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4bbb11908f
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6e4a22b5c3
@ -3,7 +3,7 @@
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Booting
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=======
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After exploitation the goal is to fully boot the device.
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After exploitation the goal is to fully boot the device.
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Current boot chain:
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@ -19,63 +19,9 @@ As done by Frederic, the bootrom can be dumped using his provided scripts, and c
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./exynos-usbdl e payloads/Exynos8890_dump_bootrom.bin dumped_sboot.bin
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scripts/split-sboot-8890.sh dumped_sboot.bin
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This results in the following files:
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.. list-table:: bootrom stages
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:header-rows: 1
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* - File
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- Strings output
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- Likely boot stage?
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* - sboot.bin.1.bin
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- Exynos BL1
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- BL1
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* - sboot.bin.2.bin
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- BL31 %s
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- BL31
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* - sboot.bin.3.bin
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- Unsure. Contains strings like: TOP_DIV_ACLK_MFC_600 and APOLLO_DIV_APOLLO_RUN_MONITOR
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- BL2?
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* - sboot.bin.4.bin
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- Contains more textual information, and references to post BL2 boot, and android information
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- Kernel boot/BL33?
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debugger
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========
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After the initial loading of the debugger, the state reported is:
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.. code:: bash
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root | DEBUG |
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X0 : 0x0 | X1 : 0xffffffff | X2 : 0x20215d8 | X3 : 0x2021894 | X4 : 0x4 | X5 : 0x0 | X6 : 0x0 |
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X7 : 0x136c0008 | X8 : 0x2069000 | X9 : 0x0 | X10 : 0x2070000 | X11 : 0x0 | X12 : 0x0 | X13 : 0x0 |
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X14 : 0xf | X15 : 0x206d000 | X16 : 0x9 | X17 : 0x0 | X18 : 0x1 | X19 : 0x2000 | X20 : 0x2069000 |
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X21 : 0x0 | X22 : 0x0 | X23 : 0x0 | X24 : 0x0 | X25 : 0x0 | X26 : 0x0 | X27 : 0x1 |
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X28 : 0x0 | X29 : 0x2020f00 | LR/X30 : 0x20219b8 | SP/X31 : 0x2020ef0
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With the original bl1
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.. code:: bash
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root | DEBUG |
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X0 : 0x0 | X1 : 0x1 | X2 : 0x20215d8 | X3 : 0x2021894 | X4 : 0x4 | X5 : 0x0 | X6 : 0x0 |
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X7 : 0x136c0008 | X8 : 0x2069000 | X9 : 0x0 | X10 : 0x2070000 | X11 : 0x0 | X12 : 0x0 | X13 : 0x0 |
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X14 : 0xf | X15 : 0x20c4000 | X16 : 0x9 | X17 : 0x0 | X18 : 0x1 | X19 : 0x2000 | X20 : 0x2069000 |
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X21 : 0x0 | X22 : 0x0 | X23 : 0x0 | X24 : 0x0 | X25 : 0x0 | X26 : 0x0 | X27 : 0x1 |
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X28 : 0x0 | X29 : 0x2020f00 | LR/X30 : 0x20c0000 | SP/X31 : 0x2020ef0
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With a modified bl1
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.. code:: bash
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root | DEBUG |
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X0 : 0x0 | X1 : 0x1 | X2 : 0x20215d8 | X3 : 0x2021894 | X4 : 0x4 | X5 : 0x0 | X6 : 0x0 |
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X7 : 0x136c0008 | X8 : 0x2069000 | X9 : 0x0 | X10 : 0x2070000 | X11 : 0x0 | X12 : 0x0 | X13 : 0x0 |
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X14 : 0xf | X15 : 0x20c4000 | X16 : 0x9 | X17 : 0x0 | X18 : 0x1 | X19 : 0x2000 | X20 : 0x2069000 |
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X21 : 0x0 | X22 : 0x0 | X23 : 0x0 | X24 : 0x0 | X25 : 0x0 | X26 : 0x0 | X27 : 0x1 |
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X28 : 0x0 | X29 : 0x2020f00 | LR/X30 : 0x20c0000 | SP/X31 : 0x2020ef0
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Some other information about the debugger and it's current state.
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I relocated the debugger to ``0x20c0000`` to prevent overwriting it.
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@ -191,13 +137,6 @@ Replacing this function with our debugger makes us jump back:
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However this does not fully run bl1, so we will have to dig a bit deeper to see the puropose and when to jump back to the debugger.
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Authentication of BL1 seems to be done at ``0x0012848``. With return value '0' expected when this function is executed, to execute other functions.
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.. figure:: images/bl1_auth_references.png
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:align: center
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BL1 authentication.
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purpose
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-------
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bl1 interacts with several pheriperals, from the DTB these are:
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@ -8,11 +8,10 @@ OBJCOPY := $(ANDROID_NDK_ROOT)/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64
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LD := $(ANDROID_NDK_ROOT)/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android-ld.bfd
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#==================Target Samsung S7 (8890)==================
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CFLAGS_SAMSUNGS7 = -Os # -Os for optimization for size
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CFLAGS_SAMSUNGS7 = -Os
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dwc3:
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$(CC) entry.S -c -o entry.o $(CFLAGS_SAMSUNGS7) # -c compiles assembly code, and -o creates an object file (containing linking and symbol information)
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$(CC) $(CFLAGS_SAMSUNGS7) -c test_dwc3.c -o dwc3.o # compiles test_dwc3.c to dwc3.o
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$(LD) -T test_dwc3.ld entry.o dwc3.o -o dwc3.elf --just-symbols=symbols.txt # -T for linker script, --just-symbols for symbols file
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$(CC) entry.S -c -o entry.o $(CFLAGS_SAMSUNGS7)
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$(CC) $(CFLAGS_SAMSUNGS7) -c test_dwc3.c -o dwc3.o
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$(LD) -T test_dwc3.ld entry.o dwc3.o -o dwc3.elf --just-symbols=symbols.txt
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$(OBJCOPY) -O binary dwc3.elf dwc3.bin
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Binary file not shown.
Binary file not shown.
@ -1,17 +0,0 @@
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ifeq ($(ANDROID_NDK_ROOT),)
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$(error Error : Set the env variable 'ANDROID_NDK_ROOT' with the path of the Android NDK (version 20))
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endif
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CC := $(ANDROID_NDK_ROOT)/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android27-clang
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AR := $(ANDROID_NDK_ROOT)/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android-ar
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OBJCOPY := $(ANDROID_NDK_ROOT)/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android-objcopy
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LD := $(ANDROID_NDK_ROOT)/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android-ld.bfd
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#==================Target Samsung S7 (8890)==================
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CFLAGS_SAMSUNGS7 = -Os
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stage1:
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$(CC) entry.S -c -o entry.o $(CFLAGS_SAMSUNGS7)
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$(CC) $(CFLAGS_SAMSUNGS7) -c stage1.c -o stage1.o
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$(LD) -T linkscript.ld entry.o stage1.o -o stage1.elf --just-symbols=symbols.txt
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$(OBJCOPY) -O binary stage1.elf stage1.bin
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@ -1,8 +0,0 @@
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# Open a binary file and modify it
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bl1 = open('../S7/bl1.bin', 'rb').read()
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# Modify the binary file at 1C10
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bl1 = bl1[:0x1C1C] + b'\x48' + bl1[0x1C1D:]
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# Write the modified binary file
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open('../S7/bl1_mod.bin', 'wb').write(bl1)
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@ -15,4 +15,3 @@ stage1:
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$(CC) $(CFLAGS_SAMSUNGS7) -c stage1.c -o stage1.o
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$(LD) -T linkscript.ld entry.o stage1.o -o stage1.elf --just-symbols=symbols.txt
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$(OBJCOPY) -O binary stage1.elf stage1.bin
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