Ophestra
f443d315ad
The helper interface was messy due to odd context acquisition order. That has changed, so this cleans it up. Signed-off-by: Ophestra <cat@gensokyo.uk>
114 lines
2.5 KiB
Go
114 lines
2.5 KiB
Go
// Package helper runs external helpers with optional sandboxing.
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package helper
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import (
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"context"
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"fmt"
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"io"
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"os"
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"os/exec"
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"slices"
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"syscall"
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"time"
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"git.gensokyo.uk/security/fortify/helper/proc"
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)
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var (
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WaitDelay = 2 * time.Second
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)
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const (
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// FortifyHelper is set to 1 when args fd is enabled and 0 otherwise.
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FortifyHelper = "FORTIFY_HELPER"
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// FortifyStatus is set to 1 when stat fd is enabled and 0 otherwise.
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FortifyStatus = "FORTIFY_STATUS"
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)
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type Helper interface {
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// Start starts the helper process.
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Start() error
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// Wait blocks until Helper exits.
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Wait() error
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fmt.Stringer
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}
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func newHelperCmd(
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ctx context.Context, name string,
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wt io.WriterTo, argF func(argsFd, statFd int) []string,
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extraFiles []*os.File, stat bool,
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) (cmd *helperCmd) {
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cmd = new(helperCmd)
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cmd.ctx = ctx
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cmd.hasStatFd = stat
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cmd.Cmd = commandContext(ctx, name)
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cmd.Cmd.Cancel = func() error { return cmd.Process.Signal(syscall.SIGTERM) }
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cmd.WaitDelay = WaitDelay
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cmd.extraFiles = new(proc.ExtraFilesPre)
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for _, f := range extraFiles {
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_, v := cmd.extraFiles.Append()
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*v = f
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}
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argsFd := -1
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if wt != nil {
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f := proc.NewWriterTo(wt)
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argsFd = int(proc.InitFile(f, cmd.extraFiles))
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cmd.files = append(cmd.files, f)
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cmd.hasArgsFd = true
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}
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cmd.argF = func(statFd int) []string { return argF(argsFd, statFd) }
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return
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}
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// helperCmd wraps Cmd and implements methods shared across all Helper implementations.
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type helperCmd struct {
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// returns an array of arguments passed directly
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// to the helper process
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argF func(statFd int) []string
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// whether argsFd is present
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hasArgsFd bool
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// whether statFd is present
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hasStatFd bool
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// closes statFd
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stat io.Closer
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// deferred extraFiles fulfillment
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files []proc.File
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// passed through to [proc.Fulfill] and [proc.InitFile]
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extraFiles *proc.ExtraFilesPre
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ctx context.Context
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*exec.Cmd
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}
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// finalise sets up the underlying [exec.Cmd] object.
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func (h *helperCmd) finalise() (args []string) {
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h.Env = slices.Grow(h.Env, 2)
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if h.hasArgsFd {
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h.Cmd.Env = append(h.Env, FortifyHelper+"=1")
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} else {
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h.Cmd.Env = append(h.Env, FortifyHelper+"=0")
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}
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statFd := -1
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if h.hasStatFd {
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f := proc.NewStat(&h.stat)
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statFd = int(proc.InitFile(f, h.extraFiles))
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h.files = append(h.files, f)
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h.Cmd.Env = append(h.Cmd.Env, FortifyStatus+"=1")
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// stat is populated on fulfill
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h.Cmd.Cancel = func() error { return h.stat.Close() }
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} else {
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h.Cmd.Env = append(h.Cmd.Env, FortifyStatus+"=0")
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}
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return h.argF(statFd)
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}
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var commandContext = exec.CommandContext
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