hdiutil convert -format UDZO -o custom_rootfs.dmg decrypted_rootfs.dmg Re-encrypt (for compatibility with iBEC/iBSS) – optional, if you are using a bootrom exploit or patched iBSS . Many custom firmware workflows skip re-encryption and use a patched iBSS that accepts unencrypted images. Replace the original root filesystem DMG inside the IPSW structure with your custom one. Then modify BuildManifest.plist to remove signature checks (or use a tool like ipsw to rebuild).
Here’s a structured write-up for an project, written in a technical yet accessible style—ideal for a blog, forum post (e.g., Reddit r/LegacyJailbreak), or GitHub README. Write-Up: Building & Installing Custom Firmware on iPhone 4s Overview The iPhone 4s (A5 chip) represents a golden era for jailbreak experimentation. Unlike modern devices, its bootrom exploit (Limera1n – though partially patched) and persistent unsigned bootloader access via kloader allow for custom firmware that goes far beyond simple userland jailbreaks. iphone 4s custom firmware
Example:
xpwntool rootfs.dmg decrypted_rootfs.dmg -k <key> -iv <iv> Mount the decrypted DMG: hdiutil convert -format UDZO -o custom_rootfs
⚠️ : Messing with the baseband (BB) can permanently break cellular. Avoid modifying files inside /usr/local/standalone/firmware . Then modify BuildManifest
⚠️ : Bypassing activation lock via custom firmware is possible on some 4s models with hactivate patches, but this is legally gray and technically complex.
unzip iPhone4,1_6.1.3_Restore.ipsw -d firmware/ The root filesystem ( 048-XXXXX.dmg ) is encrypted with a per- device key. Use a tool like iDecrypt or xpwntool with the appropriate key (searchable in public key databases for 4s).
