/ go-winio Public
backuptar: SecurityDescriptorFromTarHeader() don't decode twice #233
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I noticed this when looking at #220
While writing, I wondered why we didn't just return the result of
base64.StdEncoding.DecodeString()directly, but it looks like that may return "garbage" output on failure; https://github.com/golang/go/blob/go1.17.7/src/encoding/base64/base64.go#L382-L387
Here's a short example showing that; https://go.dev/play/p/6kCw85ofiTx
The above shows;
While callers should never trust output if an error occurs, it's probably better to explicitly return
niljust to be sure no garbage is used.
This may be a theoretical situation, but the tar headers may contain
both the old and new headers, in which case we would be decoding
This patch rewrites the function to try the new headers first, and
return early if found, then fall back to trying the old headers.