kubernetes/vendor/golang.org/x/oauth2/internal/oauth2.go

// ParseKey converts the binary contents of a private key file
// to an *rsa.PrivateKey. It detects whether the private key is in a
// PEM container or not. If so, it extracts the private key
// from PEM container before conversion. It only supports PEM
// containers with no passphrase.
func ParseKey(key []byte) (*rsa.PrivateKey, error) { … }