cmd: add new CLI "totp"

The totp is a program to generate Time-based One-time Password from
secret key.

2 files changed, 68 insertions, 0 deletions

diff --git a/README.md b/README.md
index 7bb5bdf0..077186df 100644
--- a/README.md
+++ b/README.md
@@ -23,6 +23,8 @@ This library is released every month, usually at the first week of month.
 * [**smtpcli**](https://pkg.go.dev/github.com/shuLhan/share/cmd/smtpcli):
   Command line interface to SMTP client protocol.
 
+* [**totp**](https://pkg.go.dev/github.com/shuLhan/share/cmd/totp):
+  Program to generate Time-based One-time Password using secret key.
 
 ## Libraries
 
diff --git a/cmd/totp/main.go b/cmd/totp/main.go
new file mode 100644
index 00000000..f175827c
--- /dev/null
+++ b/cmd/totp/main.go
@@ -0,0 +1,66 @@
+//
+// Program totp generate Time-based One-time Password from secret key.
+//
+package main
+
+import (
+	"crypto/sha1"
+	"crypto/sha256"
+	"crypto/sha512"
+	"flag"
+	"fmt"
+	"hash"
+	"log"
+	"os"
+
+	"github.com/shuLhan/share/lib/totp"
+)
+
+func main() {
+	log.SetFlags(0)
+
+	flag.Usage = usage
+
+	paramDigits := flag.Int("digits", 6, "number of digits to generated")
+	paramHash := flag.String("hash", "sha1", "hash names, valid values is sha1, sha256, sha512")
+	paramTimestep := flag.Int("timestep", 30, "time step in seconds")
+	paramHelp := flag.Bool("help", false, "show command usage")
+	flag.Parse()
+
+	if *paramHelp {
+		flag.Usage()
+	}
+	if len(os.Args) == 1 {
+		flag.Usage()
+	}
+
+	var hashFn func() hash.Hash
+	switch *paramHash {
+	case "sha256":
+		hashFn = sha256.New
+	case "sha512":
+		hashFn = sha512.New
+	default:
+		hashFn = sha1.New
+	}
+
+	totproto := totp.New(hashFn, *paramDigits, *paramTimestep)
+	secret := []byte(os.Args[1])
+	p0, err := totproto.Generate(secret)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Printf("%s\n", p0)
+}
+
+func usage() {
+	log.Printf(`%s is command line interface to generate time-based one-time password.
+Usage:
+	%s [OPTIONS] <SECRET_KEY>
+
+Available OPTIONS:
+`, os.Args[0], os.Args[0])
+	flag.PrintDefaults()
+	os.Exit(2)
+}