package/prosody: security bump to version 0.11.9

package/prosody: security bump to version 0.11.9

Fixes the following security issues:

- CVE-2021-32918: DoS via insufficient memory consumption controls

  It was discovered that default settings leave Prosody susceptible to
  remote unauthenticated denial-of-service (DoS) attacks via memory
  exhaustion when running under Lua 5.2 or Lua 5.3.  Lua 5.2 is the default
  and recommended Lua version for Prosody 0.11.x series.

- CVE-2021-32920: DoS via repeated TLS renegotiation causing excessive CPU
  consumption

  It was discovered that Prosody does not disable SSL/TLS renegotiation,
  even though this is not used in XMPP.  A malicious client may flood a
  connection with renegotiation requests to consume excessive CPU resources
  on the server.

- CVE-2021-32921: Use of timing-dependent string comparison with sensitive
  values

  It was discovered that Prosody does not use a constant-time algorithm for
  comparing certain secret strings when running under Lua 5.2 or later.
  This can potentially be used in a timing attack to reveal the contents of
  secret strings to an attacker.

- CVE-2021-32917: Use of mod_proxy65 is unrestricted in default
  configuration

  mod_proxy65 is a file transfer proxy provided with Prosody to facilitate
  the transfer of files and other data between XMPP clients.

  It was discovered that the proxy65 component of Prosody allows open access
  by default, even if neither of the users have an XMPP account on the local
  server, allowing unrestricted use of the server’s bandwidth.

- CVE-2021-32919: Undocumented dialback-without-dialback option insecure

  The undocumented option ‘dialback_without_dialback’ enabled an
  experimental feature for server-to-server authentication.  A flaw in this
  feature meant it did not correctly authenticate remote servers, allowing a
  remote server to impersonate another server when this option is enabled.

For more details, see the advisory:
https://prosody.im/security/advisory_20210512/

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>