move the certPool loader function into pkg/certs (#10239)

pkg/certs/ca-certs.go

@@ -0,0 +1,57 @@
+/*
+ * MinIO Cloud Storage, (C) 2020 MinIO, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package certs
+
+import (
+	"crypto/x509"
+	"io/ioutil"
+	"os"
+	"path"
+)
+
+// GetRootCAs - returns all the root CAs into certPool
+// at the input certsCADir
+func GetRootCAs(certsCAsDir string) (*x509.CertPool, error) {
+	rootCAs, _ := x509.SystemCertPool()
+	if rootCAs == nil {
+		// In some systems (like Windows) system cert pool is
+		// not supported or no certificates are present on the
+		// system - so we create a new cert pool.
+		rootCAs = x509.NewCertPool()
+	}
+
+	fis, err := ioutil.ReadDir(certsCAsDir)
+	if err != nil {
+		if os.IsNotExist(err) || os.IsPermission(err) {
+			// Return success if CA's directory is missing or permission denied.
+			err = nil
+		}
+		return rootCAs, err
+	}
+
+	// Load all custom CA files.
+	for _, fi := range fis {
+		caCert, err := ioutil.ReadFile(path.Join(certsCAsDir, fi.Name()))
+		if err != nil {
+			// ignore files which are not readable.
+			continue
+		}
+		rootCAs.AppendCertsFromPEM(caCert)
+	}
+
+	return rootCAs, nil
+}