| 1 | package geoip |
| 2 | |
| 3 | import ( |
| 4 | "archive/tar" |
| 5 | "compress/gzip" |
| 6 | "errors" |
| 7 | "fmt" |
| 8 | "io" |
| 9 | "path" |
| 10 | "strings" |
| 11 | ) |
| 12 | |
| 13 | // ErrTooLarge is a capped reader refusing to read past its cap (spec §10.3). |
| 14 | var ErrTooLarge = errors.New("geoip archive: larger than its cap") |
| 15 | |
| 16 | type cappedReader struct { |
| 17 | r io.Reader |
| 18 | left int64 |
| 19 | } |
| 20 | |
| 21 | func (c *cappedReader) Read(p []byte) (int, error) { |
| 22 | if c.left < 0 { |
| 23 | return 0, ErrTooLarge |
| 24 | } |
| 25 | if int64(len(p)) > c.left+1 { |
| 26 | p = p[:c.left+1] |
| 27 | } |
| 28 | n, err := c.r.Read(p) |
| 29 | c.left -= int64(n) |
| 30 | if c.left < 0 { |
| 31 | return n, ErrTooLarge |
| 32 | } |
| 33 | return n, err |
| 34 | } |
| 35 | |
| 36 | // CappedReader reads r until more than max bytes have come through, then |
| 37 | // fails with ErrTooLarge. Exactly max bytes read cleanly. |
| 38 | func CappedReader(r io.Reader, max int64) io.Reader { return &cappedReader{r: r, left: max} } |
| 39 | |
| 40 | // GunzipReader expands a gzip stream, refusing to expand past maxExpanded: |
| 41 | // a decompression bomb stops at the cap, never at the end of its expansion. |
| 42 | func GunzipReader(r io.Reader, maxExpanded int64) (io.Reader, error) { |
| 43 | zr, err := gzip.NewReader(r) |
| 44 | if err != nil { |
| 45 | return nil, fmt.Errorf("geoip archive: not gzip: %w", err) |
| 46 | } |
| 47 | return CappedReader(zr, maxExpanded), nil |
| 48 | } |
| 49 | |
| 50 | // TarGzMMDB returns the first regular *.mmdb member of a .tar.gz (MaxMind's |
| 51 | // download format). Every expanded byte counts toward maxExpanded, |
| 52 | // including the members walked past, so junk padding cannot fill a disk. |
| 53 | func TarGzMMDB(r io.Reader, maxExpanded int64) (io.Reader, error) { |
| 54 | expanded, err := GunzipReader(r, maxExpanded) |
| 55 | if err != nil { |
| 56 | return nil, err |
| 57 | } |
| 58 | tr := tar.NewReader(expanded) |
| 59 | for { |
| 60 | h, err := tr.Next() |
| 61 | if err == io.EOF { |
| 62 | return nil, errors.New("geoip archive: no .mmdb member") |
| 63 | } |
| 64 | if err != nil { |
| 65 | return nil, err |
| 66 | } |
| 67 | if h.Typeflag == tar.TypeReg && strings.HasSuffix(path.Base(h.Name), ".mmdb") { |
| 68 | return tr, nil |
| 69 | } |
| 70 | } |
| 71 | } |
| 72 | |
amadan