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runtime: enforce standard descriptors are open on initialization #60641

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rolandshoemaker opened this issue Jun 6, 2023 · 8 comments
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compiler/runtime Issues related to the Go compiler and/or runtime. FrozenDueToAge Proposal Proposal-Accepted
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@rolandshoemaker
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As of CL 501223, under various circumstances we enforce that when the runtime initializes, the standard file descriptors (0, 1, 2) are open and if they are not attempt to open them, pointing to /dev/null. This negates a class of privilege escalation vulnerabilities.

I propose that we always enforce this behavior, regardless of the SUID/SGID status of a program. Ignoring the dangerous behavior this can enable, it also seems confusing on the face that a program could be executed and os.Std{in,out,err} could be closed, or point to unexpected file descriptors if the program opens files itself, without a simple way for the program to determine this itself.

Enforcing these descriptors are open makes programs safe by default, and makes the behavior of a program much more easy to reason about without deep knowledge about the mechanisms of the os.Std{in,out,err} abstractions and unix file descriptor inheritance and precedence semantics.

Rust already enforces this behavior across the board: https://github.com/rust-lang/rust/blob/3572d7451d1062e8bccf310af6bbf6255091d296/library/std/src/sys/unix/mod.rs#L81-L164, rust-lang/rust#75295.

@gopherbot gopherbot added this to the Proposal milestone Jun 6, 2023
@prattmic
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prattmic commented Jun 6, 2023

I can imagine scenarios where having the runtime try to open a file would be problematic, such as when the program runs in any empty mount namespace (/dev/null doesn't exist) or in a seccomp sandbox that disallows open.

But even in those cases, it should be straightforward to make the parent process ensure that it passes a pipe to nowhere or something to bypass this behavior. Thus, I have no complaints.

@prattmic prattmic added the compiler/runtime Issues related to the Go compiler and/or runtime. label Jun 6, 2023
@thediveo
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thediveo commented Jun 6, 2023

if you happen to come across some "Dirty Harry" seccomp profiles you don't get any chance after attempting to open /dev/null because they terminate instead of deny. Shoot first, ask later.

@prattmic
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prattmic commented Jun 6, 2023

It turns out that we've been unconditionally opening a file at startup since https://go.dev/cl/170858, so the seccomp issue wouldn't be new.

@ianlancetaylor ianlancetaylor moved this to Incoming in Proposals Jun 6, 2023
@thediveo
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thediveo commented Jun 7, 2023

thanks for the information, so nothing to worry about.

@rsc
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rsc commented Jun 28, 2023

This proposal has been added to the active column of the proposals project
and will now be reviewed at the weekly proposal review meetings.
— rsc for the proposal review group

@rsc rsc moved this from Incoming to Active in Proposals Jun 28, 2023
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rsc commented Jul 5, 2023

Based on the discussion above, this proposal seems like a likely accept.
— rsc for the proposal review group

@rsc rsc moved this from Active to Likely Accept in Proposals Jul 5, 2023
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rsc commented Jul 12, 2023

No change in consensus, so accepted. 🎉
This issue now tracks the work of implementing the proposal.
— rsc for the proposal review group

@rsc rsc moved this from Likely Accept to Accepted in Proposals Jul 12, 2023
@rsc rsc changed the title proposal: runtime: enforce standard descriptors are open on initialization runtime: enforce standard descriptors are open on initialization Jul 12, 2023
@rsc rsc modified the milestones: Proposal, Backlog Jul 12, 2023
@gopherbot
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Change https://go.dev/cl/509020 mentions this issue: runtime: enforce standard file descriptors open on init on unix

@mknyszek mknyszek moved this to In Progress in Go Compiler / Runtime Jul 19, 2023
@github-project-automation github-project-automation bot moved this from In Progress to Done in Go Compiler / Runtime Jul 25, 2023
@dmitshur dmitshur modified the milestones: Backlog, Go1.22 Jul 25, 2023
@golang golang locked and limited conversation to collaborators Jul 24, 2024
@rsc rsc removed this from Proposals Jul 25, 2024
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