Merge pull request #1944 from AFLplusplus/inject

Inject fuzzing

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+# Injection fuzzing
+
+Coverage guided fuzzing so far is only able to detect crashes, so usually
+memory corruption issues, or - if implemented by hand in the harness -
+invariants.
+
+This is a proof-of-concept implementation to additionally hunt for injection
+vulnerabilities.
+It works by instrumenting calls to specific functions and parsing the
+query parameter for a specific unescaped dictionary string, and if detected,
+crashes the target.
+
+This has a very low false positive rate.
+But obviously this can only find injection vulnerailities that are suspectible
+to this specific (but most common) issue. Hence in a rare kind of injection
+vulnerability this won't find the bug - and be a false negative.
+But this can be tweaked by the user - see the HOW TO MODIFY section below.
+
+## How to use
+
+Set one or more of the following environment variables for **compiling**
+the target and - *this is important* - when **fuzzing** the target:
+
+ - `AFL_LLVM_INJECTIONS_SQL`
+ - `AFL_LLVM_INJECTIONS_LDAP`
+ - `AFL_LLVM_INJECTIONS_XSS`
+
+Alternatively you can set `AFL_LLVM_INJECTIONS_ALL` to enable all.
+
+## How to modify
+
+If you want to add more fuctions to check for e.g. SQL injections:
+Add these to `instrumentation/injection-pass.cc` and recompile.
+
+If you want to test for more injection inputs:
+Add the dictionary tokens to `src/afl-fuzz.c` and the check for them to
+`instrumentation/afl-compiler-rt.o.c`.
+
+If you want to add new injection targets:
+You will have to edit all three files.
+
+Just search for:
+```
+// Marker: ADD_TO_INJECTIONS
+```
+in the files to see where this needs to be added.
+
+**NOTE:** pull requests to improve this feature are highly welcome :-)