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Yahoo discloses hack of 1B accounts

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Re: Yahoo discloses hack of 1B accounts

#401

Post by timdeneau »

NoPiece wrote: post #9
harigov wrote: post #3

I hope they stopped depending upon those security questions if that is part of the leak. On a side note, this seems like a great time to be an abuser. One can collect so much information about users - they may actually have more data than any govt in the world.

I hope everyone stops relying on security questions!

Side note: if your Apple account security questions are gibberish, your account now gets stuck in an infinite reset loop. I need to answer the security questions to reset my security questions or to reset my password. This occurs even if you have the current valid password, the questions are mandatory for all changes. The questions are also mandatory for phone support, so I’m locked out of my account even though I have the password. Great job everybody.

Re: Yahoo discloses hack of 1B accounts

#402

Post by leereeves »

danielweber wrote: post #359
leereeves wrote: post #226

Earlier quoted context omitted.

> hash = sha512(salt + MD5(password)) Passing the password through MD5 reduces the complexity to 128 bits, you can't get that back. So the security level is not the same, though it may be resistant to some attacks on MD5. And it's probably not important for most people, since there are less than 2^56 eight character ASCII passwords.

> Passing the password through MD5 reduces the complexity to 128 bits No, this is not the problem with MD5. You are not going to find two user-memorizeable-and-typeable passwords with an MD5 collision. If you are bringing a password with more than 128 bits of complexity to the party, any password storage scheme better than plaintext will have your password safe .

For passwords, there is no known problem with MD5, unless you know about a preimage attack.

Collisions are a problem for digital signatures, not for passwords.

But some people do want and use more than 2^128 bit passwords, for whatever reason, and an MD5 intermediate stage limits that.

Re: Yahoo discloses hack of 1B accounts

#403

Post by XorNot »

cookiecaper wrote: post #328
drodgers wrote: post #315

Earlier quoted context omitted.

If the password is stored properly, (i.e. bcrypt) then there does need to be some length limit or it becomes too easy to DoS a service by sending it hundreds of megabytes of password to bcrypt. There's no reason for that length limit to be less than 100 characters though.

Yep, people who've run marginally popular sites have dealt with this before. Give someone a text box and watch them try to stuff 4GB of content in it. There has to be a cutoff somewhere, but as you note, it should be well outside of the realm of reasonable password lengths (hundreds of characters).

Hash the password locally (you are serving JavaScript over SSL right?) and only send the SHA256.

Re: Yahoo discloses hack of 1B accounts

#404

Post by normaljoe »

jsjohnst wrote: post #260
mturmon wrote: post #247

Earlier quoted context omitted.

Yet, somehow they did get out.

Apologies, I've heard the details at this point and I can't disclose them. The limit of what I can do is poke holes in the theories that are wrong.

I am taking a WAG here but if they got code then they might be able to take educated guesses at the UDB values without actual access to UDB. Those guesses are more likely to be true with bot registered accounts where there is duplication of information.

This goes back to my theory that a good portion where junk accounts.

Not saying this is acceptable, just saying garbage in garbage out.

Re: Yahoo discloses hack of 1B accounts

#405

Post by jsjohnst »

geekone wrote: post #392
jsjohnst wrote: post #379

Earlier quoted context omitted.

"Dishonest", not in the slightest. From what I'm told, they really don't know how they got in. But that's only the part of the story discussed in the press release, what's not discussed is how the data existed in that format.

If they do not know how the adversaries got in, how do they know the adversaries are not still in to some degree?

Good point. I don't know if they do know that for sure.

Re: Yahoo discloses hack of 1B accounts

#406

Post by jsjohnst »

bazzargh wrote: post #400
yuhong wrote: post #391

Earlier quoted context omitted.

bcrypt(md5(password)) allow the existing password hash to be reused.

No. They've stolen the hash, so if they crack it, you've just let them waltz back in. The correct response is force a password reset, and _delete_ weak hashes so that they cannot be stolen in a subsequent breach. At worst, store a bcrypted md5 password as you suggest, but only as a check for a password the user must not be allowed to use again; it _cannot_ be used to sign them in. One of the attacks you're preventing…

When they did the bcrypt(md5(password)) there was no leaks of Yahoo!'s md5'd passwords. That's obviously changed now and thus why the billion passwords were invalidated (I'm one of those folks btw, but I also had TFA on my account and my password had sufficient entropy you won't brute force the md5).

Re: Yahoo discloses hack of 1B accounts

#407

Post by jsjohnst »

normaljoe wrote: post #387
jsjohnst wrote: post #31

Earlier quoted context omitted.

1) As Yahoo "upgraded" all password storage in UDB (where all login / registration details are stored) to be bcrypt before 2013, I'm curious how this was possible. 2) Yahoo doesn't use a centralized session storage. If you know a few values (not disclosing the exact ones) from the UDB, it's theoretically (guess not so theoretical now) possible to create forged cookies if you steal the signing keys. To my knowledge, t…

I'm guessing by your handle I know who you are :). Ex-Yahoo super chat moderating guy here, which should let you know me. Wouldn't the upgrade require the accounts to actually login to migrate password? Last I was at Yahoo there was at least 3B junk accounts in UDB. With out knowing details I am guessing that many of the "compromised" accounts fall into that bucket. I get that membership can't just trash junk account…

Just to confirm, purple Yahoo! car in YEF spot ;)

As to your question, no, they didn't need to login due to how the hash "upgrade" was done (unlike how Tumblr did it around the same time). I was one of the people in the billion accounts and I definitely have logged in and also changed my password multiple times (also have very high entropy passwords and use TFA).

Re: Yahoo discloses hack of 1B accounts

#408

Post by pugz »

eric_h wrote: post #303
Endy wrote: post #244

Earlier quoted context omitted.

I don't download my email. I have a webmail for a reason - I don't want a mail client with all its attendant files gumming up my PC. I moved off Netscape Communicator to webmail because it took up over 40% of my drive, and I've never regretted the decision. And I don't like 2FA either. It's a hassle and never, ever, worth my time or energy. There was one gaming service (I think it was an MMO) that demanded 2FA or bus…

> I don't like 2FA either That seems to be a rather dangerous position to hold these days. I personally dislike that googles 2FA is SMS based (unless there's a way to use e.g. Authy with it that I'm unaware of), but still seems that the only way to be reasonably safe is a strong password and 2FA. I'll add that The authy app on the Apple Watch has made 2FA for services that support it rather painless.

I use 1Password as my 2FA app for Google services. I only set it up relatively recently so maybe support for non-SMS is new. Or region-based?

Re: Yahoo discloses hack of 1B accounts

#409

Post by jsjohnst »

normaljoe wrote: post #404
jsjohnst wrote: post #260

Earlier quoted context omitted.

Apologies, I've heard the details at this point and I can't disclose them. The limit of what I can do is poke holes in the theories that are wrong.

I am taking a WAG here but if they got code then they might be able to take educated guesses at the UDB values without actual access to UDB. Those guesses are more likely to be true with bot registered accounts where there is duplication of information. This goes back to my theory that a good portion where junk accounts. Not saying this is acceptable, just saying garbage in garbage out.

You can't guess the XX (anonymized for obvious reasons) key without access to the UDB.

Re: Yahoo discloses hack of 1B accounts

#410

Post by normaljoe »

camus2 wrote: post #20
kuschku wrote: post #12

Earlier quoted context omitted.

[deleted]

> Sure, SHA1, scrypt or bcrypt with salt were already common back then, but it's an entirely different story than if they had used it today. Not an excuse, this is Yahoo, not a PHP shop in India doing some low budget contracting.They should have a top of the line security team enforcing the most recent secure practices. Furthermore I got no email from Yahoo telling me that my account may have been hacked. Both incomp…

> Furthermore I got no email from Yahoo telling me that my account may have been hacked

Then your account was most likely not on the list of accounts compromised.

> By the way I did some PHP dev back in 2011

Well Yahoo is a tad bit older then that, by about 17 years. This is not an excuse, but really comparing your 2011 coding to 1994.... Go ahead and boot up your old 486. I'll get back to you when this page loads up in an hour. :)

Yahoo's code base is old and huge, like billions of lines huge. Yahoo's engineers have modernized it at a massively rapid pace. I'm not sure of current state, but when I left Yahoo finance was written in something like 10 languages including serving pages in C, cause that's all they had back then.

Current tech is NodeJSish and others. They have their own hardened versions. But still migrating millions of lines of C to something other then C isn't a walk in the park.

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