cloudflare/cloudflared
Publicmirrored from https://github.com/cloudflare/cloudflaredAvailable
tunneldns/https_upstream.go
105lines · modecode
| 1 | package tunneldns |
| 2 | |
| 3 | import ( |
| 4 | "bytes" |
| 5 | "crypto/tls" |
| 6 | "fmt" |
| 7 | "io/ioutil" |
| 8 | "net/http" |
| 9 | "net/url" |
| 10 | "time" |
| 11 | |
| 12 | "github.com/miekg/dns" |
| 13 | "github.com/pkg/errors" |
| 14 | log "github.com/sirupsen/logrus" |
| 15 | "golang.org/x/net/context" |
| 16 | "golang.org/x/net/http2" |
| 17 | ) |
| 18 | |
| 19 | const ( |
| 20 | defaultTimeout = 5 * time.Second |
| 21 | ) |
| 22 | |
| 23 | // UpstreamHTTPS is the upstream implementation for DNS over HTTPS service |
| 24 | type UpstreamHTTPS struct { |
| 25 | client *http.Client |
| 26 | endpoint *url.URL |
| 27 | } |
| 28 | |
| 29 | // NewUpstreamHTTPS creates a new DNS over HTTPS upstream from hostname |
| 30 | func NewUpstreamHTTPS(endpoint string) (Upstream, error) { |
| 31 | u, err := url.Parse(endpoint) |
| 32 | if err != nil { |
| 33 | return nil, err |
| 34 | } |
| 35 | |
| 36 | // Update TLS and HTTP client configuration |
| 37 | tls := &tls.Config{ServerName: u.Hostname()} |
| 38 | transport := &http.Transport{ |
| 39 | TLSClientConfig: tls, |
| 40 | DisableCompression: true, |
| 41 | MaxIdleConns: 1, |
| 42 | } |
| 43 | http2.ConfigureTransport(transport) |
| 44 | |
| 45 | client := &http.Client{ |
| 46 | Timeout: defaultTimeout, |
| 47 | Transport: transport, |
| 48 | } |
| 49 | |
| 50 | return &UpstreamHTTPS{client: client, endpoint: u}, nil |
| 51 | } |
| 52 | |
| 53 | // Exchange provides an implementation for the Upstream interface |
| 54 | func (u *UpstreamHTTPS) Exchange(ctx context.Context, query *dns.Msg) (*dns.Msg, error) { |
| 55 | queryBuf, err := query.Pack() |
| 56 | if err != nil { |
| 57 | return nil, errors.Wrap(err, "failed to pack DNS query") |
| 58 | } |
| 59 | |
| 60 | // No content negotiation for now, use DNS wire format |
| 61 | buf, backendErr := u.exchangeWireformat(queryBuf) |
| 62 | if backendErr == nil { |
| 63 | response := &dns.Msg{} |
| 64 | if err := response.Unpack(buf); err != nil { |
| 65 | return nil, errors.Wrap(err, "failed to unpack DNS response from body") |
| 66 | } |
| 67 | |
| 68 | response.Id = query.Id |
| 69 | return response, nil |
| 70 | } |
| 71 | |
| 72 | log.WithError(backendErr).Errorf("failed to connect to an HTTPS backend %q", u.endpoint) |
| 73 | return nil, backendErr |
| 74 | } |
| 75 | |
| 76 | // Perform message exchange with the default UDP wireformat defined in current draft |
| 77 | // https://datatracker.ietf.org/doc/draft-ietf-doh-dns-over-https |
| 78 | func (u *UpstreamHTTPS) exchangeWireformat(msg []byte) ([]byte, error) { |
| 79 | req, err := http.NewRequest("POST", u.endpoint.String(), bytes.NewBuffer(msg)) |
| 80 | if err != nil { |
| 81 | return nil, errors.Wrap(err, "failed to create an HTTPS request") |
| 82 | } |
| 83 | |
| 84 | req.Header.Add("Content-Type", "application/dns-udpwireformat") |
| 85 | req.Host = u.endpoint.Hostname() |
| 86 | |
| 87 | resp, err := u.client.Do(req) |
| 88 | if err != nil { |
| 89 | return nil, errors.Wrap(err, "failed to perform an HTTPS request") |
| 90 | } |
| 91 | |
| 92 | // Check response status code |
| 93 | defer resp.Body.Close() |
| 94 | if resp.StatusCode != http.StatusOK { |
| 95 | return nil, fmt.Errorf("returned status code %d", resp.StatusCode) |
| 96 | } |
| 97 | |
| 98 | // Read wireformat response from the body |
| 99 | buf, err := ioutil.ReadAll(resp.Body) |
| 100 | if err != nil { |
| 101 | return nil, errors.Wrap(err, "failed to read the response body") |
| 102 | } |
| 103 | |
| 104 | return buf, nil |
| 105 | } |