package main /* The purpose of this command is to be run as a new user. It initializes their ssh authorized_keys2 file, which allows them to ssh in for the first time. This is an isolated command because creating a file and chowning it normally requires root permissions. We don't want to run the welcome command as root, so we give it `sudo` permission to run this one command as any user. The keyfile path is hardcoded, so if someone were to assume `welcome`'s identity, it could of course cause havoc but not delete This is a port of the old createkeyfile.py script from the former admin system. There are two functional changes: 1. It also creates `.ssh`. I can't remember if there was a reason the old script didn't do that as there is no record one way or the other. But having this command make `.ssh` means one fewer thing in the sudoers file. 2. It guards against overwriting of both .ssh and authorized_keys2. This is solely to limit the effect of a security breach. In the old admin system keys were managed via the django admin, meaning this script was used to add keys to authorized_keys2. these days we just edit authorized_keys2 directly, so this new command should only ever be used to initialize .ssh for a new user. */ import ( "fmt" "os" "os/user" "path" "strings" ) const keyfileName = "authorized_keys2" func quit(msg string) { fmt.Println(msg) os.Exit(1) } func main() { username := os.Args[1] if username == "" { quit("expected username as argument") } u, err := user.Current() if err != nil { quit(err.Error()) } if u.Username != username { quit("that's my purse; I don't know you") } sshPath := path.Join("/home", u.Username, ".ssh") keyfilePath := path.Join(sshPath, keyfileName) if err = os.Mkdir(sshPath, os.FileMode(0700)); err != nil { quit(err.Error()) } f, err := os.OpenFile(keyfilePath, os.O_CREATE|os.O_EXCL|os.O_RDWR, 0600) if err != nil { quit(fmt.Sprintf("failed to open %s: %s", keyfilePath, err.Error())) } defer f.Close() stdin := make([]byte, 90000) // arbitrary limit n, err := os.Stdin.Read(stdin) if err != nil { quit(err.Error()) } else if n == 0 { quit("nothing passed on STDIN") } stdin = stdin[0:n] if !strings.HasPrefix(string(stdin), "########## GREETINGS! ##########") { // TODO further validation? quit(fmt.Sprintf("file contents look wrong: %s", string(stdin))) } n, err = f.Write(stdin) if err != nil { quit(err.Error()) } else if n == 0 { quit("wrote nothing to keyfile") } } /* The old script, in full: #!/usr/bin/env python3 """this script allows django to add public keys for a user. it's in its own script so that a specific command can be added to the ttadmin user's sudoers file.""" import sys KEYFILE_PATH = '/home/{}/.ssh/authorized_keys2' def main(argv): username = argv[1] with open(KEYFILE_PATH.format(username), 'w') as f: f.write(sys.stdin.read()) if __name__ == '__main__': exit(main(sys.argv)) */