98 lines
2.5 KiB
Go
98 lines
2.5 KiB
Go
package tunneldns
|
|
|
|
import (
|
|
"bytes"
|
|
"crypto/tls"
|
|
"fmt"
|
|
"io/ioutil"
|
|
"net/http"
|
|
"net/url"
|
|
"time"
|
|
|
|
"github.com/miekg/dns"
|
|
"github.com/pkg/errors"
|
|
log "github.com/sirupsen/logrus"
|
|
"golang.org/x/net/context"
|
|
)
|
|
|
|
const (
|
|
defaultTimeout = 5 * time.Second
|
|
)
|
|
|
|
// UpstreamHTTPS is the upstream implementation for DNS over HTTPS service
|
|
type UpstreamHTTPS struct {
|
|
client *http.Client
|
|
endpoint *url.URL
|
|
}
|
|
|
|
// NewUpstreamHTTPS creates a new DNS over HTTPS upstream from hostname
|
|
func NewUpstreamHTTPS(endpoint string) (Upstream, error) {
|
|
u, err := url.Parse(endpoint)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// Update TLS and HTTP client configuration
|
|
tls := &tls.Config{ServerName: u.Hostname()}
|
|
client := &http.Client{
|
|
Timeout: time.Second * defaultTimeout,
|
|
Transport: &http.Transport{TLSClientConfig: tls},
|
|
}
|
|
|
|
return &UpstreamHTTPS{client: client, endpoint: u}, nil
|
|
}
|
|
|
|
// Exchange provides an implementation for the Upstream interface
|
|
func (u *UpstreamHTTPS) Exchange(ctx context.Context, query *dns.Msg) (*dns.Msg, error) {
|
|
queryBuf, err := query.Pack()
|
|
if err != nil {
|
|
return nil, errors.Wrap(err, "failed to pack DNS query")
|
|
}
|
|
|
|
// No content negotiation for now, use DNS wire format
|
|
buf, backendErr := u.exchangeWireformat(queryBuf)
|
|
if backendErr == nil {
|
|
response := &dns.Msg{}
|
|
if err := response.Unpack(buf); err != nil {
|
|
return nil, errors.Wrap(err, "failed to unpack DNS response from body")
|
|
}
|
|
|
|
response.Id = query.Id
|
|
return response, nil
|
|
}
|
|
|
|
log.WithError(backendErr).Errorf("failed to connect to an HTTPS backend %q", u.endpoint)
|
|
return nil, backendErr
|
|
}
|
|
|
|
// Perform message exchange with the default UDP wireformat defined in current draft
|
|
// https://datatracker.ietf.org/doc/draft-ietf-doh-dns-over-https
|
|
func (u *UpstreamHTTPS) exchangeWireformat(msg []byte) ([]byte, error) {
|
|
req, err := http.NewRequest("POST", u.endpoint.String(), bytes.NewBuffer(msg))
|
|
if err != nil {
|
|
return nil, errors.Wrap(err, "failed to create an HTTPS request")
|
|
}
|
|
|
|
req.Header.Add("Content-Type", "application/dns-udpwireformat")
|
|
req.Host = u.endpoint.Hostname()
|
|
|
|
resp, err := u.client.Do(req)
|
|
if err != nil {
|
|
return nil, errors.Wrap(err, "failed to perform an HTTPS request")
|
|
}
|
|
|
|
// Check response status code
|
|
defer resp.Body.Close()
|
|
if resp.StatusCode != http.StatusOK {
|
|
return nil, fmt.Errorf("returned status code %d", resp.StatusCode)
|
|
}
|
|
|
|
// Read wireformat response from the body
|
|
buf, err := ioutil.ReadAll(resp.Body)
|
|
if err != nil {
|
|
return nil, errors.Wrap(err, "failed to read the response body")
|
|
}
|
|
|
|
return buf, nil
|
|
}
|