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This directory includes some working notes to audit the entire Teliva codebase
for side-effects that should be gated/sandboxed.
Founding principle for this approach: Side-effects come from the OS. There can
be no effects visible outside a Unix process (regardless of language) if it
doesn't invoke any OS syscalls.
## Top down
Things to secure:
* screen? Keep apps from drawing over standard Teliva UI elements.
* Teliva currently doesn't stop apps from overwriting the menu, if they're
clever. However, it always redraws its UI elements before accepting any
input from the keyboard.
* code? There are currently no protections against .tlv files clobbering
existing definitions. I'm hoping that disallowing native code keeps this
safe. Apps can only affect themselves.
* files opened (for read/write) on file system
* `io_open`
* `io_lines`
* destinations opened (for read/write) on network
* `inet_tryconnect` // `socket_connect`
* `inet_tryaccept` // `socket_accept`
It seems more difficult to control what is written to a file or socket once
it's opened. For starters let's just focus on the interfaces that convert a
string path or url to a file descriptor.
Scenarios:
* (1) app reads system files
* (1) app sends data to a remote server
* (1) app should _never_ be allowed to open Teliva's system files:
- `teliva_editor_state`
- app-specific sandboxing policies
* (2) app can read from a remote server but not write (POST)
* app gains access to a remote server for a legitimate purpose, reads
sensitive data from the local system file for legitimate purpose. Now
there's nothing preventing it from exfiltrating the sensitive data to the
remote server.
- (2) solution: make it obvious in the UI that granting both permissions
allows an app to do anything. Educate people to separate apps that read
sensitive data from apps that access remote servers.
- (2) solution: map phases within an app to distinct permission sets
* app A legitimately needs to read sensitive data. It saves a copy to file
X. app B seems to legitimately needs to access the network, but also
asks to read file X. If the owner forgets who wrote file X and what it
contains, sensitive data could be exfiltrated.
* (3) app wants access to system() or exec() or popen()
Difficulty levels
1. I have some sense of how to enforce this.
2. Seems vaguely doable.
3. Seems unlikely to be doable.
UX:
* distinguish what Teliva can do, what the app can do, and Teliva's ability
to police the app.
* easily visualize Teliva's ability to police an app.
- maybe show a lock in halves; left half = file system, right half =
network. One half unlocked = orange. Both unlocked = red.
## Bottom up
* `includes`: all `#include`s throughout the codebase. I assume that C the
language itself can't invoke any syscalls without at least triggering
warnings from the compiler.
```
cd src
grep '#include' * */* > ../sandboxing/includes
```
* `system_includes`: all `#include <...>`s throughout the codebase. I assume
side-effects require going outside the codebase. `#include`s could smuggle
out of the codebase using relative paths (`../`) but I assume it's easy to
protect against this using code review.
```
grep '<' sandboxing/includes > sandboxing/system_includes
```
* `unique_system_includes`: deduped
```
sed 's/.*<\|>.*//g' sandboxing/system_includes |sort |uniq > sandboxing/unique_system_includes
```
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