-/*
-Permissions management on Arvados locator hashes.
-
-The permissions structure for Arvados is as follows (from
-https://arvados.org/issues/2328)
-
-A Keep locator string has the following format:
-
- [hash]+[size]+A[signature]@[timestamp]
-
-The "signature" string here is a cryptographic hash, expressed as a
-string of hexadecimal digits, and timestamp is a 32-bit Unix timestamp
-expressed as a hexadecimal number. e.g.:
-
- acbd18db4cc2f85cedef654fccc4a4d8+3+A257f3f5f5f0a4e4626a18fc74bd42ec34dcb228a@7fffffff
-
-The signature represents a guarantee that this locator was generated
-by either Keep or the API server for use with the supplied API token.
-If a request to Keep includes a locator with a valid signature and is
-accompanied by the proper API token, the user has permission to GET
-that object.
-
-The signature may be generated either by Keep (after the user writes a
-block) or by the API server (if the user has can_read permission on
-the specified object). Keep and API server share a secret that is used
-to generate signatures.
-
-To verify a permission hint, Keep generates a new hint for the
-requested object (using the locator string, the timestamp, the
-permission secret and the user's API token, which must appear in the
-request headers) and compares it against the hint included in the
-request. If the permissions do not match, or if the API token is not
-present, Keep returns a 401 error.
-*/
+// Generate and verify permission signatures for Keep locators.
+//
+// See https://dev.arvados.org/projects/arvados/wiki/Keep_locator_format
package keepclient
ErrSignatureMissing = errors.New("Missing signature")
)
-// makePermSignature returns a string representing the signed permission
-// hint for the blob identified by blobHash, apiToken, expiration timestamp, and permission secret.
-//
-// The permissionSecret is the secret key used to generate SHA1 digests
-// for permission hints. apiserver and Keep must use the same key.
-func makePermSignature(blobHash string, apiToken string, expiry string, permissionSecret []byte) string {
+// makePermSignature generates a SHA-1 HMAC digest for the given blob,
+// token, expiry, and site secret.
+func makePermSignature(blobHash, apiToken, expiry string, permissionSecret []byte) string {
hmac := hmac.New(sha1.New, permissionSecret)
hmac.Write([]byte(blobHash))
hmac.Write([]byte("@"))
return fmt.Sprintf("%x", digest)
}
-// SignLocator takes a blobLocator, an apiToken, an expiry time, and a permission secret
-// and returns a signed locator string.
-func SignLocator(blobLocator string, apiToken string, expiry time.Time, permissionSecret []byte) string {
- // If no permission secret or API token is available,
- // return an unsigned locator.
- if permissionSecret == nil || apiToken == "" {
+// SignLocator returns blobLocator with a permission signature
+// added. If either permissionSecret or apiToken is empty, blobLocator
+// is returned untouched.
+//
+// This function is intended to be used by system components and admin
+// utilities: userland programs do not know the permissionSecret.
+func SignLocator(blobLocator, apiToken string, expiry time.Time, permissionSecret []byte) string {
+ if len(permissionSecret) == 0 || apiToken == "" {
return blobLocator
}
- // Extract the hash from the blob locator, omitting any size hint that may be present.
+ // Strip off all hints: only the hash is used to sign.
blobHash := strings.Split(blobLocator, "+")[0]
- // Return the signed locator string.
timestampHex := fmt.Sprintf("%08x", expiry.Unix())
return blobLocator +
"+A" + makePermSignature(blobHash, apiToken, timestampHex, permissionSecret) +
// either ExpiredError (if the timestamp has expired, which is
// something the client could have figured out independently) or
// PermissionError.
-func VerifySignature(signedLocator string, apiToken string, permissionSecret []byte) error {
+//
+// This function is intended to be used by system components and admin
+// utilities: userland programs do not know the permissionSecret.
+func VerifySignature(signedLocator, apiToken string, permissionSecret []byte) error {
matches := signedLocatorRe.FindStringSubmatch(signedLocator)
if matches == nil {
- // Could not find a permission signature at all
return ErrSignatureMissing
}
blobHash := matches[1]
return nil
}
-// parseHexTimestamp parses timestamp
func parseHexTimestamp(timestampHex string) (ts time.Time, err error) {
if tsInt, e := strconv.ParseInt(timestampHex, 16, 0); e == nil {
ts = time.Unix(tsInt, 0)