CODEWITHSUNDEEP
urlpasswordsreset
Pratik Kothari
Pratik Kothari

Reputation: 2446

Generate temporary URL to reset password

I am looking to implement a Forgot Password feature on my website. I like the option where an email containing a temporary one-time use URL that expires after some time is sent to the user.

I have looked at the following pages to get these ideas but I am not sure how to implement this using ASP.NET and C#. As one of the users indicated, if I can implement this without storing this information inside the database, that will be ideal. Please advise.

Password reset by emailing temporary passwords

Thanks.

Upvotes: 34

Views: 57861

Answers (9)

Sandeep yadav
Sandeep yadav

Reputation: 1

There is an issues with this approach. A safe hash makes the token really long. Either you integrate the salt into the hash itself (makes it about 20 charactes longer), or you store this unique salt in the database. If you store the salt in the database, you could as well store a random token which is not derrived from any existing

Upvotes: 0

Mitchel Sellers
Mitchel Sellers

Reputation: 63126

Depending on your needs, you could encrypt information, in a format similar to the following format

(UserId)-(ExpireDate)

Encrypt the data, make that the link, then decrypt the data and take action from there...

Crude, but most likely usable, and not requiring DB usage

Upvotes: -3

Stephen Turner
Stephen Turner

Reputation: 7314

I'd use a hash code to validate details in the password reset url. This can all be done without writing anything to the DB or sending any privileged info to an attaker.

To briefly explain normal password salt and hashing; say the salt is 1111 and the pasword is password, you'd concatenate the two and hash the string 1111password, say this gives you a hash of 9999, you'd then store the original salt 1111 and hash 9999 in your user record.

When you are validating a password you use the stored salt, concatenate the password attempt, hash it and compare with the stored hash. For example asecret becomes 1111asecret but hashes to 8888. This doesn't match the original hash so the password match fails.

Of course the salt and hash would normally be properly generated and calculated with established crypto libraries (don't invent your own!).

For the password reset URL I'd put in the unique identifier for the user, i.e. email address, the date the request is made, and a new hash. This hash would be generated from those details concatenated together plus the salt and hash already stored for the user.

For example:

Email: [email protected]
Request Date: 2014-07-17
Salt: 1111
Hash: 9999

Generate a new hash of those concatenated, i.e. '[email protected]', say this gives a hash of 7777.

The URL I then generate would then have the email, request date and the new hash:

https:\\www.example.com\[email protected]&requestdate=2014-07-17&hash=7777

The server will combine the email and supplied date with it's salt and hash and confirm the hash it generated is the same as the supplied one. If this is Ok then it will show the reset form with the same three parameters hidden behind it, otherwise an error. These get resubmitted and rechecked when the new password is entered to prevent that form being spoofed.

The email address needs to be supplied to make the request and it is only sent out in an email to the same address. the date is hardly priveleged info and the hash is not reversible so gives nothing anyway. Nothing has been written to the database and any tampering with the parameters causes the hash to fail and the URL to report an error.

Upvotes: 0

user813006
user813006

Reputation: 11

I would definitely include the database in this process. Once a reset is requested, it's a good idea to indicate that the account is locked out.

For example, if you are changing your pw because you think your account may have been compromised, you definitely don't want it to remain accessible while you go about the change process.

Also, inclusion of "real" information in the reset token could be decoded if someone really wants it and has the horsepower. It would be safer to generate a random string, save it in the db in the row for that user, and then key back to it when the link is clicked.

This gives you two things:

1) There's nothing to decrypt, and therefore nothing of value can be gained from it. 2) The presence of the token in the user record indicates that reset is in progress and the account should be treated as locked out.

Upvotes: 1

QMaster
QMaster

Reputation: 3904

The goal of sending some data|string to user email is validation of account owner. Please care about some points:

  • Avoid sending important information in reset or activate link.
  • It's best way to store unique string data conjunction with user account and send it as that link. but be aware if you send just one section as link to user email and just check it in page, your application may be in dangerous by brute-force or dictionary attacker. It's enough to check a list of string to find some links and change password. I know that has a little chance, but not zero.

Result: I think it's better if you

  1. combine user email with string link then encrypt them (not hash because hashed value can't be reverse) and send to user email.
  2. User click and your page get the encrypted value.
  3. decrypt value.
  4. extract user email.
  5. find email in database.
  6. compare string from received link with other one attached to user email in database.

Good luck.

Upvotes: 0

Rick Putnam
Rick Putnam

Reputation: 546

@Alex

You can also use System.Security.Cryptography classes in .NET for the hash algorithms. For example:

using System.Security.Cryptography;
...
var hash = SHA256CryptoServiceProvider.Create().ComputeHash(myTokenToHash);
...

Upvotes: 2

Alex
Alex

Reputation: 1609

I used a Hashing Class to create unique automatic logins made up of the current date/time and the users email address:

string strNow = DateTime.Now.ToString();
string strHash = strNow + strEmail;
strHash = Hash.GetHash(strHash, Hash.HashType.SHA1);

get the Hash Class from: http://www.developerfusion.com/code/4601/create-hashes-md5-sha1-sha256-sha384-sha512/

Then just take it from the URL using:

if (Request.QueryString["hash"] != null)
{
                //extract Hash from the URL
                string strHash = Request.QueryString["hash"];
}

Upvotes: 1

Scott Arrington
Scott Arrington

Reputation: 12503

Probably the easiest way is going to be to modify your users table to add 2 extra columns, OR if you don't want to modify the existing table you could add a new dependent table called "UserPasswordReset" or something like that. The columns are like this:

PasswordResetToken UNIQUEIDENTIFIER,
PasswordResetExpiration DATETIME

If you go with the additional table route, you could do also add the UserID column, make it a primary key and a foriegn key reference back to your users table. A UNIQUE constraint would also be recommended. Then you simply use a Guid in your asp.net application as the token.

The flow could be something like this:

  1. User requests password reset for their account
  2. You insert a new record in the table (or update their user record) by setting the PasswordResetExpiration to a date in the future (DateTime.Now.AddDays(1)), and set the token to Guid.NewGuid()
  3. Email the user a link to your ResetPassword.aspx page with the guid in the query string (http://www.yoursite.com/ResetPassword.aspx?token=Guid-here)
  4. Use the ResetPassword.aspx page to validate the token and expiration fields. (I.E. Make sure DateTime.Now < PasswordResetExpiration)
  5. Provide a simple form that allows the user to reset this password.

I know you wanted to avoid modifying the database, but it really is probably the simplest method.

Upvotes: 79

Goyuix
Goyuix

Reputation: 24340

Here, the System.Guid class in your friend, as it will generate a unique (well, unique enough) 128-bit number:

  • Generate a new Guid ( System.Guid.NewGuid() )
  • Store that Guid somewhere (Application object maybe?)
  • Send a custom URL in an email with that Guid
  • When the user hits the site, make them enter the password you sent in the email
  • If the passwords match, go ahead and force them to enter a new password

Upvotes: 1

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