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android-review.linaro.org / platform / prebuilts / go / darwin-x86 / ebae30230ea323ebd5d80796b00cc5234e0a02f1 / . / src / net / http / sniff.go
blob: 0d21b44a560717266ea70983ce2976c0b0fc6a44 [file] [log] [blame]
Dan Willemsen38f2dba2016-07-08 14:54:35 -0700[diff] [blame]1// Copyright 2011 The Go Authors. All rights reserved.
Brent Austinba3052e2015-04-21 16:08:23 -0700[diff] [blame]2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5package http
6
7import (
8 "bytes"
9 "encoding/binary"
10)
11
12// The algorithm uses at most sniffLen bytes to make its decision.
13const sniffLen = 512
14
15// DetectContentType implements the algorithm described
16// at http://mimesniff.spec.whatwg.org/ to determine the
Dan Willemsen38f2dba2016-07-08 14:54:35 -0700[diff] [blame]17// Content-Type of the given data. It considers at most the
18// first 512 bytes of data. DetectContentType always returns
Brent Austinba3052e2015-04-21 16:08:23 -0700[diff] [blame]19// a valid MIME type: if it cannot determine a more specific one, it
20// returns "application/octet-stream".
21func DetectContentType(data []byte) string {
22 if len(data) > sniffLen {
23 data = data[:sniffLen]
24 }
25
26 // Index of the first non-whitespace byte in data.
27 firstNonWS := 0
28 for ; firstNonWS < len(data) && isWS(data[firstNonWS]); firstNonWS++ {
29 }
30
31 for _, sig := range sniffSignatures {
32 if ct := sig.match(data, firstNonWS); ct != "" {
33 return ct
34 }
35 }
36
37 return "application/octet-stream" // fallback
38}
39
40func isWS(b byte) bool {
Dan Willemsen09eb3b12015-09-16 14:34:17 -0700[diff] [blame]41 switch b {
42 case '\t', '\n', '\x0c', '\r', ' ':
43 return true
44 }
45 return false
Brent Austinba3052e2015-04-21 16:08:23 -0700[diff] [blame]46}
47
48type sniffSig interface {
49 // match returns the MIME type of the data, or "" if unknown.
50 match(data []byte, firstNonWS int) string
51}
52
53// Data matching the table in section 6.
54var sniffSignatures = []sniffSig{
55 htmlSig("<!DOCTYPE HTML"),
56 htmlSig("<HTML"),
57 htmlSig("<HEAD"),
58 htmlSig("<SCRIPT"),
59 htmlSig("<IFRAME"),
60 htmlSig("<H1"),
61 htmlSig("<DIV"),
62 htmlSig("<FONT"),
63 htmlSig("<TABLE"),
64 htmlSig("<A"),
65 htmlSig("<STYLE"),
66 htmlSig("<TITLE"),
67 htmlSig("<B"),
68 htmlSig("<BODY"),
69 htmlSig("<BR"),
70 htmlSig("<P"),
71 htmlSig("<!--"),
72
73 &maskedSig{mask: []byte("\xFF\xFF\xFF\xFF\xFF"), pat: []byte("<?xml"), skipWS: true, ct: "text/xml; charset=utf-8"},
74
75 &exactSig{[]byte("%PDF-"), "application/pdf"},
76 &exactSig{[]byte("%!PS-Adobe-"), "application/postscript"},
77
78 // UTF BOMs.
79 &maskedSig{mask: []byte("\xFF\xFF\x00\x00"), pat: []byte("\xFE\xFF\x00\x00"), ct: "text/plain; charset=utf-16be"},
80 &maskedSig{mask: []byte("\xFF\xFF\x00\x00"), pat: []byte("\xFF\xFE\x00\x00"), ct: "text/plain; charset=utf-16le"},
81 &maskedSig{mask: []byte("\xFF\xFF\xFF\x00"), pat: []byte("\xEF\xBB\xBF\x00"), ct: "text/plain; charset=utf-8"},
82
83 &exactSig{[]byte("GIF87a"), "image/gif"},
84 &exactSig{[]byte("GIF89a"), "image/gif"},
85 &exactSig{[]byte("\x89\x50\x4E\x47\x0D\x0A\x1A\x0A"), "image/png"},
86 &exactSig{[]byte("\xFF\xD8\xFF"), "image/jpeg"},
87 &exactSig{[]byte("BM"), "image/bmp"},
88 &maskedSig{
89 mask: []byte("\xFF\xFF\xFF\xFF\x00\x00\x00\x00\xFF\xFF\xFF\xFF\xFF\xFF"),
90 pat: []byte("RIFF\x00\x00\x00\x00WEBPVP"),
91 ct: "image/webp",
92 },
93 &exactSig{[]byte("\x00\x00\x01\x00"), "image/vnd.microsoft.icon"},
Brent Austinba3052e2015-04-21 16:08:23 -0700[diff] [blame]94 &maskedSig{
95 mask: []byte("\xFF\xFF\xFF\xFF\x00\x00\x00\x00\xFF\xFF\xFF\xFF"),
96 pat: []byte("RIFF\x00\x00\x00\x00WAVE"),
97 ct: "audio/wave",
98 },
Dan Willemsen38f2dba2016-07-08 14:54:35 -0700[diff] [blame]99 &maskedSig{
100 mask: []byte("\xFF\xFF\xFF\xFF\x00\x00\x00\x00\xFF\xFF\xFF\xFF"),
101 pat: []byte("FORM\x00\x00\x00\x00AIFF"),
102 ct: "audio/aiff",
103 },
104 &maskedSig{
105 mask: []byte("\xFF\xFF\xFF\xFF"),
106 pat: []byte(".snd"),
107 ct: "audio/basic",
108 },
109 &maskedSig{
110 mask: []byte("OggS\x00"),
111 pat: []byte("\x4F\x67\x67\x53\x00"),
112 ct: "application/ogg",
113 },
114 &maskedSig{
115 mask: []byte("\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF"),
116 pat: []byte("MThd\x00\x00\x00\x06"),
117 ct: "audio/midi",
118 },
119 &maskedSig{
120 mask: []byte("\xFF\xFF\xFF"),
121 pat: []byte("ID3"),
122 ct: "audio/mpeg",
123 },
124 &maskedSig{
125 mask: []byte("\xFF\xFF\xFF\xFF\x00\x00\x00\x00\xFF\xFF\xFF\xFF"),
126 pat: []byte("RIFF\x00\x00\x00\x00AVI "),
127 ct: "video/avi",
128 },
Brent Austinba3052e2015-04-21 16:08:23 -0700[diff] [blame]129 &exactSig{[]byte("\x1A\x45\xDF\xA3"), "video/webm"},
130 &exactSig{[]byte("\x52\x61\x72\x20\x1A\x07\x00"), "application/x-rar-compressed"},
131 &exactSig{[]byte("\x50\x4B\x03\x04"), "application/zip"},
132 &exactSig{[]byte("\x1F\x8B\x08"), "application/x-gzip"},
133
Dan Willemsen38f2dba2016-07-08 14:54:35 -0700[diff] [blame]134 mp4Sig{},
Brent Austinba3052e2015-04-21 16:08:23 -0700[diff] [blame]135
Dan Willemsen38f2dba2016-07-08 14:54:35 -0700[diff] [blame]136 textSig{}, // should be last
Brent Austinba3052e2015-04-21 16:08:23 -0700[diff] [blame]137}
138
139type exactSig struct {
140 sig []byte
141 ct string
142}
143
144func (e *exactSig) match(data []byte, firstNonWS int) string {
145 if bytes.HasPrefix(data, e.sig) {
146 return e.ct
147 }
148 return ""
149}
150
151type maskedSig struct {
152 mask, pat []byte
153 skipWS bool
154 ct string
155}
156
157func (m *maskedSig) match(data []byte, firstNonWS int) string {
Dan Willemsen38f2dba2016-07-08 14:54:35 -0700[diff] [blame]158 // pattern matching algorithm section 6
159 // https://mimesniff.spec.whatwg.org/#pattern-matching-algorithm
160
Brent Austinba3052e2015-04-21 16:08:23 -0700[diff] [blame]161 if m.skipWS {
162 data = data[firstNonWS:]
163 }
Dan Willemsen38f2dba2016-07-08 14:54:35 -0700[diff] [blame]164 if len(m.pat) != len(m.mask) {
165 return ""
166 }
Brent Austinba3052e2015-04-21 16:08:23 -0700[diff] [blame]167 if len(data) < len(m.mask) {
168 return ""
169 }
170 for i, mask := range m.mask {
171 db := data[i] & mask
172 if db != m.pat[i] {
173 return ""
174 }
175 }
176 return m.ct
177}
178
179type htmlSig []byte
180
181func (h htmlSig) match(data []byte, firstNonWS int) string {
182 data = data[firstNonWS:]
183 if len(data) < len(h)+1 {
184 return ""
185 }
186 for i, b := range h {
187 db := data[i]
188 if 'A' <= b && b <= 'Z' {
189 db &= 0xDF
190 }
191 if b != db {
192 return ""
193 }
194 }
195 // Next byte must be space or right angle bracket.
196 if db := data[len(h)]; db != ' ' && db != '>' {
197 return ""
198 }
199 return "text/html; charset=utf-8"
200}
201
Dan Willemsen09eb3b12015-09-16 14:34:17 -0700[diff] [blame]202var mp4ftype = []byte("ftyp")
Dan Willemsen38f2dba2016-07-08 14:54:35 -0700[diff] [blame]203var mp4 = []byte("mp4")
Dan Willemsen09eb3b12015-09-16 14:34:17 -0700[diff] [blame]204
Dan Willemsen38f2dba2016-07-08 14:54:35 -0700[diff] [blame]205type mp4Sig struct{}
Brent Austinba3052e2015-04-21 16:08:23 -0700[diff] [blame]206
207func (mp4Sig) match(data []byte, firstNonWS int) string {
Dan Willemsen38f2dba2016-07-08 14:54:35 -0700[diff] [blame]208 // https://mimesniff.spec.whatwg.org/#signature-for-mp4
209 // c.f. section 6.2.1
210 if len(data) < 12 {
Brent Austinba3052e2015-04-21 16:08:23 -0700[diff] [blame]211 return ""
212 }
213 boxSize := int(binary.BigEndian.Uint32(data[:4]))
214 if boxSize%4 != 0 || len(data) < boxSize {
215 return ""
216 }
Dan Willemsen09eb3b12015-09-16 14:34:17 -0700[diff] [blame]217 if !bytes.Equal(data[4:8], mp4ftype) {
Brent Austinba3052e2015-04-21 16:08:23 -0700[diff] [blame]218 return ""
219 }
220 for st := 8; st < boxSize; st += 4 {
221 if st == 12 {
222 // minor version number
223 continue
224 }
Dan Willemsen38f2dba2016-07-08 14:54:35 -0700[diff] [blame]225 if bytes.Equal(data[st:st+3], mp4) {
Brent Austinba3052e2015-04-21 16:08:23 -0700[diff] [blame]226 return "video/mp4"
Brent Austinba3052e2015-04-21 16:08:23 -0700[diff] [blame]227 }
228 }
229 return ""
230}
231
Dan Willemsen38f2dba2016-07-08 14:54:35 -0700[diff] [blame]232type textSig struct{}
Brent Austinba3052e2015-04-21 16:08:23 -0700[diff] [blame]233
234func (textSig) match(data []byte, firstNonWS int) string {
235 // c.f. section 5, step 4.
236 for _, b := range data[firstNonWS:] {
237 switch {
Dan Willemsen38f2dba2016-07-08 14:54:35 -0700[diff] [blame]238 case b <= 0x08,
Brent Austinba3052e2015-04-21 16:08:23 -0700[diff] [blame]239 b == 0x0B,
240 0x0E <= b && b <= 0x1A,
241 0x1C <= b && b <= 0x1F:
242 return ""
243 }
244 }
245 return "text/plain; charset=utf-8"
246}