Add the ability to contruct TrustRoot from targets

pkg/root/trusted_root.go

@@ -51,6 +51,7 @@ type CertificateAuthority struct {
 	Leaf                *x509.Certificate
 	ValidityPeriodStart time.Time
 	ValidityPeriodEnd   time.Time
+	URI                 string
 }
 
 type TransparencyLog struct {
@@ -81,6 +82,15 @@ func (tr *TrustedRoot) CTLogs() map[string]*TransparencyLog {
 	return tr.ctLogs
 }
 
+func (tr *TrustedRoot) MarshalJSON() ([]byte, error) {
+	err := tr.constructProtoTrustRoot()
+	if err != nil {
+		return nil, fmt.Errorf("failed constructing protobuf TrustRoot representation: %w", err)
+	}
+
+	return protojson.Marshal(tr.trustedRoot)
+}
+
 func NewTrustedRootFromProtobuf(protobufTrustedRoot *prototrustroot.TrustedRoot) (trustedRoot *TrustedRoot, err error) {
 	if protobufTrustedRoot.GetMediaType() != TrustedRootMediaType01 {
 		return nil, fmt.Errorf("unsupported TrustedRoot media type: %s", protobufTrustedRoot.GetMediaType())
@@ -240,7 +250,9 @@ func ParseCertificateAuthority(certAuthority *prototrustroot.CertificateAuthorit
 		return nil, fmt.Errorf("CertificateAuthority cert chain is empty")
 	}
 
-	certificateAuthority = &CertificateAuthority{}
+	certificateAuthority = &CertificateAuthority{
+		URI: certAuthority.Uri,
+	}
 	for i, cert := range certChain.GetCertificates() {
 		parsedCert, err := x509.ParseCertificate(cert.RawBytes)
 		if err != nil {
@@ -302,6 +314,27 @@ func NewTrustedRootProtobuf(rootJSON []byte) (*prototrustroot.TrustedRoot, error
 	return pbTrustedRoot, nil
 }
 
+// NewTrustedRoot initializes a TrustedRoot object from a mediaType string, list of Fulcio
+// certificate authorities, list of timestamp authorities and maps of ctlogs and rekor
+// transparency log instances.
+func NewTrustedRoot(mediaType string,
+	certificateAuthorities []CertificateAuthority,
+	certificateTransparencyLogs map[string]*TransparencyLog,
+	timestampAuthorities []CertificateAuthority,
+	transparencyLogs map[string]*TransparencyLog) (*TrustedRoot, error) {
+	// document that we assume 1 cert chain per target and with certs already ordered from leaf to root
+	if mediaType != TrustedRootMediaType01 {
+		return nil, fmt.Errorf("unsupported TrustedRoot media type: %s", TrustedRootMediaType01)
+	}
+	tr := &TrustedRoot{
+		fulcioCertAuthorities:   certificateAuthorities,
+		ctLogs:                  certificateTransparencyLogs,
+		timestampingAuthorities: timestampAuthorities,
+		rekorLogs:               transparencyLogs,
+	}
+	return tr, nil
+}
+
 // FetchTrustedRoot fetches the Sigstore trusted root from TUF and returns it.
 func FetchTrustedRoot() (*TrustedRoot, error) {
 	return FetchTrustedRootWithOptions(tuf.DefaultOptions())

pkg/root/trusted_root_create.go

@@ -0,0 +1,221 @@
+// Copyright 2023 The Sigstore 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 root
+
+import (
+	"crypto"
+	"crypto/ecdsa"
+	"crypto/ed25519"
+	"crypto/elliptic"
+	"crypto/rsa"
+	"crypto/x509"
+	"fmt"
+	"sort"
+	"time"
+
+	protocommon "github.com/sigstore/protobuf-specs/gen/pb-go/common/v1"
+	prototrustroot "github.com/sigstore/protobuf-specs/gen/pb-go/trustroot/v1"
+	timestamppb "google.golang.org/protobuf/types/known/timestamppb"
+)
+
+func (tr *TrustedRoot) constructProtoTrustRoot() error {
+	tr.trustedRoot = &prototrustroot.TrustedRoot{}
+	tr.trustedRoot.MediaType = TrustedRootMediaType01
+
+	for logID, transparencyLog := range tr.rekorLogs {
+		tlProto, err := transparencyLogToProtobufTL(*transparencyLog)
+		if err != nil {
+			return fmt.Errorf("failed converting rekor log %s to protobuf: %w", logID, err)
+		}
+		tr.trustedRoot.Tlogs = append(tr.trustedRoot.Tlogs, tlProto)
+		// ensure stable sorting of the slice
+		sort.Slice(tr.trustedRoot.Tlogs, func(i, j int) bool {
+			iTime := time.Unix(0, 0)
+			jTime := time.Unix(0, 0)
+
+			if tr.trustedRoot.Tlogs[i].PublicKey.ValidFor.Start != nil {
+				iTime = tr.trustedRoot.Tlogs[i].PublicKey.ValidFor.Start.AsTime()
+			}
+			if tr.trustedRoot.Tlogs[j].PublicKey.ValidFor.Start != nil {
+				iTime = tr.trustedRoot.Tlogs[j].PublicKey.ValidFor.Start.AsTime()
+			}
+			return iTime.Before(jTime)
+		})
+	}
+
+	for logID, ctLog := range tr.ctLogs {
+		ctProto, err := transparencyLogToProtobufTL(*ctLog)
+		if err != nil {
+			return fmt.Errorf("failed converting ctlog %s to protobuf: %w", logID, err)
+		}
+		tr.trustedRoot.Ctlogs = append(tr.trustedRoot.Ctlogs, ctProto)
+		// ensure stable sorting of the slice
+		sort.Slice(tr.trustedRoot.Ctlogs, func(i, j int) bool {
+			iTime := time.Unix(0, 0)
+			jTime := time.Unix(0, 0)
+
+			if tr.trustedRoot.Ctlogs[i].PublicKey.ValidFor.Start != nil {
+				iTime = tr.trustedRoot.Ctlogs[i].PublicKey.ValidFor.Start.AsTime()
+			}
+			if tr.trustedRoot.Ctlogs[j].PublicKey.ValidFor.Start != nil {
+				iTime = tr.trustedRoot.Ctlogs[j].PublicKey.ValidFor.Start.AsTime()
+			}
+			return iTime.Before(jTime)
+		})
+	}
+
+	for _, ca := range tr.fulcioCertAuthorities {
+		caProto, err := certificateAuthorityToProtobufCA(ca)
+		if err != nil {
+			return fmt.Errorf("failed converting fulcio cert chain to protobuf: %w", err)
+		}
+		tr.trustedRoot.CertificateAuthorities = append(tr.trustedRoot.CertificateAuthorities, caProto)
+	}
+
+	for _, ca := range tr.timestampingAuthorities {
+		caProto, err := certificateAuthorityToProtobufCA(ca)
+		if err != nil {
+			return fmt.Errorf("failed converting TSA cert chain to protobuf: %w", err)
+		}
+		tr.trustedRoot.TimestampAuthorities = append(tr.trustedRoot.TimestampAuthorities, caProto)
+	}
+
+	return nil
+}
+
+func certificateAuthorityToProtobufCA(ca CertificateAuthority) (*prototrustroot.CertificateAuthority, error) {
+	org := ""
+	if len(ca.Root.Subject.Organization) > 0 {
+		org = ca.Root.Subject.Organization[0]
+	}
+	var allCerts []*protocommon.X509Certificate
+	if ca.Leaf != nil {
+		allCerts = append(allCerts, &protocommon.X509Certificate{RawBytes: ca.Leaf.Raw})
+	}
+	for _, intermed := range ca.Intermediates {
+		allCerts = append(allCerts, &protocommon.X509Certificate{RawBytes: intermed.Raw})
+	}
+	if ca.Root == nil {
+		return nil, fmt.Errorf("root certificate is nil")
+	}
+	allCerts = append(allCerts, &protocommon.X509Certificate{RawBytes: ca.Root.Raw})
+
+	caProto := prototrustroot.CertificateAuthority{
+		Uri: ca.URI,
+		Subject: &protocommon.DistinguishedName{
+			Organization: org,
+			CommonName:   ca.Root.Subject.CommonName,
+		},
+		ValidFor: &protocommon.TimeRange{
+			Start: timestamppb.New(ca.ValidityPeriodStart),
+		},
+		CertChain: &protocommon.X509CertificateChain{
+			Certificates: allCerts,
+		},
+	}
+
+	if !ca.ValidityPeriodEnd.IsZero() {
+		caProto.ValidFor.End = timestamppb.New(ca.ValidityPeriodEnd)
+	}
+
+	return &caProto, nil
+}
+
+func transparencyLogToProtobufTL(tl TransparencyLog) (*prototrustroot.TransparencyLogInstance, error) {
+	hashAlgo, err := hashAlgorithmToProtobufHashAlgorithm(tl.HashFunc)
+	if err != nil {
+		return nil, fmt.Errorf("failed converting hash algorithm to protobuf: %w", err)
+	}
+	publicKey, err := publicKeyToProtobufPublicKey(tl.PublicKey, tl.ValidityPeriodStart, tl.ValidityPeriodEnd)
+	if err != nil {
+		return nil, fmt.Errorf("failed converting public key to protobuf: %w", err)
+	}
+	trProto := prototrustroot.TransparencyLogInstance{
+		BaseUrl:       tl.BaseURL,
+		HashAlgorithm: hashAlgo,
+		PublicKey:     publicKey,
+		LogId: &protocommon.LogId{
+			KeyId: tl.ID,
+		},
+	}
+
+	return &trProto, nil
+}
+
+func hashAlgorithmToProtobufHashAlgorithm(hashAlgorithm crypto.Hash) (protocommon.HashAlgorithm, error) {
+	switch hashAlgorithm {
+	case crypto.SHA256:
+		return protocommon.HashAlgorithm_SHA2_256, nil
+	case crypto.SHA384:
+		return protocommon.HashAlgorithm_SHA2_384, nil
+	case crypto.SHA512:
+		return protocommon.HashAlgorithm_SHA2_512, nil
+	case crypto.SHA3_256:
+		return protocommon.HashAlgorithm_SHA3_256, nil
+	case crypto.SHA3_384:
+		return protocommon.HashAlgorithm_SHA3_384, nil
+	default:
+		return 0, fmt.Errorf("unsupported hash algorithm for Merkle tree: %v", hashAlgorithm)
+	}
+}
+
+func publicKeyToProtobufPublicKey(publicKey crypto.PublicKey, start time.Time, end time.Time) (*protocommon.PublicKey, error) {
+	pkd := protocommon.PublicKey{
+		ValidFor: &protocommon.TimeRange{
+			Start: timestamppb.New(start),
+		},
+	}
+
+	if !end.IsZero() {
+		pkd.ValidFor.End = timestamppb.New(end)
+	}
+
+	rawBytes, err := x509.MarshalPKIXPublicKey(publicKey)
+	if err != nil {
+		return nil, fmt.Errorf("failed marshalling public key: %w", err)
+	}
+	pkd.RawBytes = rawBytes
+
+	switch p := publicKey.(type) {
+	case *ecdsa.PublicKey:
+		switch p.Curve {
+		case elliptic.P256():
+			pkd.KeyDetails = protocommon.PublicKeyDetails_PKIX_ECDSA_P256_SHA_256
+		case elliptic.P384():
+			pkd.KeyDetails = protocommon.PublicKeyDetails_PKIX_ECDSA_P384_SHA_384
+		case elliptic.P521():
+			pkd.KeyDetails = protocommon.PublicKeyDetails_PKIX_ECDSA_P521_SHA_512
+		default:
+			return nil, fmt.Errorf("unsupported curve for ecdsa key: %T", p.Curve)
+		}
+	case *rsa.PublicKey:
+		switch p.Size() * 8 {
+		case 2048:
+			pkd.KeyDetails = protocommon.PublicKeyDetails_PKIX_RSA_PKCS1V15_2048_SHA256
+		case 3072:
+			pkd.KeyDetails = protocommon.PublicKeyDetails_PKIX_RSA_PKCS1V15_3072_SHA256
+		case 4096:
+			pkd.KeyDetails = protocommon.PublicKeyDetails_PKIX_RSA_PKCS1V15_4096_SHA256
+		default:
+			return nil, fmt.Errorf("unsupported public modulus for RSA key: %d", p.Size())
+		}
+	case *ed25519.PublicKey:
+		pkd.KeyDetails = protocommon.PublicKeyDetails_PKIX_ED25519
+	default:
+		return nil, fmt.Errorf("unknown public key type: %T", p)
+	}
+
+	return &pkd, nil
+}

pkg/root/trusted_root_test.go

@@ -21,8 +21,10 @@ import (
 	"crypto/elliptic"
 	"crypto/rand"
 	"crypto/rsa"
+	"encoding/json"
 	"encoding/pem"
 	"os"
+	"strings"
 	"testing"
 	"time"
 
@@ -165,3 +167,21 @@ func TestTrustedMaterialCollectionRSA(t *testing.T) {
 	assert.NoError(t, err)
 	assert.Equal(t, verifier, verifier2)
 }
+
+func TestFromJSONToJSON(t *testing.T) {
+	trustedrootJSON, err := os.ReadFile("../../examples/trusted-root-public-good.json")
+	assert.NoError(t, err)
+
+	trustedRoot, err := NewTrustedRootFromJSON(trustedrootJSON)
+	assert.NoError(t, err)
+
+	jsonBytes, err := json.Marshal(trustedRoot)
+	assert.NoError(t, err)
+
+	// Protobuf JSON serialization intentionally strips second fraction from time, if
+	// the fraction is 0. We do the same to the expected result:
+	// https://github.com/golang/protobuf/blob/b7697bb698b1c56643249ef6179c7cae1478881d/jsonpb/encode.go#L207
+	trJSONTrimmedTime := strings.ReplaceAll(string(trustedrootJSON), ".000Z\"", "Z\"")
+
+	assert.JSONEq(t, trJSONTrimmedTime, string(jsonBytes))
+}