fixup! providers: add "akamai" provider

internal/providers/akamai/akamai.go

@@ -17,7 +17,9 @@
 package akamai
 
 import (
+	"bytes"
 	"encoding/base64"
+	"errors"
 	"fmt"
 	"net/http"
 	"net/url"
@@ -37,31 +39,44 @@ func init() {
 	})
 }
 
+// HTTP headers.
+const (
+	// tokenTTLHeader is the name of the HTTP request header that must be
+	// set when making requests to [tokenURL] or [tokenURL6].
+	tokenTTLHeader = "Metadata-Token-Expiry-Seconds"
+
+	// tokenHeader is the name of the HTTP request header that callers must
+	// set when making requests to [userdataURL] or [userdataURL6].
+	tokenHeader = "Metadata-Token"
+)
+
 var (
+	// IPv4 URLs.
 	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"}
+
+	// IPv6 URLs (for reference).
+	tokenURL6    = url.URL{Scheme: "http", Host: "[fd00:a9fe:a9fe::1]", Path: "/v1/token"}
+	userdataURL6 = url.URL{Scheme: "http", Host: "[fd00:a9fe:a9fe::1]", Path: "/v1/user-data"}
 )
 
 func fetchConfig(f *resource.Fetcher) (types.Config, report.Report, error) {
 	if f.Offline {
 		return types.Config{}, report.Report{}, resource.ErrNeedNet
 	}
 
-	token, err := f.FetchToBuffer(tokenURL, resource.FetchOptions{
-		HTTPVerb: http.MethodPut,
-		Headers: http.Header{
-			"Metadata-Token-Expiry-Seconds": []string{"3600"},
-		},
-	})
+	token, err := getToken(f)
 	if err != nil {
-		// NOTE: The instance could be running in a region where the
-		// Metadata Service has not yet been deployed.
-		return types.Config{}, report.Report{}, fmt.Errorf("generate metadata api token: %w", err)
+		return types.Config{}, report.Report{}, fmt.Errorf("get token: %w", err)
 	}
 
+	// NOTE: If we do not explicitly set the "Accept" header, it will be
+	// set by FetchToBuffer to a value that the Linode Metadata Service
+	// does not accept.
 	encoded, err := f.FetchToBuffer(userdataURL, resource.FetchOptions{
 		Headers: http.Header{
-			"Metadata-Token": []string{string(token)},
+			"Accept":    []string{"text/plain"},
+			tokenHeader: []string{string(token)},
 		},
 	})
 	if err != nil {
@@ -77,3 +92,31 @@ func fetchConfig(f *resource.Fetcher) (types.Config, report.Report, error) {
 
 	return util.ParseConfig(f.Logger, data)
 }
+
+// getToken retrieves an authorization token to use for subsequent requests to
+// Linode's Metadata Service.
+// The returned token must be provided in the [tokenHeader] request header.
+func getToken(f *resource.Fetcher) (token string, err error) {
+	// NOTE: This is using "text/plain" for content negotiation, just to
+	// skip the need to decode a JSON response.
+	// In the future, the accepted content type should probably become
+	// "application/vnd.coreos.ignition+json", but that will require
+	// support from Linode's Metadata Service API.
+	p, err := f.FetchToBuffer(tokenURL, resource.FetchOptions{
+		HTTPVerb: http.MethodPut,
+		Headers: http.Header{
+			"Accept":       []string{"text/plain"},
+			tokenTTLHeader: []string{"3600"},
+		},
+	})
+	if err != nil {
+		return "", fmt.Errorf("fetch to buffer: %w", err)
+	}
+
+	p = bytes.TrimSpace(p)
+	if len(p) == 0 {
+		return "", errors.New("receieved an empty token")
+	}
+
+	return string(p), nil
+}