mod_filter.c

Apache官方在今天放出产品系列2.2的最新版本2.2.11的源码包 最流行的HTTP服务器软件之一

/* 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.
 */

#define APR_WANT_STRFUNC
#include "apr_want.h"
#include "apr_lib.h"
#include "apr_strings.h"
#include "apr_hash.h"
#include "httpd.h"
#include "http_config.h"
#include "http_request.h"
#include "http_log.h"
#include "util_filter.h"

module AP_MODULE_DECLARE_DATA filter_module;

/**
 * @brief is a filter provider, as defined and implemented by mod_filter.
 *
 * The struct is a linked list, with dispatch criteria
 * defined for each filter.  The provider implementation itself is a
 * (2.0-compatible) ap_filter_rec_t* frec.
 */
struct ap_filter_provider_t {
    /** How to match this provider to filter dispatch criterion */
    enum {
        STRING_MATCH,
        STRING_CONTAINS,
        REGEX_MATCH,
        INT_EQ,
        INT_LT,
        INT_LE,
        INT_GT,
        INT_GE,
        DEFINED
    } match_type;

    /** negation on match_type */
    int not;

    /** The dispatch match itself - union member depends on match_type */
    union {
        const char *string;
        ap_regex_t *regex;
        int         number;
    } match;

    /** The filter that implements this provider */
    ap_filter_rec_t *frec;

    /** The next provider in the list */
    ap_filter_provider_t *next;

    /** Dispatch criteria for filter providers */
    enum {
        HANDLER,
        REQUEST_HEADERS,
        RESPONSE_HEADERS,
        SUBPROCESS_ENV,
        CONTENT_TYPE
    } dispatch;

    /** Match value for filter providers */
    const char* value;
};

/** we need provider_ctx to save ctx values set by providers in filter_init */
typedef struct provider_ctx provider_ctx;
struct provider_ctx {
    ap_filter_provider_t *provider;
    void *ctx;
    provider_ctx *next;
};
typedef struct {
    ap_out_filter_func func;
    void *fctx;
    provider_ctx *init_ctx;
} harness_ctx;

typedef struct mod_filter_chain {
    const char *fname;
    struct mod_filter_chain *next;
} mod_filter_chain;

typedef struct {
    apr_hash_t *live_filters;
    mod_filter_chain *chain;
} mod_filter_cfg;

typedef struct {
    const char* range ;
} mod_filter_ctx ;


static void filter_trace(conn_rec *c, int debug, const char *fname,
                         apr_bucket_brigade *bb)
{
    apr_bucket *b;

    switch (debug) {
    case 0:        /* normal, operational use */
        return;
    case 1:        /* mod_diagnostics level */
        ap_log_cerror(APLOG_MARK, APLOG_DEBUG, 0, c, "%s", fname);
        for (b = APR_BRIGADE_FIRST(bb);
             b != APR_BRIGADE_SENTINEL(bb);
             b = APR_BUCKET_NEXT(b)) {

            ap_log_cerror(APLOG_MARK, APLOG_DEBUG, 0, c,
                          "%s: type: %s, length: %" APR_SIZE_T_FMT,
                          fname, b->type->name ? b->type->name : "(unknown)",
                          b->length);
        }
        break;
    }
}

static int filter_init(ap_filter_t *f)
{
    ap_filter_provider_t *p;
    provider_ctx *pctx;
    int err;
    ap_filter_rec_t *filter = f->frec;

    harness_ctx *fctx = apr_pcalloc(f->r->pool, sizeof(harness_ctx));
    for (p = filter->providers; p; p = p->next) {
        if (p->frec->filter_init_func == filter_init) {
            ap_log_cerror(APLOG_MARK, APLOG_ERR, 0, f->c,
                          "Chaining of FilterProviders not supported");
            return HTTP_INTERNAL_SERVER_ERROR;
        }
        else if (p->frec->filter_init_func) {
            f->ctx = NULL;
            if ((err = p->frec->filter_init_func(f)) != OK) {
                ap_log_cerror(APLOG_MARK, APLOG_ERR, 0, f->c,
                              "filter_init for %s failed", p->frec->name);
                return err;   /* if anyone errors out here, so do we */
            }
            if (f->ctx != NULL) {
                /* the filter init function set a ctx - we need to record it */
                pctx = apr_pcalloc(f->r->pool, sizeof(provider_ctx));
                pctx->provider = p;
                pctx->ctx = f->ctx;
                pctx->next = fctx->init_ctx;
                fctx->init_ctx = pctx;
            }
        }
    }
    f->ctx = fctx;
    return OK;
}

static int filter_lookup(ap_filter_t *f, ap_filter_rec_t *filter)
{
    ap_filter_provider_t *provider;
    const char *str = NULL;
    char *str1;
    int match;
    unsigned int proto_flags;
    request_rec *r = f->r;
    harness_ctx *ctx = f->ctx;
    provider_ctx *pctx;
    mod_filter_ctx *rctx = ap_get_module_config(r->request_config,
                                                &filter_module);

    /* Check registered providers in order */
    for (provider = filter->providers; provider; provider = provider->next) {
        match = 1;
        switch (provider->dispatch) {
        case REQUEST_HEADERS:
            str = apr_table_get(r->headers_in, provider->value);
            break;
        case RESPONSE_HEADERS:
            str = apr_table_get(r->headers_out, provider->value);
            break;
        case SUBPROCESS_ENV:
            str = apr_table_get(r->subprocess_env, provider->value);
            break;
        case CONTENT_TYPE:
            str = r->content_type;
            break;
        case HANDLER:
            str = r->handler;
            break;
        }

        /* treat nulls so we don't have to check every strcmp individually
         * Not sure if there's anything better to do with them
         */
        if (!str) {
            if (provider->match_type == DEFINED && provider->match.string) {
                match = 0;
            }
        }
        /* we can't check for NULL in provider as that kills integer 0
         * so we have to test each string/regexp case in the switch
         */
        else {
            switch (provider->match_type) {
            case STRING_MATCH:
                if (strcasecmp(str, provider->match.string)) {
                    match = 0;
                }
                break;
            case STRING_CONTAINS:
                str1 = apr_pstrdup(r->pool, str);
                ap_str_tolower(str1);
                if (!strstr(str1, provider->match.string)) {
                    match = 0;
                }
                break;
            case REGEX_MATCH:
                if (ap_regexec(provider->match.regex, str, 0, NULL, 0)
                    == AP_REG_NOMATCH) {
                    match = 0;
                }
                break;
            case INT_EQ:
                if (atoi(str) != provider->match.number) {
                    match = 0;
                }
                break;
            /* Integer comparisons should be [var] OP [match]
             * We need to set match = 0 if the condition fails
             */
            case INT_LT:
                if (atoi(str) >= provider->match.number) {
                    match = 0;
                }
                break;
            case INT_LE:
                if (atoi(str) > provider->match.number) {
                    match = 0;
                }
                break;
            case INT_GT:
                if (atoi(str) <= provider->match.number) {
                    match = 0;
                }
                break;
            case INT_GE:
                if (atoi(str) < provider->match.number) {
                    match = 0;
                }
                break;
            case DEFINED:        /* we already handled this:-) */
                break;
            }
        }

        if (match != provider->not) {
            /* condition matches this provider */
#ifndef NO_PROTOCOL
            /* check protocol
             *
             * FIXME:
             * This is a quick hack and almost certainly buggy.
             * The idea is that by putting this in mod_filter, we relieve
             * filter implementations of the burden of fixing up HTTP headers
             * for cases that are routinely affected by filters.
             *
             * Default is ALWAYS to do nothing, so as not to tread on the
             * toes of filters which want to do it themselves.
             *
             */
            proto_flags = provider->frec->proto_flags;

            /* some specific things can't happen in a proxy */
            if (r->proxyreq) {
                if (proto_flags & AP_FILTER_PROTO_NO_PROXY) {
                    /* can't use this provider; try next */
                    continue;
                }

                if (proto_flags & AP_FILTER_PROTO_TRANSFORM) {
                    str = apr_table_get(r->headers_out, "Cache-Control");
                    if (str) {
                        str1 = apr_pstrdup(r->pool, str);
                        ap_str_tolower(str1);
                        if (strstr(str1, "no-transform")) {
                            /* can't use this provider; try next */
                            continue;
                        }
                    }
                    apr_table_addn(r->headers_out, "Warning",
                                   apr_psprintf(r->pool,
                                                "214 %s Transformation applied",
                                                r->hostname));
                }
            }

            /* things that are invalidated if the filter transforms content */
            if (proto_flags & AP_FILTER_PROTO_CHANGE) {
                apr_table_unset(r->headers_out, "Content-MD5");
                apr_table_unset(r->headers_out, "ETag");
                if (proto_flags & AP_FILTER_PROTO_CHANGE_LENGTH) {
                    apr_table_unset(r->headers_out, "Content-Length");
                }
            }

            /* no-cache is for a filter that has different effect per-hit */
            if (proto_flags & AP_FILTER_PROTO_NO_CACHE) {
                apr_table_unset(r->headers_out, "Last-Modified");
                apr_table_addn(r->headers_out, "Cache-Control", "no-cache");
            }

            if (proto_flags & AP_FILTER_PROTO_NO_BYTERANGE) {
                apr_table_unset(r->headers_out, "Accept-Ranges");
            }
            else if (rctx && rctx->range) {
                /* restore range header we saved earlier */
                apr_table_setn(r->headers_in, "Range", rctx->range);
                rctx->range = NULL;
            }
#endif
            for (pctx = ctx->init_ctx; pctx; pctx = pctx->next) {
                if (pctx->provider == provider) {
                    ctx->fctx = pctx->ctx ;
                }
            }
            ctx->func = provider->frec->filter_func.out_func;
            return 1;
        }
    }

    /* No provider matched */
    return 0;
}

static apr_status_t filter_harness(ap_filter_t *f, apr_bucket_brigade *bb)
{
    apr_status_t ret;
    const char *cachecontrol;
    char *str;
    harness_ctx *ctx = f->ctx;
    ap_filter_rec_t *filter = f->frec;

    if (f->r->status != 200) {
        ap_remove_output_filter(f);
        return ap_pass_brigade(f->next, bb);
    }

    filter_trace(f->c, filter->debug, f->frec->name, bb);

    /* look up a handler function if we haven't already set it */
    if (!ctx->func) {
#ifndef NO_PROTOCOL
        if (f->r->proxyreq) {
            if (filter->proto_flags & AP_FILTER_PROTO_NO_PROXY) {
                ap_remove_output_filter(f);
                return ap_pass_brigade(f->next, bb);
            }

            if (filter->proto_flags & AP_FILTER_PROTO_TRANSFORM) {
                cachecontrol = apr_table_get(f->r->headers_out,
                                             "Cache-Control");
                if (cachecontrol) {
                    str = apr_pstrdup(f->r->pool,  cachecontrol);
                    ap_str_tolower(str);
                    if (strstr(str, "no-transform")) {
                        ap_remove_output_filter(f);
                        return ap_pass_brigade(f->next, bb);
                    }
                }
            }
        }
#endif
        if (!filter_lookup(f, filter)) {
            ap_remove_output_filter(f);
            return ap_pass_brigade(f->next, bb);
        }
    }

    /* call the content filter with its own context, then restore our
     * context
     */
    f->ctx = ctx->fctx;
    ret = ctx->func(f, bb);
    ctx->fctx = f->ctx;
    f->ctx = ctx;

    return ret;
}

#ifndef NO_PROTOCOL
static const char *filter_protocol(cmd_parms *cmd, void *CFG, const char *fname,
                                   const char *pname, const char *proto)
{
    static const char *sep = ";, \t";
    char *arg;
    char *tok = 0;
    unsigned int flags = 0;
    mod_filter_cfg *cfg = CFG;
    ap_filter_provider_t *provider = NULL;
    ap_filter_rec_t *filter = apr_hash_get(cfg->live_filters, fname,
                                           APR_HASH_KEY_STRING);

    if (!filter) {
        return "FilterProtocol: No such filter";
    }

    /* Fixup the args: it's really pname that's optional */
    if (proto == NULL) {
        proto = pname;
        pname = NULL;
    }
    else {
        /* Find provider */
        for (provider = filter->providers; provider; provider = provider->next){
            if (!strcasecmp(provider->frec->name, pname)) {
                break;
            }
        }
        if (!provider) {
            return "FilterProtocol: No such provider for this filter";
        }
    }

    /* Now set flags from our args */
    for (arg = apr_strtok(apr_pstrdup(cmd->pool, proto), sep, &tok);
         arg; arg = apr_strtok(NULL, sep, &tok)) {

        if (!strcasecmp(arg, "change=yes")) {
            flags |= AP_FILTER_PROTO_CHANGE | AP_FILTER_PROTO_CHANGE_LENGTH;
        }