *buf)
{
    meta *ret = NULL;
    size_t offs = 0;
    const char *p;
    const char *q;
    char *header;
    char *content;
    ap_regmatch_t pmatch[2];
    char delim;

    while (!ap_regexec(seek_meta, buf+offs, 2, pmatch, 0)) {
        header = NULL;
        content = NULL;
        p = buf+offs+pmatch[1].rm_eo;
        while (!apr_isalpha(*++p));
        for (q = p; apr_isalnum(*q) || (*q == '-'); ++q);
        header = apr_pstrndup(r->pool, p, q-p);
        if (strncasecmp(header, "Content-", 8)) {
            /* find content=... string */
            p = apr_strmatch(seek_content, buf+offs+pmatch[0].rm_so,
                              pmatch[0].rm_eo - pmatch[0].rm_so);
            /* if it doesn't contain "content", ignore, don't crash! */
            if (p != NULL) {
                while (*p) {
                    p += 7;
                    while (apr_isspace(*p))
                        ++p;
                    /* XXX Should we search for another content= pattern? */
                    if (*p != '=')
                        break;
                    while (*p && apr_isspace(*++p));
                    if ((*p == '\'') || (*p == '"')) {
                        delim = *p++;
                        for (q = p; *q && *q != delim; ++q);
                        /* No terminating delimiter found? Skip the boggus directive */
                        if (*q != delim)
                           break;
                    } else {
                        for (q = p; *q && !apr_isspace(*q) && (*q != '>'); ++q);
                    }
                    content = apr_pstrndup(r->pool, p, q-p);
                    break;
                }
            }
        }
        else if (!strncasecmp(header, "Content-Type", 12)) {
            ret = apr_palloc(r->pool, sizeof(meta));
            ret->start = offs+pmatch[0].rm_so;
            ret->end = offs+pmatch[0].rm_eo;
        }
        if (header && content) {
#ifndef GO_FASTER
            ap_log_rerror(APLOG_MARK, APLOG_TRACE2, 0, r,
                          "Adding header [%s: %s] from HTML META",
                          header, content); 
#endif
            apr_table_setn(r->headers_out, header, content);
        }
        offs += pmatch[0].rm_eo;
    }
    return ret;
}

static const char *interpolate_vars(request_rec *r, const char *str)
{
    const char *start;
    const char *end;
    const char *delim;
    const char *before;
    const char *after;
    const char *replacement;
    const char *var;
    for (;;) {
        start = str;
        if (start = ap_strstr_c(start, "${"), start == NULL)
            break;

        if (end = ap_strchr_c(start+2, '}'), end == NULL)
            break;

        delim = ap_strchr_c(start, '|');
        before = apr_pstrndup(r->pool, str, start-str);
        after = end+1;
        if (delim) {
            var = apr_pstrndup(r->pool, start+2, delim-start-2);
        }
        else {
            var = apr_pstrndup(r->pool, start+2, end-start-2);
        }
        replacement = apr_table_get(r->subprocess_env, var);
        if (!replacement) {
            if (delim)
                replacement = apr_pstrndup(r->pool, delim+1, end-delim-1);
            else
                replacement = "";
        }
        str = apr_pstrcat(r->pool, before, replacement, after, NULL);
        ap_log_rerror(APLOG_MARK, APLOG_TRACE1, 0, r,
                      "Interpolating %s  =>  %s", var, replacement);
    }
    return str;
}
static void fixup_rules(saxctxt *ctx)
{
    urlmap *newp;
    urlmap *p;
    urlmap *prev = NULL;
    request_rec *r = ctx->f->r;

    for (p = ctx->cfg->map; p; p = p->next) {
        if (p->cond != NULL) {
            const char *err;
            int ok = ap_expr_exec(r, p->cond, &err);
            if (err) {
                ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(01421)
                              "Error evaluating expr: %s", err);
            }
            if (ok == 0) {
                continue;  /* condition is unsatisfied */
            }
        }

        newp = apr_pmemdup(r->pool, p, sizeof(urlmap));

        if (newp->flags & M_INTERPOLATE_FROM) {
            newp->from.c = interpolate_vars(r, newp->from.c);
            if (!newp->from.c || !*newp->from.c)
                continue;        /* don't use empty from-pattern */
            if (newp->flags & M_REGEX) {
                newp->from.r = ap_pregcomp(r->pool, newp->from.c,
                                           newp->regflags);
            }
        }
        if (newp->flags & M_INTERPOLATE_TO) {
            newp->to = interpolate_vars(r, newp->to);
        }
        /* evaluate p->cond; continue if unsatisfied */
        /* create new urlmap with memcpy and append to map */
        /* interpolate from if flagged to do so */
        /* interpolate to if flagged to do so */

        if (prev != NULL)
            prev->next = newp;
        else
            ctx->map = newp;
        prev = newp;
    }

    if (prev)
        prev->next = NULL;
}

static saxctxt *check_filter_init (ap_filter_t *f)
{
    saxctxt *fctx;
    if (!f->ctx) {
        proxy_html_conf *cfg;
        const char *force;
        const char *errmsg = NULL;
        cfg = ap_get_module_config(f->r->per_dir_config, &proxy_html_module);
        force = apr_table_get(f->r->subprocess_env, "PROXY_HTML_FORCE");

        if (!force) {
            if (!f->r->proxyreq) {
                errmsg = "Non-proxy request; not inserting proxy-html filter";
            }
            else if (!f->r->content_type) {
                errmsg = "No content-type; bailing out of proxy-html filter";
            }
            else if (strncasecmp(f->r->content_type, "text/html", 9) &&
                     strncasecmp(f->r->content_type,
                                 "application/xhtml+xml", 21)) {
                errmsg = "Non-HTML content; not inserting proxy-html filter";
            }
        }
        if (!cfg->links) {
            errmsg = "No links configured: nothing for proxy-html filter to do";
        }

        if (errmsg) {
#ifndef GO_FASTER
            ap_log_rerror(APLOG_MARK, APLOG_TRACE1, 0, f->r, "%s", errmsg);
#endif
            ap_remove_output_filter(f);
            return NULL;
        }

        fctx = f->ctx = apr_pcalloc(f->r->pool, sizeof(saxctxt));
        fctx->f = f;
        fctx->bb = apr_brigade_create(f->r->pool,
                                      f->r->connection->bucket_alloc);
        fctx->cfg = cfg;
        apr_table_unset(f->r->headers_out, "Content-Length");

        if (cfg->interp)
            fixup_rules(fctx);
        else
            fctx->map = cfg->map;
        /* defer dealing with charset_out until after sniffing charset_in
         * so we can support setting one to t'other.
         */
    }
    return f->ctx;
}

static apr_status_t proxy_html_filter(ap_filter_t *f, apr_bucket_brigade *bb)
{
    apr_bucket* b;
    meta *m = NULL;
    xmlCharEncoding enc;
    const char *buf = 0;
    apr_size_t bytes = 0;
#ifndef USE_OLD_LIBXML2
    int xmlopts = XML_PARSE_RECOVER | XML_PARSE_NONET |
                  XML_PARSE_NOBLANKS | XML_PARSE_NOERROR | XML_PARSE_NOWARNING;
#endif

    saxctxt *ctxt = check_filter_init(f);
    if (!ctxt)
        return ap_pass_brigade(f->next, bb);
    for (b = APR_BRIGADE_FIRST(bb);
         b != APR_BRIGADE_SENTINEL(bb);
         b = APR_BUCKET_NEXT(b)) {
        if (APR_BUCKET_IS_METADATA(b)) {
            if (APR_BUCKET_IS_EOS(b)) {
                if (ctxt->parser != NULL) {
                    consume_buffer(ctxt, buf, 0, 1);
                }
                APR_BRIGADE_INSERT_TAIL(ctxt->bb,
                apr_bucket_eos_create(ctxt->bb->bucket_alloc));
                ap_pass_brigade(ctxt->f->next, ctxt->bb);
            }
            else if (APR_BUCKET_IS_FLUSH(b)) {
                /* pass on flush, except at start where it would cause
                 * headers to be sent before doc sniffing
                 */
                if (ctxt->parser != NULL) {
                    ap_fflush(ctxt->f->next, ctxt->bb);
                }
            }
        }
        else if (apr_bucket_read(b, &buf, &bytes, APR_BLOCK_READ)
                 == APR_SUCCESS) {
            if (ctxt->parser == NULL) {
                const char *cenc;
                if (!xml2enc_charset ||
                    (xml2enc_charset(f->r, &enc, &cenc) != APR_SUCCESS)) {
                    if (!xml2enc_charset)
                        ap_log_rerror(APLOG_MARK, APLOG_WARNING, 0, f->r, APLOGNO(01422)
                     "No i18n support found.  Install mod_xml2enc if required");
                    enc = XML_CHAR_ENCODING_NONE;
                    ap_set_content_type(f->r, "text/html;charset=utf-8");
                }
                else {
                    /* if we wanted a non-default charset_out, insert the
                     * xml2enc filter now that we've sniffed it
                     */
                    if (ctxt->cfg->charset_out && xml2enc_filter) {
                        if (*ctxt->cfg->charset_out != '*')
                            cenc = ctxt->cfg->charset_out;
                        xml2enc_filter(f->r, cenc, ENCIO_OUTPUT);
                        ap_set_content_type(f->r,
                                            apr_pstrcat(f->r->pool,
                                                        "text/html;charset=",
                                                        cenc, NULL));
                    }
                    else /* Normal case, everything worked, utf-8 output */
                        ap_set_content_type(f->r, "text/html;charset=utf-8");
                }

                ap_fputs(f->next, ctxt->bb, ctxt->cfg->doctype);
                ctxt->parser = htmlCreatePushParserCtxt(&sax, ctxt, buf,
                                                        4, 0, enc);
                buf += 4;
                bytes -= 4;
                if (ctxt->parser == NULL) {
                    apr_status_t rv = ap_pass_brigade(f->next, bb);
                    ap_remove_output_filter(f);
                    return rv;
                }
                apr_pool_cleanup_register(f->r->pool, ctxt->parser,
                                          (int(*)(void*))htmlFreeParserCtxt,
                                          apr_pool_cleanup_null);
#ifndef USE_OLD_LIBXML2
                if (xmlopts = xmlCtxtUseOptions(ctxt->parser, xmlopts), xmlopts)
                    ap_log_rerror(APLOG_MARK, APLOG_WARNING, 0, f->r, APLOGNO(01423)
                                  "Unsupported parser opts %x", xmlopts);
#endif
                if (ctxt->cfg->metafix)
                    m = metafix(f->r, buf);
                if (m) {
                    consume_buffer(ctxt, buf, m->start, 0);
                    consume_buffer(ctxt, buf+m->end, bytes-m->end, 0);
                }
                else {
                    consume_buffer(ctxt, buf, bytes, 0);
                }
            }
            else {
                consume_buffer(ctxt, buf, bytes, 0);
            }
        }
        else {
            ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, f->r, APLOGNO(01424)
                          "Error in bucket read");
        }
    }
    /*ap_fflush(ctxt->f->next, ctxt->bb);        // uncomment for debug */
    apr_brigade_cleanup(bb);
    return APR_SUCCESS;
}

static void *proxy_html_config(apr_pool_t *pool, char *x)
{
    proxy_html_conf *ret = apr_pcalloc(pool, sizeof(proxy_html_conf));
    ret->doctype = DEFAULT_DOCTYPE;
    ret->etag = DEFAULT_ETAG;
    ret->bufsz = 8192;
    /* ret->interp = 1; */
    /* don't initialise links and events until they get set/used */
    return ret;
}

static void *proxy_html_merge(apr_pool_t *pool, void *BASE, void *ADD)
{
    proxy_html_conf *base = (proxy_html_conf *) BASE;
    proxy_html_conf *add = (proxy_html_conf *) ADD;
    proxy_html_conf *conf = apr_palloc(pool, sizeof(proxy_html_conf));

    /* don't merge declarations - just use the most specific */
    conf->links = (add->links == NULL) ? base->links : add->links;
    conf->events = (add->events == NULL) ? base->events : add->events;

    conf->charset_out = (add->charset_out == NULL)
                        ? base->charset_out : add->charset_out;

    if (add->map && base->map) {
        urlmap *a;
        conf->map = NULL;
        for (a = base->map; a; a = a->next) {
            urlmap *save = conf->map;
            conf->map = apr_pmemdup(pool, a, sizeof(urlmap));
            conf->map->next = save;
        }
        for (a = add->map; a; a = a->next) {
            urlmap *save = conf->map;
            conf->map = apr_pmemdup(pool, a, sizeof(urlmap));
            conf->map->next = save;
        }
    }
    else
        conf->map = add->map ? add->map : base->map;

    conf->doctype = (add->doctype == DEFAULT_DOCTYPE)
                    ? base->doctype : add->doctype;
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