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JS: recognize sanitizing slashes in URL redirection queries
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@@ -16,46 +16,8 @@ module ServerSideUrlRedirect {
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/**
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* A data flow sink for unvalidated URL redirect vulnerabilities.
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*/
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abstract class Sink extends DataFlow::Node {
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/**
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* Holds if this sink may redirect to a non-local URL.
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*/
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predicate maybeNonLocal() {
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exists (DataFlow::Node prefix | prefix = getAPrefix(this) |
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not exists(prefix.asExpr().getStringValue())
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or
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exists (string prefixVal | prefixVal = prefix.asExpr().getStringValue() |
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// local URLs (i.e., URLs that start with `/` not followed by `\` or `/`,
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// or that start with `~/`) are unproblematic
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not prefixVal.regexpMatch("/[^\\\\/].*|~/.*") and
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// so are localhost URLs
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not prefixVal.regexpMatch("(\\w+:)?//localhost[:/].*")
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)
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)
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}
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}
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abstract class Sink extends DataFlow::Node { }
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/**
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* Gets a node that is transitively reachable from `nd` along prefix predecessor edges.
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*/
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private DataFlow::Node prefixCandidate(Sink sink) {
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result = sink or
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result = prefixCandidate(sink).getAPredecessor() or
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result = StringConcatenation::getFirstOperand(prefixCandidate(sink))
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}
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/**
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* Gets an expression that may end up being a prefix of the string concatenation `nd`.
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*/
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private DataFlow::Node getAPrefix(Sink sink) {
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exists (DataFlow::Node prefix |
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prefix = prefixCandidate(sink) and
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not exists(StringConcatenation::getFirstOperand(prefix)) and
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not exists(prefix.getAPredecessor()) and
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result = prefix
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)
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}
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/**
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* A sanitizer for unvalidated URL redirect vulnerabilities.
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*/
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@@ -72,7 +34,7 @@ module ServerSideUrlRedirect {
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}
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override predicate isSink(DataFlow::Node sink) {
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sink.(Sink).maybeNonLocal()
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sink instanceof Sink
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}
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override predicate isSanitizer(DataFlow::Node node) {
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@@ -7,11 +7,19 @@
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import javascript
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/**
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* Holds if a string value containing `?` or `#` may flow into
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* `nd` or one of its operands, assuming that it is a concatenation.
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* Holds if the string value of `nd` prevents anything appended after it
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* from affecting the hostname of a URL.
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*
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* Specifically, this holds if the string contains any of the following:
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* - `?` (any suffix becomes part of query)
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* - `#` (any suffix becomes part of fragment)
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* - `/` or `\`, immediately prefixed by a character other than `:`, `/`, or `\` (any suffix becomes part of the path)
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*
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* In the latter case, the additional prefix check is necessary to avoid a `/` that could be interpreted as
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* the `//` separating the (optional) scheme from the hostname.
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*/
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private predicate hasSanitizingSubstring(DataFlow::Node nd) {
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nd.asExpr().getStringValue().regexpMatch(".*[?#].*")
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predicate hasSanitizingSubstring(DataFlow::Node nd) {
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nd.asExpr().getStringValue().regexpMatch(".*([?#]|[^?#:/\\\\][/\\\\]).*")
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or
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hasSanitizingSubstring(StringConcatenation::getAnOperand(nd))
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or
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@@ -21,8 +29,8 @@ private predicate hasSanitizingSubstring(DataFlow::Node nd) {
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}
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/**
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* Holds if data that flows from `source` to `sink` may have a string
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* containing the character `?` or `#` prepended to it.
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* Holds if data that flows from `source` to `sink` cannot affect the
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* hostname of the resulting string when interpreted as a URL.
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*
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* This is considered as a sanitizing edge for the URL redirection queries.
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*/
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@@ -7,14 +7,6 @@ nodes
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| express.js:35:16:35:21 | target |
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| express.js:40:16:40:108 | (req.pa ... ntacts" |
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| express.js:40:69:40:87 | req.param('action') |
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| express.js:44:7:44:28 | handle |
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| express.js:44:16:44:28 | req.params[0] |
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| express.js:45:7:45:33 | url |
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| express.js:45:13:45:27 | "/Me/" + handle |
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| express.js:45:13:45:33 | "/Me/" ... e + "/" |
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| express.js:45:22:45:27 | handle |
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| express.js:49:3:49:3 | url |
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| express.js:49:26:49:28 | url |
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| express.js:74:16:74:43 | `${req. ... )}/foo` |
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| express.js:74:19:74:37 | req.param("target") |
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| express.js:83:7:83:34 | target |
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@@ -24,6 +16,18 @@ nodes
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| express.js:118:16:118:63 | [req.qu ... ection] |
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| express.js:118:16:118:72 | [req.qu ... oin('') |
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| express.js:118:17:118:30 | req.query.page |
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| express.js:134:16:134:36 | '/' + r ... ms.user |
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| express.js:134:22:134:36 | req.params.user |
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| express.js:135:16:135:37 | '//' + ... ms.user |
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| express.js:135:23:135:37 | req.params.user |
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| express.js:136:16:136:36 | 'u' + r ... ms.user |
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| express.js:136:22:136:36 | req.params.user |
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| express.js:138:16:138:45 | '/' + ( ... s.user) |
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| express.js:138:22:138:45 | ('/u' + ... s.user) |
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| express.js:138:23:138:44 | '/u' + ... ms.user |
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| express.js:138:30:138:44 | req.params.user |
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| express.js:139:16:139:37 | '/u' + ... ms.user |
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| express.js:139:23:139:37 | req.params.user |
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| node.js:6:7:6:52 | target |
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| node.js:6:16:6:39 | url.par ... , true) |
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| node.js:6:16:6:45 | url.par ... ).query |
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@@ -54,19 +58,19 @@ edges
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| express.js:27:7:27:34 | target | express.js:35:16:35:21 | target |
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| express.js:27:16:27:34 | req.param("target") | express.js:27:7:27:34 | target |
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| express.js:40:69:40:87 | req.param('action') | express.js:40:16:40:108 | (req.pa ... ntacts" |
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| express.js:44:7:44:28 | handle | express.js:45:22:45:27 | handle |
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| express.js:44:16:44:28 | req.params[0] | express.js:44:7:44:28 | handle |
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| express.js:45:7:45:33 | url | express.js:49:3:49:3 | url |
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| express.js:45:13:45:27 | "/Me/" + handle | express.js:45:13:45:33 | "/Me/" ... e + "/" |
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| express.js:45:13:45:33 | "/Me/" ... e + "/" | express.js:45:7:45:33 | url |
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| express.js:45:22:45:27 | handle | express.js:45:13:45:27 | "/Me/" + handle |
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| express.js:49:3:49:3 | url | express.js:49:26:49:28 | url |
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| express.js:74:19:74:37 | req.param("target") | express.js:74:16:74:43 | `${req. ... )}/foo` |
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| express.js:83:7:83:34 | target | express.js:90:18:90:23 | target |
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| express.js:83:7:83:34 | target | express.js:97:16:97:21 | target |
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| express.js:83:16:83:34 | req.param("target") | express.js:83:7:83:34 | target |
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| express.js:118:16:118:63 | [req.qu ... ection] | express.js:118:16:118:72 | [req.qu ... oin('') |
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| express.js:118:17:118:30 | req.query.page | express.js:118:16:118:63 | [req.qu ... ection] |
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| express.js:134:22:134:36 | req.params.user | express.js:134:16:134:36 | '/' + r ... ms.user |
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| express.js:135:23:135:37 | req.params.user | express.js:135:16:135:37 | '//' + ... ms.user |
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| express.js:136:22:136:36 | req.params.user | express.js:136:16:136:36 | 'u' + r ... ms.user |
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| express.js:138:22:138:45 | ('/u' + ... s.user) | express.js:138:16:138:45 | '/' + ( ... s.user) |
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| express.js:138:23:138:44 | '/u' + ... ms.user | express.js:138:22:138:45 | ('/u' + ... s.user) |
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| express.js:138:30:138:44 | req.params.user | express.js:138:23:138:44 | '/u' + ... ms.user |
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| express.js:139:23:139:37 | req.params.user | express.js:139:16:139:37 | '/u' + ... ms.user |
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| node.js:6:7:6:52 | target | node.js:7:34:7:39 | target |
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| node.js:6:16:6:39 | url.par ... , true) | node.js:6:16:6:45 | url.par ... ).query |
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| node.js:6:16:6:45 | url.par ... ).query | node.js:6:16:6:52 | url.par ... .target |
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@@ -94,11 +98,15 @@ edges
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| express.js:33:18:33:23 | target | express.js:27:16:27:34 | req.param("target") | express.js:33:18:33:23 | target | Untrusted URL redirection due to $@. | express.js:27:16:27:34 | req.param("target") | user-provided value |
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| express.js:35:16:35:21 | target | express.js:27:16:27:34 | req.param("target") | express.js:35:16:35:21 | target | Untrusted URL redirection due to $@. | express.js:27:16:27:34 | req.param("target") | user-provided value |
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| express.js:40:16:40:108 | (req.pa ... ntacts" | express.js:40:69:40:87 | req.param('action') | express.js:40:16:40:108 | (req.pa ... ntacts" | Untrusted URL redirection due to $@. | express.js:40:69:40:87 | req.param('action') | user-provided value |
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| express.js:49:26:49:28 | url | express.js:44:16:44:28 | req.params[0] | express.js:49:26:49:28 | url | Untrusted URL redirection due to $@. | express.js:44:16:44:28 | req.params[0] | user-provided value |
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| express.js:74:16:74:43 | `${req. ... )}/foo` | express.js:74:19:74:37 | req.param("target") | express.js:74:16:74:43 | `${req. ... )}/foo` | Untrusted URL redirection due to $@. | express.js:74:19:74:37 | req.param("target") | user-provided value |
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| express.js:90:18:90:23 | target | express.js:83:16:83:34 | req.param("target") | express.js:90:18:90:23 | target | Untrusted URL redirection due to $@. | express.js:83:16:83:34 | req.param("target") | user-provided value |
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| express.js:97:16:97:21 | target | express.js:83:16:83:34 | req.param("target") | express.js:97:16:97:21 | target | Untrusted URL redirection due to $@. | express.js:83:16:83:34 | req.param("target") | user-provided value |
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| express.js:118:16:118:72 | [req.qu ... oin('') | express.js:118:17:118:30 | req.query.page | express.js:118:16:118:72 | [req.qu ... oin('') | Untrusted URL redirection due to $@. | express.js:118:17:118:30 | req.query.page | user-provided value |
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| express.js:134:16:134:36 | '/' + r ... ms.user | express.js:134:22:134:36 | req.params.user | express.js:134:16:134:36 | '/' + r ... ms.user | Untrusted URL redirection due to $@. | express.js:134:22:134:36 | req.params.user | user-provided value |
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| express.js:135:16:135:37 | '//' + ... ms.user | express.js:135:23:135:37 | req.params.user | express.js:135:16:135:37 | '//' + ... ms.user | Untrusted URL redirection due to $@. | express.js:135:23:135:37 | req.params.user | user-provided value |
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| express.js:136:16:136:36 | 'u' + r ... ms.user | express.js:136:22:136:36 | req.params.user | express.js:136:16:136:36 | 'u' + r ... ms.user | Untrusted URL redirection due to $@. | express.js:136:22:136:36 | req.params.user | user-provided value |
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| express.js:138:16:138:45 | '/' + ( ... s.user) | express.js:138:30:138:44 | req.params.user | express.js:138:16:138:45 | '/' + ( ... s.user) | Untrusted URL redirection due to $@. | express.js:138:30:138:44 | req.params.user | user-provided value |
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| express.js:139:16:139:37 | '/u' + ... ms.user | express.js:139:23:139:37 | req.params.user | express.js:139:16:139:37 | '/u' + ... ms.user | Untrusted URL redirection due to $@. | express.js:139:23:139:37 | req.params.user | user-provided value |
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| node.js:7:34:7:39 | target | node.js:6:26:6:32 | req.url | node.js:7:34:7:39 | target | Untrusted URL redirection due to $@. | node.js:6:26:6:32 | req.url | user-provided value |
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| node.js:15:34:15:45 | '/' + target | node.js:11:26:11:32 | req.url | node.js:15:34:15:45 | '/' + target | Untrusted URL redirection due to $@. | node.js:11:26:11:32 | req.url | user-provided value |
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| node.js:32:34:32:55 | target ... =" + me | node.js:29:26:29:32 | req.url | node.js:32:34:32:55 | target ... =" + me | Untrusted URL redirection due to $@. | node.js:29:26:29:32 | req.url | user-provided value |
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@@ -126,3 +126,15 @@ function sendUserToUrl(res, nextUrl) {
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app.get('/call', function(req, res) {
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sendUserToUrl(res, req.query.nextUrl);
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});
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app.get('/redirect/:user', function(req, res) {
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res.redirect('/users/' + req.params.user); // GOOD
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res.redirect('users/' + req.params.user); // GOOD
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res.redirect('/' + req.params.user); // BAD - could go to //evil.com
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res.redirect('//' + req.params.user); // BAD - could go to //evil.com
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res.redirect('u' + req.params.user); // BAD - could go to u.evil.com
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res.redirect('/' + ('/u' + req.params.user)); // BAD - could go to //u.evil.com
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res.redirect('/u' + req.params.user); // GOOD - but flagged anyway
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});
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