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diff --git a/Documentation/mainboard/index.md b/Documentation/mainboard/index.md index a0436afb1f..ce30ee2f1c 100644 --- a/Documentation/mainboard/index.md +++ b/Documentation/mainboard/index.md @@ -92,6 +92,7 @@ The boards in this section are not real mainboards, but emulators. - [W530](lenovo/w530.md) - [T430 / T530 / X230 / W530 common](lenovo/xx30_series.md) - [T431s](lenovo/t431s.md) +- [Internal flashing](lenovo/ivb_internal_flashing.md) ### Haswell series diff --git a/Documentation/mainboard/lenovo/ivb_bios_flashing1.jpg b/Documentation/mainboard/lenovo/ivb_bios_flashing1.jpg Binary files differnew file mode 100644 index 0000000000..10a27b08e3 --- /dev/null +++ b/Documentation/mainboard/lenovo/ivb_bios_flashing1.jpg diff --git a/Documentation/mainboard/lenovo/ivb_bios_flashing2.jpg b/Documentation/mainboard/lenovo/ivb_bios_flashing2.jpg Binary files differnew file mode 100644 index 0000000000..4be1101e5f --- /dev/null +++ b/Documentation/mainboard/lenovo/ivb_bios_flashing2.jpg diff --git a/Documentation/mainboard/lenovo/ivb_bios_legacy_only.jpg b/Documentation/mainboard/lenovo/ivb_bios_legacy_only.jpg Binary files differnew file mode 100644 index 0000000000..aef9c7bfb1 --- /dev/null +++ b/Documentation/mainboard/lenovo/ivb_bios_legacy_only.jpg diff --git a/Documentation/mainboard/lenovo/ivb_bios_uefi_only.jpg b/Documentation/mainboard/lenovo/ivb_bios_uefi_only.jpg Binary files differnew file mode 100644 index 0000000000..7def81ed82 --- /dev/null +++ b/Documentation/mainboard/lenovo/ivb_bios_uefi_only.jpg diff --git a/Documentation/mainboard/lenovo/ivb_internal_flashing.md b/Documentation/mainboard/lenovo/ivb_internal_flashing.md new file mode 100644 index 0000000000..d0ac3cdd79 --- /dev/null +++ b/Documentation/mainboard/lenovo/ivb_internal_flashing.md @@ -0,0 +1,372 @@ +# Ivy Bridge Lenovo ThinkPad Internal Flashing + +## Introduction + +Old versions of stock BIOS for these models have several security issues. +In order to flash coreboot internally, two of them are of interest. + +**First** is the fact the SMM_BWP and BLE are not enabled in BIOS +versions released before 2014. We have tested many versions on T430 and +X230 and found out that SMM_BWP=1 only since the update, the changelog +of which contains following line: + +> (New) Improved the UEFI BIOS security feature. + +**Second** is [S3 Boot Script vulnerability](https://support.lenovo.com/eg/ru/product_security/s3_boot_protect), +that was discovered and fixed later. + +## Requirements + +- USB drive (in case you need to downgrade BIOS) +- Linux install that (can be) loaded in UEFI mode +- [CHIPSEC](https://github.com/chipsec/chipsec) + +## BIOS versions + +Below is a table of BIOS versions that are vulnerable enough for our +goals, per model. The version number means that you need to downgrade to +that or earlier version. + +```eval_rst ++------------+--------------+ +| Model | BIOS version | ++============+==============+ +| X230 | 2.60 | ++------------+--------------+ +| X230T | 2.58 | ++------------+--------------+ +| T430 | 2.64 | ++------------+--------------+ +| T430s | 2.59 | ++------------+--------------+ +| T530 | 2.60 | ++------------+--------------+ +| W530 | 2.58 | ++------------+--------------+ +``` + +If your BIOS version is equal or lower, skip to the +**[Examining protections](#examining-protections-theory)** section. If not, +go through the downgrade process, described next. + +## Downgrading BIOS + +Go to the Lenovo web site and download BIOS Update Bootable CD for your +machine of needed version (see above). + +Lenovo states that BIOS has "security rollback prevention", meaning once +you update it to some version X, you will not be able to downgrade it to +pre-X version. That's not true. It seems that this is completely +client-side restriction in flashing utilities (both Windows utility and +Bootable CD). You just need to call `winflash.exe` or `dosflash.exe` +directly. Therefore you need to modify the bootable CD image you just +downloaded. + +Extract an El Torito image: +``` +geteltorito -o ./bios.img g1uj41us.iso +``` +Mount the partition in that image: +``` +sudo mount -t vfat ./bios.img /mnt -o loop,offset=16384 +``` +List files, find the `AUTOEXEC.BAT` file and the `FLASH` directory: +``` +ls /mnt +ls /mnt/FLASH +``` + +Inside the `FLASH` directory, there should be a directory called +`G1ET93WW` or similar (exact name depends on your ThinkPad model and +BIOS version). See what's inside: +``` +ls /mnt/FLASH/G1ET93WW +``` +There must be a file with `.FL1` extension called `$01D2000.FL1` or +something similar. + +Now open the `AUTOEXEC.BAT` file: +``` +sudo vim /mnt/AUTOEXEC.BAT +``` +You will see a list of commands: +``` +@ECHO OFF +PROMPT $p$g +cd c:\flash +command.com +``` +Replace the last line (`command.com`) with this (change path to the +`.FL1` file according to yours): +``` +dosflash.exe /sd /file G1ET93WW\$01D2000.FL1 +``` + +Save the file, then unmount the partition: +``` +sudo unmount /mnt +``` + +Write this image to a USB drive (replace `/dev/sdX` with your USB drive +device name): +``` +sudo dd if=./bios.img of=/dev/sdX bs=1M +``` + +Now reboot and press F1 to enter BIOS settings. Open the **Startup** tab +and set the startup mode to **Legacy** (or **Both**/**Legacy First**): + + + +Press F10 to save changes and reboot. + +Now, before you process, make sure that AC adapter is connected! If your +battery will die during the process, you'll likely need external +programmer to recover. + +Boot from the USB drive (press F12 to select boot device), and BIOS +flashing process should begin: + + + + + +It may reboot a couple of times in the process. Do not interrupt it. + +When it's completed, go back to the BIOS settings and set startup mode +to **UEFI** (or **Both**/**UEFI First**). This is required for +vulnerability exploitation. + + + +Then boot to your system and make sure that `/sys/firmware/efi` or +`/sys/firmware/efivars` exist. + +## Examining protections (theory) + +There are two main ways that Intel platform provides to protect BIOS +chip: +- **BIOS_CNTL** register of LPC Interface Bridge Registers (accessible + via PCI configuration space, offset 0xDC). It has: + * **SMM_BWP** (*SMM BIOS Write Protect*) bit. If set to 1, the BIOS is + writable only in SMM. Once set to 1, cannot be changed anymore. + * **BLE** (*BIOS Lock Enable*) bit. If set to 1, setting BIOSWE to 1 + will raise SMI. Once set to 1, cannot be changed anymore. + * **BIOSWE** (*BIOS Write Enable*) bit. Controls whether BIOS is + writable. This bit is always R/W. +- SPI Protected Range Registers (**PR0**-**PR4**) of SPI Configuration + Registers (SPIBAR+0x74 - SPIBAR+0x84). Each register has bits that + define protected range, plus WP bit, that defines whether write + protection is enabled. + + There's also **FLOCKDN** bit of HSFS register (SPIBAR+0x04) of SPI + Configuration Registers. When set to 1, PR0-PR4 registers cannot be + written. Once set to 1, cannot be changed anymore. + +To be able to flash, we need SMM_BWP=0, BIOSWE=1, BLE=0, FLOCKDN=0 or +SPI protected ranges (PRx) to have a WP bit set to 0. + +Let's see what we have. Examine HSFS register: +``` +sudo chipsec_main -m chipsec.modules.common.spi_lock +``` +You should see that FLOCKDN=1: +``` +[x][ ======================================================================= +[x][ Module: SPI Flash Controller Configuration Locks +[x][ ======================================================================= +[*] HSFS = 0xE009 << Hardware Sequencing Flash Status Register (SPIBAR + 0x4) + [00] FDONE = 1 << Flash Cycle Done + [01] FCERR = 0 << Flash Cycle Error + [02] AEL = 0 << Access Error Log + [03] BERASE = 1 << Block/Sector Erase Size + [05] SCIP = 0 << SPI cycle in progress + [13] FDOPSS = 1 << Flash Descriptor Override Pin-Strap Status + [14] FDV = 1 << Flash Descriptor Valid + [15] FLOCKDN = 1 << Flash Configuration Lock-Down +``` + +Then check BIOS_CNTL and PR0-PR4: +``` +sudo chipsec_main -m common.bios_wp +``` +Good news: on old BIOS versions, SMM_BWP=0 and BLE=0. + +Bad news: there are 4 write protected SPI ranges: + +``` +[x][ ======================================================================= +[x][ Module: BIOS Region Write Protection +[x][ ======================================================================= +[*] BC = 0x 8 << BIOS Control (b:d.f 00:31.0 + 0xDC) + [00] BIOSWE = 0 << BIOS Write Enable + [01] BLE = 0 << BIOS Lock Enable + [02] SRC = 2 << SPI Read Configuration + [04] TSS = 0 << Top Swap Status + [05] SMM_BWP = 0 << SMM BIOS Write Protection +[-] BIOS region write protection is disabled! + +[*] BIOS Region: Base = 0x00500000, Limit = 0x00BFFFFF +SPI Protected Ranges +------------------------------------------------------------ +PRx (offset) | Value | Base | Limit | WP? | RP? +------------------------------------------------------------ +PR0 (74) | 00000000 | 00000000 | 00000000 | 0 | 0 +PR1 (78) | 8BFF0B40 | 00B40000 | 00BFFFFF | 1 | 0 +PR2 (7C) | 8B100B10 | 00B10000 | 00B10FFF | 1 | 0 +PR3 (80) | 8ADE0AD0 | 00AD0000 | 00ADEFFF | 1 | 0 +PR4 (84) | 8AAF0800 | 00800000 | 00AAFFFF | 1 | 0 +``` + +Other way to examine SPI configuration registers is to just dump SPIBAR: +``` +sudo chipsec_util mmio dump SPIBAR +``` +You will see SPIBAR address (0xFED1F800) and registers (for example, +00000004 is HSFS): +``` +[mmio] MMIO register range [0x00000000FED1F800:0x00000000FED1F800+00000200]: ++00000000: 0BFF0500 ++00000004: 0004E009 +... +``` +As you can see, the only thing we need is to unset WP bit on PR0-PR4. +But that cannot be done once FLOCKDN is set to 1. + +Now the fun part! + +FLOCKDN may only be cleared by a hardware reset, which includes S3 +state. On S3 resume boot path, the chipset configuration has to be +restored and it's done by executing so-called S3 Boot Scripts. You can +dump these scripts by executing: +``` +sudo chipsec_util uefi s3bootscript +``` +There are many entries. Along them, you can find instructions to write +to HSFS (remember, we know that SPIBAR is 0xFED1F800): +``` +Entry at offset 0x2B8F (len = 0x17, header len = 0x0): +Data: +02 00 17 02 00 00 00 01 00 00 00 04 f8 d1 fe 00 | +00 00 00 09 e0 04 00 | +Decoded: + Opcode : S3_BOOTSCRIPT_MEM_WRITE (0x0002) + Width : 0x02 (4 bytes) + Address: 0xFED1F804 + Count : 0x1 + Values : 0x0004E009 +``` +These scripts are stored in memory. The vulnerability is that we can +overwrite this memory, change these instructions and they will be +executed on S3 resume. Once we patch that instruction to not set FLOCKDN +bit, we will be able to write to PR0-PR4 registers. + +## Creating a backup + +Before you proceed, please create a backup of the `bios` region. Then, +in case something goes wrong, you'll be able to flash it back externally. + +The `me` region is locked, so an attempt to create a full dump will fail. +But you can back up the `bios`: +``` +sudo flashrom -p internal -r bios_backup.rom --ifd -i bios +``` + +If you will ever need to flash it back, use `--ifd -i bios` as well: +``` +sudo flashrom -p <YOUR_PROGRAMMER> -w bios_backup.rom --ifd -i bios +``` +**Caution:** if you will omit `--ifd -i bios` for flashing, you will +brick your machine, because your backup has `FF`s in place of `fd` and +`me` regions. Flash only `bios` region! + +## Removing protections (practice) + +The original boot script writes 0xE009 to HSFS. FLOCKDN is 15th bit, so +let's write 0x6009 instead: +``` +sudo chipsec_main -m tools.uefi.s3script_modify -a replace_op,mmio_wr,0xFED1F804,0x6009,0x2 +``` +You will get a lot of output and in the end you should see something +like this: +``` +[*] Modifying S3 boot script entry at address 0x00000000DAF49B8F.. +[mem] 0x00000000DAF49B8F +[*] Original entry: + 2 0 17 2 0 0 0 1 0 0 0 4 f8 d1 fe 0 | + 0 0 0 9 e0 4 0 | +[mem] buffer len = 0x17 to PA = 0x00000000DAF49B8F + 2 0 17 2 0 0 0 1 0 0 0 4 f8 d1 fe 0 | + 0 0 0 9 60 0 0 | ` +[mem] 0x00000000DAF49B8F +[*] Modified entry: + 2 0 17 2 0 0 0 1 0 0 0 4 f8 d1 fe 0 | + 0 0 0 9 60 0 0 | ` +[*] After sleep/resume, check the value of register 0xFED1F804 is 0x6009 +[+] PASSED: The script has been modified. Go to sleep.. +``` +Now go to S3, then resume and check FLOCKDN. It should be 0: +``` +sudo chipsec_main -m chipsec.modules.common.spi_lock +``` +``` +... +[x][ ======================================================================= +[x][ Module: SPI Flash Controller Configuration Locks +[x][ ======================================================================= +[*] HSFS = 0x6008 << Hardware Sequencing Flash Status Register (SPIBAR + 0x4) + [00] FDONE = 0 << Flash Cycle Done + [01] FCERR = 0 << Flash Cycle Error + [02] AEL = 0 << Access Error Log + [03] BERASE = 1 << Block/Sector Erase Size + [05] SCIP = 0 << SPI cycle in progress + [13] FDOPSS = 1 << Flash Descriptor Override Pin-Strap Status + [14] FDV = 1 << Flash Descriptor Valid + [15] FLOCKDN = 0 << Flash Configuration Lock-Down +[-] SPI Flash Controller configuration is not locked +[-] FAILED: SPI Flash Controller not locked correctly. +... +``` +Remove WP from protected ranges: +``` +sudo chipsec_util mmio write SPIBAR 0x74 0x4 0xAAF0800 +sudo chipsec_util mmio write SPIBAR 0x78 0x4 0xADE0AD0 +sudo chipsec_util mmio write SPIBAR 0x7C 0x4 0xB100B10 +sudo chipsec_util mmio write SPIBAR 0x80 0x4 0xBFF0B40 +``` +Verify that it worked: +``` +sudo chipsec_main -m common.bios_wp +``` +``` +[x][ ======================================================================= +[x][ Module: BIOS Region Write Protection +[x][ ======================================================================= +[*] BC = 0x 9 << BIOS Control (b:d.f 00:31.0 + 0xDC) + [00] BIOSWE = 1 << BIOS Write Enable + [01] BLE = 0 << BIOS Lock Enable + [02] SRC = 2 << SPI Read Configuration + [04] TSS = 0 << Top Swap Status + [05] SMM_BWP = 0 << SMM BIOS Write Protection +[-] BIOS region write protection is disabled! + +[*] BIOS Region: Base = 0x00500000, Limit = 0x00BFFFFF +SPI Protected Ranges +------------------------------------------------------------ +PRx (offset) | Value | Base | Limit | WP? | RP? +------------------------------------------------------------ +PR0 (74) | 0AAF0800 | 00800000 | 00AAF000 | 0 | 0 +PR1 (78) | 0ADE0AD0 | 00AD0000 | 00ADE000 | 0 | 0 +PR2 (7C) | 0B100B10 | 00B10000 | 00B10000 | 0 | 0 +PR3 (80) | 0BFF0B40 | 00B40000 | 00BFF000 | 0 | 0 +PR4 (84) | 00000000 | 00000000 | 00000000 | 0 | 0 +``` + +Bingo! + +Now you can [flash internally](/flash_tutorial/int_flashrom.md). +Remember to flash only the `bios` region (use `--ifd -i bios -N` +flashrom arguments). `fd` and `me` are still locked. + +Note that you should have an external SPI programmer as a backup method. +It will help you recover if you flash non-working ROM by mistake. |
