To make deobfuscation of literals more difficult, this update emulates the method used for obfuscating strings and byte slices. Some constants are now placed within lambda parameters (external keys). Additionally, with a certain probability, external keys can be further obfuscated using a global key stored in a global variable.
Go 1.20 is starting to deprecate the use of math/rand's global state,
per https://go.dev/issue/56319 and https://go.dev/issue/20661.
The reasoning is sound:
Deprecated: Programs that call Seed and then expect a specific sequence
of results from the global random source (using functions such as Int)
can be broken when a dependency changes how much it consumes from the
global random source. To avoid such breakages, programs that need a
specific result sequence should use NewRand(NewSource(seed)) to obtain a
random generator that other packages cannot access.
Aside from the tests, we used math/rand only for obfuscating literals,
which caused a deterministic series of calls like Intn. Our call to Seed
was also deterministic, per either GarbleActionID or the -seed flag.
However, our determinism was fragile. If any of our dependencies or
other packages made any calls to math/rand's global funcs, then our
determinism could be broken entirely, and it's hard to notice.
Start using separate math/rand.Rand objects for each use case.
Also make uses of crypto/rand use "cryptorand" for consistency.
Note that this requires a bit of a refactor in internal/literals
to start passing around Rand objects. We also do away with unnecessary
short funcs, especially since math/rand's Read never errors,
and we can obtain a byte via math/rand's Uint32.
Many files were missing copyright, so also add a short script to add the
missing lines with the current year, and run it.
The AUTHORS file is also self-explanatory. Contributors can add
themselves there, or we can simply update it from time to time via
git-shortlog.
Since we have two scripts now, set up a directory for them.
pagran
Daniel Martí
Nick
lu4p