Use securejoin.SecureJoin when forming userns paths

go.mod

@@ -1,6 +1,6 @@
 module github.com/containers/skopeo
 
-go 1.19
+go 1.21
 
 require (
 	github.com/containers/common v0.57.5
@@ -14,7 +14,7 @@ require (
 	github.com/sirupsen/logrus v1.9.3
 	github.com/spf13/cobra v1.8.0
 	github.com/spf13/pflag v1.0.5
-	github.com/stretchr/testify v1.8.4
+	github.com/stretchr/testify v1.9.0
 	github.com/syndtr/gocapability v0.0.0-20200815063812-42c35b437635
 	golang.org/x/exp v0.0.0-20231226003508-02704c960a9b
 	golang.org/x/term v0.17.0
@@ -35,7 +35,7 @@ require (
 	github.com/containers/libtrust v0.0.0-20230121012942-c1716e8a8d01 // indirect
 	github.com/coreos/go-oidc/v3 v3.7.0 // indirect
 	github.com/cyberphone/json-canonicalization v0.0.0-20231011164504-785e29786b46 // indirect
-	github.com/cyphar/filepath-securejoin v0.2.4 // indirect
+	github.com/cyphar/filepath-securejoin v0.3.4 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/distribution/reference v0.5.0 // indirect
 	github.com/docker/docker v24.0.7+incompatible // indirect
@@ -121,7 +121,7 @@ require (
 	golang.org/x/net v0.19.0 // indirect
 	golang.org/x/oauth2 v0.14.0 // indirect
 	golang.org/x/sync v0.5.0 // indirect
-	golang.org/x/sys v0.17.0 // indirect
+	golang.org/x/sys v0.21.0 // indirect
 	golang.org/x/text v0.14.0 // indirect
 	golang.org/x/tools v0.16.0 // indirect
 	google.golang.org/appengine v1.6.8 // indirect