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Why you shoud never use your favorite password on News.YCombinator.com

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Re: Why you shoud never use your favorite password on News.YCombinator.com

#61

Post by tptacek »

gojomo wrote: post #57
tptacek wrote: post #50

Earlier quoted context omitted.

No. Respectfully, you too have failed to think this through. Attackers with access to raw traffic can (and routinely do) change the traffic. Attackers will simply rewrite your hashing Javascript in transit.

That's an active attack. My statement was clear and correct. The number of people who can passively eavesdrop on traffic (eg, on open wifi) is much larger than those who can dynamically change traffic in transit.

There are no passive-only attackers. Attackers who can observe raw traffic can hijack it (if it's the '90s) or redirect it (if it's 5 years ago, and in Brazil, and money is involved --- just to make it specific).

Look, we're locked in an Internet message board death struggle and neither of us are going to concede anything, so let me just finish with this tangent:

If you tried to sell an app to a Fortune 1000 company that defended against passive-only attackers but left logins open to active attackers, and they contracted out a 1 week 1 person web pen test to make sure your app was safe for peripheral customer data to go inside, you'd get dinged for this and you'd cut a dot release.

If, instead of cutting a dot release you explained why it was worth them moving ahead with a pilot that defended against passive attackers, you would Lose The Sale. Seen it happen.

I don't much care about your Hacker News password, but lots of you write applications, and I've seen some of the most unlikely (message boards, bug trackers, blogs---err, content managers) wind up in security audit hell. My advice, take it or leave it: don't bother with these Javascript hash schemes.

Re: Why you shoud never use your favorite password on News.YCombinator.com

#62

Post by mattmaroon »

mhartl wrote: post #33
axod wrote: post #13

1. Go read up on HTTP vs HTTPS 2. Never use the same login for 2 websites The fact this has been upvoted to top position is more worrying than any security worries.

Never use the same login for 2 websites Dude, my brain would explode.

How about, never use the same login on 2 websites you care about?

I use the same pwd on about 100 sites, none of which I would really be upset about if it got stolen.

Re: Why you shoud never use your favorite password on News.YCombinator.com

#63

Post by tptacek »

cperciva wrote: post #60
tptacek wrote: post #51

Earlier quoted context omitted.

Message digest functions are not, generally, number-theoretic.

How is this relevant? The question of P ?= NP isn't limited to number-theoretic functions -- if P = NP then it is possible to find a preimage to any (polynomial time) hash function in polynomial time.

You're right.

Re: Why you shoud never use your favorite password on News.YCombinator.com

#64

Post by jncraton »

tptacek wrote: post #54
Hexstream wrote: post #27

Earlier quoted context omitted.

Here's how I understand it: The salt is generated on the server, it's always the same for a given user (and possibly all users). You concatenate this with the password in some way. The utility of this is that if a user's password is mypassword then it will be hashed as, say, mypasswordsalt so someone with a "rainbow table" of all hashes and the corresponding cleartext would normally have quickly known that the hash's…

This is going to make me sound like even more of an asshole , but I'm going to say it anyways because it is true: if you have to explain to yourself what a "salt" is, or you can't spell "nonce", you shouldn't be designing security systems. That doesn't mean your app needs to be insecure; it just means you should be using someone else's authentication system to do it.

This is hacker news. I think that we are all here to learn. We all have different levels of expertise as well as areas of interest. I'm personally not working a full time coding job yet because I'm still in school and I still have quite a bit that I want to learn just hacking around on my own smaller projects.

The fact that the concept of a salt isn't totally automatic to him or that he misspelled nonce only means that he shouldn't be designing security systems right now. There is a lot that we can all learn, some of us just have farther to go than others.

Re: Why you shoud never use your favorite password on News.YCombinator.com

#65

Post by cperciva »

tptacek wrote: post #59
cperciva wrote: post #58

Earlier quoted context omitted.

I didn't say that "passive-only attacks" were a reasonable threat model. In fact, I explicitly stated that I was not saying that the suggested mechanism was a good idea. But even if only 0.0001% of attackers are limited to passive-only attacks (and I suspect the actual value is higher -- more like 0.1%) then the suggested mechanism is 0.0001% more secure than transmitting the password in plaintext -- which invalidate…

No, because you're ignoring the fact that one of the 15-odd places that an attacker can bust up to redirect traffic to their own servers is the "observe all packets" vantage point, which allows them to predict DNS XIDs and source ports. I know you're smarter than this, Colin. I think you're being pedantic. Would you advise anyone on this message board any differently than me ? I think you already said "no".

Would you advise anyone on this message board any differently than me? I think you already said "no".

There are two parts to giving advice: Helping people with their immediate question, and helping people better understand the field in question so that they won't need your advice the next time. You told people that what they were talking about doing was a bad idea, which I agree with; but the explanation you gave was misleading.

I agree with your recommendation of "don't do that"; but I think it's important for people to understand WHY they shouldn't do that -- and claiming that it's "no more secure" rather than explaining that it's very slightly more secure obfuscates rather than elucidates.

Re: Why you shoud never use your favorite password on News.YCombinator.com

#66

Post by fiaz »

Hexstream wrote: post #29
fiaz wrote: post #25

Earlier quoted context omitted.

I don't understand why this guy is getting down modded...I think it's perfectly reasonable to ask a question without incurring a penalty, regardless of how much you disagree with it.

I wouldn't want us to set a precedent such that everyone formulate statements as questions to avoid the possibility of being modded down?

What about "listening to your users?"

Re: Why you shoud never use your favorite password on News.YCombinator.com

#67

Post by cperciva »

tptacek wrote: post #43
bct wrote: post #30

Earlier quoted context omitted.

> Digest access authentication is an immediate and halfway decent fix. It really is a shame that browsers have such a terrible UI for HTTP auth.

Before you consider converting your own web app to HTTP auth instead of login forms, be aware of the fact that several of the top security firms will demerit your app for doing it, and that will hurt you selling to companies. I don't totally agree with this (HTTP digest auth, while silly, is still better than the crazy Javascript hashing schemes), but the logic is, it is difficult to "log out" and manage sessions wit…

be aware of the fact that several of the top security firms will demerit your app for doing it

Speaking as FreeBSD Security Officer: Several of the top security firms provide ratings which reflect the quality of their checklists more than the quality of the security in the systems they're assessing. The FreeBSD security team recently dealt with a case of "if you don't fix this, people using FreeBSD will lose marks on PCI audits" -- and our answer was "screw the auditors, this isn't a security issue and we're not going to send out a bogus security advisory just to keep some idiotic auditors happy".

Re: Why you shoud never use your favorite password on News.YCombinator.com

#68

Post by volida »

tptacek wrote: post #61
gojomo wrote: post #57

Earlier quoted context omitted.

That's an active attack. My statement was clear and correct. The number of people who can passively eavesdrop on traffic (eg, on open wifi) is much larger than those who can dynamically change traffic in transit.

There are no passive-only attackers. Attackers who can observe raw traffic can hijack it (if it's the '90s) or redirect it (if it's 5 years ago, and in Brazil, and money is involved --- just to make it specific). Look, we're locked in an Internet message board death struggle and neither of us are going to concede anything, so let me just finish with this tangent: If you tried to sell an app to a Fortune 1000 company…

you are saying that if someone is encrypting the password using RSA in javascript and then using the hash to exchange the password between server/client, is volnerable because someone can interfere in the traffic and change the javascript served to the user, so that the password is sent in plaintext and therefore steal the password?

then why meebo and other sites practise this method without security problems?

Re: Why you shoud never use your favorite password on News.YCombinator.com

#69

Post by rplevy »

kwdowicz wrote: post #12
cperciva wrote: post #3

Of course the password is in plaintext. Logins are done via HTTP, not via HTTPS. You know, there isn't that little yellow lock thingy in the bottom left corner of the window? Is this really news to anyone?

users have million sites where they have logins and passwords - they can't have million password - even pattern can be guessed. If the risk is to low it's ok to not use HTTPS. But some blurring would give positive results - as like some hackers commented already.

One approach is to invent a mnemonic system for constructing secure passwords. The passwords should be systematically related to the specific site (including variables that are only known or relevant to you), but the patten should not be obvious to anyone but yourself (and memorable enough that the passwords & method of constructing do not need to be explicitly recorded). This makes it possible to have a unique password for every site. As a further foil to anyone who might somehow crack the pattern, use different mental password construction algorithms for sites with different levels of perceived security importance (although then it is easier to get confused).

Re: Why you shoud never use your favorite password on News.YCombinator.com

#70

Post by huhtenberg »

immad wrote: post #35

use clickpass

Actually - don't.

http://img223.imageshack.us/img223/3784/clickpasskf8.png

http://codefromthe70s.org/sslblacklist.asp

If they don't care about the security of their web interface, do you really want to entrust them with your passwords ?

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