Handle root offset and root table vtable invalidation (#7177)

* Handle invalid root offset

* Handle vtable offset invalidation

* Added script generator. Add more cases through vtable ref table size

* review responses

* vtable offset validation

* Moved padding insertion to the end. Tests invalid field lenghts

* table offsets validated. Added type after field

* validate string length

* add todo

* invalid vector length

* invalid structs

* general cleanup

* reworded invalid offsets

* example for vector of structs

* invalid vector of tables

* invalid vector of strings

* invalid vector of scalars

* vector of unions

* validate union type value

* invalid vector union type values

tests/annotated_binary/tests/README.md

@@ -0,0 +1,125 @@
+# Tests for Annotated Binaries
+
+## Invalid Binary Tests
+
+The following is a collection of manually corrupted binaries based off of
+`..\annotated_binary.bin`. Each file changes some offset or length/size entry to
+point so an invalid spot, and the generated annotated binaries demonstrate that
+those corruptions can be spotted.
+
+Each of these files were ran with the following command:
+
+```sh
+cd .tests/annotated_binary
+../../flatc -annotate annotated_binary.fbs tests/{binary_file}...
+```
+
+### `invalid_root_offset.bin`
+
+Changed first two bytes from `4400` to `FFFF` which produces an offset larger
+than the binary.
+
+### `invalid_root_table_vtable_offset.bin`
+
+Changed two bytes at 0x0044 from `3A00` to `FFFF` which points to an offset
+outside the binary.
+
+### `invalid_root_table_too_short.bin`
+
+Truncated the file to 0x46 bytes, as that cuts into the vtable offset field of
+the root table.
+
+```sh
+truncate annotated_binary.bin --size=70 >> invalid_root_table_too_short.bin
+```
+
+### `invalid_vtable_size.bin`
+
+Changed two bytes at 0x000A from `3A00` to `FFFF` which size is larger than the
+binary.
+
+### `invalid_vtable_size_short.bin`
+
+Changed two bytes at 0x000A from `3A00` to `0100` which size is smaller than the
+minimum size of 4 bytes.
+
+### `invalid_vtable_ref_table_size.bin`
+
+Changed two bytes at 0x000C from `6800` to `FFFF` which size is larger than the
+binary.
+
+### `invalid_vtable_ref_table_size_short.bin`
+
+Changed two bytes at 0x000C from `6800` to `0100` which size is smaller than 
+the minimum size of 4 bytes.
+
+### `invalid_vtable_field_offset.bin`
+
+Changed two bytes at 0x0016 from `1000` to `FFFF` which points to a field larger
+than the binary.
+
+### `invalid_table_field_size.bin`
+
+Truncated the file to 0x52 bytes, as that cuts a Uint32t value in half.
+
+### `invalid_table_field_offset.bin`
+
+Truncated the file to 0x96 bytes, as that cuts a UOffset32 value in half. Also,
+changed two bytes at 0x90 from `DC00` to `FFFF` which points to a section larger
+than the binary.
+
+### `invalid_string_length_cut_short.bin`
+
+Truncated the file to 0xAD bytes, as that cuts string length Uint32t value in 
+half.
+
+### `invalid_string_length.bin`
+
+Changed two bytes at 0x00AC from `0500` to `FFFF` which is a string length
+larger than the binary.
+
+### `invalid_vector_length_cut_short.bin`
+
+Truncated the file to 0x0136 bytes, as that cuts vector length Uint32t value in 
+half.
+
+### `invalid_struct_field_cut_short.bin`
+
+Truncated the file to 0x5d bytes, as that cuts struct field value in half.
+
+### `invalid_struct_array_field_cut_short.bin`
+
+Truncated the file to 0x6A bytes, as that cuts struct array field value in half.
+
+### `invalid_vector_structs_cut_short.bin`
+
+Truncated the file to 0x0154 bytes, as that cuts into a vector of structs.
+
+### `invalid_vector_tables_cut_short.bin`
+
+Truncated the file to 0x01DE bytes, as that cuts into a vector of table offsets.
+
+### `invalid_vector_strings_cut_short.bin`
+
+Truncated the file to 0x0176 bytes, as that cuts into a vector of string
+offsets.
+
+### `invalid_vector_scalars_cut_short.bin`
+
+Truncated the file to 0x01C1 bytes, as that cuts into a vector of scalars 
+values.
+
+### `invalid_vector_unions_cut_short.bin`
+
+Truncated the file to 0x01DE bytes, as that cuts into a vector of union offset 
+values.
+
+### `invalid_union_type_value.bin`
+
+Changed one byte at 0x004D from `02` to `FF` which is a union type value that is
+larger than the enum.
+
+### `invalid_vector_union_type_value.bin`
+
+Changed one byte at 0x0131 from `02` to `FF` which is a vector union type value 
+that is larger than the enum.