forked from sigstore/cosign
/
sget.go
122 lines (107 loc) · 3.51 KB
/
sget.go
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//
// Copyright 2021 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 sget
import (
"context"
"io"
"github.com/google/go-containerregistry/pkg/authn"
"github.com/google/go-containerregistry/pkg/name"
"github.com/google/go-containerregistry/pkg/v1/remote"
"github.com/pkg/errors"
"github.com/sigstore/cosign/cmd/cosign/cli/fulcio"
"github.com/sigstore/cosign/cmd/cosign/cli/options"
"github.com/sigstore/cosign/cmd/cosign/cli/verify"
"github.com/sigstore/cosign/pkg/cosign"
ociremote "github.com/sigstore/cosign/pkg/oci/remote"
sigs "github.com/sigstore/cosign/pkg/signature"
)
func New(image, key string, out io.Writer) *SecureGet {
return &SecureGet{
ImageRef: image,
KeyRef: key,
Out: out,
}
}
type SecureGet struct {
ImageRef string
KeyRef string
Out io.Writer
}
func (sg *SecureGet) Do(ctx context.Context) error {
ref, err := name.ParseReference(sg.ImageRef)
if err != nil {
return err
}
opts := []remote.Option{
remote.WithAuthFromKeychain(authn.DefaultKeychain),
remote.WithContext(ctx),
}
co := &cosign.CheckOpts{
ClaimVerifier: cosign.SimpleClaimVerifier,
RegistryClientOpts: []ociremote.Option{ociremote.WithRemoteOptions(opts...)},
}
if _, ok := ref.(name.Tag); ok {
if sg.KeyRef == "" && !options.EnableExperimental() {
return errors.New("public key must be specified when fetching by tag, you must fetch by digest or supply a public key")
}
}
// Overwrite "ref" with a digest to avoid a race where we verify the tag,
// and then access the file through the tag. This has a race where we
// might download content that isn't what we verified.
ref, err = ociremote.ResolveDigest(ref, co.RegistryClientOpts...)
if err != nil {
return err
}
if sg.KeyRef != "" {
pub, err := sigs.LoadPublicKey(ctx, sg.KeyRef)
if err != nil {
return err
}
co.SigVerifier = pub
}
if co.SigVerifier != nil || options.EnableExperimental() {
// NB: There are only 2 kinds of verification right now:
// 1. You gave us the public key explicitly to verify against so co.SigVerifier is non-nil or,
// 2. We're going to find an x509 certificate on the signature and verify against Fulcio root trust
// TODO(nsmith5): Refactor this verification logic to pass back _how_ verification
// was performed so we don't need to use this fragile logic here.
fulcioVerified := (co.SigVerifier == nil)
co.RootCerts = fulcio.GetRoots()
sp, bundleVerified, err := cosign.VerifyImageSignatures(ctx, ref, co)
if err != nil {
return err
}
verify.PrintVerificationHeader(sg.ImageRef, co, bundleVerified, fulcioVerified)
verify.PrintVerification(sg.ImageRef, sp, "text")
}
// TODO(mattmoor): Depending on what this is, use the higher-level stuff.
img, err := remote.Image(ref, opts...)
if err != nil {
return err
}
layers, err := img.Layers()
if err != nil {
return err
}
if len(layers) != 1 {
return errors.New("invalid artifact")
}
rc, err := layers[0].Compressed()
if err != nil {
return err
}
_, err = io.Copy(sg.Out, rc)
return err
}