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JavaScript: Reduce FPs in incomplete-sanitization for bracket pair removal #17

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JavaScript: Reduce FPs in incomplete-sanitization for bracket pair removal #17

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16 changes: 14 additions & 2 deletions javascript/ql/src/Security/CWE-116/IncompleteSanitization.ql
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Original file line number Diff line number Diff line change
Expand Up @@ -100,6 +100,18 @@ predicate removesFirstOccurrence(StringReplaceCall repl, string str) {
not exists(repl.getRegExp()) and repl.replaces(str, "")
}

/**
* Holds if `repl` removes a single character `str` (either via a string argument or a regex).
*/
predicate removesCharacter(StringReplaceCall repl, string str) {
removesFirstOccurrence(repl, str)
or
exists(DataFlow::Node re | re = repl.getRegExp() |
getAMatchedString(re) = str and
repl.replaces(str, "")
)
}

/**
* Holds if `leftUnwrap` and `rightUnwrap` unwraps a string from a pair of surrounding delimiters.
*/
Expand All @@ -117,8 +129,8 @@ predicate isDelimiterUnwrapper(
or
left = "'" and right = "'"
|
removesFirstOccurrence(leftUnwrap, left) and
removesFirstOccurrence(rightUnwrap, right) and
removesCharacter(leftUnwrap, left) and
removesCharacter(rightUnwrap, right) and
leftUnwrap.getAMethodCall() = rightUnwrap
)
}
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9 changes: 8 additions & 1 deletion javascript/ql/test/query-tests/Security/CWE-116/IncompleteSanitization/tst.js
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Expand Up @@ -137,10 +137,17 @@ function goodOrBad12(s) {

s = s.replace('[', '');
s = s.replace(']', '');
s.replace(/{/, '').replace(/}/, ''); // $ Alert[js/incomplete-sanitization] - should have used a string literal if a single replacement was intended
s.replace(/{/, '').replace(/}/, ''); // bracket pair removal via regex - no alert expected
s.replace(']', '').replace('[', ''); // $ Alert[js/incomplete-sanitization] - probably OK, but still flagged
}

function goodBracketPairRegex(s) {
// Bracket pair removal via regex should not be flagged
s.replace(/\[/, '').replace(/\]/, '');
s.replace(/\{/, '').replace(/\}/, '');
s.replace(/\(/, '').replace(/\)/, '');
}

function newlines(s) {
// motivation for whitelist
require("child_process").execSync("which emacs").toString().replace("\n", "");
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