adding initial draft gitpod provider

pkg/providers/gitpod/doc.go

@@ -0,0 +1,18 @@
+//
+// 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 gitpod defines an implementation of the providers.Interface
+// that reads identity tokens from the gitpod API within a workspace.
+package gitpod

pkg/providers/gitpod/gitpod.go

@@ -0,0 +1,81 @@
+//
+// 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 gitpod
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"os"
+	"time"
+
+	"github.com/sigstore/cosign/v2/pkg/cosign/env"
+	"github.com/sigstore/cosign/v2/pkg/providers"
+)
+
+func init() {
+	providers.Register("filesystem", &gitpod{})
+}
+
+type gitpod struct{}
+
+var _ providers.Interface = (*gitpod)(nil)
+
+// Enabled implements providers.Interface
+func (ga *gitpod) Enabled(_ context.Context) bool {
+	if env.Getenv(env.VariableGitHubRequestToken) == "" {
+		return false
+	}
+	if env.Getenv(env.VariableGitHubRequestURL) == "" {
+		return false
+	}
+	return true
+}
+
+// Provide implements providers.Interface
+func (ga *gitpod) Provide(ctx context.Context, audience string) (string, error) {
+	url := env.Getenv(env.VariableGitHubRequestURL) + "&audience=" + audience
+
+	req, err := http.NewRequest("GET", url, nil)
+	if err != nil {
+		return "", err
+	}
+
+	// Retry up to 3 times.
+	for i := 0; ; i++ {
+		req.Header.Add("Authorization", "bearer "+env.Getenv(env.VariableGitHubRequestToken))
+		resp, err := http.DefaultClient.Do(req)
+		if err != nil {
+			if i == 2 {
+				return "", err
+			}
+			fmt.Fprintf(os.Stderr, "error fetching GitHub OIDC token (will retry): %v\n", err)
+			time.Sleep(time.Second)
+			continue
+		}
+		defer resp.Body.Close()
+
+		var payload struct {
+			Value string `json:"value"`
+		}
+		decoder := json.NewDecoder(resp.Body)
+		if err := decoder.Decode(&payload); err != nil {
+			return "", err
+		}
+		return payload.Value, nil
+	}
+}