Add trusted-root create helper command (#3876)

* Fixes #3700: add trusted-root create helper command

To help cosign users move from providing disparate verification material
to a single file that contains the needed verification material.

This makes it easier for users to rotate key material and specify what
time period different keys were valid.

Signed-off-by: Zach Steindler <steiza@github.com>

* Linter fixes and docgen

Signed-off-by: Zach Steindler <steiza@github.com>

* Fix Windows unit test

Signed-off-by: Zach Steindler <steiza@github.com>

* Output via stdout instead of stderr

Signed-off-by: Zach Steindler <steiza@github.com>

* Add ctlogs to `cosign trusted-root create`

With `--ignore-sct` to support if you are using keys instead of Fulcio.

Signed-off-by: Zach Steindler <steiza@github.com>

* Replace `--rekor-url` with `--ignore-tlog`

Similar to `--ignore-sct`

Signed-off-by: Zach Steindler <steiza@github.com>

* Just use paths to files on disk

Instead of clients querying remote servers

Signed-off-by: Zach Steindler <steiza@github.com>

* Add the ability to supply multiple verification material

Also add ability to specify validity start time for keys

Signed-off-by: Zach Steindler <steiza@github.com>

* Don't panic if there's unexpected content in PEM file

Update tests, also fix documentation for flags that were removed.

Co-authored-by: Dmitry S <dsavints@gmail.com>
Signed-off-by: Zach Steindler <steiza@github.com>

* remove trailing newline

Signed-off-by: Zach Steindler <steiza@github.com>

* Simplify imports

Signed-off-by: Zach Steindler <steiza@github.com>

---------

Signed-off-by: Zach Steindler <steiza@github.com>
Co-authored-by: Dmitry S <dsavints@gmail.com>

cmd/cosign/cli/commands.go

@@ -120,6 +120,7 @@ func New() *cobra.Command {
 	cmd.AddCommand(VerifyBlob())
 	cmd.AddCommand(VerifyBlobAttestation())
 	cmd.AddCommand(Triangulate())
+	cmd.AddCommand(TrustedRoot())
 	cmd.AddCommand(Env())
 	cmd.AddCommand(version.WithFont("starwars"))
 

cmd/cosign/cli/options/trustedroot.go

@@ -0,0 +1,62 @@
+//
+// Copyright 2024 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 options
+
+import (
+	"github.com/spf13/cobra"
+)
+
+type TrustedRootCreateOptions struct {
+	CertChain        []string
+	CtfeKeyPath      []string
+	CtfeStartTime    []string
+	Out              string
+	RekorKeyPath     []string
+	RekorStartTime   []string
+	TSACertChainPath []string
+}
+
+var _ Interface = (*TrustedRootCreateOptions)(nil)
+
+func (o *TrustedRootCreateOptions) AddFlags(cmd *cobra.Command) {
+	cmd.Flags().StringArrayVar(&o.CertChain, "certificate-chain", nil,
+		"path to a list of CA certificates in PEM format which will be needed "+
+			"when building the certificate chain for the signing certificate. "+
+			"Must start with the parent intermediate CA certificate of the "+
+			"signing certificate and end with the root certificate.")
+	_ = cmd.Flags().SetAnnotation("certificate-chain", cobra.BashCompFilenameExt, []string{"cert"})
+
+	cmd.Flags().StringArrayVar(&o.CtfeKeyPath, "ctfe-key", nil,
+		"path to a PEM-encoded public key used by certificate authority for "+
+			"certificate transparency log.")
+
+	cmd.Flags().StringArrayVar(&o.CtfeStartTime, "ctfe-start-time", nil,
+		"RFC 3339 string describing validity start time for key use by "+
+			"certificate transparency log.")
+
+	cmd.Flags().StringVar(&o.Out, "out", "", "path to output trusted root")
+
+	cmd.Flags().StringArrayVar(&o.RekorKeyPath, "rekor-key", nil,
+		"path to a PEM-encoded public key used by transparency log like Rekor.")
+
+	cmd.Flags().StringArrayVar(&o.RekorStartTime, "rekor-start-time", nil,
+		"RFC 3339 string describing validity start time for key use by "+
+			"transparency log like Rekor.")
+
+	cmd.Flags().StringArrayVar(&o.TSACertChainPath, "timestamp-certificate-chain", nil,
+		"path to PEM-encoded certificate chain file for the RFC3161 timestamp authority. Must contain the root CA certificate. "+
+			"Optionally may contain intermediate CA certificates")
+}

cmd/cosign/cli/trustedroot.go

@@ -0,0 +1,66 @@
+//
+// Copyright 2024 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 cli
+
+import (
+	"context"
+
+	"github.com/spf13/cobra"
+
+	"github.com/sigstore/cosign/v2/cmd/cosign/cli/options"
+	"github.com/sigstore/cosign/v2/cmd/cosign/cli/trustedroot"
+)
+
+func TrustedRoot() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "trusted-root",
+		Short: "Interact with a Sigstore protobuf trusted root",
+		Long:  "Tools for interacting with a Sigstore protobuf trusted root",
+	}
+
+	cmd.AddCommand(trustedRootCreate())
+
+	return cmd
+}
+
+func trustedRootCreate() *cobra.Command {
+	o := &options.TrustedRootCreateOptions{}
+
+	cmd := &cobra.Command{
+		Use:   "create",
+		Short: "Create a Sigstore protobuf trusted root",
+		Long:  "Create a Sigstore protobuf trusted root by supplying verification material",
+		RunE: func(cmd *cobra.Command, _ []string) error {
+			trCreateCmd := &trustedroot.CreateCmd{
+				CertChain:        o.CertChain,
+				CtfeKeyPath:      o.CtfeKeyPath,
+				CtfeStartTime:    o.CtfeStartTime,
+				Out:              o.Out,
+				RekorKeyPath:     o.RekorKeyPath,
+				RekorStartTime:   o.RekorStartTime,
+				TSACertChainPath: o.TSACertChainPath,
+			}
+
+			ctx, cancel := context.WithTimeout(cmd.Context(), ro.Timeout)
+			defer cancel()
+
+			return trCreateCmd.Exec(ctx)
+		},
+	}
+
+	o.AddFlags(cmd)
+	return cmd
+}

cmd/cosign/cli/trustedroot/trustedroot.go

@@ -0,0 +1,205 @@
+//
+// Copyright 2024 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 trustedroot
+
+import (
+	"context"
+	"crypto"
+	"crypto/x509"
+	"encoding/hex"
+	"encoding/pem"
+	"fmt"
+	"os"
+	"time"
+
+	"github.com/sigstore/cosign/v2/pkg/cosign"
+	"github.com/sigstore/sigstore-go/pkg/root"
+	"github.com/sigstore/sigstore/pkg/cryptoutils"
+)
+
+type CreateCmd struct {
+	CertChain        []string
+	CtfeKeyPath      []string
+	CtfeStartTime    []string
+	Out              string
+	RekorKeyPath     []string
+	RekorStartTime   []string
+	TSACertChainPath []string
+}
+
+func (c *CreateCmd) Exec(_ context.Context) error {
+	var fulcioCertAuthorities []root.CertificateAuthority
+	ctLogs := make(map[string]*root.TransparencyLog)
+	var timestampAuthorities []root.CertificateAuthority
+	rekorTransparencyLogs := make(map[string]*root.TransparencyLog)
+
+	for i := 0; i < len(c.CertChain); i++ {
+		fulcioAuthority, err := parsePEMFile(c.CertChain[i])
+		if err != nil {
+			return err
+		}
+		fulcioCertAuthorities = append(fulcioCertAuthorities, *fulcioAuthority)
+	}
+
+	for i := 0; i < len(c.CtfeKeyPath); i++ {
+		ctLogPubKey, id, idBytes, err := getPubKey(c.CtfeKeyPath[i])
+		if err != nil {
+			return err
+		}
+
+		startTime := time.Unix(0, 0)
+
+		if i < len(c.CtfeStartTime) {
+			startTime, err = time.Parse(time.RFC3339, c.CtfeStartTime[i])
+			if err != nil {
+				return err
+			}
+		}
+
+		ctLogs[id] = &root.TransparencyLog{
+			HashFunc:            crypto.SHA256,
+			ID:                  idBytes,
+			ValidityPeriodStart: startTime,
+			PublicKey:           *ctLogPubKey,
+			SignatureHashFunc:   crypto.SHA256,
+		}
+	}
+
+	for i := 0; i < len(c.RekorKeyPath); i++ {
+		tlogPubKey, id, idBytes, err := getPubKey(c.RekorKeyPath[i])
+		if err != nil {
+			return err
+		}
+
+		startTime := time.Unix(0, 0)
+
+		if i < len(c.RekorStartTime) {
+			startTime, err = time.Parse(time.RFC3339, c.RekorStartTime[i])
+			if err != nil {
+				return err
+			}
+		}
+
+		rekorTransparencyLogs[id] = &root.TransparencyLog{
+			HashFunc:            crypto.SHA256,
+			ID:                  idBytes,
+			ValidityPeriodStart: startTime,
+			PublicKey:           *tlogPubKey,
+			SignatureHashFunc:   crypto.SHA256,
+		}
+	}
+
+	for i := 0; i < len(c.TSACertChainPath); i++ {
+		timestampAuthority, err := parsePEMFile(c.TSACertChainPath[i])
+		if err != nil {
+			return err
+		}
+		timestampAuthorities = append(timestampAuthorities, *timestampAuthority)
+	}
+
+	newTrustedRoot, err := root.NewTrustedRoot(root.TrustedRootMediaType01,
+		fulcioCertAuthorities, ctLogs, timestampAuthorities,
+		rekorTransparencyLogs,
+	)
+	if err != nil {
+		return err
+	}
+
+	var trBytes []byte
+
+	trBytes, err = newTrustedRoot.MarshalJSON()
+	if err != nil {
+		return err
+	}
+
+	if c.Out != "" {
+		err = os.WriteFile(c.Out, trBytes, 0600)
+		if err != nil {
+			return err
+		}
+	} else {
+		fmt.Println(string(trBytes))
+	}
+
+	return nil
+}
+
+func parsePEMFile(path string) (*root.CertificateAuthority, error) {
+	certs, err := parseCerts(path)
+	if err != nil {
+		return nil, err
+	}
+
+	var ca root.CertificateAuthority
+	ca.Root = certs[len(certs)-1]
+	ca.ValidityPeriodStart = certs[len(certs)-1].NotBefore
+	if len(certs) > 1 {
+		ca.Intermediates = certs[:len(certs)-1]
+	}
+
+	return &ca, nil
+}
+
+func parseCerts(path string) ([]*x509.Certificate, error) {
+	var certs []*x509.Certificate
+
+	contents, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+
+	for block, contents := pem.Decode(contents); block != nil; block, contents = pem.Decode(contents) {
+		cert, err := x509.ParseCertificate(block.Bytes)
+		if err != nil {
+			return nil, err
+		}
+		certs = append(certs, cert)
+
+		if len(contents) == 0 {
+			break
+		}
+	}
+
+	if len(certs) == 0 {
+		return nil, fmt.Errorf("no certificates in file %s", path)
+	}
+
+	return certs, nil
+}
+
+func getPubKey(path string) (*crypto.PublicKey, string, []byte, error) {
+	pemBytes, err := os.ReadFile(path)
+	if err != nil {
+		return nil, "", []byte{}, err
+	}
+
+	pubKey, err := cryptoutils.UnmarshalPEMToPublicKey(pemBytes)
+	if err != nil {
+		return nil, "", []byte{}, err
+	}
+
+	keyID, err := cosign.GetTransparencyLogID(pubKey)
+	if err != nil {
+		return nil, "", []byte{}, err
+	}
+
+	idBytes, err := hex.DecodeString(keyID)
+	if err != nil {
+		return nil, "", []byte{}, err
+	}
+
+	return &pubKey, keyID, idBytes, nil
+}