Official `sandboxed-tor-browser` binaries break with PaX MPROTECT.

[yawning]

I suspect this is something to do with our deterministic build setup, as I do development on a box with a grsec kernel. The binary itself will run fine if you add the override attribute with setfatter or paxd, but it would be nice if it worked out of the box.

[cypherpunks]

Do you have any more information about the crash? What library shows a denied RWX mmap in the kernel log? What do the logs from strace -fe trace=memory,process say?

I really doubt it has anything to do with a deterministic build setup. The only things PAX_MPROTECT does are:

• Prevents creation of RWX mappings
• Prevents creation of RX anonymous mappings
• Prevents making a non-executable mapping executable
• Prevents making an RX mapping writable with the exception of performing relocations on a non-PIC library

Deterministic shouldn't change the behavior of Firefox itself in a way that would violate any of these. My guess is you're linking in a library which for some reason tries to create an RWX mapping. But given that the current ESR breaks due to creating RWX mappings for JIT, I haven't even played with it myself.

[yawning]

It's not firefox that's crashing, it's the launcher.

mprotect(0x52fb4b3000, 15585280, PROT_READ|PROT_WRITE) = -1 EACCES (Permission denied)
/home/yawning/.local/bin/sandboxed-tor-browser-0.0.2: error while loading shared libraries: cannot make segment writable for relocation: Permission denied
exit_group(127)                         = ?

[yawning]

And scanelf reports: TEXTREL /home/yawning/.local/bin/sandboxed-tor-browser-0.0.2

Since the binaries I build locally don't have this issue, I'm inclined to thing something is hosed elsewhere....

[yawning]

​https://github.com/golang/go/commit/53aec79ce05cd5eff1c8f5576b553d3c429227c3

This is not in any released Go version as of this date.

[cypherpunks]

Replying to yawning:

It's not firefox that's crashing, it's the launcher.

mprotect(0x52fb4b3000, 15585280, PROT_READ|PROT_WRITE) = -1 EACCES (Permission denied)
/home/yawning/.local/bin/sandboxed-tor-browser-0.0.2: error while loading shared libraries: cannot make segment writable for relocation: Permission denied
exit_group(127)                         = ?

What was 0x52fb4b3000 referring to in that trace? It had to have been a library or executable or something which was originally mapped as PROT_READ|PROT_EXEC, but what?

EDIT: Nevermind, I didn't see the link above.

[yawning]

This might have solved itself, it might not. It's basically moot because I don't pay for grsec, and people that do can either wait till the launcher gets built with a new enough Go, or set the fs attributes to work around this issue.