use plain pkg module

Signed-off-by: Jörn Friedrich Dreyer <jfd@butonic.de>

pkg/crypto/crypto.go

@@ -0,0 +1,28 @@
+// Package crypto implements utility functions for handling crypto related files.
+package crypto
+
+import (
+	"bytes"
+	"crypto/x509"
+	"errors"
+	"io"
+)
+
+// NewCertPoolFromPEM reads certificates from io.Reader and returns a x509.CertPool
+// containing those certificates.
+func NewCertPoolFromPEM(crts ...io.Reader) (*x509.CertPool, error) {
+	certPool := x509.NewCertPool()
+
+	var buf bytes.Buffer
+	for _, c := range crts {
+		if _, err := io.Copy(&buf, c); err != nil {
+			return nil, err
+		}
+		if !certPool.AppendCertsFromPEM(buf.Bytes()) {
+			return nil, errors.New("failed to append cert from PEM")
+		}
+		buf.Reset()
+	}
+
+	return certPool, nil
+}