Graham Iossi created GUACAMOLE-990:
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Summary: TOTP Rate Limit To Mitigate Brute Force Security
Vulnerability?
Key: GUACAMOLE-990
URL: https://issues.apache.org/jira/browse/GUACAMOLE-990
Project: Guacamole
Issue Type: Improvement
Components: guacamole-auth-totp
Affects Versions: 1.1.0
Reporter: Graham Iossi
Google's [libpam
module|[https://github.com/google/google-authenticator-libpam/blob/master/man/google-authenticator.1.md]]
has a rate limit option to prevent brute forcing.
Does Guacamole's TOTP have anything built-in that's introducing any sleep/delay
in the code input loop?
It _seems_ like it doesn't from my clumsy attempts at testing this by just
hammering the keyboard :)
If that's true then it seems like this would potentially be easier to bypass
than even the password itself. I might be butchering the napkin math here, but
with a possible number range of 1 million (6 digits) and 30 seconds, assuming a
WAN latency per attempt of 7ms, that would mean that on average, once a hacker
broke a password, they could then break through the TOTP segment over a
scripted 233 login attempts or so.
If there was even a plain old unconfigurable 1 second sleep built in to the
code input loop between attempts without even any added guacamole.properties
options being introduced, I think this would basically handle the problem by
pushing the possible average breakthrough time into unreasonable timelines.
Also, though this would be another issue, it seemed that incrementing
totp-digits with v1.1.0 to 8 didn't result in 8 digits being displayed when I
scanned the resulting barcode in google authenticator. The introductory user
bit did specify 8 digits - just not the resulting google authenticator entry.
That may just be a bug in google authenticator however - not sure as I haven't
tested any other TOTP apps, but I thought I'd mention it.
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