Ophestra Umiker
1cd0846dc9
There is no way to have machinectl pass part of its argv to the child, and formatting the string for a shell is highly error-prone and complex, so the argv slice is encoded and passed to a launcher process launched by machinectl which then calls execve(2) to start the final process. Signed-off-by: Ophestra Umiker <cat@ophivana.moe>
73 lines
1.5 KiB
Go
73 lines
1.5 KiB
Go
package main
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import (
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"bytes"
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"encoding/base64"
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"encoding/gob"
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"fmt"
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"os"
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"strings"
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"syscall"
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)
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const (
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// hidden path for main to act as a launcher
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egoLauncher = "EGO_LAUNCHER"
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)
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// hidden launcher path
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func tryLauncher() {
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if printVersion {
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if r, ok := os.LookupEnv(egoLauncher); ok {
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// egoLauncher variable contains launcher payload
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dec := base64.NewDecoder(base64.StdEncoding, strings.NewReader(r))
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var argv []string
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if err := gob.NewDecoder(dec).Decode(&argv); err != nil {
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fmt.Println("Error decoding launcher payload:", err)
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os.Exit(1)
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}
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if err := os.Unsetenv(egoLauncher); err != nil {
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fmt.Println("Error unsetting launcher payload:", err)
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// not fatal, do not fail
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}
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var p string
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if len(argv) > 0 {
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if p, ok = which(argv[0]); !ok {
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fmt.Printf("Did not find '%s' in PATH\n", argv[0])
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os.Exit(1)
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}
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} else {
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if p, ok = os.LookupEnv("SHELL"); !ok {
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fmt.Println("No command was specified and $SHELL was unset")
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os.Exit(1)
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}
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}
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if err := syscall.Exec(p, argv, os.Environ()); err != nil {
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fmt.Println("Error executing launcher payload:", err)
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os.Exit(1)
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}
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// unreachable
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os.Exit(1)
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return
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}
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}
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}
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func launcherPayloadEnv() string {
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r := &bytes.Buffer{}
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enc := base64.NewEncoder(base64.StdEncoding, r)
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if err := gob.NewEncoder(enc).Encode(command); err != nil {
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fatal("Error encoding launcher payload:", err)
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}
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_ = enc.Close()
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return egoLauncher + "=" + r.String()
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}
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