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net/http: remove discrepancies between the MIME Sniffing Spec and its implementation
The change fixes the following deviations between the existing implementation and the Spec: 1. Using pattern instead of "mask" for assertion and iteration in the Pattern Matching Algorithm. 2. Rename "image/vnd.microsoft.icon" to "image/x-icon" and add another signature for the same. 3. Using named strings instead of hexadecimal representation in "application/zip" and "application/x-rar-compressed". 4. Reordering "sniffSignatures" in accordance with the Spec section "Identifying a resource with an unknown MIME type". In addition to the above fixes, unit tests for Image MIME type group are added. Fixes #30570 Change-Id: I97d2ae22b426c3c57bf8efd2ed9396c0be983688 Reviewed-on: https://go-review.googlesource.com/c/go/+/165277 Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com> Run-TryBot: Emmanuel Odeke <emm.odeke@gmail.com> TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Kshitij Saraogi
Emmanuel Odeke
parent
43e8fd4ef1
commit
583fddf3bc
@ -37,6 +37,8 @@ func DetectContentType(data []byte) string {
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return "application/octet-stream" // fallback
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}
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// isWS reports whether the provided byte is a whitespace byte (0xWS)
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// as defined in https://mimesniff.spec.whatwg.org/#terminology.
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func isWS(b byte) bool {
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switch b {
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case '\t', '\n', '\x0c', '\r', ' ':
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@ -45,6 +47,16 @@ func isWS(b byte) bool {
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return false
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}
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// isTT reports whether the provided byte is a tag-terminating byte (0xTT)
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// as defined in https://mimesniff.spec.whatwg.org/#terminology.
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func isTT(b byte) bool {
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switch b {
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case ' ', '>':
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return true
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}
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return false
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}
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type sniffSig interface {
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// match returns the MIME type of the data, or "" if unknown.
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match(data []byte, firstNonWS int) string
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@ -69,33 +81,57 @@ var sniffSignatures = []sniffSig{
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htmlSig("<BR"),
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htmlSig("<P"),
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htmlSig("<!--"),
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&maskedSig{mask: []byte("\xFF\xFF\xFF\xFF\xFF"), pat: []byte("<?xml"), skipWS: true, ct: "text/xml; charset=utf-8"},
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&maskedSig{
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mask: []byte("\xFF\xFF\xFF\xFF\xFF"),
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pat: []byte("<?xml"),
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skipWS: true,
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ct: "text/xml; charset=utf-8"},
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&exactSig{[]byte("%PDF-"), "application/pdf"},
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&exactSig{[]byte("%!PS-Adobe-"), "application/postscript"},
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// UTF BOMs.
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&maskedSig{mask: []byte("\xFF\xFF\x00\x00"), pat: []byte("\xFE\xFF\x00\x00"), ct: "text/plain; charset=utf-16be"},
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&maskedSig{mask: []byte("\xFF\xFF\x00\x00"), pat: []byte("\xFF\xFE\x00\x00"), ct: "text/plain; charset=utf-16le"},
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&maskedSig{mask: []byte("\xFF\xFF\xFF\x00"), pat: []byte("\xEF\xBB\xBF\x00"), ct: "text/plain; charset=utf-8"},
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&maskedSig{
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mask: []byte("\xFF\xFF\x00\x00"),
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pat: []byte("\xFE\xFF\x00\x00"),
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ct: "text/plain; charset=utf-16be",
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},
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&maskedSig{
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mask: []byte("\xFF\xFF\x00\x00"),
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pat: []byte("\xFF\xFE\x00\x00"),
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ct: "text/plain; charset=utf-16le",
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},
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&maskedSig{
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mask: []byte("\xFF\xFF\xFF\x00"),
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pat: []byte("\xEF\xBB\xBF\x00"),
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ct: "text/plain; charset=utf-8",
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},
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// Image types
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// For posterity, we originally returned "image/vnd.microsoft.icon" from
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// https://tools.ietf.org/html/draft-ietf-websec-mime-sniff-03#section-7
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// https://codereview.appspot.com/4746042
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// but that has since been replaced with "image/x-icon" in Section 6.2
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// of https://mimesniff.spec.whatwg.org/#matching-an-image-type-pattern
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&exactSig{[]byte("\x00\x00\x01\x00"), "image/x-icon"},
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&exactSig{[]byte("\x00\x00\x02\x00"), "image/x-icon"},
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&exactSig{[]byte("BM"), "image/bmp"},
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&exactSig{[]byte("GIF87a"), "image/gif"},
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&exactSig{[]byte("GIF89a"), "image/gif"},
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&exactSig{[]byte("\x89\x50\x4E\x47\x0D\x0A\x1A\x0A"), "image/png"},
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&exactSig{[]byte("\xFF\xD8\xFF"), "image/jpeg"},
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&exactSig{[]byte("BM"), "image/bmp"},
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&maskedSig{
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mask: []byte("\xFF\xFF\xFF\xFF\x00\x00\x00\x00\xFF\xFF\xFF\xFF\xFF\xFF"),
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pat: []byte("RIFF\x00\x00\x00\x00WEBPVP"),
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ct: "image/webp",
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},
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&exactSig{[]byte("\x00\x00\x01\x00"), "image/vnd.microsoft.icon"},
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&exactSig{[]byte("\x89PNG\x0D\x0A\x1A\x0A"), "image/png"},
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&exactSig{[]byte("\xFF\xD8\xFF"), "image/jpeg"},
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// Audio and Video types
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// Enforce the pattern match ordering as prescribed in
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// https://mimesniff.spec.whatwg.org/#matching-an-audio-or-video-type-pattern
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&maskedSig{
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mask: []byte("\xFF\xFF\xFF\xFF\x00\x00\x00\x00\xFF\xFF\xFF\xFF"),
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pat: []byte("RIFF\x00\x00\x00\x00WAVE"),
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ct: "audio/wave",
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mask: []byte("\xFF\xFF\xFF\xFF"),
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pat: []byte(".snd"),
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ct: "audio/basic",
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},
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&maskedSig{
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mask: []byte("\xFF\xFF\xFF\xFF\x00\x00\x00\x00\xFF\xFF\xFF\xFF"),
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@ -103,9 +139,9 @@ var sniffSignatures = []sniffSig{
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ct: "audio/aiff",
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},
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&maskedSig{
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mask: []byte("\xFF\xFF\xFF\xFF"),
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pat: []byte(".snd"),
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ct: "audio/basic",
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mask: []byte("\xFF\xFF\xFF"),
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pat: []byte("ID3"),
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ct: "audio/mpeg",
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},
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&maskedSig{
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mask: []byte("\xFF\xFF\xFF\xFF\xFF"),
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@ -117,21 +153,25 @@ var sniffSignatures = []sniffSig{
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pat: []byte("MThd\x00\x00\x00\x06"),
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ct: "audio/midi",
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},
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&maskedSig{
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mask: []byte("\xFF\xFF\xFF"),
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pat: []byte("ID3"),
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ct: "audio/mpeg",
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},
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&maskedSig{
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mask: []byte("\xFF\xFF\xFF\xFF\x00\x00\x00\x00\xFF\xFF\xFF\xFF"),
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pat: []byte("RIFF\x00\x00\x00\x00AVI "),
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ct: "video/avi",
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},
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&maskedSig{
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mask: []byte("\xFF\xFF\xFF\xFF\x00\x00\x00\x00\xFF\xFF\xFF\xFF"),
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pat: []byte("RIFF\x00\x00\x00\x00WAVE"),
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ct: "audio/wave",
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},
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// 6.2.0.2. video/mp4
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mp4Sig{},
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// 6.2.0.3. video/webm
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&exactSig{[]byte("\x1A\x45\xDF\xA3"), "video/webm"},
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// Fonts
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// Font types
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&maskedSig{
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// 34 NULL bytes followed by the string "LP"
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pat: []byte("\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x4C\x50"),
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pat: []byte("\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00LP"),
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// 34 NULL bytes followed by \xF\xF
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mask: []byte("\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xFF\xFF"),
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ct: "application/vnd.ms-fontobject",
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@ -142,15 +182,13 @@ var sniffSignatures = []sniffSig{
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&exactSig{[]byte("wOFF"), "font/woff"},
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&exactSig{[]byte("wOF2"), "font/woff2"},
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&exactSig{[]byte("\x1A\x45\xDF\xA3"), "video/webm"},
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&exactSig{[]byte("\x52\x61\x72\x20\x1A\x07\x00"), "application/x-rar-compressed"},
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&exactSig{[]byte("\x50\x4B\x03\x04"), "application/zip"},
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// Archive types
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&exactSig{[]byte("\x1F\x8B\x08"), "application/x-gzip"},
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&exactSig{[]byte("PK\x03\x04"), "application/zip"},
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&exactSig{[]byte("Rar \x1A\x07\x00"), "application/x-rar-compressed"},
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&exactSig{[]byte("\x00\x61\x73\x6D"), "application/wasm"},
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mp4Sig{},
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textSig{}, // should be last
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}
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@ -182,12 +220,12 @@ func (m *maskedSig) match(data []byte, firstNonWS int) string {
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if len(m.pat) != len(m.mask) {
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return ""
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}
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if len(data) < len(m.mask) {
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if len(data) < len(m.pat) {
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return ""
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}
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for i, mask := range m.mask {
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db := data[i] & mask
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if db != m.pat[i] {
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for i, pb := range m.pat {
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maskedData := data[i] & m.mask[i]
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if maskedData != pb {
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return ""
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}
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}
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@ -210,8 +248,8 @@ func (h htmlSig) match(data []byte, firstNonWS int) string {
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return ""
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}
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}
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// Next byte must be space or right angle bracket.
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if db := data[len(h)]; db != ' ' && db != '>' {
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// Next byte must be a tag-terminating byte(0xTT).
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if !isTT(data[len(h)]) {
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return ""
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}
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return "text/html; charset=utf-8"
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@ -229,7 +267,7 @@ func (mp4Sig) match(data []byte, firstNonWS int) string {
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return ""
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}
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boxSize := int(binary.BigEndian.Uint32(data[:4]))
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if boxSize%4 != 0 || len(data) < boxSize {
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if len(data) < boxSize || boxSize%4 != 0 {
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return ""
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}
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if !bytes.Equal(data[4:8], mp4ftype) {
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@ -237,7 +275,7 @@ func (mp4Sig) match(data []byte, firstNonWS int) string {
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}
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for st := 8; st < boxSize; st += 4 {
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if st == 12 {
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// minor version number
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// Ignores the four bytes that correspond to the version number of the "major brand".
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continue
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}
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if bytes.Equal(data[st:st+3], mp4) {
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@ -36,8 +36,14 @@ var sniffTests = []struct {
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{"XML", []byte("\n<?xml!"), "text/xml; charset=utf-8"},
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// Image types.
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{"Windows icon", []byte("\x00\x00\x01\x00"), "image/x-icon"},
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{"Windows cursor", []byte("\x00\x00\x02\x00"), "image/x-icon"},
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{"BMP image", []byte("BM..."), "image/bmp"},
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{"GIF 87a", []byte(`GIF87a`), "image/gif"},
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{"GIF 89a", []byte(`GIF89a...`), "image/gif"},
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{"WEBP image", []byte("RIFF\x00\x00\x00\x00WEBPVP"), "image/webp"},
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{"PNG image", []byte("\x89PNG\x0D\x0A\x1A\x0A"), "image/png"},
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{"JPEG image", []byte("\xFF\xD8\xFF"), "image/jpeg"},
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// Audio types.
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{"MIDI audio", []byte("MThd\x00\x00\x00\x06\x00\x01"), "audio/midi"},
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