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Python: Support EC keygen without class-instance for cryptography

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I also added a new test to show off how what the origin ends up looking
like... I think it looks ok
This commit is contained in:
Rasmus Wriedt Larsen
2021-05-05 12:29:55 +02:00
parent 3ceb8bbcc6
commit 668bfd3a41
5 changed files with 56 additions and 5 deletions
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26
python/ql/src/semmle/python/frameworks/Cryptography.qll
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@@ -22,7 +22,7 @@ private module CryptographyModel {
* Gets a predefined curve class from
* `cryptography.hazmat.primitives.asymmetric.ec` with a specific key size (in bits).
*/
private DataFlow::Node curveClassWithKeySize(int keySize) {
private API::Node predefinedCurveClass(int keySize) {
exists(string curveName |
result =
API::moduleImport("cryptography")
@@ -31,7 +31,6 @@ private module CryptographyModel {
.getMember("asymmetric")
.getMember("ec")
.getMember(curveName)
.getAUse()
|
// obtained by manually looking at source code in
// https://github.com/pyca/cryptography/blob/cba69f1922803f4f29a3fde01741890d88b8e217/src/cryptography/hazmat/primitives/asymmetric/ec.py#L208-L300
@@ -75,13 +74,30 @@ private module CryptographyModel {
)
}
/** Gets a reference to a predefined curve class with a specific key size (in bits), as well as the origin of the class. */
private DataFlow::LocalSourceNode curveClassWithKeySize(
DataFlow::TypeTracker t, int keySize, DataFlow::Node origin
) {
t.start() and
result = predefinedCurveClass(keySize).getAnImmediateUse() and
origin = result
or
exists(DataFlow::TypeTracker t2 |
result = curveClassWithKeySize(t2, keySize, origin).track(t2, t)
)
}
/** Gets a reference to a predefined curve class with a specific key size (in bits), as well as the origin of the class. */
DataFlow::Node curveClassWithKeySize(int keySize, DataFlow::Node origin) {
curveClassWithKeySize(DataFlow::TypeTracker::end(), keySize, origin).flowsTo(result)
}
/** Gets a reference to a predefined curve class instance with a specific key size (in bits), as well as the origin of the class. */
private DataFlow::LocalSourceNode curveClassInstanceWithKeySize(
DataFlow::TypeTracker t, int keySize, DataFlow::Node origin
) {
t.start() and
result.(DataFlow::CallCfgNode).getFunction() = curveClassWithKeySize(keySize) and
origin = result
result.(DataFlow::CallCfgNode).getFunction() = curveClassWithKeySize(keySize, origin)
or
exists(DataFlow::TypeTracker t2 |
result = curveClassInstanceWithKeySize(t2, keySize, origin).track(t2, t)
@@ -164,6 +180,8 @@ private module CryptographyModel {
override int getKeySizeWithOrigin(DataFlow::Node origin) {
this.getCurveArg() = Ecc::curveClassInstanceWithKeySize(result, origin)
or
this.getCurveArg() = Ecc::curveClassWithKeySize(result, origin)
}
// Note: There is not really a key-size argument, since it's always specified by the curve.