| 1 | //go:build linux |
| 2 | |
| 3 | package host |
| 4 | |
| 5 | import ( |
| 6 | "context" |
| 7 | "net" |
| 8 | "net/url" |
| 9 | "os" |
| 10 | "os/exec" |
| 11 | "path/filepath" |
| 12 | "strconv" |
| 13 | "strings" |
| 14 | |
| 15 | "github.com/carlosframework/platform/internal/hostbox" |
| 16 | "github.com/carlosframework/platform/internal/hostwrite" |
| 17 | "github.com/carlosframework/platform/internal/registry" |
| 18 | "golang.org/x/sys/unix" |
| 19 | ) |
| 20 | |
| 21 | // claimProbeDepth bounds the parent walk from a peer to the spawned process. |
| 22 | const claimProbeDepth = 64 |
| 23 | |
| 24 | // claimProbeSocketReady is the claim's probe readiness check (claim Plan 9 |
| 25 | // D3; moves §7.7 as ruled in H12): GET the declared readiness path over the |
| 26 | // route's socket and accept 2xx only, and only from a peer whose pid is the |
| 27 | // spawned process or a descendant of it and is a member of exactly the main |
| 28 | // role's cgroup. A preforking server's worker passes; any process outside the |
| 29 | // spawned tree or the role's group never receives the request. |
| 30 | func claimProbeSocketReady(ctx context.Context, cmd *exec.Cmd, rt registry.Route, in ClaimLaunchInputs, roleCgroup string) error { |
| 31 | target, ok := claimReadyURL(in.ReadyPath) |
| 32 | if cmd == nil || cmd.Process == nil || cmd.Process.Pid <= 1 || rt.Socket == "" || !ok || !filepath.IsAbs(roleCgroup) { |
| 33 | return hostwrite.ErrUnavailable |
| 34 | } |
| 35 | rel, err := filepath.Rel("/sys/fs/cgroup", filepath.Clean(roleCgroup)) |
| 36 | if err != nil || !filepath.IsLocal(rel) || rel == "." { |
| 37 | return hostwrite.ErrUnavailable |
| 38 | } |
| 39 | root, member := cmd.Process.Pid, "0::/"+filepath.ToSlash(rel) |
| 40 | return claimPollReady(ctx, rt.Socket, target, func(conn net.Conn) error { return claimProbePeer(conn, root, member) }, func(status int) bool { return status >= 200 && status < 300 }) |
| 41 | } |
| 42 | |
| 43 | // claimReadyURL is the request target for a declared absolute path on the |
| 44 | // socket's fixed host. A path that could name another host is refused. |
| 45 | func claimReadyURL(path string) (string, bool) { |
| 46 | if !strings.HasPrefix(path, "/") || strings.HasPrefix(path, "//") || strings.ContainsAny(path, "#\\ \t\r\n\x00") { |
| 47 | return "", false |
| 48 | } |
| 49 | u, err := url.Parse("http://carlos" + path) |
| 50 | if err != nil || u.Host != "carlos" || u.User != nil || u.Opaque != "" { |
| 51 | return "", false |
| 52 | } |
| 53 | return u.String(), true |
| 54 | } |
| 55 | |
| 56 | // claimProbePeer accepts the connection's peer only when its parent chain |
| 57 | // reaches root and its cgroup v2 membership is exactly member. |
| 58 | func claimProbePeer(conn net.Conn, root int, member string) error { |
| 59 | unixConn, ok := conn.(*net.UnixConn) |
| 60 | if !ok || root <= 1 { |
| 61 | return hostwrite.ErrUnavailable |
| 62 | } |
| 63 | raw, err := unixConn.SyscallConn() |
| 64 | if err != nil { |
| 65 | return err |
| 66 | } |
| 67 | var peer *unix.Ucred |
| 68 | var socketErr error |
| 69 | if err = raw.Control(func(fd uintptr) { peer, socketErr = unix.GetsockoptUcred(int(fd), unix.SOL_SOCKET, unix.SO_PEERCRED) }); err != nil { |
| 70 | return err |
| 71 | } |
| 72 | if socketErr != nil { |
| 73 | return socketErr |
| 74 | } |
| 75 | if peer == nil || peer.Pid <= 1 { |
| 76 | return hostwrite.ErrUnavailable |
| 77 | } |
| 78 | pid := int(peer.Pid) |
| 79 | for at, steps := pid, 0; at != root; steps++ { |
| 80 | if at <= 1 || steps >= claimProbeDepth { |
| 81 | return hostbox.ErrChanged |
| 82 | } |
| 83 | if at, err = claimParentPID(at); err != nil { |
| 84 | return err |
| 85 | } |
| 86 | } |
| 87 | groups, err := os.ReadFile("/proc/" + strconv.Itoa(pid) + "/cgroup") |
| 88 | if err != nil { |
| 89 | return err |
| 90 | } |
| 91 | for _, line := range strings.Split(string(groups), "\n") { |
| 92 | if line == member { |
| 93 | return nil |
| 94 | } |
| 95 | } |
| 96 | return hostbox.ErrChanged |
| 97 | } |
| 98 | |
| 99 | func claimParentPID(pid int) (int, error) { |
| 100 | raw, err := os.ReadFile("/proc/" + strconv.Itoa(pid) + "/stat") |
| 101 | if err != nil { |
| 102 | return 0, err |
| 103 | } |
| 104 | i := strings.LastIndexByte(string(raw), ')') |
| 105 | if i < 0 { |
| 106 | return 0, hostwrite.ErrUnavailable |
| 107 | } |
| 108 | fields := strings.Fields(string(raw)[i+1:]) |
| 109 | if len(fields) < 2 { |
| 110 | return 0, hostwrite.ErrUnavailable |
| 111 | } |
| 112 | return strconv.Atoi(fields[1]) |
| 113 | } |
| 114 | |
amadan