pledge: DNS in Go program without CGO fails on setsockopt

[shoenig]

I've been messing around with pledge.com (amazing by the way, thank you!), and ran into a case where AFAICT no promise is enough to enable DNS in a Go program compiled without CGO enabled. Ran into this while trying to run the traefik webserver, but here's a toy example for reproduction.

program

package main

import (
	"fmt"	
	"net"
)

func main() {
	addrs, err := net.LookupHost("example.com")
	fmt.Println("addrs:", addrs, "err", err)
}

building

CGO_ENABLED=0 go build

run normally

./dnstest 
addrs: [93.184.216.34 2606:2800:220:1:248:1893:25c8:1946] err <nil>

run with minimal(?) promises

pledge-1.7.com -p 'stdio rpath inet unix dns' ./dnstest
SIGSYS: bad system call
PC=0x4026ae m=3 sigcode=1

goroutine 6 [syscall]:
syscall.Syscall6(0xc0000c4120?, 0x47f58b?, 0x7f7367b12800?, 0xc0000c4138?, 0x4128c6?, 0x7f7367b12a00?, 0x7f736796abb8?)
	/opt/google/go/src/syscall/syscall_linux.go:90 +0x36 fp=0xc0000c40e8 sp=0xc0000c4060 pc=0x47fcd6
syscall.setsockopt(0xc0000c41a0?, 0x4133f0?, 0xc0000c4180?, 0x4bbacb?, 0x7f7367d09fff?)
	/opt/google/go/src/syscall/zsyscall_linux_amd64.go:1470 +0x39 fp=0xc0000c4138 sp=0xc0000c40e8 pc=0x47f499
syscall.SetsockoptInt(...)
	/opt/google/go/src/syscall/syscall_unix.go:458
net.setDefaultSockopts(0x7f7367b12b00?, 0x7f7367b12a00?, 0xc0000c41e8?, 0x6b?)
	/opt/google/go/src/net/sockopt_linux.go:21 +0xb3 fp=0xc0000c4190 sp=0xc0000c4138 pc=0x4bda13
net.socket({0x510348, 0xc000108000}, {0x4e89ef, 0x3}, 0x2, 0x2, 0x7f736796aaa8?, 0x10?, {0x5104b8, 0x0}, ...)
	/opt/google/go/src/net/sock_posix.go:23 +0x99 fp=0xc0000c4240 sp=0xc0000c4190 pc=0x4bc119
net.internetSocket({0x510348, 0xc000108000}, {0x4e89ef, 0x3}, {0x5104b8, 0x0}, {0x5104b8, 0xc000102060}, 0x4d24a0?, 0x0, ...)
	/opt/google/go/src/net/ipsock_posix.go:142 +0xf8 fp=0xc0000c42c0 sp=0xc0000c4240 pc=0x4b5cf8
net.(*sysDialer).dialUDP(0x5d4c97?, {0x510348?, 0xc000108000?}, 0xc0000c4380?, 0x464825?)
	/opt/google/go/src/net/udpsock_posix.go:206 +0x7d fp=0xc0000c4340 sp=0xc0000c42c0 pc=0x4bf5bd
net.(*sysDialer).dialSingle(0xc000112000, {0x510348, 0xc000108000}, {0x510198?, 0xc000102060})
	/opt/google/go/src/net/dial.go:585 +0x2f4 fp=0xc0000c4410 sp=0xc0000c4340 pc=0x4a64b4
net.(*sysDialer).dialSerial(0xc000112000, {0x510348, 0xc000108000}, {0xc00010a020?, 0x1, 0x7f7367b12900?})
	/opt/google/go/src/net/dial.go:550 +0x312 fp=0xc0000c4518 sp=0xc0000c4410 pc=0x4a5d92
net.(*sysDialer).dialParallel(0x0?, {0x510348?, 0xc000108000?}, {0xc00010a020?, 0xc000108000?, 0x4e8ad8?}, {0x0?, 0x4e89ef?, 0x1?})
	/opt/google/go/src/net/dial.go:451 +0x413 fp=0xc0000c4770 sp=0xc0000c4518 pc=0x4a5333
net.(*Dialer).DialContext(0xc0000c4908, {0x510348, 0xc000108000}, {0x4e89ef, 0x3}, {0xc000018340, 0xd})
	/opt/google/go/src/net/dial.go:428 +0x705 fp=0xc0000c48c0 sp=0xc0000c4770 pc=0x4a4c05
net.(*Resolver).dial(0xc00010a010?, {0x510348?, 0xc000108000?}, {0x4e89ef?, 0x5a6300?}, {0xc000018340?, 0x0?})
	/opt/google/go/src/net/lookup.go:686 +0xa5 fp=0xc0000c4978 sp=0xc0000c48c0 pc=0x4b7d25
net.(*Resolver).exchange(_, {_, _}, {_, _}, {{{0x65, 0x78, 0x61, 0x6d, 0x70, ...}, ...}, ...}, ...)
	/opt/google/go/src/net/dnsclient_unix.go:177 +0x445 fp=0xc0000c5008 sp=0xc0000c4978 pc=0x4a83a5
net.(*Resolver).tryOneName(_, {_, _}, _, {_, _}, _)
	/opt/google/go/src/net/dnsclient_unix.go:277 +0x485 fp=0xc0000c5a38 sp=0xc0000c5008 pc=0x4a96e5
net.(*Resolver).goLookupIPCNAMEOrder.func3.1(0x1?)
	/opt/google/go/src/net/dnsclient_unix.go:638 +0x85 fp=0xc0000c5fc8 sp=0xc0000c5a38 pc=0x4ac565
net.(*Resolver).goLookupIPCNAMEOrder.func3.2()
	/opt/google/go/src/net/dnsclient_unix.go:641 +0x2a fp=0xc0000c5fe0 sp=0xc0000c5fc8 pc=0x4ac4aa
runtime.goexit()
	/opt/google/go/src/runtime/asm_amd64.s:1594 +0x1 fp=0xc0000c5fe8 sp=0xc0000c5fe0 pc=0x461401
created by net.(*Resolver).goLookupIPCNAMEOrder.func3
	/opt/google/go/src/net/dnsclient_unix.go:637 +0x16c

run with all the promises

pledge-1.7.com -p 'stdio rpath inet unix dns wpath cpath dpath flock tty recvfd sendfd fattr proc id exec' ./dnstest
addrs: [] err lookup example.com on 127.0.0.53:53: dial udp 127.0.0.53:53: setsockopt: operation not permitted

pledge is assimilated

file $(which pledge-1.7.com)
/opt/bin/pledge-1.7.com: ELF 64-bit LSB executable, x86-64, version 1 (FreeBSD), for OpenBSD, statically linked, no section header

linux

uname -a
Linux orange 5.19.8-200.fc36.x86_64 #1 SMP PREEMPT_DYNAMIC Thu Sep 8 19:02:21 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux

[jart]

Looks like it needs SOL_SOCKET + SO_BROADCAST. I'm going to add IPPROTO_IPV6 + IPV6_V6ONLY too since that's also referenced.

[jart]

I believe I've fixed the issue. Could you please build make o//tool/build/pledge.com at head and confirm it works so I can cut a release? Thanks for confirming.

The way to troubleshoot these issues normally, particularly when you're using static binaries, is to run the command under strace -ff pledge.com my-go-program.

[shoenig]

It works, thanks!

[jart]

I'll push a new release to https://justine.lol/pledge/ later today.

[shoenig]

I might have one more Go related bug/fix - I spotted a panic where (I think) tgkill couldn't be used by the GC, trying to make a reproduction now.