identifier, policy, va: Remove/reject scope zone from IPv6 addresses (#8294)

Followup to #8293
Fixes #8292

identifier/identifier.go

@@ -118,7 +118,7 @@ func NewIP(ip netip.Addr) ACMEIdentifier {
 		// RFC 8738, Sec. 3: The identifier value MUST contain the textual form
 		// of the address as defined in RFC 1123, Sec. 2.1 for IPv4 and in RFC
 		// 5952, Sec. 4 for IPv6.
-		Value: ip.String(),
+		Value: ip.WithZone("").String(),
 	}
 }
 

identifier/identifier_test.go

@@ -10,6 +10,39 @@ import (
 	"testing"
 )
 
+func TestNewIP(t *testing.T) {
+	cases := []struct {
+		name string
+		ip   netip.Addr
+		want ACMEIdentifier
+	}{
+		{
+			name: "IPv4 address",
+			ip:   netip.MustParseAddr("9.9.9.9"),
+			want: ACMEIdentifier{Type: TypeIP, Value: "9.9.9.9"},
+		},
+		{
+			name: "IPv6 address",
+			ip:   netip.MustParseAddr("fe80::cafe"),
+			want: ACMEIdentifier{Type: TypeIP, Value: "fe80::cafe"},
+		},
+		{
+			name: "IPv6 address with scope zone",
+			ip:   netip.MustParseAddr("fe80::cafe%lo"),
+			want: ACMEIdentifier{Type: TypeIP, Value: "fe80::cafe"},
+		},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			got := NewIP(tc.ip)
+			if got != tc.want {
+				t.Errorf("NewIP(%#v) = %#v, but want %#v", tc.ip, got, tc.want)
+			}
+		})
+	}
+}
+
 // TestFromX509 tests FromCert and FromCSR, which are fromX509's public
 // wrappers.
 func TestFromX509(t *testing.T) {

policy/pa.go

@@ -326,6 +326,7 @@ func ValidDomain(domain string) error {
 // ValidIP checks that an IP address:
 //   - isn't empty
 //   - is an IPv4 or IPv6 address
+//   - doesn't contain a scope zone (RFC 4007)
 //   - isn't in an IANA special-purpose address registry
 //
 // It does NOT ensure that the IP address is absent from any PA blocked lists.
@@ -340,7 +341,7 @@ func ValidIP(ip string) error {
 	// 5952, Sec. 4 for IPv6.") ParseAddr() will accept a non-compliant but
 	// otherwise valid string; String() will output a compliant string.
 	parsedIP, err := netip.ParseAddr(ip)
-	if err != nil || parsedIP.String() != ip {
+	if err != nil || parsedIP.WithZone("").String() != ip {
 		return errIPInvalid
 	}
 
@@ -477,6 +478,7 @@ func (pa *AuthorityImpl) WillingToIssue(idents identifier.ACMEIdentifiers) error
 //
 // For IP identifiers:
 //   - MUST match the syntax of an IP address
+//   - MUST NOT contain a scope zone (RFC 4007)
 //   - MUST NOT be in an IANA special-purpose address registry
 //
 // If multiple identifiers are invalid, the error will contain suberrors

policy/pa_test.go

@@ -136,6 +136,8 @@ func TestWellFormedIdentifiers(t *testing.T) {
 		{identifier.ACMEIdentifier{Type: "ip", Value: `1.1.168.192.in-addr.arpa`}, errIPInvalid}, // reverse DNS
 
 		// Unexpected IPv6 variants
+		{identifier.ACMEIdentifier{Type: "ip", Value: `2602:80a:6000:abad:cafe::1%lo`}, errIPInvalid},                                             // scope zone (RFC 4007)
+		{identifier.ACMEIdentifier{Type: "ip", Value: `2602:80a:6000:abad:cafe::1%`}, errIPInvalid},                                               // empty scope zone (RFC 4007)
 		{identifier.ACMEIdentifier{Type: "ip", Value: `3fff:aaa:a:c0ff:ee:a:bad:deed:ffff`}, errIPInvalid},                                        // extra octet
 		{identifier.ACMEIdentifier{Type: "ip", Value: `3fff:aaa:a:c0ff:ee:a:bad:mead`}, errIPInvalid},                                             // character out of range
 		{identifier.ACMEIdentifier{Type: "ip", Value: `2001:db8::/32`}, errIPInvalid},                                                             // with CIDR

va/http.go

@@ -338,6 +338,10 @@ func (va *ValidationAuthorityImpl) extractRequestTarget(req *http.Request) (iden
 
 	reqIP, err := netip.ParseAddr(reqHost)
 	if err == nil {
+		// Reject IPv6 addresses with a scope zone (RFCs 4007 & 6874)
+		if reqIP.Zone() != "" {
+			return identifier.ACMEIdentifier{}, 0, berrors.ConnectionFailureError("Invalid host in redirect target: contains scope zone")
+		}
 		err := va.isReservedIPFunc(reqIP)
 		if err != nil {
 			return identifier.ACMEIdentifier{}, 0, berrors.ConnectionFailureError("Invalid host in redirect target: %s", err)

va/http_test.go

@@ -360,6 +360,14 @@ func TestExtractRequestTarget(t *testing.T) {
 			ExpectedError: fmt.Errorf("Invalid host in redirect target: " +
 				"IP address is in a reserved address block: [RFC9637]: Documentation"),
 		},
+		{
+			Name: "bare IPv6, scope zone",
+			Req: &http.Request{
+				URL: mustURL("http://[::1%25lo]"),
+			},
+			ExpectedError: fmt.Errorf("Invalid host in redirect target: " +
+				"contains scope zone"),
+		},
 		{
 			Name: "valid HTTP redirect, explicit port",
 			Req: &http.Request{