Module ExternalFlow

INTERNAL use only. This is an experimental API subject to change without notice.

Provides classes and predicates for dealing with flow models specified in data extensions and CSV format.

The CSV specification has the following columns:

• Sources: package; type; subtypes; name; signature; ext; output; kind; provenance
• Sinks: package; type; subtypes; name; signature; ext; input; kind; provenance
• Summaries: package; type; subtypes; name; signature; ext; input; output; kind; provenance
• Neutrals: package; type; name; signature; kind; provenance A neutral is used to indicate that a callable is neutral with respect to flow (no summary), source (is not a source) or sink (is not a sink).

The interpretation of a row is similar to API-graphs with a left-to-right reading.

1. The package column selects a package.

2. The type column selects a type within that package.

3. The subtypes is a boolean that indicates whether to jump to an arbitrary subtype of that type.

4. The name column optionally selects a specific named member of the type.

5. The signature column optionally restricts the named member. If signature is blank then no such filtering is done. The format of the signature is a comma-separated list of types enclosed in parentheses. The types can be short names or fully qualified names (mixing these two options is not allowed within a single signature).

6. The ext column specifies additional API-graph-like edges. Currently there are only two valid values: "" and “Annotated”. The empty string has no effect. “Annotated” applies if name and signature were left blank and acts by selecting an element that is annotated by the annotation type selected by the first 4 columns. This can be another member such as a field or method, or a parameter.

7. The input column specifies how data enters the element selected by the first 6 columns, and the output column specifies how data leaves the element selected by the first 6 columns. An input can be a dot separated path consisting of either "", “Argument[n]”, “Argument[n1..n2]”, “ReturnValue”, “Element”, “WithoutElement”, or “WithElement”:

   • "": Selects a write to the selected element in case this is a field.
   • “Argument[n]”: Selects an argument in a call to the selected element. The arguments are zero-indexed, and this specifies the qualifier.
   • “Argument[n1..n2]”: Similar to “Argument[n]” but select any argument in the given range. The range is inclusive at both ends.
   • “ReturnValue”: Selects a value being returned by the selected element. This requires that the selected element is a method with a body.
   • “Element”: Selects the collection elements of the selected element.
   • “WithoutElement”: Selects the selected element but without its collection elements.
   • “WithElement”: Selects the collection elements of the selected element, but points to the selected element.

   An output can be can be a dot separated path consisting of either "", “Argument[n]”, “Argument[n1..n2]”, “Parameter”, “Parameter[n]”, “Parameter[n1..n2]”, “ReturnValue”, or “Element”:

   • "": Selects a read of a selected field, or a selected parameter.
   • “Argument[n]”: Selects the post-update value of an argument in a call to the selected element. That is, the value of the argument after the call returns. The arguments are zero-indexed, and this specifies the qualifier.
   • “Argument[n1..n2]”: Similar to “Argument[n]” but select any argument in the given range. The range is inclusive at both ends.
   • “Parameter”: Selects the value of a parameter of the selected element. “Parameter” is also allowed in case the selected element is already a parameter itself.
   • “Parameter[n]”: Similar to “Parameter” but restricted to a specific numbered parameter (zero-indexed, and this specifies the value of this).
   • “Parameter[n1..n2]”: Similar to “Parameter[n]” but selects any parameter in the given range. The range is inclusive at both ends.
   • “ReturnValue”: Selects the return value of a call to the selected element.
   • “Element”: Selects the collection elements of the selected element.

8. The kind column is a tag that can be referenced from QL to determine to which classes the interpreted elements should be added. For example, for sources “remote” indicates a default remote flow source, and for summaries “taint” indicates a default additional taint step and “value” indicates a globally applicable value-preserving step. For neutrals the kind can be summary, source or sink to indicate that the neutral is neutral with respect to flow (no summary), source (is not a source) or sink (is not a sink).

9. The provenance column is a tag to indicate the origin and verification of a model. The format is {origin}-{verification} or just “manual” where the origin describes the origin of the model and verification describes how the model has been verified. Some examples are:

   • “df-generated”: The model has been generated by the model generator tool.
   • “df-manual”: The model has been generated by the model generator and verified by a human.
   • “manual”: The model has been written by hand. This information is used in a heuristic for dataflow analysis to determine, if a model or source code should be used for determining flow.