"@" + timestamp_hex
}
-// VerifySignature returns true if the signature on the signed_locator
-// can be verified using the given api_token.
-func VerifySignature(signed_locator string, api_token string) bool {
- if re, err := regexp.Compile(`^([a-f0-9]{32}(\+[0-9]+)?).*\+A[[:xdigit:]]+@([[:xdigit:]]{8})`); err == nil {
- if matches := re.FindStringSubmatch(signed_locator); matches != nil {
- blob_locator := matches[1]
- timestamp_hex := matches[3]
- if expire_ts, err := ParseHexTimestamp(timestamp_hex); err == nil {
- // Fail signatures with expired timestamps.
- if expire_ts.Before(time.Now()) {
- return false
- }
- return signed_locator == SignLocator(blob_locator, api_token, expire_ts)
- }
- }
+var signedLocatorRe = regexp.MustCompile(`^([[:xdigit:]]{32}).*\+A([[:xdigit:]]{40})@([[:xdigit:]]{8})`)
+
+// VerifySignature returns nil if the signature on the signed_locator
+// can be verified using the given api_token. Otherwise it returns
+// either ExpiredError (if the timestamp has expired, which is
+// something the client could have figured out independently) or
+// PermissionError.
+func VerifySignature(signed_locator string, api_token string) error {
+ matches := signedLocatorRe.FindStringSubmatch(signed_locator)
+ if matches == nil {
+ // Could not find a permission signature at all
+ return PermissionError
+ }
+ blob_hash := matches[1]
+ sig_hex := matches[2]
+ exp_hex := matches[3]
+ if exp_time, err := ParseHexTimestamp(exp_hex); err != nil {
+ return PermissionError
+ } else if exp_time.Before(time.Now()) {
+ return ExpiredError
+ }
+ if sig_hex != MakePermSignature(blob_hash, api_token, exp_hex) {
+ return PermissionError
}
- return false
+ return nil
}
func ParseHexTimestamp(timestamp_hex string) (ts time.Time, err error) {