add ability to use out of band transitions

Currently the NULL character is used as an out of band transition
for string/path elements. This works for them as the NULL character
is not valid for this data. However this does not work for binary
data that can contain a NULL character.

So far we have only dealt with fixed length fields of binary data
making the NULL separator either unnecessary.

However binary data like in the xattr match and mount data field are
variable length and can contain NULL characters. To deal with this
add the ability to specify out of band transitions, that can only
be triggered by code not input data.

The out of band transition can be used to separate variable length
data fields just as the NULL transition has been used to separate
variable length strings.

In the compressed hfa out of band transitions are expressed as a
negative offset from the states base. This leaves us room to expand
the character match range in the future if desired and on average
makes the range between the out of band transition and the input
transitions smaller than would be had if the out of band transition
had been stored after the valid input transitions.

Out of band transitions in the dfa will not break old kernels
that don't know about them, but they won't be able to trigger
the out of band transition match. So they should not be used unless
the kernel indicates that it supports them.

It should be noted that this patch only adds support for a single
out of band transition. If multiple out of band transitions are
required. It is trivial to extend.
- Add a tag indicating support in the kernel
- add a oob max range field to the dfa header so the kernel knows
  what the max range that needs verifying is.
- extend oob generation fns to generate oob based on value instead
  of a fixed -1.

Signed-off-by: John Johansen <john.johansen@canonical.com>

parser/libapparmor_re/chfa.h

@@ -28,6 +28,7 @@
 
 #define BASE32_FLAGS 0xff000000
 #define DiffEncodeBit32 0x80000000
+#define MATCH_FLAG_OOB_TRANSITION 0x20000000
 #define base_mask_size(X) ((X) & ~BASE32_FLAGS)
 
 using namespace std;
@@ -54,7 +55,7 @@ class CHFA {
 	map<const State *, size_t> num;
 	map<transchar, transchar> &eq;
 	transchar max_eq;
-	size_t first_free;
+	ssize_t first_free;
 	unsigned int chfaflags;
 };