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add sha256:... as alternative way to specify a blob #4016

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add sha256:... as alternative way to specify a blob #4016

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55 changes: 35 additions & 20 deletions cmd/cosign/cli/verify/verify_blob_attestation.go
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Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,8 @@ import (
"io"
"os"
"path/filepath"
"strings"
"regexp"

v1 "github.com/google/go-containerregistry/pkg/v1"
"github.com/sigstore/cosign/v2/cmd/cosign/cli/options"
Expand Down Expand Up @@ -76,6 +78,9 @@ type VerifyBlobAttestationCommand struct {
UseSignedTimestamps bool
}

// Add validation helper
var sha256RegExp = regexp.MustCompile("^[a-f0-9]{64}$")

// Exec runs the verification command
func (c *VerifyBlobAttestationCommand) Exec(ctx context.Context, artifactPath string) (err error) {
if options.NOf(c.SignaturePath, c.BundlePath) == 0 {
Expand Down Expand Up @@ -127,29 +132,39 @@ func (c *VerifyBlobAttestationCommand) Exec(ctx context.Context, artifactPath st
}
var h v1.Hash
if c.CheckClaims {
// Get the actual digest of the blob
var payload internal.HashReader
f, err := os.Open(filepath.Clean(artifactPath))
if err != nil {
return err
}
defer f.Close()
fileInfo, err := f.Stat()
if err != nil {
return err
}
err = payloadsize.CheckSize(uint64(fileInfo.Size()))
if err != nil {
return err
}
var hexDigest string
if strings.HasPrefix(artifactPath, "sha256:") {
// log that we are using a sha256 hash
fmt.Fprintf(os.Stderr, "Using sha256 hash %s\n", artifactPath)
hexDigest = strings.TrimPrefix(artifactPath, "sha256:")
if !sha256RegExp.MatchString(hexDigest) {
return fmt.Errorf("invalid sha256 hash format: must be 64 hex characters")
}
} else {
// Get the actual digest of the blob
var payload internal.HashReader
f, err := os.Open(filepath.Clean(artifactPath))
if err != nil {
return err
}
defer f.Close()
fileInfo, err := f.Stat()
if err != nil {
return err
}
err = payloadsize.CheckSize(uint64(fileInfo.Size()))
if err != nil {
return err
}

payload = internal.NewHashReader(f, sha256.New())
if _, err := io.ReadAll(&payload); err != nil {
return err
payload = internal.NewHashReader(f, sha256.New())
if _, err := io.ReadAll(&payload); err != nil {
return err
}
hexDigest = hex.EncodeToString(payload.Sum(nil))
}
digest := payload.Sum(nil)
h = v1.Hash{
Hex: hex.EncodeToString(digest),
Hex: hexDigest,
Algorithm: "sha256",
}
co.ClaimVerifier = cosign.IntotoSubjectClaimVerifier
Expand Down