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ncat_hostmatch.c

/***************************************************************************
 * ncat_hostmatch.c -- Address set (addrset) management, used for --allow  *
 * and --deny.                                                             *
 ***********************IMPORTANT NMAP LICENSE TERMS************************
 *                                                                         *
 * The Nmap Security Scanner is (C) 1996-2009 Insecure.Com LLC. Nmap is    *
 * also a registered trademark of Insecure.Com LLC.  This program is free  *
 * software; you may redistribute and/or modify it under the terms of the  *
 * GNU General Public License as published by the Free Software            *
 * Foundation; Version 2 with the clarifications and exceptions described  *
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 * this software under certain conditions.  If you wish to embed Nmap      *
 * technology into proprietary software, we sell alternative licenses      *
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 * license Nmap technology such as host discovery, port scanning, OS       *
 * detection, and version detection.                                       *
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 *   not derivative works.)                                                * 
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 * included with Nmap.                                                     *
 *                                                                         *
 ***************************************************************************/

/* $Id: ncat_hostmatch.c 14321 2009-07-16 02:27:31Z david $ */

/* The code in this file has tests in the file tests/test-addrset.sh. Run that
   program after making any big changes. Also, please add tests for any new
   features. */

#include "nsock.h"
#include "ncat.h"
#include "ncat_hostmatch.h"
#include "sys_wrap.h"

#include <errno.h>
#include <limits.h>
#include <stdio.h>
#ifndef WIN32
#include <netdb.h>
#endif

void addrset_init(struct addrset *set)
{
    set->head = NULL;
}

void addrset_free(struct addrset *set)
{
    struct addrset_elem *elem, *next;

    for (elem = set->head; elem != NULL; elem = next) {
        next = elem->next;
        free(elem);
    }
}

/* A debugging function to print out the contents of an addrset_elem. For IPv4
   this is the four bit vectors. For IPv6 it is the address and netmask. */
void addrset_elem_print(const struct addrset_elem *elem)
{
    int i, j;

    if (elem->type == ADDRSET_TYPE_IPV4_BITVECTOR) {
        for (i = 0; i < 4; i++) {
            for (j = 0; j < sizeof(octet_bitvector) / sizeof(bitvector_t); j++)
                printf("%08lX ", elem->u.ipv4.bits[i][j]);
            printf("\n");
        }
#ifdef HAVE_IPV6
    } else if (elem->type == ADDRSET_TYPE_IPV6_NETMASK) {
        for (i = 0; i < 16; i += 2) {
            if (i > 0)
                printf(":");
            printf("%02X", elem->u.ipv6.addr.s6_addr[i]);
            printf("%02X", elem->u.ipv6.addr.s6_addr[i + 1]);
        }
        printf(" ");
        for (i = 0; i < 16; i += 2) {
            if (i > 0)
                printf(":");
            printf("%02X", elem->u.ipv6.mask.s6_addr[i]);
            printf("%02X", elem->u.ipv6.mask.s6_addr[i + 1]);
        }
        printf("\n");
#endif
    }
    printf("---\n");
}

/* This is a wrapper around getaddrinfo that automatically handles hints for
   IPv4/IPv6, TCP/UDP, and whether name resolution is allowed (o.nodns). */
static int resolve_name(const char *name, struct addrinfo **result)
{
    struct addrinfo hints = { 0 };
    int rc;

    if (o.udp)
        hints.ai_protocol = IPPROTO_UDP;
    else
        hints.ai_protocol = IPPROTO_TCP;

    /* First do a non-DNS lookup for any address family (just checks for a valid
       numeric address). We recognize numeric addresses no matter the setting of
       o.af. This is also the last step if o.nodns is true. */
    hints.ai_flags |= AI_NUMERICHOST;
    hints.ai_family = AF_UNSPEC;
    *result = NULL;
    rc = getaddrinfo(name, NULL, &hints, result);
    if (rc == 0 || o.nodns)
        return rc;

    /* Do a DNS lookup now. When we look up a name we only want addresses
       corresponding to the current value of o.af. */
    hints.ai_flags &= ~AI_NUMERICHOST;
    hints.ai_family = o.af;
    *result = NULL;
    rc = getaddrinfo(name, NULL, &hints, result);

    return rc;
}

/* This is an address family-agnostic version of inet_ntop. */
static char *address_to_string(const struct sockaddr *sa, size_t sa_len,
                               char *buf, size_t len)
{
    getnameinfo(sa, sa_len, buf, len, NULL, 0, NI_NUMERICHOST);

    return buf;
}

/* Break an IPv4 address into an array of octets. */
static void in_addr_to_octets(const struct in_addr *ia, uint8_t octets[4])
{
    octets[0] = (ia->s_addr & 0xFF);
    octets[1] = (ia->s_addr & (0xFF << 8)) >> 8;
    octets[2] = (ia->s_addr & (0xFF << 16)) >> 16;
    octets[3] = (ia->s_addr & (0xFF << 24)) >> 24;
}

#define BITVECTOR_BITS (sizeof(bitvector_t) * CHAR_BIT)
#define BIT_SET(v, n) ((v)[(n) / BITVECTOR_BITS] |= 1UL << ((n) % BITVECTOR_BITS))
#define BIT_IS_SET(v, n) (((v)[(n) / BITVECTOR_BITS] & 1UL << ((n) % BITVECTOR_BITS)) != 0)

static int parse_ipv4_ranges(struct addrset_elem *elem, const char *spec);
static void apply_ipv4_netmask_bits(struct addrset_elem *elem, int bits);
#ifdef HAVE_IPV6
static void make_ipv6_netmask(struct in6_addr *mask, int bits);
#endif

/* Add a host specification into the address set. Returns 1 on success, 0 on
   error. */
int addrset_add_spec(struct addrset *set, const char *spec)
{
    char *local_spec;
    char *netmask_s;
    char *tail;
    long netmask_bits;
    struct addrinfo *addrs, *addr;
    struct addrset_elem *elem;
    int rc;

    /* Make a copy of the spec to mess with. */
    local_spec = Strdup(spec);
    if (local_spec == NULL)
        return 0;

    /* Read the CIDR netmask bits, if present. */
    netmask_s = strchr(local_spec, '/');
    if (netmask_s == NULL) {
        /* A negative value means unspecified; default depends on the address
           family. */
        netmask_bits = -1;
    } else {
        *netmask_s = '\0';
        netmask_s++;
        errno = 0;
        netmask_bits = parse_long(netmask_s, &tail);
        if (errno != 0 || *tail != '\0' || tail == netmask_s) {
            loguser("Error parsing netmask in \"%s\".\n", spec);
            free(local_spec);
            return 0;
        }
    }

    elem = (struct addrset_elem *) safe_malloc(sizeof(*elem));
    memset(elem->u.ipv4.bits, 0, sizeof(elem->u.ipv4.bits));

    /* Check if this is an IPv4 address, with optional ranges and wildcards. */
    if (parse_ipv4_ranges(elem, local_spec)) {
        if (netmask_bits > 32) {
            loguser("Illegal netmask in \"%s\". Must be between 0 and 32.\n", spec);
            free(local_spec);
            free(elem);
            return 0;
        }
        apply_ipv4_netmask_bits(elem, netmask_bits);
        if (o.debug)
            logdebug("Add IPv4 range %s/%ld to addrset.\n", local_spec, netmask_bits > 0 ? netmask_bits : 32);
        elem->type = ADDRSET_TYPE_IPV4_BITVECTOR;
        elem->next = set->head;
        set->head = elem;
        free(local_spec);
        return 1;
    } else {
        free(elem);
    }

    /* When all else fails, resolve the name. */
    rc = resolve_name(local_spec, &addrs);
    if (rc != 0) {
        loguser("Error resolving name \"%s\": %s\n", local_spec, gai_strerror(rc));
        free(local_spec);
        return 0;
    }
    if (addrs == NULL)
        loguser("Warning: no addresses found for %s.\n", local_spec);
    free(local_spec);

    /* Walk the list of addresses and add them all to the set with netmasks. */
    for (addr = addrs; addr != NULL; addr = addr->ai_next) {
        char addr_string[128];

        elem = (struct addrset_elem *) safe_malloc(sizeof(*elem));
        memset(elem->u.ipv4.bits, 0, sizeof(elem->u.ipv4.bits));

        address_to_string(addr->ai_addr, addr->ai_addrlen, addr_string, sizeof(addr_string));

        /* Note: it is possible that in this loop we are dealing with addresses
           of more than one family (e.g., IPv4 and IPv6). But we have at most
           one netmask value for all of them. Whatever netmask we have is
           applied blindly to whatever addresses there are, which may not be
           what you want if a /24 is applied to IPv6 and will cause an error if
           a /120 is applied to IPv4. */
        if (addr->ai_family == AF_INET) {
            const struct sockaddr_in *sin = (struct sockaddr_in *) addr->ai_addr;
            uint8_t octets[4];

            elem->type = ADDRSET_TYPE_IPV4_BITVECTOR;

            in_addr_to_octets(&sin->sin_addr, octets);
            BIT_SET(elem->u.ipv4.bits[0], octets[0]);
            BIT_SET(elem->u.ipv4.bits[1], octets[1]);
            BIT_SET(elem->u.ipv4.bits[2], octets[2]);
            BIT_SET(elem->u.ipv4.bits[3], octets[3]);

            if (netmask_bits > 32) {
                loguser("Illegal netmask in \"%s\". Must be between 0 and 32.\n", spec);
                free(elem);
                return 0;
            }
            apply_ipv4_netmask_bits(elem, netmask_bits);

            if (o.debug)
                logdebug("Add IPv4 %s/%ld to addrset.\n", addr_string, netmask_bits > 0 ? netmask_bits : 32);
#ifdef HAVE_IPV6
        } else if (addr->ai_family == AF_INET6) {
            const struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *) addr->ai_addr;

            elem->type = ADDRSET_TYPE_IPV6_NETMASK;

            elem->u.ipv6.addr = sin6->sin6_addr;

            if (netmask_bits > 128) {
                loguser("Illegal netmask in \"%s\". Must be between 0 and 128.\n", spec);
                free(elem);
                return 0;
            }
            make_ipv6_netmask(&elem->u.ipv6.mask, netmask_bits);

            if (o.debug)
                logdebug("Add IPv6 %s/%ld to addrset.\n", addr_string, netmask_bits > 0 ? netmask_bits : 128);
#endif
        } else {
            if (o.verbose)
                logdebug("ignoring address %s for %s. Family %d socktype %d protocol %d.\n", addr_string, spec, addr->ai_family, addr->ai_socktype, addr->ai_protocol);
            free(elem);
            continue;
        }

        elem->next = set->head;
        set->head = elem;
    }

    freeaddrinfo(addrs);

    return 1;
}

/* Add whitespace-separated host specifications from fd into the address set.
   Returns 1 on success, 0 on error. */
int addrset_add_file(struct addrset *set, FILE *fd)
{
    char buf[1024];
    int c, i;

    for (;;) {
        /* Skip whitespace. */
        while ((c = getc(fd)) != EOF) {
            if (!isspace(c))
                break;
        }
        if (c == EOF)
            break;
        ungetc(c, fd);

        i = 0;
        while ((c = getc(fd)) != EOF) {
            if (isspace(c))
                break;
            if (i + 1 > sizeof(buf) - 1) {
                /* Truncate the specification to give a little context. */
                buf[11] = '\0';
                loguser("Host specification starting with \"%s\" is too long.\n", buf);
                return 0;
            }
            buf[i++] = c;
        }
        buf[i] = '\0';

        if (!addrset_add_spec(set, buf))
            return 0;
    }

    return 1;
}

/* Parse an IPv4 address with optional ranges and wildcards into bit vectors.
   Each octet must match the regular expression '(\*|#?(-#?)?(,#?(-#?)?)*)',
   where '#' stands for an integer between 0 and 255. Return 1 on success, 0 on
   error. */
static int parse_ipv4_ranges(struct addrset_elem *elem, const char *spec)
{
    const char *p;
    int octet_index, i;

    p = spec;
    octet_index = 0;
    while (*p != '\0' && octet_index < 4) {
        if (*p == '*') {
            for (i = 0; i < 256; i++)
                BIT_SET(elem->u.ipv4.bits[octet_index], i);
            p++;
        } else {
            for (;;) {
                long start, end;
                char *tail;

                errno = 0;
                start = parse_long(p, &tail);
                /* Is this a range open on the left? */
                if (tail == p) {
                    if (*p == '-')
                        start = 0;
                    else
                        return 0;
                }
                if (errno != 0 || start < 0 || start > 255)
                    return 0;
                p = tail;

                /* Look for a range. */
                if (*p == '-') {
                    p++;
                    errno = 0;
                    end = parse_long(p, &tail);
                    /* Is this range open on the right? */
                    if (tail == p)
                        end = 255;
                    if (errno != 0 || end < 0 || end > 255 || end < start)
                        return 0;
                    p = tail;
                } else {
                    end = start;
                }

                /* Fill in the range in the bit vector. */
                for (i = start; i <= end; i++)
                    BIT_SET(elem->u.ipv4.bits[octet_index], i);

                if (*p != ',')
                    break;
                p++;
            }
        }
        octet_index++;
        if (octet_index < 4) {
            if (*p != '.')
                return 0;
            p++;
        }
    }
    if (*p != '\0' || octet_index < 4)
        return 0;

    return 1;
}

/* Expand a single-octet bit vector to include any additional addresses that
   result when mask is applied. */
static void apply_ipv4_netmask_octet(octet_bitvector bits, uint8_t mask)
{
    int i, j;
    uint32_t chunk_size;

    /* Process the bit vector in chunks, first of size 1, then of size 2, up to
       size 128. Check the next bit of the mask. If it is 1, do nothing.
       Otherwise, pair up the chunks (first with the second, third with the
       fourth, etc.). For each pair of chunks, set a bit in one chunk if it is
       set in the other. chunk_size also serves as an index into the mask. */
    for (chunk_size = 1; chunk_size < 256; chunk_size <<= 1) {
        if ((mask & chunk_size) != 0)
            continue;
        for (i = 0; i < 256; i += chunk_size * 2) {
            for (j = 0; j < chunk_size; j++) {
                if (BIT_IS_SET(bits, i + j))
                    BIT_SET(bits, i + j + chunk_size);
                else if (BIT_IS_SET(bits, i + j + chunk_size))
                    BIT_SET(bits, i + j);
            }
        }
    }
}

/* Expand an addrset_elem's IPv4 bit vectors to include any additional addresses
   that result when the given netmask is applied. The mask is in network byte
   order. */
static void apply_ipv4_netmask(struct addrset_elem *elem, uint32_t mask)
{
    mask = ntohl(mask);
    /* Apply the mask one octet at a time. It's done this way because ranges
       span exactly one octet. */
    apply_ipv4_netmask_octet(elem->u.ipv4.bits[0], (mask & 0xFF000000) >> 24);
    apply_ipv4_netmask_octet(elem->u.ipv4.bits[1], (mask & 0x00FF0000) >> 16);
    apply_ipv4_netmask_octet(elem->u.ipv4.bits[2], (mask & 0x0000FF00) >> 8);
    apply_ipv4_netmask_octet(elem->u.ipv4.bits[3], (mask & 0x000000FF));
}

/* Expand an addrset_elem's IPv4 bit vectors to include any additional addresses
   that result from the application of a CIDR-style netmask with the given
   number of bits. If bits is negative it is taken to be 32. */
static void apply_ipv4_netmask_bits(struct addrset_elem *elem, int bits)
{
    uint32_t mask;

    if (bits > 32)
        return;
    if (bits < 0)
        bits = 32;

    if (bits == 0)
        mask = htonl(0x00000000);
    else
        mask = htonl(0xFFFFFFFF << (32 - bits));
    apply_ipv4_netmask(elem, mask);
}

#ifdef HAVE_IPV6
/* Fill in an in6_addr with a CIDR-style netmask with the given number of bits.
   If bits is negative it is taken to be 128. The netmask is written in network
   byte order. */
static void make_ipv6_netmask(struct in6_addr *mask, int bits)
{
    int i;

    memset(mask, 0, sizeof(*mask));

    if (bits > 128)
        return;
    if (bits < 0)
        bits = 128;

    if (bits == 0)
        return;

    i = 0;
    /* 0 < bits <= 128, so this loop goes at most 15 times. */
    for ( ; bits > 8; bits -= 8)
        mask->s6_addr[i++] = 0xFF;
    mask->s6_addr[i] = 0xFF << (8 - bits);
}
#endif

static int match_ipv4_bits(const octet_bitvector bits[4], const struct sockaddr *sa)
{
    uint8_t octets[4];

    if (sa->sa_family != AF_INET)
        return 0;

    in_addr_to_octets(&((const struct sockaddr_in *) sa)->sin_addr, octets);

    return BIT_IS_SET(bits[0], octets[0])
        && BIT_IS_SET(bits[1], octets[1])
        && BIT_IS_SET(bits[2], octets[2])
        && BIT_IS_SET(bits[3], octets[3]);
}

#ifdef HAVE_IPV6
static int match_ipv6_netmask(const struct in6_addr *addr,
    const struct in6_addr *mask, const struct sockaddr *sa)
{
    const uint8_t *a = addr->s6_addr;
    const uint8_t *m = mask->s6_addr;
    const uint8_t *b = ((const struct sockaddr_in6 *) sa)->sin6_addr.s6_addr;
    int i;

    if (sa->sa_family != AF_INET6)
        return 0;

    for (i = 0; i < 16; i++) {
        if ((a[i] & m[i]) != (b[i] & m[i]))
            return 0;
    }

    return 1;
}
#endif

static int addrset_elem_match(const struct addrset_elem *elem, const struct sockaddr *sa)
{
    switch (elem->type) {
        case ADDRSET_TYPE_IPV4_BITVECTOR:
            return match_ipv4_bits(elem->u.ipv4.bits, sa);
#ifdef HAVE_IPV6
        case ADDRSET_TYPE_IPV6_NETMASK:
            return match_ipv6_netmask(&elem->u.ipv6.addr, &elem->u.ipv6.mask, sa);
#endif
    }

    return 0;
}

int addrset_contains(const struct addrset *set, const struct sockaddr *sa)
{
    struct addrset_elem *elem;

    for (elem = set->head; elem != NULL; elem = elem->next) {
        if (addrset_elem_match(elem, sa))
            return 1;
    }

    return 0;
}

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