This is a cross platform .dmg decryption tool. Maintained by 0cyn, but credit goes to its original owner.
On macOS, you will need to brew install openssl.
On Linux, you will need to apt install openssl openssl-dev.
To build on Linux, run make linux.
To build on macOS, run make mac.
On macOS, you can use the environment variable OPENSSL_DIR to override the one in the Makefile. Currently, it points to OpenSSL 3.3.1, which is what Homebrew installs on macOS Sonoma as of 2024-06-07.
To install, run sudo make install.
To clean, run make clean.
To uninstall, run sudo make uninstall.
To run, run vfdecrypt:
Usage: vfdecrypt -i in-file [-p password] [-k key] -o out-file
NOTICE: The -i and -o flags are extremely important, as without them, the program will never terminate unless forced to.
NOTICE: ONLY the -k -i and -o flags have been tested.
Let's say you have a file like iPhone4,1_9.3.5_13G36_Restore.ipsw and you want to extract the root file system. First, unzip the file:
unzip iPhone4,1_9.3.5_13G36_Restore.ipsw
Next, find the decryption keys on the iPhone wiki. This file is from an iPhone 4S (iPhone4,1) running iOS 9.3.5 with the build ID 13G36. So, following the links, you should arrive at this page, which tells us that the root filesystem is in 058-48374-036.dmg with the key 677d05afbb9a1eaa5f5e353829df15c4a5a6a2f7c2f354dadbff11e4aad7e97bf8f9275d.
You can now run vfdecrypt:
vfdecrypt -i iPhone4,1_9.3.5_13G36_Restore/058-48374-036.dmg -k 677d05afbb9a1eaa5f5e353829df15c4a5a6a2f7c2f354dadbff11e4aad7e97bf8f9275d -o decrypted.dmg
Finally, you can mount decrypted.dmg (or whatever you chose as a filename).