commit 7541763c24ba6f08003447e7b4a4935e1eadce28
Author: afonso <afonso@francof.net>
Date:   Sat Aug 31 11:36:28 2024 +0100

    First commit

diff --git a/doh-proxy.go b/doh-proxy.go
new file mode 100644
index 0000000..da5fb33
--- /dev/null
+++ b/doh-proxy.go
@@ -0,0 +1,206 @@
+package main
+
+import (
+	"bytes"
+	"crypto/tls"
+	"flag"
+	"io"
+	"log"
+	"net"
+	"net/http"
+	"os"
+	"time"
+
+	"github.com/miekg/dns"
+	"golang.org/x/net/http2"
+)
+
+// ProtocolType represents the type of DNS protocol
+type ProtocolType int
+
+const (
+	// Enum-like constants for ProtocolType
+	TCP ProtocolType = iota
+	UDP
+)
+
+// DoHProxy represents the DNS-over-HTTPS proxy
+type DoHProxy struct {
+	listenAddress string
+	port          string
+	upstreamURLs  []string
+	client        *http.Client
+	protocols     []ProtocolType // List of protocols to listen on
+	logRequests   bool
+}
+
+// NewDoHProxy initializes a new DoHProxy instance
+func NewDoHProxy(listenAddress, port string, upstreamURLs []string, protocols []ProtocolType, logRequests bool) *DoHProxy {
+	// HTTP client with support for HTTP/2
+	transport := &http.Transport{
+		TLSClientConfig: &tls.Config{},
+	}
+
+	http2.ConfigureTransport(transport) // Enable HTTP/2 support
+
+	// HTTP client for DoH requests
+	client := &http.Client{
+		Transport: transport,
+		Timeout:   5 * time.Second, // Set a timeout for requests
+	}
+
+	return &DoHProxy{
+		listenAddress: listenAddress,
+		port:          port,
+		upstreamURLs:  upstreamURLs,
+		client:        client,
+		protocols:     protocols,
+		logRequests:   logRequests,
+	}
+}
+
+// HandleDNSRequest handles incoming DNS requests and forwards them to DoH servers
+func (p *DoHProxy) HandleDNSRequest(w dns.ResponseWriter, r *dns.Msg) {
+	dnsQuery, err := r.Pack()
+	if err != nil {
+		log.Printf("Failed to pack DNS request: %v", err)
+		return
+	}
+
+	var response *http.Response
+	var currentUpstream string
+
+	// Send the DNS query to each upstream DoH server until one succeeds
+	for _, upstream := range p.upstreamURLs {
+		req, _ := http.NewRequest("POST", upstream, bytes.NewBuffer(dnsQuery))
+		req.Header.Set("Content-Type", "application/dns-message")
+		req.Header.Set("Accept", "application/dns-message")
+
+		response, err = p.client.Do(req)
+		if err == nil && response.StatusCode == http.StatusOK {
+			currentUpstream = upstream
+			break
+		}
+	}
+	if currentUpstream == "" {
+		if p.logRequests {
+			log.Printf("Failed to query any upstream")
+		}
+		return
+	}
+	if response == nil {
+		log.Printf("All upstream DoH servers failed")
+		dns.HandleFailed(w, r)
+		return
+	}
+	defer response.Body.Close()
+
+	// Read the response body
+	body, err := io.ReadAll(response.Body)
+	if err != nil {
+		log.Printf("Failed to read response from upstream: %v", err)
+		dns.HandleFailed(w, r)
+		return
+	}
+
+	// Unpack the DNS response and send it back to the client
+	dnsResponse := new(dns.Msg)
+	if err := dnsResponse.Unpack(body); err != nil {
+		log.Printf("Failed to unpack DNS response: %v", err)
+		dns.HandleFailed(w, r)
+		return
+	}
+	if p.logRequests {
+		log.Println("Successfully proxied request through ", currentUpstream)
+	}
+	w.WriteMsg(dnsResponse)
+
+}
+
+// Run starts the DNS server and listens for incoming queries based on the protocol
+func (p *DoHProxy) Run() {
+	for _, proto := range p.protocols {
+		switch proto {
+		case TCP:
+			go func() {
+				server := &dns.Server{Addr: net.JoinHostPort(p.listenAddress, p.port), Net: "tcp"}
+				dns.HandleFunc(".", p.HandleDNSRequest)
+
+				log.Printf("Starting DoH Proxy on %s:%s over TCP", p.listenAddress, p.port)
+				if err := server.ListenAndServe(); err != nil {
+					log.Fatalf("Failed to start DNS server (TCP): %v", err)
+				}
+			}()
+		case UDP:
+			go func() {
+				server := &dns.Server{Addr: net.JoinHostPort(p.listenAddress, p.port), Net: "udp"}
+				dns.HandleFunc(".", p.HandleDNSRequest)
+
+				log.Printf("Starting DoH Proxy on %s:%s over UDP", p.listenAddress, p.port)
+				if err := server.ListenAndServe(); err != nil {
+					log.Fatalf("Failed to start DNS server (UDP): %v", err)
+				}
+			}()
+		}
+	}
+
+	// Keep the main goroutine running indefinitely
+	select {}
+}
+
+func main() {
+	// Define flags using the flag library
+	listenAddress := flag.String("l", "127.0.0.1", "Listen address for the DNS server")
+	port := flag.String("p", "53", "Port for the DNS server")
+
+	// Define flags for protocols
+	tcpFlag := flag.Bool("tcp", false, "Listen on TCP")
+	udpFlag := flag.Bool("udp", false, "Listen on UDP")
+
+	// Define flag for logging
+	logFlag := flag.Bool("log", false, "Log each request proxied through an upstream")
+
+	var upstreamURLs []string
+
+	// Custom flag for handling multiple upstream URLs
+	flag.Func("u", `Upstream DoH server URL (can be specified multiple times)
+Example:
+    -u https://dns.quad9.net/dns-query -u https://1.1.1.1/dns-query
+WARNING:
+    If this is your system's default DNS resolver 
+    and the server URL is a domain name, at least one other
+    DNS server after this one must be specified as an IP address
+    in order to resolve the domain name of the first one.`, func(value string) error {
+		log.Printf("Added %s as an upstream DoH server\n", value)
+		upstreamURLs = append(upstreamURLs, value)
+		return nil
+	})
+
+	// Parse the flags
+	flag.Parse()
+
+	// Check if at least one upstream DoH URL is provided
+	if len(upstreamURLs) == 0 {
+		flag.PrintDefaults()
+		os.Exit(1)
+	}
+
+	// Determine which protocols to use
+	var protocols []ProtocolType
+	if *tcpFlag {
+		protocols = append(protocols, TCP)
+	}
+	if *udpFlag {
+		protocols = append(protocols, UDP)
+	}
+	if !*tcpFlag && !*udpFlag {
+		// Default to both if no specific flag is provided
+		protocols = []ProtocolType{TCP, UDP}
+	}
+	if *logFlag {
+		log.Println("Logging requests")
+	}
+	// Initialize and run the DoH proxy
+	proxy := NewDoHProxy(*listenAddress, *port, upstreamURLs, protocols, *logFlag)
+	proxy.Run()
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..559ec11
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,16 @@
+module dohproxy
+
+go 1.23.0
+
+require (
+	github.com/miekg/dns v1.1.62
+	golang.org/x/net v0.28.0
+)
+
+require (
+	golang.org/x/mod v0.18.0 // indirect
+	golang.org/x/sync v0.8.0 // indirect
+	golang.org/x/sys v0.23.0 // indirect
+	golang.org/x/text v0.17.0 // indirect
+	golang.org/x/tools v0.22.0 // indirect
+)
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..1fabb37
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,14 @@
+github.com/miekg/dns v1.1.62 h1:cN8OuEF1/x5Rq6Np+h1epln8OiyPWV+lROx9LxcGgIQ=
+github.com/miekg/dns v1.1.62/go.mod h1:mvDlcItzm+br7MToIKqkglaGhlFMHJ9DTNNWONWXbNQ=
+golang.org/x/mod v0.18.0 h1:5+9lSbEzPSdWkH32vYPBwEpX8KwDbM52Ud9xBUvNlb0=
+golang.org/x/mod v0.18.0/go.mod h1:hTbmBsO62+eylJbnUtE2MGJUyE7QWk4xUqPFrRgJ+7c=
+golang.org/x/net v0.28.0 h1:a9JDOJc5GMUJ0+UDqmLT86WiEy7iWyIhz8gz8E4e5hE=
+golang.org/x/net v0.28.0/go.mod h1:yqtgsTWOOnlGLG9GFRrK3++bGOUEkNBoHZc8MEDWPNg=
+golang.org/x/sync v0.8.0 h1:3NFvSEYkUoMifnESzZl15y791HH1qU2xm6eCJU5ZPXQ=
+golang.org/x/sync v0.8.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
+golang.org/x/sys v0.23.0 h1:YfKFowiIMvtgl1UERQoTPPToxltDeZfbj4H7dVUCwmM=
+golang.org/x/sys v0.23.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/text v0.17.0 h1:XtiM5bkSOt+ewxlOE/aE/AKEHibwj/6gvWMl9Rsh0Qc=
+golang.org/x/text v0.17.0/go.mod h1:BuEKDfySbSR4drPmRPG/7iBdf8hvFMuRexcpahXilzY=
+golang.org/x/tools v0.22.0 h1:gqSGLZqv+AI9lIQzniJ0nZDRG5GBPsSi+DRNHWNz6yA=
+golang.org/x/tools v0.22.0/go.mod h1:aCwcsjqvq7Yqt6TNyX7QMU2enbQ/Gt0bo6krSeEri+c=