Sandrine Bailleux 85bebe18da refactor(console): disable getc() by default ... 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>		2023-10-11 08:40:14 +02:00
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console/aarch64	refactor(console): disable getc() by default	2023-10-11 08:40:14 +02:00
crypto	refactor(libc): clean up dependencies in libc	2022-09-22 13:23:49 +02:00