Summary:
In Java, we handle unknown code by propagating behavior from the parameters of the unknown function call to the return value (or constructed object, in the case of a constructor). But we do this in a somewhat silly way--generating a new summary with these semantics at each unknown call site. Instead, this diff introduces these two options as predefined behaviors and adds specialized code for them.
As a side effect of this approach, unknown functions are no longer counted as passthroughs. This is ok; the original behavior was less of a reasoned decision and more of an unintended consequence of the way we decided to handle unknown code.
This new approach ought to be more efficient than the old one, and as a virtuous side effect it will be easier to specify how to handle unknown code in other languages like C++.
Reviewed By: jeremydubreil
Differential Revision: D4205624
fbshipit-source-id: bf97445
Summary:
Our default strategy for handling unknown code is to propagate taint from the actuals to the return value.
But for commonly-used methods like `StringBuilder.append` (used every time you do `+` with a string in Java), this doesn't work.
The taint should be propagated to both the receiver and the return value in these cases.
I'm considering a solution where we always propagate taint to the receiver of unknown functions in the future, but I am concerned about the performance.
So let's stick with a few special string cases for now.
Reviewed By: cristianoc
Differential Revision: D4124355
fbshipit-source-id: 5b2a232
Summary:
this makes frontends no longer depend on SymExec.ml. `ModelBuiltins` was split into two modules:
- `BuiltinDecl` with procnames for builtins (used to determine whether some function is a builtin)
- `BuiltinDefn` with implementations used by `SymExec`
- they both have similar type defined in `BUILTINS.S` which makes sure that new builtin gets added into both modules.
During the refactor I ran some scripts:
`BuiltinDecl.ml`:
let X = create_procname "X"
cat BuiltinDecl.ml | grep "create_procname" | tail -70 | awk ' { print $1,$2,$3,$4,"\42"$2"\42"} '
then manually confirm string match. Exceptions:
"__exit" -> "_exit"
"objc_cpp_throw" -> "__infer_objc_cpp_throw"
__objc_dictionary_literal
nsArray_arrayWithObjects
nsArray_arrayWithObjectsCount
`BuiltinDefn.ml`:
let X = Builtin.register BuiltinDecl.X execute_X
cat BuiltinDecl.ml | grep "create_procname" | tail -70 | awk ' { print $1,$2,$3,"Builtin.register BuiltinDecl."$2,"execute_"$2} '
then, fix all compilation problems
Reviewed By: jberdine
Differential Revision: D3951035
fbshipit-source-id: f059602
Summary:
Right now, taint gets lost if it flows into a constructor or procedure whose implementation is missing.
Since the core Java (e.g., String) and Android classes (e.g, Intent) are among these, this is bad.
We could handle this by writing a bunch of models instead, but that would be a lot of work (plus we may still miss cases).
Reviewed By: jvillard
Differential Revision: D4051591
fbshipit-source-id: 65851c8
Sam Blackshear
Andrzej Kotulski