AdGuardHome/internal/dnsforward/clientid.go

203 lines
5.3 KiB
Go

package dnsforward
import (
"crypto/tls"
"fmt"
"path"
"strings"
"github.com/AdguardTeam/dnsproxy/proxy"
"github.com/AdguardTeam/golibs/errors"
"github.com/AdguardTeam/golibs/netutil"
"github.com/lucas-clemente/quic-go"
)
// ValidateClientID returns an error if id is not a valid ClientID.
func ValidateClientID(id string) (err error) {
err = netutil.ValidateDomainNameLabel(id)
if err != nil {
// Replace the domain name label wrapper with our own.
return fmt.Errorf("invalid clientid %q: %w", id, errors.Unwrap(err))
}
return nil
}
// hasLabelSuffix returns true if s ends with suffix preceded by a dot. It's
// a helper function to prevent unnecessary allocations in code like:
//
// if strings.HasSuffix(s, "." + suffix) { /* … */ }
//
// s must be longer than suffix.
func hasLabelSuffix(s, suffix string) (ok bool) {
return strings.HasSuffix(s, suffix) && s[len(s)-len(suffix)-1] == '.'
}
// clientIDFromClientServerName extracts and validates a ClientID. hostSrvName
// is the server name of the host. cliSrvName is the server name as sent by the
// client. When strict is true, and client and host server name don't match,
// clientIDFromClientServerName will return an error.
func clientIDFromClientServerName(
hostSrvName string,
cliSrvName string,
strict bool,
) (clientID string, err error) {
if hostSrvName == cliSrvName {
return "", nil
}
if !hasLabelSuffix(cliSrvName, hostSrvName) {
if !strict {
return "", nil
}
return "", fmt.Errorf(
"client server name %q doesn't match host server name %q",
cliSrvName,
hostSrvName,
)
}
clientID = cliSrvName[:len(cliSrvName)-len(hostSrvName)-1]
err = ValidateClientID(clientID)
if err != nil {
// Don't wrap the error, because it's informative enough as is.
return "", err
}
return strings.ToLower(clientID), nil
}
// clientIDFromDNSContextHTTPS extracts the client's ID from the path of the
// client's DNS-over-HTTPS request.
func clientIDFromDNSContextHTTPS(pctx *proxy.DNSContext) (clientID string, err error) {
r := pctx.HTTPRequest
if r == nil {
return "", fmt.Errorf(
"proxy ctx http request of proto %s is nil",
pctx.Proto,
)
}
origPath := r.URL.Path
parts := strings.Split(path.Clean(origPath), "/")
if parts[0] == "" {
parts = parts[1:]
}
if len(parts) == 0 || parts[0] != "dns-query" {
return "", fmt.Errorf("clientid check: invalid path %q", origPath)
}
switch len(parts) {
case 1:
// Just /dns-query, no ClientID.
return "", nil
case 2:
clientID = parts[1]
default:
return "", fmt.Errorf("clientid check: invalid path %q: extra parts", origPath)
}
err = ValidateClientID(clientID)
if err != nil {
return "", fmt.Errorf("clientid check: %w", err)
}
return strings.ToLower(clientID), nil
}
// tlsConn is a narrow interface for *tls.Conn to simplify testing.
type tlsConn interface {
ConnectionState() (cs tls.ConnectionState)
}
// quicConnection is a narrow interface for quic.Connection to simplify testing.
type quicConnection interface {
ConnectionState() (cs quic.ConnectionState)
}
// clientIDFromDNSContext extracts the client's ID from the server name of the
// client's DoT or DoQ request or the path of the client's DoH. If the protocol
// is not one of these, clientID is an empty string and err is nil.
func (s *Server) clientIDFromDNSContext(pctx *proxy.DNSContext) (clientID string, err error) {
proto := pctx.Proto
if proto == proxy.ProtoHTTPS {
clientID, err = clientIDFromDNSContextHTTPS(pctx)
if err != nil {
return "", fmt.Errorf("checking url: %w", err)
} else if clientID != "" {
return clientID, nil
}
// Go on and check the domain name as well.
} else if proto != proxy.ProtoTLS && proto != proxy.ProtoQUIC {
return "", nil
}
hostSrvName := s.conf.ServerName
if hostSrvName == "" {
return "", nil
}
cliSrvName, err := clientServerName(pctx, proto)
if err != nil {
return "", err
}
clientID, err = clientIDFromClientServerName(
hostSrvName,
cliSrvName,
s.conf.StrictSNICheck,
)
if err != nil {
return "", fmt.Errorf("clientid check: %w", err)
}
return clientID, nil
}
// clientServerName returns the TLS server name based on the protocol.
func clientServerName(pctx *proxy.DNSContext, proto proxy.Proto) (srvName string, err error) {
switch proto {
case proxy.ProtoHTTPS:
// github.com/lucas-clemente/quic-go seems to not populate the TLS
// field. So, if the request comes over HTTP/3, use the Host header
// value as the server name.
//
// See https://github.com/lucas-clemente/quic-go/issues/2879.
//
// TODO(a.garipov): Remove this crutch once they fix it.
r := pctx.HTTPRequest
if r.ProtoAtLeast(3, 0) {
var host string
host, err = netutil.SplitHost(r.Host)
if err != nil {
return "", fmt.Errorf("parsing host: %w", err)
}
srvName = host
} else if connState := r.TLS; connState != nil {
srvName = r.TLS.ServerName
}
case proxy.ProtoQUIC:
qConn := pctx.QUICConnection
conn, ok := qConn.(quicConnection)
if !ok {
return "", fmt.Errorf("pctx conn of proto %s is %T, want quic.Connection", proto, qConn)
}
srvName = conn.ConnectionState().TLS.ServerName
case proxy.ProtoTLS:
conn := pctx.Conn
tc, ok := conn.(tlsConn)
if !ok {
return "", fmt.Errorf("pctx conn of proto %s is %T, want *tls.Conn", proto, conn)
}
srvName = tc.ConnectionState().ServerName
}
return srvName, nil
}