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125 lines
3.9 KiB
125 lines
3.9 KiB
package magic
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import (
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"bytes"
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"encoding/binary"
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)
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var (
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// SevenZ matches a 7z archive.
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SevenZ = prefix([]byte{0x37, 0x7A, 0xBC, 0xAF, 0x27, 0x1C})
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// Gzip matches gzip files based on http://www.zlib.org/rfc-gzip.html#header-trailer.
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Gzip = prefix([]byte{0x1f, 0x8b})
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// Fits matches an Flexible Image Transport System file.
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Fits = prefix([]byte{
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0x53, 0x49, 0x4D, 0x50, 0x4C, 0x45, 0x20, 0x20, 0x3D, 0x20,
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0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,
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0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x54,
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})
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// Xar matches an eXtensible ARchive format file.
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Xar = prefix([]byte{0x78, 0x61, 0x72, 0x21})
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// Bz2 matches a bzip2 file.
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Bz2 = prefix([]byte{0x42, 0x5A, 0x68})
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// Ar matches an ar (Unix) archive file.
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Ar = prefix([]byte{0x21, 0x3C, 0x61, 0x72, 0x63, 0x68, 0x3E})
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// Deb matches a Debian package file.
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Deb = offset([]byte{
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0x64, 0x65, 0x62, 0x69, 0x61, 0x6E, 0x2D,
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0x62, 0x69, 0x6E, 0x61, 0x72, 0x79,
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}, 8)
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// Warc matches a Web ARChive file.
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Warc = prefix([]byte("WARC/1.0"), []byte("WARC/1.1"))
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// Cab matches a Microsoft Cabinet archive file.
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Cab = prefix([]byte("MSCF\x00\x00\x00\x00"))
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// Xz matches an xz compressed stream based on https://tukaani.org/xz/xz-file-format.txt.
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Xz = prefix([]byte{0xFD, 0x37, 0x7A, 0x58, 0x5A, 0x00})
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// Lzip matches an Lzip compressed file.
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Lzip = prefix([]byte{0x4c, 0x5a, 0x49, 0x50})
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// RPM matches an RPM or Delta RPM package file.
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RPM = prefix([]byte{0xed, 0xab, 0xee, 0xdb}, []byte("drpm"))
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// Cpio matches a cpio archive file.
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Cpio = prefix([]byte("070707"), []byte("070701"), []byte("070702"))
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// RAR matches a RAR archive file.
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RAR = prefix([]byte("Rar!\x1A\x07\x00"), []byte("Rar!\x1A\x07\x01\x00"))
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)
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// InstallShieldCab matches an InstallShield Cabinet archive file.
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func InstallShieldCab(raw []byte, _ uint32) bool {
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return len(raw) > 7 &&
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bytes.Equal(raw[0:4], []byte("ISc(")) &&
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raw[6] == 0 &&
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(raw[7] == 1 || raw[7] == 2 || raw[7] == 4)
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}
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// Zstd matches a Zstandard archive file.
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func Zstd(raw []byte, limit uint32) bool {
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return len(raw) >= 4 &&
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(0x22 <= raw[0] && raw[0] <= 0x28 || raw[0] == 0x1E) && // Different Zstandard versions.
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bytes.HasPrefix(raw[1:], []byte{0xB5, 0x2F, 0xFD})
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}
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// CRX matches a Chrome extension file: a zip archive prepended by a package header.
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func CRX(raw []byte, limit uint32) bool {
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const minHeaderLen = 16
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if len(raw) < minHeaderLen || !bytes.HasPrefix(raw, []byte("Cr24")) {
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return false
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}
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pubkeyLen := binary.LittleEndian.Uint32(raw[8:12])
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sigLen := binary.LittleEndian.Uint32(raw[12:16])
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zipOffset := minHeaderLen + pubkeyLen + sigLen
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if uint32(len(raw)) < zipOffset {
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return false
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}
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return Zip(raw[zipOffset:], limit)
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}
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// Tar matches a (t)ape (ar)chive file.
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func Tar(raw []byte, _ uint32) bool {
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// The "magic" header field for files in in UStar (POSIX IEEE P1003.1) archives
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// has the prefix "ustar". The values of the remaining bytes in this field vary
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// by archiver implementation.
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if len(raw) >= 512 && bytes.HasPrefix(raw[257:], []byte{0x75, 0x73, 0x74, 0x61, 0x72}) {
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return true
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}
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if len(raw) < 256 {
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return false
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}
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// The older v7 format has no "magic" field, and therefore must be identified
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// with heuristics based on legal ranges of values for other header fields:
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// https://www.nationalarchives.gov.uk/PRONOM/Format/proFormatSearch.aspx?status=detailReport&id=385&strPageToDisplay=signatures
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rules := []struct {
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min, max uint8
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i int
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}{
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{0x21, 0xEF, 0},
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{0x30, 0x37, 105},
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{0x20, 0x37, 106},
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{0x00, 0x00, 107},
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{0x30, 0x37, 113},
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{0x20, 0x37, 114},
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{0x00, 0x00, 115},
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{0x30, 0x37, 121},
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{0x20, 0x37, 122},
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{0x00, 0x00, 123},
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{0x30, 0x37, 134},
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{0x30, 0x37, 146},
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{0x30, 0x37, 153},
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{0x00, 0x37, 154},
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}
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for _, r := range rules {
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if raw[r.i] < r.min || raw[r.i] > r.max {
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return false
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}
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}
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for _, i := range []uint8{135, 147, 155} {
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if raw[i] != 0x00 && raw[i] != 0x20 {
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return false
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}
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}
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return true
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}
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