Methods have now moved away from bash and gdb to manually forking the binary, dumping and patching as needed. The majority of cracking tools started out as bash scripts that used gdb to dump the decrypted data xCrack, CrackTM, PCM etc. Uint32_t cryptid /* which enryption system,Ĭracking has legitimate uses in the Application Security industry, as well as for user's who wish to back up DRM-free copies of software they own, however the act of stripping DRM does allow the binary to be easily shared. Uint32_t cryptsize /* file size of encrypted range */ Uint32_t cryptoff /* file offset of encrypted range */ Uint32_t cmdsize /* sizeof(struct encryption_info_command) */ Resigning takes place because while the codesignature doesn't have to be valid thanks to the jailbreak, it does have to be in place unless you have AppSync or similar to disable codesignature checks. This will only work on jailbroken devices as codesignature validation has been removed. 'Cracking' works by letting the kernel decrypt the binary then siphoning the decrypted data into a new binary file, resigning, and repackaging. If cryptid is a non-zero value then the binary in encrypted. iOS can tell the encryption status of a binary via the cryptid struture member of LC_ENCRYPTION_INFO MachO load command. When iOS executes the binary, the decryption keys are used to decrypt the binary into a readable state where it is then loaded into memory and executed. This encrypts the binary so that decryption keys are needed in order to make the binary readable. App Store binaries are signed by both their developer and Apple.
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