cmd/hakurei: terminate specified instance

This is theoretically susceptible to the PID race, but such an event is statistically impossible, and not exploitable in the intended use case, regardless.

Signed-off-by: Ophestra <cat@gensokyo.uk>

cmd/dist/comp/_hakurei

@@ -36,6 +36,11 @@ _hakurei_show() {
     'files:files:__hakurei_files'
 }
 
+_hakurei_kill() {
+  _alternative \
+    'instances:domains:__hakurei_instances'
+}
+
 __hakurei_files() {
   _files -g "*.(json|hakurei)"
   return $?
@@ -60,6 +65,7 @@ __hakurei_instances() {
     "run:Load and start container from configuration file"
     "exec:Configure and start a permissive container"
     "show:Show live or local instance configuration"
+    "kill:Terminate an active instance"
     "ps:List active instances"
     "version:Display version information"
     "license:Show full license text"

cmd/hakurei/command.go

@@ -11,6 +11,7 @@ import (
 	"os/user"
 	"strconv"
 	"sync"
+	"syscall"
 	"time"
 
 	"hakurei.app/check"
@@ -372,6 +373,23 @@ func buildCommand(ctx context.Context, msg message.Msg, early *earlyHardeningErr
 			Flag(&flagNoStore, "no-store", command.BoolFlag(false), "Do not attempt to match from active instances")
 	}
 
+	c.NewCommand("kill", "Terminate an active instance", func(args []string) error {
+		if len(args) != 1 {
+			log.Fatal("kill requires 1 argument")
+		}
+
+		var sc hst.Paths
+		env.CopyPaths().Copy(&sc, new(outcome.Hsu).MustID(nil))
+		entry := tryIdentifier(msg, args[0], outcome.NewStore(&sc))
+		if entry == nil {
+			log.Fatalf("%q does not match any active instance", args[0])
+		}
+		if err := syscall.Kill(entry.PID, syscall.SIGTERM); err != nil {
+			log.Fatalf("cannot terminate %s: %v", entry.ID.String(), err)
+		}
+		return errSuccess
+	})
+
 	{
 		var flagShort bool
 		c.NewCommand("ps", "List active instances", func(args []string) error {

cmd/hakurei/command_test.go

@@ -25,6 +25,7 @@ commands:
     run         Load and start container from configuration file
     exec        Configure and start a permissive container
     show        Show live or local instance configuration
+    kill        Terminate an active instance
     ps          List active instances
     version     Display version information
     license     Show full license text