1446549 - nsIMIMEService implementations are not compatible with content sandboxing

Status: NEW

(Core :: Security: Process Sandboxing, defect, P2)

Description

[Haik Aftandilian [:haik]]

The nsIMIMEService implementations rely on getting information about installed applications and that is problematic when used from content processes. On Mac, the system libraries that are used to lookup the application used for MIME types depend on being able to read from /Applications which is blocked in content processes. This is a problem on Linux too. See Mac bug 1437281 and bug 1391186 and Linux bug 1382323 for examples. There are still some call sites that do MIME lookups in content. We should refactor our code so that content processes don't do MIME lookups OR, if they need to, we should remote the API's.

Comment 1

[Jed Davis [:jld] ⟨⏰|UTC-7⟩ ⟦he/him⟧]

For reference, bug 1434392 was indirectly caused by this — it was a regression caused by bug 1412464 which was a sandboxing workaround for the MIME service.

Comment 2

[Haik Aftandilian [:haik]]

Bug 1452278 remoted some of these problematic calls on macOS and went into Firefox 68. The plan with 1452278 was to enable it for all platforms after some soak time. This can be tested on other platforms by changing nsExternalHelperAppService::GetSingleton() to use nsOSHelperAppServiceChild for child processes like it does for Mac.