auth.go

   1 package anidb
   2
   3 import (
   4         "crypto/aes"
   5         "crypto/cipher"
   6         "crypto/rand"
   7         "github.com/Kovensky/go-anidb/udp"
   8         "io"
   9         "runtime"
  10 )
  11
  12 // We still have the key and IV somewhere in memory...
  13 // but it's better than plaintext.
  14 type credentials struct {
  15         username []byte
  16         password []byte
  17         udpKey   []byte
  18 }
  19
  20 func (c *credentials) shred() {
  21         if c != nil {
  22                 io.ReadFull(rand.Reader, c.username)
  23                 io.ReadFull(rand.Reader, c.password)
  24                 io.ReadFull(rand.Reader, c.udpKey)
  25                 c.username = nil
  26                 c.password = nil
  27                 c.udpKey = nil
  28         }
  29 }
  30
  31 // Randomly generated on every execution
  32 var aesKey []byte
  33
  34 func init() {
  35         aesKey = make([]byte, aes.BlockSize)
  36         if _, err := io.ReadFull(rand.Reader, aesKey); err != nil {
  37                 panic(err)
  38         }
  39 }
  40
  41 func crypt(plaintext string) []byte {
  42         p := []byte(plaintext)
  43
  44         block, err := aes.NewCipher(aesKey)
  45         if err != nil {
  46                 panic(err)
  47         }
  48
  49         ciphertext := make([]byte, len(p)+aes.BlockSize)
  50         iv := ciphertext[:aes.BlockSize]
  51         if _, err := io.ReadFull(rand.Reader, iv); err != nil {
  52                 panic(err)
  53         }
  54
  55         stream := cipher.NewCTR(block, iv)
  56         stream.XORKeyStream(ciphertext[aes.BlockSize:], p)
  57
  58         return ciphertext
  59 }
  60
  61 func decrypt(ciphertext []byte) string {
  62         if len(ciphertext) <= aes.BlockSize {
  63                 return ""
  64         }
  65         p := make([]byte, len(ciphertext)-aes.BlockSize)
  66
  67         block, err := aes.NewCipher(aesKey)
  68         if err != nil {
  69                 panic(err)
  70         }
  71
  72         stream := cipher.NewCTR(block, ciphertext[:aes.BlockSize])
  73         stream.XORKeyStream(p, ciphertext[aes.BlockSize:])
  74
  75         return string(p)
  76 }
  77
  78 func newCredentials(username, password, udpKey string) *credentials {
  79         return &credentials{
  80                 username: crypt(username),
  81                 password: crypt(password),
  82                 udpKey:   crypt(udpKey),
  83         }
  84 }
  85
  86 func (udp *udpWrap) ReAuth() udpapi.APIReply {
  87         if Banned() {
  88                 return bannedReply
  89         }
  90
  91         udp.credLock.Lock()
  92         defer udp.credLock.Unlock()
  93
  94         if c := udp.credentials; c != nil {
  95                 logRequest(paramSet{cmd: "AUTH", params: paramMap{"user": decrypt(c.username)}})
  96                 r := udp.AniDBUDP.Auth(
  97                         decrypt(c.username),
  98                         decrypt(c.password),
  99                         decrypt(c.udpKey))
 100                 runtime.GC() // any better way to clean the plaintexts?
 101                 logReply(r)
 102
 103                 err := r.Error()
 104
 105                 if err != nil {
 106                         switch r.Code() {
 107                         // 555 -- banned
 108                         // 601 -- server down, treat the same as a ban
 109                         case 555, 601:
 110                                 setBanned()
 111                         case 500: // bad credentials
 112                                 udp.credentials.shred()
 113                                 udp.credentials = nil
 114                         case 503, 504: // client rejected
 115                                 panic(err)
 116                         }
 117                 }
 118                 udp.connected = err == nil
 119                 return r
 120         }
 121         return &noauthAPIReply{}
 122 }
 123
 124 // Saves the used credentials in the AniDB struct, to allow automatic
 125 // re-authentication when needed; they are (properly) encrypted with a key that's
 126 // uniquely generated every time the module is initialized.
 127 func (adb *AniDB) SetCredentials(username, password, udpKey string) {
 128         adb.udp.credLock.Lock()
 129         defer adb.udp.credLock.Unlock()
 130
 131         adb.udp.credentials.shred()
 132         adb.udp.credentials = newCredentials(username, password, udpKey)
 133 }
 134
 135 // Authenticates to anidb's UDP API and, on success, stores the credentials using
 136 // SetCredentials. If udpKey is not "", the communication with the server
 137 // will be encrypted, but in the VERY weak ECB mode.
 138 func (adb *AniDB) Auth(username, password, udpKey string) (err error) {
 139         defer runtime.GC() // any better way to clean the plaintexts?
 140
 141         adb.udp.sendLock.Lock()
 142         defer adb.udp.sendLock.Unlock()
 143
 144         if !Banned() {
 145                 adb.SetCredentials(username, password, udpKey)
 146         }
 147
 148         // ReAuth clears the credentials if they're bad
 149         return adb.udp.ReAuth().Error()
 150 }
 151
 152 // Logs the user out and removes the credentials from the AniDB struct.
 153 func (adb *AniDB) Logout() error {
 154         adb.udp.credLock.Lock()
 155         defer adb.udp.credLock.Unlock()
 156
 157         adb.udp.credentials.shred()
 158         adb.udp.credentials = nil
 159
 160         adb.udp.sendLock.Lock()
 161         defer adb.udp.sendLock.Unlock()
 162
 163         if adb.udp.connected {
 164                 adb.udp.connected = false
 165                 logRequest(paramSet{cmd: "LOGOUT"})
 166                 return adb.udp.Logout()
 167         }
 168         return nil
 169 }