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cmd/link: support full relro #45681

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Foxboron
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Most Linux distributions today enable PIE and full RELRO on all binaries
to make exploitation harder. When buildmode=pie is used we enable full
relro as that is probably what most people want regardless.

This introduces a negligible startup time for binaries.

https://fedoraproject.org/wiki/Changes/Harden_All_Packages
https://www.redhat.com/en/blog/hardening-elf-binaries-using-relocation-read-only-relro

Related #44480

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@Foxboron Foxboron mentioned this pull request May 13, 2021
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@Foxboron Foxboron force-pushed the morten/full-relro branch from 54b4266 to b85c7f7 Compare May 7, 2022 10:31
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y27988 commented Oct 13, 2022

Why is this feature not merged into the main branch?

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I have failed to followup on this a properly sadly. The review cycle takes a while (understandably) so it doesn't end up super high on my todo list :)

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@nrvnrvn nrvnrvn mentioned this pull request Mar 4, 2023
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@Foxboron Foxboron closed this Nov 1, 2023
gopherbot pushed a commit that referenced this pull request Feb 29, 2024
@nrvnrvn @cherrymui
cmd/link: add option to enable full RELRO for ELF
45b641c 
-bindnow linker option enables full RELRO on ELF targets.

This options defaults to false and preserves
current behavior - partial relro for buildmode=pie.

Also, the following changes were made to align
internal linker's behavior with external ELF linkers:
- GNU_RELRO segment is marked Read-only
- .dynamic is a relro section for partial and full RELRO
- .got is a relro section for partial and full RELRO
- .got.plt is a relro section for full RELRO only

Supersedes #45681 (golang.org/cl/312509)

Change-Id: I51c4ef07b14beceb7cd6fd989f323e45f89a63ca
GitHub-Last-Rev: bc68264
GitHub-Pull-Request: #58869
Reviewed-on: https://go-review.googlesource.com/c/go/+/473495
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>
Run-TryBot: Cherry Mui <[email protected]>
Reviewed-by: Than McIntosh <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
gopherbot pushed a commit that referenced this pull request Mar 14, 2024
@thanm
Revert: "cmd/link: add option to enable full RELRO for ELF"
be58fd0 
This reverts https://go.dev/cl/c/go/+/473495.

Reason for revert: breaks some Google-internal tests.

This revert will be temporary until we can gather more info on the
nature of the failures and hopefully develop an upstream test case,
etc.

Updates #45681.

Change-Id: Ib628ddc53bc5489e4f76c0f4ad809b75e899102c
Reviewed-on: https://go-review.googlesource.com/c/go/+/571415
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>
gopherbot pushed a commit that referenced this pull request Mar 15, 2024
@thanm
cmd/link: support -bindnow option and permit use of "-Wl,-z,now"
88480fa 
This is a partial roll-forward of CL 473495, which was subsequently
reverted. The second half of CL 473495 will appear in a future CL.

In this patch we introduce a new Go linker "-bindnow" command line
flag, and update the Go command to permit the use of the -Wl,-z,now
option, to allow users to produce binaries that have immediate
binding.

Updates #45681.

Change-Id: Idd61b0d6597bcd37b16c343714c55a4ef6dfb534
Reviewed-on: https://go-review.googlesource.com/c/go/+/571416
Reviewed-by: Cherry Mui <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
gopherbot pushed a commit that referenced this pull request Apr 22, 2024
@thanm
cmd/link: move .dynamic and .got sections to relro if applicable
2dddc7e 
This is the second of two CLs to roll forward the changes in CL
473495, which was subsequently reverted.

In this patch we move the .dynamic and .got sections from the writable
data segment to the relro segment if the platform supports relro and
we're producing a PIE binary, and also moves .got.plt into relro if
eager binding is in effect (e.g. -bindnow or -Wl,-z,now).

Updates #45681.

Change-Id: I9f4fba6e825b96d1b5e27fb75844450dd0a650b3
Reviewed-on: https://go-review.googlesource.com/c/go/+/571417
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>
gopherbot pushed a commit that referenced this pull request Apr 25, 2024
@thanm
cmd/link/internal/ld: revised bindnow/relro test for ELF
1ca31ea 
This patch re-enables the portion of the TestElfBindNow test that
verifies that selected sections are in a read-only segment. Turns out
we can't always check for read-only ".got" on all architectures (on
ppc64le for example ".got" will only turn up if there is CGO use), so
always look for readonly ".dynamic", but only look for readonly ".got"
if the section is present.

Updates #45681.

Change-Id: I4687ae3cf9a81818268925e17700170ba34204a7
Reviewed-on: https://go-review.googlesource.com/c/go/+/581115
Reviewed-by: Cherry Mui <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
EthanHeilman pushed a commit to EthanHeilman/go that referenced this pull request Apr 30, 2024
@thanm @EthanHeilman
cmd/link/internal/ld: revised bindnow/relro test for ELF
e3726cd 
This patch re-enables the portion of the TestElfBindNow test that
verifies that selected sections are in a read-only segment. Turns out
we can't always check for read-only ".got" on all architectures (on
ppc64le for example ".got" will only turn up if there is CGO use), so
always look for readonly ".dynamic", but only look for readonly ".got"
if the section is present.

Updates golang#45681.

Change-Id: I4687ae3cf9a81818268925e17700170ba34204a7
Reviewed-on: https://go-review.googlesource.com/c/go/+/581115
Reviewed-by: Cherry Mui <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

Fixes RSA mod overflow timing channel

Addressing review comments

Addresses review comment about newline
gopherbot pushed a commit that referenced this pull request May 10, 2024
@thanm
cmd/link/internal/ld: fix overlapping sections in ELF relro links
a548dee 
This patch fixes a problem with how the .dynamic and .got sections are
handled during PIE linking on ELF targets. These sections were being
given addresses that overlapped with the .data.rel.ro section, which
resulted in binaries that worked correctly but confused the binutils
"strip" tool (which, confusingly, produced non-working stripped output
when used on Go PIE binaries without returning a non-zero exit
status). The new RELRO PIE code path preserves .dynamic and .got as
their own independent sections, while ensuring that they make it into
the RELRO segment. A new test verifies that we can successfully strip
and run Go PIE binaries, and also that we don't wind up with any
sections whose address ranges overlap.

Fixes #67261.
Updates #45681.

Change-Id: If874be05285252a9b074d4a1fc6a4023b9a28b5e
Reviewed-on: https://go-review.googlesource.com/c/go/+/584595
Reviewed-by: Cherry Mui <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
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