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I've been thinking about this in regard to AWS. The encryption at rest for most things is completely transparent so the only thing your really protected against

I've been thinking about this in regard to AWS. The encryption at rest for most things is completely transparent so the only thing your really protected against is someone walking into a data center and grabbing your drive somehow. Or improperly disposed drives. Maybe some kind of hypervisor or SAN exploit but I don't know much about that. AWS seems to have turned part of the cloud operating model they are supposed to be responsible for back onto the user and no one questions it.

WrtCdEvrydy 6y ago
Sorry, here's your cloud fees back.
- ape4 6y ago
  Self hosting (remember that) seems best for really confidential things.
  - ENOTTY 6y ago
    Self hosting is no longer realistic because all the data you actually want to compute on is now in the cloud. The egress costs of that data into your self hosted environment would destroy you. Imagine a world where the cloud produces more data at a rate that exceeds the pipes leaving the cloud. You are quite literally locked into computing within that same cloud.
    - roynasser 6y ago
      Its very realistic! Its being done at this moment! (amazing, isnt it?) lfmao... but jokes aside, the "cloud" is just series of datacenters with less choice of a brand, you do realize this? There is no such "cloud" as you say... Internet allows exactly for decentralized data (among cloud-1a-b1-c2 to cloud-2b-5x-3h is not all "in the cloud", its the same as datacenterA to datacenterB.... proximity still has an effect, as do all other network conditions...) Dont let the marketing sandcastle trap you in!
  - londons_explore 6y ago
    Except Google has a much much bigger budget for security engineers than you have...
    - thu2111 6y ago
      In this threat model that's a downside, not an upside. SEV is not, to me, a convincing security model. It was tried a long time ago, it doesn't work. SGX uses small enclaves for a reason. Hacking your average Linux box is quite easy already, which is why compromised passwords flow like water. With the SEV threat model the cloud provider is no longer on your side. They are no longer defending you against threats, they are a threat. That's why you want encrypted RAM. But you're being threatened by one of the world's most advanced security organisations, a company that literally pays a large team to do nothing but locate zero day exploits all day, every day. And they swap zero days with other major tech firms too. So they have access to bugs in your OS before you do, and this is structural, there's no fix for it. Worse, they recommend you use Google-controlled, 'hardened' OS images. But that makes no sense because you're trying to defend yourself against Google. Finally, it's very unclear to me that the Linux kernel is going to accept bug reports of the form "the hardware behaved in arbitrary incorrect ways because it was redefined by a malicious hypervisor on the fly". The kernel isn't designed to deal with a malicious hypervisor. It's not going to be checking the results of things that might be hypercalls to check the hypervisor didn't hand back invalid results. In the past this has caused big problems with userspace apps trying to run on malicious kernels: the kernel was able to break in to the encrypted memory space immediately because the kernel could manipulate syscall returns in ways the app didn't expect. But let's put OS hacking to one side. SEV has a very poor track record of security. There were dozens of bugs in their firmware in past revisions, ordinary C type buffer overflows. Then there were basic crypto bugs: you could send the firmware an invalid point on the elliptic curve and it wasn't checking for that, things like this. Perhaps Google has audited AMD's firmware now and have knocked out all these problems. Perhaps not. Who knows - they mention working with AMD on performance but not security. Moreover, SEV doesn't have anything to say on the topic of side channel attacks. And unlike with SGX, because the whole point of SEV is you use existing software and operating systems, there's also no fix for this problem. Normal kernels and apps aren't designed to resist a compromised hypervisor. SGX enclaves are designed for-purpose so you can argue that they're the smallest piece of app logic that needs to process your data and you can go to town on securing it, whilst the bulk of the app handling resource management, connections, scheduling, etc, is blinded by cryptography. Enclaves expect the host to attack them because they were written that way. They can do things in a less efficient but more side-channel proof way. With SEV this is theoretically an option (could run some specially written hardened OS), but, it's not how it's being advertised so nobody will do it.
  - DCKing 6y ago
    Self hosting is only best if you want maximum control. But most people can't handle that imagined level of control in reality, at least not on the same level as a major cloud platform. AWS (or GCP or Azure) infrastructure is overwhelmingly more likely to be able to do security better from a maintenance, intrusion handling or physical security perspective than any single organization can do, especially organizations smaller than AWS. The tradeoff is that despite how much AWS can claim to not touch your data, and all the feature, contract and compliance documentation they have to show for it, you can never be sure they're not touching it (deliberately or by accident). Self hosting is not about confidentiality. For nearly all categories of "confidential data", I would much much rather have it in a major cloud platform than running in some closet somewhere or in some random colocation center somewhere, all other circumstances being equal. Self hosting is about how much you want to be in control, regardless of your capabilities to actually be in control.
    - znpy 6y ago
      > Self hosting is only best if you want maximum control. Not necessarily. Beyond a certain scale you can go build your own datacenter (or smaller: rent a whole rack cabinet in a datacenter) and start exploiting economics of scale. A lot of people don't realize that nowadays you can pack tens of cores and literally terabytes of ram in a 2u server.
      - gzu 6y ago
        That's what I don't quite understand about the current state of cloud computing. We're seeing huge advances in hardware/network technologies this decade but there's an ever increasing push to centralize hosting with cloud providers. Will this ever swing the other way?
        ape4 6y ago
        Yeah especially if your company has more than one location - for redunancy
        acdha 6y ago
        Look at what's driving the shift: data centers are a major capital investment up-front plus a significant amount of staffing to operate and secure them. If you have enough proven need to justify that, you can easily beat a cloud provider — especially if you can simplify the problem in some ways that a generic service cannot. For most organizations, however, it's hard to justify investing millions of dollars up-front in the hope that at some point you'll be saving enough to make that pay off. If that's not your core business it's often easier and safer to outsource it so, for example, you don't end up with a data center full of 50% utilized hardware which you bought to have capacity for growth which wasn't quite what you expected — or a big crunch when you have more demand than capacity and now need to double that investment to handle [currently] 10% of your usage.
gtsteve 6y ago
There are other use-cases. For example, you can crypto-shred an unlimited amount of data just by deleting the key associated with it. You can also set up workflows such as your client owning the encryption key that encrypts data held by you and they can revoke it at any time. Slack has a similar system and I was asked by a large financial institution about the same. I expect to see this more in future.
- aj3 6y ago
  > For example, you can crypto-shred an unlimited amount of data just by deleting the key associated with it. Sounds like a great target for ransomware crews!
  - gtsteve 6y ago
    Yes indeed! But you mark the key for deletion and there's a minimum time of 7 days before it is deleted and during that time you can't use it. You've got quite a while to realise there's a problem and fix it.
    - aj3 6y ago
      This sounds reasonable.
    - toomuchtodo 6y ago
      How many critical domains and TLS certs expire with many months of notice? In a proper shop, someone will be alerted. Most places are not on the ball, and that alert is going to go entirely unnoticed.
      - gtsteve 6y ago
        You'll probably notice your disks not mounting and your vms not starting up and your users not being able to take data etc. Or not, depends on how frequently accessed it is. We'd definitely notice.
acdha 6y ago
AWS encryption at rest comes in two flavors: their managed keys protect against the threat you managed (which is still important for some compliance targets) but if you use customer-managed keys you can go further and protect against compromises in your accounts - server A only has access to encrypt, server B can only decrypt, role C in account D can encrypt data before transferring it, even the account root user can’t update the policy to break that, etc. It’s considerably more work but also more benefit.
- aj3 6y ago
  Not sure what benefits are there in scheme you described. Which threat exactly is mitigated by using this tech?
  - acdha 6y ago
    Simple example: say I use S3 with the Amazon-managed key. Anyone who has a policy granting access to a bucket — and lots of people love to write bucket policies with Resource:* — can read or write objects in that bucket using that key. If you use a CMK, you can write custom policies which are both far more restrictive and shouldn't change as much as other resource types. That means that I could, say, have a policy which says the key-admin role/group/user is the only principal in the account which can update the key settings at all (even administrator can't do that then), the writer role is the only one with kms:Encrypt, and the reader role is the only one with kms:Decrypt. No matter what S3 access you have, if you aren't one of those roles you won't be able to use the encrypted data. This is probably also in a scenario something like “central group A provisions the KMS, devops group B creates lots of other resources using that key”. You can add conditions, too — “anyone in our account can encrypt, decrypt requests can only come from this IP address or VPC”, “only requests from this AWS service are accepted” (i.e. that compromised EC2 instance can't use it), “access to data encrypted with this key can only be done in the two regions we approve of that”, “this particular encryption value must be used on all requests”, etc. https://docs.aws.amazon.com/kms/latest/developerguide/key-policies.html#key-policy-example https://docs.aws.amazon.com/kms/latest/developerguide/key-po... https://docs.aws.amazon.com/kms/latest/developerguide/policy-conditions.html https://docs.aws.amazon.com/kms/latest/developerguide/policy... That adds an extra layer of defense: if I compromise a user, even one with some level of administrative access, who doesn't have the CMK access all I can get are errors or encrypted data rather than the raw data. If you're careful you can architect environments where a person can deploy code without direct access to secrets or a system can stream data through to an encrypted store (if you are storing PII, this can be a huge difference between “all of our users” and “only the ones who used the system during this time period”). In some cases these can be bypassed (i.e. a CMK might not allow Administrator to access it directly but they could possibly issue credentials for a user who does have access) but you're preventing generic attacks which just scrape up everything that compromised credentials have access to, and hopefully increasing both the level access required and the likelihood of producing an audit alert.

WrtCdEvrydy 6y ago

Sorry, here's your cloud fees back.

ape4 6y ago
Self hosting (remember that) seems best for really confidential things.
- ENOTTY 6y ago
  Self hosting is no longer realistic because all the data you actually want to compute on is now in the cloud. The egress costs of that data into your self hosted environment would destroy you. Imagine a world where the cloud produces more data at a rate that exceeds the pipes leaving the cloud. You are quite literally locked into computing within that same cloud.
  - roynasser 6y ago
    Its very realistic! Its being done at this moment! (amazing, isnt it?) lfmao... but jokes aside, the "cloud" is just series of datacenters with less choice of a brand, you do realize this? There is no such "cloud" as you say... Internet allows exactly for decentralized data (among cloud-1a-b1-c2 to cloud-2b-5x-3h is not all "in the cloud", its the same as datacenterA to datacenterB.... proximity still has an effect, as do all other network conditions...) Dont let the marketing sandcastle trap you in!
- londons_explore 6y ago
  Except Google has a much much bigger budget for security engineers than you have...
  - thu2111 6y ago
    In this threat model that's a downside, not an upside. SEV is not, to me, a convincing security model. It was tried a long time ago, it doesn't work. SGX uses small enclaves for a reason. Hacking your average Linux box is quite easy already, which is why compromised passwords flow like water. With the SEV threat model the cloud provider is no longer on your side. They are no longer defending you against threats, they are a threat. That's why you want encrypted RAM. But you're being threatened by one of the world's most advanced security organisations, a company that literally pays a large team to do nothing but locate zero day exploits all day, every day. And they swap zero days with other major tech firms too. So they have access to bugs in your OS before you do, and this is structural, there's no fix for it. Worse, they recommend you use Google-controlled, 'hardened' OS images. But that makes no sense because you're trying to defend yourself against Google. Finally, it's very unclear to me that the Linux kernel is going to accept bug reports of the form "the hardware behaved in arbitrary incorrect ways because it was redefined by a malicious hypervisor on the fly". The kernel isn't designed to deal with a malicious hypervisor. It's not going to be checking the results of things that might be hypercalls to check the hypervisor didn't hand back invalid results. In the past this has caused big problems with userspace apps trying to run on malicious kernels: the kernel was able to break in to the encrypted memory space immediately because the kernel could manipulate syscall returns in ways the app didn't expect. But let's put OS hacking to one side. SEV has a very poor track record of security. There were dozens of bugs in their firmware in past revisions, ordinary C type buffer overflows. Then there were basic crypto bugs: you could send the firmware an invalid point on the elliptic curve and it wasn't checking for that, things like this. Perhaps Google has audited AMD's firmware now and have knocked out all these problems. Perhaps not. Who knows - they mention working with AMD on performance but not security. Moreover, SEV doesn't have anything to say on the topic of side channel attacks. And unlike with SGX, because the whole point of SEV is you use existing software and operating systems, there's also no fix for this problem. Normal kernels and apps aren't designed to resist a compromised hypervisor. SGX enclaves are designed for-purpose so you can argue that they're the smallest piece of app logic that needs to process your data and you can go to town on securing it, whilst the bulk of the app handling resource management, connections, scheduling, etc, is blinded by cryptography. Enclaves expect the host to attack them because they were written that way. They can do things in a less efficient but more side-channel proof way. With SEV this is theoretically an option (could run some specially written hardened OS), but, it's not how it's being advertised so nobody will do it.
- DCKing 6y ago
  Self hosting is only best if you want maximum control. But most people can't handle that imagined level of control in reality, at least not on the same level as a major cloud platform. AWS (or GCP or Azure) infrastructure is overwhelmingly more likely to be able to do security better from a maintenance, intrusion handling or physical security perspective than any single organization can do, especially organizations smaller than AWS. The tradeoff is that despite how much AWS can claim to not touch your data, and all the feature, contract and compliance documentation they have to show for it, you can never be sure they're not touching it (deliberately or by accident). Self hosting is not about confidentiality. For nearly all categories of "confidential data", I would much much rather have it in a major cloud platform than running in some closet somewhere or in some random colocation center somewhere, all other circumstances being equal. Self hosting is about how much you want to be in control, regardless of your capabilities to actually be in control.
  - znpy 6y ago
    > Self hosting is only best if you want maximum control. Not necessarily. Beyond a certain scale you can go build your own datacenter (or smaller: rent a whole rack cabinet in a datacenter) and start exploiting economics of scale. A lot of people don't realize that nowadays you can pack tens of cores and literally terabytes of ram in a 2u server.
    - gzu 6y ago
      That's what I don't quite understand about the current state of cloud computing. We're seeing huge advances in hardware/network technologies this decade but there's an ever increasing push to centralize hosting with cloud providers. Will this ever swing the other way?
      - ape4 6y ago
        Yeah especially if your company has more than one location - for redunancy
      - acdha 6y ago
        Look at what's driving the shift: data centers are a major capital investment up-front plus a significant amount of staffing to operate and secure them. If you have enough proven need to justify that, you can easily beat a cloud provider — especially if you can simplify the problem in some ways that a generic service cannot. For most organizations, however, it's hard to justify investing millions of dollars up-front in the hope that at some point you'll be saving enough to make that pay off. If that's not your core business it's often easier and safer to outsource it so, for example, you don't end up with a data center full of 50% utilized hardware which you bought to have capacity for growth which wasn't quite what you expected — or a big crunch when you have more demand than capacity and now need to double that investment to handle [currently] 10% of your usage.

gtsteve 6y ago

There are other use-cases. For example, you can crypto-shred an unlimited amount of data just by deleting the key associated with it. You can also set up workflows such as your client owning the encryption key that encrypts data held by you and they can revoke it at any time. Slack has a similar system and I was asked by a large financial institution about the same. I expect to see this more in future.

aj3 6y ago
> For example, you can crypto-shred an unlimited amount of data just by deleting the key associated with it. Sounds like a great target for ransomware crews!
- gtsteve 6y ago
  Yes indeed! But you mark the key for deletion and there's a minimum time of 7 days before it is deleted and during that time you can't use it. You've got quite a while to realise there's a problem and fix it.
  - aj3 6y ago
    This sounds reasonable.
  - toomuchtodo 6y ago
    How many critical domains and TLS certs expire with many months of notice? In a proper shop, someone will be alerted. Most places are not on the ball, and that alert is going to go entirely unnoticed.
    - gtsteve 6y ago
      You'll probably notice your disks not mounting and your vms not starting up and your users not being able to take data etc. Or not, depends on how frequently accessed it is. We'd definitely notice.

acdha 6y ago

AWS encryption at rest comes in two flavors: their managed keys protect against the threat you managed (which is still important for some compliance targets) but if you use customer-managed keys you can go further and protect against compromises in your accounts - server A only has access to encrypt, server B can only decrypt, role C in account D can encrypt data before transferring it, even the account root user can’t update the policy to break that, etc. It’s considerably more work but also more benefit.

aj3 6y ago
Not sure what benefits are there in scheme you described. Which threat exactly is mitigated by using this tech?
- acdha 6y ago
  Simple example: say I use S3 with the Amazon-managed key. Anyone who has a policy granting access to a bucket — and lots of people love to write bucket policies with Resource:* — can read or write objects in that bucket using that key. If you use a CMK, you can write custom policies which are both far more restrictive and shouldn't change as much as other resource types. That means that I could, say, have a policy which says the key-admin role/group/user is the only principal in the account which can update the key settings at all (even administrator can't do that then), the writer role is the only one with kms:Encrypt, and the reader role is the only one with kms:Decrypt. No matter what S3 access you have, if you aren't one of those roles you won't be able to use the encrypted data. This is probably also in a scenario something like “central group A provisions the KMS, devops group B creates lots of other resources using that key”. You can add conditions, too — “anyone in our account can encrypt, decrypt requests can only come from this IP address or VPC”, “only requests from this AWS service are accepted” (i.e. that compromised EC2 instance can't use it), “access to data encrypted with this key can only be done in the two regions we approve of that”, “this particular encryption value must be used on all requests”, etc. https://docs.aws.amazon.com/kms/latest/developerguide/key-policies.html#key-policy-example https://docs.aws.amazon.com/kms/latest/developerguide/key-po... https://docs.aws.amazon.com/kms/latest/developerguide/policy-conditions.html https://docs.aws.amazon.com/kms/latest/developerguide/policy... That adds an extra layer of defense: if I compromise a user, even one with some level of administrative access, who doesn't have the CMK access all I can get are errors or encrypted data rather than the raw data. If you're careful you can architect environments where a person can deploy code without direct access to secrets or a system can stream data through to an encrypted store (if you are storing PII, this can be a huge difference between “all of our users” and “only the ones who used the system during this time period”). In some cases these can be bypassed (i.e. a CMK might not allow Administrator to access it directly but they could possibly issue credentials for a user who does have access) but you're preventing generic attacks which just scrape up everything that compromised credentials have access to, and hopefully increasing both the level access required and the likelihood of producing an audit alert.