X-Git-Url: https://git.arvados.org/arvados.git/blobdiff_plain/d81ea65da05119d5c6480d373b5d42bbee8ae1ad..30012ed996dd5336cbfa7394234d1cbbf08a2b78:/services/keepstore/perms.go

diff --git a/services/keepstore/perms.go b/services/keepstore/perms.go
index 143815576b..65160b1868 100644
--- a/services/keepstore/perms.go
+++ b/services/keepstore/perms.go
@@ -80,23 +80,31 @@ func SignLocator(blob_locator string, api_token string, expiry time.Time) string
 		"@" + 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) {