var signedLocatorRe = regexp.MustCompile(`^([[:xdigit:]]{32}).*\+A([[:xdigit:]]{40})@([[:xdigit:]]{8})`)
-// 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 {
+// 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 false
+ return PermissionError
}
blob_hash := matches[1]
sig_hex := matches[2]
exp_hex := matches[3]
- if exp_time, err := ParseHexTimestamp(exp_hex); err != nil || exp_time.Before(time.Now()) {
- // Signature is expired, or timestamp is unparseable
- return false
+ if exp_time, err := ParseHexTimestamp(exp_hex); err != nil {
+ return PermissionError
+ } else if exp_time.Before(time.Now()) {
+ return ExpiredError
}
- return sig_hex == MakePermSignature(blob_hash, api_token, exp_hex)
+ if sig_hex != MakePermSignature(blob_hash, api_token, exp_hex) {
+ return PermissionError
+ }
+ return nil
}
func ParseHexTimestamp(timestamp_hex string) (ts time.Time, err error) {