gauth/gauth.go
2014-02-26 20:12:10 -08:00

136 lines
3.0 KiB
Go

package main
import (
"bytes"
"code.google.com/p/gopass"
"crypto/aes"
"crypto/cipher"
"crypto/hmac"
"crypto/sha1"
"crypto/sha256"
"encoding/base32"
"encoding/csv"
"fmt"
"io/ioutil"
"log"
"math/big"
"os/user"
"path"
"strings"
"time"
)
func TimeStamp() (int64, int) {
time := time.Now().Unix()
return time / 30, int(time % 30)
}
func normalizeSecret(sec string) string {
noPadding := strings.ToUpper(strings.Replace(sec, " ", "", -1))
padLength := 8 - (len(noPadding) % 8)
if padLength < 8 {
return noPadding + strings.Repeat("=", padLength)
}
return noPadding
}
func AuthCode(sec string, ts int64) (string, error) {
key, err := base32.StdEncoding.DecodeString(sec)
if err != nil {
return "", err
}
enc := hmac.New(sha1.New, key)
msg := make([]byte, 8, 8)
msg[0] = (byte)(ts >> (7 * 8) & 0xff)
msg[1] = (byte)(ts >> (6 * 8) & 0xff)
msg[2] = (byte)(ts >> (5 * 8) & 0xff)
msg[3] = (byte)(ts >> (4 * 8) & 0xff)
msg[4] = (byte)(ts >> (3 * 8) & 0xff)
msg[5] = (byte)(ts >> (2 * 8) & 0xff)
msg[6] = (byte)(ts >> (1 * 8) & 0xff)
msg[7] = (byte)(ts >> (0 * 8) & 0xff)
if _, err := enc.Write(msg); err != nil {
return "", err
}
hash := enc.Sum(nil)
offset := hash[19] & 0x0f
trunc := hash[offset : offset+4]
trunc[0] &= 0x7F
res := new(big.Int).Mod(new(big.Int).SetBytes(trunc), big.NewInt(1000000))
return fmt.Sprintf("%06d", res), nil
}
func authCodeOrDie(sec string, ts int64) string {
str, e := AuthCode(sec, ts)
if e != nil {
log.Fatal(e)
}
return str
}
func main() {
user, e := user.Current()
if e != nil {
log.Fatal(e)
}
cfgPath := path.Join(user.HomeDir, ".config/gauth.csv")
cfgContent, e := ioutil.ReadFile(cfgPath)
if e != nil {
log.Fatal(e)
}
// Support for 'openssl enc -aes-128-cbc -md sha256 -pass pass:'
if bytes.Compare(cfgContent[:8], []byte{0x53, 0x61, 0x6c, 0x74, 0x65, 0x64, 0x5f, 0x5f}) == 0 {
passwd, e := gopass.GetPass("Encryption password: ")
if e != nil {
log.Fatal(e)
}
salt := cfgContent[8:16]
rest := cfgContent[16:]
salting := sha256.New()
salting.Write([]byte(passwd))
salting.Write(salt)
sum := salting.Sum(nil)
key := sum[:16]
iv := sum[16:]
block, e := aes.NewCipher(key)
if e != nil {
log.Fatal(e)
}
mode := cipher.NewCBCDecrypter(block, iv)
mode.CryptBlocks(rest, rest)
// Remove padding
i := len(rest)
for rest[i] < 16 {
i--
}
cfgContent = rest[:i]
}
cfgReader := csv.NewReader(bytes.NewReader(cfgContent))
// Unix-style tabular
cfgReader.Comma = ':'
cfg, e := cfgReader.ReadAll()
if e != nil {
log.Fatal(e)
}
currentTS, progress := TimeStamp()
prevTS := currentTS - 1
nextTS := currentTS + 1
fmt.Println(" prev curr next")
for _, record := range cfg {
name := record[0]
secret := normalizeSecret(record[1])
prevToken := authCodeOrDie(secret, prevTS)
currentToken := authCodeOrDie(secret, currentTS)
nextToken := authCodeOrDie(secret, nextTS)
fmt.Printf("%-10s %s %s %s\n", name, prevToken, currentToken, nextToken)
}
fmt.Printf("[%-29s]\n", strings.Repeat("=", progress))
}