Extracts (uncaches) a dyld shared cache file on macOS

uncache_dylds.c

#include <dlfcn.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>

/*

  Extracts (uncaches) a dyld shared cache file on macOS

  Compile:

      cc uncache_dylds.c -o uncache_dylds

  Example:

      uncache_dylds /…/Cryptexes/…/dyld/dyld_shared_cache_arm64e outdir

*/


#define EXTACTOR_BUNDLE "/usr/lib/dsc_extractor.bundle"
#define EXTRACT_FN "dyld_shared_cache_extract_dylibs_progress"

/*
  uncache

  Parameters:

      cache: path to the dyld cache file
      out: path to output directory
      progress: block with two int arguments: current & total

  Returns:

    0 on success // I, um, think?

 */
int
(*uncache)(const char *cache, const char *out, void (^progress)(int, int));

int
main(int argc, char **argv)
{
    if (argc < 3) {
        fprintf(stderr, "usage: %s <dyld-shared-cache> <outdir>\n", argv[0]);
        exit(1);
    }

    void *bundle = dlopen(EXTACTOR_BUNDLE, RTLD_LAZY);
    if (!bundle) {
        fprintf(stderr, "load error: " EXTACTOR_BUNDLE " did not open\n");
        fprintf(stderr, "dlerror: %s\n", dlerror());
        exit(1);
    }

    uncache = dlsym(bundle, EXTRACT_FN);
    if (!uncache) {
        fprintf(stderr, "not found: " EXTRACT_FN "\n");
        fprintf(stderr, "dlerror: %s\n", dlerror());
        exit(1);
    }

    int result = uncache(argv[1], argv[2], ^(int i, int n) {
        fprintf(stderr, ".");
    });
    fprintf(stderr, "\nresult=%d\n", result);

    return 0;
}