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netsurf/content/mimesniff.c
Vincent Sanders f39d78dc2e mimimal mime sniffing test
2017-03-20 00:48:11 +00:00

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/*
* Copyright 2011 John-Mark Bell <jmb@netsurf-browser.org>
*
* This file is part of NetSurf, http://www.netsurf-browser.org/
*
* NetSurf is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; version 2 of the License.
*
* NetSurf is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/**
* \file
* MIME type sniffer implementation
*
* Spec version: 2011-11-27
*/
#include <string.h>
#include <strings.h>
#include "utils/http.h"
#include "utils/utils.h"
#include "utils/corestrings.h"
#include "content/content_factory.h"
#include "content/mimesniff.h"
struct map_s {
const uint8_t *sig;
size_t len;
bool safe;
lwc_string **type;
};
static bool mimesniff__has_binary_octets(const uint8_t *data, size_t len)
{
const uint8_t *end = data + len;
while (data != end) {
const uint8_t c = *data;
/* Binary iff in C0 and not ESC, CR, FF, LF, HT */
if (c <= 0x1f && c != 0x1b && c != '\r' && c != '\f' &&
c != '\n' && c != '\t')
break;
data++;
}
return data != end;
}
static nserror mimesniff__match_mp4(const uint8_t *data, size_t len,
lwc_string **effective_type)
{
uint32_t box_size, i;
/* ISO/IEC 14496-12:2008 $4.3 says (effectively):
*
* struct ftyp_box {
* uint32_t size; (in octets, including size+type words)
* uint32_t type; (== 'ftyp')
* uint32_t major_brand;
* uint32_t minor_version;
* uint32_t compatible_brands[];
* }
*
* Note 1: A size of 0 implies that the length of the box is designated
* by the remaining input data (and thus may only occur in the last
* box in the input). We'll reject this below, as it's pointless
* sniffing input that contains no boxes other than 'ftyp'.
*
* Note 2: A size of 1 implies an additional uint64_t field after
* the type which contains the extended box size. We'll reject this,
* too, as it implies a minimum of (2^32 - 24) / 4 compatible brands,
* which is decidely unlikely.
*/
/* 12 reflects the minimum number of octets needed to sniff useful
* information out of an 'ftyp' box (i.e. the size, type,
* and major_brand words). */
if (len < 12)
return NSERROR_NOT_FOUND;
/* Box size is big-endian */
box_size = (data[0] << 24) | (data[1] << 16) | (data[2] << 8) | data[3];
/* Require that we can read the entire box, and reject bad box sizes */
if (len < box_size || box_size % 4 != 0)
return NSERROR_NOT_FOUND;
/* Ensure this is an 'ftyp' box */
if (data[4] != 'f' || data[5] != 't' ||
data[6] != 'y' || data[7] != 'p')
return NSERROR_NOT_FOUND;
/* Check if major brand begins with 'mp4' */
if (data[8] == 'm' && data[9] == 'p' && data[10] == '4') {
*effective_type = lwc_string_ref(corestring_lwc_video_mp4);
return NSERROR_OK;
}
/* Search each compatible brand in the box for "mp4" */
for (i = 16; i <= box_size - 4; i += 4) {
if (data[i] == 'm' &&
data[i+1] == 'p' &&
data[i+2] == '4') {
*effective_type = lwc_string_ref(corestring_lwc_video_mp4);
return NSERROR_OK;
}
}
return NSERROR_NOT_FOUND;
}
static nserror mimesniff__match_unknown_ws(const uint8_t *data, size_t len,
lwc_string **effective_type)
{
#define SIG(t, s, x) { (const uint8_t *) s, SLEN(s), x, t }
static const struct map_s ws_exact_match_types[] = {
SIG(&corestring_lwc_text_xml, "<?xml", false),
{ NULL, 0, false, NULL }
};
static const struct map_s ws_inexact_match_types[] = {
SIG(&corestring_lwc_text_html, "<!DOCTYPE HTML", false),
SIG(&corestring_lwc_text_html, "<HTML", false),
SIG(&corestring_lwc_text_html, "<HEAD", false),
SIG(&corestring_lwc_text_html, "<SCRIPT", false),
SIG(&corestring_lwc_text_html, "<IFRAME", false),
SIG(&corestring_lwc_text_html, "<H1", false),
SIG(&corestring_lwc_text_html, "<DIV", false),
SIG(&corestring_lwc_text_html, "<FONT", false),
SIG(&corestring_lwc_text_html, "<TABLE", false),
SIG(&corestring_lwc_text_html, "<A", false),
SIG(&corestring_lwc_text_html, "<STYLE", false),
SIG(&corestring_lwc_text_html, "<TITLE", false),
SIG(&corestring_lwc_text_html, "<B", false),
SIG(&corestring_lwc_text_html, "<BODY", false),
SIG(&corestring_lwc_text_html, "<BR", false),
SIG(&corestring_lwc_text_html, "<P", false),
SIG(&corestring_lwc_text_html, "<!--", false),
{ NULL, 0, false, NULL }
};
#undef SIG
const uint8_t *end = data + len;
const struct map_s *it;
/* Skip leading whitespace */
while (data != end) {
const uint8_t c = *data;
if (c != '\t' && c != '\n' && c != '\f' &&
c != '\r' && c != ' ')
break;
data++;
}
if (data == end)
return NSERROR_NOT_FOUND;
len = end - data;
for (it = ws_exact_match_types; it->sig != NULL; it++) {
if (it->len <= len && memcmp(data, it->sig, it->len) == 0) {
*effective_type = lwc_string_ref(*it->type);
return NSERROR_OK;
}
}
for (it = ws_inexact_match_types; it->sig != NULL; it++) {
/* +1 for trailing space or > */
if (len < it->len + 1)
continue;
if (strncasecmp((const char *) data,
(const char *) it->sig, it->len) == 0 &&
(data[it->len] == ' ' ||
data[it->len] == '>')) {
*effective_type = lwc_string_ref(*it->type);
return NSERROR_OK;
}
}
return NSERROR_NOT_FOUND;
}
static nserror mimesniff__match_unknown_bom(const uint8_t *data, size_t len,
lwc_string **effective_type)
{
#define SIG(t, s, x) { (const uint8_t *) s, SLEN(s), x, t }
static const struct map_s bom_match_types[] = {
SIG(&corestring_lwc_text_plain, "\xfe\xff", false),
SIG(&corestring_lwc_text_plain, "\xff\xfe", false),
SIG(&corestring_lwc_text_plain, "\xef\xbb\xbf", false),
{ NULL, 0, false, NULL }
};
#undef SIG
const struct map_s *it;
for (it = bom_match_types; it->sig != NULL; it++) {
if (it->len <= len && memcmp(data, it->sig, it->len) == 0) {
*effective_type = lwc_string_ref(*it->type);
return NSERROR_OK;
}
}
return NSERROR_NOT_FOUND;
}
static nserror mimesniff__match_unknown_riff(const uint8_t *data, size_t len,
lwc_string **effective_type)
{
#define SIG(t, s, x) { (const uint8_t *) s, SLEN(s), x, t }
static const struct map_s riff_match_types[] = {
SIG(&corestring_lwc_image_webp, "WEBPVP", true),
SIG(&corestring_lwc_audio_wave, "WAVE", true),
{ NULL, 0, false, NULL }
};
#undef SIG
const struct map_s *it;
for (it = riff_match_types; it->sig != NULL; it++) {
if (it->len + SLEN("RIFF????") <= len &&
memcmp(data, "RIFF", SLEN("RIFF")) == 0 &&
memcmp(data + SLEN("RIFF????"),
it->sig, it->len) == 0) {
*effective_type = lwc_string_ref(*it->type);
return NSERROR_OK;
}
}
return NSERROR_NOT_FOUND;
}
static nserror mimesniff__match_unknown_exact(const uint8_t *data, size_t len,
bool allow_unsafe, lwc_string **effective_type)
{
#define SIG(t, s, x) { (const uint8_t *) s, SLEN(s), x, t }
static const struct map_s exact_match_types[] = {
SIG(&corestring_lwc_image_gif, "GIF87a", true),
SIG(&corestring_lwc_image_gif, "GIF89a", true),
SIG(&corestring_lwc_image_png, "\x89PNG\r\n\x1a\n", true),
SIG(&corestring_lwc_image_jpeg, "\xff\xd8\xff", true),
SIG(&corestring_lwc_image_bmp, "BM", true),
SIG(&corestring_lwc_image_vnd_microsoft_icon, "\x00\x00\x01\x00", true),
SIG(&corestring_lwc_application_ogg, "OggS\x00", true),
SIG(&corestring_lwc_video_webm, "\x1a\x45\xdf\xa3", true),
SIG(&corestring_lwc_application_x_rar_compressed, "Rar \x1a\x07\x00", true),
SIG(&corestring_lwc_application_zip, "PK\x03\x04", true),
SIG(&corestring_lwc_application_x_gzip, "\x1f\x8b\x08", true),
SIG(&corestring_lwc_application_postscript, "%!PS-Adobe-",true),
SIG(&corestring_lwc_application_pdf, "%PDF-", false),
{ NULL, 0, false, NULL }
};
#undef SIG
const struct map_s *it;
for (it = exact_match_types; it->sig != NULL; it++) {
if (it->len <= len && memcmp(data, it->sig, it->len) == 0 &&
(allow_unsafe || it->safe)) {
*effective_type = lwc_string_ref(*it->type);
return NSERROR_OK;
}
}
return NSERROR_NOT_FOUND;
}
static nserror mimesniff__match_unknown(const uint8_t *data, size_t len,
bool allow_unsafe, lwc_string **effective_type)
{
if (mimesniff__match_unknown_exact(data, len, allow_unsafe,
effective_type) == NSERROR_OK)
return NSERROR_OK;
if (mimesniff__match_unknown_riff(data, len,
effective_type) == NSERROR_OK)
return NSERROR_OK;
if (allow_unsafe == false)
return NSERROR_NOT_FOUND;
if (mimesniff__match_unknown_bom(data, len,
effective_type) == NSERROR_OK)
return NSERROR_OK;
if (mimesniff__match_unknown_ws(data, len,
effective_type) == NSERROR_OK)
return NSERROR_OK;
if (mimesniff__match_mp4(data, len, effective_type) == NSERROR_OK)
return NSERROR_OK;
return NSERROR_NOT_FOUND;
}
static nserror mimesniff__compute_unknown(const uint8_t *data, size_t len,
lwc_string **effective_type)
{
if (data == NULL)
return NSERROR_NEED_DATA;
len = min(len, 512);
if (mimesniff__match_unknown(data, len, true,
effective_type) == NSERROR_OK) {
return NSERROR_OK;
}
if (mimesniff__has_binary_octets(data, len) == false) {
/* No binary octets => text/plain */
*effective_type = lwc_string_ref(corestring_lwc_text_plain);
return NSERROR_OK;
}
*effective_type = lwc_string_ref(corestring_lwc_application_octet_stream);
return NSERROR_OK;
}
static nserror mimesniff__compute_text_or_binary(const uint8_t *data,
size_t len, lwc_string **effective_type)
{
if (data == NULL) {
return NSERROR_NEED_DATA;
}
len = min(len, 512);
if (len >= 3 && ((data[0] == 0xfe && data[1] == 0xff) ||
(data[0] == 0xff && data[1] == 0xfe) ||
(data[0] == 0xef && data[1] == 0xbb &&
data[2] == 0xbf))) {
/* Found a BOM => text/plain */
*effective_type = lwc_string_ref(corestring_lwc_text_plain);
return NSERROR_OK;
}
if (mimesniff__has_binary_octets(data, len) == false) {
/* No binary octets => text/plain */
*effective_type = lwc_string_ref(corestring_lwc_text_plain);
return NSERROR_OK;
}
if (mimesniff__match_unknown(data, len, false,
effective_type) == NSERROR_OK)
return NSERROR_OK;
*effective_type = lwc_string_ref(corestring_lwc_application_octet_stream);
return NSERROR_OK;
}
static nserror mimesniff__compute_image(lwc_string *official_type,
const uint8_t *data, size_t len, lwc_string **effective_type)
{
#define SIG(t, s) { (const uint8_t *) s, SLEN(s), t }
static const struct it_s {
const uint8_t *sig;
size_t len;
lwc_string **type;
} image_types[] = {
SIG(&corestring_lwc_image_gif, "GIF87a"),
SIG(&corestring_lwc_image_gif, "GIF89a"),
SIG(&corestring_lwc_image_png, "\x89PNG\r\n\x1a\n"),
SIG(&corestring_lwc_image_jpeg, "\xff\xd8\xff"),
SIG(&corestring_lwc_image_bmp, "BM"),
SIG(&corestring_lwc_image_vnd_microsoft_icon, "\x00\x00\x01\x00"),
{ NULL, 0, NULL }
};
#undef SIG
const struct it_s *it;
if (data == NULL) {
lwc_string_unref(official_type);
return NSERROR_NEED_DATA;
}
for (it = image_types; it->sig != NULL; it++) {
if (it->len <= len && memcmp(data, it->sig, it->len) == 0) {
lwc_string_unref(official_type);
*effective_type = lwc_string_ref(*it->type);
return NSERROR_OK;
}
}
/* WebP has a signature that doesn't fit into the above table */
if (SLEN("RIFF????WEBPVP") <= len &&
memcmp(data, "RIFF", SLEN("RIFF")) == 0 &&
memcmp(data + SLEN("RIFF????"),
"WEBPVP", SLEN("WEBPVP")) == 0 ) {
lwc_string_unref(official_type);
*effective_type = lwc_string_ref(corestring_lwc_image_webp);
return NSERROR_OK;
}
*effective_type = official_type;
return NSERROR_OK;
}
static nserror mimesniff__compute_feed_or_html(const uint8_t *data,
size_t len, lwc_string **effective_type)
{
#define RDF_NS "http://www.w3.org/1999/02/22-rdf-syntax-ns#"
#define RSS_NS "http://purl.org/rss/1.0"
enum state_e {
BEFORE_BOM,
BEFORE_MARKUP,
MARKUP_START,
COMMENT_OR_DOCTYPE,
IN_COMMENT,
IN_DOCTYPE,
IN_PI,
IN_TAG,
IN_RDF
} state = BEFORE_BOM;
bool rdf = false, rss = false;
const uint8_t *end;
if (data == NULL)
return NSERROR_NEED_DATA;
end = data + min(len, 512);
while (data < end) {
const uint8_t c = *data;
#define MATCH(s) SLEN(s) <= (size_t) (end - data) && \
memcmp(data, s, SLEN(s)) == 0
switch (state) {
case BEFORE_BOM:
if (3 <= end - data && c == 0xef && data[1] == 0xbb &&
data[2] == 0xbf) {
data += 3;
}
state = BEFORE_MARKUP;
break;
case BEFORE_MARKUP:
if (c == '\t' || c == '\n' || c == '\r' || c == ' ')
data++;
else if (c != '<')
data = end;
else {
state = MARKUP_START;
data++;
}
break;
case MARKUP_START:
if (c == '!') {
state = COMMENT_OR_DOCTYPE;
data++;
} else if (c == '?') {
state = IN_PI;
data++;
} else {
/* Reconsume input */
state = IN_TAG;
}
break;
case COMMENT_OR_DOCTYPE:
if (2 <= end - data && c == '-' && data[1] == '-') {
state = IN_COMMENT;
data += 2;
} else {
/* Reconsume input */
state = IN_DOCTYPE;
}
break;
case IN_COMMENT:
if (3 <= end - data && c == '-' && data[1] == '-' &&
data[2] == '>') {
state = BEFORE_MARKUP;
data += 3;
} else
data++;
break;
case IN_DOCTYPE:
if (c == '>')
state = BEFORE_MARKUP;
data++;
break;
case IN_PI:
if (2 <= end - data && c == '?' && data[1] == '>') {
state = BEFORE_MARKUP;
data += 2;
} else
data++;
break;
case IN_TAG:
if (MATCH("rss")) {
*effective_type =
lwc_string_ref(corestring_lwc_application_rss_xml);
return NSERROR_OK;
} else if (MATCH("feed")) {
*effective_type =
lwc_string_ref(corestring_lwc_application_atom_xml);
return NSERROR_OK;
} else if (MATCH("rdf:RDF")) {
state = IN_RDF;
data += SLEN("rdf:RDF");
} else
data = end;
break;
case IN_RDF:
if (MATCH(RSS_NS)) {
rss = true;
data += SLEN(RSS_NS);
} else if (MATCH(RDF_NS)) {
rdf = true;
data += SLEN(RDF_NS);
} else
data++;
if (rdf && rss) {
*effective_type = lwc_string_ref(corestring_lwc_application_rss_xml);
return NSERROR_OK;
}
break;
}
#undef MATCH
}
*effective_type = lwc_string_ref(corestring_lwc_text_html);
return NSERROR_OK;
#undef RSS_NS
#undef RDF_NS
}
/* See mimesniff.h for documentation */
nserror
mimesniff_compute_effective_type(const char *content_type_header,
const uint8_t *data,
size_t len,
bool sniff_allowed,
bool image_only,
lwc_string **effective_type)
{
#define S(s) { s, SLEN(s) }
static const struct tt_s {
const char *data;
size_t len;
} text_types[] = {
S("text/plain"),
S("text/plain; charset=ISO-8859-1"),
S("text/plain; charset=iso-8859-1"),
S("text/plain; charset=UTF-8"),
{ NULL, 0 }
};
#undef S
size_t content_type_header_len;
http_content_type *ct;
const struct tt_s *tt;
bool match;
nserror error;
if (content_type_header == NULL) {
if (sniff_allowed == false) {
return NSERROR_NOT_FOUND;
}
/* No official type => unknown */
return mimesniff__compute_unknown(data, len, effective_type);
}
error = http_parse_content_type(content_type_header, &ct);
if (error != NSERROR_OK) {
if (sniff_allowed == false)
return NSERROR_NOT_FOUND;
/* Unparseable => unknown */
return mimesniff__compute_unknown(data, len, effective_type);
}
if (sniff_allowed == false) {
*effective_type = lwc_string_ref(ct->media_type);
http_content_type_destroy(ct);
return NSERROR_OK;
}
if (image_only) {
lwc_string *official_type;
if (lwc_string_caseless_isequal(ct->media_type,
corestring_lwc_image_svg,
&match) == lwc_error_ok && match) {
*effective_type = lwc_string_ref(corestring_lwc_image_svg);
http_content_type_destroy(ct);
return NSERROR_OK;
}
official_type = lwc_string_ref(ct->media_type);
http_content_type_destroy(ct);
return mimesniff__compute_image(official_type,
data, len, effective_type);
}
content_type_header_len = strlen(content_type_header);
/* Look for text types */
for (tt = text_types; tt->data != NULL; tt++) {
if (tt->len == content_type_header_len &&
memcmp(tt->data,
content_type_header,
content_type_header_len) == 0) {
http_content_type_destroy(ct);
return mimesniff__compute_text_or_binary(data, len,
effective_type);
}
}
/* unknown/unknown, application/unknown, * / * */
if ((lwc_string_caseless_isequal(ct->media_type,
corestring_lwc_unknown_unknown,
&match) == lwc_error_ok && match) ||
(lwc_string_caseless_isequal(ct->media_type,
corestring_lwc_application_unknown,
&match) == lwc_error_ok && match) ||
(lwc_string_caseless_isequal(ct->media_type,
corestring_lwc_any,
&match) == lwc_error_ok && match)) {
http_content_type_destroy(ct);
return mimesniff__compute_unknown(data, len, effective_type);
}
/* +xml */
if (lwc_string_length(ct->media_type) > SLEN("+xml") &&
strncasecmp(lwc_string_data(ct->media_type) +
lwc_string_length(ct->media_type) -
SLEN("+xml"),
"+xml", SLEN("+xml")) == 0) {
/* Use official type */
*effective_type = lwc_string_ref(ct->media_type);
http_content_type_destroy(ct);
return NSERROR_OK;
}
/* text/xml, application/xml */
if ((lwc_string_caseless_isequal(ct->media_type,
corestring_lwc_text_xml,
&match) == lwc_error_ok && match) ||
(lwc_string_caseless_isequal(ct->media_type,
corestring_lwc_application_xml,
&match) == lwc_error_ok && match)) {
/* Use official type */
*effective_type = lwc_string_ref(ct->media_type);
http_content_type_destroy(ct);
return NSERROR_OK;
}
/* Image types */
if (content_factory_type_from_mime_type(ct->media_type) ==
CONTENT_IMAGE) {
lwc_string *official_type = lwc_string_ref(ct->media_type);
http_content_type_destroy(ct);
return mimesniff__compute_image(official_type,
data, len, effective_type);
}
/* text/html */
if ((lwc_string_caseless_isequal(ct->media_type,
corestring_lwc_text_html,
&match) == lwc_error_ok && match)) {
http_content_type_destroy(ct);
return mimesniff__compute_feed_or_html(data, len,
effective_type);
}
/* Use official type */
*effective_type = lwc_string_ref(ct->media_type);
http_content_type_destroy(ct);
return NSERROR_OK;
}
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