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Check for valid length and simplify BOM check (#247)

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This commit is contained in:
Albrecht Schlosser 2021-07-03 18:59:19 +02:00
parent 6361e7d1b7
commit ce26f04f2d
1 changed files with 17 additions and 2 deletions
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19
src/fl_images_core.cxx
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@ -145,8 +145,23 @@ fl_check_images(const char *name, // I - Filename
buf += lutf8; count -= lutf8;
}
if ((count >= 5 && memcmp(buf, "<?xml", 5) == 0) ||
(count >= 4 && memcmp(buf, "<svg", 4) == 0))
// Check if we have a UTF-8 BOM in the first three bytes (issue #247).
// If yes we need at least 5 more bytes to recognize the signature.
// Note: BOM (Byte Order Marker) in UTF-8 is not recommended but allowed.
if (count >= 8) {
const uchar bom[3] = { 0xef, 0xbb, 0xbf };
if (memcmp(buf, bom, 3) == 0) {
buf += 3;
count -= 3;
}
}
// Check svg or xml signature
if ((count >= 5 &&
(memcmp(buf, "<?xml", 5) == 0 ||
memcmp(buf, "<svg ", 5) == 0)))
return new Fl_SVG_Image(name);
#endif // FLTK_USE_SVG