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Fix #11: Support double quotes in strings #12

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merged 5 commits into from
Aug 26, 2019
Merged

Fix #11: Support double quotes in strings #12

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9b83b49
Fix #11: Support double quotes in strings
arendjr Aug 6, 2019
dd9510f
support more variable names
albehrens Aug 7, 2019
d7eb14a
Revert "support more variable names"
albehrens Aug 9, 2019
ae835e3
Tighten string regex
arendjr Aug 12, 2019
82d3eda
at this point i'm just being paranoid
cshaa Aug 26, 2019
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7 changes: 1 addition & 6 deletions src/filtrex.js
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Original file line number Diff line number Diff line change
Expand Up @@ -140,12 +140,7 @@ function filtrexParser() {
return "SYMBOL";`
], // 'some-symbol'

['"(?:[^"])*"',
`yytext = JSON.stringify(
yytext.substr(1, yyleng-2)
);
return "STRING";`
], // "foo"
['"(?:\\\\"|[^"])*"', 'return "STRING";'], // "foo"
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@cshaa cshaa Aug 8, 2019 •
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Your regex also matches "a\" as a legit string. The not-char pattern should be something like [^"\\] instead of [^"]. This can be used as an exploit, because the next string would be actually executed as JavaScript:

"a\" == "; window.p0wned = true; //"

Also, can you guarantee that removing the JSON.stringify won't result in any malicious code? We know that everything that comes out of stringify is safe. But how can we be sure every match of your regex is safe? (After fixing the previous bug, of course, now it obviously isn't safe.)


// End
['$', 'return "EOF";'],
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11 changes: 8 additions & 3 deletions test/security.js
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Expand Up @@ -57,9 +57,10 @@ describe('Security', () => {
});


it('does backslash escaping', () =>
expect( compileExpression(`"\\" + '\\'`)({'\\':'good'}) ).equals('\\good')
);
it('does backslash escaping', () => {
expect( compileExpression(`"\\\\" + '\\'`)({'\\':'good'}) ).equals('\\good');
expect( compileExpression(`"\\\\" + '\\\\'`)({'\\\\':'good'}) ).equals('\\good');
});


it('in() is not vulnerable to Object.prototype extensions ', () => {
Expand All @@ -76,4 +77,8 @@ describe('Security', () => {
).equals(undefined);
})


it('supports double quotes inside strings', () => {
expect( compileExpression('"\\"test\\""')({}) ).equals('"test"');
});
});