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How to find the AWS account ID of any S3 bucket

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Re: How to find the AWS account ID of any S3 bucket

#41

> The ability to apply a wildcard match on the s3:ResourceAccount condition key That’s the crazy part. No good can ever come from this - there is no legitimate reason why you would grant or deny permission based on a partial account id match.

That's the part that surprised me as well; it doesn't seem like a field that should be eligible for anything other than an exact match. I am unable to conceive of a use case for pattern matching account IDs.

Re: How to find the AWS account ID of any S3 bucket

#43
post #14
post #8

Earlier quoted context omitted.

AWS Account IDs are not secret and don’t need to be. AWS doesn’t design anything that assumes your account ID is secret, and you shouldn’t either.

I've gotten in long arguments with senior IT people who refuse to believe this even when they talk to AWS directly about it.

I guess anything that looks like random letters/numbers is going to be considered a secret to some people. If it wasn't meant to be secret, it would be human readable. Or some such nonsense.

Re: How to find the AWS account ID of any S3 bucket

#46

Earlier quoted context omitted.

It’s not defense in depth to build your security model off of false assumptions, it’s just bad security.

I don't understand your reasoning. Neither my name nor where I live nor my phone number nor my license plate are secrets. Yet I don't go around wearing a t-shirt with my personally identifying information printed on it. What am I missing?

If you knew that there was an assassin out there trying to find you and cause you harm, would you consider “I don’t wear a t-shirt with my address on it” to be any form of protection against that assassin?

If you want protection against that, you need to focus on better home security, hiring bodyguards, going to the police etc, and you’re better off assuming that the assassin will find your address regardless of whether or not you wear a t-shirt with it printed on.

Put another way: there’s a difference between “I don’t do this thing” and “I rely on not doing this thing for my safety”. The second one makes a lot more assumptions than the first one does, and those assumptions can lead to problems if they are false assumptions.

Re: How to find the AWS account ID of any S3 bucket

#48

Earlier quoted context omitted.

It’s not defense in depth to build your security model off of false assumptions, it’s just bad security.

I don't understand your reasoning. Neither my name nor where I live nor my phone number nor my license plate are secrets. Yet I don't go around wearing a t-shirt with my personally identifying information printed on it. What am I missing?

If you place any sort of security assumptions on AWS account IDs into your threat model, you're effectively directly introducing a security vulnerability. If you're not then why include it into your security threat model to begin with? I believe that is their point.

Since AWS does not, and has never, treated that information as secret, then there is absolutely no reason to consider it sensitive because there is no security guarantees with how AWS handles those IDs (as this article demonstrates).

Thus, either you're including them into your threat model as sensitive and thus immediately opening up yourself to vulnerabilities (bad security), or you're not including them at all (and thus not treating them as sensitive/secret/whatever). The argument the parent had (and that I agree with) is that you should do the latter unless AWS provides a means to work with those IDs securely (it won't because they're not secrets).

Re: How to find the AWS account ID of any S3 bucket

#50

Earlier quoted context omitted.

You've said "this is wrong" and then repeated exactly my point back to me. I suspect some misunderstanding has occurred here. We are agreeing on this--you need to follow AWS's lead and design your cloud deployment such that the account ID doesn't leak anything interesting about your business. That's a direct quote from my original post. I further gave an example--if you're a design firm using a single account for dif…

I think we agree, but either your meaning or your words are giving me pause. > you can treat your account ID as non-secret because AWS does. That doesn't directly follow; It does follow, and not only that, but not only “can” you treat them as non-secret, you _must_ treat them as non-secret. > the difference between AWS's point of view and your company's point of view means there are things you might care about that A…

Correlation of bucket ownership isn't a security issue at all. I never used that word in my posts, and the author of this article also never suggested that it was. That's the point--there are other considerations that AWS does not care about, but your business does. Your cloud deployment needs to be designed such that the account IDs do not leak information that your business doesn't want to be revealed. You don't get the non-secretness for "free"--you have to think about it and be careful on how you isolate things into accounts. As far as I can tell, we agree on all of this and have just suffered some misunderstanding in this thread.
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