AdGuardHome/internal/dnsforward/clientid.go

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package dnsforward
import (
"crypto/tls"
"fmt"
"path"
"strings"
"github.com/AdguardTeam/dnsproxy/proxy"
"github.com/lucas-clemente/quic-go"
)
const maxDomainPartLen = 64
// ValidateClientID returns an error if clientID is not a valid client ID.
func ValidateClientID(clientID string) (err error) {
if len(clientID) > maxDomainPartLen {
return fmt.Errorf("client id %q is too long, max: %d", clientID, maxDomainPartLen)
}
for i, r := range clientID {
if (r >= 'a' && r <= 'z') || (r >= '0' && r <= '9') || r == '-' {
continue
}
return fmt.Errorf("invalid char %q at index %d in client id %q", r, i, clientID)
}
return nil
}
// clientIDFromClientServerName extracts and validates a client ID. 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, cliSrvName string, strict bool) (clientID string, err error) {
if hostSrvName == cliSrvName {
return "", nil
}
if !strings.HasSuffix(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 {
return "", fmt.Errorf("invalid client id: %w", err)
}
return clientID, nil
}
// processClientIDHTTPS extracts the client's ID from the path of the
// client's DNS-over-HTTPS request.
func processClientIDHTTPS(ctx *dnsContext) (rc resultCode) {
pctx := ctx.proxyCtx
r := pctx.HTTPRequest
if r == nil {
ctx.err = fmt.Errorf("proxy ctx http request of proto %s is nil", pctx.Proto)
return resultCodeError
}
origPath := r.URL.Path
parts := strings.Split(path.Clean(origPath), "/")
if parts[0] == "" {
parts = parts[1:]
}
if len(parts) == 0 || parts[0] != "dns-query" {
ctx.err = fmt.Errorf("client id check: invalid path %q", origPath)
return resultCodeError
}
clientID := ""
switch len(parts) {
case 1:
// Just /dns-query, no client ID.
return resultCodeSuccess
case 2:
clientID = parts[1]
default:
ctx.err = fmt.Errorf("client id check: invalid path %q: extra parts", origPath)
return resultCodeError
}
err := ValidateClientID(clientID)
if err != nil {
ctx.err = fmt.Errorf("client id check: invalid client id: %w", err)
return resultCodeError
}
ctx.clientID = clientID
return resultCodeSuccess
}
// tlsConn is a narrow interface for *tls.Conn to simplify testing.
type tlsConn interface {
ConnectionState() (cs tls.ConnectionState)
}
// quicSession is a narrow interface for quic.Session to simplify testing.
type quicSession interface {
ConnectionState() (cs quic.ConnectionState)
}
// processClientID 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.
func processClientID(dctx *dnsContext) (rc resultCode) {
pctx := dctx.proxyCtx
proto := pctx.Proto
if proto == proxy.ProtoHTTPS {
return processClientIDHTTPS(dctx)
} else if proto != proxy.ProtoTLS && proto != proxy.ProtoQUIC {
return resultCodeSuccess
}
srvConf := dctx.srv.conf
hostSrvName := srvConf.TLSConfig.ServerName
if hostSrvName == "" {
return resultCodeSuccess
}
cliSrvName := ""
if proto == proxy.ProtoTLS {
conn := pctx.Conn
tc, ok := conn.(tlsConn)
if !ok {
dctx.err = fmt.Errorf("proxy ctx conn of proto %s is %T, want *tls.Conn", proto, conn)
return resultCodeError
}
cliSrvName = tc.ConnectionState().ServerName
} else if proto == proxy.ProtoQUIC {
qs, ok := pctx.QUICSession.(quicSession)
if !ok {
dctx.err = fmt.Errorf("proxy ctx quic session of proto %s is %T, want quic.Session", proto, pctx.QUICSession)
return resultCodeError
}
cliSrvName = qs.ConnectionState().ServerName
}
clientID, err := clientIDFromClientServerName(hostSrvName, cliSrvName, srvConf.StrictSNICheck)
if err != nil {
dctx.err = fmt.Errorf("client id check: %w", err)
return resultCodeError
}
dctx.clientID = clientID
return resultCodeSuccess
}