server: Move all the top level files into cmd folder. (#2490)

This change brings a change which was done for the 'mc'
package to allow for clean repo and have a cleaner
github drop in experience.

cmd/access-key.go

@@ -0,0 +1,86 @@
+/*
+ * Minio Cloud Storage, (C) 2015, 2016 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 cmd
+
+import (
+	"crypto/rand"
+	"encoding/base64"
+	"regexp"
+)
+
+// credential container for access and secret keys.
+type credential struct {
+	AccessKeyID     string `json:"accessKey"`
+	SecretAccessKey string `json:"secretKey"`
+}
+
+const (
+	minioAccessID = 20
+	minioSecretID = 40
+)
+
+// isValidSecretKey - validate secret key.
+var isValidSecretKey = regexp.MustCompile(`^.{8,40}$`)
+
+// isValidAccessKey - validate access key.
+var isValidAccessKey = regexp.MustCompile(`^[a-zA-Z0-9\\-\\.\\_\\~]{5,20}$`)
+
+// mustGenAccessKeys - must generate access credentials.
+func mustGenAccessKeys() (creds credential) {
+	creds, err := genAccessKeys()
+	fatalIf(err, "Unable to generate access keys.")
+	return creds
+}
+
+// genAccessKeys - generate access credentials.
+func genAccessKeys() (credential, error) {
+	accessKeyID, err := genAccessKeyID()
+	if err != nil {
+		return credential{}, err
+	}
+	secretAccessKey, err := genSecretAccessKey()
+	if err != nil {
+		return credential{}, err
+	}
+	creds := credential{
+		AccessKeyID:     string(accessKeyID),
+		SecretAccessKey: string(secretAccessKey),
+	}
+	return creds, nil
+}
+
+// genAccessKeyID - generate random alpha numeric value using only uppercase characters
+// takes input as size in integer
+func genAccessKeyID() ([]byte, error) {
+	alpha := make([]byte, minioAccessID)
+	if _, err := rand.Read(alpha); err != nil {
+		return nil, err
+	}
+	for i := 0; i < minioAccessID; i++ {
+		alpha[i] = alphaNumericTable[alpha[i]%byte(len(alphaNumericTable))]
+	}
+	return alpha, nil
+}
+
+// genSecretAccessKey - generate random base64 numeric value from a random seed.
+func genSecretAccessKey() ([]byte, error) {
+	rb := make([]byte, minioSecretID)
+	if _, err := rand.Read(rb); err != nil {
+		return nil, err
+	}
+	return []byte(base64.StdEncoding.EncodeToString(rb))[:minioSecretID], nil
+}