pgaskin/otpprint.go

## otpprint.go
// Command otpprint prints TOTP codes.
package main

import (
	"crypto/hmac"
	"crypto/sha1"
	"encoding/base32"
	"encoding/binary"
	"fmt"
	"hash"
	"math"
	"os"
	"strconv"
	"strings"
	"time"
)

func main() {
	if n := len(os.Args); n < 2 || n > 4 {
		fmt.Printf("usage: %s secret [text|html] [now|YYYY-MM-DD|unix]\n", os.Args[0])
		os.Exit(2)
	}

	secret, err := base32.StdEncoding.DecodeString(strings.ToUpper(strings.ReplaceAll(os.Args[1], " ", "")))
	if err != nil {
		fmt.Fprintf(os.Stderr, "fatal: invalid base32 secret: %v\n", err)
		os.Exit(1)
	}

	var html bool
	if len(os.Args) > 2 {
		switch m := os.Args[2]; m {
		case "h", "html":
			html = true
		case "t", "text":
			html = false
		default:
			fmt.Fprintf(os.Stderr, "fatal: invalid mode %q\n", m)
			os.Exit(1)
		}
	}

	var dt time.Time
	if len(os.Args) > 3 && os.Args[3] != "now" {
		if v, err := strconv.ParseInt(os.Args[3], 10, 64); err != nil {
			if v, err := time.ParseInLocation("2006-01-02", os.Args[3], time.Local); err != nil {
				fmt.Fprintf(os.Stderr, "fatal: invalid start date %q\n", os.Args[3])
				os.Exit(1)
			} else {
				dt = v
			}
		} else {
			dt = time.Unix(v, 0)
		}
	} else {
		dt = time.Now()
	}

	yy, mm, dd := dt.Date()

	if html {
		fmt.Println(`<!DOCTYPE html>`)
		fmt.Println(`<html lang="en">`)
		fmt.Println(`<head>`)
		fmt.Println(`<meta charset="utf-8">`)
		fmt.Println(`<title>TOTP</title>`)
		fmt.Println(`<style>` + strings.TrimSpace(strings.NewReplacer("\t", "", "\n", "").Replace(`
			* {
				box-sizing: border-box;
			}
			main {
				width: 8.5in;
				height: 11in;
				overflow: hidden;
				color: #000;
			}
			@media screen {
				html {
					background: #444;
					padding: .1in;
				}
				main {
					margin: 0 auto;
					box-shadow: 0 0 6px 0 #000;
					background: #fff;
				}
			}
			@page {
				margin: 0;
				size: letter;
			}
			main {
				font-family: Roboto;
				font-size: 6pt;
				padding: .1in;
				line-height: 1;
				display: flex;
				align-items: center;
				justify-content: center;
			}
			table {
				border-collapse: collapse;
				flex: 0 0 auto;
				border: 1px solid #000;
			}
			th, td {
				padding: .9pt;
				white-space: nowrap;
			}
			th {
				font-weight: bold;
			}
			tr.rh > * {
				background: #ddd;
			}
			tr.rg > * {
				border-bottom: 1px solid #000;
			}
		`)) + `</style>`)
		fmt.Println(`<body>`)
		fmt.Println(`<main>`)
		fmt.Println(`<table>`)
	}
	for i := -1; i < 96; i++ {
		var (
			rh = i == -1
			rg = (i+1)%6 == 0
		)
		if html {
			fmt.Print(`<tr`)
			if rh || rg {
				fmt.Print(` class="`)
				if rh {
					fmt.Print("rh")
				}
				if rh && rg {
					fmt.Print(" ")
				}
				if rg {
					fmt.Print("rg")
				}
				fmt.Print(`"`)
			}
			fmt.Print(`>`)
		} else {
			if rh {
				fmt.Print("\033[1m")
			}
			if rg {
				fmt.Print("\033[4m")
			}
		}
		for j := -1; j < 26; j++ {
			var ld, lm int
			if i != -1 {
				lm = i * 10
			}
			if j != -1 {
				ld = j
			}
			lt := time.Date(yy, mm, dd+ld, 6, lm, 0, 0, time.Local)
			var ct string
			switch {
			case i == -1 && j == -1:
				ct = lt.Format("Jan")
			case i == -1:
				ct = lt.Format("Mon _2")
			case j == -1:
				ct = lt.Format("15:04")
			default:
				ct = hotp(totp(lt, 0), secret, 0, nil)
			}
			if html {
				if i == -1 || j == -1 {
					fmt.Printf(`<th>%s</th>`, ct)
				} else {
					fmt.Printf(`<td>%s</td>`, ct)
				}
			} else {
				if j == -1 {
					fmt.Printf("% -5s", ct)
				} else {
					fmt.Printf(" % -6s", ct)
				}
			}
		}
		if html {
			fmt.Println(`</tr>`)
		} else {
			fmt.Println("\033[0m")
		}
	}
	if html {
		fmt.Println(`</table>`)
		fmt.Println(`</main>`)
	}
}

func totp(t time.Time, s time.Duration) uint64 {
	if t.IsZero() {
		t = time.Now()
	}
	if s == 0 {
		s = time.Second * 30
	}
	return uint64(math.Floor(float64(t.Unix()) / s.Seconds()))
}

func hotp(c uint64, k []byte, n int, h func() hash.Hash) string {
	if n == 0 {
		n = 6
	}
	if h == nil {
		h = sha1.New
	}
	if n <= 0 || n > 8 {
		panic("otp: must be 0 < n <= 8")
	}
	if len(k) == 0 {
		panic("otp: key must not be empty")
	}
	hsh := hmac.New(h, k)
	binary.Write(hsh, binary.BigEndian, c)
	dst := hsh.Sum(nil)
	off := dst[len(dst)-1] & 0xf
	val := int64(((int(dst[off]))&0x7f)<<24 |
		((int(dst[off+1] & 0xff)) << 16) |
		((int(dst[off+2] & 0xff)) << 8) |
		((int(dst[off+3]) & 0xff) << 0))
	return fmt.Sprintf("%0*d", n, val%int64(math.Pow10(n)))
}
	// Command otpprint prints TOTP codes.
	package main

	import (
	"crypto/hmac"
	"crypto/sha1"
	"encoding/base32"
	"encoding/binary"
	"fmt"
	"hash"
	"math"
	"os"
	"strconv"
	"strings"
	"time"
	)

	func main() {
	if n := len(os.Args); n < 2 \|\| n > 4 {
	fmt.Printf("usage: %s secret [text\|html] [now\|YYYY-MM-DD\|unix]\n", os.Args[0])
	os.Exit(2)
	}

	secret, err := base32.StdEncoding.DecodeString(strings.ToUpper(strings.ReplaceAll(os.Args[1], " ", "")))
	if err != nil {
	fmt.Fprintf(os.Stderr, "fatal: invalid base32 secret: %v\n", err)
	os.Exit(1)
	}

	var html bool
	if len(os.Args) > 2 {
	switch m := os.Args[2]; m {
	case "h", "html":
	html = true
	case "t", "text":
	html = false
	default:
	fmt.Fprintf(os.Stderr, "fatal: invalid mode %q\n", m)
	os.Exit(1)
	}
	}

	var dt time.Time
	if len(os.Args) > 3 && os.Args[3] != "now" {
	if v, err := strconv.ParseInt(os.Args[3], 10, 64); err != nil {
	if v, err := time.ParseInLocation("2006-01-02", os.Args[3], time.Local); err != nil {
	fmt.Fprintf(os.Stderr, "fatal: invalid start date %q\n", os.Args[3])
	os.Exit(1)
	} else {
	dt = v
	}
	} else {
	dt = time.Unix(v, 0)
	}
	} else {
	dt = time.Now()
	}

	yy, mm, dd := dt.Date()

	if html {
	fmt.Println(`<!DOCTYPE html>`)
	fmt.Println(`<html lang="en">`)
	fmt.Println(`<head>`)
	fmt.Println(`<meta charset="utf-8">`)
	fmt.Println(`<title>TOTP</title>`)
	fmt.Println(`<style>` + strings.TrimSpace(strings.NewReplacer("\t", "", "\n", "").Replace(`
	* {
	box-sizing: border-box;
	}
	main {
	width: 8.5in;
	height: 11in;
	overflow: hidden;
	color: #000;
	}
	@media screen {
	html {
	background: #444;
	padding: .1in;
	}
	main {
	margin: 0 auto;
	box-shadow: 0 0 6px 0 #000;
	background: #fff;
	}
	}
	@page {
	margin: 0;
	size: letter;
	}
	main {
	font-family: Roboto;
	font-size: 6pt;
	padding: .1in;
	line-height: 1;
	display: flex;
	align-items: center;
	justify-content: center;
	}
	table {
	border-collapse: collapse;
	flex: 0 0 auto;
	border: 1px solid #000;
	}
	th, td {
	padding: .9pt;
	white-space: nowrap;
	}
	th {
	font-weight: bold;
	}
	tr.rh > * {
	background: #ddd;
	}
	tr.rg > * {
	border-bottom: 1px solid #000;
	}
	`)) + `</style>`)
	fmt.Println(`<body>`)
	fmt.Println(`<main>`)
	fmt.Println(`<table>`)
	}
	for i := -1; i < 96; i++ {
	var (
	rh = i == -1
	rg = (i+1)%6 == 0
	)
	if html {
	fmt.Print(`<tr`)
	if rh \|\| rg {
	fmt.Print(` class="`)
	if rh {
	fmt.Print("rh")
	}
	if rh && rg {
	fmt.Print(" ")
	}
	if rg {
	fmt.Print("rg")
	}
	fmt.Print(`"`)
	}
	fmt.Print(`>`)
	} else {
	if rh {
	fmt.Print("\033[1m")
	}
	if rg {
	fmt.Print("\033[4m")
	}
	}
	for j := -1; j < 26; j++ {
	var ld, lm int
	if i != -1 {
	lm = i * 10
	}
	if j != -1 {
	ld = j
	}
	lt := time.Date(yy, mm, dd+ld, 6, lm, 0, 0, time.Local)
	var ct string
	switch {
	case i == -1 && j == -1:
	ct = lt.Format("Jan")
	case i == -1:
	ct = lt.Format("Mon _2")
	case j == -1:
	ct = lt.Format("15:04")
	default:
	ct = hotp(totp(lt, 0), secret, 0, nil)
	}
	if html {
	if i == -1 \|\| j == -1 {
	fmt.Printf(`<th>%s</th>`, ct)
	} else {
	fmt.Printf(`<td>%s</td>`, ct)
	}
	} else {
	if j == -1 {
	fmt.Printf("% -5s", ct)
	} else {
	fmt.Printf(" % -6s", ct)
	}
	}
	}
	if html {
	fmt.Println(`</tr>`)
	} else {
	fmt.Println("\033[0m")
	}
	}
	if html {
	fmt.Println(`</table>`)
	fmt.Println(`</main>`)
	}
	}

	func totp(t time.Time, s time.Duration) uint64 {
	if t.IsZero() {
	t = time.Now()
	}
	if s == 0 {
	s = time.Second * 30
	}
	return uint64(math.Floor(float64(t.Unix()) / s.Seconds()))
	}

	func hotp(c uint64, k []byte, n int, h func() hash.Hash) string {
	if n == 0 {
	n = 6
	}
	if h == nil {
	h = sha1.New
	}
	if n <= 0 \|\| n > 8 {
	panic("otp: must be 0 < n <= 8")
	}
	if len(k) == 0 {
	panic("otp: key must not be empty")
	}
	hsh := hmac.New(h, k)
	binary.Write(hsh, binary.BigEndian, c)
	dst := hsh.Sum(nil)
	off := dst[len(dst)-1] & 0xf
	val := int64(((int(dst[off]))&0x7f)<<24 \|
	((int(dst[off+1] & 0xff)) << 16) \|
	((int(dst[off+2] & 0xff)) << 8) \|
	((int(dst[off+3]) & 0xff) << 0))
	return fmt.Sprintf("%0*d", n, val%int64(math.Pow10(n)))
	}