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Security notes
(These are misellaneous security notes, collected during and around the threat modeling sessions with Eleanor Saitta.)
- Fuzzing: e-mail parser and httpd should be fuzzed constantly
- We should accept the Syndis offer to get audited and pentested
- We should use SSLlabs to make sure we don't forget to upgrade our TLS configs when new vulnerabilities are found
- Look into XSS/CSRF/... test suites, beg for free licenses from vendors if necessary. (Ella can give advice & leads)
- We should test the GnuPG interface code extra carefully, as not all versions of gpg are the same.
Side note: it might make sense to run the GPG tests on setup and make sure the app isn't making promises it can't keep. Reporting back incompatibilities would help development, as long as we respect user privacy.
Any data downloaded from the internt (keys, gravatars, etc.) should be downloaded using Tor if possible, and we should make an effort to:
- Look like other common apps/browsers so we can't be targeted with exploits
- Change Tor identity frequently to prevent the data provider or exit node operator from being able to infer information about our mail or social graph.
Anonymizing logs is important so users can send us bug reports without leaking confidential data.
The Tor project has done some interesting work on privacy friendly global logging for gathering of statistics, we should look at what they are doing.
Users need to understand that the multiple personalities features of Mailpile are "soft" and if they want to be sure no data leaks from one personality to another, they should run separate instances of the app.
Ella had some very specific scenarios where information about GPG keys and trust levels could leak from one persona to another. She felt this pertained most strongly to SMTorP use.
Use the UW protocol? Bittorrent prevents us from targeting individual users!
It can be important to make sure workflows can only be done in the order specified. This can be done by passing variables that link step1 to step2 so skipping step1 (or tricking someone into skipping step1) is impossible.
Comparisons with strings in Python may differ with those in the OS/FS layer, especially due to Unicode complicating everything.
Treating paths as byte-lists and strictly limiting which chars are allowed (kill the unicode) can help.
An entire class of bugs can be eliminated if data is dumbed down to ASCII as soon as it enters the system. This may be OK for things like the URL path, impossible for input variable values.
Wrapper classes that have funny instance variables or getters which signify "untainted" data. Passing a string directly or some other data which has not been "cleaned" will trigger an AttributeError exception.
This library is an anti-XSS library. Check it? http://code.google.com/p/reform/
OWASP anti-samy, helps make HTML safe to display.
Statement of intent? How do we deal with them? Format verification, include ClamAV? Recommended way would be to neutralize content into known-safe forms by converting images to themselves, PDF rendered in JS, etc.
Support Tor for connecting to IMAP/SMTP.
Mixmaster/mixminion (later): We know the NSA can probably do timing analysis on Tor. Mix networks, if they had traffic and were maintained, would resist this. Clearsigned e-mails exiting from mix nodes could provide cover traffic. Ask users "do you wanna help make the network anonymous?". Delays things... button to "send fast"? ..... Ella says: IMPORTANT. Consider this as an alternate transport.
Backwards compatibility is bad. We want to just support new browsers and real security if at all possible.
Optimal case:
- Help people buy domains
- Buy keys
- Make end-to-end TLS over pagekite easy
Make sure SPF gets configured, think about DKIM.
Others: self-signed, pagekite MITM.