What is the best “forgot my password” method? [dup

问题:

Possible Duplicate:
Forgot Password: what is the best method of implementing a forgot password function?

I'm programming a community website.

I want to build a "forgot my password" feature.

Looking around at different sites, I've found they employ one of three options:

1. send the user an email with a link to a unique, hidden URL that allows him to change his password (Gmail and Amazon)

2. send the user an email with a new, randomly generated password (Wordpress)

3. send the user his current password (www.teach12.com)

Option #3 seems the most convenient to the user but since I save passwords as an MD5 hash, I don't see how option #3 would be available to me since MD5 is irreversible. This also seems to be insecure option since it means that the website must be saving the password in clear text somewhere, and at the least the clear-text password is being sent over insecure e-mail to the user. Or am I missing something here?

So if I can't do option #1, option #2 seems to be the simplest to program since I just have to change the user's password and send it to him. Although this is somewhat insecure since you have to have a live password being communicated via insecure e-mail. However, this could also be misused by trouble-makers to pester users by typing in random e-mails and constantly changing passwords of various users.

Option #1 seems to be the most secure but requires a little extra programming to deal with a hidden URL that expires etc., but it seems to be what the big sites use.

What experience have you had using/programming these various options? Are there any options I've missed?

回答1:

4) Crediting their bank account with two random amounts and ask them to enter those in.
5) Snail mail them some new password and ask them to enter it in.
6) Have them text or call some number and enter some value to a phone number with the mobile phone they registered on file.
7) Get out of the password management problem altogether by outsourcing it to OpenID providers like Stack Overflow, Facebook, blog engines, and others are starting to do.

Outside of those, use option #1 or #2 with the added feature that both expire in an hour.

回答2:

I'm shocked at the upvotes on answers describing #1 and #2 as equivalent. They aren't at all. Sending the user a short term link to change their password is the most convenient, most commonly used, and most secure approach that doesn't involve an out of band interaction (mail, text msg, etc.). A few reasons:

1. Setting a temporary password via a forgot password link allows users to effectively change a user's password and lock a user out of their account if they know the user's login. With a link, the user simply knows someone is messing around and their access isn't impacted.
2. The password reset link is only valid for a short period, so there's a very small window for an attacker to strike. And even if they did, the user would know because the reset link would no longer work if the attacker intercepted the link and used it to change the password. If the new assigned password isn't changed by the user immediately, the attacker who intercepted the password can quietly impersonate the user indefinitely. So the big difference is, while a hacker can intercept the reset password link email, if they use the link to change the user's password, the user will know something is wrong because the link won't work and they'll generate another password reset request.
3. Easier to use - the user simply clicks a link in their email rather than typing a new random password you've generated.

And security questions often make a site less secure, not more - they're another attack vector and often the weakest link. I highly recommend reading The Web Application Hacker's Handbook for an excellent discussion on this topic.

回答3:

Note that Option #2 also requires you to keep track of the old password and expire the new random password if it isn't used within, say 24 hours.

Otherwise I could annoy you by repeatedly issuing you a new random password -- if you are not near your email you might not know why you cannot log in with your normal password.

Also, please avoid requiring an "identification question". The answers to these questions are typically much easier to guess/lookup than real passwords -- so everybody can identify themselves as me. See the Sarah Palin story for a recent example of how insecure this is.

回答4:

Options 1 and 2 as insecure as each other.

There. I said it. If the user's email account has been breached, there's no reasonable secure way to do things unless you collect more private data like their address, mother's maiden name - all of which can be guessed.

The best (albeit most annoying) version I have seen is where you need to remember a secret question and a secret answer. It means the user has to remember which question they asked, which, of course, can always be forgotten too!

If they forget the question and you're a "real" company, there's always the option of sending the user a token through the post, with instructions on how to reset all their security... It's very unlikely that a hacker will have access to their real life mail.

A skew on that would be to collect a telephone number when the user created the account. If that existed and they couldn't remember any of their details, you could set up some sort of automated calling system that told them how to reset their details.

And one thing to mention about #2: Don't let the process overwrite the current account password. If that happened anybody could say they forgot any account's password, triggering lots of unwanted password changes.

回答5:

There's no real difference between the security of option 1 or 2. Option 1 is effectively the same as preloading the new password in the form.

In fact, with the prevalence of phishing attacks, one could argue that encouraging use of option 1 with long URLs could make people less alert about clicking on long mysterious URLs.

回答6:

Read the OWASP top ten to make sure your method is compliant.

Here is the direct link.

回答7:

Just a quick note on something not specifically in regards to your question. You mentioned you used MD5 to hash stored passwords. Regardless of whether you choose to use Options 1 or 2 (3 is going to be the least secure as, for obvious reasons), MD5 is a cracked hashing algorithm, and can actually make it fairly easy for hackers to gain access to accounts protected by MD5 hashing.

You can read more about the vulnerability it at the following URL: en.wikipedia.org/wiki/MD5

A better hashing solution would be something like SHA, which is still a stable and secure hashing algorithm. Combined with option #1 or #2, you should have a reasonably secure system in place to protect your users passwords, barring all but the most determined hackers.

回答8:

Option #1 is probably the best. #3 is insecure (and I also suggest using something stronger than MD5, such as SHA1). Option #2 is not good because it allows any random person to lock you out of your account until you check your email, unless you use a security question. And security questions are often easier to crack than passwords.

回答9:

Option #1 has a couple of major advantages over #2. If a random user types in my email address into the "I have forgotten my password" box, then my password will not be reset. Also, it is slightly more secure in that there is no permanent record of the site's password stored in your gmail inbox forever.

A critical missing piece here is that the link you provide in #1 should only work for one password reset and have a time limit

All these solutions mean that you are treating your email inbox as the "one ring" that rules them all. Most online services seem to be doing this now days anyway.

My preferred approach is to go with openid where possible. Password management is hell that no one seems to get quite right. It's easier to hand this problem to someone else.

回答10:

Option 4: Require user to reset password by entering their account name AND email address. As long as you aren't disclosing real names or email addresses on the site (WHY would you in this day and age?) this is a reasonably secure and tamper-proof method. Send a link to a reset page, not the password itself.

Option 5: Use OpenID and pass the responsibility to a 3rd-party to worry about it.

Honestly though this is a lot more effort than most sites require. I for one LIKE receiving plaintext passwords by email because I store them in a "registrations" folder in my inbox. That way I can lookup passwords for sites when I forget them (which happens a lot!). If somebody is reading my email I have bigger problems to worry about than people using my twitter account (if I had one). Of course banks and corporations have stronger requirements but you didn't specify what your site is. That's the key to the best answer.

回答11:

I agree with your comments about option #3 being insecure.

As for programming either #1 or #2, option #2 is easier to program but #1 isn't much harder and both are probably about as secure as each other.

Whichever option you choose, you can also consider making it more secure by including requests for personal information (that you obtain during registration) as part of the forgotten password process.

I've programmed systems where you have a username and to get a new password you have to enter both your username and your email address. You can get sent a reminder of your username but the main point is that someone probably won't be able to guess your username and your email but if you do it just on email, there's less secure.

Secret questions are an approach to the personal information part. I personally think they don't offer a lot of value as people tend to choose questions that many people will either know the answer to, be able to guess or be able to find out. It is better than nothing however so long as you use it in conjunction with an already relatively secure method.

Obviously the more of this you do, the more programming work it is.

The simplest method is:

1. Have a "remind me of my username" link (enter email). Don't tell the user if an email was sent or not because people can use that to find out if an email address is of a member. Always tell the user to check their inbox for the reminder email but only send it if someone is a member; and
2. Require both username and email to get sent a new one-time password. That password should only last an hour or so. When the user uses it, they should be forced to change their password immediately.

回答12:

Either option 1 or 2 would be fine. As you said, option 3 is insecure as you would need to store the clear text password. You could probably get fancy and use a reversible encryption algorithm to store/retrieve the password, but with better alternatives available to you there's no reason to go down that road.

回答13:

There is an additional option that you can use in combination with any of the options that you mention:

You can let the user write a reminder for their password, that you send to them as the first step when they have forgotten the password. If the reminder doesn't help the user, you can go on to the next option.

As the reminder isn't the password itself, it's safe to send by mail (or perhaps even display directly on the page).

回答14:

If you are hashing them Option 3 is unavailable and if you are not hashing them, shame on you. :)

I prefer option 1, sending a reset password link sent to their email which allows them (for a limited time) to reset their password. It does require more work, but it's easy for them to use and ultimately as secure as their email login process.

回答15:

You could made a mix between #1 and #2, taking advantages from both:

Send the user an email with a link to a unique, hidden URL that allows him to change a new randomly generated password.

That page could be SSL, and the password could expire in 12-24 hours.

回答16:

I've tried a couple of methods that I've not really been happy with. What I've settled on for the next project is to:

1. User enters username and email address
2. Email sent with link containing url and guid param which has been stored in db with 48 hour expiry
3. User confirms password to be reset
4. New password is emailed to user
5. Login with new password displays message or redirects to change password page.

回答17:

Instruct the user come personally to your offices and prove her identity with id card or passport.

This, of course, assumes that you have offices near your users and that the account are valuable enough to justify this procedure. Suitable for example banks.