// Auth handles validation of HMAC-SHA1 authentication
func (a *HMACAuthenticator) Auth(r *http.Request) (error, error) {
// Check for Authorization header
auth := r.Header.Get("Authorization")
if auth == "" {
// Check for X-Goat-Authorization header override
auth = r.Header.Get("X-Goat-Authorization")
}
// Fetch credentials from HTTP Basic auth
pubkey, credentials, err := basicCredentials(auth)
if err != nil {
return err, nil
}
// Split credentials into nonce and API signature
pair := strings.Split(credentials, "/")
if len(pair) < 2 {
return errors.New("no nonce value"), nil
}
nonce := pair[0]
signature := pair[1]
// Check if nonce previously used, add it if it is not, to prevent replay attacks
// note: bloom filter may report false positives, but better safe than sorry
if nonceFilter.TestAndAdd([]byte(nonce)) {
return errors.New("repeated API request"), nil
}
// Load API key by pubkey
key, err := new(data.APIKey).Load(pubkey, "pubkey")
if err != nil || key == (data.APIKey{}) {
return errors.New("no such public key"), err
}
// Check if key is expired, delete it if it is
if key.Expire <= time.Now().Unix() {
go func(key data.APIKey) {
if err := key.Delete(); err != nil {
log.Println(err.Error())
}
}(key)
return errors.New("expired API key"), nil
}
// Generate API signature
expected, err := apiSignature(key.UserID, nonce, r.Method, r.URL.Path, key.Secret)
if err != nil {
return nil, errors.New("failed to generate API signature")
}
// Verify that HMAC signature is correct
if !hmac.Equal([]byte(signature), []byte(expected)) {
return errors.New("invalid API signature"), nil
}
// Update API key expiration time
key.Expire = time.Now().Add(7 * 24 * time.Hour).Unix()
go func(key data.APIKey) {
if err := key.Save(); err != nil {
log.Println(err.Error())
}
}(key)
// Load user by user ID
user, err := new(data.UserRecord).Load(key.UserID, "id")
if err != nil || user == (data.UserRecord{}) {
return errors.New("no such user"), err
}
// Store user for session
a.session = user
return nil, nil
}
