CGI question: safe passwords possible?

[Paul Rubin]

> Yes, you can have the client hash the password using JavaScript.  You
> can find free code for doing MD5 or SHA hashing in JavaScript, and then
> use code kind of like:
> 
> <form action="whatever" onSubmit="dohash(this)">
> <input type="password" name="password">
> <input type="hidden" name="password_enc">
> <script>
> function dohash(form) {
>   form.elements.password_enc.value = 
>       md5hash(form.elements.password.value);
>   form.elements.password.value = "";
> }
> </script>
> 

Don't do it that way, since the hashed value sent to the server is
re-useable.  Try something more like:

 <form action="whatever" onSubmit="dohash(this)">
 <input type="password" name="password">
 <input type="hidden" name="password_enc">
 <script>
 function dohash(form) {
   # Set "iv" to some random server-generated junk that's different every time
   iv = "un43iuhiuanasdcainini3nr3r"

   form.elements.password_enc.value = 
       md5hash(iv + md5hash(iv + form.elements.password.value));
   form.elements.password.value = "";
 }

> (testing this and finding the md5hash implementation are excersizes left
> to the user)

MD5 and SHA Javascript implementations are available at:

  http://pajhome.org.uk/crypt/md5/index.html

There's also some scripts there for doing the kind of thing the OP is
asking.