1 files changed, 59 insertions, 0 deletions
diff --git a/pkg/authn/github/keychain.go b/pkg/authn/github/keychain.go
new file mode 100644
index 0000000..97ad34e
--- /dev/null
+++ b/pkg/authn/github/keychain.go
@@ -0,0 +1,59 @@
+// Copyright 2022 Google LLC All Rights Reserved.
+//
+// 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 github provides a keychain for the GitHub Container Registry.
+package github
+
+import (
+	"net/url"
+	"os"
+
+	"github.com/google/go-containerregistry/pkg/authn"
+)
+
+const ghcrHostname = "ghcr.io"
+
+// Keychain exports an instance of the GitHub Keychain.
+//
+// This keychain matches on requests for ghcr.io and provides the value of the
+// environment variable $GITHUB_TOKEN, if it's set.
+var Keychain authn.Keychain = githubKeychain{}
+
+type githubKeychain struct{}
+
+func (githubKeychain) Resolve(r authn.Resource) (authn.Authenticator, error) {
+	serverURL, err := url.Parse("https://" + r.String())
+	if err != nil {
+		return authn.Anonymous, nil
+	}
+	if serverURL.Hostname() == ghcrHostname {
+		username := os.Getenv("GITHUB_ACTOR")
+		if username == "" {
+			username = "unset"
+		}
+		if tok := os.Getenv("GITHUB_TOKEN"); tok != "" {
+			return githubAuthenticator{username, tok}, nil
+		}
+	}
+	return authn.Anonymous, nil
+}
+
+type githubAuthenticator struct{ username, password string }
+
+func (g githubAuthenticator) Authorization() (*authn.AuthConfig, error) {
+	return &authn.AuthConfig{
+		Username: g.username,
+		Password: g.password,
+	}, nil
+}