Problem 1770. singularity 2.0 (hard)

Created by Alfonso Nieto-Castanon

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{"relationships":[{"relationshipType":"http://schemas.mathworks.com/matlab/code/2013/relationships/document","targetMode":"","relationshipId":"rId1","target":"/matlab/document.xml"},{"relationshipType":"http://schemas.mathworks.com/matlab/code/2013/relationships/output","targetMode":"","relationshipId":"rId2","target":"/matlab/output.xml"}],"parts":[{"partUri":"/matlab/document.xml","relationship":[],"contentType":"application/vnd.mathworks.matlab.code.document+xml","content":"<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<w:document xmlns:w=\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\"><w:body><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>This problem is the continuation of problem</w:t></w:r><w:r><w:t> </w:t></w:r><w:hyperlink w:docLocation=\"http://www.mathworks.com/matlabcentral/cody/problems/1769-singularity-2-0-easier\"><w:r><w:t>Singularity 2.0 (easier)</w:t></w:r></w:hyperlink></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>If you have been in Cody long enough you have probably run across some badly constructed problems and test suites.</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>This problem, I believe, represents an apparently impossible scenario. Yet, it is possible to solve it. Do you know how?</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:rPr><w:b/></w:rPr><w:t>Description:</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>This is this problem's testsuite:</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"code\"/></w:pPr><w:r><w:t><![CDATA[ myfunction();\n [a,b]=1; % oops...\n assert(isequal(a,b));]]></w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>As you may notice, the second line is not a proper assignment, so the testsuite will break at that point, and will return an error message:</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:rPr><w:rFonts w:cs=\"monospace\"/></w:rPr><w:t>??? Too many output arguments.</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>Typical hacks work by overloading some function in the evaluation code (e.g. assert hack). Unfortunately, as far as I know, assignment operators cannot be overloaded in Matlab. Is there something</w:t></w:r><w:r><w:t> </w:t></w:r><w:r><w:rPr><w:rFonts w:cs=\"monospace\"/></w:rPr><w:t>myfunction</w:t></w:r><w:r><w:t> could do to still solve this problem?</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:rPr><w:b/></w:rPr><w:t>Hint</w:t></w:r><w:r><w:t>:</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>You may use a similar trick as before but now targeting a vulnerability in the function</w:t></w:r><w:r><w:t> </w:t></w:r><w:r><w:rPr><w:rFonts w:cs=\"monospace\"/></w:rPr><w:t>verifyCode</w:t></w:r><w:r><w:t> instead of in the testsuite. For simplicity, here is the relevant portion of the verifyCode.m file (the function that evaluates and scores Cody problems):</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"code\"/></w:pPr><w:r><w:t><![CDATA[ function testSuiteResults = verifyCode( sourceFile, testFile )\n %VERIFYCODE Evaluates and verifies MATLAB Code against provided test suite.\n % TESTSUITERESULTS = VERIFYCODE(SOURCEFILE, TESTFILE) evaluates SOURCEFILE against\n % TESTFILE and returns the results.\n \n % Score it\n score = calculateSize(sourceFile);\n % Load the test file\n code = fileread(testFile);\n % Split it into cells\n code2 = regexprep(code,'\\n%%','\\nxxx-cellbreak-xxx%%');\n cellList = regexp(code2,'xxx-cellbreak-xxx','split');\n % Test each cell\n % Each testpoint structure\n % testPoint = struct(...\n % 'pass', false, ...\n % 'code', '', ...\n % 'output', '');\n testSuite = struct([]);\n [containsIllegalFcnFlag, illegalFcnMessage] = containsIllegalFcn(sourceFile);\n for countVariable = 1:length(cellList)\n cellCode = cellList{countVariable};\n cleanCellCode = cleanCode(cellCode);\n % Test is guilty until proven successful\n pass = false;\n % Run it\n try\n output = evaluateCode(cleanCellCode);\n pass = true;\n catch me\n output = ['Error: ' me.message];\n end\n if containsIllegalFcnFlag\n pass = false;\n output = illegalFcnMessage;\n end\n cellOutput = cleanCode(output);\n testSuite(countVariable).code = cleanCellCode;\n testSuite(countVariable).output = cellOutput;\n testSuite(countVariable).pass = pass;\n end\n % Set up data structure to return\n testSuiteResults = struct(...\n 'pass', false, ...\n 'score', 0, ...\n 'functions', [], ...\n 'testPoints', struct([]));\n % Populate the result struct\n % If any test point is failed, sets the overall pass status to false.\n testSuiteResults.pass = all([testSuite.pass]);\n % sets the score\n testSuiteResults.score = sprintf('%d',score);\n % Set test points\n testSuiteResults.testPoints = testSuite;\n % Set functions points\n testSuiteResults.functions = findFcns(sourceFile,'file');\n end]]></w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>Previous problem in this series:</w:t></w:r><w:r><w:t> </w:t></w:r><w:hyperlink w:docLocation=\"http://www.mathworks.com/matlabcentral/cody/problems/1769-singularity-2-0-easier\"><w:r><w:t>Singularity 2.0 (easier)</w:t></w:r></w:hyperlink></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>Next problem in this series:</w:t></w:r><w:r><w:t> </w:t></w:r><w:hyperlink w:docLocation=\"http://www.mathworks.com/matlabcentral/cody/problems/1764-singularity-2-0\"><w:r><w:t>Singularity 2.0 (really hard)</w:t></w:r></w:hyperlink></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:rPr><w:i/></w:rPr><w:t>Copyright 1984-2012 The MathWorks, Inc.</w:t></w:r></w:p></w:body></w:document>"},{"partUri":"/matlab/output.xml","contentType":"text/xml","content":"<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\" ?><embeddedOutputs><metaData><evaluationState>manual</evaluationState><layoutState>code</layoutState><outputStatus>ready</outputStatus></metaData><outputArray type=\"array\"/><regionArray type=\"array\"/></embeddedOutputs>"}]}

This problem is the continuation of problem <a href = "http://www.mathworks.com/matlabcentral/cody/problems/1769-singularity-2-0-easier">Singularity 2.0 (easier)</a>If you have been in Cody long enough you have probably run across some badly constructed problems and test suites.This problem, I believe, represents an apparently impossible scenario. Yet, it is possible to solve it. Do you know how?Description:This is this problem's testsuite:<pre> %%
 myfunction();
 [a,b]=1; % oops...
 assert(isequal(a,b));</pre>As you may notice, the second line is not a proper assignment, so the testsuite will break at that point, and will return an error message:<tt>??? Too many output arguments.</tt>Typical hacks work by overloading some function in the evaluation code (e.g. assert hack). Unfortunately, as far as I know, assignment operators cannot be overloaded in Matlab. Is there something <tt>myfunction</tt> could do to still solve this problem?Hint:You may use a similar trick as before but now targeting a vulnerability in the function <tt>verifyCode</tt> instead of in the testsuite. For simplicity, here is the relevant portion of the verifyCode.m file (the function that evaluates and scores Cody problems):<pre> function testSuiteResults = verifyCode( sourceFile, testFile )
 %VERIFYCODE Evaluates and verifies MATLAB Code against provided test suite.
 % TESTSUITERESULTS = VERIFYCODE(SOURCEFILE, TESTFILE) evaluates SOURCEFILE against
 % TESTFILE and returns the results.
 % Copyright 1984-2012 The MathWorks, Inc.
 % Score it
 score = calculateSize(sourceFile);
 % Load the test file
 code = fileread(testFile);
 % Split it into cells
 code2 = regexprep(code,'\n%%','\nxxx-cellbreak-xxx%%');
 cellList = regexp(code2,'xxx-cellbreak-xxx','split');
 % Test each cell
 % Each testpoint structure
 % testPoint = struct(...
 % 'pass', false, ...
 % 'code', '', ...
 % 'output', '');
 testSuite = struct([]);
 [containsIllegalFcnFlag, illegalFcnMessage] = containsIllegalFcn(sourceFile);
 for countVariable = 1:length(cellList)
 cellCode = cellList{countVariable};
 cleanCellCode = cleanCode(cellCode);
 % Test is guilty until proven successful
 pass = false;
 % Run it
 try
 output = evaluateCode(cleanCellCode);
 pass = true;
 catch me
 output = ['Error: ' me.message];
 end
 if containsIllegalFcnFlag
 pass = false;
 output = illegalFcnMessage;
 end
 cellOutput = cleanCode(output);
 testSuite(countVariable).code = cleanCellCode;
 testSuite(countVariable).output = cellOutput;
 testSuite(countVariable).pass = pass;
 end
 % Set up data structure to return
 testSuiteResults = struct(...
 'pass', false, ...
 'score', 0, ...
 'functions', [], ...
 'testPoints', struct([]));
 % Populate the result struct
 % If any test point is failed, sets the overall pass status to false.
 testSuiteResults.pass = all([testSuite.pass]);
 % sets the score
 testSuiteResults.score = sprintf('%d',score);
 % Set test points
 testSuiteResults.testPoints = testSuite;
 % Set functions points
 testSuiteResults.functions = findFcns(sourceFile,'file');
 end</pre>Previous problem in this series: <a href = "http://www.mathworks.com/matlabcentral/cody/problems/1769-singularity-2-0-easier">Singularity 2.0 (easier)</a>Next problem in this series: <a href = "http://www.mathworks.com/matlabcentral/cody/problems/1764-singularity-2-0">Singularity 2.0 (really hard)</a>

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Last Solution submitted on Sep 25, 2020

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Jean-Marie Sainthillier on 3 Aug 2013

Where do you find all these informations ?

Alfonso Nieto-Castanon on 3 Aug 2013

dbstack('-completenames') will tell you the function call stack, then you can just read the appropriate files to see what is in them...

Jean-Marie Sainthillier on 3 Aug 2013

You should write a book with all your Matlab experience (seriously).

Jean-Marie Sainthillier on 3 Aug 2013

Do you suggest it is possible to modify directly the testsuite in the function ?

Alfonso Nieto-Castanon on 3 Aug 2013

well, not exactly. When myfunction() is being evaluated it is being called by the testsuite code (and that happens inside a evalc command inside the evaluateCode() subfunction) so it is already too late to change the testsuite itself. You can do two things: a) either assume the the call to 'evaluateCode()' is going to fail, and see if you can do something about it (this is the simpler way to solve this problem); or b) try to modify the testsuite *before* myfunction() is being evaluated (that is the solution needed for the next problem -'singularity 2.0 (really hard)'- in this series

Alfonso Nieto-Castanon on 3 Aug 2013

ps. and thanks for the compliment :)

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Solution 296002

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Jean-Marie Sainthillier on 4 Aug 2013

Correct solution with a fail !
:)

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Problem 1770. singularity 2.0 (hard)

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