core-lightning/gossipd/netaddress.c

#include <arpa/inet.h>
#include <assert.h>
#include <common/status.h>
#include <common/type_to_string.h>
#include <errno.h>
#include <gossipd/netaddress.h>
#include <netinet/in.h>
#include <stdbool.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>
#include <wire/wire.h>

/* Based on bitcoin's src/netaddress.cpp, hence different naming and styling!
   version 7f31762cb6261806542cc6d1188ca07db98a6950:

   Copyright (c) 2009-2010 Satoshi Nakamoto
   Copyright (c) 2009-2016 The Bitcoin Core developers
   Distributed under the MIT software license, see the accompanying
   file COPYING or http://www.opensource.org/licenses/mit-license.php.
*/

/* The common IPv4-in-IPv6 prefix */
static const unsigned char pchIPv4[12] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xff, 0xff };

static bool IsRFC6145(const struct wireaddr *addr)
{
    static const unsigned char pchRFC6145[] = {0,0,0,0,0,0,0,0,0xFF,0xFF,0,0};
    return addr->type == ADDR_TYPE_IPV6
        && memcmp(addr->addr, pchRFC6145, sizeof(pchRFC6145)) == 0;
}

static bool IsRFC6052(const struct wireaddr *addr)
{
    static const unsigned char pchRFC6052[] = {0,0x64,0xFF,0x9B,0,0,0,0,0,0,0,0};
    return addr->type == ADDR_TYPE_IPV6
        && memcmp(addr->addr, pchRFC6052, sizeof(pchRFC6052)) == 0;
}

static bool IsRFC3964(const struct wireaddr *addr)
{
    return addr->type == ADDR_TYPE_IPV6
        && addr->addr[0] == 0x20 && addr->addr[1] == 0x02;
}

/* Return offset of IPv4 address, or 0 == not an IPv4 */
static size_t IPv4In6(const struct wireaddr *addr)
{
    if (addr->type != ADDR_TYPE_IPV6)
        return 0;
    if (memcmp(addr->addr, pchIPv4, sizeof(pchIPv4)) == 0)
        return sizeof(pchIPv4);
    if (IsRFC6052(addr))
        return 12;
    if (IsRFC6145(addr))
        return 12;
    if (IsRFC3964(addr))
        return 2;
    return 0;
}

/* Is this an IPv4 address, or an IPv6-wrapped IPv4 */
static bool IsIPv4(const struct wireaddr *addr)
{
    return addr->type == ADDR_TYPE_IPV4 || IPv4In6(addr) != 0;
}

static bool IsIPv6(const struct wireaddr *addr)
{
    return addr->type == ADDR_TYPE_IPV6 && IPv4In6(addr) == 0;
}

static bool RawEq(const struct wireaddr *addr, const void *cmp, size_t len)
{
    size_t off = IPv4In6(addr);

    assert(off + len <= addr->addrlen);
    return memcmp(addr->addr + off, cmp, len) == 0;
}

/* The bitcoin code packs addresses backwards, so we map it here. */
static unsigned int GetByte(const struct wireaddr *addr, int n)
{
    size_t off = IPv4In6(addr);
    assert(off + n < addr->addrlen);
    return addr->addr[addr->addrlen - 1 - off - n];
}

static bool IsRFC1918(const struct wireaddr *addr)
{
    return IsIPv4(addr) && (
        GetByte(addr, 3) == 10 ||
        (GetByte(addr, 3) == 192 && GetByte(addr, 2) == 168) ||
        (GetByte(addr, 3) == 172 && (GetByte(addr, 2) >= 16 && GetByte(addr, 2) <= 31)));
}

static bool IsRFC2544(const struct wireaddr *addr)
{
    return IsIPv4(addr) && GetByte(addr, 3) == 198 && (GetByte(addr, 2) == 18 || GetByte(addr, 2) == 19);
}

static bool IsRFC3927(const struct wireaddr *addr)
{
    return IsIPv4(addr) && (GetByte(addr, 3) == 169 && GetByte(addr, 2) == 254);
}

static bool IsRFC6598(const struct wireaddr *addr)
{
    return IsIPv4(addr) && GetByte(addr, 3) == 100 && GetByte(addr, 2) >= 64 && GetByte(addr, 2) <= 127;
}

static bool IsRFC5737(const struct wireaddr *addr)
{
    return IsIPv4(addr) && ((GetByte(addr, 3) == 192 && GetByte(addr, 2) == 0 && GetByte(addr, 1) == 2) ||
        (GetByte(addr, 3) == 198 && GetByte(addr, 2) == 51 && GetByte(addr, 1) == 100) ||
        (GetByte(addr, 3) == 203 && GetByte(addr, 2) == 0 && GetByte(addr, 1) == 113));
}

static bool IsRFC3849(const struct wireaddr *addr)
{
    return IsIPv6(addr) && GetByte(addr, 15) == 0x20 && GetByte(addr, 14) == 0x01 && GetByte(addr, 13) == 0x0D && GetByte(addr, 12) == 0xB8;
}

static bool IsRFC4862(const struct wireaddr *addr)
{
    static const unsigned char pchRFC4862[] = {0xFE,0x80,0,0,0,0,0,0};
    return IsIPv6(addr) && RawEq(addr, pchRFC4862, sizeof(pchRFC4862));
}

static bool IsRFC4193(const struct wireaddr *addr)
{
    return IsIPv6(addr) && ((GetByte(addr, 15) & 0xFE) == 0xFC);
}

static bool IsRFC4843(const struct wireaddr *addr)
{
    return IsIPv6(addr) && (GetByte(addr, 15) == 0x20 && GetByte(addr, 14) == 0x01 && GetByte(addr, 13) == 0x00 && (GetByte(addr, 12) & 0xF0) == 0x10);
}

static bool IsTor(const struct wireaddr *addr UNUSED)
{
	/* FIXME */
	return false;
}

static bool IsLocal(const struct wireaddr *addr)
{
    // IPv4 loopback
   if (IsIPv4(addr) && (GetByte(addr, 3) == 127 || GetByte(addr, 3) == 0))
       return true;

   // IPv6 loopback (::1/128)
   static const unsigned char pchLocal[16] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1};
   if (IsIPv6(addr) && RawEq(addr, pchLocal, sizeof(pchLocal)))
       return true;

   return false;
}

static bool IsInternal(const struct wireaddr *addr)
{
    return addr->type == ADDR_TYPE_PADDING;
}

static bool IsValid(const struct wireaddr *addr)
{
    // unspecified IPv6 address (::/128)
    unsigned char ipNone6[16] = {};
    if (IsIPv6(addr) && RawEq(addr, ipNone6, sizeof(ipNone6)))
        return false;

    // documentation IPv6 address
    if (IsRFC3849(addr))
        return false;

    if (IsInternal(addr))
        return false;

    if (IsIPv4(addr))
    {
        // INADDR_NONE
        uint32_t ipNone = INADDR_NONE;
        if (RawEq(addr, &ipNone, sizeof(ipNone)))
            return false;

        // 0
        ipNone = 0;
        if (RawEq(addr, &ipNone, sizeof(ipNone)))
            return false;
    }

    return true;
}

static bool IsRoutable(const struct wireaddr *addr)
{
    return IsValid(addr) && !(IsRFC1918(addr) || IsRFC2544(addr) || IsRFC3927(addr) || IsRFC4862(addr) || IsRFC6598(addr) || IsRFC5737(addr) || (IsRFC4193(addr) && !IsTor(addr)) || IsRFC4843(addr) || IsLocal(addr) || IsInternal(addr));
}

/* Trick I learned from Harald Welte: create UDP socket, connect() and
 * then query address. */
/* Returns 0 if protocol completely unsupported, ADDR_LISTEN if we
 * can't reach addr, ADDR_LISTEN_AND_ANNOUNCE if we can (and fill saddr). */
static enum addr_listen_announce get_local_sockname(int af, void *saddr,
						    socklen_t saddrlen)
{
    int fd = socket(af, SOCK_DGRAM, 0);
    if (fd < 0) {
        status_trace("Failed to create %u socket: %s",
		     af, strerror(errno));
        return 0;
    }

    if (connect(fd, saddr, saddrlen) != 0) {
        status_trace("Failed to connect %u socket: %s",
		     af, strerror(errno));
        close(fd);
        return ADDR_LISTEN;
    }

    if (getsockname(fd, saddr, &saddrlen) != 0) {
        status_trace("Failed to get %u socket name: %s",
		     af, strerror(errno));
        close(fd);
        return ADDR_LISTEN;
    }

    close(fd);
    return ADDR_LISTEN_AND_ANNOUNCE;
}

/* Return 0 if not available, or whether it's listenable-only or announceable.
 * If it's listenable only, will set wireaddr to all-zero address for universal
 * binding. */
static enum addr_listen_announce guess_one_address(struct wireaddr *addr,
						   u16 portnum,
						   enum wire_addr_type type)
{
    enum addr_listen_announce ret;

    addr->type = type;
    addr->port = portnum;

    /* We point to Google nameservers, works unless you're inside Google :) */
    switch (type) {
    case ADDR_TYPE_IPV4: {
        struct sockaddr_in sin;
	sin.sin_port = htons(53);
        /* 8.8.8.8 */
	sin.sin_addr.s_addr = 0x08080808;
        sin.sin_family = AF_INET;
        ret = get_local_sockname(AF_INET, &sin, sizeof(sin));
        addr->addrlen = sizeof(sin.sin_addr);
        memcpy(addr->addr, &sin.sin_addr, addr->addrlen);
        break;
    }
    case ADDR_TYPE_IPV6: {
        struct sockaddr_in6 sin6;
        /* 2001:4860:4860::8888 */
        static const unsigned char pchGoogle[16]
                = {0x20,0x01,0x48,0x60,0x48,0x60,0,0,0,0,0,0,8,8,8,8};
        memset(&sin6, 0, sizeof(sin6));
        sin6.sin6_port = htons(53);
        sin6.sin6_family = AF_INET6;
        memcpy(sin6.sin6_addr.s6_addr, pchGoogle, sizeof(pchGoogle));
        ret = get_local_sockname(AF_INET6, &sin6, sizeof(sin6));
        addr->addrlen = sizeof(sin6.sin6_addr);
        memcpy(addr->addr, &sin6.sin6_addr, addr->addrlen);
        break;
    }
    case ADDR_TYPE_PADDING:
        status_trace("Padding address, ignoring");
        return 0;
    }

    if (ret == 0)
	return ret;

    /* If we can reach it, but resulting address is unroutable, listen only */
    if (ret == ADDR_LISTEN_AND_ANNOUNCE && !IsRoutable(addr)) {
        status_trace("Address %s is not routable",
		     type_to_string(tmpctx, struct wireaddr, addr));
	ret = ADDR_LISTEN;
    }

    if (ret == ADDR_LISTEN) {
	/* This corresponds to INADDR_ANY or in6addr_any */
	memset(addr->addr, 0, addr->addrlen);
    } else {
	status_trace("Public address %s",
		     type_to_string(tmpctx, struct wireaddr, addr));
    }
    return ret;
}

void guess_addresses(struct wireaddr_internal **wireaddrs,
		     enum addr_listen_announce **listen_announce,
		     u16 portnum)
{
    size_t n = tal_count(*wireaddrs);

    status_trace("Trying to guess public addresses...");

    /* We allocate an extra, then remove if it's not needed. */
    tal_resize(wireaddrs, n+1);
    tal_resize(listen_announce, n+1);

    (*wireaddrs)[n].itype = ADDR_INTERNAL_WIREADDR;
    /* We do IPv6 first: on Linux, that binds to IPv4 too. */
    (*listen_announce)[n] = guess_one_address(&(*wireaddrs)[n].u.wireaddr,
					      portnum, ADDR_TYPE_IPV6);
    if ((*listen_announce)[n] != 0) {
        n++;
        tal_resize(wireaddrs, n+1);
	tal_resize(listen_announce, n+1);
	(*wireaddrs)[n].itype = ADDR_INTERNAL_WIREADDR;
    }
    (*listen_announce)[n] = guess_one_address(&(*wireaddrs)[n].u.wireaddr,
					      portnum, ADDR_TYPE_IPV4);
    if ((*listen_announce)[n] == 0) {
        tal_resize(wireaddrs, n);
        tal_resize(listen_announce, n);
    }
}