fix(mutate): also set timestamps only present in some formats (#1550)

BronzeDeer · web-flow · commit 824efc7772b0 · 2023-02-01T10:39:32.000-08:00
Currently, layerTime only mutates the modification timestamp which is
present in all tar formats. When working with layers GNU or PAX header
formats, access and change timestamps are also generated/recorded. This
breaks functionality like reproducible builds which rely on having
control over all variable fields (esp. timestamps)  in the layers

This commit adds a special case to the layerTime(Layer, Time) function
which will also set the additional timestamps if the header is of GNU or
PAX format

Signed-off-by: Joel Pepper &lt;pepper@bronze-deer.de&gt;
diff --git a/pkg/v1/mutate/mutate.go b/pkg/v1/mutate/mutate.go
@@ -465,6 +465,13 @@ func layerTime(layer v1.Layer, t time.Time) (v1.Layer, error) {
 		}
 
 		header.ModTime = t
+
+		//PAX and GNU Format support additional timestamps in the header
+		if header.Format == tar.FormatPAX || header.Format == tar.FormatGNU {
+			header.AccessTime = t
+			header.ChangeTime = t
+		}
+
 		if err := tarWriter.WriteHeader(header); err != nil {
 			return nil, fmt.Errorf("writing tar header: %w", err)
 		}

Original file line number	Diff line number	Diff line change
`@@ -465,6 +465,13 @@ func layerTime(layer v1.Layer, t time.Time) (v1.Layer, error) {`
`465`	`465`	`}`
`466`	`466`
`467`	`467`	`header.ModTime = t`
	`468`	`+`
	`469`	`+ //PAX and GNU Format support additional timestamps in the header`
	`470`	`+ if header.Format == tar.FormatPAX \|\| header.Format == tar.FormatGNU {`
	`471`	`+ header.AccessTime = t`
	`472`	`+ header.ChangeTime = t`
	`473`	`+ }`
	`474`	`+`
`468`	`475`	`if err := tarWriter.WriteHeader(header); err != nil {`
`469`	`476`	`return nil, fmt.Errorf("writing tar header: %w", err)`
`470`	`477`	`}`