| 1 | //go:build linux |
| 2 | |
| 3 | package host |
| 4 | |
| 5 | import ( |
| 6 | "errors" |
| 7 | "fmt" |
| 8 | "io" |
| 9 | "os" |
| 10 | |
| 11 | "github.com/carlosframework/platform/internal/moves" |
| 12 | "github.com/carlosframework/platform/internal/safefile" |
| 13 | ) |
| 14 | |
| 15 | // heldRenderJournalMax bounds the render journal root reads: a move's |
| 16 | // journal holds step values (digests, ids, one install manifest), well |
| 17 | // under this. |
| 18 | const heldRenderJournalMax = 1 << 20 |
| 19 | |
| 20 | // readHeldRenderHash is root's read of the held render's journalled hash |
| 21 | // for (host, op): moves.JournalFile under the agent's data directory. The |
| 22 | // journal is agent-written, so root never opens it by name (#267, |
| 23 | // platform-1e): safefile.OpenFile walks every directory from / with |
| 24 | // O_NOFOLLOW, pins the leaf with O_PATH|O_NOFOLLOW and fstats it before |
| 25 | // opening it for reading (with O_NONBLOCK), so a symlink at any component |
| 26 | // fails, and a FIFO, a device or a file with more than one link is refused |
| 27 | // without being opened for reading; the bytes are read from that one |
| 28 | // descriptor, bounded. A journal, or a directory on its path, that does not |
| 29 | // exist is os.ErrNotExist (not yet); anything else unsafe is |
| 30 | // errHeldReleaseUnsafe. A journal with no rendered step is "". |
| 31 | func readHeldRenderHash(dataDir, host, op string) (string, error) { |
| 32 | f, err := safefile.OpenFile(moves.JournalFile(dataDir, host, op), os.O_RDONLY, 0) |
| 33 | if errors.Is(err, os.ErrNotExist) { |
| 34 | return "", os.ErrNotExist |
| 35 | } |
| 36 | if err != nil { |
| 37 | return "", fmt.Errorf("%w: %v", errHeldReleaseUnsafe, err) |
| 38 | } |
| 39 | defer f.Close() |
| 40 | st, err := f.Stat() |
| 41 | if err != nil { |
| 42 | return "", fmt.Errorf("%w: %v", errHeldReleaseUnsafe, err) |
| 43 | } |
| 44 | if !st.Mode().IsRegular() || st.Size() > heldRenderJournalMax { |
| 45 | return "", errHeldReleaseUnsafe |
| 46 | } |
| 47 | raw, err := io.ReadAll(io.LimitReader(f, heldRenderJournalMax+1)) |
| 48 | if err != nil { |
| 49 | return "", fmt.Errorf("%w: %v", errHeldReleaseUnsafe, err) |
| 50 | } |
| 51 | if len(raw) > heldRenderJournalMax { |
| 52 | return "", errHeldReleaseUnsafe |
| 53 | } |
| 54 | j, err := moves.DecodeJournal(raw, host, op) |
| 55 | if err != nil { |
| 56 | return "", fmt.Errorf("%w: %v", errHeldReleaseUnsafe, err) |
| 57 | } |
| 58 | return j.Steps[landStepRendered], nil |
| 59 | } |
| 60 | |
amadan