Vulnerable Regular Expression

[cristianstaicu]

The following regular expression used for parsing the user agent is vulnerable to ReDoS:

/Dell.*Streak|Dell.*Aero|Dell.*Venue|DELL.*Venue Pro|Dell Flash|Dell Smoke|Dell Mini 3iX|XCD28|XCD35|\b001DL\b|\b101DL\b|\bGS01\b/i

The slowdown is moderate: for 50.000 characters around 10 seconds matching time. I would suggest one of the following:

• remove the regex,
• anchor the regex,
• limit the number of characters that can be matched by the repetition,
• limit the input size.

If needed, I can provide an actual example showing the slowdown.

[hgoebl]

Thanks for your contribution. As this project is just a "satellite" of Mobile-Detect (php) and all patterns are generated based on Mobile-Detect, we have limited power to change the RegExs.
Would you mind opening an issue in Mobile-Detect?

BTW the string used to match patterns is the user-agent string. Do you think there's still an issue?

[darrenscerri]

BTW the string used to match patterns is the user-agent string. Do you think there's still an issue?

An attacker can send a user-agent string of arbitrary length

[serbanghita]

@cristianstaicu @darrenscerri @hgoebl Ok, I'm limiting the .* regex. I'm taking a look at the DB and come back with an updated regex

[serbanghita]

@hgoebl can you assign me to this?

[hgoebl]

IMHO we should better limit the input size.
In case of mobile-detect.js it's not desirable to have significantly longer regexps.

@serbanghita (dumb question) how can I assign this to you?

[darrenscerri]

@hgoebl I think a global limit on the input size would be more appropriate than fiddling with the regexps. I think a limit of 500 characters is quite reasonable.

[serbanghita]

Guys I took a look at the User-Agent database regarding Dell and simplified the regex, I also limited the length of the User-Agent to max 500 characters.

[johnstew]

Is this still a vulnerability or is everything good in 1.4.1?

[hgoebl]

fixed in 1.4.0