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JavaScript: Teach IncompleteSanitization to recognize incomplete URI {en,de}coding. #43

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Merged
semmle-qlci merged 1 commit into from
Aug 10, 2018
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JavaScript: Teach IncompleteSanitization to recognize incomplete URI {en,de}coding. #43

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1 change: 1 addition & 0 deletions change-notes/1.18/analysis-javascript.md
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Original file line number Diff line number Diff line change
Expand Up @@ -39,6 +39,7 @@
| Arguments redefined | Fewer results | This rule previously also flagged redefinitions of `eval`. This was an oversight that is now fixed. |
| CORS misconfiguration for credentials transfer | More true-positive results | This rule now treats header names case-insensitively. |
| Hard-coded credentials | More true-positive results | This rule now recognizes secret cryptographic keys. |
| Incomplete sanitization | More true-positive results | This rule now recognizes incomplete URL encoding and decoding. |
| Insecure randomness | More true-positive results | This rule now recognizes secret cryptographic keys. |
| Missing rate limiting | More true-positive results, fewer false-positive results | This rule now recognizes additional rate limiters and expensive route handlers. |
| Missing X-Frame-Options HTTP header | Fewer false-positive results | This rule now treats header names case-insensitively. |
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15 changes: 13 additions & 2 deletions javascript/ql/src/Security/CWE-116/IncompleteSanitization.ql
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Expand Up @@ -106,8 +106,19 @@ where repl.getMethodName() = "replace" and
(
not old.(RegExpLiteral).isGlobal() and
msg = "This replaces only the first occurrence of " + old + "." and
// only flag if this is likely to be a sanitizer
getAMatchedString(old) = metachar() and
// only flag if this is likely to be a sanitizer or URL encoder or decoder
exists (string m | m = getAMatchedString(old) |
// sanitizer
m = metachar()
or
exists (string urlEscapePattern | urlEscapePattern = "(%[0-9A-Fa-f]{2})+" |
// URL decoder
m.regexpMatch(urlEscapePattern)
or
// URL encoder
repl.getArgument(1).getStringValue().regexpMatch(urlEscapePattern)
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@asger-semmle asger-semmle Aug 10, 2018

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Not a real problem in this case, but it does bother me a bit that m isn't bound in the last case. It's not that obvious that there is no cartesian product here.

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@xiemaisi xiemaisi Aug 10, 2018

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I can pull it out of the exists if you like and add and exists(getAMatchedString(old)) instead (that bit is important to avoid false positives from cases where we cannot analyse old).

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@asger-semmle asger-semmle Aug 10, 2018

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Ah right, if the exists matters then let's keep it like this.

)
) and
// don't flag replace operations in a loop
not DataFlow::valueNode(repl.getReceiver()) = DataFlow::valueNode(repl).getASuccessor+()
or
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2 changes: 2 additions & 0 deletions javascript/ql/test/query-tests/Security/CWE-116/IncompleteSanitization.expected
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Expand Up @@ -7,3 +7,5 @@
| tst.js:29:20:29:27 | /('\|")/g | This does not backslash-escape the backslash character. |
| tst.js:33:20:33:22 | '\|' | This replaces only the first occurrence of '\|'. |
| tst.js:37:20:37:23 | /"/g | This does not backslash-escape the backslash character. |
| tst.js:41:20:41:22 | "/" | This replaces only the first occurrence of "/". |
| tst.js:45:20:45:24 | "%25" | This replaces only the first occurrence of "%25". |
15 changes: 15 additions & 0 deletions javascript/ql/test/query-tests/Security/CWE-116/tst.js
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Original file line number Diff line number Diff line change
Expand Up @@ -37,6 +37,14 @@ function bad9(s) {
return s.replace(/"/g, "\\\""); // NOT OK
}

function bad10(s) {
return s.replace("/", "%2F"); // NOT OK
}

function bad11(s) {
return s.replace("%25", "%"); // NOT OK
}


function good1(s) {
while (s.indexOf("'") > 0)
Expand Down Expand Up @@ -91,6 +99,10 @@ function flowifyComments(s) {
return s.replace(/#/g, '💩'); // OK
}

function good11(s) {
return s.replace("%d", "42");
}

app.get('/some/path', function(req, res) {
let untrusted = req.param("p");

Expand All @@ -106,6 +118,8 @@ app.get('/some/path', function(req, res) {
bad7(untrusted);
bad8(untrusted);
bad9(untrusted);
bad10(untrusted);
bad11(untrusted);

good1(untrusted);
good2(untrusted);
Expand All @@ -118,4 +132,5 @@ app.get('/some/path', function(req, res) {
good9(untrusted);
good10(untrusted);
flowifyComments(untrusted);
good11(untrusted);
});