Description
What version of Go are you using (go version
)?
$ go version go version go1.17.8 linux/amd64
Does this issue reproduce with the latest release?
Yes, as this is library related using version:
golang.org/x/crypto v0.0.0-20220321153916-2c7772ba3064
I can confirm the issue also happens with previous versions:
golang.org/x/crypto@v0.0.0-20220315160706-3147a52a75dd
What operating system and processor architecture are you using (go env
)?
go env
Output
$ go env GO111MODULE="" GOARCH="amd64" GOBIN="" GOCACHE="/home/USER/.cache/go-build" GOENV="/home/USER/.config/go/env" GOEXE="" GOEXPERIMENT="" GOFLAGS="" GOHOSTARCH="amd64" GOHOSTOS="linux" GOINSECURE="" GOMODCACHE="/home/USER/go/pkg/mod" GONOPROXY="" GONOSUMDB="" GOOS="linux" GOPATH="/home/USER/go" GOPRIVATE="" GOPROXY="https://proxy.golang.org,direct" GOROOT="/usr/local/go" GOSUMDB="sum.golang.org" GOTMPDIR="" GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64" GOVCS="" GOVERSION="go1.17.8" GCCGO="gccgo" AR="ar" CC="gcc" CXX="g++" CGO_ENABLED="1" 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 -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build762703969=/tmp/go-build -gno-record-gcc-switches"
What did you do?
The application implements a golang ssh transport that hangs indefinitely at ssh.Dial
every so often.
The current timeout is set to 30 seconds, which ssh.Dial
does not uphold (https://github.com/fluxcd/source-controller/blob/main/pkg/git/libgit2/managed/ssh.go#L251-L255 https://github.com/fluxcd/source-controller/blob/main/pkg/git/libgit2/managed/init.go#L30).
This is a low concurrency (2-4 parallel workers) application which creates multiple ssh connections to execute simple git operations.
The ssh.Dial
uses the ssh.ClientConfig
as below:
ssh.ClientConfig{
User: username,
Auth: []ssh.AuthMethod{ssh.PublicKeys(key)},
Timeout: 30 * time.Second,
}
Actual code can be seen at:
https://github.com/fluxcd/source-controller/blob/main/pkg/git/libgit2/managed/ssh.go#L166
What did you expect to see?
The ssh.Dial
operation error if the Dial operation took longer than the pre-configured timeout.
What did you see instead?
The goroutine hangs indefinitely. pprof
shows the culprit being:
goroutine 25748 [select, 50 minutes]:
golang.org/x/crypto/ssh.(*handshakeTransport).kexLoop(0xc0003398c0)
golang.org/x/crypto@v0.0.0-20220321153916-2c7772ba3064/ssh/handshake.go:268 +0x485
created by golang.org/x/crypto/ssh.newClientTransport
golang.org/x/crypto@v0.0.0-20220321153916-2c7772ba3064/ssh/handshake.go:135 +0x23d