| 1 | package archive |
| 2 | |
| 3 | import ( |
| 4 | "archive/tar" |
| 5 | "crypto/ecdh" |
| 6 | "crypto/sha256" |
| 7 | "errors" |
| 8 | "fmt" |
| 9 | "io" |
| 10 | |
| 11 | "github.com/carlosframework/platform/internal/appconfig" |
| 12 | ) |
| 13 | |
| 14 | // errVerifyAborted is what Verify closes its pipe with when it stops |
| 15 | // reading before the end, so Open's next write fails and its goroutine |
| 16 | // exits instead of blocking on the pipe for the rest of the archive. |
| 17 | var errVerifyAborted = errors.New("archive: verify stopped reading") |
| 18 | |
| 19 | // check validates a manifest on its own, before any byte of the archive is |
| 20 | // read: the version and chunk size this package writes, the digests and |
| 21 | // key present, and an entry list Build could have written (valid, unique |
| 22 | // paths within the limits, sizes summing to Bytes, at most Cap). |
| 23 | func (m Manifest) check() error { |
| 24 | switch { |
| 25 | case m.V != ManifestVersion: |
| 26 | return fmt.Errorf("archive: manifest version %d, want %d", m.V, ManifestVersion) |
| 27 | case m.Chunk != ChunkSize: |
| 28 | return fmt.Errorf("archive: manifest chunk %d, want %d", m.Chunk, ChunkSize) |
| 29 | case m.Plain == "" || m.Sealed == "" || m.SealedDataKey == "": |
| 30 | return errors.New("archive: manifest carries no sealed digest, plaintext digest or sealed data key") |
| 31 | case len(m.Entries) > entryLimit: |
| 32 | return ErrTooManyEntries |
| 33 | } |
| 34 | seen := make(map[string]bool, len(m.Entries)) |
| 35 | var sum int64 |
| 36 | for _, e := range m.Entries { |
| 37 | if _, _, err := checkName(e.Path, false); err != nil { |
| 38 | return err |
| 39 | } |
| 40 | if seen[e.Path] { |
| 41 | return fmt.Errorf("%w: %q named twice in the manifest", ErrBadPath, e.Path) |
| 42 | } |
| 43 | seen[e.Path] = true |
| 44 | if e.Size < 0 || e.Size > Cap-sum { |
| 45 | return ErrOverCap |
| 46 | } |
| 47 | sum += e.Size |
| 48 | } |
| 49 | if sum != m.Bytes { |
| 50 | return fmt.Errorf("archive: manifest entries hold %d bytes, manifest says %d", sum, m.Bytes) |
| 51 | } |
| 52 | return nil |
| 53 | } |
| 54 | |
| 55 | // Verify is T5 (§7.3): it opens the sealed object with priv, streams the |
| 56 | // tar out of zstd and checks everything the manifest promised: the |
| 57 | // plaintext digest, every entry's path, size and sha256, the entry types |
| 58 | // (regular files and directories only), the limits, and the sealed digest |
| 59 | // of the bytes it read. It writes nothing and returns the first mismatch. |
| 60 | // Open's own verdict (every chunk authenticated, the final chunk present |
| 61 | // and last) wins over any mismatch found in what it produced. |
| 62 | func Verify(sealed io.Reader, m Manifest, priv *ecdh.PrivateKey, b appconfig.Binding) error { |
| 63 | if err := m.check(); err != nil { |
| 64 | return err |
| 65 | } |
| 66 | sealedHash := sha256.New() |
| 67 | pr, pw := io.Pipe() |
| 68 | done := make(chan error, 1) |
| 69 | go func() { |
| 70 | err := Open(io.TeeReader(sealed, sealedHash), m.SealedDataKey, priv, b, pw) |
| 71 | pw.CloseWithError(err) |
| 72 | done <- err |
| 73 | }() |
| 74 | plain, err := verifyStream(pr, m) |
| 75 | // Break the pipe whatever happened, so a producer still writing fails |
| 76 | // and exits, then wait for it. After a clean read to EOF this is a |
| 77 | // no-op: Open has already returned. |
| 78 | pr.CloseWithError(errVerifyAborted) |
| 79 | if openErr := <-done; openErr != nil && !errors.Is(openErr, errVerifyAborted) { |
| 80 | return openErr |
| 81 | } |
| 82 | if err != nil { |
| 83 | return err |
| 84 | } |
| 85 | if plain != m.Plain { |
| 86 | return fmt.Errorf("archive: plaintext digest %s, manifest says %s", plain, m.Plain) |
| 87 | } |
| 88 | if got := digestString(sealedHash); got != m.Sealed { |
| 89 | return fmt.Errorf("archive: sealed digest %s, manifest says %s", got, m.Sealed) |
| 90 | } |
| 91 | return nil |
| 92 | } |
| 93 | |
| 94 | // verifyStream reads the opened archive from r to its end and checks it |
| 95 | // against m, returning the plaintext digest. h hashes the decoded tar, |
| 96 | // end marker included, which is exactly what Build's hashWriter hashed (it |
| 97 | // sits between tar.Writer and the compressor), so Plain is the same bytes |
| 98 | // on both sides (round-4 finding 8). |
| 99 | func verifyStream(r io.Reader, m Manifest) (string, error) { |
| 100 | zr, err := newDecoder(r) |
| 101 | if err != nil { |
| 102 | return "", err |
| 103 | } |
| 104 | defer zr.Close() |
| 105 | h := sha256.New() |
| 106 | dec := &boundedReader{r: zr, left: decodedLimit} |
| 107 | tr := tar.NewReader(io.TeeReader(dec, h)) |
| 108 | want := make(map[string]Entry, len(m.Entries)) |
| 109 | for _, e := range m.Entries { |
| 110 | want[e.Path] = e |
| 111 | } |
| 112 | rules := newStreamRules() |
| 113 | for { |
| 114 | hdr, err := tr.Next() |
| 115 | if err == io.EOF { |
| 116 | break |
| 117 | } |
| 118 | if err != nil { |
| 119 | return "", err |
| 120 | } |
| 121 | name, _, _, err := rules.admit(hdr) |
| 122 | if err != nil { |
| 123 | return "", err |
| 124 | } |
| 125 | if hdr.Typeflag == tar.TypeDir { |
| 126 | continue |
| 127 | } |
| 128 | e, ok := want[name] |
| 129 | if !ok { |
| 130 | return "", fmt.Errorf("archive: entry %q is not in the manifest", hdr.Name) |
| 131 | } |
| 132 | if e.Size != hdr.Size { |
| 133 | return "", fmt.Errorf("archive: entry %q size differs from the manifest", hdr.Name) |
| 134 | } |
| 135 | fh := sha256.New() |
| 136 | if _, err := io.CopyN(fh, tr, hdr.Size); err != nil { |
| 137 | return "", err |
| 138 | } |
| 139 | if digestString(fh) != e.SHA256 { |
| 140 | return "", fmt.Errorf("archive: entry %q digest differs", hdr.Name) |
| 141 | } |
| 142 | delete(want, name) |
| 143 | } |
| 144 | // tar.Reader stops at the end-of-archive marker; whatever follows in |
| 145 | // the decoded stream must still reach h, and the raw stream must then |
| 146 | // end, so Open's terminal result becomes this read's error. A Verify |
| 147 | // that returned at the tar marker would trust an archive whose tail |
| 148 | // was never authenticated. |
| 149 | if _, err := io.Copy(h, dec); err != nil { |
| 150 | return "", err |
| 151 | } |
| 152 | if err := requireEOF(r); err != nil { |
| 153 | return "", err |
| 154 | } |
| 155 | if len(want) != 0 { |
| 156 | return "", fmt.Errorf("archive: %d manifest entries missing from the archive", len(want)) |
| 157 | } |
| 158 | if rules.content != m.Bytes { |
| 159 | return "", fmt.Errorf("archive: the archive holds %d bytes, manifest says %d", rules.content, m.Bytes) |
| 160 | } |
| 161 | return digestString(h), nil |
| 162 | } |
| 163 | |
amadan