TBB: Add an IO abstraction layer to load encrypted firmwares

TBBR spec advocates for optional encryption of firmwares (see optional
requirement: R060_TBBR_FUNCTION). So add an IO abstaction layer to
support firmware decryption that can be stacked above any underlying IO/
packaging layer like FIP etc. It aims to provide a framework to load any
encrypted IO payload.

Also, add plat_get_enc_key_info() to be implemented in a platform
specific manner as handling of encryption key may vary from one platform
to another.

Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
Change-Id: I9892e0ddf00ebecb8981301dbfa41ea23e078b03

1 files changed, 27 insertions, 0 deletions

diff --git a/plat/common/plat_bl_common.c b/plat/common/plat_bl_common.c
index 6070db235..de6c1d176 100644
--- a/plat/common/plat_bl_common.c
+++ b/plat/common/plat_bl_common.c
@@ -11,6 +11,7 @@
 #include <common/debug.h>
 #include <lib/xlat_tables/xlat_tables_compat.h>
 #include <plat/common/platform.h>
+#include <tools_share/firmware_encrypted.h>
 
 /*
  * The following platform functions are weakly defined. The Platforms
@@ -22,6 +23,7 @@
 #pragma weak bl2_plat_handle_pre_image_load
 #pragma weak bl2_plat_handle_post_image_load
 #pragma weak plat_try_next_boot_source
+#pragma weak plat_get_enc_key_info
 
 void bl2_el3_plat_prepare_exit(void)
 {
@@ -53,6 +55,31 @@ int plat_try_next_boot_source(void)
 }
 
 /*
+ * Weak implementation to provide dummy decryption key only for test purposes,
+ * platforms must override this API for any real world firmware encryption
+ * use-case.
+ */
+int plat_get_enc_key_info(enum fw_enc_status_t fw_enc_status, uint8_t *key,
+			  size_t *key_len, unsigned int *flags,
+			  const uint8_t *img_id, size_t img_id_len)
+{
+#define DUMMY_FIP_ENC_KEY { 0x12, 0x34, 0x56, 0x78, 0x90, 0xab, 0xcd, 0xef, \
+			    0x12, 0x34, 0x56, 0x78, 0x90, 0xab, 0xcd, 0xef, \
+			    0x12, 0x34, 0x56, 0x78, 0x90, 0xab, 0xcd, 0xef, \
+			    0x12, 0x34, 0x56, 0x78, 0x90, 0xab, 0xcd, 0xef }
+
+	const uint8_t dummy_key[] = DUMMY_FIP_ENC_KEY;
+
+	assert(*key_len >= sizeof(dummy_key));
+
+	*key_len = sizeof(dummy_key);
+	memcpy(key, dummy_key, *key_len);
+	*flags = 0;
+
+	return 0;
+}
+
+/*
  * Set up the page tables for the generic and platform-specific memory regions.
  * The size of the Trusted SRAM seen by the BL image must be specified as well
  * as an array specifying the generic memory regions which can be;