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Fix A11y EndExclusive Error for Move & Expand (#7677)

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`EndExclusive` represents the end of the buffer. This is designed to not
point to any data on the buffer. UiaTextRange would point to this
`EndExclusive` and then attempt to move based on it. However, since it
does not point to any data, it could experience undefined behavior or
(inevitably) crash from running out of bounds.

This PR specifically checks for expansion and movement at that point,
and prevents us from moving beyond it. There are plans in the future to
define the "end" as the last character in the buffer. Until then, this
solution will suffice and provide correct behavior that doesn't crash.

## Validation Steps Performed
Performed the referenced bugs' repro steps and added test coverage.

Closes MSFT-20458595
Closes #7663
Closes #7664
This commit is contained in:
Carlos Zamora 2020-09-23 13:06:18 -07:00 committed by GitHub
parent 9539ec3679
commit 40893b2823
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GPG key ID: 4AEE18F83AFDEB23
3 changed files with 142 additions and 26 deletions
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39
src/buffer/out/textBuffer.cpp
View file

@ -996,19 +996,29 @@ const COORD TextBuffer::GetWordStart(const COORD target, const std::wstring_view
// so the words in the example include ["word ", "other "]
// NOTE: the start anchor (this one) is inclusive, whereas the end anchor (GetWordEnd) is exclusive
// can't expand left
if (target.X == GetSize().Left())
#pragma warning(suppress : 26496)
// GH#7664: Treat EndExclusive as EndInclusive so
// that it actually points to a space in the buffer
auto copy{ target };
const auto bufferSize{ GetSize() };
if (target == bufferSize.Origin())
{
// can't expand left
return target;
}
else if (target == bufferSize.EndExclusive())
{
// treat EndExclusive as EndInclusive
copy = { bufferSize.RightInclusive(), bufferSize.BottomInclusive() };
}
if (accessibilityMode)
{
return _GetWordStartForAccessibility(target, wordDelimiters);
return _GetWordStartForAccessibility(copy, wordDelimiters);
}
else
{
return _GetWordStartForSelection(target, wordDelimiters);
return _GetWordStartForSelection(copy, wordDelimiters);
}
}
@ -1108,6 +1118,12 @@ const COORD TextBuffer::GetWordEnd(const COORD target, const std::wstring_view w
// so the words in the example include ["word ", "other "]
// NOTE: the end anchor (this one) is exclusive, whereas the start anchor (GetWordStart) is inclusive
// Already at the end. Can't move forward.
if (target == GetSize().EndExclusive())
{
return target;
}
if (accessibilityMode)
{
return _GetWordEndForAccessibility(target, wordDelimiters);
@ -1243,6 +1259,12 @@ bool TextBuffer::MoveToNextWord(COORD& pos, const std::wstring_view wordDelimite
auto copy = pos;
const auto bufferSize = GetSize();
// Already at the end. Can't move forward.
if (pos == bufferSize.EndExclusive())
{
return false;
}
// started on a word, continue until the end of the word
while (_GetDelimiterClassAt(copy, wordDelimiters) == DelimiterClass::RegularChar)
{
@ -1287,7 +1309,14 @@ bool TextBuffer::MoveToNextWord(COORD& pos, const std::wstring_view wordDelimite
bool TextBuffer::MoveToPreviousWord(COORD& pos, std::wstring_view wordDelimiters) const
{
auto copy = pos;
auto bufferSize = GetSize();
const auto bufferSize{ GetSize() };
// GH#7663: Treat EndExclusive as EndInclusive so
// that it actually points to a space in the buffer
if (pos == bufferSize.EndExclusive())
{
copy = { bufferSize.RightInclusive(), bufferSize.BottomInclusive() };
}
// started on whitespace/delimiter, continue until the end of the previous word
while (_GetDelimiterClassAt(copy, wordDelimiters) != DelimiterClass::RegularChar)

2
src/host/ut_host/TextBufferTests.cpp
View file

@ -2065,7 +2065,7 @@ void TextBufferTests::GetWordBoundaries()
{ { 79, 0 }, {{ 10, 0 }, { 5, 0 }} },
// tests for second line of text
{ { 0, 1 }, {{ 0, 1 }, { 0, 1 }} },
{ { 0, 1 }, {{ 0, 1 }, { 5, 0 }} },
{ { 1, 1 }, {{ 0, 1 }, { 5, 0 }} },
{ { 2, 1 }, {{ 2, 1 }, { 2, 1 }} },
{ { 3, 1 }, {{ 2, 1 }, { 2, 1 }} },

127
src/interactivity/win32/ut_interactivity_win32/UiaTextRangeTests.cpp
View file

@ -106,6 +106,26 @@ class UiaTextRangeTests
ExpectedResult expected;
};
static constexpr wchar_t* toString(TextUnit unit) noexcept
{
// if a format is not supported, it goes to the next largest text unit
switch (unit)
{
case TextUnit_Character:
return L"Character";
case TextUnit_Format:
case TextUnit_Word:
return L"Word";
case TextUnit_Line:
return L"Line";
case TextUnit_Paragraph:
case TextUnit_Page:
case TextUnit_Document:
default:
return L"Document";
}
};
TEST_METHOD_SETUP(MethodSetup)
{
CONSOLE_INFORMATION& gci = Microsoft::Console::Interactivity::ServiceLocator::LocateGlobals().getConsoleInformation();
@ -304,26 +324,6 @@ class UiaTextRangeTests
// based on the text unit we are testing
constexpr TextUnit supportedUnits[] = { TextUnit_Character, TextUnit_Word, TextUnit_Line, TextUnit_Document };
auto toString = [&](TextUnit unit) {
// if a format is not supported, it goes to the next largest text unit
switch (unit)
{
case TextUnit_Character:
return L"Character";
case TextUnit_Format:
case TextUnit_Word:
return L"Word";
case TextUnit_Line:
return L"Line";
case TextUnit_Paragraph:
case TextUnit_Page:
case TextUnit_Document:
return L"Document";
default:
throw E_INVALIDARG;
}
};
struct TextUnitBoundaries
{
COORD start;
@ -1103,4 +1103,91 @@ class UiaTextRangeTests
VERIFY_ARE_EQUAL(test.expected.end, utr->_end);
}
}
TEST_METHOD(ExpansionAtExclusiveEnd)
{
// GH#7664: When attempting to expand to an enclosing unit
// at the end exclusive, the UTR should refuse to move past
// the end.
const auto bufferSize{ _pTextBuffer->GetSize() };
const til::point endInclusive{ bufferSize.RightInclusive(), bufferSize.BottomInclusive() };
const auto endExclusive{ bufferSize.EndExclusive() };
// Iterate over each TextUnit. If the we don't support
// the given TextUnit, we're supposed to fallback
// to the last one that was defined anyways.
Microsoft::WRL::ComPtr<UiaTextRange> utr;
for (int unit = TextUnit::TextUnit_Character; unit != TextUnit::TextUnit_Document; ++unit)
{
Log::Comment(NoThrowString().Format(L"%s", toString(static_cast<TextUnit>(unit))));
// Create a degenerate UTR at EndExclusive
THROW_IF_FAILED(Microsoft::WRL::MakeAndInitialize<UiaTextRange>(&utr, _pUiaData, &_dummyProvider, endInclusive, endExclusive));
THROW_IF_FAILED(utr->ExpandToEnclosingUnit(static_cast<TextUnit>(unit)));
VERIFY_ARE_EQUAL(endExclusive, utr->_end);
}
}
TEST_METHOD(MovementAtExclusiveEnd)
{
// GH#7663: When attempting to move from end exclusive,
// the UTR should refuse to move past the end.
const auto bufferSize{ _pTextBuffer->GetSize() };
const til::point endInclusive = { bufferSize.RightInclusive(), bufferSize.BottomInclusive() };
const auto endExclusive{ bufferSize.EndExclusive() };
// Iterate over each TextUnit. If the we don't support
// the given TextUnit, we're supposed to fallback
// to the last one that was defined anyways.
Microsoft::WRL::ComPtr<UiaTextRange> utr;
int moveAmt;
for (int unit = TextUnit::TextUnit_Character; unit != TextUnit::TextUnit_Document; ++unit)
{
Log::Comment(NoThrowString().Format(L"Forward by %s", toString(static_cast<TextUnit>(unit))));
// Create a degenerate UTR at EndExclusive
THROW_IF_FAILED(Microsoft::WRL::MakeAndInitialize<UiaTextRange>(&utr, _pUiaData, &_dummyProvider, endInclusive, endExclusive));
THROW_IF_FAILED(utr->Move(static_cast<TextUnit>(unit), 1, &moveAmt));
VERIFY_ARE_EQUAL(endExclusive, utr->_end);
VERIFY_ARE_EQUAL(0, moveAmt);
}
// Verify that moving backwards still works properly
const COORD writeTarget{ 2, 2 };
_pTextBuffer->Write({ L"temp" }, writeTarget);
for (int unit = TextUnit::TextUnit_Character; unit != TextUnit::TextUnit_Document; ++unit)
{
COORD expectedEnd;
switch (static_cast<TextUnit>(unit))
{
case TextUnit::TextUnit_Character:
expectedEnd = endInclusive;
break;
case TextUnit::TextUnit_Word:
expectedEnd = writeTarget;
break;
case TextUnit::TextUnit_Line:
expectedEnd = endExclusive;
break;
case TextUnit::TextUnit_Document:
expectedEnd = bufferSize.Origin();
break;
default:
continue;
}
Log::Comment(NoThrowString().Format(L"Backwards by %s", toString(static_cast<TextUnit>(unit))));
// Create a degenerate UTR at EndExclusive
THROW_IF_FAILED(Microsoft::WRL::MakeAndInitialize<UiaTextRange>(&utr, _pUiaData, &_dummyProvider, endInclusive, endExclusive));
THROW_IF_FAILED(utr->Move(static_cast<TextUnit>(unit), -1, &moveAmt));
VERIFY_ARE_EQUAL(expectedEnd, utr->_end);
VERIFY_ARE_EQUAL(-1, moveAmt);
}
}
};