[Servercert-wg] Ballot SC40: Security Requirements for Air-Gapped CA Systems

[Ben Wilson]

Ballot SC40: Security Requirements for Air-Gapped CA Systems

Purpose of the Ballot:

This ballot increases the security of Air-Gapped/Offline CA systems
(“Air-Gapped CA Systems”) by clarifying the controls that CAs must
implement to protect them.

Air-Gapped CA systems (usually Root CA private keys) are maintained in
highly secure locations, and while they can share certain exterior physical
controls with online systems, they are not connected to online systems or
the Internet. Thus, they have different operational requirements and
controls due to their separate risk profile. While the scope of the current
Network and Certificate System Security Requirements (NCSSRs) includes
Air-Gapped CA systems, the current NCSSRs focuses on online systems and
contains a number of requirements that are not practical to implement in an
offline environment and could actually increase the risk to such offline
systems.

As an example, access to offline/air-gapped CA systems frequently elevates
the risk to the environment. A quarterly vulnerability scan in the offline
environment is not practical, because there is an increased risk involved
with attaching a scanning device to such Air-Gapped CA system. Just as
another example among several, because such systems are not connected, the
provisions of subsection 1.g (ports and protocols) are not applicable.

This ballot develops a working definition for an “Air-Gapped CA System” to
allow for a clear delineation between those system components that fall
under this category of Air-Gapped/Offline requirements and those under
other requirements. In doing so, the ballot creates two sets of
requirements tailored to their respective operating environments and
characteristics.

Not only does this ballot introduce a new section 5, it also adds
additional physical security requirements for air-gapped CAs by requiring
video monitoring, intrusion detection, and other intrusion prevention
controls to protect Air-Gapped CA Systems against unauthorized physical
access attempts. The new section 5 presents logical security requirements
in subsections a through m and physical security requirements in
subsections p through w.

These proposed subsections in the proposed new section 5 are based on
sections 1 through 3 of the existing NCSSRs as follows:


Description

Offline

Criteria #

General

Criteria #

Logical Security of Air-Gapped CA Systems


Configuration review

5a

1h

Appointing individuals to trusted roles

5b

2a

Grant access to Air-Gapped CAs

5c

1i

Document responsibilities of Trusted roles

5d

2b

Segregation of duties

5e

2d

Require least privileged access for Trusted Roles

5f

2e

All access tracked to individual account

5g

2f

Password requirements

5h

2gi

Review logical access

5i

2j

Implement multi-factor access

5j

2m

Monitor Air-Gapped CA systems

5k

3b

Review logging integrity

5l

3e

Monitor archive and retention of logs

5m

3f

Physical Security of Air-Gapped CA Systems


Grant physical access

5p

1i

Multi-person physical access

5q

1j

Review physical access

5r

2j

Video monitoring

5s

3a

Physical access monitoring

5t

3a

Review accounts with physical access

5u

2j

Monitor retention of physical access of records

5v

3f

Review integrity of physical access logs

5w

3e

This motion is made by Ben Wilson of Mozilla and endorsed by David Kluge of
Google Trust Services and Neil Dunbar of TrustCor.

--- Motion Begins ---

That the CA/Browser Forum Server Certificate Working Group adopt the
following requirements as amendments to the Network and Certificate System
Security Requirements.

1. Replace the current language in section 1.c. with "Maintain Root CA
Systems in a High Security Zone and as Air-Gapped CA Systems, in accordance
with Section 5;"

2. Add a definition of "Air-Gapped CA System" as "A system that is kept
offline or otherwise air-gapped and separated from other systems and that
is used by a CA or Delegated Third Party in storing and managing CA private
keys and performing signing operations."

3. Revise the definition of Security Support System to read:

"A system used to provide physical and logical security support functions,
which MAY include authentication, network boundary control, audit logging,
audit log reduction and analysis, vulnerability scanning, and intrusion
detection (physical intrusion detection, Host-based intrusion detection,
Network-based intrusion detection)."

4. Add a new Section 5 to read as follows:

5. GENERAL PROTECTIONS FOR AIR-GAPPED CA SYSTEMS

This Section 5 separates requirements for Air-Gapped CA Systems into two
categories--logical security and physical security.

Logical Security of Air-Gapped CA Systems

Certification Authorities and Delegated Third Parties SHALL implement the
following controls to ensure the logical security of Air-Gapped CA Systems:

a. Review configurations of Air-Gapped CA Systems at least on an annual
basis;

b. Follow a documented procedure for appointing individuals to those
Trusted Roles that are authorized to operate Air-Gapped CA Systems;

c. Grant logical access to Air-Gapped CA Systems only to persons acting in
Trusted Roles and implement controls so that all logical access to
Air-Gapped CA Systems can be traced back to an accountable individual;

d. Document the responsibilities assigned to Trusted Roles based on the
security principle of multi-person control and the security-related
concerns of the functions to be performed;

e. Ensure that an individual in a Trusted Role acts only within the scope
of such role when performing administrative tasks assigned to that role;

f. Require employees and contractors to observe the principle of "least
privilege" when accessing, or when configuring access privileges on,
Air-Gapped CA Systems;

g. Require that all access to systems and offline key material can be
traced back to an individual in a Trusted Role (through a combination of
recordkeeping, use of logical and physical credentials, authentication
factors, video recording, etc.);

h. If an authentication control used by a Trusted Role is a username and
password, then, where technically feasible require that passwords have at
least twelve (12) characters;

i. Review logical access control lists at least annually and deactivate any
accounts that are no longer necessary for operations;

j. Enforce Multi-Factor Authentication OR multi-party authentication for
administrator access to Air-Gapped CA Systems;

k. Identify those Air-Gapped CA Systems capable of monitoring and logging
system activity and enable those systems to continuously monitor and log
system activity. Back up logs to an external system each time the system is
used or on a quarterly basis, whichever is less frequent;

l. On a quarterly basis or each time the Air-Gapped CA System is used,
whichever is less frequent, check the integrity of the logical access
logging processes and ensure that logging and log-integrity functions are
effective;

m. On a quarterly basis or each time the Air-Gapped CA System is used,
whichever is less frequent, monitor the archival and retention of logical
access logs to ensure that logs are retained for the appropriate amount of
time in accordance with the disclosed business practices and applicable
legislation.

n. Reserved for future use

o. Reserved for future use

Physical Security of Air-Gapped CA Systems

Certification Authorities and Delegated Third Parties SHALL implement the
following controls to ensure the physical security of Air-Gapped CA Systems:

p. Grant physical access to Air-Gapped CA Systems only to persons acting in
Trusted Roles and implement controls so that all physical access to
Air-Gapped CA Systems can be traced back to an accountable individual;

q. Ensure that only personnel assigned to Trusted Roles have physical
access to Air-Gapped CA Systems and multi-person access controls are
enforced at all times;

r. Implement a process that removes physical access of an individual to all
Air-Gapped CA Systems within twenty-four (24) hours upon termination of the
individual’s employment or contracting relationship with the CA or
Delegated Third Party;

s. Implement video monitoring, intrusion detection, and intrusion
prevention controls to protect Air-Gapped CA Systems against unauthorized
physical access attempts;

t. Implement a Security Support System that monitors, detects, and alerts
personnel to any physical access to Air-Gapped CA Systems;

u. Implement a process that prevents physical access of an individual to an
Air-Gapped CA within twenty-four (24) hours of removal from the relevant
authorized Trusted Role, and review lists of holders of physical keys and
combinations to doors and safes as well as logical accounts tied to
physical access controls at least every three (3) months, and;

v. On a quarterly basis or each time the Air-Gapped CA System is used,
whichever is less frequent, monitor the archival and retention of the
physical access logs to ensure that logs are retained for the appropriate
amount of time in accordance with the disclosed business practices and
applicable legislation.

w. On a quarterly basis or each time the Air-Gapped CA System is used,
whichever is less frequent, check the integrity of the physical access
logging processes and ensure that logging and log-integrity functions are
effective.

--- Motion Ends ---

Discussion Period -

This ballot proposes a Final Maintenance Guideline.

The procedure for approval of this ballot is as follows:

Discussion (7+ days)

Start Time: 2021-02-02 21:00 UTC

End Time: not before 2021-02-09 21:00 UTC

Vote for approval (7 days)

Start Time: TBD

End Time: TBD
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