plugin: add test (was encoding/asn1 error when using plugin)

[fsenart]

Please answer these questions before submitting your issue. Thanks!

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

go version go1.8beta2 linux/amd64

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

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/fsenart/projects"
GORACE=""
GOROOT="/home/fsenart/tools/go"
GOTOOLDIR="/home/fsenart/tools/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build746500890=/tmp/go-build -gno-record-gcc-switches"
CXX="g++"
CGO_ENABLED="1"
PKG_CONFIG="pkg-config"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"

What did you do?

If possible, provide a recipe for reproducing the error.
A complete runnable program is good.
A link on play.golang.org is best.

// main.go

package main

import (
	"plugin"
	"reflect"
)

func main() {
	p, err := plugin.Open("plugin.so")
	if err != nil {
		panic(err)
	}
	f, err := p.Lookup("F")
	if err != nil {
		panic(err)
	}

	// f.(func())()
	reflect.ValueOf(f).Call(nil)
}

// plugin.go

package main

import "C"
import "net/http"

func F() {
	_, err := http.Get("https://example.com")
	if err != nil {
		panic(err)
	}
}

# Makefile

test: build
	@./main

build: clean
	@go build -buildmode=plugin -o plugin.so plugin.go
	@go build -o main main.go

clean:
	@rm -rf main *.so

What did you expect to see?

I don't expect any panic to happen.

What did you see instead?

I see a panic happen.

panic: Get https://example.com: tls: failed to parse certificate from server: asn1: structure error: tags don't match (4 vs {class:0 tag:16 length:1242 isCompound:true}) {optional:false explicit:false application:false defaultValue:<nil> tag:<nil> stringType:0 timeType:0 set:false omitEmpty:false} RawContent @4

goroutine 1 [running]:
plugin/unnamed-4ad3198f73971e7223d350ce7ae956cd80d817d9.F()
	/home/fsenart/projects/src/github.com/alsanium/issue_asn1/plugin.go:9 +0x65
reflect.Value.call(0x4d3820, 0xc42000f728, 0x13, 0x4ef099, 0x4, 0x0, 0x0, 0x0, 0xc42000c2e0, 0x4d3820, ...)
	/home/fsenart/tools/go/src/reflect/value.go:434 +0x91f
reflect.Value.Call(0x4d3820, 0xc42000f728, 0x13, 0x0, 0x0, 0x0, 0xc42004df68, 0x4be551, 0x0)
	/home/fsenart/tools/go/src/reflect/value.go:302 +0xa4
main.main()
	/home/fsenart/projects/src/github.com/alsanium/issue_asn1/main.go:19 +0xed
Makefile:2: recipe for target 'test' failed

---

Observations

• If I don't use the reflect package, and instead make type assertion manually, then no error happens.

  f.(func())()
  // reflect.ValueOf(f).Call(nil)

• If I don't use the plugin package, then no error happens.

  package main
  
  import (
      "net/http"
      "reflect"
  )
  
  var f interface{} = func() {
      _, err := http.Get("https://example.com")
      if err != nil {
          panic(err)
      }
  }
  
  func main() {
      //f.(func())()
      reflect.ValueOf(f).Call(nil)
  }

[bradfitz]

/cc @crawshaw @ianlancetaylor

[bradfitz]

Probably too late for a Go 1.8 fix, but maybe a point release.

[fsenart]

OK. THIS IS WEIRD.

After more investigation, it seems not even related to the reflect package.

The error happens if you import any package when using the plugin package.
For example (plugin.go as above):

// main.go

package main

import (
	"fmt" // you can import any package (fails with fmt, log, json, etc.)
	"plugin"
)

func main() {
	fmt.Print() // dummy print for the import statement

	p, err := plugin.Open("plugin.so")
	if err != nil {
		panic(err)
	}
	f, err := p.Lookup("F")
	if err != nil {
		panic(err)
	}

	f.(func())()
}

PS: I don't know what should be the issue title!

[stefanahman]

Getting the same error using https://github.com/eawsy/aws-lambda-go-shim library.
After more investigation and reading this thread, I noticed the plugin import in this file.

[fsenart]

@stefanahman we effectively use go plugins in this project and the issue is related to the fact that we have other imports than plugin in the referenced file (cf. above comment).

@bradfitz at the time I've opened the issue, I agree with you that the problem was very special and happen in rare cases and Go1.8Maybe milestone was ok.
But considering my last comment, you must notice that as soon as any package is imported along with the plugin package then all SSL requests fail. Isn't it a major issue to be fixed before the release of 1.8? Can you please reconsider the milestone, taking into account the new elements?

[crawshaw]

Importing package plugin into a binary switches the linker to the dynamic linking codepath. Presumably that is triggering something which causes type-handling problems.

(I won't have access to a linux machine to investigate this until tomorrow.)

[cristim]

@fsenart, @bradfitz IMHO having the new plugin feature break TLS when there are any other imports makes it pretty useless for a lot of web backend use cases, so I think 1.8 shouldn't be released before this issue is fixed.

[bradfitz]

If we stopped the release train for every bug, we'd never ship.

Plugins are a new part of Go 1.8 anyway. Expect some rough edges. For instance, we disabled them entirely on Mac at the last second, and they don't work on Windows. A few more bugs are expected. That's what point releases are for.

[cristim]

@bradfitz if you mentioned all that it sounds reasonable, I was just under the impression that the plugin feature was a bit more mature than that.

[schickling]

Same issue here. Thanks for investigating @fsenart 👍