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platform_external_selinux/secilc/docs/cil_context_statement.md
bauen1 057d72af2d secilc/docs: use fenced code blocks for cil examples 
Also fixes the occasional missing brackets as higlighted by my editor,
however the individual examples where not reviewed much closer.

secilc was chosen as language name because the compiler is named secilc
and outside of SELinux the name cil is less searchable and could lead to
confusion.

Signed-off-by: Jonathan Hettwer <j2468h@gmail.com>
2021-02-16 09:32:29 -05:00

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Context Statement

Contexts are formed using previously declared parameters and may be named or anonymous where:

  • Named - The context is declared with a context identifier that is used as a reference.

  • Anonymous - They are defined within the CIL labeling statement using user, role etc. identifiers.

Each type is shown in the examples.

context

Declare an SELinux security context identifier for labeling. The range (or current and clearance levels) MUST be defined whether the policy is MLS/MCS enabled or not.

Statement definition:

    (context context_id (user_id role_id type_id levelrange_id)))

Where:

context

The context keyword.

context_id

The context identifier.

user_id

A single previously declared user identifier.

role_id

A single previously declared role identifier.

type_id

A single previously declared type or typealias identifier.

levelrange_id

A single previously declared levelrange identifier. This entry may also be defined by anonymous or named level, sensitivity, sensitivityalias, category, categoryalias or categoryset as discussed in the Multi-Level Security Labeling Statements section and shown in the examples.

Examples:

This example uses a named context definition:

    (context runas_exec_context (u object_r exec low_low))

    (filecon "/system/bin/run-as" file runas_exec_context)

to resolve/build a file_contexts entry of (assuming MLS enabled policy):

    /system/bin/run-as  -- u:object_r:runas.exec:s0-s0

This example uses an anonymous context where the previously declared user role type levelrange identifiers are used to specify two portcon statements:

    (portcon udp 1024 (test.user object_r test.process ((s0) (s1))))
    (portcon tcp 1024 (test.user object_r test.process (system_low system_high)))

This example uses an anonymous context for the first and named context for the second in a netifcon statement:

    (context netif_context (test.user object_r test.process ((s0 (c0)) (s1 (c0)))))

    (netifcon eth04 (test.user object_r test.process ((s0 (c0)) (s1 (c0)))) netif_context)