Documentation/process/embargoed-hardware-issues.rst - linux - Git at Google

 .. _embargoed_hardware_issues:

 Embargoed hardware issues
 =========================

 Scope
 -----

 Hardware issues which result in security problems are a different category
 of security bugs than pure software bugs which only affect the Linux
 kernel.

 Hardware issues like Meltdown, Spectre, L1TF etc. must be treated
 differently because they usually affect all Operating Systems ("OS") and
 therefore need coordination across different OS vendors, distributions,
 silicon vendors, hardware integrators, and other parties. For some of the
 issues, software mitigations can depend on microcode or firmware updates,
 which need further coordination.

 .. _Contact:

 Contact
 -------

 The Linux kernel hardware security team is separate from the regular Linux
 kernel security team.

 The team only handles developing fixes for embargoed hardware security
 issues. Reports of pure software security bugs in the Linux kernel are not
 handled by this team and the reporter will be guided to contact the regular
 Linux kernel security team (:ref:`Documentation/admin-guide/
 <securitybugs>`) instead.

 The team can be contacted by email at <hardware-security@kernel.org>. This
 is a private list of security officers who will help you coordinate a fix
 according to our documented process.

 The list is encrypted and email to the list can be sent by either PGP or
 S/MIME encrypted and must be signed with the reporter's PGP key or S/MIME
 certificate. The list's PGP key and S/MIME certificate are available from
 the following URLs:

   - PGP: https://www.kernel.org/static/files/hardware-security.asc
   - S/MIME: https://www.kernel.org/static/files/hardware-security.crt

 While hardware security issues are often handled by the affected silicon
 vendor, we welcome contact from researchers or individuals who have
 identified a potential hardware flaw.

 Hardware security officers
 ^^^^^^^^^^^^^^^^^^^^^^^^^^

 The current team of hardware security officers:

   - Linus Torvalds (Linux Foundation Fellow)
   - Greg Kroah-Hartman (Linux Foundation Fellow)
   - Thomas Gleixner (Linux Foundation Fellow)

 Operation of mailing-lists
 ^^^^^^^^^^^^^^^^^^^^^^^^^^

 The encrypted mailing-lists which are used in our process are hosted on
 Linux Foundation's IT infrastructure. By providing this service, members
 of Linux Foundation's IT operations personnel technically have the
 ability to access the embargoed information, but are obliged to
 confidentiality by their employment contract. Linux Foundation IT
 personnel are also responsible for operating and managing the rest of
 kernel.org's infrastructure.

 The Linux Foundation's current director of IT Project infrastructure is
 Konstantin Ryabitsev.


 Non-disclosure agreements
 -------------------------

 The Linux kernel hardware security team is not a formal body and therefore
 unable to enter into any non-disclosure agreements.  The kernel community
 is aware of the sensitive nature of such issues and offers a Memorandum of
 Understanding instead.


 Memorandum of Understanding
 ---------------------------

 The Linux kernel community has a deep understanding of the requirement to
 keep hardware security issues under embargo for coordination between
 different OS vendors, distributors, silicon vendors, and other parties.

 The Linux kernel community has successfully handled hardware security
 issues in the past and has the necessary mechanisms in place to allow
 community compliant development under embargo restrictions.

 The Linux kernel community has a dedicated hardware security team for
 initial contact, which oversees the process of handling such issues under
 embargo rules.

 The hardware security team identifies the developers (domain experts) who
 will form the initial response team for a particular issue. The initial
 response team can bring in further developers (domain experts) to address
 the issue in the best technical way.

 All involved developers pledge to adhere to the embargo rules and to keep
 the received information confidential. Violation of the pledge will lead to
 immediate exclusion from the current issue and removal from all related
 mailing lists. In addition, the hardware security team will also exclude
 the offender from future issues. The impact of this consequence is a highly
 effective deterrent in our community. In case a violation happens the
 hardware security team will inform the involved parties immediately. If you
 or anyone else becomes aware of a potential violation, please report it
 immediately to the Hardware security officers.


 Process
 ^^^^^^^

 Due to the globally distributed nature of Linux kernel development,
 face-to-face meetings are almost impossible to address hardware security
 issues.  Phone conferences are hard to coordinate due to time zones and
 other factors and should be only used when absolutely necessary. Encrypted
 email has been proven to be the most effective and secure communication
 method for these types of issues.

 Start of Disclosure
 """""""""""""""""""

 Disclosure starts by emailing the Linux kernel hardware security team per
 the Contact section above.  This initial contact should contain a
 description of the problem and a list of any known affected silicon. If
 your organization builds or distributes the affected hardware, we encourage
 you to also consider what other hardware could be affected.  The disclosing
 party is responsible for contacting the affected silicon vendors in a
 timely manner.

 The hardware security team will provide an incident-specific encrypted
 mailing list which will be used for initial discussion with the reporter,
 further disclosure, and coordination of fixes.

 The hardware security team will provide the disclosing party a list of
 developers (domain experts) who should be informed initially about the
 issue after confirming with the developers that they will adhere to this
 Memorandum of Understanding and the documented process. These developers
 form the initial response team and will be responsible for handling the
 issue after initial contact. The hardware security team is supporting the
 response team, but is not necessarily involved in the mitigation
 development process.

 While individual developers might be covered by a non-disclosure agreement
 via their employer, they cannot enter individual non-disclosure agreements
 in their role as Linux kernel developers. They will, however, agree to
 adhere to this documented process and the Memorandum of Understanding.

 The disclosing party should provide a list of contacts for all other
 entities who have already been, or should be, informed about the issue.
 This serves several purposes:

  - The list of disclosed entities allows communication across the
    industry, e.g. other OS vendors, HW vendors, etc.

  - The disclosed entities can be contacted to name experts who should
    participate in the mitigation development.

  - If an expert who is required to handle an issue is employed by a listed
    entity or member of an listed entity, then the response teams can
    request the disclosure of that expert from that entity. This ensures
    that the expert is also part of the entity's response team.

 Disclosure
 """"""""""

 The disclosing party provides detailed information to the initial response
 team via the specific encrypted mailing-list.

 From our experience, the technical documentation of these issues is usually
 a sufficient starting point, and further technical clarification is best
 done via email.

 Mitigation development
 """"""""""""""""""""""

 The initial response team sets up an encrypted mailing-list or repurposes
 an existing one if appropriate.

 Using a mailing list is close to the normal Linux development process and
 has been successfully used to develop mitigations for various hardware
 security issues in the past.

 The mailing list operates in the same way as normal Linux development.
 Patches are posted, discussed, and reviewed and if agreed upon, applied to
 a non-public git repository which is only accessible to the participating
 developers via a secure connection. The repository contains the main
 development branch against the mainline kernel and backport branches for
 stable kernel versions as necessary.

 The initial response team will identify further experts from the Linux
 kernel developer community as needed.  Any involved party can suggest
 further experts to be included, each of which will be subject to the same
 requirements outlined above.

 Bringing in experts can happen at any time in the development process and
 needs to be handled in a timely manner.

 If an expert is employed by or a member of an entity on the disclosure list
 provided by the disclosing party, then participation will be requested from
 the relevant entity.

 If not, then the disclosing party will be informed about the experts'
 participation. The experts are covered by the Memorandum of Understanding
 and the disclosing party is requested to acknowledge their participation.
 In the case where the disclosing party has a compelling reason to object,
 any objection must to be raised within five working days and resolved with
 the incident team immediately. If the disclosing party does not react
 within five working days this is taken as silent acknowledgment.

 After the incident team acknowledges or resolves an objection, the expert
 is disclosed and brought into the development process.

 List participants may not communicate about the issue outside of the
 private mailing list. List participants may not use any shared resources
 (e.g. employer build farms, CI systems, etc) when working on patches.

 Early access
 """"""""""""

 The patches discussed and developed on the list can neither be distributed
 to any individual who is not a member of the response team nor to any other
 organization.

 To allow the affected silicon vendors to work with their internal teams and
 industry partners on testing, validation, and logistics, the following
 exception is provided:

 	Designated representatives of the affected silicon vendors are
 	allowed to hand over the patches at any time to the silicon
 	vendor’s response team. The representative must notify the kernel
 	response team about the handover. The affected silicon vendor must
 	have and maintain their own documented security process for any
 	patches shared with their response team that is consistent with
 	this policy.

 	The silicon vendor’s response team can distribute these patches to
 	their industry partners and to their internal teams under the
 	silicon vendor’s documented security process. Feedback from the
 	industry partners goes back to the silicon vendor and is
 	communicated by the silicon vendor to the kernel response team.

 	The handover to the silicon vendor’s response team removes any
 	responsibility or liability from the kernel response team regarding
 	premature disclosure, which happens due to the involvement of the
 	silicon vendor’s internal teams or industry partners. The silicon
 	vendor guarantees this release of liability by agreeing to this
 	process.

 Coordinated release
 """""""""""""""""""

 The involved parties will negotiate the date and time when the embargo
 ends. At that point, the prepared mitigations are published into the
 relevant kernel trees.  There is no pre-notification process: the
 mitigations are published in public and available to everyone at the same
 time.

 While we understand that hardware security issues need coordinated embargo
 time, the embargo time should be constrained to the minimum time that is
 required for all involved parties to develop, test, and prepare their
 mitigations. Extending embargo time artificially to meet conference talk
 dates or other non-technical reasons creates more work and burden for the
 involved developers and response teams as the patches need to be kept up to
 date in order to follow the ongoing upstream kernel development, which
 might create conflicting changes.

 CVE assignment
 """"""""""""""

 Neither the hardware security team nor the initial response team assign
 CVEs, nor are CVEs required for the development process. If CVEs are
 provided by the disclosing party they can be used for documentation
 purposes.

 Process ambassadors
 -------------------

 For assistance with this process we have established ambassadors in various
 organizations, who can answer questions about or provide guidance on the
 reporting process and further handling. Ambassadors are not involved in the
 disclosure of a particular issue, unless requested by a response team or by
 an involved disclosed party. The current ambassadors list:

   ============= ========================================================
   AMD		Tom Lendacky <thomas.lendacky@amd.com>
   Ampere	Darren Hart <darren@os.amperecomputing.com>
   ARM		Catalin Marinas <catalin.marinas@arm.com>
   IBM Power	Michael Ellerman <ellerman@au.ibm.com>
   IBM Z		Christian Borntraeger <borntraeger@de.ibm.com>
   Intel		Tony Luck <tony.luck@intel.com>
   Qualcomm	Trilok Soni <quic_tsoni@quicinc.com>
   RISC-V	Palmer Dabbelt <palmer@dabbelt.com>
   Samsung	Javier González <javier.gonz@samsung.com>

   Microsoft	James Morris <jamorris@linux.microsoft.com>
   Xen		Andrew Cooper <andrew.cooper3@citrix.com>

   Canonical	John Johansen <john.johansen@canonical.com>
   Debian	Ben Hutchings <ben@decadent.org.uk>
   Oracle	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
   Red Hat	Josh Poimboeuf <jpoimboe@redhat.com>
   SUSE		Jiri Kosina <jkosina@suse.cz>

   Google	Kees Cook <keescook@chromium.org>

   LLVM		Nick Desaulniers <ndesaulniers@google.com>
   ============= ========================================================

 If you want your organization to be added to the ambassadors list, please
 contact the hardware security team. The nominated ambassador has to
 understand and support our process fully and is ideally well-connected in
 the Linux kernel community.

 Encrypted mailing-lists
 -----------------------

 We use encrypted mailing lists for communication. The operating principle
 of these lists is that email sent to the list is encrypted either with the
 list's PGP key or with the list's S/MIME certificate. The mailing list
 software decrypts the email and re-encrypts it individually for each
 subscriber with the subscriber's PGP key or S/MIME certificate. Details
 about the mailing list software and the setup that is used to ensure the
 security of the lists and protection of the data can be found here:
 https://korg.wiki.kernel.org/userdoc/remail.

 List keys
 ^^^^^^^^^

 For initial contact see the :ref:`Contact` section above. For incident
 specific mailing lists, the key and S/MIME certificate are conveyed to the
 subscribers by email sent from the specific list.

 Subscription to incident-specific lists
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

 Subscription to incident-specific lists is handled by the response teams.
 Disclosed parties who want to participate in the communication send a list
 of potential experts to the response team so the response team can validate
 subscription requests.

 Each subscriber needs to send a subscription request to the response team
 by email. The email must be signed with the subscriber's PGP key or S/MIME
 certificate. If a PGP key is used, it must be available from a public key
 server and is ideally connected to the Linux kernel's PGP web of trust. See
 also: https://www.kernel.org/signature.html.

 The response team verifies that the subscriber request is valid and adds
 the subscriber to the list. After subscription the subscriber will receive
 email from the mailing-list which is signed either with the list's PGP key
 or the list's S/MIME certificate. The subscriber's email client can extract
 the PGP key or the S/MIME certificate from the signature so the subscriber
 can send encrypted email to the list.
	.. _embargoed_hardware_issues:

	Embargoed hardware issues
	=========================

	Scope
	-----

	Hardware issues which result in security problems are a different category
	of security bugs than pure software bugs which only affect the Linux
	kernel.

	Hardware issues like Meltdown, Spectre, L1TF etc. must be treated
	differently because they usually affect all Operating Systems ("OS") and
	therefore need coordination across different OS vendors, distributions,
	silicon vendors, hardware integrators, and other parties. For some of the
	issues, software mitigations can depend on microcode or firmware updates,
	which need further coordination.

	.. _Contact:

	Contact
	-------

	The Linux kernel hardware security team is separate from the regular Linux
	kernel security team.

	The team only handles developing fixes for embargoed hardware security
	issues. Reports of pure software security bugs in the Linux kernel are not
	handled by this team and the reporter will be guided to contact the regular
	Linux kernel security team (:ref:`Documentation/admin-guide/
	<securitybugs>`) instead.

	The team can be contacted by email at <hardware-security@kernel.org>. This
	is a private list of security officers who will help you coordinate a fix
	according to our documented process.

	The list is encrypted and email to the list can be sent by either PGP or
	S/MIME encrypted and must be signed with the reporter's PGP key or S/MIME
	certificate. The list's PGP key and S/MIME certificate are available from
	the following URLs:

	- PGP: https://www.kernel.org/static/files/hardware-security.asc
	- S/MIME: https://www.kernel.org/static/files/hardware-security.crt

	While hardware security issues are often handled by the affected silicon
	vendor, we welcome contact from researchers or individuals who have
	identified a potential hardware flaw.

	Hardware security officers
	^^^^^^^^^^^^^^^^^^^^^^^^^^

	The current team of hardware security officers:

	- Linus Torvalds (Linux Foundation Fellow)
	- Greg Kroah-Hartman (Linux Foundation Fellow)
	- Thomas Gleixner (Linux Foundation Fellow)

	Operation of mailing-lists
	^^^^^^^^^^^^^^^^^^^^^^^^^^

	The encrypted mailing-lists which are used in our process are hosted on
	Linux Foundation's IT infrastructure. By providing this service, members
	of Linux Foundation's IT operations personnel technically have the
	ability to access the embargoed information, but are obliged to
	confidentiality by their employment contract. Linux Foundation IT
	personnel are also responsible for operating and managing the rest of
	kernel.org's infrastructure.

	The Linux Foundation's current director of IT Project infrastructure is
	Konstantin Ryabitsev.


	Non-disclosure agreements
	-------------------------

	The Linux kernel hardware security team is not a formal body and therefore
	unable to enter into any non-disclosure agreements. The kernel community
	is aware of the sensitive nature of such issues and offers a Memorandum of
	Understanding instead.


	Memorandum of Understanding
	---------------------------

	The Linux kernel community has a deep understanding of the requirement to
	keep hardware security issues under embargo for coordination between
	different OS vendors, distributors, silicon vendors, and other parties.

	The Linux kernel community has successfully handled hardware security
	issues in the past and has the necessary mechanisms in place to allow
	community compliant development under embargo restrictions.

	The Linux kernel community has a dedicated hardware security team for
	initial contact, which oversees the process of handling such issues under
	embargo rules.

	The hardware security team identifies the developers (domain experts) who
	will form the initial response team for a particular issue. The initial
	response team can bring in further developers (domain experts) to address
	the issue in the best technical way.

	All involved developers pledge to adhere to the embargo rules and to keep
	the received information confidential. Violation of the pledge will lead to
	immediate exclusion from the current issue and removal from all related
	mailing lists. In addition, the hardware security team will also exclude
	the offender from future issues. The impact of this consequence is a highly
	effective deterrent in our community. In case a violation happens the
	hardware security team will inform the involved parties immediately. If you
	or anyone else becomes aware of a potential violation, please report it
	immediately to the Hardware security officers.


	Process
	^^^^^^^

	Due to the globally distributed nature of Linux kernel development,
	face-to-face meetings are almost impossible to address hardware security
	issues. Phone conferences are hard to coordinate due to time zones and
	other factors and should be only used when absolutely necessary. Encrypted
	email has been proven to be the most effective and secure communication
	method for these types of issues.

	Start of Disclosure
	"""""""""""""""""""

	Disclosure starts by emailing the Linux kernel hardware security team per
	the Contact section above. This initial contact should contain a
	description of the problem and a list of any known affected silicon. If
	your organization builds or distributes the affected hardware, we encourage
	you to also consider what other hardware could be affected. The disclosing
	party is responsible for contacting the affected silicon vendors in a
	timely manner.

	The hardware security team will provide an incident-specific encrypted
	mailing list which will be used for initial discussion with the reporter,
	further disclosure, and coordination of fixes.

	The hardware security team will provide the disclosing party a list of
	developers (domain experts) who should be informed initially about the
	issue after confirming with the developers that they will adhere to this
	Memorandum of Understanding and the documented process. These developers
	form the initial response team and will be responsible for handling the
	issue after initial contact. The hardware security team is supporting the
	response team, but is not necessarily involved in the mitigation
	development process.

	While individual developers might be covered by a non-disclosure agreement
	via their employer, they cannot enter individual non-disclosure agreements
	in their role as Linux kernel developers. They will, however, agree to
	adhere to this documented process and the Memorandum of Understanding.

	The disclosing party should provide a list of contacts for all other
	entities who have already been, or should be, informed about the issue.
	This serves several purposes:

	- The list of disclosed entities allows communication across the
	industry, e.g. other OS vendors, HW vendors, etc.

	- The disclosed entities can be contacted to name experts who should
	participate in the mitigation development.

	- If an expert who is required to handle an issue is employed by a listed
	entity or member of an listed entity, then the response teams can
	request the disclosure of that expert from that entity. This ensures
	that the expert is also part of the entity's response team.

	Disclosure
	""""""""""

	The disclosing party provides detailed information to the initial response
	team via the specific encrypted mailing-list.

	From our experience, the technical documentation of these issues is usually
	a sufficient starting point, and further technical clarification is best
	done via email.

	Mitigation development
	""""""""""""""""""""""

	The initial response team sets up an encrypted mailing-list or repurposes
	an existing one if appropriate.

	Using a mailing list is close to the normal Linux development process and
	has been successfully used to develop mitigations for various hardware
	security issues in the past.

	The mailing list operates in the same way as normal Linux development.
	Patches are posted, discussed, and reviewed and if agreed upon, applied to
	a non-public git repository which is only accessible to the participating
	developers via a secure connection. The repository contains the main
	development branch against the mainline kernel and backport branches for
	stable kernel versions as necessary.

	The initial response team will identify further experts from the Linux
	kernel developer community as needed. Any involved party can suggest
	further experts to be included, each of which will be subject to the same
	requirements outlined above.

	Bringing in experts can happen at any time in the development process and
	needs to be handled in a timely manner.

	If an expert is employed by or a member of an entity on the disclosure list
	provided by the disclosing party, then participation will be requested from
	the relevant entity.

	If not, then the disclosing party will be informed about the experts'
	participation. The experts are covered by the Memorandum of Understanding
	and the disclosing party is requested to acknowledge their participation.
	In the case where the disclosing party has a compelling reason to object,
	any objection must to be raised within five working days and resolved with
	the incident team immediately. If the disclosing party does not react
	within five working days this is taken as silent acknowledgment.

	After the incident team acknowledges or resolves an objection, the expert
	is disclosed and brought into the development process.

	List participants may not communicate about the issue outside of the
	private mailing list. List participants may not use any shared resources
	(e.g. employer build farms, CI systems, etc) when working on patches.

	Early access
	""""""""""""

	The patches discussed and developed on the list can neither be distributed
	to any individual who is not a member of the response team nor to any other
	organization.

	To allow the affected silicon vendors to work with their internal teams and
	industry partners on testing, validation, and logistics, the following
	exception is provided:

	Designated representatives of the affected silicon vendors are
	allowed to hand over the patches at any time to the silicon
	vendor’s response team. The representative must notify the kernel
	response team about the handover. The affected silicon vendor must
	have and maintain their own documented security process for any
	patches shared with their response team that is consistent with
	this policy.

	The silicon vendor’s response team can distribute these patches to
	their industry partners and to their internal teams under the
	silicon vendor’s documented security process. Feedback from the
	industry partners goes back to the silicon vendor and is
	communicated by the silicon vendor to the kernel response team.

	The handover to the silicon vendor’s response team removes any
	responsibility or liability from the kernel response team regarding
	premature disclosure, which happens due to the involvement of the
	silicon vendor’s internal teams or industry partners. The silicon
	vendor guarantees this release of liability by agreeing to this
	process.

	Coordinated release
	"""""""""""""""""""

	The involved parties will negotiate the date and time when the embargo
	ends. At that point, the prepared mitigations are published into the
	relevant kernel trees. There is no pre-notification process: the
	mitigations are published in public and available to everyone at the same
	time.

	While we understand that hardware security issues need coordinated embargo
	time, the embargo time should be constrained to the minimum time that is
	required for all involved parties to develop, test, and prepare their
	mitigations. Extending embargo time artificially to meet conference talk
	dates or other non-technical reasons creates more work and burden for the
	involved developers and response teams as the patches need to be kept up to
	date in order to follow the ongoing upstream kernel development, which
	might create conflicting changes.

	CVE assignment
	""""""""""""""

	Neither the hardware security team nor the initial response team assign
	CVEs, nor are CVEs required for the development process. If CVEs are
	provided by the disclosing party they can be used for documentation
	purposes.

	Process ambassadors
	-------------------

	For assistance with this process we have established ambassadors in various
	organizations, who can answer questions about or provide guidance on the
	reporting process and further handling. Ambassadors are not involved in the
	disclosure of a particular issue, unless requested by a response team or by
	an involved disclosed party. The current ambassadors list:

	============= ========================================================
	AMD Tom Lendacky <thomas.lendacky@amd.com>
	Ampere Darren Hart <darren@os.amperecomputing.com>
	ARM Catalin Marinas <catalin.marinas@arm.com>
	IBM Power Michael Ellerman <ellerman@au.ibm.com>
	IBM Z Christian Borntraeger <borntraeger@de.ibm.com>
	Intel Tony Luck <tony.luck@intel.com>
	Qualcomm Trilok Soni <quic_tsoni@quicinc.com>
	RISC-V Palmer Dabbelt <palmer@dabbelt.com>
	Samsung Javier González <javier.gonz@samsung.com>

	Microsoft James Morris <jamorris@linux.microsoft.com>
	Xen Andrew Cooper <andrew.cooper3@citrix.com>

	Canonical John Johansen <john.johansen@canonical.com>
	Debian Ben Hutchings <ben@decadent.org.uk>
	Oracle Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
	Red Hat Josh Poimboeuf <jpoimboe@redhat.com>
	SUSE Jiri Kosina <jkosina@suse.cz>

	Google Kees Cook <keescook@chromium.org>

	LLVM Nick Desaulniers <ndesaulniers@google.com>
	============= ========================================================

	If you want your organization to be added to the ambassadors list, please
	contact the hardware security team. The nominated ambassador has to
	understand and support our process fully and is ideally well-connected in
	the Linux kernel community.

	Encrypted mailing-lists
	-----------------------

	We use encrypted mailing lists for communication. The operating principle
	of these lists is that email sent to the list is encrypted either with the
	list's PGP key or with the list's S/MIME certificate. The mailing list
	software decrypts the email and re-encrypts it individually for each
	subscriber with the subscriber's PGP key or S/MIME certificate. Details
	about the mailing list software and the setup that is used to ensure the
	security of the lists and protection of the data can be found here:
	https://korg.wiki.kernel.org/userdoc/remail.

	List keys
	^^^^^^^^^

	For initial contact see the :ref:`Contact` section above. For incident
	specific mailing lists, the key and S/MIME certificate are conveyed to the
	subscribers by email sent from the specific list.

	Subscription to incident-specific lists
	^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

	Subscription to incident-specific lists is handled by the response teams.
	Disclosed parties who want to participate in the communication send a list
	of potential experts to the response team so the response team can validate
	subscription requests.

	Each subscriber needs to send a subscription request to the response team
	by email. The email must be signed with the subscriber's PGP key or S/MIME
	certificate. If a PGP key is used, it must be available from a public key
	server and is ideally connected to the Linux kernel's PGP web of trust. See
	also: https://www.kernel.org/signature.html.

	The response team verifies that the subscriber request is valid and adds
	the subscriber to the list. After subscription the subscriber will receive
	email from the mailing-list which is signed either with the list's PGP key
	or the list's S/MIME certificate. The subscriber's email client can extract
	the PGP key or the S/MIME certificate from the signature so the subscriber
	can send encrypted email to the list.