MachoView should define imported symbols even if they are not presented in SYMTAB

[mostobriv]

Version and Platform (required):

• Binary Ninja Version: 5.2.8012-dev Personal (aec518eb)

Bug Description:
Current implementation of MachoView relies on symtab when defining the symbols in the macho. However it is possible to bind imported (external) symbols even if they are not in the symtab, as binding from DYLD_INFO uses their own inlined strings. So for the cases when symbol is used in the binding, but not listed in the symtab, leads to the error with applying relocation during macho analysis.

Steps To Reproduce:
Please provide all steps required to reproduce the behavior:

1. Open attached binary
2. Go to 0x100004000
3. There is null instead of external symbol

Expected Behavior:
I think MachoView should define symbols when they referenced in the dyld binding as well.

Screenshots/Video Recording:

Binary:
bin.zip

Additional Information:
Definition of the imported macho symbol is nested in the loop over symtab, so if there is no symbols (symtab.nsyms == 0) then no symbols will be defined, it's incorrect.

binaryninja-api/view/macho/machoview.cpp

Line 3121 in 2f1d09c

for (size_t i = 0; i < symtab.nsyms; i++)

[mostobriv]

Found out, that MachoView even won't apply any relocations due to failed search of symbol, so bv.relocations_at(addr) == []

[mostobriv]

Here is a bit more interesting example. In this binary dynsymtab and symtab is empty, however there is plenty of bindings in DYLD_INFO, even weak bindings into self

libloader.zip