support authenticating with SHA-256 digest (#524)

pkg/auth/www_authenticate.go

@@ -0,0 +1,23 @@
+package auth
+
+import (
+	"github.com/bluenviron/gortsplib/v4/pkg/base"
+	"github.com/bluenviron/gortsplib/v4/pkg/headers"
+)
+
+// GenerateWWWAuthenticate generates a WWW-Authenticate header.
+func GenerateWWWAuthenticate(methods []headers.AuthMethod, realm string, nonce string) base.HeaderValue {
+	if methods == nil {
+		methods = []headers.AuthMethod{headers.AuthDigestSHA256, headers.AuthDigestMD5, headers.AuthBasic}
+	}
+
+	var ret base.HeaderValue
+	for _, m := range methods {
+		ret = append(ret, headers.Authenticate{
+			Method: m,
+			Realm:  realm,
+			Nonce:  nonce, // used only by digest
+		}.Marshal()...)
+	}
+	return ret
+}