add config options for Deny CIDR and fallback policy

modules/caddyhttp/proxyprotocol/listenerwrapper.go

@@ -37,18 +37,59 @@ type ListenerWrapper struct {
 	// Allow is an optional list of CIDR ranges to
 	// allow/require PROXY headers from.
 	Allow []string `json:"allow,omitempty"`
+	allow []*net.IPNet
 
-	policies []goproxy.PolicyFunc
+	// Denby is an optional list of CIDR ranges to
+	// deny PROXY headers from.
+	Deny []string `json:"deny,omitempty"`
+	deny []*net.IPNet
+
+	// Accepted values are: ignore, use, reject, require, skip
+	// default: ignore
+	// Policy definitions are here: https://pkg.go.dev/github.com/pires/go-proxyproto@v0.7.0#Policy
+	FallbackPolicy Policy `json:"fallback_policy,omitempty"`
+
+	policy goproxy.PolicyFunc
 }
 
 // Provision sets up the listener wrapper.
 func (pp *ListenerWrapper) Provision(ctx caddy.Context) error {
-	if len(pp.Allow) > 0 {
-		allowlist, err := goproxy.LaxWhiteListPolicy(pp.Allow)
+	for _, cidr := range pp.Allow {
+		_, ipnet, err := net.ParseCIDR(cidr)
 		if err != nil {
 			return err
 		}
-		pp.policies = append(pp.policies, allowlist)
+		pp.allow = append(pp.allow, ipnet)
+	}
+	for _, cidr := range pp.Deny {
+		_, ipnet, err := net.ParseCIDR(cidr)
+		if err != nil {
+			return err
+		}
+		pp.deny = append(pp.deny, ipnet)
+	}
+	pp.policy = func(upstream net.Addr) (goproxy.Policy, error) {
+		ret := pp.FallbackPolicy
+		host, _, err := net.SplitHostPort(upstream.String())
+		if err != nil {
+			return goproxy.REJECT, err
+		}
+		ip := net.ParseIP(host)
+		if ip == nil {
+			return goproxy.REJECT, err
+		}
+		for _, ipnet := range pp.deny {
+			if ipnet.Contains(ip) {
+				return goproxy.REJECT, nil
+			}
+		}
+		for _, ipnet := range pp.allow {
+			if ipnet.Contains(ip) {
+				ret = PolicyUSE
+				break
+			}
+		}
+		return policyToGoProxyPolicy[ret], nil
 	}
 	return nil
 }
@@ -59,8 +100,6 @@ func (pp *ListenerWrapper) WrapListener(l net.Listener) net.Listener {
 		Listener:          l,
 		ReadHeaderTimeout: time.Duration(pp.Timeout),
 	}
-	if len(pp.policies) > 0 {
-		pl.Policy = pp.policies[0]
-	}
+	pl.Policy = pp.policy
 	return pl
 }

modules/caddyhttp/proxyprotocol/module.go

@@ -35,6 +35,8 @@ func (ListenerWrapper) CaddyModule() caddy.ModuleInfo {
 //	proxy_protocol {
 //		timeout <duration>
 //		allow <IPs...>
+//		deny <IPs...>
+//		fallback_policy <policy>
 //	}
 func (w *ListenerWrapper) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
 	for d.Next() {
@@ -57,7 +59,17 @@ func (w *ListenerWrapper) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
 
 			case "allow":
 				w.Allow = append(w.Allow, d.RemainingArgs()...)
-
+			case "deny":
+				w.Deny = append(w.Deny, d.RemainingArgs()...)
+			case "fallback_policy":
+				if !d.NextArg() {
+					return d.ArgErr()
+				}
+				p, err := parsePolicy(d.Val())
+				if err != nil {
+					return d.WrapErr(err)
+				}
+				w.FallbackPolicy = p
 			default:
 				return d.ArgErr()
 			}

modules/caddyhttp/proxyprotocol/policy.go

@@ -0,0 +1,82 @@
+package proxyprotocol
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+
+	goproxy "github.com/pires/go-proxyproto"
+)
+
+type Policy int
+
+// as defined in: https://pkg.go.dev/github.com/pires/go-proxyproto@v0.7.0#Policy
+const (
+	// IGNORE address from PROXY header, but accept connection
+	PolicyIGNORE Policy = iota
+	// USE address from PROXY header
+	PolicyUSE
+	// REJECT connection when PROXY header is sent
+	// Note: even though the first read on the connection returns an error if
+	// a PROXY header is present, subsequent reads do not. It is the task of
+	// the code using the connection to handle that case properly.
+	PolicyREJECT
+	// REQUIRE connection to send PROXY header, reject if not present
+	// Note: even though the first read on the connection returns an error if
+	// a PROXY header is not present, subsequent reads do not. It is the task
+	// of the code using the connection to handle that case properly.
+	PolicyREQUIRE
+	// SKIP accepts a connection without requiring the PROXY header
+	// Note: an example usage can be found in the SkipProxyHeaderForCIDR
+	// function.
+	PolicySKIP
+)
+
+var policyToGoProxyPolicy = map[Policy]goproxy.Policy{
+	PolicyUSE:     goproxy.USE,
+	PolicyIGNORE:  goproxy.IGNORE,
+	PolicyREJECT:  goproxy.REJECT,
+	PolicyREQUIRE: goproxy.REQUIRE,
+	PolicySKIP:    goproxy.SKIP,
+}
+
+var policyMap = map[Policy]string{
+	PolicyUSE:     "USE",
+	PolicyIGNORE:  "IGNORE",
+	PolicyREJECT:  "REJECT",
+	PolicyREQUIRE: "REQUIRE",
+	PolicySKIP:    "SKIP",
+}
+
+var policyMapRev = map[string]Policy{
+	"USE":     PolicyUSE,
+	"IGNORE":  PolicyIGNORE,
+	"REJECT":  PolicyREJECT,
+	"REQUIRE": PolicyREQUIRE,
+	"SKIP":    PolicySKIP,
+}
+
+// MarshalText implements the text marshaller method.
+func (x Policy) MarshalText() ([]byte, error) {
+	return []byte(policyMap[x]), nil
+}
+
+// UnmarshalText implements the text unmarshaller method.
+func (x *Policy) UnmarshalText(text []byte) error {
+	name := string(text)
+	tmp, err := parsePolicy(name)
+	if err != nil {
+		return err
+	}
+	*x = tmp
+	return nil
+}
+
+func parsePolicy(name string) (Policy, error) {
+	if x, ok := policyMapRev[strings.ToUpper(name)]; ok {
+		return x, nil
+	}
+	return Policy(0), fmt.Errorf("%s is %w", name, errInvalidPolicy)
+}
+
+var errInvalidPolicy = errors.New("invalid policy")