lnd.xprv/tor/tor.go
2018-09-07 06:51:49 +02:00

244 lines
6.7 KiB
Go

package tor
import (
"crypto/rand"
"encoding/hex"
"fmt"
"net"
"strconv"
"github.com/btcsuite/btcd/connmgr"
"github.com/miekg/dns"
"golang.org/x/net/proxy"
)
var (
// dnsCodes maps the DNS response codes to a friendly description. This
// does not include the BADVERS code because of duplicate keys and the
// underlying DNS (miekg/dns) package not using it. For more info, see
// https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml.
dnsCodes = map[int]string{
0: "no error",
1: "format error",
2: "server failure",
3: "non-existent domain",
4: "not implemented",
5: "query refused",
6: "name exists when it should not",
7: "RR set exists when it should not",
8: "RR set that should exist does not",
9: "server not authoritative for zone",
10: "name not contained in zone",
16: "TSIG signature failure",
17: "key not recognized",
18: "signature out of time window",
19: "bad TKEY mode",
20: "duplicate key name",
21: "algorithm not supported",
22: "bad truncation",
23: "bad/missing server cookie",
}
)
// proxyConn is a wrapper around net.Conn that allows us to expose the actual
// remote address we're dialing, rather than the proxy's address.
type proxyConn struct {
net.Conn
remoteAddr net.Addr
}
func (c *proxyConn) RemoteAddr() net.Addr {
return c.remoteAddr
}
// Dial is a wrapper over the non-exported dial function that returns a wrapper
// around net.Conn in order to expose the actual remote address we're dialing,
// rather than the proxy's address.
func Dial(address, socksAddr string, streamIsolation bool) (net.Conn, error) {
conn, err := dial(address, socksAddr, streamIsolation)
if err != nil {
return nil, err
}
// Now that the connection is established, we'll create our internal
// proxyConn that will serve in populating the correct remote address
// of the connection, rather than using the proxy's address.
remoteAddr, err := ParseAddr(address, socksAddr)
if err != nil {
return nil, err
}
return &proxyConn{
Conn: conn,
remoteAddr: remoteAddr,
}, nil
}
// dial establishes a connection to the address via Tor's SOCKS proxy. Only TCP
// is supported over Tor. The final argument determines if we should force
// stream isolation for this new connection. If we do, then this means this new
// connection will use a fresh circuit, rather than possibly re-using an
// existing circuit.
func dial(address, socksAddr string, streamIsolation bool) (net.Conn, error) {
// If we were requested to force stream isolation for this connection,
// we'll populate the authentication credentials with random data as
// Tor will create a new circuit for each set of credentials.
var auth *proxy.Auth
if streamIsolation {
var b [16]byte
if _, err := rand.Read(b[:]); err != nil {
return nil, err
}
auth = &proxy.Auth{
User: hex.EncodeToString(b[:8]),
Password: hex.EncodeToString(b[8:]),
}
}
// Establish the connection through Tor's SOCKS proxy.
dialer, err := proxy.SOCKS5("tcp", socksAddr, auth, proxy.Direct)
if err != nil {
return nil, err
}
return dialer.Dial("tcp", address)
}
// LookupHost performs DNS resolution on a given host via Tor's native resolver.
// Only IPv4 addresses are returned.
func LookupHost(host, socksAddr string) ([]string, error) {
ip, err := connmgr.TorLookupIP(host, socksAddr)
if err != nil {
return nil, err
}
// Only one IPv4 address is returned by the TorLookupIP function.
return []string{ip[0].String()}, nil
}
// LookupSRV uses Tor's SOCKS proxy to route DNS SRV queries. Tor does not
// natively support SRV queries so we must route all SRV queries through the
// proxy by connecting directly to a DNS server and querying it. The DNS server
// must have TCP resolution enabled for the given port.
func LookupSRV(service, proto, name, socksAddr, dnsServer string,
streamIsolation bool) (string, []*net.SRV, error) {
// Connect to the DNS server we'll be using to query SRV records.
conn, err := dial(dnsServer, socksAddr, streamIsolation)
if err != nil {
return "", nil, err
}
dnsConn := &dns.Conn{Conn: conn}
defer dnsConn.Close()
// Once connected, we'll construct the SRV request for the host
// following the format _service._proto.name. as described in RFC #2782.
host := fmt.Sprintf("_%s._%s.%s.", service, proto, name)
msg := new(dns.Msg).SetQuestion(host, dns.TypeSRV)
// Send the request to the DNS server and read its response.
if err := dnsConn.WriteMsg(msg); err != nil {
return "", nil, err
}
resp, err := dnsConn.ReadMsg()
if err != nil {
return "", nil, err
}
// We'll fail if we were unable to query the DNS server for our record.
if resp.Rcode != dns.RcodeSuccess {
return "", nil, fmt.Errorf("unable to query for SRV records: "+
"%s", dnsCodes[resp.Rcode])
}
// Retrieve the RR(s) of the Answer section.
var rrs []*net.SRV
for _, rr := range resp.Answer {
srv := rr.(*dns.SRV)
rrs = append(rrs, &net.SRV{
Target: srv.Target,
Port: srv.Port,
Priority: srv.Priority,
Weight: srv.Weight,
})
}
return "", rrs, nil
}
// ResolveTCPAddr uses Tor's proxy to resolve TCP addresses instead of the
// standard system resolver provided in the `net` package.
func ResolveTCPAddr(address, socksAddr string) (*net.TCPAddr, error) {
// Split host:port since the lookup function does not take a port.
host, port, err := net.SplitHostPort(address)
if err != nil {
return nil, err
}
ip, err := LookupHost(host, socksAddr)
if err != nil {
return nil, err
}
p, err := strconv.Atoi(port)
if err != nil {
return nil, err
}
return &net.TCPAddr{
IP: net.ParseIP(ip[0]),
Port: p,
}, nil
}
// ParseAddr parses an address from its string format to a net.Addr.
func ParseAddr(address, socksAddr string) (net.Addr, error) {
host, portStr, err := net.SplitHostPort(address)
if err != nil {
return nil, err
}
port, err := strconv.Atoi(portStr)
if err != nil {
return nil, err
}
if IsOnionHost(host) {
return &OnionAddr{OnionService: host, Port: port}, nil
}
return ResolveTCPAddr(address, socksAddr)
}
// IsOnionHost determines whether a host is part of an onion address.
func IsOnionHost(host string) bool {
// Note the starting index of the onion suffix in the host depending
// on its length.
var suffixIndex int
switch len(host) {
case V2Len:
suffixIndex = V2Len - OnionSuffixLen
case V3Len:
suffixIndex = V3Len - OnionSuffixLen
default:
return false
}
// Make sure the host ends with the ".onion" suffix.
if host[suffixIndex:] != OnionSuffix {
return false
}
// We'll now attempt to decode the host without its suffix, as the
// suffix includes invalid characters. This will tell us if the host is
// actually valid if successful.
host = host[:suffixIndex]
if _, err := Base32Encoding.DecodeString(host); err != nil {
return false
}
return true
}