[cabf_netsec] Minutes from Today's Call 19-Oct-2017

Moudrick M. Dadashov md at ssc.lt
Wed Oct 25 13:43:17 MST 2017


ETSI TR 103 456 V1.1.1 (2017-10) Implementation of the Network and 
Information Security (NIS) Directive



On 10/20/2017 2:39 AM, Ben Wilson via Netsec wrote:
> In Attendance:  Ben Wilson, Fotis Loukos, Travis Graham, Xiu Lei, 
> Robin Alden, Wayne Thayer, Dimitris Zacharopoulos, Tim Hollebeek, Neil 
> Dunbar, Tobi Josefowitz, Ryan Hurst, Kefeng Chen, Rick Agarwala, 
> Patrick Milot, Colin McIntyre
> Ben noted that the last call was before the F2F.  During the F2F, we 
> recapped our progress and explained why we are working on what we 
> are.  He explained that we were going to try and go to the next item 
> to discuss in the Network Security Requirements, but that it might be 
> based on what topic was easier to tackle, rather than on the 
> prioritized list.
> Dimitris gave an update on the work of the subgroup that has been 
> discussing the threat/risk assessment and CA system architecture. 
> Dimitris explained that it was hard to participate during the F2F 
> based on technical difficulties.  The group has started listing the 
> risks and some of the mitigating factors.  The subgroup would like 
> more participation.  The subgroup will consider simplifying next steps 
> by just documenting basic vulnerabilities and threats and omitting the 
> compensating controls for now.
> Neil suggested that the subgroup begin meeting weekly.  Weekly 
> meetings on Wednesdays (Fridays?) were proposed.  Dimitris said that 
> weekly meetings would be fine to gain momentum, and then the group 
> could fall back to bi-weekly meetings.
> Tim had proposed that we do threat modeling of the CA system with a 
> high-level view of the architecture—maybe have two architectures, one 
> for traditional and one for cloud and third-party data center 
> arrangements. Neil noted that if a root CA is supposed to be offline, 
> then having it cloud-based is virtually impossible. There was general 
> agreement that we were really talking about third-party data center 
> arrangements, however, Tim said that portions of a CA system could be 
> cloud-based.  He said that when doing a threat modeling exercise, you 
> have to have an adequate description of the system, but when we check 
> with CABF members, we’ll likely find that they are some operating in a 
> corporate data center where others are operating in someone else’s 
> data center, and the properties are somewhat different.  There was 
> discussion of the two types of environments, and it was agreed that we 
> need to come up with a model that works for both corporate data 
> centers and collocated facilities.  Dimitris said that they would be 
> proceeding with a traditional model first.  Dimitris said at the end 
> of the exercise, we’d need to map the current network requirements and 
> see how they fit into this architecture.  Ben wondered whether  some 
> other group has written up / documented what the CA environment is, so 
> that we don’t have to re-create the wheel?  Dimitris said it isn’t as 
> important how we sketch it out, at the end of the day we’ll be 
> discussing the same problems, such as, how do you transfer data, 
> update operating systems/software, etc., and that physical security is 
> probably the easier part.  Neil said the main issue for him has always 
> been, how do you know the state that the system is in when you are 
> patching, or whatever.  How do you know that what you did to the 
> system had the desired effect?  How do you audit that? Do you have 
> vulnerability scanning for a system that is completely offline?  That 
> is unlikely, etc.
> The group then prioritized the list of work items – green (easy to 
> work on), yellow (moderate difficulty), and red (difficult), as follows:
>  1. Defining "Root CA System", "Offline" and "Air-Gapped" and
>     clarifying associated requirements
>  2. Defining terms like "workstation", "account", "zone", "CA System,"
>     and "Issuing System" (easy)
>  3. Clarifying log review, "human review" of logs vs. automated
>     reviews (moderate)
>  4. Defining "Critical Vulnerability" and "Critical Security Event"
>     and clarifying actions to take and clarifying action to take
>     within 96 hours of detecting a vulnerability not otherwise
>     addressed by CA's procedures (difficult)
>  5. Providing guidance on the criteria for acceptable penetration
>     tests and vulnerability scans (difficult)
>  6. Including mitigating factors and compensating controls in the
>     NCSSR (difficult)
>  7. Penetration tests after changes the CA determines are
>     "significant" (moderate)
>  8. Clarifying audit documentation requirements for network/system
>     configurations (1.f, g, and h) (moderate)
>  9. Addressing software development vulnerabilities and processes
>     (difficult)
> 10. Modifying 2.j. "review all system account configurations every 90
>     days" (easy)
> 11. Addressing wireless security vulnerabilities (moderate)
> 12. Timeframes in which to disable system access of former employees
>     (currently within 24 hours) (easy)
> 13. Password rules (currently 12 characters, OR 8 characters + changes
>     every 90 days, OR a documented policy) (moderate).
> Ben noted that we could talk about 2., ("workstation", "account", 
> "zone", "CA System," and "Issuing System”), but that  it likely falls 
> within the architectural/threat modeling.  It was agreed that this 
> issue would fit in within the work of that subgroup.
> Ryan suggested we talk about passwords today, 2.g.  There were lots of 
> opinions about the quality of passwords required, 8 characters being 
> insufficient, how the password provision applies/doesn’t apply to 
> other authentication mechanisms, etc.  Ryan suggested we look at 
> anti-hammering mechanisms, lockouts, etc.  Dimitris noted that the 
> Network Security Requirements already mention lockouts (2g and 2k).  
> Ryan noted that Windows login and TPMs have these mechanisms to slow 
> down failed login attempts.  He noted that these can cause denial of 
> service, which is OK in a local system, but might not be OK as 
> mechanisms with a remote system. Ryan suggested that we provide a lot 
> of examples, rather than be overly specific so that people can choose 
> better solutions. Ben asked whether this meant that we should provide 
> more guidance and fewer requirements.  Ryan said that there has to be 
> more flexibility in which mechanisms are used.
> Ben noted that discussions of passwords might take a lot of time, and 
> maybe we should break this discussion off into a subgroup.  Ryan 
> suggested that for topics like passwords, subgroups could come back to 
> the group with recommendations.  Tim said a useful piece of homework 
> for passwords would be for people to read section 5.1.1 of NIST 
> 800-63b (https://pages.nist.gov/800-63-3/sp800-63b.html). Volunteers 
> for the subgroup included Ryan, Ben, Tim, Robin and Fotis.
> The group turned its attention to audit logging and manual log 
> review.  Sections 3.b to 3.e. were reviewed.  Ryan and Ben noted that 
> these sections could be reworded so that provisions in 3.c. would 
> encompass parts of 3.e. (the responsibility for making sure things are 
> functioning correctly).   Logging can stop functioning for a variety 
> of reasons, e.g. disk failure, and it’s important to have processes in 
> place to catch that, but the human review, when auditors have 
> interpreted this, they have taken it to mean human review of the 
> actual log with an eye to finding anomalies.  It’s not realistic for 
> humans to find patterns in the data.  So it’s one thing organizations 
> do, but not because it adds value.  You need systems in place to 
> identify patterns, as stated in subsection c., but you don’t want to 
> have humans doing that.
> Tobi asked whether the design of subsection e. might have been to 
> catch things like classes of messages that are not being forwarded to 
> your logging architecture. Ryan said you could have periodic reviews 
> of the design, and if that’s the intent, then the requirement should 
> be that you have yearly reviews of your logging strategies to ensure 
> they are capturing the right things vs. a monthly review of logs. What 
> ends up happening is the new guy is assigned the task of doing manual 
> log reviews, which provides no value.  Tobi said that he interprets e. 
> to mean that he could glance over the log to see that it is operating 
> properly and could spot anomalies.  Ryan said that for Let’s Encrypt, 
> with millions of log entries daily, you’re never going to see it.  
> Tobi said that he wouldn’t expect to see a single one, but if there is 
> a whole class of warnings he would definitely notice them.  That was 
> countered with arguments that anomalies would be buried in systems 
> where hundreds of subsystems are logging.
> Ryan said that he thought there ought to be someplace in the 
> requirements where we address these issues, but that he didn’t think a 
> manual review of an at-scale system logs is valuable.  There should be 
> a requirement for automation that captures security-sensitive events.
> Ben said that e. is really two requirements.  One requirement is that 
> the system has integrity and the other requirement is to have some 
> human review of the log (with the use of an in-house or third-party 
> audit log reduction and analysis tool), and maybe we should split them 
> up into e. and a new subsection f.   One way to edit e. would be to 
> remove language so that it would read, “Ensure that application and 
> system logs have integrity and are operating properly.”  Then f. could 
> read, “Conduct a human review of logs once a month using an in-house 
> or third-party audit log reduction and analysis tool.”  However, he 
> said he didn’t know whether the latter, human review, was necessary. 
> We want to make this easy, practical and realistic.  If we think that 
> this is covered in the previous subsections a-d, we could make that 
> edit and just move on.
> Dimitris said his interpretation of subsection e. is that you just 
> have to make sure your systems are logging. It doesn’t say anything 
> more about drilling in and trying to find if there are any security 
> alerts hidden in the logs.  You just need to check once a month that 
> all of your critical systems are actually logging, and you can 
> automate this process.  Tobi said that you can obviously tell if 
> something is not working.  Dimitris said it doesn’t say you have to 
> find attacks or any weird activity, which is described under 
> subsection c.
> Ben said that Dimitris’ reading of e. is the logical conclusion, but 
> then e. has stuff about human review and log reduction analysis tools, 
> which confuse the interpretation.  As the drafter of these 
> requirements, he knows that there was an intent to require human 
> review of logs using automated tools, but that he isn’t arguing that 
> it was the right thing to do, especially when it is causing this 
> confusion. By making Ben’s suggested changes, it would ensure that 
> Dimitris’ interpretation is carried forward—that the system has 
> integrity and is operating properly.  Ben then said that if we wanted 
> to, we could go on and talk about human review of an audit log using 
> analytical tools, which is an extra step that is a lot of work.  Tobi 
> said he didn’t think that anyone was expecting anyone to sit down and 
> go through massive amounts of log entries—that makes no sense.
> Ben asked whether we add in a new f. a monthly review or do we make 
> the assumption that if you  have continuous monitoring, etc., in b. 
> and c. that you have already covered what would be provided by a 
> monthly review? Dimitris said he thought we have covered those under 
> b. and c., and they are already mandatory.  There was a question as to 
> whether we should define what “integrity” means?  Tobi said that 
> integrity means that you are getting what you think you are getting.  
> It was then noted that CAs have been asked to hash logs, sign logs, 
> stamp logs, etc.  Ryan said he didn’t interpret integrity as Tobi did 
> but that integrity means that it has not been modified since it was 
> put there, which is different than what you put there is what you 
> expected you put there.  The word “integrity” was highlighted and it 
> was decided that we would pick up again when we reconvened talking 
> about the meaning of integrity.
> Meeting adjourned.
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