tinyproxy/src/htmlerror.c

/* tinyproxy - A fast light-weight HTTP proxy
 * Copyright (C) 2003 Steven Young <sdyoung@miranda.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

/* This file contains source code for the handling and display of
 * HTML error pages with variable substitution.
 */

#include "tinyproxy.h"

#include "common.h"
#include "buffer.h"
#include "conns.h"
#include "heap.h"
#include "htmlerror.h"
#include "network.h"
#include "utils.h"

/*
 * Add an error number -> filename mapping to the errorpages list.
 */
#define ERRORNUM_BUFSIZE 8      /* this is more than required */
#define ERRPAGES_BUCKETCOUNT 16

int
add_new_errorpage(char *filepath, unsigned int errornum)
{
        char errornbuf[ERRORNUM_BUFSIZE];

        config.errorpages = hashmap_create(ERRPAGES_BUCKETCOUNT);
        if (!config.errorpages)
                return (-1);

        snprintf(errornbuf, ERRORNUM_BUFSIZE, "%u", errornum);

        if (hashmap_insert(config.errorpages, errornbuf,
                           filepath, strlen(filepath) + 1) < 0)
                return (-1);

        return (0);
}

/*
 * Get the file appropriate for a given error.
 */
static char *
get_html_file(unsigned int errornum)
{
        hashmap_iter result_iter;
        char errornbuf[ERRORNUM_BUFSIZE];
        char *key;
        static char *val;

        assert(errornum >= 100 && errornum < 1000);

        if (!config.errorpages)
                return (config.errorpage_undef);

        snprintf(errornbuf, ERRORNUM_BUFSIZE, "%u", errornum);

        result_iter = hashmap_find(config.errorpages, errornbuf);

        if (hashmap_is_end(config.errorpages, result_iter))
                return (config.errorpage_undef);

        if (hashmap_return_entry(config.errorpages, result_iter,
                                 &key, (void **)&val) < 0)
                return (config.errorpage_undef);

        return (val);
}

/*
 * Look up the value for a variable.
 */
static char *
lookup_variable(struct conn_s *connptr, char *varname)
{
        hashmap_iter result_iter;
        char *key;
        static char *data;

        result_iter = hashmap_find(connptr->error_variables, varname);

        if (hashmap_is_end(connptr->error_variables, result_iter))
                return (NULL);

        if (hashmap_return_entry(connptr->error_variables, result_iter,
                                 &key, (void **)&data) < 0)
                return (NULL);

        return (data);
}

#define HTML_BUFSIZE 4096

/*
 * Send an already-opened file to the client with variable substitution.
 */
int
send_html_file(FILE * infile, struct conn_s *connptr)
{
        char inbuf[HTML_BUFSIZE], *varstart = NULL, *p;
        char *varval;
        int in_variable = 0, writeret;

        while (fgets(inbuf, HTML_BUFSIZE, infile) != NULL) {
                for (p = inbuf; *p; p++) {
                        switch (*p) {
                        case '}':
                                if (in_variable) {
                                        *p = '\0';
                                        if (!
                                            (varval =
                                             lookup_variable(connptr,
                                                             varstart)))
                                                varval = "(unknown)";
                                        writeret =
                                            write_message(connptr->client_fd,
                                                          "%s", varval);
                                        if (writeret)
                                                return (writeret);
                                        in_variable = 0;
                                } else {
                                        writeret =
                                            write_message(connptr->client_fd,
                                                          "%c", *p);
                                        if (writeret)
                                                return (writeret);
                                }
                                break;
                        case '{':
                                /* a {{ will print a single {.  If we are NOT
                                 * already in a { variable, then proceed with
                                 * setup.  If we ARE already in a { variable,
                                 * this code will fallthrough to the code that
                                 * just dumps a character to the client fd.
                                 */
                                if (!in_variable) {
                                        varstart = p + 1;
                                        in_variable++;
                                } else
                                        in_variable = 0;
                        default:
                                if (!in_variable) {
                                        writeret =
                                            write_message(connptr->client_fd,
                                                          "%c", *p);
                                        if (writeret)
                                                return (writeret);
                                }

                        }
                }
                in_variable = 0;
        }
        return (0);
}

int
send_http_headers(struct conn_s *connptr, int code, char *message)
{
        char *headers =
            "HTTP/1.0 %d %s\r\n"
            "Server: %s/%s\r\n"
            "Content-Type: text/html\r\n" "Connection: close\r\n" "\r\n";

        return (write_message(connptr->client_fd, headers,
                              code, message, PACKAGE, VERSION));
}

/*
 * Display an error to the client.
 */
int
send_http_error_message(struct conn_s *connptr)
{
        char *error_file;
        FILE *infile;
        int ret;
        char *fallback_error =
            "<html><head><title>%s</title></head>"
            "<body><blockquote><i>%s %s</i><br>"
            "The page you requested was unavailable. The error code is listed "
            "below. In addition, the HTML file which has been configured as the "
            "page to be displayed when an error of this type was unavailable, "
            "with the error code %d (%s).  Please contact your administrator."
            "<center>%s</center>" "</body></html>" "\r\n";

        send_http_headers(connptr, connptr->error_number,
                          connptr->error_string);

        error_file = get_html_file(connptr->error_number);
        if (!(infile = fopen(error_file, "r")))
                return (write_message(connptr->client_fd, fallback_error,
                                      connptr->error_string,
                                      PACKAGE, VERSION,
                                      errno, strerror(errno),
                                      connptr->error_string));

        ret = send_html_file(infile, connptr);
        fclose(infile);
        return (ret);
}

/*
 * Add a key -> value mapping for HTML file substitution.
 */

#define ERRVAR_BUCKETCOUNT 16

int
add_error_variable(struct conn_s *connptr, char *key, char *val)
{
        if (!connptr->error_variables)
                if (!
                    (connptr->error_variables =
                     hashmap_create(ERRVAR_BUCKETCOUNT)))
                        return (-1);

        if (hashmap_insert(connptr->error_variables, key, val,
                           strlen(val) + 1) < 0)
                return (-1);

        return (0);
}

#define ADD_VAR_RET(x, y) if(y) { if(add_error_variable(connptr, x, y) == -1) return(-1); }

/*
 * Set some standard variables used by all HTML pages
 */
int
add_standard_vars(struct conn_s *connptr)
{
        char timebuf[30];
        time_t global_time = time(NULL);

        strftime(timebuf, sizeof(timebuf), "%a, %d %b %Y %H:%M:%S GMT",
                 gmtime(&global_time));

        ADD_VAR_RET("request", connptr->request_line);
        ADD_VAR_RET("cause", connptr->error_string);
        ADD_VAR_RET("clientip", connptr->client_ip_addr);
        ADD_VAR_RET("clienthost", connptr->client_string_addr);
        ADD_VAR_RET("version", VERSION);
        ADD_VAR_RET("package", PACKAGE);
        ADD_VAR_RET("date", timebuf);
        return (0);
}

/*
 * Add the error information to the conn structure.
 */
int
indicate_http_error(struct conn_s *connptr, int number, char *message, ...)
{
        va_list ap;
        char *key, *val;

        va_start(ap, message);

        while ((key = va_arg(ap, char *))) {
                val = va_arg(ap, char *);

                if (add_error_variable(connptr, key, val) == -1) {
                        va_end(ap);
                        return (-1);
                }
        }

        connptr->error_number = number;
        connptr->error_string = safestrdup(message);

        va_end(ap);

        return (add_standard_vars(connptr));
}