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05d0dd1801
We used to rely on a parallel implementation of an object file parser and writer to be able to obfuscate import paths. After compiling each package, we would parse the object file, replace the import paths, and write the updated object file in-place. That worked well, in most cases. Unfortunately, it had some flaws: * Complexity. Even when most of the code is maintained in a separate module, the import_obfuscation.go file was still close to a thousand lines of code. * Go compatibility. The object file format changes between Go releases, so we were supporting Go 1.15, but not 1.16. Fixing the object file package to work with 1.16 would probably break 1.15 support. * Bugs. For example, we recently had to add a workaround for #224, since import paths containing dots after the domain would end up escaped. Another example is #190, which seems to be caused by the object file parser or writer corrupting the compiled code and causing segfaults in some rare edge cases. Instead, let's drop that method entirely, and force the compiler and linker to do the work for us. The steps necessary when compiling a package to obfuscate are: 1) Replace its "package foo" lines with the obfuscated package path. No need to separate the package path and name, since the obfuscated path does not contain slashes. 2) Replace the "-p pkg/foo" flag with the obfuscated path. 3) Replace the "import" spec lines with the obfuscated package paths, for those dependencies which were obfuscated. 4) Replace the "-importcfg [...]" file with a version that uses the obfuscated paths instead. The linker also needs that last step, since it also uses an importcfg file to find object files. There are three noteworthy drawbacks to this new method: 1) Since we no longer write object files, we can't use them to store data to be cached. As such, the -debugdir flag goes back to using the "-a" build flag to always rebuild all packages. On the plus side, that caching didn't work very well; see #176. 2) The package name "main" remains in all declarations under it, not just "func main", since we can only rename entire packages. This seems fine, as it gives little information to the end user. 3) The -tiny mode no longer sets all lines to 0, since it did that by modifying object files. As a temporary measure, we instead set all top-level declarations to be on line 1. A TODO is added to hopefully improve this again in the near future. The upside is that we get rid of all the issues mentioned before. Plus, garble now nearly works with Go 1.16, with the exception of two very minor bugs that look fixable. A follow-up PR will take care of that and start testing on 1.16. Fixes #176. Fixes #190. |
3 years ago | |
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| bench | 4 years ago | |
| mod | 3 years ago | |
| scripts | 3 years ago | |