path: root/modules/metadata/mod_headers.c

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 * Portions of this software are based upon public domain software
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 */

/*
 * mod_headers.c: Add/append/remove HTTP response headers
 *     Written by Paul Sutton, paul@ukweb.com, 1 Oct 1996
 *
 * HeaderIn and HeaderOut can be used to add/replace/remove HTTP headers.
 * Valid in both per-server and per-dir configurations.
 *
 * Syntax is:
 *
 *   HeaderIn action header value
 *   HeaderOut 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
 *     unset  - remove this header
 *
 * Where action is unset, the third argument (value) should not be given.
 * The header name can include the colon, or not.
 *
 * The Header(In|Out) directive 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:
 *
 *   HeaderOut append Author "John P. Doe"
 *   HeaderOut unset Author
 *
 * Examples:
 *
 *  To set the "Author" header, use
 *     HeaderOut add Author "John P. Doe"
 *
 *  To remove a header:
 *     HeaderOut unset Author
 *
 */

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

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_unset = 'u'             /* unset header */
} hdr_actions;

typedef enum {
    hdr_in = 0,                 /* HeaderIn */
    hdr_out = 1,                /* HeaderOut */
} hdr_inout;

typedef struct {
    hdr_actions action;
    char *header;
    const char *value;
} header_entry;

/*
 * 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;
} headers_conf;

module AP_MODULE_DECLARE_DATA headers_module;

static void *create_headers_config(apr_pool_t *p, server_rec *s)
{
    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));

    return conf;
}

static void *create_headers_dir_config(apr_pool_t *p, char *d)
{
    return create_headers_config(p, NULL);
}

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);

    return newconf;
}


/* handle HeaderIn and HeaderOut directive */
static const char *header_inout_cmd(hdr_inout inout, cmd_parms *cmd, void *indirconf,
                              const char *action, const char *inhdr,
                              const char *value)
{
    headers_conf *dirconf = indirconf;
    char *hdr = apr_pstrdup(cmd->pool, inhdr);
    header_entry *new;
    server_rec *s = cmd->server;
    headers_conf *serverconf = ap_get_module_config(s->module_config,
                                                    &headers_module);
    char *colon;

    if (cmd->path) {
        new = (header_entry *) apr_array_push((hdr_in == inout) ? dirconf->fixup_in : dirconf->fixup_out);
    }
    else {
        new = (header_entry *) apr_array_push((hdr_in == inout) ? serverconf->fixup_in : serverconf->fixup_out);
    }

    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, "unset"))
        new->action = hdr_unset;
    else
        return "first argument must be add, set, append or unset.";

    if (new->action == hdr_unset) {
        if (value)
            return "Header(In|Out) unset takes two arguments";
    }
    else if (!value)
        return "Header(In|Out) requires three arguments";

    if ((colon = strchr(hdr, ':')))
        *colon = '\0';

    new->header = hdr;
    new->value = value;

    return NULL;
}

/* handle deprecated Header directive */
static const char *header_cmd(cmd_parms *cmd, void *indirconf,
                              const char *action, const char *inhdr,
                              const char *value)
{
    return "The Header directive has been deprecated. Use HeaderOut instead.";
}

/* handle HeaderOut directive */
static const char *header_out_cmd(cmd_parms *cmd, void *indirconf,
                              const char *action, const char *inhdr,
                              const char *value)
{
    return header_inout_cmd(hdr_out, cmd, indirconf, action, inhdr, value);
}

/* handle HeaderIn directive */
static const char *header_in_cmd(cmd_parms *cmd, void *indirconf,
                              const char *action, const char *inhdr,
                              const char *value)
{
    return header_inout_cmd(hdr_in, cmd, indirconf, action, inhdr, value);
}


static void do_headers_fixup(apr_table_t *headers,
                             apr_array_header_t *fixup)
{
    int i;

    for (i = 0; i < fixup->nelts; ++i) {
        header_entry *hdr = &((header_entry *) (fixup->elts))[i];
        switch (hdr->action) {
        case hdr_add:
            apr_table_addn(headers, hdr->header, hdr->value);
            break;
        case hdr_append:
            apr_table_mergen(headers, hdr->header, hdr->value);
            break;
        case hdr_set:
            apr_table_setn(headers, hdr->header, hdr->value);
            break;
        case hdr_unset:
            apr_table_unset(headers, hdr->header);
            break;
        }
    }
}

static void ap_headers_insert_output_filter(request_rec *r)
{
    headers_conf *serverconf = ap_get_module_config(r->server->module_config,
                                                    &headers_module);
    headers_conf *dirconf = ap_get_module_config(r->per_dir_config,
                                                 &headers_module);

    if (serverconf->fixup_out->nelts || dirconf->fixup_out->nelts) {
	ap_add_output_filter("FIXUP_HEADERS_OUT", NULL, r, r->connection);
    }
}

static apr_status_t ap_headers_output_filter(ap_filter_t *f,
                                             apr_bucket_brigade *in)
{
    headers_conf *serverconf = ap_get_module_config(f->r->server->module_config,
                                                    &headers_module);
    headers_conf *dirconf = ap_get_module_config(f->r->per_dir_config,
                                                 &headers_module);

    ap_log_error(APLOG_MARK, APLOG_DEBUG|APLOG_NOERRNO, 0, f->r->server,
		 "headers: ap_headers_output_filter()");

    /* do the fixup */
    do_headers_fixup(f->r->headers_out, serverconf->fixup_out);
    do_headers_fixup(f->r->headers_out, dirconf->fixup_out);

    /* remove ourselves from the filter chain */
    ap_remove_output_filter(f);

    /* send the data up the stack */
    return ap_pass_brigade(f->next,in);
}

static apr_status_t ap_headers_fixup(request_rec *r)
{
    headers_conf *serverconf = ap_get_module_config(r->server->module_config,
                                                    &headers_module);
    headers_conf *dirconf = ap_get_module_config(r->per_dir_config,
                                                 &headers_module);

    /* do the fixup */
    if (serverconf->fixup_in->nelts || dirconf->fixup_in->nelts) {
        do_headers_fixup(r->headers_in, serverconf->fixup_in);
        do_headers_fixup(r->headers_in, dirconf->fixup_in);
    }

    return DECLINED;
}
                                        
static const command_rec headers_cmds[] =
{
    AP_INIT_TAKE23("Header", header_cmd, NULL, OR_FILEINFO,
                   "deprecated, use HeaderOut instead"),
    AP_INIT_TAKE23("HeaderIn", header_in_cmd, NULL, OR_FILEINFO,
                   "an action, header and value"),
    AP_INIT_TAKE23("HeaderOut", header_out_cmd, NULL, OR_FILEINFO,
                   "an action, header and value"),
    {NULL}
};

static void register_hooks(apr_pool_t *p)
{
    ap_hook_insert_filter(ap_headers_insert_output_filter, NULL, NULL, APR_HOOK_LAST);
    ap_hook_fixups(ap_headers_fixup, NULL, NULL, APR_HOOK_LAST);
    ap_register_output_filter("FIXUP_HEADERS_OUT", ap_headers_output_filter, AP_FTYPE_CONTENT);
}

module AP_MODULE_DECLARE_DATA headers_module =
{
    STANDARD20_MODULE_STUFF,
    create_headers_dir_config,  /* dir config creater */
    merge_headers_config,       /* dir merger --- default is to override */
    create_headers_config,      /* server config */
    merge_headers_config,       /* merge server configs */
    headers_cmds,               /* command apr_table_t */
    register_hooks		/* register hooks */
};