Open-Xchange: Buffer overread off by one in `rpa_read_buffer`, incomplete fix for CVE-2020-12674

In function rpareadbuffer, the condition in if p end return 0; len = p++; is not strict enough It should be if p = end return 0; len = p++; The fix from https://github.com/dovecot/core/commit/69ad3c902ea4bbf9f21ab1857d8923f975dc6145 is not enough The ASAN stack trace is...