Update mime_types.conf configuration

[patschi]

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What does this PR include?

Short Description

In the last months and years, the default mime_types.conf of rspamd has changed and it might be also useful to make some adjustments to the weight of certain file extensions.

This PR is removing all file extensions from mime_types.conf which are already in rspamd's default configuration at rspamd/src/plugins/lua/mime_types.lua. If file extension is not present or has a different score compared to rspamd default, it is still in the list.

There are also a few major differences to certain file extensions, which might be useful to discuss and carefully adjust. For example, .exe files are rated very 'badly' due to high chance of being malicious, so are other extensions like bat, cmd, etc.

Current suggestion:

# Extensions that are treated as 'bad'
# Number is score multiply factor
bad_extensions = {
  apk = 4,
  appx = 4,
  appxbundle = 4,
  bat = 8,
  cab = 20,
  cmd = 8,
  com = 20,
  diagcfg = 4,
  diagpack = 4,
  dmg = 8,
  ex = 20,
  ex_ = 20,
  exe = 20,
  img = 4,
  jar = 8,
  jnlp = 8,
  js = 8,
  jse = 8,
  lnk = 20,
  mjs = 8,
  msi = 4,
  msix = 4,
  msixbundle = 4,
  ps1 = 8,
  scr = 20,
  sct = 20,
  vb = 20,
  vbe = 20,
  vbs = 20,
  vhd = 4,
  py = 4,
  reg = 8,
  scf = 8,
  vhdx = 4,
};

# Extensions that are particularly penalized for archives
bad_archive_extensions = {
  pptx = 0.5,
  docx = 0.5,
  xlsx = 0.5,
  pdf = 1.0,
  jar = 12,
  jnlp = 12,
  bat = 12,
  cmd = 12,
};

# Used to detect another archive in archive
archive_extensions = {
  tar = 1,
  ['tar.gz'] = 1,
};

As a important reminder: For all remaining and additional file extensions and score weights, please check above default rspamd configuration!

This is meant as a sort-of open discussion on the weighting, I find a good way to achieve weighting fitting most usecases.

Affected Containers

• rspamd

[DerLinkman]

I would also add this to the Docs, that users can still modify this file.

[DerLinkman]

@patschi for the next time, please always create new branches out of staging not master! See Contributing.md too for this :)