Opened 5 years ago

Closed 5 years ago

#5690 closed feature request (wontfix)

Enable RTS opts by default with security warning

Reported by: EyalLotem Owned by:
Priority: normal Milestone:
Component: Compiler Version: 7.2.1
Keywords: Cc:
Operating System: Unknown/Multiple Architecture: Unknown/Multiple
Type of failure: None/Unknown Test Case:
Blocked By: Blocking:
Related Tickets: Differential Rev(s):
Wiki Page:


RTS options have security problems. However, disabling them has a lot of downsides.

I propose enabling them by default, with a message like:

"Warning: RTS options are enabled. This has the security implications explained by http://.... To disable RTS options, use -disable-rtsopts. To suppress this warning, use -enable-rtsopts."

This would allow everyone to ignore the warning while in development, or explicitly enable rts opts as they do now. Security-minded projects will not be likely to forget to disable the RTS opts given this warning.

Change History (2)

comment:1 Changed 5 years ago by simonmar

difficulty: Unknown

We have relaxed the restrictions a lot in 7.4.1:

commit 8c7ad0bd5bf1e7f62f44784cc889e8ee585b8d08

Author: Duncan Coutts <>
Date:   Thu Oct 27 13:26:15 2011 +0100

    Change what +RTS options are available by default
    Ticket #3910 originally pointed out that the RTS options are a potential
    security problem. For example the -t -s or -S flags can be used to
    overwrite files. This would be bad in the context of CGI scripts or
    setuid binaries. So we introduced a system where +RTS processing is more
    or less disabled unless you pass the -rtsopts flag at link time.
    This scheme is safe enough but it also really annoies users. They have
    to use -rtsopts in many circumstances: with -threaded to use -N, with
    -eventlog to use -l, with -prof to use any of the profiling flags. Many
    users just set -rtsopts globally or in project .cabal files. Apart from
    annoying users it reduces security because it means that deployed
    binaries will have all RTS options enabled rather than just profiling
    This patch relaxes the set of RTS options that are available in the
    default -rtsopts=some case. For "deployment" ways like vanilla and
    -threaded we remain quite conservative. Only --info -? --help are
    allowed for vanilla. For -threaded, -N and -N<x> are allowed with a
    check that x <= num cpus.
    For "developer" ways like -debug, -eventlog, -prof, we allow all the
    options that are special to that way. Some of these allow writing files,
    but the file written is not directly under the control of the attacker.
    For the setuid case (where the attacker would have control over binary
    name, current dir, local symlinks etc) we check if the process is
    running setuid/setgid and refuse all RTS option processing. Users would
    need to use -rtsopts=all in this case.
    We are making the assumption that developers will not deploy binaries
    built in the -debug, -eventlog, -prof ways. And even if they do, the
    damage should be limited to DOS, information disclosure and writing
    files like <progname>.eventlog, not arbitrary files.

 rts/RtsFlags.c |  131 +++++++++++++++++++++++++++++++++++++++++++++++---------
 1 files changed, 110 insertions(+), 21 deletions(-)

comment:2 Changed 5 years ago by simonmar

Resolution: wontfix
Status: newclosed

I don't think emitting a warning by default is the right approach. If others feel differently please feel free to gang up and sign a petition :)

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