chore(events/syscall): linux only utils

Signed-off-by: Leonardo Grasso <me@leonardograsso.com>

events/syscall/utils_linux.go

@@ -0,0 +1,59 @@
+// +build linux
+
+package syscall
+
+import (
+	"os/exec"
+	"os/user"
+	"strconv"
+	sys "syscall"
+
+	"github.com/falcosecurity/event-generator/events"
+)
+
+func becameUser(h events.Helper, username string) error {
+	h.Log().WithField("user", username).
+		Info("became user")
+
+	u, err := user.Lookup(username)
+	if err != nil {
+		return err
+	}
+
+	uid, err := strconv.Atoi(u.Uid)
+	if err != nil {
+		return err
+	}
+
+	return sys.Setuid(uid)
+}
+
+func runAsUser(h events.Helper, username string, cmdName string, cmdArgs ...string) error {
+	h.Log().WithField("user", username).
+		WithField("cmdName", cmdName).
+		WithField("cmdArgs", cmdArgs).
+		Info("run command as another user")
+
+	u, err := user.Lookup(username)
+	if err != nil {
+		return err
+	}
+
+	uid, err := strconv.Atoi(u.Uid)
+	if err != nil {
+		return err
+	}
+
+	gid, err := strconv.Atoi(u.Gid)
+	if err != nil {
+		return err
+	}
+
+	cmd := exec.Command(cmdName, cmdArgs...)
+	cmd.SysProcAttr = &sys.SysProcAttr{}
+	cmd.SysProcAttr.Credential = &sys.Credential{
+		Uid: uint32(uid),
+		Gid: uint32(gid),
+	}
+	return cmd.Run()
+}