Fix unsigned underflow in SimpleString::subString() on empty strings · cpputest/cpputest@a5270d6 · GitHub

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94xhn

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basvodde

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Fix unsigned underflow in SimpleString::subString() on empty strings

subString(beginPos, amount) rejected out-of-range beginPos with `if (beginPos > size()-1) return "";`. Since size() returns size_t, calling this on an empty string (size() == 0) makes size()-1 wrap around to SIZE_MAX, so the bounds check is defeated for any beginPos and the function falls through to an out-of-bounds read of the string's internal buffer. Use `beginPos >= size()` instead, which is mathematically equivalent to the original check for every size() >= 1 and additionally handles size() == 0 correctly.

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‎src/CppUTest/SimpleString.cpp‎

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+1-1Lines changed: 1 addition & 1 deletion

Original file line number	Diff line number	Diff line change
@@ -580,7 +580,7 @@ void SimpleString::padStringsToSameLength(SimpleString& str1, SimpleString& str2
580	580
581	581	SimpleString SimpleString::subString(size_t beginPos, size_t amount) const
582	582	{
583		- if (beginPos > size()-1) return "";
	583	+ if (beginPos >= size()) return "";
584	584
585	585	SimpleString newString = getBuffer() + beginPos;
586	586

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