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 * Portions of this software are based upon public domain software
 * originally written at the National Center for Supercomputing Applications,
 * University of Illinois, Urbana-Champaign.
 */

/*
 * mod_env.c
 * version 0.0.5
 * status beta
 * Pass environment variables to CGI/SSI scripts.
 * 
 * Andrew Wilson <Andrew.Wilson@cm.cf.ac.uk> 06.Dec.95
 *
 * Change log:
 * 08.Dec.95 Now allows PassEnv directive to appear more than once in
 *           conf files.
 * 10.Dec.95 optimisation.  getenv() only called at startup and used 
 *           to build a fast-to-access table.  apr_table_t used to build 
 *           per-server environment for each request.
 *           robustness.  better able to handle errors in configuration
 *           files:
 *           1)  PassEnv directive present, but no environment variable listed
 *           2)  PassEnv FOO present, but $FOO not present in environment
 *           3)  no PassEnv directive present
 * 23.Dec.95 Now allows SetEnv directive with same semantics as 'sh' setenv:
 *              SetEnv Var      sets Var to the empty string
 *              SetEnv Var Val  sets Var to the value Val
 *           Values containing whitespace should be quoted, eg:
 *              SetEnv Var "this is some text"
 *           Environment variables take their value from the last instance
 *           of PassEnv / SetEnv to be reached in the configuration file.
 *           For example, the sequence:
 *              PassEnv FOO
 *              SetEnv FOO override
 *           Causes FOO to take the value 'override'.
 * 23.Feb.96 Added UnsetEnv directive to allow environment variables
 *           to be removed.
 *           Virtual hosts now 'inherit' parent server environment which
 *           they're able to overwrite with their own directives or
 *           selectively ignore with UnsetEnv.
 *       *** IMPORTANT - the way that virtual hosts inherit their ***
 *       *** environment variables from the default server's      ***
 *       *** configuration has changed.  You should test your     ***
 *       *** configuration carefully before accepting this        ***
 *       *** version of the module in a live webserver which used ***
 *       *** older versions of the module.                        ***
 */

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

#if APR_HAVE_STDLIB_H
#include <stdlib.h>
#endif

#include "ap_config.h"
#include "httpd.h"
#include "http_config.h"
#include "http_request.h"


typedef struct {
    apr_table_t *vars;
    const char *unsetenv;
    int vars_present;
} env_dir_config_rec;

module AP_MODULE_DECLARE_DATA env_module;

static void *create_env_dir_config(apr_pool_t *p, char *dummy)
{
    env_dir_config_rec *conf = apr_palloc(p, sizeof(*conf));

    conf->vars = apr_table_make(p, 50);
    conf->unsetenv = "";
    conf->vars_present = 0;

    return conf;
}

static void *merge_env_dir_configs(apr_pool_t *p, void *basev, void *addv)
{
    env_dir_config_rec *base = basev;
    env_dir_config_rec *add = addv;
    env_dir_config_rec *newconf = apr_palloc(p, sizeof(*newconf));

    apr_table_t *new_table;
    apr_table_entry_t *elts;
    apr_array_header_t *arr;

    int i;
    const char *uenv, *unset;

    /* 
     * new_table = copy_table( p, base->vars );
     * foreach $element ( @add->vars ) {
     *     table_set( new_table, $element.key, $element.val );
     * };
     * foreach $unsetenv ( @UNSETENV ) {
     *     table_unset( new_table, $unsetenv );
     * }
     */

    new_table = apr_table_copy(p, base->vars);

    arr = apr_table_elts(add->vars);
    elts = (apr_table_entry_t *)arr->elts;

    for (i = 0; i < arr->nelts; ++i) {
        apr_table_setn(new_table, elts[i].key, elts[i].val);
    }

    unset = add->unsetenv;
    uenv = ap_getword_conf(p, &unset);
    while (uenv[0] != '\0') {
        apr_table_unset(new_table, uenv);
        uenv = ap_getword_conf(p, &unset);
    }

    newconf->vars = new_table;

    newconf->vars_present = base->vars_present || add->vars_present;

    return newconf;
}

static const char *add_env_module_vars_passed(cmd_parms *cmd, void *sconf_,
                                              const char *arg)
{
    env_dir_config_rec *sconf = sconf_;
    apr_table_t *vars = sconf->vars;
    char *env_var;
    char *name_ptr;

    while (*arg) {
        name_ptr = ap_getword_conf(cmd->pool, &arg);
        env_var = getenv(name_ptr);
        if (env_var != NULL) {
            sconf->vars_present = 1;
            apr_table_setn(vars, name_ptr, apr_pstrdup(cmd->pool, env_var));
        }
    }
    return NULL;
}

static const char *add_env_module_vars_set(cmd_parms *cmd, void *sconf_,
                                           const char *arg)
{
    env_dir_config_rec *sconf = sconf_;
    apr_table_t *vars = sconf->vars;
    char *name, *value;

    name = ap_getword_conf(cmd->pool, &arg);
    value = ap_getword_conf(cmd->pool, &arg);

    /* name is mandatory, value is optional.  no value means
     * set the variable to an empty string
     */


    if ((*name == '\0') || (*arg != '\0')) {
        return "SetEnv takes one or two arguments.  An environment variable name and an optional value to pass to CGI.";
    }

    sconf->vars_present = 1;
    apr_table_setn(vars, name, value);

    return NULL;
}

static const char *add_env_module_vars_unset(cmd_parms *cmd, void *sconf_,
                                             const char *arg)
{
    env_dir_config_rec *sconf = sconf_;

    sconf->unsetenv = sconf->unsetenv
        ? apr_pstrcat(cmd->pool, sconf->unsetenv, " ", arg, NULL)
        : arg;

    return NULL;
}

static const command_rec env_module_cmds[] =
{
AP_INIT_RAW_ARGS("PassEnv", add_env_module_vars_passed, NULL,
     OR_FILEINFO, "a list of environment variables to pass to CGI."),
AP_INIT_RAW_ARGS("SetEnv", add_env_module_vars_set, NULL,
     OR_FILEINFO, "an environment variable name and a value to pass to CGI."),
AP_INIT_RAW_ARGS("UnsetEnv", add_env_module_vars_unset, NULL,
     OR_FILEINFO, "a list of variables to remove from the CGI environment."),
    {NULL},
};

static int fixup_env_module(request_rec *r)
{
    apr_table_t *e = r->subprocess_env;
    env_dir_config_rec *sconf = ap_get_module_config(r->per_dir_config,
                                                     &env_module);
    apr_table_t *vars = sconf->vars;

    if (!sconf->vars_present)
        return DECLINED;

    r->subprocess_env = apr_table_overlay(r->pool, e, vars);

    return OK;
}

static void register_hooks(apr_pool_t *p)
{
    ap_hook_fixups(fixup_env_module, NULL, NULL, APR_HOOK_MIDDLE);
}

module AP_MODULE_DECLARE_DATA env_module =
{
    STANDARD20_MODULE_STUFF,
    create_env_dir_config,      /* dir config creater */
    merge_env_dir_configs,      /* dir merger --- default is to override */
    NULL,                       /* server config */
    NULL,                       /* merge server configs */
    env_module_cmds,            /* command apr_table_t */
    register_hooks              /* register hooks */
};
