Redsn0w 0.9.5 is the tool from iPhone Dev team to jailbreak iPhone 3G 4.0 Beta firmware but if you have iPhone 3GS then you are out of luck, as Redsn0w 0.9.5 only supports iPhone 3G as of now. The jailbreak for OS 4.0 is released with only intention of motivating developers to get their applications ready for 4.0 which is expected to be announced at WWDC 2010.
Until Apple announces iPhone OS 4.0, don’t expect jailbreak tools for iPhone 3GS 4.0 but that doesn’t mean you can’t jailbreak now. One of enthusiastic iPhone hacker, Kaatje has successfully jailbreaked iPhone 3GS 4.0, however the process is not as easy as you may think.
The most interesting part of Kaatje’s jailbreak process is, retaining baseband of iPhone 3GS even after restoring to OS 4.0. Yes as you may guessed now, she managed to achieve this by creating custom OS 4.0 ipsw file and restoring on her test iPhone 3GS with the help of P0sixjinja. Since the baseband is still 05.11.07 the phone is not locked, it can be downgraded back to 3.1.3.
“I accomplished this by patching asr, lockdownd, LLB, iBEC, IBSS, iBoot, kernelcache, MobileSafari, Services.plist, and fstab. The binaries were patched with IDA Pro and OxED and were then diffed against the original pwned files with bsdiff to create patch files. I then took the diff files and built a firmware bundle that I dropped into Pwnagetool and updated the cydia tree within Pwnagetool as well. Once this was done, I created a custom ipsw with Pwnagetool, unzipped it, applied a pwned LLB from a pwnagetool generated 3.1.3 ipsw, zipped it back up and restored to my device.”
Screenshots after the break,
Since OS 4.0 is proprietary code of Apple, you won’t find custom iPhone OS 4.0 ipws anywhere. We suggest you to wait patiently till WWDC 2010.