hello,
the Arch Linux Go packaging guidelines[0] currently suggest this for
building software written in Go:
> export CGO_CPPFLAGS="${CPPFLAGS}"
> export CGO_CFLAGS="${CFLAGS}"
> export CGO_CXXFLAGS="${CXXFLAGS}"
> export CGO_LDFLAGS="${LDFLAGS}"
> export GOFLAGS="-buildmode=pie -trimpath -ldflags=-linkmode=external
-mod=readonly -modcacherw"
>
> # or alternatively you can define some of these flags from the CLI
options
> go build \
> -trimpath \
> -buildmode=pie \
> -mod=readonly \
> -modcacherw \
> -ldflags "-linkmode external -extldflags \"${LDFLAGS}\"" \
> .
[0]: https://wiki.archlinux.org/title/Go_package_guidelines
There's also section "2.2.2 Supporting debug packages" which contradicts
the previous section.
## Suggestion
I'd like to propose changing this to something like:
> prepare() {
> cd ${pkgname}-${pkgver}
> go mod download
> }
>
> build() {
> cd ${pkgname}-${pkgver}
> go build .
> }
>
> package() {
> cd ${pkgname}-${pkgver}
> install -Dm0755 -t "${pkgdir}/usr/bin/" "${pkgname}"
> }
Plus any extra flags (for example for debug packages to work, if any are
needed at all - there's a note about this towards the end of this
essay). Instead of suggesting two (three) different approaches, the
packaging guidelines should endorse argv over environment variables (how
to set them with environment variables can still be documented in a
later section of the guideline). The reason I'm suggesting this:
## Passing flags over argv
Setting these options through environment variables is for cases when
`go` isn't executed directly by our PKGBUILD, but instead by some
indirection like a Makefile. Makefiles are more popular in Go projects
than they are in e.g. Rust projects, but presumably because for many
years (10+) there was no analogous to `env!("CARGO_PKG_VERSION")` to
embed a version string into the binary for --version output.
Since almost exactly two years ago, in Go 1.18 released March 2022,
there's now `runtime/debug.ReadBuildInfo` which gives you a reference to
an embedded struct that contains a version string[1].
[1]: https://pkg.go.dev/runtime/debug#ReadBuildInfo
Hopefully more Go projects are going to favor this in the future over
custom build scripts and passing `-X main.Version=...` with output from
`git describe --tags`. If this catches on, people might think of `go
build` more like they currently think of `cargo build` and I think the
Go package guideline should encourage this.
Not just for Go but for software in general, using `git describe` should
be considered an anti-pattern. In the way the Arch Linux build system
currently works, only the checked out files are authenticated and pinned
by sha256sums= and friends, but `git describe` explicitly works on
unauthenticated git objects in `.git/`. I've published a writeup on how
to take advantage of this on the reproducible builds list in September
2023[2].
[2]:
https://lists.reproducible-builds.org/pipermail/rb-general/2023-September/003075.html
## Using the Go native Linker
Binaries built by the Go compiler have been reproducible for a long
time, however Go binaries built by Arch Linux usually aren't. This has
led to some confusion, with bug reports to upstreams of Go software
because it wasn't obvious that the package not being reproducible in
this case isn't a problem in upstream's source code, but the way Arch
Linux compiles it.
Arch Linux generally prefers binaries with hardening flags enabled[3]
and therefore explicitly opts into a non-default linker (Cgo), but it
seems to be the unpopular choice. Cgo seems to have less support than
normal Go on Linux (evidently, since Cgo has been known to have
reproducible build issues for years now). Other Linux distributions seem
to stick to normal Go too, Nix has Cgo off by default[4] and searching
through nixpkgs for "buildGoModule" yields about 2k results, searching
for "CGO_ENABLED" has 105 results, with more than half being
"CGO_ENABLED=0" though. Alpine Linux only sets GOFLAGS globally[5]
(which Arch Linux currently doesn't), searching for `rg -l --multiline
'\tgo.*build'` in aports matches 356 files, `rg -l CGO_ENABLED=0`
matches 23 files and `rg -l CGO_ENABLED=1` matches 18 files.
[3]: https://github.com/jvoisin/compiler-flags-distro
[4]:
https://github.com/NixOS/nixpkgs/blob/b081342f1c16e4cbe4f40f139bbdda1475ea306a/pkgs/build-support/go/module.nix
[5]: https://git.alpinelinux.org/abuild/tree/default.conf?h=3.12.0#n5
The global GOFLAGS as specified in Alpine Linux are:
> export GOFLAGS="-buildmode=pie -modcacherw -trimpath -buildvcs=false"
Which we could consider setting globally too, like we do with RUSTFLAGS.
Figuring out what Debian does was somewhat challenging, their
integration with the go build system is called dh-golang[6], they seem
to set CGO_ENABLED=1 only when cross-compiling, with go >= 1.13
(released 2019) they seem to build with `go install -trimpath ...` and
no further GOFLAGS environment variable.
[6]:
https://salsa.debian.org/go-team/packages/dh-golang/-/blob/debian/sid/lib/Debian/Debhelper/Buildsystem/golang.pm?ref_type=heads
I understand the concern of Go possibly being more prone to ROP-style
exploits when 1) built with the native linker and 2) used with e.g. a
vulnerable version of libgit2, however, as of 2024, there have been
barely any memory-corruption based exploits for Go software.
## Motivation
- Most of our Go software is currently not reproducible due to Cgo,
including core/libcap, which is the last unreproducible package in
docker.io/library/archlinux
- The barrier for packaging Go in Arch Linux is currently somewhat high
(compared to e.g. packaging Rust), the guideline requires too much
interpretation and could be improved
- Quirks that are only needed for old Go projects (like 2.1.1) should be
listed towards the end instead of being the first code block in the
guideline
---
cheers,
kpcyrd
