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70 строки
4.0 KiB
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70 строки
4.0 KiB
ReStructuredText
Utility Process
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===============
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.. warning::
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As of january 2022, this process is under heavy work, and many things can
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evolve. Documentation might not always be as accurate as it should be.
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Please reach to #ipc if you intent to add a new utility.
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The utility process is used to provide a simple way to implement IPC actor with
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some more specific sandboxing properties, in case where you don't need or want
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to deal with the extra complexity of adding a whole new process type but you
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just want to apply different sandboxing policies.
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To implement such an actor, you will have to follow a few steps like for
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implementing the trivial example visible in `EmptyUtil
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<https://phabricator.services.mozilla.com/D126402>`_:
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- Define a new IPC actor, e.g., ``PEmptyUtil`` that allows to get some string
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via ``GetSomeString()`` from the child to the parent
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- In the ``PUtilityProcess`` definition, expose a new child-level method,
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e.g., ``StartEmptyUtilService(Endpoint<PEmptyUtilChild>)``
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- Implement ``EmptyUtilChild`` and ``EmptyUtilParent`` classes both deriving
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from their ``PEmptyUtilXX``. If you want or need to run things from a
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different thread, you can have a look at ``UtilityProcessGenericActor``
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- Make sure both are refcounted
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- Expose your new service on ``UtilityProcessManager`` with a method
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performing the heavy lifting of starting your process, you can take
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inspiration from ``StartEmptyUtil()`` in the sample.
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- Ideally, this starting method should rely on `StartUtility() <https://searchfox.org/mozilla-central/rev/fb511723f821ceabeea23b123f1c50c9e93bde9d/ipc/glue/UtilityProcessManager.cpp#210-258,266>`_
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- To use ``StartUtility()`` mentioned above, please ensure that you provide
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a ``nsresult BindToUtilityProcess(RefPtr<UtilityProcessParent>
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aUtilityParent)``. Usually, it should be in charge of creating a set of
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endpoints and performing ``Bind()`` to setup the IPC. You can see some example for `Utility AudioDecoder <https://searchfox.org/mozilla-central/rev/4b3039b48c3cb67774270ebcc2a7d8624d888092/ipc/glue/UtilityAudioDecoderChild.h#31-51>`_
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- For proper user-facing exposition in ``about:processes`` you will have to also provide an actor
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name via a method ``UtilityActorName GetActorName() { return UtilityActorName::EmptyUtil; }``
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+ Add member within `enum WebIDLUtilityActorName in <https://searchfox.org/mozilla-central/rev/fb511723f821ceabeea23b123f1c50c9e93bde9d/dom/chrome-webidl/ChromeUtils.webidl#686-689>`_
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+ Add member within `enum class UtilityActorName of <https://searchfox.org/mozilla-central/rev/fb511723f821ceabeea23b123f1c50c9e93bde9d/toolkit/components/processtools/ProcInfo.h#71-74>`_
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+ Update mapping in `switch case <https://searchfox.org/mozilla-central/rev/fb511723f821ceabeea23b123f1c50c9e93bde9d/dom/base/ChromeUtils.cpp#916-919>`_ and update the `static assert <https://searchfox.org/mozilla-central/rev/fb511723f821ceabeea23b123f1c50c9e93bde9d/dom/base/ChromeUtils.cpp#910-911>`_
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- Handle reception of ``StartEmptyUtilService`` on the child side of
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``UtilityProcess`` within ``RecvStartEmptyUtilService()``
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- The specific sandboxing requirements can be implemented by tracking
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``SandboxingKind``, and it starts within `UtilityProcessSandboxing header
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<https://searchfox.org/mozilla-central/source/ipc/glue/UtilityProcessSandboxing.h>`_
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- Try and make sure you at least add some ``gtest`` coverage of your new
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actor, for example like in `existing gtest
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<https://searchfox.org/mozilla-central/source/ipc/glue/test/gtest/TestUtilityProcess.cpp>`_
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- Also ensure actual sandbox testing within
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+ ``SandboxTest`` to start your new process,
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`<https://searchfox.org/mozilla-central/source/security/sandbox/common/test/SandboxTest.cpp>`_
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+ ``SandboxTestingChildTests`` to define the test
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`<https://searchfox.org/mozilla-central/source/security/sandbox/common/test/SandboxTestingChildTests.h>`_
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+ ``SandboxTestingChild`` to run your test
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`<https://searchfox.org/mozilla-central/source/security/sandbox/common/test/SandboxTestingChild.cpp>`_
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