helper/seccomp: do not call F_println if not verbose

This (slightly) improves performance.

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

helper/bwrap/seccomp.go

@@ -0,0 +1,90 @@
+package bwrap
+
+import (
+	"fmt"
+	"os"
+
+	"git.gensokyo.uk/security/fortify/helper/seccomp"
+	"git.gensokyo.uk/security/fortify/internal/fmsg"
+)
+
+type SyscallPolicy struct {
+	// disable fortify extensions
+	Compat bool `json:"compat"`
+	// deny development syscalls
+	DenyDevel bool `json:"deny_devel"`
+	// deny multiarch/emulation syscalls
+	Multiarch bool `json:"multiarch"`
+	// allow PER_LINUX32
+	Linux32 bool `json:"linux32"`
+	// allow AF_CAN
+	Can bool `json:"can"`
+	// allow AF_BLUETOOTH
+	Bluetooth bool `json:"bluetooth"`
+}
+
+type seccompBuilder struct {
+	config *Config
+}
+
+func (s *seccompBuilder) Len() int {
+	if s == nil {
+		return 0
+	}
+	return 2
+}
+
+func (s *seccompBuilder) Append(args *[]string, extraFiles *[]*os.File) error {
+	if s == nil {
+		return nil
+	}
+	if f, err := s.config.resolveSeccomp(); err != nil {
+		return err
+	} else {
+		extraFile(args, extraFiles, positionalArgs[Seccomp], f)
+		return nil
+	}
+}
+
+func (c *Config) resolveSeccomp() (*os.File, error) {
+	if c.Syscall == nil {
+		return nil, nil
+	}
+
+	// resolve seccomp filter opts
+	var (
+		opts    seccomp.SyscallOpts
+		optd    []string
+		optCond = [...]struct {
+			v bool
+			o seccomp.SyscallOpts
+			d string
+		}{
+			{!c.Syscall.Compat, seccomp.FlagExt, "fortify"},
+			{!c.UserNS, seccomp.FlagDenyNS, "denyns"},
+			{c.NewSession, seccomp.FlagDenyTTY, "denytty"},
+			{c.Syscall.DenyDevel, seccomp.FlagDenyDevel, "denydevel"},
+			{c.Syscall.Multiarch, seccomp.FlagMultiarch, "multiarch"},
+			{c.Syscall.Linux32, seccomp.FlagLinux32, "linux32"},
+			{c.Syscall.Can, seccomp.FlagCan, "can"},
+			{c.Syscall.Bluetooth, seccomp.FlagBluetooth, "bluetooth"},
+		}
+	)
+	if seccomp.CPrintln != nil {
+		optd = make([]string, 1, len(optCond)+1)
+		optd[0] = "common"
+	}
+	for _, opt := range optCond {
+		if opt.v {
+			opts |= opt.o
+			if fmsg.Verbose() {
+				optd = append(optd, opt.d)
+			}
+		}
+	}
+	if seccomp.CPrintln != nil {
+		seccomp.CPrintln(fmt.Sprintf("seccomp flags: %s", optd))
+	}
+
+	return seccomp.Export(opts)
+}