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runtime: feature request: Support for ASLR with the heap #27583

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lattera opened this issue Sep 9, 2018 · 13 comments
Open

runtime: feature request: Support for ASLR with the heap #27583

lattera opened this issue Sep 9, 2018 · 13 comments
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compiler/runtime Issues related to the Go compiler and/or runtime. NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.
Milestone
Backlog

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@lattera
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lattera commented Sep 9, 2018

Please answer these questions before submitting your issue. Thanks!

What version of Go are you using (go version)?

go version go1.11 freebsd/amd64

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

GOARCH="amd64"
GOBIN=""
GOCACHE="/home/shawn/.cache/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="freebsd"
GOOS="freebsd"
GOPATH="/home/shawn/go"
GOPROXY=""
GORACE=""
GOROOT="/usr/local/go"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/freebsd_amd64"
GCCGO="gccgo"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build851003260=/tmp/go-build -gno-record-gcc-switches"

What did you do?

Run a go application

What did you expect to see?

The heap mapped at a non-fixed location.

What did you see instead?

The heap mapped at a fixed location.

More information:

I've read through a previous discussion in 2012 about golang's use of deterministic memory allocations here: https://groups.google.com/forum/#!msg/golang-nuts/Jd9tlNc6jUE/qp2oyfEEfjQJ

Back then, -buildmode=pie didn't exist back then, so I figured a revisit of the topic might be warranted.

Go 1.11 introduced -buildmode=pie for FreeBSD, which HardenedBSD is able to take advantage of, given HBSD's PaX ASLR implementation. HardenedBSD is a hardened derivative of FreeBSD.

When applying -buildmode=pie with gitea, I wanted to verify that golang was able to take full advantage of HardenedBSD's robust ASLR implementation. I noticed a fixed mapping at 0xc000000000. I restarted the process, looked at the memory mappings again (procstat -v $PID) and saw 0xc000000000 again. Grepping through the golang 1.11 codebase revealed that Go allocates its heap at a fixed address, starting at 0xc000000000.

With the heap being allocated at a fixed mapping, golang applications are still not able to really utilize ASLR. Thus, -buildmode=pie is moot.

Given that the reason to implement PIE support is to take advantage of ASLR, I'm curious if perhaps updating the heap management code for ASLR support was overlooked. Or perhaps it wasn't, and this is deliberate. Or perhaps a totally different reason. Either way, could someone shed some light on this?

I submitted a post on the golang-nuts mailing list, asking the same questions. It can be found here: https://groups.google.com/d/msg/golang-nuts/pAGcmRA_V5s/2NnOPDEcBgAJ
@randall77
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@aclements

@ianlancetaylor ianlancetaylor changed the title Feature request: Support for ASLR with the heap runtime: feature request: Support for ASLR with the heap Sep 9, 2018
@ianlancetaylor ianlancetaylor added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Sep 9, 2018
@ianlancetaylor ianlancetaylor added this to the Go1.12 milestone Sep 9, 2018
@fntlnz fntlnz mentioned this issue Oct 23, 2018
Open
@aclements aclements modified the milestones: Go1.12, Go1.13 Jan 8, 2019
@randall77 randall77 modified the milestones: Go1.13, Go1.14 Jun 3, 2019
@rsc rsc modified the milestones: Go1.14, Backlog Oct 9, 2019
@lattera
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lattera commented Dec 29, 2021

Just checking in. Any movement on this? I'm still seeing that the heap is mapped at a fixed address (0xc000000000)

@ianlancetaylor
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Nothing has changed.

A randomly placed heap requires completely different code from support for Position Independent Executables. And fixed location of executable code is riskier than fixed location of non-executable data. I say this not to say that a randomly placed heap is a bad idea, but merely to observe that -buildmode=pie doesn't really have anything to do with a randomly placed heap, despite their both being based on the same underlying idea.

@lattera
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lattera commented Dec 29, 2021

I'm of the opinion that non-executable data is still executable (read: data-only attacks causing the code to take different code branches.) Fuzzers show this concept in action. Machines are weird. ;-)

In order for ASLR to be effective, everything's gotta be randomized. My original statement from years back about PIE is only tangentially related. It just doesn't make sense to support PIE without also randomizing the heap. (Not that I'm arguing to remove existing PIE support--the opposite: to include heap randomization.)

@ianlancetaylor
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Since Go programs are always multi-threaded, the contents of the heap are already somewhat randomized. I can't agree that it doesn't make sense to support PIE without randomizing the heap address.

But I'm not opposed to this, it's just that somebody has to do the work. Want to volunteer?

@lattera
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lattera commented Dec 29, 2021

I'd love to, but my spare time's focused on HardenedBSD. What I can do, though, is ping the HardenedBSD community to see if anyone's interested in volunteering. I'll report back if I can find a volunteer.

@theLOICofFRANCE
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Followed.
I hope that one of the 65 members of @goland or @google can take care of it.

Thanks.

@walterjwhite
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I'd also like to voice support for this. I'm on FreeBSD and enabled ASLR just to find that my go programs don't run. Fortunately though, I can temporarily disable ASLR without rebooting:

sysctl kern.elf64.aslr.enable=0
sysctl kern.elf32.aslr.enable=0

@lattera
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lattera commented Mar 3, 2022

I'd also like to voice support for this. I'm on FreeBSD and enabled ASLR just to find that my go programs don't run. Fortunately though, I can temporarily disable ASLR without rebooting:

sysctl kern.elf64.aslr.enable=0 sysctl kern.elf32.aslr.enable=0

That would likely be a bug in FreeBSD's AS{L}R implementation. golang applications work fine with the PaX-inspired ASLR implementation in HardenedBSD.

@emaste
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emaste commented Mar 3, 2022

That would likely be a bug ...

I have no problem running go programs on FreeBSD with ASLR enabled. We'd need some more details from @walterjwhite, but should move this discussion / bug report somewhere other than this feature request issue.

@walterjwhite
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I suppose you're right.

I have some applications working with no issues in go, but I have another one which uses chromedpexecutor that drives my browser that doesn't work:

fatal error: too many address space collisions for -race mode

runtime stack:
runtime.throw({0xcdaec8, 0x30})
/usr/local/go/src/runtime/panic.go:1198 +0x74 fp=0x7fffff27ffa8 sp=0x7fffff27ff78 pc=0x47d134
runtime.(*mheap).sysAlloc(0x1172e80, 0x400000)
/usr/local/go/src/runtime/malloc.go:686 +0x6c7 fp=0x7fffff280040 sp=0x7fffff27ffa8 pc=0x452967
runtime.(*mheap).grow(0x1172e80, 0x1)
/usr/local/go/src/runtime/mheap.go:1347 +0x85 fp=0x7fffff2800b0 sp=0x7fffff280040 pc=0x46eec5
runtime.(*mheap).allocSpan(0x1172e80, 0x1, 0x0, 0x2e)
/usr/local/go/src/runtime/mheap.go:1179 +0x1bd fp=0x7fffff280120 sp=0x7fffff2800b0 pc=0x46e99d
runtime.(*mheap).alloc.func1()
/usr/local/go/src/runtime/mheap.go:913 +0x8c fp=0x7fffff280170 sp=0x7fffff280120 pc=0x46e3ec
runtime.(*mheap).alloc(0x1172e80, 0x1, 0x2e, 0x1)
/usr/local/go/src/runtime/mheap.go:907 +0x8e fp=0x7fffff2801c0 sp=0x7fffff280170 pc=0x46e2ce
runtime.(*mcentral).grow(0x1185348)
/usr/local/go/src/runtime/mcentral.go:241 +0x79 fp=0x7fffff280210 sp=0x7fffff2801c0 pc=0x45eaf9
runtime.(*mcentral).cacheSpan(0x1185348)
/usr/local/go/src/runtime/mcentral.go:161 +0x7e5 fp=0x7fffff280290 sp=0x7fffff280210 pc=0x45e905
runtime.(*mcache).refill(0x80afa8108, 0x2e)
/usr/local/go/src/runtime/mcache.go:162 +0xaa fp=0x7fffff2802d8 sp=0x7fffff280290 pc=0x45d92a
runtime.(*mcache).nextFree(0x80afa8108, 0x2e)
/usr/local/go/src/runtime/malloc.go:880 +0x8d fp=0x7fffff280318 sp=0x7fffff2802d8 pc=0x452a0d
runtime.mallocgc(0x188, 0xcbb3e0, 0x1)
/usr/local/go/src/runtime/malloc.go:1071 +0x530 fp=0x7fffff2803a8 sp=0x7fffff280318 pc=0x4530f0
runtime.newobject(0xcbb3e0)
/usr/local/go/src/runtime/malloc.go:1228 +0x38 fp=0x7fffff2803d8 sp=0x7fffff2803a8 pc=0x453718
runtime.malg(0x8000)
/usr/local/go/src/runtime/proc.go:4220 +0x31 fp=0x7fffff280418 sp=0x7fffff2803d8 pc=0x489131
runtime.mpreinit(0x115a0e0)
/usr/local/go/src/runtime/os_freebsd.go:295 +0x29 fp=0x7fffff280438 sp=0x7fffff280418 pc=0x4795c9
runtime.mcommoninit(0x115a0e0, 0xffffffffffffffff)
/usr/local/go/src/runtime/proc.go:803 +0x13a fp=0x7fffff280480 sp=0x7fffff280438 pc=0x4814ba
runtime.schedinit()
/usr/local/go/src/runtime/proc.go:691 +0xcf fp=0x7fffff2804e0 sp=0x7fffff280480 pc=0x480fef
runtime.rt0_go()
/usr/local/go/src/runtime/asm_amd64.s:212 +0x125 fp=0x7fffff2804e8 sp=0x7fffff2804e0 pc=0x4b0a65

@aclements
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@walterjwhite , mind filing a new issue? It looks like you have some compatibility issue between the Go runtime and ASLR, while this issue is about enabling randomization of the Go heap, which is not about correctness.

@walterjwhite
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#51523

@ianlancetaylor ianlancetaylor mentioned this issue Mar 7, 2022
Closed
@gopherbot gopherbot added the compiler/runtime Issues related to the Go compiler and/or runtime. label Jul 7, 2022
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compiler/runtime Issues related to the Go compiler and/or runtime. NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.
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Go Compiler / Runtime
Status: Triage Backlog
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@rsc @walterjwhite @lattera @emaste @aclements @ianlancetaylor @theLOICofFRANCE @randall77 @gopherbot