mirror of
https://github.com/containers/skopeo.git
synced 2025-09-28 21:46:48 +00:00
23899acadd
Move the manifest computation (with v2s1 signature stripping) out of skopeo/signature into a separate package; it is necessary in the OpenShift client as well, unrelated to signatures. Other Docker-specific utilities, like getting a list of layer blobsums from a manifest, may be also moved here in the future.
66 lines
2.2 KiB
Go
66 lines
2.2 KiB
Go
package dockerutils
|
|
|
|
import (
|
|
"crypto/sha256"
|
|
"encoding/hex"
|
|
"encoding/json"
|
|
|
|
"github.com/docker/libtrust"
|
|
)
|
|
|
|
// FIXME: Should we just use docker/distribution and docker/docker implementations directly?
|
|
|
|
// A string representing a Docker manifest MIME type
|
|
type manifestMIMEType string
|
|
|
|
const (
|
|
dockerV2Schema1MIMEType manifestMIMEType = "application/vnd.docker.distribution.manifest.v1+json"
|
|
dockerV2Schema2MIMEType manifestMIMEType = "application/vnd.docker.distribution.manifest.v2+json"
|
|
)
|
|
|
|
// guessManifestMIMEType guesses MIME type of a manifest and returns it _if it is recognized_, or "" if unknown or unrecognized.
|
|
// FIXME? We should, in general, prefer out-of-band MIME type instead of blindly parsing the manifest,
|
|
// but we may not have such metadata available (e.g. when the manifest is a local file).
|
|
func guessManifestMIMEType(manifest []byte) manifestMIMEType {
|
|
// A subset of manifest fields; the rest is silently ignored by json.Unmarshal.
|
|
// Also docker/distribution/manifest.Versioned.
|
|
meta := struct {
|
|
MediaType string `json:"mediaType"`
|
|
SchemaVersion int `json:"schemaVersion"`
|
|
}{}
|
|
if err := json.Unmarshal(manifest, &meta); err != nil {
|
|
return ""
|
|
}
|
|
|
|
switch meta.MediaType {
|
|
case string(dockerV2Schema2MIMEType): // A recognized type.
|
|
return manifestMIMEType(meta.MediaType)
|
|
}
|
|
switch meta.SchemaVersion {
|
|
case 1:
|
|
return dockerV2Schema1MIMEType
|
|
case 2: // Really should not happen, meta.MediaType should have been set. But given the data, this is our best guess.
|
|
return dockerV2Schema2MIMEType
|
|
}
|
|
return ""
|
|
}
|
|
|
|
// ManifestDigest returns the a digest of a docker manifest, with any necessary implied transformations like stripping v1s1 signatures.
|
|
func ManifestDigest(manifest []byte) (string, error) {
|
|
if guessManifestMIMEType(manifest) == dockerV2Schema1MIMEType {
|
|
sig, err := libtrust.ParsePrettySignature(manifest, "signatures")
|
|
if err != nil {
|
|
return "", err
|
|
}
|
|
manifest, err = sig.Payload()
|
|
if err != nil {
|
|
// Coverage: This should never happen, libtrust's Payload() can fail only if joseBase64UrlDecode() fails, on a string
|
|
// that libtrust itself has josebase64UrlEncode()d
|
|
return "", err
|
|
}
|
|
}
|
|
|
|
hash := sha256.Sum256(manifest)
|
|
return "sha256:" + hex.EncodeToString(hash[:]), nil
|
|
}
|