providers: add "akamai" provider

The "akamai" provider adds support for retrieving an ignition
configuration from Akamai Connected Cloud's (a.k.a. Linode) [Metadata
Service][1].

See flatcar/Flatcar#1404

[1]: https://www.linode.com/docs/products/compute/compute-instances/guides/metadata/

docs/supported-platforms.md

@@ -6,6 +6,7 @@ nav_order: 8
 
 Ignition is currently only supported for the following platforms:
 
+* [Akamai Connected Cloud] (`akamai`) - Ignition will read its configuration from the instance userdata. Cloud SSH keys and network configuration are handled separately.
 * [Alibaba Cloud] (`aliyun`) - Ignition will read its configuration from the instance userdata. Cloud SSH keys are handled separately.
 * [Apple Hypervisor] (`applehv`) - Ignition will read its configuration using an HTTP GET over a vsock connection with its host on port 1024.
 * [Amazon Web Services] (`aws`) - Ignition will read its configuration from the instance userdata. Cloud SSH keys are handled separately.
@@ -36,6 +37,7 @@ Ignition is under active development, so this list may grow over time.
 
 For most cloud providers, cloud SSH keys and custom network configuration are handled by [Afterburn].
 
+[Akamai Connected Cloud]: https://www.linode.com
 [Alibaba Cloud]: https://www.alibabacloud.com/product/ecs
 [Apple Hypervisor]: https://developer.apple.com/documentation/hypervisor
 [Amazon Web Services]: https://aws.amazon.com/ec2/

internal/providers/akamai/akamai.go

@@ -0,0 +1,79 @@
+// Copyright 2024 CoreOS, Inc.
+//
+// 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 akamai provides platform support for Akamai Connected Cloud
+// (previously known as Linode).
+package akamai
+
+import (
+	"encoding/base64"
+	"fmt"
+	"net/http"
+	"net/url"
+
+	"github.com/coreos/ignition/v2/config/v3_5_experimental/types"
+	"github.com/coreos/ignition/v2/internal/platform"
+	"github.com/coreos/ignition/v2/internal/providers/util"
+	"github.com/coreos/ignition/v2/internal/resource"
+
+	"github.com/coreos/vcontext/report"
+)
+
+func init() {
+	platform.Register(platform.Provider{
+		Name:  "akamai",
+		Fetch: fetchConfig,
+		Init:  initFetcher,
+	})
+}
+
+var (
+	tokenURL    = url.URL{Scheme: "http", Host: "169.254.169.254", Path: "/v1/token"}
+	userdataURL = url.URL{Scheme: "http", Host: "169.254.169.254", Path: "/v1/user-data"}
+)
+
+func fetchConfig(f *resource.Fetcher) (types.Config, report.Report, error) {
+	encoded, err := f.FetchToBuffer(userdataURL, resource.FetchOptions{})
+	if err != nil {
+		return types.Config{}, report.Report{}, err
+	}
+
+	// The Linode Metadata Service requires userdata to be base64-encoded
+	// when it is uploaded.
+	data := make([]byte, base64.StdEncoding.DecodedLen(len(encoded)))
+	if _, err := base64.StdEncoding.Decode(data, encoded); err != nil {
+		return types.Config{}, report.Report{}, fmt.Errorf("decode base64: %w", err)
+	}
+
+	return util.ParseConfig(f.Logger, data)
+}
+
+func initFetcher(f *resource.Fetcher) error {
+	token, err := f.FetchToBuffer(tokenURL, resource.FetchOptions{
+		HTTPVerb: http.MethodPut,
+		Headers: http.Header{
+			"Metadata-Token-Expiry-Seconds": []string{"3600"},
+		},
+	})
+
+	// NOTE: ErrNotFound could mean the instance is running in a region
+	// where the Metadata Service has not been deployed.
+	if err != nil {
+		return fmt.Errorf("generate metadata api token: %w", err)
+	}
+
+	f.AkamaiMetadataToken = string(token)
+
+	return nil
+}

internal/resource/url.go

@@ -98,6 +98,10 @@ type Fetcher struct {
 	// It is used when fetching resources from GCS.
 	GCSSession *storage.Client
 
+	// AkamaiMetadataToken holds the token returned by the Metadata Service
+	// and is required for subsequent requests.
+	AkamaiMetadataToken string
+
 	// Whether to only attempt fetches which can be performed offline. This
 	// currently only includes the "data" scheme. Other schemes will result in
 	// ErrNeedNet. In the future, we can improve on this by dropping this