akamai: fix base64 decoding

trailing \x00 character was making Ignition to fail parsing the config.
It is not always the case, that is why we did not catch it earlier: when
there is no padding in the base64 payload, everything was working.

https://pkg.go.dev/encoding/base64#Encoding.Decode

Signed-off-by: Mathieu Tortuyaux <mtortuyaux@microsoft.com>

docs/release-notes.md

@@ -14,6 +14,7 @@ nav_order: 9
 
 ### Bug fixes
 
+- Fixed Akamai Ignition base64 decoding
 
 ## Ignition 2.19.0 (2024-06-05)
 

internal/providers/akamai/akamai.go

@@ -86,11 +86,12 @@ func fetchConfig(f *resource.Fetcher) (types.Config, report.Report, error) {
 	// The Linode Metadata Service requires userdata to be base64-encoded
 	// when it is uploaded, so we will have to decode the response.
 	data := make([]byte, base64.StdEncoding.DecodedLen(len(encoded)))
-	if _, err := base64.StdEncoding.Decode(data, encoded); err != nil {
+	n, err := base64.StdEncoding.Decode(data, encoded)
+	if err != nil {
 		return types.Config{}, report.Report{}, fmt.Errorf("decode base64: %w", err)
 	}
 
-	return util.ParseConfig(f.Logger, data)
+	return util.ParseConfig(f.Logger, data[:n])
 }
 
 // defaultTokenTTL is the time-to-live (TTL; in seconds) for an authorization