feat: add initial implementation of osiris, the TLS terminator for Anubis

Signed-off-by: Xe Iaso <me@xeiaso.net>

cmd/osiris/internal/entrypoint/h2c.go

@@ -0,0 +1,33 @@
+package entrypoint
+
+import (
+	"crypto/tls"
+	"net"
+	"net/http"
+	"net/http/httputil"
+	"net/url"
+
+	"golang.org/x/net/http2"
+)
+
+func newH2CReverseProxy(target *url.URL) *httputil.ReverseProxy {
+	director := func(req *http.Request) {
+		req.URL.Scheme = target.Scheme
+		req.URL.Host = target.Host
+		req.Host = target.Host
+	}
+
+	// Use h2c transport
+	transport := &http2.Transport{
+		AllowHTTP: true,
+		DialTLS: func(network, addr string, cfg *tls.Config) (net.Conn, error) {
+			// Just do plain TCP (h2c)
+			return net.Dial(network, addr)
+		},
+	}
+
+	return &httputil.ReverseProxy{
+		Director:  director,
+		Transport: transport,
+	}
+}