WebApp Sec mailing list archives
RE: At what layer to hash a password
From: Niels Teusink <teusink () fox-it com>
Date: Mon, 28 Jun 2010 22:37:54 +0200
As I see it you have three options: on the client in javascript, in the application or in the database On the client seems nice, but there are both advantages and disadvantages + you hash the password before it's even sent to the server, so the server never actually has the plaintext password - you'll have to implement some challenge/response scheme, or the password can simply be replayed - if you implement challenge/response, your client has to do something like this: hash(hash($password+$salt)+$challenge). This means that an attacker could authenticate with hash($password+$salt) instead of the password, which is the thing that is stored in your database (passing-the-hash attack) and the attacker won't have to crack the passwords to authenticate as a user if he breaks into the database - some people use it as an SSL alternative but it's not a very good one (a skilled attacker in a MITM position just grabs the session cookie or changes the javascript on-the-fly to submit the plaintext password as well). It does offer some protection from passive sniffing though - needs javascript to be enabled In the application + it's easy and you can hash the password just after receiving it - your application still receives the password in plaintext, it temporarily ends up in memory in lots of places (but an attacker will probably modify your app instead of going through RAM) In the database + one system for all your applications (but if you want to change the algorithm you run into problems with existing passwords anyway) - you have to do something like UPDATE users SET password = MYHASH('plaintextsecretpass'||salt) WHERE id=1 and your password will end up plaintext in your database logs. I tend to do it in the application just after receiving the password. I really like the approach of native database accounts as well, but you'll have to store the plaintext password (or a connection handle if you can) in the user session. No perfect solution I guess :) (especially if you have the multiple interfaces thing to take into account) Niels -----Original Message----- From: listbounce () securityfocus com [mailto:listbounce () securityfocus com] On Behalf Of Robin Wood Sent: maandag 21 juni 2010 15:06 To: webappsec () securityfocus com Subject: At what layer to hash a password When developing a web app using a presentation (html generation not browser side), application and database layer approach at what level should you encode a password that is on its way into a database? I'm generally thinking of hashing as the main encoding method but anything could be used. If you go for presentation layer then you could end up needing to update multiple areas of the code if you change the encoding method changes. You can pass this off to a function but in some situations you could still end up having to make multiple updates. The advantage of this layer is that the password is protected for its whole journey down the stack and into the database so even if it leaks in a debug or error log for example the plaintext isn't leaked. You could also have a problem if you use multiple different presentation layers keeping them all in sync and ensuring they all have the correct functionality to perform the encoding. At the other end if you do the encoding at the database layer then you only have a single point to change to update the algorithm so this is better from a coding point of view but there is the potential for the password to leak out on its way there. This leaves application layer, might be the best as you can pull all the setting calls into a single place but there is still chance of some leakage. I prefer the presentation layer from a security point of view but from clean coding I'd rather do it at database layer the same way I encode timestamps to what will go into the database at the last minute. What do other people think? Robin This list is sponsored by Cenzic -------------------------------------- Let Us Hack You. Before Hackers Do! It's Finally Here - The Cenzic Website HealthCheck. FREE. Request Yours Now! http://www.cenzic.com/2009HClaunch_Securityfocus -------------------------------------- This list is sponsored by Cenzic -------------------------------------- Let Us Hack You. Before Hackers Do! It's Finally Here - The Cenzic Website HealthCheck. FREE. Request Yours Now! http://www.cenzic.com/2009HClaunch_Securityfocus --------------------------------------
Current thread:
- At what layer to hash a password Robin Wood (Jun 26)
- Re: At what layer to hash a password Chris Travers (Jun 28)
- Re: At what layer to hash a password Javier Bassi (Jun 28)
- Re: At what layer to hash a password Chris Travers (Jun 29)
- RE: At what layer to hash a password Dave Wichers (Jun 28)
- Re: At what layer to hash a password Robin Wood (Jun 28)
- Re: At what layer to hash a password Tom Ritter (Jun 28)
- Re: At what layer to hash a password Grega Bremec (Jun 28)
- Re: At what layer to hash a password Robin Wood (Jun 28)
- Re:Re: At what layer to hash a password 薛 (Jun 29)
- Re: At what layer to hash a password Grega Bremec (Jun 28)
- RE: At what layer to hash a password Niels Teusink (Jun 28)
- Re: At what layer to hash a password Chris Travers (Jun 29)