reverseproxy: Refactor dial address parsing, augment command parsing (#4616)

1 files changed, 112 insertions, 0 deletions

diff --git a/modules/caddyhttp/reverseproxy/addresses.go b/modules/caddyhttp/reverseproxy/addresses.go
new file mode 100644
index 0000000..f15ed76
--- /dev/null
+++ b/modules/caddyhttp/reverseproxy/addresses.go
@@ -0,0 +1,112 @@
+// Copyright 2015 Matthew Holt and The Caddy Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package reverseproxy
+
+import (
+	"fmt"
+	"net"
+	"net/url"
+	"strings"
+
+	"github.com/caddyserver/caddy/v2"
+)
+
+// parseUpstreamDialAddress parses configuration inputs for
+// the dial address, including support for a scheme in front
+// as a shortcut for the port number, and a network type,
+// for example 'unix' to dial a unix socket.
+//
+// TODO: the logic in this function is kind of sensitive, we
+// need to write tests before making any more changes to it
+func parseUpstreamDialAddress(upstreamAddr string) (string, string, error) {
+	var network, scheme, host, port string
+
+	if strings.Contains(upstreamAddr, "://") {
+		// we get a parsing error if a placeholder is specified
+		// so we return a more user-friendly error message instead
+		// to explain what to do instead
+		if strings.Contains(upstreamAddr, "{") {
+			return "", "", fmt.Errorf("due to parsing difficulties, placeholders are not allowed when an upstream address contains a scheme")
+		}
+
+		toURL, err := url.Parse(upstreamAddr)
+		if err != nil {
+			return "", "", fmt.Errorf("parsing upstream URL: %v", err)
+		}
+
+		// there is currently no way to perform a URL rewrite between choosing
+		// a backend and proxying to it, so we cannot allow extra components
+		// in backend URLs
+		if toURL.Path != "" || toURL.RawQuery != "" || toURL.Fragment != "" {
+			return "", "", fmt.Errorf("for now, URLs for proxy upstreams only support scheme, host, and port components")
+		}
+
+		// ensure the port and scheme aren't in conflict
+		urlPort := toURL.Port()
+		if toURL.Scheme == "http" && urlPort == "443" {
+			return "", "", fmt.Errorf("upstream address has conflicting scheme (http://) and port (:443, the HTTPS port)")
+		}
+		if toURL.Scheme == "https" && urlPort == "80" {
+			return "", "", fmt.Errorf("upstream address has conflicting scheme (https://) and port (:80, the HTTP port)")
+		}
+		if toURL.Scheme == "h2c" && urlPort == "443" {
+			return "", "", fmt.Errorf("upstream address has conflicting scheme (h2c://) and port (:443, the HTTPS port)")
+		}
+
+		// if port is missing, attempt to infer from scheme
+		if toURL.Port() == "" {
+			var toPort string
+			switch toURL.Scheme {
+			case "", "http", "h2c":
+				toPort = "80"
+			case "https":
+				toPort = "443"
+			}
+			toURL.Host = net.JoinHostPort(toURL.Hostname(), toPort)
+		}
+
+		scheme, host, port = toURL.Scheme, toURL.Hostname(), toURL.Port()
+	} else {
+		// extract network manually, since caddy.ParseNetworkAddress() will always add one
+		if idx := strings.Index(upstreamAddr, "/"); idx >= 0 {
+			network = strings.ToLower(strings.TrimSpace(upstreamAddr[:idx]))
+			upstreamAddr = upstreamAddr[idx+1:]
+		}
+		var err error
+		host, port, err = net.SplitHostPort(upstreamAddr)
+		if err != nil {
+			host = upstreamAddr
+		}
+		// we can assume a port if only a hostname is specified, but use of a
+		// placeholder without a port likely means a port will be filled in
+		if port == "" && !strings.Contains(host, "{") {
+			port = "80"
+		}
+	}
+
+	// for simplest possible config, we only need to include
+	// the network portion if the user specified one
+	if network != "" {
+		return caddy.JoinNetworkAddress(network, host, port), scheme, nil
+	}
+
+	// if the host is a placeholder, then we don't want to join with an empty port,
+	// because that would just append an extra ':' at the end of the address.
+	if port == "" && strings.Contains(host, "{") {
+		return host, scheme, nil
+	}
+
+	return net.JoinHostPort(host, port), scheme, nil
+}