| 1 | //go:build linux |
| 2 | |
| 3 | package dbreads |
| 4 | |
| 5 | import ( |
| 6 | "errors" |
| 7 | "fmt" |
| 8 | "log" |
| 9 | "net" |
| 10 | "os" |
| 11 | "os/user" |
| 12 | "strconv" |
| 13 | |
| 14 | "golang.org/x/sys/unix" |
| 15 | ) |
| 16 | |
| 17 | var errNotSocket = errors.New("stdin is not a connected unix stream socket") |
| 18 | |
| 19 | // RunWorker is `carlos system db-worker`, which carlos-dbread@.service runs |
| 20 | // once per connection to carlos-dbread.socket (spec §8.3). |
| 21 | func RunWorker(args []string) { |
| 22 | if len(args) != 0 { |
| 23 | fmt.Fprintln(os.Stderr, "db-worker: takes no arguments") |
| 24 | os.Exit(2) |
| 25 | } |
| 26 | RunWorkerWith(WorkerOptions{Scratch: "/var/tmp", MaxRestored: fileSizeLimit()}) |
| 27 | } |
| 28 | |
| 29 | // RunWorkerWith is RunWorker with its options supplied: the seam the root |
| 30 | // runner's acceptance tests use to make a restore slow (Task 15). |
| 31 | func RunWorkerWith(opt WorkerOptions) { |
| 32 | conn, err := StdinConn(os.Stdin, CarlosUID) |
| 33 | if err != nil { |
| 34 | fmt.Fprintf(os.Stderr, "db-worker: %v\n", err) |
| 35 | os.Exit(2) |
| 36 | } |
| 37 | if err := ServeWorker(conn, opt); err != nil { |
| 38 | log.Printf("db-worker: %v", err) |
| 39 | os.Exit(1) |
| 40 | } |
| 41 | } |
| 42 | |
| 43 | // CarlosUID is the agent's user, the only peer the worker serves. |
| 44 | func CarlosUID() (uint32, error) { |
| 45 | u, err := user.Lookup("carlos") |
| 46 | if err != nil { |
| 47 | return 0, err |
| 48 | } |
| 49 | uid, err := strconv.ParseUint(u.Uid, 10, 32) |
| 50 | return uint32(uid), err |
| 51 | } |
| 52 | |
| 53 | // StdinConn checks f is a connected unix stream socket (SO_TYPE, the socket |
| 54 | // name's family, SO_PEERCRED) whose peer is wantUID, and returns it as a |
| 55 | // connection. |
| 56 | func StdinConn(f *os.File, wantUID func() (uint32, error)) (net.Conn, error) { |
| 57 | fd := int(f.Fd()) |
| 58 | typ, err := unix.GetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_TYPE) |
| 59 | if err != nil || typ != unix.SOCK_STREAM { |
| 60 | return nil, errNotSocket |
| 61 | } |
| 62 | if sa, err := unix.Getsockname(fd); err != nil { |
| 63 | return nil, errNotSocket |
| 64 | } else if _, ok := sa.(*unix.SockaddrUnix); !ok { |
| 65 | return nil, errNotSocket |
| 66 | } |
| 67 | cred, err := unix.GetsockoptUcred(fd, unix.SOL_SOCKET, unix.SO_PEERCRED) |
| 68 | if err != nil || cred.Pid == 0 { |
| 69 | return nil, errNotSocket |
| 70 | } |
| 71 | want, err := wantUID() |
| 72 | if err != nil { |
| 73 | return nil, err |
| 74 | } |
| 75 | if cred.Uid != want { |
| 76 | return nil, fmt.Errorf("the peer is uid %d, not the agent's uid %d", cred.Uid, want) |
| 77 | } |
| 78 | c, err := net.FileConn(f) |
| 79 | if err != nil { |
| 80 | return nil, errNotSocket |
| 81 | } |
| 82 | return c, nil |
| 83 | } |
| 84 | |
| 85 | // fileSizeLimit is the unit's LimitFSIZE, the restored-size cap the box set |
| 86 | // for its workers, or DefaultMaxRestored when the process has no limit. |
| 87 | func fileSizeLimit() int64 { |
| 88 | var r unix.Rlimit |
| 89 | if err := unix.Getrlimit(unix.RLIMIT_FSIZE, &r); err != nil || r.Cur == unix.RLIM_INFINITY || r.Cur > 1<<62 { |
| 90 | return DefaultMaxRestored |
| 91 | } |
| 92 | return int64(r.Cur) |
| 93 | } |
| 94 | |
amadan