924da17c17
to handle IPv6 style addresses along with the existing IPv4 and string addresses. In addition, the hand-rolled "list" code has been replaced with a vector (code reuse.) Also, the code should be a little easier to understand (relatively speaking.) I do need to add some kind of testing framework (in general) to check that the new code does work with all the formats that will be thrown at it.
306 lines
7.9 KiB
C
306 lines
7.9 KiB
C
/* $Id: acl.c,v 1.19 2004-08-11 20:09:20 rjkaes Exp $
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*
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* This system handles Access Control for use of this daemon. A list of
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* domains, or IP addresses (including IP blocks) are stored in a list
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* which is then used to compare incoming connections.
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*
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* Copyright (C) 2000,2002 Robert James Kaes (rjkaes@flarenet.com)
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2, or (at your option) any
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* later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*/
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#include "tinyproxy.h"
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#include "acl.h"
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#include "heap.h"
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#include "log.h"
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#include "network.h"
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#include "sock.h"
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#include "vector.h"
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/* Define how long an IPv6 address is in bytes (128 bits, 16 bytes) */
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#define IPV6_LEN 16
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enum acl_type { ACL_STRING, ACL_NUMERIC };
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/*
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* Hold the information about a particular access control. We store
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* whether it's an ALLOW or DENY entry, and also whether it's a string
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* entry (like a domain name) or an IP entry.
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*/
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struct acl_s {
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acl_access_t access;
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enum acl_type type;
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union {
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char* addr;
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struct {
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unsigned char addr[IPV6_LEN];
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unsigned char mask[IPV6_LEN];
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} ip;
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};
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};
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/*
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* All the access lists are stored in a vector.
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*/
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static vector_t access_list = NULL;
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/*
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* Inserts a new access control into the list. The function will figure out
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* whether the location is an IP address (with optional netmask) or a
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* domain name.
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*
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* Returns:
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* -1 on failure
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* 0 otherwise.
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*/
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int
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insert_acl(char *location, acl_access_t access_type)
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{
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struct acl_s acl;
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int i, ret, mask;
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char *p, ip_dst[IPV6_LEN];
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assert(location != NULL);
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/*
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* If the access list has not been set up, create it.
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*/
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if (!access_list) {
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access_list = vector_create();
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if (!access_list) {
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log_message(LOG_ERR,
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"Unable to allocate memory for access list");
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return -1;
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}
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}
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/*
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* Start populating the access control structure.
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*/
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memset(&acl, 0, sizeof(struct acl_s));
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acl.access = access_type;
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/*
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* Check for a valid IP address (the simplest case) first.
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*/
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if (full_inet_pton(location, ip_dst) > 0) {
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acl.type = ACL_NUMERIC;
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memcpy(acl.ip.addr, ip_dst, IPV6_LEN);
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memset(acl.ip.mask, 0xff, IPV6_LEN);
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} else {
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/*
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* At this point we're either a hostname or an
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* IP address with a slash.
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*/
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p = strchr(location, '/');
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if (p != NULL) {
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/*
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* We have a slash, so it's intended to be an
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* IP address with mask
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*/
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*p = '\0';
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if (full_inet_pton(location, ip_dst) <= 0)
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return -1;
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acl.type = ACL_NUMERIC;
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memcpy(acl.ip.addr, ip_dst, IPV6_LEN);
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mask = strtol(p + 1, NULL, 10);
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for (i = 0; i != IPV6_LEN; ++i) {
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if (mask >= ((i + 1) * 8))
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acl.ip.mask[i] = 0xff;
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else
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acl.ip.mask[i] = 0xff << (8 - (mask - i * 8));
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}
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} else {
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/* In all likelihood a string */
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acl.type = ACL_STRING;
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acl.addr = safestrdup(location);
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if (!acl.addr)
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return -1;
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}
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}
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/*
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* Add the entry and then clean up.
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*/
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ret = vector_append(access_list, &acl, sizeof(struct acl_s));
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safefree(acl.addr);
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return ret;
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}
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/*
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* This function is called whenever a "string" access control is found in
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* the ACL. From here we do both a text based string comparison, along with
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* a reverse name lookup comparison of the IP addresses.
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*
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* Return: 0 if host is denied
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* 1 if host is allowed
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* -1 if no tests match, so skip
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*/
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static int
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acl_string_processing(struct acl_s* acl,
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const char* ip_address,
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const char* string_address)
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{
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int match;
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struct addrinfo hints, *res, *ressave;
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size_t test_length, match_length;
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char ipbuf[512];
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assert(acl && acl->type == ACL_STRING);
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assert(ip_address && strlen(ip_address) > 0);
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assert(string_address && strlen(string_address) > 0);
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/*
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* If the first character of the ACL string is a period, we need to
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* do a string based test only; otherwise, we can do a reverse
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* lookup test as well.
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*/
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if (acl->addr[0] != '.') {
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memset(&hints, 0, sizeof(struct addrinfo));
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hints.ai_family = AF_UNSPEC;
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hints.ai_socktype = SOCK_STREAM;
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if (getaddrinfo(acl->addr, NULL, &hints, &res) != 0)
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goto STRING_TEST;
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ressave = res;
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match = FALSE;
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do {
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get_ip_string(res->ai_addr, ipbuf, sizeof(ipbuf));
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if (strcmp(ip_address, ipbuf) == 0) {
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match = TRUE;
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break;
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}
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} while ((res = res->ai_next) != NULL);
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freeaddrinfo(ressave);
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if (match) {
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if (acl->access == ACL_DENY)
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return 0;
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else
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return 1;
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}
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}
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STRING_TEST:
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test_length = strlen(string_address);
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match_length = strlen(acl->addr);
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/*
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* If the string length is shorter than AC string, return a -1 so
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* that the "driver" will skip onto the next control in the list.
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*/
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if (test_length < match_length)
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return -1;
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if (strcasecmp(string_address + (test_length - match_length), acl->addr) == 0) {
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if (acl->access == ACL_DENY)
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return 0;
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else
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return 1;
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}
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/* Indicate that no tests succeeded, so skip to next control. */
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return -1;
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}
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/*
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* Compare the supplied numeric IP address with the supplied ACL structure.
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*
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* Return:
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* 1 IP address is allowed
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* 0 IP address is denied
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* -1 neither allowed nor denied.
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*/
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static int
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check_numeric_acl(const struct acl_s* acl, const char* ip)
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{
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uint8_t addr[IPV6_LEN], x, y;
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int i;
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assert(acl && acl->type == ACL_NUMERIC);
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assert(ip && strlen(ip) > 0);
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if (full_inet_pton(ip, &addr) <= 0) return -1;
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for (i = 0; i != IPV6_LEN; ++i) {
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x = addr[i] & acl->ip.mask[i];
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y = acl->ip.addr[i] & acl->ip.mask[i];
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/* If x and y don't match, the IP addresses don't match */
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if (x != y)
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return 0;
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}
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/* The addresses match, return the permission */
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return (acl->access == ACL_ALLOW);
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}
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/*
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* Checks whether file descriptor is allowed.
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*
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* Returns:
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* 1 if allowed
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* 0 if denied
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*/
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int
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check_acl(int fd, const char* ip, const char* host)
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{
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struct acl_s* acl;
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int perm;
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int i;
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assert(fd >= 0);
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assert(ip != NULL);
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assert(host != NULL);
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/*
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* If there is no access list allow everything.
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*/
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if (!access_list) return 1;
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for (i = 0; i != vector_length(access_list); ++i) {
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acl = vector_getentry(access_list, i, NULL);
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switch (acl->type) {
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case ACL_STRING:
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perm = acl_string_processing(acl, ip, host);
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break;
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case ACL_NUMERIC:
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if (ip[0] == '\0') continue;
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perm = check_numeric_acl(acl, ip);
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break;
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}
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/*
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* Check the return value too see if the IP address is
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* allowed or denied.
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*/
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if (perm == 0)
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break;
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else if (perm == 1)
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return perm;
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}
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/*
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* Deny all connections by default.
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*/
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log_message(LOG_NOTICE, "Unauthorized connection from \"%s\" [%s].",
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host, ip);
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return 0;
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}
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