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cidr.cpp

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/*       +------------------------------------+
 *       | Inspire Internet Relay Chat Daemon |
 *       +------------------------------------+
 *
 *  InspIRCd: (C) 2002-2008 InspIRCd Development Team
 * See: http://www.inspircd.org/wiki/index.php/Credits
 *
 * This program is free but copyrighted software; see
 *            the file COPYING for details.
 *
 * ---------------------------------------------------
 */

/* $Core */

#include "inspircd.h"

/* Used when comparing CIDR masks for the modulus bits left over.
 * A lot of ircd's seem to do this:
 * ((-1) << (8 - (mask % 8)))
 * But imho, it sucks in comparison to a nice neat lookup table.
 */
const unsigned char inverted_bits[8] = {        0x00, /* 00000000 - 0 bits - never actually used */
                                0x80, /* 10000000 - 1 bits */
                                0xC0, /* 11000000 - 2 bits */
                                0xE0, /* 11100000 - 3 bits */
                                0xF0, /* 11110000 - 4 bits */
                                0xF8, /* 11111000 - 5 bits */
                                0xFC, /* 11111100 - 6 bits */
                                0xFE  /* 11111110 - 7 bits */
};


/* Match raw bytes using CIDR bit matching, used by higher level MatchCIDR() */
bool irc::sockets::MatchCIDRBits(const unsigned char* address, const unsigned char* mask, unsigned int mask_bits)
{
        unsigned int divisor = mask_bits / 8; /* Number of whole bytes in the mask */
        unsigned int modulus = mask_bits % 8; /* Remaining bits in the mask after whole bytes are dealt with */

        /* First (this is faster) compare the odd bits with logic ops */
        if (modulus)
                if ((address[divisor] & inverted_bits[modulus]) != (mask[divisor] & inverted_bits[modulus]))
                        /* If they dont match, return false */
                        return false;

        /* Secondly (this is slower) compare the whole bytes */
        if (memcmp(address, mask, divisor))
                return false;

        /* The address matches the mask, to mask_bits bits of mask */
        return true;
}

/* Match CIDR, but dont attempt to match() against leading *!*@ sections */
bool irc::sockets::MatchCIDR(const std::string &address, const std::string &cidr_mask)
{
        return MatchCIDR(address, cidr_mask, false);
}

/* Match CIDR strings, e.g. 127.0.0.1 to 127.0.0.0/8 or 3ffe:1:5:6::8 to 3ffe:1::0/32
 * If you have a lot of hosts to match, youre probably better off building your mask once
 * and then using the lower level MatchCIDRBits directly.
 *
 * This will also attempt to match any leading usernames or nicknames on the mask, using
 * match(), when match_with_username is true.
 */
bool irc::sockets::MatchCIDR(const std::string &address, const std::string &cidr_mask, bool match_with_username)
{
        unsigned char addr_raw[16];
        unsigned char mask_raw[16];
        unsigned int bits = 0;

        std::string address_copy;
        std::string cidr_copy;

        /* The caller is trying to match ident@<mask>/bits.
         * Chop off the ident@ portion, use match() on it
         * seperately.
         */
        if (match_with_username)
        {
                /* Use strchr not strrchr, because its going to be nearer to the left */
                std::string::size_type username_mask_pos = cidr_mask.rfind('@');
                std::string::size_type username_addr_pos = address.rfind('@');

                /* Both strings have an @ symbol in them */
                if (username_mask_pos != std::string::npos && username_addr_pos != std::string::npos)
                {
                        /* Try and match() the strings before the @
                         * symbols, and recursively call MatchCIDR without
                         * username matching enabled to match the host part.
                         */
                        return (InspIRCd::Match(address.substr(0, username_addr_pos), cidr_mask.substr(0, username_mask_pos), NULL) &&
                                        MatchCIDR(address.substr(username_addr_pos + 1), cidr_mask.substr(username_mask_pos + 1), false));
                }
                else
                {
                        address_copy = address.substr(username_addr_pos + 1);
                        cidr_copy = cidr_mask.substr(username_mask_pos + 1);
                }
        }
        else
        {
                address_copy.assign(address);
                cidr_copy.assign(cidr_mask);
        }

        in_addr  address_in4;
        in_addr  mask_in4;

        std::string::size_type bits_chars = cidr_copy.rfind('/');

        if (bits_chars != std::string::npos)
        {
                bits = atoi(cidr_copy.substr(bits_chars + 1).c_str());
                cidr_copy.erase(bits_chars, cidr_copy.length() - bits_chars);
        }
        else
        {
                /* No 'number of bits' field! */
                return false;
        }

#ifdef SUPPORT_IP6LINKS
        in6_addr address_in6;
        in6_addr mask_in6;

        if (inet_pton(AF_INET6, address_copy.c_str(), &address_in6) > 0)
        {
                if (inet_pton(AF_INET6, cidr_copy.c_str(), &mask_in6) > 0)
                {
                        memcpy(&addr_raw, &address_in6.s6_addr, 16);
                        memcpy(&mask_raw, &mask_in6.s6_addr, 16);

                        if (bits > 128)
                                bits = 128;
                }
                else
                {
                        /* The address was valid ipv6, but the mask
                         * that goes with it wasnt.
                         */
                        return false;
                }
        }
        else
#endif
        if (inet_pton(AF_INET, address_copy.c_str(), &address_in4) > 0)
        {
                if (inet_pton(AF_INET, cidr_copy.c_str(), &mask_in4) > 0)
                {
                        memcpy(&addr_raw, &address_in4.s_addr, 4);
                        memcpy(&mask_raw, &mask_in4.s_addr, 4);

                        if (bits > 32)
                                bits = 32;
                }
                else
                {
                        /* The address was valid ipv4,
                         * but the mask that went with it wasnt.
                         */
                        return false;
                }
        }
        else
        {
                /* The address was neither ipv4 or ipv6 */
                return false;
        }

        /* Low-level-match the bits in the raw data */
        return MatchCIDRBits(addr_raw, mask_raw, bits);
}