Yahoo discloses hack of 1B accounts • Hacker News Board

Re: Yahoo discloses hack of 1B accounts

#391

Post by yuhong » Thu, Dec 15, 2016, 3:53 AM UTC

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…

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

Re: Yahoo discloses hack of 1B accounts

#392

Post by geekone » Thu, Dec 15, 2016, 3:54 AM UTC

jsjohnst wrote: post #379

mustacheemperor wrote: post #377

Earlier quoted context omitted.

The contrast between your statements and the press statement is great enough to imply Yahoo is being dishonest.

"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?

Re: Yahoo discloses hack of 1B accounts

#393

Post by Buge » Thu, Dec 15, 2016, 3:55 AM UTC

alyandon wrote: post #281

0x0 wrote: post #189

Earlier quoted context omitted.

Are you sure they actually logged in to your account to send spam (are the spam emails visible in your sent folder), or could it be that someone is just spoofing the SMTP MAIL FROM / email From: header?

As far as I can tell it wasn't someone spoofing my email address. Emails were sent to people on my contact list and the numerous bounce messages to contacts that no longer had valid email addresses confirmed the origin of the traffic.

It's possible that a contact of yours was compromised, and that contact had many contacts in common with you. And then they spoofed your address.

Re: Yahoo discloses hack of 1B accounts

#394

Post by Buge » Thu, Dec 15, 2016, 3:58 AM UTC

manarth wrote: post #170

agf wrote: post #91

Earlier quoted context omitted.

If it's a password so long and complex it wouldn't be in any rainbow table computable in reasonable time. While MD5 can be computed quickly, there is still a limit to how many you can compute -- and there are an infinite number of possible passwords if they aren't length limited.

Rainbow tables are attacks against secure algorithms. MD5 is recognised as an insecure algorithm: given a known hash, there are multiple possible passwords that would resolve to the same hash, therefore appearing to be the correct password. With MD5, it's not necessary to compute an infinite number of possible passwords, and it is possible that, given a particular hash, a collision can be found within a reasonable ti…

You are describing a first preimage attack. There have not been any computable first (or second) preimage attacks on md5.

https://stackoverflow.com/questions/822638/does-any-publishe...

There are collision attacks, but that is not relevant for password cracking.

Re: Yahoo discloses hack of 1B accounts

#395

Post by normaljoe » Thu, Dec 15, 2016, 4:01 AM UTC

jsjohnst wrote: post #379

mustacheemperor wrote: post #377

Earlier quoted context omitted.

The contrast between your statements and the press statement is great enough to imply Yahoo is being dishonest.

"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.

From my experience if Paranoids did know they would have locked it down at the expense of engineers or others. I know since I have made breaking changes to infrastructure which did lock out some engineers and cause plenty of headaches.

Every Yahoo I have ever known has cursed the Paranoids for getting and the way. Every Yahoo that has actually been in a situation has also blessed the Paranoids for the same reasons.

Simple fact is that Yahoo has a mega butt ton of code from several decades. There are going to be holes and when they are found they are fixed pretty damn quick. Last one I dealt with was solved in hours with all hand on deck. Sometimes it just sucks to be as old a Yahoo is.

Re: Yahoo discloses hack of 1B accounts

#396

Post by Buge » Thu, Dec 15, 2016, 4:01 AM UTC

JonDav wrote: post #130

ubercore wrote: post #79

Earlier quoted context omitted.

What do you mean by a password that can't be reasonably brute forced? EDIT: To clarify, I mean specifically with md5. I'm by no means an expert, just curious because I had considered md5 so broken that this comment caught my attention.

Pretty much even if you choose a high entropy password like say: `]{;& rQQQjoJkxm0ayM+gG,@vf*>#-{X4E>aZG(A1~tf the MD5 algorithm can be broken using various techniques like collisions, unsalted I believe means that their database would accept the hashes the third party has. End result is they should have migrated away from MD5 after it was declared unsafe.

No, a collision attack would not give you the plaintext from a hash. A first preimage attack would do that, but no computable first (or second) preimage attacks against md5 have been found.

https://stackoverflow.com/questions/822638/does-any-publishe...

Re: Yahoo discloses hack of 1B accounts

#397

Post by jsudhams » Thu, Dec 15, 2016, 4:01 AM UTC

zardeh wrote: post #325

eric_h wrote: post #303

Earlier quoted context omitted.

> 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.

Google also allows you to use google authenticator, but I don't believe they allow third party services.

Google does allow other apps (I think it is still same as GAuth) SASS pass and other authenticators with good. But yes they don't allow other token provides like Yubikey or RSA fobs

Re: Yahoo discloses hack of 1B accounts

#398

Post by normaljoe » Thu, Dec 15, 2016, 4:03 AM UTC

yuhong wrote: post #391

normaljoe wrote: post #387

Earlier quoted context omitted.

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…

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

Good point. Thanks for pointing out my mistake.

Re: Yahoo discloses hack of 1B accounts

#399

Post by Buge » Thu, Dec 15, 2016, 4:03 AM UTC

pluma wrote: post #83

scrollaway wrote: post #13

Earlier quoted context omitted.

It's really not. Unsalted MD5 has been shameful for a long, long time.

As a data point: when I was a teenage code monkey in 2004 writing PHP I already understood that unsalted MD5 is unsafe. According to Wikipedia: * 2004 it became possible to find MD5 collisions at a rate of one per hour on a cluster * 2005 it became possible to do this within "a few hours" on a consumer laptop * 2006 it became possible to do this within one minute * nowadays it's possible to do this "within seconds" P…

That website does not find collisions. It uses rainbow tables (or some other type of table) to crack passwords that it already knows.

Collisions are irrelevant for password cracking.

Re: Yahoo discloses hack of 1B accounts

#400

Post by bazzargh » Thu, Dec 15, 2016, 4:06 AM UTC

yuhong wrote: post #391

normaljoe wrote: post #387

Earlier quoted context omitted.

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…

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 is on _other_ sites, where the user has reused the passwords. Keeping around weak hashes even to let that user perform a reset is risking that hash being taken, cracked and used in a breach elsewhere.