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AT+stkprof
Used as an injection vector for the first iPhone 3G unlock payload.
Contents
Credit
Exploit
There is a stack-based buffer overflow in the at+stkprof command that allows unsigned code execution on the iPhone 3G baseband.
Implementation
The dev team used this exploit in the first public iPhone 3G unlock called yellowsn0w. It can be downloaded from Cydia, and is a daemon that will run in the background. It will inject their payload whenever the baseband is reset.
The source code is also available here [1]
New Implementation (yellowsn0w 0.9.6)
In the newest yellowsn0w, this command is still used as the injection vector for the exploit, but it is used differently. It is still the at+stkprof command, but it seems to send their stuff all in one go.
at+stkprof=122064a541c044b1878222803d0107001320133f8e720470000bf9f1 54000170100546e5640200000005c130100266e5640ddddddddeeeeeeeeb8905120 000000001010101020202020611301000c000000223B22270F32101C1743BAA 50BA40E78213501D00C297810B47A847A8786146C046C046C046C0701118C 93201340246C0E7EF370146C03030473829411+09pG79p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
Anyone with a better insight feel free to comment / modify, as I didn't look any further into this, I just looked at the ztringz :)
yellowsn0w 0.9.6 with comments
The exploit consists from 3 parts:
Code loader
ROM:00000000 ; =============== S U B R O U T I N E ======================================= ROM:00000000 ROM:00000000 ROM:00000000 loader ROM:00000000 LDR R2, =0x11700 ; unused ram to place code ROM:00000002 ADDS R4, R2, #1 ; thumb switch ROM:00000004 LDR R3, =0x40159FBF ; at-handler buffer where StrToHex result of the at-command is ROM:00000006 ROM:00000006 copy.loop ; CODE XREF: loader+12�j ROM:00000006 LDRB R0, [R3] ; copying code until double quotes ROM:00000008 CMP R0, #0x22 ; '"' ROM:0000000A BEQ run ; jump thumb code ROM:0000000C STRB R0, [R2] ROM:0000000E ADDS R2, #1 ROM:00000010 ADDS R3, #1 ROM:00000012 B copy.loop ; copying code until double quotes ROM:00000014 ; --------------------------------------------------------------------------- ROM:00000014 ROM:00000014 run ; CODE XREF: loader+A�j ROM:00000014 BX R4 ; jump thumb code ROM:00000014 ; End of function loader ROM:00000014 ROM:00000014 ; ---------------------------------------------------------------------------
Task creator
RAM:000119A0 ; =============== S U B R O U T I N E =======================================
RAM:000119A0
RAM:000119A0
RAM:000119A0 handler_replace
RAM:000119A0 LDR R0, =0x4011714C ; soft reset handler addr
RAM:000119A2 ADR R1, new_handler
RAM:000119A4 ADDS R1, #1 ; thumbing
RAM:000119A6 STR R1, [R0] ; setting new handler
RAM:000119A8 POP {R0-R4,PC} ; safe exit fixing stack
RAM:000119A8 ; End of function handler_replace
RAM:000119B0 ; =============== S U B R O U T I N E =======================================
RAM:000119B0
RAM:000119B0
RAM:000119B0 new_handler ; DATA XREF: handler_replace+2�o
RAM:000119B0 PUSH {R4-R7,LR}
RAM:000119B2 LDR R3, =0x403BB344 ; jamptable var
RAM:000119B4 MOVS R6, #0x80
RAM:000119B6 SUB SP, SP, #0x2C
RAM:000119B8 LSLS R6, R6, #4 ; 0x200
RAM:000119BA STRH R0, [R3] ; saving R0 to mem var
RAM:000119BC STR R1, [SP,#0x40+resp_string] ; saving responce prt to stack
RAM:000119BE LDR R4, =0x201420AC ; malloc
RAM:000119C0 ADDS R0, R6, #0
RAM:000119C2 BLX R4 ; malloc(0x200)
RAM:000119C4 MOVS R5, #0
RAM:000119C6 STR R0, [SP,#0x40+ptr_200] ; saving pointer to stack
RAM:000119C8 MOVS R0, #0x98 ; sizeof(NU_TASK)
RAM:000119CA BLX R4 ; malloc(0x98)
RAM:000119CC ADDS R7, R0, #0 ; R7 = task
RAM:000119CE STR R5, [R0,#0xC] ; task.field=0
RAM:000119D0 MOVS R0, 0x100
RAM:000119D4 BLX R4 ; malloc(0x100)
RAM:000119D6 MOVS R2, #0x80
RAM:000119D8 LDR R1, =task_loop ; src
RAM:000119DA LSLS R2, R2, #1 ; size to copy
RAM:000119DC LDR R3, =0x203C58A0 ; bytecpy
RAM:000119DE ADDS R4, R0, #0 ; R4 = dyn_task_loop
RAM:000119E0 BLX R3 ; bytecpy(task_loop, dyn_task_loop, 0x100)
RAM:000119E2 LDR R3, [SP,#0x40+ptr_200]
RAM:000119E4 STR R3, [SP,#4] ; void *stack_address = malloc(0x200)
RAM:000119E6 MOVS R3, #0x44
RAM:000119E8 STR R3, [SP,#0xC] ; priority = 0x44
RAM:000119EA MOVS R3, #0xA
RAM:000119EC ADDS R4, #1 ; thumbing dyn_task_loop
RAM:000119EE STR R3, [SP,#0x14] ; preempt = NU_PREEMPT
RAM:000119F0 MOVS R3, #0xC
RAM:000119F2 ADDS R2, R4, #0 ; void(*task_entry)
RAM:000119F4 STR R3, [SP,#0x18] ; auto_start = NU_START
RAM:000119F6 LDR R1, =devteam1 ; char *name
RAM:000119F8 STR R5, [SP] ; void *argv = 0
RAM:000119FA STR R6, [SP,#8] ; stack_size = 0x200
RAM:000119FC STR R5, [SP,#0x10] ; time_slice = 0
RAM:000119FE ADDS R0, R7, #0 ; NU_TASK *task
RAM:00011A00 MOVS R3, #0 ; int argc = 0
RAM:00011A02 LDR R4, =0x203FB540 ; NU_Create_Task
RAM:00011A04 BLX R4 ; status = NU_Create_Task()
RAM:00011A06 ADDS R2, R0, #0
RAM:00011A08 CMP R0, #0 ; success = zero
RAM:00011A0A BNE status_error
RAM:00011A0C LDR R1, =OK
RAM:00011A0E LDR R0, [SP,#0x40+resp_string]
RAM:00011A10 LDR R3, =0x2046DD00 ; sprintf
RAM:00011A12 BLX R3 ; sprintf(resp_string,"OK")
RAM:00011A14 B exit ; fixing stack
RAM:00011A16 ; ---------------------------------------------------------------------------
RAM:00011A16
RAM:00011A16 status_error ; CODE XREF: new_handler+5A�j
RAM:00011A16 LDR R1, =ERROR
RAM:00011A18 LDR R0, [SP,#0x40+resp_string]
RAM:00011A1A LDR R3, =0x2046DD00 ; sprintf
RAM:00011A1C BLX R3 ; sprintf(resp_string,"ERROR")
RAM:00011A1E
RAM:00011A1E exit ; CODE XREF: new_handler+64�j
RAM:00011A1E ADD SP, SP, #0x2C ; fixing stack
RAM:00011A20 POP {R4-R7,PC} ; bye
RAM:00011A20 ; End of function new_handler
RAM:00011A20
RAM:00011A20 ; ---------------------------------------------------------------------------
Unlock task loop
RAM:00011A64 ; =============== S U B R O U T I N E =======================================
RAM:00011A64
RAM:00011A64 task_loop ; DATA XREF: RAM:off_11A2C�o
RAM:00011A64 PUSH {R4,R5,LR}
RAM:00011A66 LDR R5, =0x40232754 ; sec mailbox
RAM:00011A68 SUB SP, SP, #0x14
RAM:00011A6A
RAM:00011A6A loop ; CODE XREF: task_loop+44�j
RAM:00011A6A LDR R3, =0x20165998 ; NU_Receive_From_Mailbox
RAM:00011A6C ADDS R0, R5, #0 ; NU_MAILBOX *mailbox
RAM:00011A6E MOV R1, SP ; void *Message
RAM:00011A70 MOVS R2, #0xFF ; Timeout
RAM:00011A72 BLX R3 ; NU_Receive_From_Mailbox(sec_mailbox,SP,0xFF)
RAM:00011A74 LDR R3, [SP] ; Message[0]
RAM:00011A76 CMP R3, #0xD ; Message[0] = 0xD ?
RAM:00011A78 BNE skip ;
RAM:00011A7A LDR R1, [SP,#4] ; Message[1]
RAM:00011A7C LDR R3, =0x402F79BC
RAM:00011A7E LDR R2, [R1] ; Message[1].field0
RAM:00011A80 STR R2, [R3] ; sec_task_var1 = Message[1].field0
RAM:00011A82 ADDS R3, #4 ; 0x402F79C0
RAM:00011A84 LDR R2, [R1,#4] ; Message[1].field1
RAM:00011A86 STR R2, [R3] ; sec_task_var2 = Message[1].field1
RAM:00011A88 LDR R2, [R1,#8] ; Message[1].field2
RAM:00011A8A LDR R3, =0x100FF00
RAM:00011A8C STR R3, [R2] ; Message[1].field2[0] = 0x100FF00
RAM:00011A8E LDR R3, =0x4020401
RAM:00011A90 STR R3, [R2,#4] ; Message[1].field2[1] = 0x4020401
RAM:00011A92 LDR R3, =0x4040403
RAM:00011A94 STR R3, [R2,#8] ; Message[1].field2[2] = 0x4040403
RAM:00011A96 MOVS R3, #1
RAM:00011A98 STR R3, [R1,#0xC] ; Message[1].field3 = 1
RAM:00011A9A MOVS R3, #0x20
RAM:00011A9C STR R3, [SP] ; Message[0] = 0x20
RAM:00011A9E
RAM:00011A9E skip ; CODE XREF: task_loop+14�j
RAM:00011A9E ADDS R0, R5, #0 ; sec mailbox
RAM:00011AA0 MOV R1, SP ; void *Message
RAM:00011AA2 MOVS R2, #0xFF ; timeout
RAM:00011AA4 LDR R3, =0x203ED568
RAM:00011AA6 BLX R3 ; NU_Send_To_Mailbox()
RAM:00011AA8 B loop ; NU_Receive_From_Mailbox
RAM:00011AA8 ; End of function task_loop
