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Python: Exclude AF_UNIX sockets from BindToAllInterfaces

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Looking at the results of the the previous DCA run, there was a bunch of
false positives where `bind` was being used with a `AF_UNIX` socket (a
filesystem path encoded as a string), not a `(host, port)` tuple. These
results should be excluded from the query, as they are not vulnerable.

Ideally, we would just add `.TupleElement[0]` to the MaD sink, except we
don't actually support this in Python MaD...

So, instead I opted for a more low-tech solution: check that the
argument in question flows from a tuple in the local scope.

This eliminates a bunch of false positives on `python/cpython` leaving
behind four true positive results.
This commit is contained in:
Taus
2026-03-27 14:11:14 +00:00
parent c9832c330a
commit 4f74d421b9
3 changed files with 18 additions and 1 deletions
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14
python/ql/src/Security/CVE-2018-1281/BindToAllInterfaces.ql
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@@ -42,8 +42,20 @@ private module BindToAllInterfacesFlow = TaintTracking::Global<BindToAllInterfac
private import BindToAllInterfacesFlow
/**
* Holds if `sink` is the address argument of a `bind()` call on a
* network socket (AF_INET or AF_INET6), as opposed to a Unix domain
* socket (AF_UNIX) which takes a plain string path.
*
* Network socket addresses are tuples like `(host, port)`, so we check
* that the sink argument is a tuple, by looking for flow from a tuple expression.
*/
private predicate isNetworkBind(DataFlow::Node sink) {
any(DataFlow::LocalSourceNode n | n.asExpr() instanceof Tuple).flowsTo(sink)
}
from PathNode source, PathNode sink
where flowPath(source, sink)
where flowPath(source, sink) and isNetworkBind(sink.getNode())
select sink.getNode(), source, sink,
"Binding a socket to all interfaces (using $@) is a security risk.", source.getNode(),
"'" + source.getNode().asExpr().(StringLiteral).getText() + "'"

1
python/ql/test/query-tests/Security/CVE-2018-1281/BindToAllInterfaces.expected
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@@ -60,4 +60,5 @@ nodes
| BindToAllInterfaces_test.py:53:10:53:25 | ControlFlowNode for Tuple | semmle.label | ControlFlowNode for Tuple |
| BindToAllInterfaces_test.py:58:10:58:18 | ControlFlowNode for StringLiteral | semmle.label | ControlFlowNode for StringLiteral |
| BindToAllInterfaces_test.py:58:10:58:25 | ControlFlowNode for Tuple | semmle.label | ControlFlowNode for Tuple |
| BindToAllInterfaces_test.py:62:9:62:10 | ControlFlowNode for StringLiteral | semmle.label | ControlFlowNode for StringLiteral |
subpaths

4
python/ql/test/query-tests/Security/CVE-2018-1281/BindToAllInterfaces_test.py
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@@ -56,3 +56,7 @@ gs.bind(('0.0.0.0', 31137)) # $ Alert[py/bind-socket-all-network-interfaces]
from eventlet.green import socket as esocket
es = esocket.socket(esocket.AF_INET, esocket.SOCK_STREAM)
es.bind(('0.0.0.0', 31137)) # $ Alert[py/bind-socket-all-network-interfaces]
# AF_UNIX socket binding should not be flagged
us = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
us.bind('')