Configuration:

(add-to-list 'load-path "path/to/hidepass") ; (optional)
(require 'hidepass)

Multiline password is disabled by default, configure it with:
(setopt hidepass-multiline-patterns
  '(("^#\\+begin_src pass\n" . "^#\\+end_src")
    ("<secret>" . "</secret>")
    ("---BEGIN PASSWORD---" . "---END PASSWORD---")))