| 1 | package host |
| 2 | |
| 3 | import ( |
| 4 | "context" |
| 5 | "encoding/json" |
| 6 | "errors" |
| 7 | "net" |
| 8 | "os" |
| 9 | "os/exec" |
| 10 | "path/filepath" |
| 11 | "strconv" |
| 12 | "strings" |
| 13 | "time" |
| 14 | |
| 15 | "github.com/carlosframework/platform/internal/rootstate" |
| 16 | "github.com/carlosframework/platform/internal/safefile" |
| 17 | "golang.org/x/sys/unix" |
| 18 | ) |
| 19 | |
| 20 | func captureClaimUnitSocket(path, boot string) (claimUnitSocketIdentity, error) { |
| 21 | parent, err := safefile.OpenDir(filepath.Dir(path)) |
| 22 | if err != nil { |
| 23 | return claimUnitSocketIdentity{}, err |
| 24 | } |
| 25 | defer parent.Close() |
| 26 | return claimUnitSocketAt(int(parent.Fd()), filepath.Base(path), boot) |
| 27 | } |
| 28 | |
| 29 | func claimUnitSocketAt(parent int, name, boot string) (claimUnitSocketIdentity, error) { |
| 30 | var st unix.Stat_t |
| 31 | if err := unix.Fstatat(parent, name, &st, unix.AT_SYMLINK_NOFOLLOW); err != nil { |
| 32 | return claimUnitSocketIdentity{}, err |
| 33 | } |
| 34 | if boot == "" || st.Mode&unix.S_IFMT != unix.S_IFSOCK || st.Nlink != 1 { |
| 35 | return claimUnitSocketIdentity{}, os.ErrPermission |
| 36 | } |
| 37 | return claimUnitSocketIdentity{Boot: boot, Device: uint64(st.Dev), Inode: st.Ino, UID: st.Uid, GID: st.Gid, Mode: st.Mode}, nil |
| 38 | } |
| 39 | |
| 40 | func parkClaimUnitSocket(source, archive, boot string, want claimUnitSocketIdentity) error { |
| 41 | return parkClaimUnitSocketWith(source, archive, boot, want, unix.Renameat2) |
| 42 | } |
| 43 | |
| 44 | func parkClaimUnitSocketWith(source, archive, boot string, want claimUnitSocketIdentity, rename func(int, string, int, string, uint) error) error { |
| 45 | if want.Boot == "" || want.Device == 0 || want.Inode == 0 || want.Mode&unix.S_IFMT != unix.S_IFSOCK || boot == "" { |
| 46 | return os.ErrPermission |
| 47 | } |
| 48 | src, err := safefile.OpenDir(filepath.Dir(source)) |
| 49 | if err != nil { |
| 50 | return err |
| 51 | } |
| 52 | defer src.Close() |
| 53 | dst, err := safefile.OpenDir(filepath.Dir(archive)) |
| 54 | if err != nil { |
| 55 | return err |
| 56 | } |
| 57 | defer dst.Close() |
| 58 | sfd, dfd := int(src.Fd()), int(dst.Fd()) |
| 59 | sname, dname := filepath.Base(source), filepath.Base(archive) |
| 60 | old, sourceErr := claimUnitSocketAt(sfd, sname, boot) |
| 61 | parked, archiveErr := claimUnitSocketAt(dfd, dname, boot) |
| 62 | if errors.Is(sourceErr, os.ErrNotExist) { |
| 63 | if errors.Is(archiveErr, os.ErrNotExist) { |
| 64 | return errors.Join(src.Sync(), dst.Sync()) |
| 65 | } |
| 66 | if archiveErr != nil || parked != want { |
| 67 | return os.ErrPermission |
| 68 | } |
| 69 | return errors.Join(src.Sync(), dst.Sync()) |
| 70 | } |
| 71 | if sourceErr != nil || old != want || !errors.Is(archiveErr, os.ErrNotExist) { |
| 72 | return os.ErrPermission |
| 73 | } |
| 74 | if err = rename(sfd, sname, dfd, dname, unix.RENAME_NOREPLACE); err != nil { |
| 75 | return err |
| 76 | } |
| 77 | parked, err = claimUnitSocketAt(dfd, dname, boot) |
| 78 | if err != nil || parked != want { |
| 79 | // Preserve a raced replacement; never overwrite a new source name. |
| 80 | restore := unix.Renameat2(dfd, dname, sfd, sname, unix.RENAME_NOREPLACE) |
| 81 | return errors.Join(os.ErrPermission, err, restore, src.Sync(), dst.Sync()) |
| 82 | } |
| 83 | return errors.Join(src.Sync(), dst.Sync()) |
| 84 | } |
| 85 | |
| 86 | func captureProductionClaimUnitSocket(ctx context.Context, s claimUnitShape, p claimUnitPredecessor) (claimUnitSocketIdentity, error) { |
| 87 | if !claimFlatSocket(s) { |
| 88 | return claimUnitSocketIdentity{}, os.ErrPermission |
| 89 | } |
| 90 | boot, err := claimUnitBoot() |
| 91 | if err != nil { |
| 92 | return claimUnitSocketIdentity{}, err |
| 93 | } |
| 94 | before, err := captureClaimUnitSocket(s.Socket, boot) |
| 95 | if err != nil { |
| 96 | return before, err |
| 97 | } |
| 98 | out, err := exec.CommandContext(ctx, "systemctl", "show", "-p", "MainPID", "--value", p.Unit).Output() |
| 99 | if err != nil { |
| 100 | return before, err |
| 101 | } |
| 102 | pid, err := strconv.Atoi(strings.TrimSpace(string(out))) |
| 103 | if err != nil || pid <= 1 { |
| 104 | return before, os.ErrPermission |
| 105 | } |
| 106 | conn, err := (&net.Dialer{Timeout: time.Second}).DialContext(ctx, "unix", s.Socket) |
| 107 | if err != nil { |
| 108 | return before, err |
| 109 | } |
| 110 | defer conn.Close() |
| 111 | if err = claimProbePeer(conn, pid, "0::/"+p.Group); err != nil { |
| 112 | return before, err |
| 113 | } |
| 114 | after, err := captureClaimUnitSocket(s.Socket, boot) |
| 115 | if err != nil || after != before { |
| 116 | return before, os.ErrPermission |
| 117 | } |
| 118 | return before, nil |
| 119 | } |
| 120 | |
| 121 | func parkProductionClaimUnitSocket(b claimUnitBinding, id claimUnitSocketIdentity) error { |
| 122 | if !b.valid() || !claimFlatSocket(b.Shape) { |
| 123 | return os.ErrPermission |
| 124 | } |
| 125 | boot, err := claimUnitBoot() |
| 126 | if err != nil { |
| 127 | return err |
| 128 | } |
| 129 | const dir = "/run/carlos-control/unit-migrations" |
| 130 | store, err := rootstate.Open(dir, true, false) |
| 131 | if err != nil { |
| 132 | return err |
| 133 | } |
| 134 | defer store.Close() |
| 135 | raw, err := json.Marshal(b) |
| 136 | if err != nil { |
| 137 | return err |
| 138 | } |
| 139 | return parkClaimUnitSocket(b.Shape.Socket, filepath.Join(dir, claimUnitDigest(raw)+".sock"), boot, id) |
| 140 | } |
| 141 | |
amadan