adds tsa cert chain check for env var or tuf targets. (sigstore#3600)

* adds tsa cert chain check for env var or tuf targets. Signed-off-by: ianhundere <[email protected]> * adds new flag, --use-signed-timestamps, and adjusts verify_*.go tsa logic. Signed-off-by: ianhundere <[email protected]> --------- Signed-off-by: ianhundere <[email protected]>
dmitris · Jun 19, 2024 · 2b538f8 · 2b538f8
1 parent 9e3811b
commit 2b538f8
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Showing 14 changed files with 344 additions and 93 deletions.
diff --git a/cmd/cosign/cli/options/verify.go b/cmd/cosign/cli/options/verify.go
@@ -30,6 +30,7 @@ type CommonVerifyOptions struct {
 	// it for other verify options.
 	ExperimentalOCI11     bool
 	PrivateInfrastructure bool
+	UseSignedTimestamps   bool
 }
 
 func (o *CommonVerifyOptions) AddFlags(cmd *cobra.Command) {
@@ -40,6 +41,9 @@ func (o *CommonVerifyOptions) AddFlags(cmd *cobra.Command) {
 		"path to PEM-encoded certificate chain file for the RFC3161 timestamp authority. Must contain the root CA certificate. "+
 			"Optionally may contain intermediate CA certificates, and may contain the leaf TSA certificate if not present in the timestamp")
 
+	cmd.Flags().BoolVar(&o.UseSignedTimestamps, "use-signed-timestamps", false,
+		"use signed timestamps if available")
+
 	cmd.Flags().BoolVar(&o.IgnoreTlog, "insecure-ignore-tlog", false,
 		"ignore transparency log verification, to be used when an artifact signature has not been uploaded to the transparency log. Artifacts "+
 			"cannot be publicly verified when not included in a log")

diff --git a/cmd/cosign/cli/verify/verify.go b/cmd/cosign/cli/verify/verify.go
@@ -34,7 +34,6 @@ import (
 	"github.com/sigstore/cosign/v2/cmd/cosign/cli/rekor"
 	"github.com/sigstore/cosign/v2/cmd/cosign/cli/sign"
 	cosignError "github.com/sigstore/cosign/v2/cmd/cosign/errors"
-	"github.com/sigstore/cosign/v2/internal/pkg/cosign/tsa"
 	"github.com/sigstore/cosign/v2/internal/ui"
 	"github.com/sigstore/cosign/v2/pkg/blob"
 	"github.com/sigstore/cosign/v2/pkg/cosign"
@@ -77,11 +76,23 @@ type VerifyCommand struct {
 	NameOptions                  []name.Option
 	Offline                      bool
 	TSACertChainPath             string
+	UseSignedTimestamps          bool
 	IgnoreTlog                   bool
 	MaxWorkers                   int
 	ExperimentalOCI11            bool
 }
 
+func (c *VerifyCommand) loadTSACertificates(ctx context.Context) (*cosign.TSACertificates, error) {
+	if c.TSACertChainPath == "" && !c.UseSignedTimestamps {
+		return nil, fmt.Errorf("TSA certificate chain path not provided and use-signed-timestamps not set")
+	}
+	tsaCertificates, err := cosign.GetTSACerts(ctx, c.TSACertChainPath, cosign.GetTufTargets)
+	if err != nil {
+		return nil, fmt.Errorf("unable to load TSA certificates: %w", err)
+	}
+	return tsaCertificates, nil
+}
+
 // Exec runs the verification command
 func (c *VerifyCommand) Exec(ctx context.Context, images []string) (err error) {
 	if len(images) == 0 {
@@ -136,29 +147,14 @@ func (c *VerifyCommand) Exec(ctx context.Context, images []string) (err error) {
 		co.ClaimVerifier = cosign.SimpleClaimVerifier
 	}
 
-	if c.TSACertChainPath != "" {
-		_, err := os.Stat(c.TSACertChainPath)
-		if err != nil {
-			return fmt.Errorf("unable to open timestamp certificate chain file: %w", err)
-		}
-		// TODO: Add support for TUF certificates.
-		pemBytes, err := os.ReadFile(filepath.Clean(c.TSACertChainPath))
-		if err != nil {
-			return fmt.Errorf("error reading certification chain path file: %w", err)
-		}
-
-		leaves, intermediates, roots, err := tsa.SplitPEMCertificateChain(pemBytes)
+	if c.TSACertChainPath != "" || c.UseSignedTimestamps {
+		tsaCertificates, err := c.loadTSACertificates(ctx)
 		if err != nil {
-			return fmt.Errorf("error splitting certificates: %w", err)
-		}
-		if len(leaves) > 1 {
-			return fmt.Errorf("certificate chain must contain at most one TSA certificate")
-		}
-		if len(leaves) == 1 {
-			co.TSACertificate = leaves[0]
+			return fmt.Errorf("unable to load TSA certificates: %w", err)
 		}
-		co.TSAIntermediateCertificates = intermediates
-		co.TSARootCertificates = roots
+		co.TSACertificate = tsaCertificates.LeafCert
+		co.TSARootCertificates = tsaCertificates.RootCert
+		co.TSAIntermediateCertificates = tsaCertificates.IntermediateCerts
 	}
 
 	if !c.IgnoreTlog {

diff --git a/cmd/cosign/cli/verify/verify_attestation.go b/cmd/cosign/cli/verify/verify_attestation.go
@@ -28,7 +28,6 @@ import (
 	"github.com/sigstore/cosign/v2/cmd/cosign/cli/fulcio"
 	"github.com/sigstore/cosign/v2/cmd/cosign/cli/options"
 	"github.com/sigstore/cosign/v2/cmd/cosign/cli/rekor"
-	"github.com/sigstore/cosign/v2/internal/pkg/cosign/tsa"
 	"github.com/sigstore/cosign/v2/internal/ui"
 	"github.com/sigstore/cosign/v2/pkg/cosign"
 	"github.com/sigstore/cosign/v2/pkg/cosign/cue"
@@ -68,6 +67,18 @@ type VerifyAttestationCommand struct {
 	TSACertChainPath             string
 	IgnoreTlog                   bool
 	MaxWorkers                   int
+	UseSignedTimestamps          bool
+}
+
+func (c *VerifyAttestationCommand) loadTSACertificates(ctx context.Context) (*cosign.TSACertificates, error) {
+	if c.TSACertChainPath == "" && !c.UseSignedTimestamps {
+		return nil, fmt.Errorf("TSA certificate chain path not provided and use-signed-timestamps not set")
+	}
+	tsaCertificates, err := cosign.GetTSACerts(ctx, c.TSACertChainPath, cosign.GetTufTargets)
+	if err != nil {
+		return nil, fmt.Errorf("unable to load TSA certificates: %w", err)
+	}
+	return tsaCertificates, nil
 }
 
 // Exec runs the verification command
@@ -118,30 +129,16 @@ func (c *VerifyAttestationCommand) Exec(ctx context.Context, images []string) (e
 		}
 	}
 
-	if c.TSACertChainPath != "" {
-		_, err := os.Stat(c.TSACertChainPath)
-		if err != nil {
-			return fmt.Errorf("unable to open timestamp certificate chain file '%s: %w", c.TSACertChainPath, err)
-		}
-		// TODO: Add support for TUF certificates.
-		pemBytes, err := os.ReadFile(filepath.Clean(c.TSACertChainPath))
+	if c.TSACertChainPath != "" || c.UseSignedTimestamps {
+		tsaCertificates, err := c.loadTSACertificates(ctx)
 		if err != nil {
-			return fmt.Errorf("error reading certification chain path file: %w", err)
+			return fmt.Errorf("unable to load TSA certificates: %w", err)
 		}
-
-		leaves, intermediates, roots, err := tsa.SplitPEMCertificateChain(pemBytes)
-		if err != nil {
-			return fmt.Errorf("error splitting certificates: %w", err)
-		}
-		if len(leaves) > 1 {
-			return fmt.Errorf("certificate chain must contain at most one TSA certificate")
-		}
-		if len(leaves) == 1 {
-			co.TSACertificate = leaves[0]
-		}
-		co.TSAIntermediateCertificates = intermediates
-		co.TSARootCertificates = roots
+		co.TSACertificate = tsaCertificates.LeafCert
+		co.TSARootCertificates = tsaCertificates.RootCert
+		co.TSAIntermediateCertificates = tsaCertificates.IntermediateCerts
 	}
+
 	if !c.IgnoreTlog {
 		if c.RekorURL != "" {
 			rekorClient, err := rekor.NewClient(c.RekorURL)
@@ -157,6 +154,7 @@ func (c *VerifyAttestationCommand) Exec(ctx context.Context, images []string) (e
 			return fmt.Errorf("getting Rekor public keys: %w", err)
 		}
 	}
+
 	if keylessVerification(c.KeyRef, c.Sk) {
 		// This performs an online fetch of the Fulcio roots. This is needed
 		// for verifying keyless certificates (both online and offline).
@@ -169,6 +167,7 @@ func (c *VerifyAttestationCommand) Exec(ctx context.Context, images []string) (e
 			return fmt.Errorf("getting Fulcio intermediates: %w", err)
 		}
 	}
+
 	keyRef := c.KeyRef
 
 	// Keys are optional!

diff --git a/cmd/cosign/cli/verify/verify_blob.go b/cmd/cosign/cli/verify/verify_blob.go
@@ -31,7 +31,6 @@ import (
 	"github.com/sigstore/cosign/v2/cmd/cosign/cli/fulcio"
 	"github.com/sigstore/cosign/v2/cmd/cosign/cli/options"
 	"github.com/sigstore/cosign/v2/cmd/cosign/cli/rekor"
-	"github.com/sigstore/cosign/v2/internal/pkg/cosign/tsa"
 	"github.com/sigstore/cosign/v2/internal/ui"
 	"github.com/sigstore/cosign/v2/pkg/blob"
 	"github.com/sigstore/cosign/v2/pkg/cosign"
@@ -64,9 +63,21 @@ type VerifyBlobCmd struct {
 	IgnoreSCT                    bool
 	SCTRef                       string
 	Offline                      bool
+	UseSignedTimestamps          bool
 	IgnoreTlog                   bool
 }
 
+func (c *VerifyBlobCmd) loadTSACertificates(ctx context.Context) (*cosign.TSACertificates, error) {
+	if c.TSACertChainPath == "" && !c.UseSignedTimestamps {
+		return nil, fmt.Errorf("either TSA certificate chain path must be provided or use-signed-timestamps must be set")
+	}
+	tsaCertificates, err := cosign.GetTSACerts(ctx, c.TSACertChainPath, cosign.GetTufTargets)
+	if err != nil {
+		return nil, fmt.Errorf("unable to load TSA certificates: %w", err)
+	}
+	return tsaCertificates, nil
+}
+
 // nolint
 func (c *VerifyBlobCmd) Exec(ctx context.Context, blobRef string) error {
 	var cert *x509.Certificate
@@ -112,32 +123,17 @@ func (c *VerifyBlobCmd) Exec(ctx context.Context, blobRef string) error {
 		Offline:                      c.Offline,
 		IgnoreTlog:                   c.IgnoreTlog,
 	}
-	if c.RFC3161TimestampPath != "" && c.KeyOpts.TSACertChainPath == "" {
-		return fmt.Errorf("timestamp-certificate-chain is required to validate a RFC3161 timestamp")
+	if c.RFC3161TimestampPath != "" && !(c.TSACertChainPath != "" || c.UseSignedTimestamps) {
+		return fmt.Errorf("either TSA certificate chain path must be provided or use-signed-timestamps must be set when using RFC3161 timestamp path")
 	}
-	if c.KeyOpts.TSACertChainPath != "" {
-		_, err := os.Stat(c.KeyOpts.TSACertChainPath)
-		if err != nil {
-			return fmt.Errorf("unable to open timestamp certificate chain file '%s: %w", c.KeyOpts.TSACertChainPath, err)
-		}
-		// TODO: Add support for TUF certificates.
-		pemBytes, err := os.ReadFile(filepath.Clean(c.KeyOpts.TSACertChainPath))
+	if c.TSACertChainPath != "" || c.UseSignedTimestamps {
+		tsaCertificates, err := c.loadTSACertificates(ctx)
 		if err != nil {
-			return fmt.Errorf("error reading certification chain path file: %w", err)
-		}
-
-		leaves, intermediates, roots, err := tsa.SplitPEMCertificateChain(pemBytes)
-		if err != nil {
-			return fmt.Errorf("error splitting certificates: %w", err)
-		}
-		if len(leaves) > 1 {
-			return fmt.Errorf("certificate chain must contain at most one TSA certificate")
-		}
-		if len(leaves) == 1 {
-			co.TSACertificate = leaves[0]
+			return err
 		}
-		co.TSAIntermediateCertificates = intermediates
-		co.TSARootCertificates = roots
+		co.TSACertificate = tsaCertificates.LeafCert
+		co.TSARootCertificates = tsaCertificates.RootCert
+		co.TSAIntermediateCertificates = tsaCertificates.IntermediateCerts
 	}
 
 	if !c.IgnoreTlog {

diff --git a/cmd/cosign/cli/verify/verify_blob_attestation.go b/cmd/cosign/cli/verify/verify_blob_attestation.go
@@ -35,7 +35,6 @@ import (
 	"github.com/sigstore/cosign/v2/cmd/cosign/cli/rekor"
 	internal "github.com/sigstore/cosign/v2/internal/pkg/cosign"
 	payloadsize "github.com/sigstore/cosign/v2/internal/pkg/cosign/payload/size"
-	"github.com/sigstore/cosign/v2/internal/pkg/cosign/tsa"
 	"github.com/sigstore/cosign/v2/pkg/blob"
 	"github.com/sigstore/cosign/v2/pkg/cosign"
 	"github.com/sigstore/cosign/v2/pkg/cosign/bundle"
@@ -71,7 +70,8 @@ type VerifyBlobAttestationCommand struct {
 	PredicateType string
 	// TODO: Add policies
 
-	SignaturePath string // Path to the signature
+	SignaturePath       string // Path to the signature
+	UseSignedTimestamps bool
 }
 
 // Exec runs the verification command
@@ -140,32 +140,18 @@ func (c *VerifyBlobAttestationCommand) Exec(ctx context.Context, artifactPath st
 	}
 
 	// Set up TSA, Fulcio roots and tlog public keys and clients.
-	if c.RFC3161TimestampPath != "" && c.KeyOpts.TSACertChainPath == "" {
-		return fmt.Errorf("timestamp-cert-chain is required to validate a rfc3161 timestamp bundle")
+	if c.RFC3161TimestampPath != "" && !(c.TSACertChainPath != "" || c.UseSignedTimestamps) {
+		return fmt.Errorf("either TSA certificate chain path must be provided or use-signed-timestamps must be set when using RFC3161 timestamp path")
 	}
-	if c.KeyOpts.TSACertChainPath != "" {
-		_, err := os.Stat(c.TSACertChainPath)
-		if err != nil {
-			return fmt.Errorf("unable to open timestamp certificate chain file: %w", err)
-		}
-		// TODO: Add support for TUF certificates.
-		pemBytes, err := os.ReadFile(filepath.Clean(c.TSACertChainPath))
-		if err != nil {
-			return fmt.Errorf("error reading certification chain path file: %w", err)
-		}
 
-		leaves, intermediates, roots, err := tsa.SplitPEMCertificateChain(pemBytes)
+	if c.TSACertChainPath != "" || c.UseSignedTimestamps {
+		tsaCertificates, err := cosign.GetTSACerts(ctx, c.TSACertChainPath, cosign.GetTufTargets)
 		if err != nil {
-			return fmt.Errorf("error splitting certificates: %w", err)
-		}
-		if len(leaves) > 1 {
-			return fmt.Errorf("certificate chain must contain at most one TSA certificate")
-		}
-		if len(leaves) == 1 {
-			co.TSACertificate = leaves[0]
+			return fmt.Errorf("unable to load or get TSA certificates: %w", err)
 		}
-		co.TSAIntermediateCertificates = intermediates
-		co.TSARootCertificates = roots
+		co.TSACertificate = tsaCertificates.LeafCert
+		co.TSARootCertificates = tsaCertificates.RootCert
+		co.TSAIntermediateCertificates = tsaCertificates.IntermediateCerts
 	}
 
 	if !c.IgnoreTlog {

diff --git a/doc/cosign_dockerfile_verify.md b/doc/cosign_dockerfile_verify.md
diff --git a/doc/cosign_manifest_verify.md b/doc/cosign_manifest_verify.md
diff --git a/doc/cosign_verify-attestation.md b/doc/cosign_verify-attestation.md
diff --git a/doc/cosign_verify-blob-attestation.md b/doc/cosign_verify-blob-attestation.md
diff --git a/doc/cosign_verify-blob.md b/doc/cosign_verify-blob.md
diff --git a/doc/cosign_verify.md b/doc/cosign_verify.md
diff --git a/pkg/cosign/env/env.go b/pkg/cosign/env/env.go
@@ -58,6 +58,7 @@ const (
 	VariableSigstoreRootFile           Variable = "SIGSTORE_ROOT_FILE"
 	VariableSigstoreRekorPublicKey     Variable = "SIGSTORE_REKOR_PUBLIC_KEY"
 	VariableSigstoreIDToken            Variable = "SIGSTORE_ID_TOKEN" //nolint:gosec
+	VariableSigstoreTSACertificateFile Variable = "SIGSTORE_TSA_CERTIFICATE_FILE"
 
 	// Other external environment variables
 	VariableGitHubHost                Variable = "GITHUB_HOST"
@@ -138,7 +139,12 @@ var (
 			Sensitive:   false,
 			External:    true,
 		},
-
+		VariableSigstoreTSACertificateFile: {
+			Description: "path to the concatenated PEM-encoded TSA certificate file (leaf, intermediate(s), root) used by Sigstore",
+			Expects:     "path to the TSA certificate file",
+			Sensitive:   false,
+			External:    true,
+		},
 		VariableGitHubHost: {
 			Description: "is URL of the GitHub Enterprise instance",
 			Expects:     "string with the URL of GitHub Enterprise instance",