cert: Add issuer certificate

This PR adds the issuer certificate with parsing and validation.

contributes to scionproto#2853

go/lib/scrypto/cert/v2/BUILD.bazel

@@ -5,6 +5,7 @@ go_library(
     srcs = [
         "as.go",
         "base.go",
+        "issuer.go",
     ],
     importpath = "github.com/scionproto/scion/go/lib/scrypto/cert/v2",
     visibility = ["//visibility:public"],
@@ -22,6 +23,8 @@ go_test(
         "as_test.go",
         "base_json_test.go",
         "base_test.go",
+        "issuer_json_test.go",
+        "issuer_test.go",
     ],
     embed = [":go_default_library"],
     deps = [

go/lib/scrypto/cert/v2/as_json_test.go

@@ -22,6 +22,7 @@ import (
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
+	"github.com/scionproto/scion/go/lib/addr"
 	"github.com/scionproto/scion/go/lib/scrypto"
 	"github.com/scionproto/scion/go/lib/scrypto/cert/v2"
 )
@@ -51,6 +52,16 @@ func TestASUnmarshalJSON(t *testing.T) {
 				}
 			},
 		},
+		"With optional distribution points": {
+			baseTest: baseTest{
+				Modify: func(g *genCert) {
+					(*g.OptDistPoints) = []addr.IA{ia210}
+				},
+			},
+			ModifyExpected: func(c *cert.AS) {
+				c.OptionalDistributionPoints = []addr.IA{ia210}
+			},
+		},
 		"Invalid CertificateType": {
 			baseTest: baseTest{
 				Modify: func(g *genCert) {

go/lib/scrypto/cert/v2/issuer.go

@@ -0,0 +1,136 @@
+// Copyright 2019 Anapaya Systems
+//
+// 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 cert
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+
+	"github.com/scionproto/scion/go/lib/common"
+	"github.com/scionproto/scion/go/lib/scrypto"
+)
+
+var (
+	// ErrIssuerTRCVersionNotSet indicates the issuer TRC version is not set.
+	ErrIssuerTRCVersionNotSet = errors.New("issuer TRC version not set")
+)
+
+// Issuer is the Issuer certificate.
+type Issuer struct {
+	Base
+	// Issuer holds the TRC Version. Since the issuer certificate is
+	// self-signed, the issuing AS in the TRC is the same as the subject of this
+	// certificate.
+	Issuer IssuerTRC `json:"Issuer"`
+	// CertificateType ensures the correct certificate type when marshalling.
+	CertificateType TypeIssuer `json:"CertificateType"`
+}
+
+// Validate checks that the certificate is in a valid format.
+func (c *Issuer) Validate() error {
+	if err := c.Base.Validate(); err != nil {
+		return err
+	}
+	if err := c.validateKeys(true); err != nil {
+		return err
+	}
+	return nil
+}
+
+// UnmarshalJSON checks that all fields are set.
+func (c *Issuer) UnmarshalJSON(b []byte) error {
+	var cAlias issuerAlias
+	dec := json.NewDecoder(bytes.NewReader(b))
+	dec.DisallowUnknownFields()
+	if err := dec.Decode(&cAlias); err != nil {
+		return err
+	}
+	if err := cAlias.checkAllSet(); err != nil {
+		return err
+	}
+	*c = Issuer{
+		Base:            cAlias.Base,
+		Issuer:          *cAlias.Issuer,
+		CertificateType: *cAlias.CertificateType,
+	}
+	return nil
+}
+
+type issuerAlias struct {
+	Base
+	Issuer          *IssuerTRC  `json:"Issuer"`
+	CertificateType *TypeIssuer `json:"CertificateType"`
+}
+
+func (c *issuerAlias) checkAllSet() error {
+	if err := c.Base.checkAllSet(); err != nil {
+		return err
+	}
+	switch {
+	case c.Issuer == nil:
+		return ErrIssuerNotSet
+	case c.CertificateType == nil:
+		return ErrCertificateTypeNotSet
+	}
+	return nil
+}
+
+// issuerTRCAlias is necessary to avoid an infinite recursion when unmarshalling.
+type issuerTRCAlias IssuerTRC
+
+// IssuerTRC identifies the TRC that authenticates the issuer certificate. The
+// issuer certificate is self-signed, thus, the issuing AS and TRC ISD are
+// implied by the subject.
+type IssuerTRC struct {
+	// TRCVersion is the version of the issuing TRC.
+	TRCVersion scrypto.Version `json:"TRCVersion"`
+}
+
+// UnmarshalJSON checks that all fields are set.
+func (i *IssuerTRC) UnmarshalJSON(b []byte) error {
+	dec := json.NewDecoder(bytes.NewReader(b))
+	dec.DisallowUnknownFields()
+	if err := dec.Decode((*issuerTRCAlias)(i)); err != nil {
+		return err
+	}
+	return i.checkAllSet()
+}
+
+func (i *IssuerTRC) checkAllSet() error {
+	if i.TRCVersion == 0 {
+		return ErrIssuerTRCVersionNotSet
+	}
+	return nil
+}
+
+const TypeIssuerJSON = "Issuer"
+
+// TypeIssuer indicates an AS certificate.
+type TypeIssuer struct{}
+
+// UnmarshalText checks that the certificate type matches.
+func (TypeIssuer) UnmarshalText(b []byte) error {
+	if TypeIssuerJSON != string(b) {
+		return common.NewBasicError(InvalidCertificateType, nil,
+			"expected", TypeIssuerJSON, "actual", string(b))
+	}
+	return nil
+}
+
+// MarshalText returns the AS certificate type.
+func (TypeIssuer) MarshalText() ([]byte, error) {
+	return []byte(TypeIssuerJSON), nil
+}