mod_headers.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.
 */

/*
 * mod_headers.c: Add/append/remove HTTP response headers
 *     Written by Paul Sutton, [e-mail], 1 Oct 1996
 *
 * The Header directive can be used to add/replace/remove HTTP headers
 * within the response message.  The RequestHeader directive can be used
 * to add/replace/remove HTTP headers before a request message is processed.
 * Valid in both per-server and per-dir configurations.
 *
 * Syntax is:
 *
 *   Header action header value
 *   RequestHeader action header value
 *
 * Where action is one of:
 *     set    - set this header, replacing any old value
 *     add    - add this header, possible resulting in two or more
 *              headers with the same name
 *     append - append this text onto any existing header of this same
 *     merge  - merge this text onto any existing header of this same,
 *              avoiding duplicate values
 *     unset  - remove this header
 *      edit  - transform the header value according to a regexp
 *
 * Where action is unset, the third argument (value) should not be given.
 * The header name can include the colon, or not.
 *
 * The Header and RequestHeader directives can only be used where allowed
 * by the FileInfo override.
 *
 * When the request is processed, the header directives are processed in
 * this order: firstly, the main server, then the virtual server handling
 * this request (if any), then any <Directory> sections (working downwards
 * from the root dir), then an <Location> sections (working down from
 * shortest URL component), the any <File> sections. This order is
 * important if any 'set' or 'unset' actions are used. For example,
 * the following two directives have different effect if applied in
 * the reverse order:
 *
 *   Header append Author "John P. Doe"
 *   Header unset Author
 *
 * Examples:
 *
 *  To set the "Author" header, use
 *     Header add Author "John P. Doe"
 *
 *  To remove a header:
 *     Header unset Author
 *
 */

#include "apr.h"
#include "apr_lib.h"
#include "apr_strings.h"
#include "apr_buckets.h"

#include "apr_hash.h"
#define APR_WANT_STRFUNC
#include "apr_want.h"

#include "httpd.h"
#include "http_config.h"
#include "http_request.h"
#include "http_log.h"
#include "util_filter.h"
#include "http_protocol.h"

#include "mod_ssl.h" /* for the ssl_var_lookup optional function defn */

/* format_tag_hash is initialized during pre-config */
static apr_hash_t *format_tag_hash;

typedef enum {
    hdr_add = 'a',              /* add header (could mean multiple hdrs) */
    hdr_set = 's',              /* set (replace old value) */
    hdr_append = 'm',           /* append (merge into any old value) */
    hdr_merge = 'g',            /* merge (merge, but avoid duplicates) */
    hdr_unset = 'u',            /* unset header */
    hdr_echo = 'e',             /* echo headers from request to response */
    hdr_edit = 'r'              /* change value by regexp */
} hdr_actions;

/*
 * magic cmd->info values
 */
static char hdr_in  = '0';  /* RequestHeader */
static char hdr_out = '1';  /* Header onsuccess */
static char hdr_err = '2';  /* Header always */

/*
 * There is an array of struct format_tag per Header/RequestHeader
 * config directive
 */
typedef struct {
    const char* (*func)(request_rec *r,char *arg);
    char *arg;
} format_tag;

/* 'Magic' condition_var value to run action in post_read_request */
static const char* condition_early = "early";
/*
 * There is one "header_entry" per Header/RequestHeader config directive
 */
typedef struct {
    hdr_actions action;
    const char *header;
    apr_array_header_t *ta;   /* Array of format_tag structs */
    ap_regex_t *regex;
    const char *condition_var;
    const char *subs;
} header_entry;

/* echo_do is used for Header echo to iterate through the request headers*/
typedef struct {
    request_rec *r;
    header_entry *hdr;
} echo_do;

/* edit_do is used for Header edit to iterate through the request headers */
typedef struct {
    apr_pool_t *p;
    header_entry *hdr;
    apr_table_t *t;
} edit_do;

/*
 * headers_conf is our per-module configuration. This is used as both
 * a per-dir and per-server config
 */
typedef struct {
    apr_array_header_t *fixup_in;
    apr_array_header_t *fixup_out;
    apr_array_header_t *fixup_err;
} headers_conf;

module AP_MODULE_DECLARE_DATA headers_module;

/* Pointer to ssl_var_lookup, if available. */
static APR_OPTIONAL_FN_TYPE(ssl_var_lookup) *header_ssl_lookup = NULL;

/*
 * Tag formatting functions
 */
static const char *constant_item(request_rec *r, char *stuff)
{
    return stuff;
}
static const char *header_request_duration(request_rec *r, char *a)
{
    return apr_psprintf(r->pool, "D=%" APR_TIME_T_FMT,
                        (apr_time_now() - r->request_time));
}
static const char *header_request_time(request_rec *r, char *a)
{
    return apr_psprintf(r->pool, "t=%" APR_TIME_T_FMT, r->request_time);
}

/* unwrap_header returns HDR with any newlines converted into
 * whitespace if necessary. */
static const char *unwrap_header(apr_pool_t *p, const char *hdr)
{
    if (ap_strchr_c(hdr, APR_ASCII_LF) || ap_strchr_c(hdr, APR_ASCII_CR)) {
        char *ptr;

        hdr = ptr = apr_pstrdup(p, hdr);

        do {
            if (*ptr == APR_ASCII_LF || *ptr == APR_ASCII_CR)
                *ptr = APR_ASCII_BLANK;
        } while (*ptr++);
    }
    return hdr;
}

static const char *header_request_env_var(request_rec *r, char *a)
{
    const char *s = apr_table_get(r->subprocess_env,a);

    if (s)
        return unwrap_header(r->pool, s);
    else
        return "(null)";
}

static const char *header_request_ssl_var(request_rec *r, char *name)
{
    if (header_ssl_lookup) {
        const char *val = header_ssl_lookup(r->pool, r->server,
                                            r->connection, r, name);
        if (val && val[0])
            return unwrap_header(r->pool, val);
        else
            return "(null)";
    }
    else {
        return "(null)";
    }
}

/*
 * Config routines
 */

static void *create_headers_dir_config(apr_pool_t *p, char *d)
{
    headers_conf *conf = apr_pcalloc(p, sizeof(*conf));

    conf->fixup_in = apr_array_make(p, 2, sizeof(header_entry));
    conf->fixup_out = apr_array_make(p, 2, sizeof(header_entry));
    conf->fixup_err = apr_array_make(p, 2, sizeof(header_entry));

    return conf;
}

static void *merge_headers_config(apr_pool_t *p, void *basev, void *overridesv)
{
    headers_conf *newconf = apr_pcalloc(p, sizeof(*newconf));
    headers_conf *base = basev;
    headers_conf *overrides = overridesv;

    newconf->fixup_in = apr_array_append(p, base->fixup_in,
                                         overrides->fixup_in);
    newconf->fixup_out = apr_array_append(p, base->fixup_out,
                                          overrides->fixup_out);
    newconf->fixup_err = apr_array_append(p, base->fixup_err,
                                          overrides->fixup_err);

    return newconf;
}

static char *parse_misc_string(apr_pool_t *p, format_tag *tag, const char **sa)
{
    const char *s;
    char *d;

    tag->func = constant_item;

    s = *sa;
    while (*s && *s != '%') {
        s++;
    }
    /*
     * This might allocate a few chars extra if there's a backslash
     * escape in the format string.
     */
    tag->arg = apr_palloc(p, s - *sa + 1);

    d = tag->arg;
    s = *sa;
    while (*s && *s != '%') {
        if (*s != '\\') {
            *d++ = *s++;
        }
        else {
            s++;
            switch (*s) {
            case '\\':
                *d++ = '\\';
                s++;
                break;
            case 'r':
                *d++ = '\r';
                s++;
                break;
            case 'n':
                *d++ = '\n';
                s++;
                break;
            case 't':
                *d++ = '\t';
                s++;
                break;
            default:
                /* copy verbatim */
                *d++ = '\\';
                /*
                 * Allow the loop to deal with this *s in the normal
                 * fashion so that it handles end of string etc.
                 * properly.
                 */
                break;
            }
        }
    }
    *d = '\0';

    *sa = s;
    return NULL;
}

static char *parse_format_tag(apr_pool_t *p, format_tag *tag, const char **sa)
{
    const char *s = *sa;
    const char * (*tag_handler)(request_rec *,char *);

    /* Handle string literal/conditionals */
    if (*s != '%') {
        return parse_misc_string(p, tag, sa);
    }
    s++; /* skip the % */

    /* Pass through %% or % at end of string as % */
    if ((*s == '%') || (*s == '\0')) {
        tag->func = constant_item;
        tag->arg = "%";
        if (*s)
            s++;
        *sa = s;
        return NULL;
    }

    tag->arg = '\0';
    /* grab the argument if there is one */
    if (*s == '{') {
        ++s;
        tag->arg = ap_getword(p,&s,'}');
    }

    tag_handler = (const char * (*)(request_rec *,char *))apr_hash_get(format_tag_hash, s++, 1);

    if (!tag_handler) {
        char dummy[2];
        dummy[0] = s[-1];
        dummy[1] = '\0';
        return apr_pstrcat(p, "Unrecognized header format %", dummy, NULL);
    }
    tag->func = tag_handler;

    *sa = s;
    return NULL;
}

/*
 * A format string consists of white space, text and optional format
 * tags in any order. E.g.,
 *
 * Header add MyHeader "Free form text %D %t more text"
 *
 * Decompose the format string into its tags. Each tag (struct format_tag)
 * contains a pointer to the function used to format the tag. Then save each
 * tag in the tag array anchored in the header_entry.
 */
static char *parse_format_string(apr_pool_t *p, header_entry *hdr, const char *s)
{
    char *res;

    /* No string to parse with unset and echo commands */
    if (hdr->action == hdr_unset ||
        hdr->action == hdr_edit ||
        hdr->action == hdr_echo) {
        return NULL;
    }

    hdr->ta = apr_array_make(p, 10, sizeof(format_tag));

    while (*s) {
        if ((res = parse_format_tag(p, (format_tag *) apr_array_push(hdr->ta), &s))) {
            return res;
        }
    }
    return NULL;
}

/* handle RequestHeader and Header directive */
static APR_INLINE const char *header_inout_cmd(cmd_parms *cmd,
                                               void *indirconf,
                                               const char *action,
                                               const char *hdr,
                                               const char *value,
                                               const char *subs,
                                               const char *envclause)
{
    headers_conf *dirconf = indirconf;
    const char *condition_var = NULL;
    const char *colon;
    header_entry *new;

    apr_array_header_t *fixup = (cmd->info == &hdr_in)
        ? dirconf->fixup_in   : (cmd->info == &hdr_err)
        ? dirconf->fixup_err
        : dirconf->fixup_out;

    new = (header_entry *) apr_array_push(fixup);

    if (!strcasecmp(action, "set"))
        new->action = hdr_set;
    else if (!strcasecmp(action, "add"))
        new->action = hdr_add;
    else if (!strcasecmp(action, "append"))
        new->action = hdr_append;
    else if (!strcasecmp(action, "merge"))
        new->action = hdr_merge;
    else if (!strcasecmp(action, "unset"))
        new->action = hdr_unset;
    else if (!strcasecmp(action, "echo"))
        new->action = hdr_echo;
    else if (!strcasecmp(action, "edit"))
        new->action = hdr_edit;
    else
        return "first argument must be 'add', 'set', 'append', 'merge', "
               "'unset', 'echo', or 'edit'.";

    if (new->action == hdr_edit) {
        if (subs == NULL) {
            return "Header edit requires a match and a substitution";
        }
        new->regex = ap_pregcomp(cmd->pool, value, AP_REG_EXTENDED);
        if (new->regex == NULL) {
            return "Header edit regex could not be compiled";
        }
        new->subs = subs;
    }
    else {
        /* there's no subs, so envclause is really that argument */
        if (envclause != NULL) {
            return "Too many arguments to directive";
        }
        envclause = subs;
    }
    if (new->action == hdr_unset) {
        if (value) {
            if (envclause) {