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Thread: New Bootloader Exploit
11-30-2007, 06:46 PM #1
New Bootloader Exploit
Here's Geohot's update on hardware & software exploit for bootloader 4.06
New Bootloader Exploits
I found two exploits into the new bootloader, one hardware and one software. They are both untested and hard to implement, but I'm sure they will both work.
The version check reads from 0xA0021000 and 0xA0021004 to get the version of the main firmware. It then compares the values [0xA0021000]==~[0xA0021004]. If that check fails it ignores the version check. It is also the only bootloader access into high flash. So when A16 goes high, pull any data line high or low. That will cause the check to fail, and hence the version check to be skipped. And they shouldn't be any memory accesses in the bootloader, so it'll be fine.
This exploit is in the the way the secpack signature is padded. They did a lot to remove the really bad signature checking of the old bootloader that IPSF exploited. Although the secpack still has 0x28 bytes of data at the end that isn't checked for normal secpack sigs. The secpack sig is(0x30 header/padding, 0x14 main fw sha, 0x14 secpack sha, 0x28 unchecked padding) So by spoofing the first 0x58 of the RSA, you can set any secpack and main fw sha hash you want. It is very easy in exponent 3 RSA cryptosystems to spoof the first 1/3 of the message bytes. I believe with some clever math and brute force, the whole 0x58 can be spoofed. Any cryptology experts out there?
Read it here: http://iphonejtag.blogspot.com/2007/...-exploits.html
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11-30-2007, 10:59 PM #2
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