tinyproxy/src/filter.c

/* tinyproxy - A fast light-weight HTTP proxy
 * Copyright (C) 1999 George Talusan <gstalusan@uwaterloo.ca>
 * Copyright (C) 2002 James E. Flemer <jflemer@acm.jhu.edu>
 * Copyright (C) 2002 Robert James Kaes <rjkaes@users.sourceforge.net>
 *
 * 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.
 */

/* A substring of the domain to be filtered goes into the file
 * pointed at by DEFAULT_FILTER.
 */

#include "main.h"

#include "filter.h"
#include "heap.h"
#include "log.h"
#include "reqs.h"

#define FILTER_BUFFER_LEN (512)

static int err;

struct filter_list {
        struct filter_list *next;
        char *pat;
        regex_t *cpat;
};

static struct filter_list *fl = NULL;
static int already_init = 0;
static filter_policy_t default_policy = FILTER_DEFAULT_ALLOW;

/*
 * Initializes a linked list of strings containing hosts/urls to be filtered
 */
void filter_init (void)
{
        FILE *fd;
        struct filter_list *p;
        char buf[FILTER_BUFFER_LEN];
        char *s;
        int cflags;

        if (!fl && !already_init) {
                fd = fopen (config.filter, "r");
                if (fd) {
                        p = NULL;

                        cflags = REG_NEWLINE | REG_NOSUB;
                        if (config.filter_extended)
                                cflags |= REG_EXTENDED;
                        if (!config.filter_casesensitive)
                                cflags |= REG_ICASE;

                        while (fgets (buf, FILTER_BUFFER_LEN, fd)) {
                                /*
                                 * Remove any trailing white space and
                                 * comments.
                                 */
                                s = buf;
                                while (*s) {
                                        if (isspace ((unsigned char) *s))
                                                break;
                                        if (*s == '#') {
                                                /*
                                                 * If the '#' char is preceeded by
                                                 * an escape, it's not a comment
                                                 * string.
                                                 */
                                                if (s == buf
                                                    || *(s - 1) != '\\')
                                                        break;
                                        }
                                        ++s;
                                }
                                *s = '\0';

                                /* skip leading whitespace */
                                s = buf;
                                while (*s && isspace ((unsigned char) *s))
                                        s++;

                                /* skip blank lines and comments */
                                if (*s == '\0')
                                        continue;

                                if (!p) /* head of list */
                                        fl = p =
                                            (struct filter_list *)
                                            safecalloc (1,
                                                        sizeof (struct
                                                                filter_list));
                                else {  /* next entry */
                                        p->next =
                                            (struct filter_list *)
                                            safecalloc (1,
                                                        sizeof (struct
                                                                filter_list));
                                        p = p->next;
                                }

                                p->pat = safestrdup (s);
                                p->cpat =
                                    (regex_t *) safemalloc (sizeof (regex_t));
                                err = regcomp (p->cpat, p->pat, cflags);
                                if (err != 0) {
                                        fprintf (stderr,
                                                 "Bad regex in %s: %s\n",
                                                 config.filter, p->pat);
                                        exit (EX_DATAERR);
                                }
                        }
                        if (ferror (fd)) {
                                perror ("fgets");
                                exit (EX_DATAERR);
                        }
                        fclose (fd);

                        already_init = 1;
                }
        }
}

/* unlink the list */
void filter_destroy (void)
{
        struct filter_list *p, *q;

        if (already_init) {
                for (p = q = fl; p; p = q) {
                        regfree (p->cpat);
                        safefree (p->cpat);
                        safefree (p->pat);
                        q = p->next;
                        safefree (p);
                }
                fl = NULL;
                already_init = 0;
        }
}

/* Return 0 to allow, non-zero to block */
int filter_domain (const char *host)
{
        struct filter_list *p;
        int result;

        if (!fl || !already_init)
                goto COMMON_EXIT;

        for (p = fl; p; p = p->next) {
                result =
                    regexec (p->cpat, host, (size_t) 0, (regmatch_t *) 0, 0);

                if (result == 0) {
                        if (default_policy == FILTER_DEFAULT_ALLOW)
                                return 1;
                        else
                                return 0;
                }
        }

COMMON_EXIT:
        if (default_policy == FILTER_DEFAULT_ALLOW)
                return 0;
        else
                return 1;
}

/* returns 0 to allow, non-zero to block */
int filter_url (const char *url)
{
        struct filter_list *p;
        int result;

        if (!fl || !already_init)
                goto COMMON_EXIT;

        for (p = fl; p; p = p->next) {
                result =
                    regexec (p->cpat, url, (size_t) 0, (regmatch_t *) 0, 0);

                if (result == 0) {
                        if (default_policy == FILTER_DEFAULT_ALLOW)
                                return 1;
                        else
                                return 0;
                }
        }

COMMON_EXIT:
        if (default_policy == FILTER_DEFAULT_ALLOW)
                return 0;
        else
                return 1;
}

/*
 * Set the default filtering policy
 */
void filter_set_default_policy (filter_policy_t policy)
{
        default_policy = policy;
}