semanticcpg apidocs

Domain specific language for querying code property graphs

This is the API reference for the CPG query language, a language to mine code for defects and vulnerabilities both interactively on a code analysis shell (REPL), or using non-interactive scripts.

Queries written in the CPG query language express graph traversals (see https://en.wikipedia.org/wiki/Graph_traversal). Similar to the standard graph traversal language "Gremlin" (see https://en.wikipedia.org/wiki/Gremlin_(programming_language))) these traversals are formulated as sequences of primitive language elements referred to as "steps". You can think of a step as a small program, similar to a unix shell utility, however, instead of processing lines one by one, the step processes nodes of the graph.

==Starting a traversal== All traversals begin by selecting a set of start nodes, e.g.,

cpg.method

will start the traversal at all methods, while

cpg.local

will start at all local variables. The complete list of starting points can be found at

io.shiftleft.codepropertygraph.Cpg

==Lazy evaluation== Queries are lazily evaluated, e.g., cpg.method creates a traversal which you can add more steps to. You can, for example, evaluate the traversal by converting it to a list:

cpg.method.toList

Since toList is such a common operation, we provide the shorthand l, meaning that

cpg.method.l

provides the same result as the former query.

==Properties== Nodes have "properties", key-value pairs where keys are strings and values are primitive data types such as strings, integers, or Booleans. Properties of nodes can be selected based on their key, e.g.,

cpg.method.name

traverses to all method names. Nodes can also be filtered based on properties, e.g.,

cpg.method.name(".*exec.*")

traverse to all methods where name matches the regular expression ".exec.". You can see a complete list of properties by browsing to the API documentation of the corresponding step. For example, you can find the properties of method nodes at io.shiftleft.semanticcpg.language.types.structure.MethodTraversal.

==Side effects== Useful if you want to mutate something outside the traversal, or simply debug it: This prints all typeDecl names as it traverses the graph and increments i for each one.

 var i = 0
 cpg.typeDecl.sideEffect{typeTemplate => println(typeTemplate.name); i = i + 1}.exec

==[advanced] Selecting multiple things from your traversal== If you are interested in multiple things along the way of your traversal, you label anything using the as modulator, and use select at the end. Note that the compiler automatically derived the correct return type as a tuple of the labelled steps, in this case with two elements.

 cpg.method.as("method").definingTypeDecl.as("classDef").select.toList
 // return type: List[(Method, TypeDecl)]

==[advanced] For comprehensions== You can always start a new traversal from a node, e.g.,

 val someMethod = cpg.method.head
 someMethod.start.parameter.toList

You can use this e.g. in a for comprehension, which is (in this context) essentially an alternative way to select multiple intermediate things. It is more expressive, but more computationally expensive.

 val query = for {
   method <- cpg.method
   param <- method.start.parameter
 } yield (method.name, param.name)

 query.toList

Language for traversing the code property graph

Implicit conversions to specific steps, based on the node at hand. Automatically in scope when using anything in the steps package, e.g. Steps