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Explicitly set max supported dirEntry size #875 (#876)

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Jaifroid 2022-08-04 15:29:07 +01:00 committed by GitHub
parent 7b4a62bc64
commit d76e09ff30
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1 changed files with 22 additions and 5 deletions
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www/js/lib/zimfile.js
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@ -21,6 +21,14 @@
*/ */
'use strict'; 'use strict';
/**
* This code makes an assumption that no Directory Entry will be larger that MAX_SUPPORTED_DIRENTRY_SIZE bytes.
* If a larger dirEntry is encountered, a warning will display in console. Increase this value if necessary.
* See https://stackoverflow.com/questions/417142/what-is-the-maximum-length-of-a-url-in-different-browsers to understand
* why 5120 has been chosen here (maximum that IE11 can deal with in code).
*/
const MAX_SUPPORTED_DIRENTRY_SIZE = 5120;
/** /**
* Add Polyfill currently required by IE11 to run zstddec-asm and xzdec-asm * Add Polyfill currently required by IE11 to run zstddec-asm and xzdec-asm
* See https://github.com/emscripten-core/emscripten/issues/14700 * See https://github.com/emscripten-core/emscripten/issues/14700
@ -171,7 +179,7 @@ define(['xzdec_wrapper', 'zstddec_wrapper', 'util', 'utf8', 'zimDirEntry', 'file
*/ */
ZIMFile.prototype.dirEntry = function (offset) { ZIMFile.prototype.dirEntry = function (offset) {
var that = this; var that = this;
return this._readSlice(offset, 2048).then(function (data) { return this._readSlice(offset, MAX_SUPPORTED_DIRENTRY_SIZE).then(function (data) {
var dirEntry = { var dirEntry = {
offset: offset, offset: offset,
mimetypeInteger: readInt(data, 0, 2), mimetypeInteger: readInt(data, 0, 2),
@ -187,9 +195,18 @@ define(['xzdec_wrapper', 'zstddec_wrapper', 'util', 'utf8', 'zimDirEntry', 'file
var pos = dirEntry.redirect ? 12 : 16; var pos = dirEntry.redirect ? 12 : 16;
if (data.subarray) { if (data.subarray) {
dirEntry.url = utf8.parse(data.subarray(pos), true); dirEntry.url = utf8.parse(data.subarray(pos), true);
while (data[pos] !== 0) for (pos; pos <= MAX_SUPPORTED_DIRENTRY_SIZE; pos++) {
pos++; if (data[pos] === 0) break;
}
if (data[pos] === 0) {
dirEntry.title = utf8.parse(data.subarray(pos + 1), true); dirEntry.title = utf8.parse(data.subarray(pos + 1), true);
} else {
// DEV: If you encounter this warning in console, it means that a very large dirEntry.url has exceeded the maximum supported
// dirEntry size. Consider increasing MAX_SUPPORTED_DIRENTRY_SIZE if such warnings are encountered regularly with a ZIM.
console.warn('WARNING! A Directory Entry URL larger than ' + MAX_SUPPORTED_DIRENTRY_SIZE + ' bytes was encountered! ' +
'The dirEntry.url is likely to be invalid.', dirEntry.url
);
}
return new zimDirEntry.DirEntry(that, dirEntry); return new zimDirEntry.DirEntry(that, dirEntry);
} }
}); });