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LibWeb: Prevent OOB access in HTMLEncodingDetection for input of '</'

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Previously, this never checked if `position + 2` was valid. This
slightly reorders the loop so all indices are checked.

Fixes #22163
This commit is contained in:
MacDue 2024-01-04 11:22:20 +00:00 • committed by Andreas Kling
parent 3f52d6045a
commit 5e973fca0b
3 changed files with 17 additions and 4 deletions
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12
Tests/LibWeb/Layout/expected/incomplete-input-no-newline-at-eof-should-not-crash.txt Normal file
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@ -0,0 +1,12 @@
Viewport <#document> at (0,0) content-size 800x600 children: not-inline
BlockContainer <html> at (0,0) content-size 800x600 [BFC] children: not-inline
BlockContainer <body> at (8,8) content-size 784x17.46875 children: inline
line 0 width: 14.65625, height: 17.46875, bottom: 17.46875, baseline: 13.53125
frag 0 from TextNode start: 0, length: 2, rect: [8,8 14.65625x17.46875]
"</"
TextNode <#text>
ViewportPaintable (Viewport<#document>) [0,0 800x600]
PaintableWithLines (BlockContainer<HTML>) [0,0 800x600]
PaintableWithLines (BlockContainer<BODY>) [8,8 784x17.46875]
TextPaintable (TextNode<#text>)

1
Tests/LibWeb/Layout/input/incomplete-input-no-newline-at-eof-should-not-crash.html Normal file
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@ -0,0 +1 @@
</

8
Userland/Libraries/LibWeb/HTML/Parser/HTMLEncodingDetection.cpp
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@ -321,12 +321,12 @@ Optional<ByteString> run_prescan_byte_stream_algorithm(DOM::Document& document,
prescan_skip_whitespace_and_slashes(input, position);
while (prescan_get_attribute(document, input, position)) { };
} else if (!prescan_should_abort(input, position + 1) && input[position] == '<' && (input[position + 1] == '!' || input[position + 1] == '/' || input[position + 1] == '?')) {
position += 2;
while (input[position] != '>') {
++position;
position += 1;
do {
position += 1;
if (prescan_should_abort(input, position))
return {};
}
} while (input[position] != '>');
} else {
// Do nothing.
}