mod_userdir.c

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/* 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_userdir... implement the UserDir command.  Broken away from the
 * Alias stuff for a couple of good and not-so-good reasons:
 *
 * 1) It shows a real minimal working example of how to do something like
 *    this.
 * 2) I know people who are actually interested in changing this *particular*
 *    aspect of server functionality without changing the rest of it.  That's
 *    what this whole modular arrangement is supposed to be good at...
 *
 * Modified by Alexei Kosut to support the following constructs
 * (server running at www.foo.com, request for /~bar/one/two.html)
 *
 * UserDir public_html      -> ~bar/public_html/one/two.html
 * UserDir /usr/web         -> /usr/web/bar/one/two.html
 * UserDir /home/ * /www     -> /home/bar/www/one/two.html
 *  NOTE: theses ^ ^ space only added allow it to work in a comment, ignore
 * UserDir http://x/users   -> (302) http://x/users/bar/one/two.html
 * UserDir http://x/ * /y     -> (302) http://x/bar/y/one/two.html
 *  NOTE: here also ^ ^
 *
 * In addition, you can use multiple entries, to specify alternate
 * user directories (a la Directory Index). For example:
 *
 * UserDir public_html /usr/web http://www.xyz.com/users
 *
 * Modified by Ken Coar to provide for the following:
 *
 * UserDir disable[d] username ...
 * UserDir enable[d] username ...
 *
 * If "disabled" has no other arguments, *all* ~<username> references are
 * disabled, except those explicitly turned on with the "enabled" keyword.
 */

#include "httpd.h"
#include "http_config.h"

module userdir_module;

typedef struct userdir_config {
    int globally_disabled;
    char *userdir;
    table *enabled_users;
    table *disabled_users;
} userdir_config;

/*
 * Server config for this module: global disablement flag, a list of usernames
 * ineligible for UserDir access, a list of those immune to global (but not
 * explicit) disablement, and the replacement string for all others.
 */

static void *create_userdir_config(pool *p, server_rec *s)
{
    userdir_config *newcfg;

    newcfg = (userdir_config *) ap_pcalloc(p, sizeof(userdir_config));
    newcfg->globally_disabled = 0;
    newcfg->userdir = DEFAULT_USER_DIR;
    newcfg->enabled_users = ap_make_table(p, 4);
    newcfg->disabled_users = ap_make_table(p, 4);
    return (void *) newcfg;
}

#define O_DEFAULT 0
#define O_ENABLE 1
#define O_DISABLE 2

static const char *set_user_dir(cmd_parms *cmd, void *dummy, char *arg)
{
    userdir_config *s_cfg;
    char *username;
    const char *usernames = arg;
    char *kw = ap_getword_conf(cmd->pool, &usernames);
    table *usertable;

    s_cfg = (userdir_config *) ap_get_module_config(cmd->server->module_config,
                                                    &userdir_module);
    /*
     * Let's do the comparisons once.
     */
    if ((!strcasecmp(kw, "disable")) || (!strcasecmp(kw, "disabled"))) {
        /*
         * If there are no usernames specified, this is a global disable - we
         * need do no more at this point than record the fact.
         */
        if (strlen(usernames) == 0) {
            s_cfg->globally_disabled = 1;
            return NULL;
        }
        usertable = s_cfg->disabled_users;
    }
    else if ((!strcasecmp(kw, "enable")) || (!strcasecmp(kw, "enabled"))) {
        /*
         * The "disable" keyword can stand alone or take a list of names, but
         * the "enable" keyword requires the list.  Whinge if it doesn't have
         * it.
         */
        if (strlen(usernames) == 0) {
            return "UserDir \"enable\" keyword requires a list of usernames";
        }
        usertable = s_cfg->enabled_users;
    }
    else {
        /*
         * If the first (only?) value isn't one of our keywords, look at each
         * config 'word' for validity and copy the entire arg to the userdir 
         * if all paths are valid.
         */
        const char *userdirs = arg;
        while (*userdirs) {
            char *thisdir = ap_getword_conf(cmd->pool, &userdirs);
            if (!ap_os_is_path_absolute(thisdir) && !strchr(thisdir, ':')) {
#if defined(WIN32) || defined(NETWARE)
                return "UserDir must specify an absolute redirect "
                       "or absolute file path";
#else
                if (strchr(thisdir, '*')) {
                     return "UserDir cannot specify '*' substitution within "
                            "a relative path";
                }
#endif
            }
        }
        s_cfg->userdir = ap_pstrdup(cmd->pool, arg);
#if defined(WIN32) || defined(OS2) || defined(NETWARE)
        /* These are incomplete paths, so we cannot canonicalize them yet.
         * but any backslashes will confuse the parser, later, so simply
         * change them to slash form.
         */
        arg = s_cfg->userdir;
        while (arg = strchr(arg, '\\')) {
            *(arg++) = '/';
        }
#endif
        return NULL;
    }
    /*
     * Now we just take each word in turn from the command line and add it to
     * the appropriate table.
     */
    while (*usernames) {
        username = ap_getword_conf(cmd->pool, &usernames);
        ap_table_setn(usertable, username, kw);
    }
    return NULL;
}

static const command_rec userdir_cmds[] =
{
    {"UserDir", set_user_dir, NULL, RSRC_CONF, RAW_ARGS,
     "the public subdirectory in users' home directories, or "
     "'disabled', or 'disabled username username...', or "
     "'enabled username username...'"},
    {NULL}
};

static int translate_userdir(request_rec *r)
{
    void *server_conf = r->server->module_config;
    const userdir_config *s_cfg =
    (userdir_config *) ap_get_module_config(server_conf, &userdir_module);
    char *name = r->uri;
    const char *userdirs = s_cfg->userdir;
    const char *w, *dname;
    char *redirect;
    struct stat statbuf;

    /*
     * If the URI doesn't match our basic pattern, we've nothing to do with
     * it.
     */
    if ((s_cfg->userdir == NULL)
        || (name[0] != '/')
        || (name[1] != '~')) {
        return DECLINED;
    }

    dname = name + 2;
    w = ap_getword(r->pool, &dname, '/');

    /*
     * The 'dname' funny business involves backing it up to capture the '/'
     * delimiting the "/~user" part from the rest of the URL, in case there
     * was one (the case where there wasn't being just "GET /~user HTTP/1.0",
     * for which we don't want to tack on a '/' onto the filename).
     */

    if (dname[-1] == '/') {
        --dname;
    }

    /*
     * If there's no username, it's not for us.  Ignore . and .. as well.
     */
    if ((w[0] == '\0')
        || ((w[1] == '.')
            && ((w[2] == '\0')
                || ((w[2] == '.') && (w[3] == '\0'))))) {
        return DECLINED;
    }
    /*
     * Nor if there's an username but it's in the disabled list.
     */
    if (ap_table_get(s_cfg->disabled_users, w) != NULL) {
        return DECLINED;
    }
    /*
     * If there's a global interdiction on UserDirs, check to see if this
     * name is one of the Blessed.
     */
    if (s_cfg->globally_disabled
        && (ap_table_get(s_cfg->enabled_users, w) == NULL)) {
        return DECLINED;
    }

    /*
     * Special cases all checked, onward to normal substitution processing.
     */

    while (*userdirs) {
        const char *userdir = ap_getword_conf(r->pool, &userdirs);
        char *filename = NULL;
        int is_absolute = ap_os_is_path_absolute(userdir);

        if (strchr(userdir, '*')) {
            /* token '*' embedded:
             */
            char *x = ap_getword(r->pool, &userdir, '*');
            if (is_absolute) {
                /* token '*' within absolute path
                 * serves [UserDir arg-pre*][user][UserDir arg-post*]
                 * /somepath/ * /somedir + /~smith -> /somepath/smith/somedir
                 */
                filename = ap_pstrcat(r->pool, x, w, userdir, NULL);
            }
            else if (strchr(x, ':')) {
                /* token '*' within a redirect path
                 * serves [UserDir arg-pre*][user][UserDir arg-post*]
                 * http://server/user/ * + /~smith/foo ->
                 *   http://server/user/smith/foo
                 */
                redirect = ap_pstrcat(r->pool, x, w, userdir, dname, NULL);
                ap_table_setn(r->headers_out, "Location", redirect);
                return REDIRECT;
            }
            else {
                /* Not a redirect, not an absolute path, '*' token:
                 * serves [homedir]/[UserDir arg]
                 * something/ * /public_html
                 * Shouldn't happen, we trap for this in set_user_dir
                 */
                return DECLINED;
            }
        }
        else if (is_absolute) {
            /* An absolute path, no * token:
             * serves [UserDir arg]/[user]
             * /home + /~smith -> /home/smith
             */
            if (userdir[strlen(userdir) - 1] == '/')
                filename = ap_pstrcat(r->pool, userdir, w, NULL);
            else
                filename = ap_pstrcat(r->pool, userdir, "/", w, NULL);
        }
        else if (strchr(userdir, ':')) {
            /* A redirect, not an absolute path, no * token:
             * serves [UserDir arg]/[user][dname]
             * http://server/ + /~smith/foo -> http://server/smith/foo
             */
            if (userdir[strlen(userdir) - 1] == '/') {
                redirect = ap_pstrcat(r->pool, userdir, w, dname, NULL);
            }
            else {
                redirect = ap_pstrcat(r->pool, userdir, "/", w, dname, NULL);
            }
            ap_table_setn(r->headers_out, "Location", redirect);
            return REDIRECT;
        }
        else {
            /* Not a redirect, not an absolute path, no * token:
             * serves [homedir]/[UserDir arg]
             * e.g. /~smith -> /home/smith/public_html
             */
#if defined(WIN32) || defined(NETWARE)
            /* Need to figure out home dirs on NT and NetWare 
             * Shouldn't happen here, though, we trap for this in set_user_dir
             */
            return DECLINED;
#else                           /* WIN32 & NetWare */
            struct passwd *pw;
            if ((pw = getpwnam(w))) {
#ifdef OS2
                /* Need to manually add user name for OS/2 */
                filename = ap_pstrcat(r->pool, pw->pw_dir, w, "/",
                                      userdir, NULL);
#else
                filename = ap_pstrcat(r->pool, pw->pw_dir, "/",
                                      userdir, NULL);
#endif
            }
#endif                          /* WIN32 & NetWare */
        }

        /*
         * Now see if it exists, or we're at the last entry. If we are at the
         * last entry, then use the filename generated (if there is one)
         * anyway, in the hope that some handler might handle it. This can be
         * used, for example, to run a CGI script for the user.
         */
        if (filename && (!*userdirs || stat(filename, &statbuf) != -1)) {
            r->filename = ap_pstrcat(r->pool, filename, dname, NULL);
	    /* when statbuf contains info on r->filename we can save a syscall
	     * by copying it to r->finfo
	     */
	    if (*userdirs && dname[0] == 0) {
		r->finfo = statbuf;
            }
            return OK;
        }
    }

    return DECLINED;
}

module userdir_module = {
    STANDARD_MODULE_STUFF,
    NULL,                       /* initializer */
    NULL,                       /* dir config creater */
    NULL,                       /* dir merger --- default is to override */
    create_userdir_config,      /* server config */
    NULL,                       /* merge server config */
    userdir_cmds,               /* command table */
    NULL,                       /* handlers */
    translate_userdir,          /* filename translation */
    NULL,                       /* check_user_id */
    NULL,                       /* check auth */
    NULL,                       /* check access */
    NULL,                       /* type_checker */
    NULL,                       /* fixups */
    NULL,                       /* logger */
    NULL,                       /* header parser */
    NULL,                       /* child_init */
    NULL,                       /* child_exit */
    NULL                        /* post read-request */
};