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Merge pull request #5395 from tausbn/python-share-typetracker
Python: Make the type tracking implementation shareable
This commit is contained in:
Arthur Baars
420
python/ql/src/experimental/typetracking/TypeTracker.qll
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420
python/ql/src/experimental/typetracking/TypeTracker.qll
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@@ -0,0 +1,420 @@
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/** Step Summaries and Type Tracking */
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private import TypeTrackerSpecific
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/**
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* Any string that may appear as the name of a piece of content. This will usually include things like:
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* - Attribute names (in Python)
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* - Property names (in JavaScript)
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*
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* In general, this can also be used to model things like stores to specific list indices. To ensure
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* correctness, it is important that
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*
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* - different types of content do not have overlapping names, and
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* - the empty string `""` is not a valid piece of content, as it is used to indicate the absence of
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* content instead.
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*/
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class ContentName extends string {
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ContentName() { this = getPossibleContentName() }
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}
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/** Either a content name, or the empty string (representing no content). */
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class OptionalContentName extends string {
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OptionalContentName() { this instanceof ContentName or this = "" }
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}
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/**
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* A description of a step on an inter-procedural data flow path.
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*/
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private newtype TStepSummary =
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LevelStep() or
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CallStep() or
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ReturnStep() or
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StoreStep(ContentName content) or
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LoadStep(ContentName content)
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/**
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* INTERNAL: Use `TypeTracker` or `TypeBackTracker` instead.
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*
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* A description of a step on an inter-procedural data flow path.
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*/
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class StepSummary extends TStepSummary {
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/** Gets a textual representation of this step summary. */
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string toString() {
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this instanceof LevelStep and result = "level"
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or
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this instanceof CallStep and result = "call"
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or
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this instanceof ReturnStep and result = "return"
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or
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exists(string content | this = StoreStep(content) | result = "store " + content)
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or
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exists(string content | this = LoadStep(content) | result = "load " + content)
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}
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}
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/** Provides predicates for updating step summaries (`StepSummary`s). */
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module StepSummary {
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/**
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* Gets the summary that corresponds to having taken a forwards
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* heap and/or inter-procedural step from `nodeFrom` to `nodeTo`.
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*/
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cached
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predicate step(LocalSourceNode nodeFrom, LocalSourceNode nodeTo, StepSummary summary) {
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exists(Node mid | nodeFrom.flowsTo(mid) and smallstep(mid, nodeTo, summary))
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}
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/**
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* Gets the summary that corresponds to having taken a forwards
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* local, heap and/or inter-procedural step from `nodeFrom` to `nodeTo`.
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*
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* Unlike `StepSummary::step`, this predicate does not compress
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* type-preserving steps.
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*/
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predicate smallstep(Node nodeFrom, LocalSourceNode nodeTo, StepSummary summary) {
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jumpStep(nodeFrom, nodeTo) and
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summary = LevelStep()
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or
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callStep(nodeFrom, nodeTo) and summary = CallStep()
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or
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returnStep(nodeFrom, nodeTo) and
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summary = ReturnStep()
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or
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exists(string content |
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localSourceStoreStep(nodeFrom, nodeTo, content) and
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summary = StoreStep(content)
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or
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basicLoadStep(nodeFrom, nodeTo, content) and summary = LoadStep(content)
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)
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}
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/**
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* Holds if `nodeFrom` is being written to the `content` content of the object in `nodeTo`.
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*
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* Note that `nodeTo` will always be a local source node that flows to the place where the content
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* is written in `basicStoreStep`. This may lead to the flow of information going "back in time"
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* from the point of view of the execution of the program.
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*
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* For instance, if we interpret attribute writes in Python as writing to content with the same
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* name as the attribute and consider the following snippet
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*
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* ```python
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* def foo(y):
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* x = Foo()
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* bar(x)
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* x.attr = y
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* baz(x)
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*
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* def bar(x):
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* z = x.attr
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* ```
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* for the attribute write `x.attr = y`, we will have `content` being the literal string `"attr"`,
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* `nodeFrom` will be `y`, and `nodeTo` will be the object `Foo()` created on the first line of the
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* function. This means we will track the fact that `x.attr` can have the type of `y` into the
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* assignment to `z` inside `bar`, even though this attribute write happens _after_ `bar` is called.
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*/
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predicate localSourceStoreStep(Node nodeFrom, LocalSourceNode nodeTo, string content) {
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exists(Node obj | nodeTo.flowsTo(obj) and basicStoreStep(nodeFrom, obj, content))
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}
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}
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private newtype TTypeTracker = MkTypeTracker(Boolean hasCall, OptionalContentName content)
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/**
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* Summary of the steps needed to track a value to a given dataflow node.
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*
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* This can be used to track objects that implement a certain API in order to
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* recognize calls to that API. Note that type-tracking does not by itself provide a
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* source/sink relation, that is, it may determine that a node has a given type,
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* but it won't determine where that type came from.
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*
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* It is recommended that all uses of this type are written in the following form,
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* for tracking some type `myType`:
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* ```ql
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* DataFlow::LocalSourceNode myType(DataFlow::TypeTracker t) {
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* t.start() and
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* result = < source of myType >
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* or
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* exists (DataFlow::TypeTracker t2 |
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* result = myType(t2).track(t2, t)
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* )
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* }
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*
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* DataFlow::Node myType() { myType(DataFlow::TypeTracker::end()).flowsTo(result) }
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* ```
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*
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* Instead of `result = myType(t2).track(t2, t)`, you can also use the equivalent
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* `t = t2.step(myType(t2), result)`. If you additionally want to track individual
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* intra-procedural steps, use `t = t2.smallstep(myCallback(t2), result)`.
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*/
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class TypeTracker extends TTypeTracker {
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Boolean hasCall;
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OptionalContentName content;
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TypeTracker() { this = MkTypeTracker(hasCall, content) }
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/** Gets the summary resulting from appending `step` to this type-tracking summary. */
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cached
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TypeTracker append(StepSummary step) {
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step = LevelStep() and result = this
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or
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step = CallStep() and result = MkTypeTracker(true, content)
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or
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step = ReturnStep() and hasCall = false and result = this
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or
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step = LoadStep(content) and result = MkTypeTracker(hasCall, "")
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or
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exists(string p | step = StoreStep(p) and content = "" and result = MkTypeTracker(hasCall, p))
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}
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/** Gets a textual representation of this summary. */
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string toString() {
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exists(string withCall, string withContent |
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(if hasCall = true then withCall = "with" else withCall = "without") and
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(if content != "" then withContent = " with content " + content else withContent = "") and
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result = "type tracker " + withCall + " call steps" + withContent
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)
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}
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/**
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* Holds if this is the starting point of type tracking.
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*/
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predicate start() { hasCall = false and content = "" }
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/**
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* Holds if this is the starting point of type tracking, and the value starts in the content named `contentName`.
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* The type tracking only ends after the content has been loaded.
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*/
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predicate startInContent(ContentName contentName) { hasCall = false and content = contentName }
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/**
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* Holds if this is the starting point of type tracking
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* when tracking a parameter into a call, but not out of it.
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*/
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predicate call() { hasCall = true and content = "" }
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/**
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* Holds if this is the end point of type tracking.
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*/
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predicate end() { content = "" }
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/**
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* INTERNAL. DO NOT USE.
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*
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* Holds if this type has been tracked into a call.
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*/
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boolean hasCall() { result = hasCall }
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/**
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* INTERNAL. DO NOT USE.
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*
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* Gets the content associated with this type tracker.
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*/
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string getContent() { result = content }
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/**
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* Gets a type tracker that starts where this one has left off to allow continued
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* tracking.
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*
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* This predicate is only defined if the type is not associated to a piece of content.
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*/
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TypeTracker continue() { content = "" and result = this }
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/**
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* Gets the summary that corresponds to having taken a forwards
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* heap and/or inter-procedural step from `nodeFrom` to `nodeTo`.
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*/
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pragma[inline]
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TypeTracker step(LocalSourceNode nodeFrom, LocalSourceNode nodeTo) {
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exists(StepSummary summary |
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StepSummary::step(nodeFrom, pragma[only_bind_out](nodeTo), pragma[only_bind_into](summary)) and
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result = this.append(pragma[only_bind_into](summary))
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)
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}
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/**
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* Gets the summary that corresponds to having taken a forwards
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* local, heap and/or inter-procedural step from `nodeFrom` to `nodeTo`.
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*
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* Unlike `TypeTracker::step`, this predicate exposes all edges
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* in the flow graph, and not just the edges between `Node`s.
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* It may therefore be less performant.
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*
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* Type tracking predicates using small steps typically take the following form:
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* ```ql
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* DataFlow::Node myType(DataFlow::TypeTracker t) {
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* t.start() and
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* result = < source of myType >
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* or
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* exists (DataFlow::TypeTracker t2 |
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* t = t2.smallstep(myType(t2), result)
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* )
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* }
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*
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* DataFlow::Node myType() {
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* result = myType(DataFlow::TypeTracker::end())
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* }
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* ```
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*/
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pragma[inline]
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TypeTracker smallstep(Node nodeFrom, Node nodeTo) {
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exists(StepSummary summary |
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StepSummary::smallstep(nodeFrom, nodeTo, summary) and
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result = this.append(summary)
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)
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or
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simpleLocalFlowStep(nodeFrom, nodeTo) and
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result = this
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}
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}
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/** Provides predicates for implementing custom `TypeTracker`s. */
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module TypeTracker {
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/**
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* Gets a valid end point of type tracking.
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*/
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TypeTracker end() { result.end() }
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}
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private newtype TTypeBackTracker = MkTypeBackTracker(Boolean hasReturn, OptionalContentName content)
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/**
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* Summary of the steps needed to back-track a use of a value to a given dataflow node.
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*
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* This can for example be used to track callbacks that are passed to a certain API,
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* so we can model specific parameters of that callback as having a certain type.
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*
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* Note that type back-tracking does not provide a source/sink relation, that is,
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* it may determine that a node will be used in an API call somewhere, but it won't
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* determine exactly where that use was, or the path that led to the use.
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*
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* It is recommended that all uses of this type are written in the following form,
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* for back-tracking some callback type `myCallback`:
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*
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* ```ql
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* DataFlow::LocalSourceNode myCallback(DataFlow::TypeBackTracker t) {
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* t.start() and
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* result = (< some API call >).getArgument(< n >).getALocalSource()
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* or
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* exists (DataFlow::TypeBackTracker t2 |
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* result = myCallback(t2).backtrack(t2, t)
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* )
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* }
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*
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* DataFlow::LocalSourceNode myCallback() { result = myCallback(DataFlow::TypeBackTracker::end()) }
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* ```
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*
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* Instead of `result = myCallback(t2).backtrack(t2, t)`, you can also use the equivalent
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* `t2 = t.step(result, myCallback(t2))`. If you additionally want to track individual
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* intra-procedural steps, use `t2 = t.smallstep(result, myCallback(t2))`.
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*/
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class TypeBackTracker extends TTypeBackTracker {
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Boolean hasReturn;
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string content;
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TypeBackTracker() { this = MkTypeBackTracker(hasReturn, content) }
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/** Gets the summary resulting from prepending `step` to this type-tracking summary. */
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TypeBackTracker prepend(StepSummary step) {
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step = LevelStep() and result = this
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or
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step = CallStep() and hasReturn = false and result = this
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or
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step = ReturnStep() and result = MkTypeBackTracker(true, content)
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or
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exists(string p |
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step = LoadStep(p) and content = "" and result = MkTypeBackTracker(hasReturn, p)
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)
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or
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step = StoreStep(content) and result = MkTypeBackTracker(hasReturn, "")
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}
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/** Gets a textual representation of this summary. */
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string toString() {
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exists(string withReturn, string withContent |
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(if hasReturn = true then withReturn = "with" else withReturn = "without") and
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(if content != "" then withContent = " with content " + content else withContent = "") and
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result = "type back-tracker " + withReturn + " return steps" + withContent
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)
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}
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/**
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* Holds if this is the starting point of type tracking.
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*/
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predicate start() { hasReturn = false and content = "" }
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/**
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* Holds if this is the end point of type tracking.
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*/
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predicate end() { content = "" }
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/**
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* INTERNAL. DO NOT USE.
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*
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* Holds if this type has been back-tracked into a call through return edge.
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*/
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boolean hasReturn() { result = hasReturn }
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/**
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* Gets a type tracker that starts where this one has left off to allow continued
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* tracking.
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*
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* This predicate is only defined if the type has not been tracked into a piece of content.
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*/
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TypeBackTracker continue() { content = "" and result = this }
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/**
|
||||
* Gets the summary that corresponds to having taken a backwards
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||||
* heap and/or inter-procedural step from `nodeTo` to `nodeFrom`.
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*/
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pragma[inline]
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TypeBackTracker step(LocalSourceNode nodeFrom, LocalSourceNode nodeTo) {
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exists(StepSummary summary |
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StepSummary::step(pragma[only_bind_out](nodeFrom), nodeTo, pragma[only_bind_into](summary)) and
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||||
this = result.prepend(pragma[only_bind_into](summary))
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||||
)
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||||
}
|
||||
|
||||
/**
|
||||
* Gets the summary that corresponds to having taken a backwards
|
||||
* local, heap and/or inter-procedural step from `nodeTo` to `nodeFrom`.
|
||||
*
|
||||
* Unlike `TypeBackTracker::step`, this predicate exposes all edges
|
||||
* in the flowgraph, and not just the edges between
|
||||
* `LocalSourceNode`s. It may therefore be less performant.
|
||||
*
|
||||
* Type tracking predicates using small steps typically take the following form:
|
||||
* ```ql
|
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* DataFlow::Node myType(DataFlow::TypeBackTracker t) {
|
||||
* t.start() and
|
||||
* result = < some API call >.getArgument(< n >)
|
||||
* or
|
||||
* exists (DataFlow::TypeBackTracker t2 |
|
||||
* t = t2.smallstep(result, myType(t2))
|
||||
* )
|
||||
* }
|
||||
*
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||||
* DataFlow::Node myType() {
|
||||
* result = myType(DataFlow::TypeBackTracker::end())
|
||||
* }
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||||
* ```
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||||
*/
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||||
pragma[inline]
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||||
TypeBackTracker smallstep(Node nodeFrom, Node nodeTo) {
|
||||
exists(StepSummary summary |
|
||||
StepSummary::smallstep(nodeFrom, nodeTo, summary) and
|
||||
this = result.prepend(summary)
|
||||
)
|
||||
or
|
||||
simpleLocalFlowStep(nodeFrom, nodeTo) and
|
||||
this = result
|
||||
}
|
||||
}
|
||||
|
||||
/** Provides predicates for implementing custom `TypeBackTracker`s. */
|
||||
module TypeBackTracker {
|
||||
/**
|
||||
* Gets a valid end point of type back-tracking.
|
||||
*/
|
||||
TypeBackTracker end() { result.end() }
|
||||
}
|
||||
@@ -0,0 +1,82 @@
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||||
/**
|
||||
* Provides Python-specific definitions for use in the type tracker library.
|
||||
*/
|
||||
|
||||
private import python
|
||||
private import semmle.python.dataflow.new.internal.DataFlowPublic as DataFlowPublic
|
||||
private import semmle.python.dataflow.new.internal.DataFlowPrivate as DataFlowPrivate
|
||||
|
||||
class Node = DataFlowPublic::Node;
|
||||
|
||||
class LocalSourceNode = DataFlowPublic::LocalSourceNode;
|
||||
|
||||
predicate simpleLocalFlowStep = DataFlowPrivate::simpleLocalFlowStep/2;
|
||||
|
||||
predicate jumpStep = DataFlowPrivate::jumpStep/2;
|
||||
|
||||
/**
|
||||
* Gets the name of a possible piece of content. For Python, this is currently only attribute names,
|
||||
* using the name of the attribute for the corresponding content.
|
||||
*/
|
||||
string getPossibleContentName() { result = any(DataFlowPublic::AttrRef a).getAttributeName() }
|
||||
|
||||
/**
|
||||
* Gets a callable for the call where `nodeFrom` is used as the `i`'th argument.
|
||||
*
|
||||
* Helper predicate to avoid bad join order experienced in `callStep`.
|
||||
* This happened when `isParameterOf` was joined _before_ `getCallable`.
|
||||
*/
|
||||
pragma[nomagic]
|
||||
private DataFlowPrivate::DataFlowCallable getCallableForArgument(
|
||||
DataFlowPublic::ArgumentNode nodeFrom, int i
|
||||
) {
|
||||
exists(DataFlowPrivate::DataFlowCall call |
|
||||
nodeFrom.argumentOf(call, i) and
|
||||
result = call.getCallable()
|
||||
)
|
||||
}
|
||||
|
||||
/** Holds if `nodeFrom` steps to `nodeTo` by being passed as a parameter in a call. */
|
||||
predicate callStep(DataFlowPublic::ArgumentNode nodeFrom, DataFlowPublic::ParameterNode nodeTo) {
|
||||
// TODO: Support special methods?
|
||||
exists(DataFlowPrivate::DataFlowCallable callable, int i |
|
||||
callable = getCallableForArgument(nodeFrom, i) and
|
||||
nodeTo.isParameterOf(callable, i)
|
||||
)
|
||||
}
|
||||
|
||||
/** Holds if `nodeFrom` steps to `nodeTo` by being returned from a call. */
|
||||
predicate returnStep(DataFlowPrivate::ReturnNode nodeFrom, Node nodeTo) {
|
||||
exists(DataFlowPrivate::DataFlowCall call |
|
||||
nodeFrom.getEnclosingCallable() = call.getCallable() and nodeTo.asCfgNode() = call.getNode()
|
||||
)
|
||||
}
|
||||
|
||||
/**
|
||||
* Holds if `nodeFrom` is being written to the `content` content of the object in `nodeTo`.
|
||||
*/
|
||||
predicate basicStoreStep(Node nodeFrom, Node nodeTo, string content) {
|
||||
exists(DataFlowPublic::AttrWrite a |
|
||||
a.mayHaveAttributeName(content) and
|
||||
nodeFrom = a.getValue() and
|
||||
nodeTo = a.getObject()
|
||||
)
|
||||
}
|
||||
|
||||
/**
|
||||
* Holds if `nodeTo` is the result of accessing the `content` content of `nodeFrom`.
|
||||
*/
|
||||
predicate basicLoadStep(Node nodeFrom, Node nodeTo, string content) {
|
||||
exists(DataFlowPublic::AttrRead a |
|
||||
a.mayHaveAttributeName(content) and
|
||||
nodeFrom = a.getObject() and
|
||||
nodeTo = a
|
||||
)
|
||||
}
|
||||
|
||||
/**
|
||||
* A utility class that is equivalent to `boolean` but does not require type joining.
|
||||
*/
|
||||
class Boolean extends boolean {
|
||||
Boolean() { this = true or this = false }
|
||||
}
|
||||
Reference in New Issue
Block a user