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 takes care of most of the false negatives from the preceding
commit.
Additionally, we add models for some known wrappers of `socket.socket`
from the `gevent` and `eventlet` packages.
Adds test cases from github/codeql#21582 demonstrating false negatives:
- Address stored in class attribute (`self.bind_addr`)
- `os.environ.get` with insecure default value
- `gevent.socket` (alternative socket module)
The fix may look a bit obscure, so here's what's going on.
When we see `from . import helper`, we create an `ImportExpr` with level
equal to 1 (corresponding to the number of dots). To resolve such
imports, we compute the name of the enclosing package, as part of
`ImportExpr.qualifiedTopName()`. For this form of import expression, it
is equivalent to `this.getEnclosingModule().getPackageName()`. But
`qualifiedTopName` requires that `valid_module_name` holds for its
result, and this was _not_ the case for namespace packages.
To fix this, we extend `valid_module_name` to include the module names
of _any_ folder, not just regular package (which are the ones where
there's a `__init__.py` in the folder). Note that this doesn't simply
include all folders -- only the ones that result in valid module names
in Python.
Adds `hasOverloadDecorator` as a predicate on functions. It looks for
decorators called `overload` or `something.overload` (usually
`typing.overload` or `t.overload`). These are then filtered out in the
predicates that (approximate) resolving methods according to the MRO.
As the test introduced in the previous commit shows, this removes the
spurious resolutions we had before.
The ones that no longer require points-to no longer import
`LegacyPointsTo`. The ones that do use the specific
`...MetricsWithPointsTo` classes that are applicable.
