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85bebe18da
The ability to read a character from the console constitutes an attack
vector into TF-A, as it gives attackers a means to inject arbitrary
data into TF-A. It is dangerous to keep that feature enabled if not
strictly necessary, especially in production firmware builds.
Thus, we need a way to disable this feature. Moreover, when it is
disabled, all related code should be eliminated from the firmware
binaries, such that no remnant/dead getc() code remains in memory,
which could otherwise be used as a gadget as part of a bigger security
attack.
This patch disables getc() feature by default. For legitimate getc()
use cases [1], it can be explicitly enabled by building TF-A with
ENABLE_CONSOLE_GETC=1.
The following changes are introduced when getc() is disabled:
- The multi-console framework no longer provides the console_getc()
function.
- If the console driver selected by the platform attempts to register
a getc() callback into the multi-console framework then TF-A will
now fail to build.
If registered through the assembly function finish_console_register():
- On AArch64, you'll get:
Error: undefined symbol CONSOLE_T_GETC used as an immediate value.
- On AArch32, you'll get:
Error: internal_relocation (type: OFFSET_IMM) not fixed up
If registered through the C function console_register(), this requires
populating a struct console with a getc field, which will trigger:
error: 'console_t' {aka 'struct console'} has no member named 'getc'
- All console drivers which previously registered a getc() callback
have been modified to do so only when ENABLE_CONSOLE_GETC=1.
[1] Example of such use cases would be:
- Firmware recovery: retrieving a golden BL2 image over the console in
order to repair a broken firmware on a bricked board.
- Factory CLI tool: Drive some soak tests through the console.
Discussed on TF-A mailing list here:
https://lists.trustedfirmware.org/archives/list/tf-a@lists.trustedfirmware.org/thread/YS7F6RCNTWBTEOBLAXIRTXWIOYINVRW7/
Change-Id: Icb412304cd23dbdd7662df7cf8992267b7975cc5
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>
Acked-by: Baruch Siach <baruch@tkos.co.il>
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| .. | ||
| include | ||
| tsp | ||
| platform.mk | ||
| uniphier.h | ||
| uniphier_bl2_setup.c | ||
| uniphier_bl31_setup.c | ||
| uniphier_boot_device.c | ||
| uniphier_cci.c | ||
| uniphier_console.h | ||
| uniphier_console.S | ||
| uniphier_console_setup.c | ||
| uniphier_emmc.c | ||
| uniphier_gicv3.c | ||
| uniphier_helpers.S | ||
| uniphier_image_desc.c | ||
| uniphier_io_storage.c | ||
| uniphier_nand.c | ||
| uniphier_psci.c | ||
| uniphier_rotpk.S | ||
| uniphier_scp.c | ||
| uniphier_smp.S | ||
| uniphier_soc_info.c | ||
| uniphier_syscnt.c | ||
| uniphier_tbbr.c | ||
| uniphier_topology.c | ||
| uniphier_usb.c | ||
| uniphier_xlat_setup.c | ||