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/*
 * 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.  table 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 "httpd.h"
#include "http_config.h"

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

module MODULE_VAR_EXPORT env_module;

static void *create_env_dir_config(pool *p, char *dummy)
{
    env_dir_config_rec *new =
    (env_dir_config_rec *) ap_palloc(p, sizeof(env_dir_config_rec));
    new->vars = ap_make_table(p, 50);
    new->unsetenv = "";
    new->vars_present = 0;
    return (void *) new;
}

static void *merge_env_dir_configs(pool *p, void *basev, void *addv)
{
    env_dir_config_rec *base = (env_dir_config_rec *) basev;
    env_dir_config_rec *add = (env_dir_config_rec *) addv;
    env_dir_config_rec *new =
    (env_dir_config_rec *) ap_palloc(p, sizeof(env_dir_config_rec));

    table *new_table;
    table_entry *elts;
    array_header *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 = ap_copy_table(p, base->vars);

    arr = ap_table_elts(add->vars);
    elts = (table_entry *)arr->elts;

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

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

    new->vars = new_table;

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

    return new;
}

static const char *add_env_module_vars_passed(cmd_parms *cmd,
					      env_dir_config_rec *sconf,
                                              const char *arg)
{
    table *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;
            ap_table_setn(vars, name_ptr, ap_pstrdup(cmd->pool, env_var));
        }
    }
    return NULL;
}

static const char *add_env_module_vars_set(cmd_parms *cmd,
					   env_dir_config_rec *sconf,
                                           const char *arg)
{
    table *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;
    ap_table_setn(vars, name, value);

    return NULL;
}

static const char *add_env_module_vars_unset(cmd_parms *cmd,
					     env_dir_config_rec *sconf,
                                             char *arg)
{
    sconf->unsetenv = sconf->unsetenv ?
        ap_pstrcat(cmd->pool, sconf->unsetenv, " ", arg, NULL) :
         arg;
    return NULL;
}

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

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

    if (!sconf->vars_present)
        return DECLINED;

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

    return OK;
}

module MODULE_VAR_EXPORT env_module =
{
    STANDARD_MODULE_STUFF,
    NULL,                       /* initializer */
    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 table */
    NULL,                       /* handlers */
    NULL,                       /* filename translation */
    NULL,                       /* check_user_id */
    NULL,                       /* check auth */
    NULL,                       /* check access */
    NULL,                       /* type_checker */
    fixup_env_module,           /* fixups */
    NULL,                       /* logger */
    NULL,                       /* header parser */
    NULL,                       /* child_init */
    NULL,                       /* child_exit */
    NULL                        /* post read-request */
};
