| 1 | package maintenance |
| 2 | |
| 3 | import ( |
| 4 | "context" |
| 5 | "crypto/ecdh" |
| 6 | "encoding/base64" |
| 7 | "errors" |
| 8 | "io" |
| 9 | "os" |
| 10 | "time" |
| 11 | ) |
| 12 | |
| 13 | const MaxResultBytes = 64 << 10 |
| 14 | const MaxExecutionDuration = 10 * time.Minute |
| 15 | |
| 16 | var ( |
| 17 | ErrResult = errors.New("maintenance: private result unavailable") |
| 18 | ErrResultOverflow = errors.New("maintenance: private result exceeds limit") |
| 19 | ) |
| 20 | |
| 21 | // CaptureResult takes ownership of a dedicated stdout read pipe and closes it |
| 22 | // on every return. It returns complete bytes only after EOF within the deadline. |
| 23 | // Closing this pipe does not prove the command or its descendants have stopped; |
| 24 | // the worker must separately check Wait and containment before publishing success. |
| 25 | func CaptureResult(ctx context.Context, pipe *os.File) ([]byte, error) { |
| 26 | if pipe == nil { |
| 27 | return nil, ErrResult |
| 28 | } |
| 29 | defer pipe.Close() |
| 30 | if ctx == nil { |
| 31 | return nil, ErrResult |
| 32 | } |
| 33 | deadline, ok := ctx.Deadline() |
| 34 | remaining := time.Until(deadline) |
| 35 | if !ok || remaining <= 0 || remaining > MaxExecutionDuration || ctx.Err() != nil { |
| 36 | return nil, ErrResult |
| 37 | } |
| 38 | info, err := pipe.Stat() |
| 39 | if err != nil || info.Mode()&os.ModeNamedPipe == 0 { |
| 40 | return nil, ErrResult |
| 41 | } |
| 42 | stop := context.AfterFunc(ctx, func() { _ = pipe.Close() }) |
| 43 | defer stop() |
| 44 | body, err := io.ReadAll(io.LimitReader(pipe, MaxResultBytes+1)) |
| 45 | if err != nil || ctx.Err() != nil { |
| 46 | clear(body) |
| 47 | return nil, ErrResult |
| 48 | } |
| 49 | if len(body) > MaxResultBytes { |
| 50 | clear(body) |
| 51 | return nil, ErrResultOverflow |
| 52 | } |
| 53 | if err := pipe.Close(); err != nil || ctx.Err() != nil { |
| 54 | clear(body) |
| 55 | return nil, ErrResult |
| 56 | } |
| 57 | return body, nil |
| 58 | } |
| 59 | |
| 60 | func SealResult(pub *ecdh.PublicKey, binding Binding, body []byte) (string, error) { |
| 61 | if binding.Direction != DirectionResult || len(body) > MaxResultBytes { |
| 62 | return "", ErrResult |
| 63 | } |
| 64 | sealed, err := Seal(pub, binding, body) |
| 65 | if err != nil { |
| 66 | return "", ErrResult |
| 67 | } |
| 68 | return sealed, nil |
| 69 | } |
| 70 | |
| 71 | // OpenResult decrypts bytes for the recipient. Encryption alone does not prove |
| 72 | // which worker produced them; callers must verify the authenticated operation |
| 73 | // outcome before treating these bytes as execution or completion evidence. |
| 74 | func OpenResult(priv *ecdh.PrivateKey, binding Binding, sealed string) ([]byte, error) { |
| 75 | const overhead = len(envelopePrefix) + ephemeralBytes + nonceBytes + tagBytes |
| 76 | if binding.Direction != DirectionResult || len(sealed) > base64.StdEncoding.EncodedLen(overhead+MaxResultBytes) { |
| 77 | return nil, ErrResult |
| 78 | } |
| 79 | body, err := Open(priv, binding, sealed) |
| 80 | if err != nil { |
| 81 | return nil, ErrResult |
| 82 | } |
| 83 | // The decoded bound is necessary even after the encoded-length check: |
| 84 | // base64 padding can give adjacent raw lengths the same encoded length. |
| 85 | if len(body) > MaxResultBytes { |
| 86 | clear(body) |
| 87 | return nil, ErrResult |
| 88 | } |
| 89 | return body, nil |
| 90 | } |
| 91 | |
amadan