At minimum you need to limit the request size to avoid DOS attacks and such. But obviously that would be a much larger limit than anyone would use for a password.
And sure, in theory your hashing browser-side could break if you do that. Depending on how much text the user pastes in. But at that point, it’s no longer your problem but the browser’s. 🦹
wouldn’t you then just break it up into chunks of 72 bytes, hash them individually, and concatenate the hashes? And if that’s still too long, split the hash into 72 byte chunks and repeat until it’s short enough?
I don’t know the specifics behind why the limit is 72 bytes, but that might be slightly tricky. My understanding of bcrypt is that it generates 2^salt different possible hashes for the same password, and when you want to test an input you have to hash the password 2^salt times to see if any match. So computation times would get very big if you’re combining hashes
Why would you not hash in the browser. Doing so makes sure the plaintext password never even gets to the server while still providing the same security.
Because then the hash is the password. Someone could just send the hash instead of trying to find a password that gets the correct hash. You can’t trust the client that much.
You can hash the password on both sides to make it work; though I’m not sure why you’d want to. I’m not sure what attack never having the plain text password on the server would prevent. Maybe some protection for MITM with password reuse?
If you hash in the browser it means you don’t salt your hash. You should absolutely salt your hash, not doing so makes your hashes very little better than plaintext.
Oh you mean that the number 256 overflows into 0 in 8-bit range. My joke was leaning more into the idea that when you use all 256 possible bit combinations (1111 1111), it can represent -1 in signed integer formats. Even though 255 is the highest number you can directly represent, there are still 256 total combinations, including zero, so IMO, the joke works.
Yep. Having to have requirements that doesn’t flow with people very well and requiring constant updates, people WILL find shortcuts. In the office, I’ve seen sheets of paper with the password written down, I’ve seen sticky notes, I’ve seen people put them in notepad/word so they could just copy paste.
This is made worse, because you have to go out of your way for a password manager, which means you need to know what that is. And you need a good one because there has been (and I’m going to generalize here) problems with some password managers in the past. And for work, they have to allow a password manager for that to even be an option. Which you then end up with this security theater.
Usually 256 bit hash is used. 256 bits is 32 bytes or 32 characters. Of course you are losing some entropy because character set is limited, but 32 characters is beyond reasonable anyway.
The eff passphrase generator has about 2.5 bits of entropy per character (without word separators). Eff recommends 6 word passphrases, and with an avg word length of 7, that’s (only) 79.45 bits of entropy that won’t even fit in the 32 characters. If there wasn’t a password length limit it would be possible to saturate the hash entropy with a 20+ word & 102+ char passphrase.
I just double checked and I have TOTP enabled for my PayPal account so it should be an option.
I just found this support article of theirs and it says it can only be enabled through their website and not through the app (why?!) so you might be running into that?
Probably people would struggle to scan the QR Code with their smartphone. I think most apps can scan it from a image but obviously this would be unsafe, especially when people sync their screenshot to the cloud.
I can 100% confirm totp exist for PayPal, because I’m using it.
There’s a special place in hell for those who set an upper limit in password lengths.
I sort of get it. You don’t want to allow the entire work of Shakespeare in the text field, even if your database can handle it.
16 characters is too low. I’d say a good upper limit would be 100, maybe 255 if you’re feeling generous.
The problem is that you (hopefully) hash the passwords, so they all end up with the same length.
At minimum you need to limit the request size to avoid DOS attacks and such. But obviously that would be a much larger limit than anyone would use for a password.
Also rate of the requests. A normal user isn’t sending a 1 MiB password every second
What’s a sensible limit. 128 bytes? Maybe 64?
I’d say 128 is understandable, but something like 256 or higher should be the limit. 64, however, is already bellow my default in bitwarden
And sure, in theory your hashing browser-side could break if you do that. Depending on how much text the user pastes in. But at that point, it’s no longer your problem but the browser’s. 🦹
Why are you hasing in the browser?
Also, what hashing algorithm would break with large input?
bcrypt has a maximum password length of 72 bytes.
https://en.wikipedia.org/wiki/Bcrypt#Maximum_password_length
Damm, I legit didn’t knew there bcrypt had a length limit! Thank you for another reason not to use bcrypt
wouldn’t you then just break it up into chunks of 72 bytes, hash them individually, and concatenate the hashes? And if that’s still too long, split the hash into 72 byte chunks and repeat until it’s short enough?
I don’t know the specifics behind why the limit is 72 bytes, but that might be slightly tricky. My understanding of bcrypt is that it generates 2^salt different possible hashes for the same password, and when you want to test an input you have to hash the password 2^salt times to see if any match. So computation times would get very big if you’re combining hashes
Why would you not hash in the browser. Doing so makes sure the plaintext password never even gets to the server while still providing the same security.
Edit: I seem to be getting downvoted… Bitwarden does exactly what I described above and I presume they know more than y’all in terms of security https://bitwarden.com/help/what-encryption-is-used/#pbkdf2
Because then the hash is the password. Someone could just send the hash instead of trying to find a password that gets the correct hash. You can’t trust the client that much.
You can hash the password on both sides to make it work; though I’m not sure why you’d want to. I’m not sure what attack never having the plain text password on the server would prevent. Maybe some protection for MITM with password reuse?
Because then that means you don’t salt your hashes, or that you distribute your salt to the browser for the hash. That’s bad.
If you hash in the browser it means you don’t salt your hash. You should absolutely salt your hash, not doing so makes your hashes very little better than plaintext.
There’s nothing stopping a browser from salting a hash. Salts don’t need to be kept secret, but it should be a new random salt per user.
The eBay password limit is 256 characters.
They made the mistake of mentioning this when I went to change my password.
Guess how many characters my eBay password has?
-1?
Damn signed bytes!
0*
I’m not sure what you’re implying with this. But how did you dig this up anyway?
255=-1, 256=0
btw, the internet never forgets
Oh you mean that the number 256 overflows into 0 in 8-bit range. My joke was leaning more into the idea that when you use all 256 possible bit combinations (
1111 1111), it can represent -1 in signed integer formats. Even though 255 is the highest number you can directly represent, there are still 256 total combinations, including zero, so IMO, the joke works.Just paste it in here and I count the characters for you.
69
oh yeah
Oh and also, “change this every four weeks please.”
Okay then. NEW PASSWORD: pa$$word_Aug24
Invalid password, maximum 13 characters.
pa$$word0824
Only a maximum of 3 digits allowed
password must not start with digit
the password cannot contains the same sequences of characters as the old password.
and i have seen this requirement in a service that requires changing it every month for some reasons.
and this is to manage a government digital identity that allows to log it in all governments websites.
That’s a weird way to say “we store your password in plaintext”
Yep. Having to have requirements that doesn’t flow with people very well and requiring constant updates, people WILL find shortcuts. In the office, I’ve seen sheets of paper with the password written down, I’ve seen sticky notes, I’ve seen people put them in notepad/word so they could just copy paste.
This is made worse, because you have to go out of your way for a password manager, which means you need to know what that is. And you need a good one because there has been (and I’m going to generalize here) problems with some password managers in the past. And for work, they have to allow a password manager for that to even be an option. Which you then end up with this security theater.
coughLastPasscough
“Problems”. What an delightfully understated term to use.
Reasonable upper limits are OK. But FFS, the limit should be enough to have a passphrase with 4 or 5 words in it.
Usually 256 bit hash is used. 256 bits is 32 bytes or 32 characters. Of course you are losing some entropy because character set is limited, but 32 characters is beyond reasonable anyway.
The eff passphrase generator has about 2.5 bits of entropy per character (without word separators). Eff recommends 6 word passphrases, and with an avg word length of 7, that’s (only) 79.45 bits of entropy that won’t even fit in the 32 characters. If there wasn’t a password length limit it would be possible to saturate the hash entropy with a 20+ word & 102+ char passphrase.
Of course, but that’s because you are using a passphrases. Passwords have a much hogher entropy.
I’d be totally fine woth 32 characters! But I’ve come across too many websites with unreasonably short (20 characters or less) limits.
Just opened a PayPal account and their limit is 20. Plus the only 2fa option is sms 🙃.
I just double checked and I have TOTP enabled for my PayPal account so it should be an option.
I just found this support article of theirs and it says it can only be enabled through their website and not through the app (why?!) so you might be running into that?
https://www.paypal.com/uk/cshelp/article/what-is-2-step-verification-and-how-do-i-turn-it-on-or-off-help167
Probably people would struggle to scan the QR Code with their smartphone. I think most apps can scan it from a image but obviously this would be unsafe, especially when people sync their screenshot to the cloud.
I can 100% confirm totp exist for PayPal, because I’m using it.
That last part definitely isn’t true.
“Your password needs to be less than 65k characters long” >:(
Darn, can’t use the entire Bee Movie on Blu-Ray as my password then.
I mean you could compress it
Basically guaranteed to be a clear text offender
Especially since it takes more effort to limit it than leave it wide open for whatever length of password a user wants to use.
nvarchar(max)is perfect to store the hashed copy.