Infer interface parameter types and check for interface-template mis-declarations

[cgzones]

• Infer parameter types of interfaces and templates

  Infer the type of parameters of templates and interfaces.
  This can help find mis-declarations, see next commit.

  In the future this can be used for further checks, e.g. find
  discrepancies between the kind of a parameter and its documentation.

• Add checks for template/interface mis-declarations

  Interfaces in the refpolicy should not:

  • declare anything (no side effects)
  • use prefix parameters

  Add one check to find interfaces that should be declared as a template
  and one check to find templates that can be declared as an interface.

  Refpolicy findings:

  qemu.if:            112: (S): Template qemu_role might be declared as an interface (S-012)
  wm.if:              142: (S): Interface wm_dbus_chat should be a template, due to parameter 0 (S-011)
  wm.if:              250: (S): Interface wm_write_pipes should be a template, due to parameter 0 (S-011)
  gnome.if:           673: (S): Interface gnome_dbus_chat_gkeyringd should be a template, due to parameter 0 (S-011)
  gnome.if:           741: (S): Interface gnome_stream_connect_gkeyringd should be a template, due to parameter 0 (S-011)
  userdomain.if:     1431: (S): Template userdom_security_admin_template might be declared as an interface (S-012)
  kismet.if:           18: (S): Template kismet_role might be declared as an interface (S-012)
  dbus.if:            193: (S): Interface dbus_connect_spec_session_bus should be a template, due to parameter 0 (S-011)
  dbus.if:            245: (S): Interface dbus_spec_session_bus_client should be a template, due to parameter 0 (S-011)
  dbus.if:            298: (S): Interface dbus_send_spec_session_bus should be a template, due to parameter 0 (S-011)
  dbus.if:            436: (S): Interface dbus_spec_session_domain should be a template, due to parameter 0 (S-011)
  rlogin.if:           32: (S): Template rlogin_read_home_content might be declared as an interface (S-012)
  git.if:              18: (S): Template git_role might be declared as an interface (S-012)
  Found the following issue counts:
  S-011: 8
  S-012: 5
  

  Closes: Suggest to change template to interface if appropriate #205

[dburgener]

typo, uses -> used

[dburgener]

Can this (and infer_interface) get a comment explaining their usage? It's not clear to me from the names, and it's slow progress trying to infer from the implementation.

[dburgener]

Okay, reading more, I think I have a rough idea of what these are both for based on how they're used. I still would like to have something with the functions to help orient anyone reading the code.

[dburgener]

Looks like a few lines of spaces got in this file (here and line 213 below)

[dburgener]

I may very well be missing something here, but I'm concerned about the situation where a parameter is incorrectly used in a way that would infer as two different parameters. Something like:

allow $1 foo_t:file read;
role $1 types foo_t;

This would be a compile error, but I think the logic here would end up setting the flavor of $1 to PARAM_ROLE, since the second line just overwrites the first? It seems like it would be valuable info to have to know if a parameter was being used inconsistently.

Then again, I could definitely be missing something, so feel free to let me know if this scenario is already handled.

[cgzones]

True, a subsequent usage of the same no yet final inferred parameter will completely override the current type.
Probably the inferred state shouldn't be a type of an enum but a bit-mask where its possible to store the information a parameter is used as a type-or-attribute, a role and a template string-part. So analysis checks can then create reports like "Parameter X has conflicting usages", "Interface foo uses templated parameter X (declare as template)".