vboot2: Introduce vb2ex_hwcrypto APIstabilize-storm-6683.Bstabilize-6670.Bstabilize-6662.B

This patch extends the vboot2 API by three callback functions that the
platform firmware may implement to offer hardware crypto engine support.
For now we only support this for hash algorithms, and we will only allow
it for firmware body hashes (not the keyblock or preamble which are too
small to matter execution-time-wise anyway). The API is similar to the
vb2api_*_hash() functions used to start body hashing in the first place,
but we still take this round trip through vboot to allow it to do
key/signature management and retain full control of the verification
process. We also add a new preamble flag to explicitly disable this
feature, so that we can later return to a solely software-based
verification path through a firmware update in case a hardware crypto
engine turns out to be insecure.

CQ-DEPEND=CL:236435
BRANCH=None
BUG=chrome-os-partner:32987
TEST='make runtests VBOOT2=1'. Manually booted on Pinky with and without
HW crypto support and with the preamble flag set to confirm expected
behavior. lib21/ parts untested except for compiling and new unit tests.

Change-Id: I17c7d02f392089875a5942a5aafcf6a657354863
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/236453
Reviewed-by: Randall Spangler <rspangler@chromium.org>

1 files changed, 23 insertions, 0 deletions

diff --git a/firmware/2lib/2stub.c b/firmware/2lib/2stub.c
index 7c9e5b17..375d4faf 100644
--- a/firmware/2lib/2stub.c
+++ b/firmware/2lib/2stub.c
@@ -8,11 +8,13 @@
 #include "2sysincludes.h"
 #include "2api.h"
 
+__attribute__((weak))
 int vb2ex_tpm_clear_owner(struct vb2_context *ctx)
 {
 	return VB2_ERROR_EX_TPM_CLEAR_OWNER_UNIMPLEMENTED;
 }
 
+__attribute__((weak))
 int vb2ex_read_resource(struct vb2_context *ctx,
 			enum vb2_resource_index index,
 			uint32_t offset,
@@ -21,3 +23,24 @@ int vb2ex_read_resource(struct vb2_context *ctx,
 {
 	return VB2_ERROR_EX_READ_RESOURCE_UNIMPLEMENTED;
 }
+
+__attribute__((weak))
+int vb2ex_hwcrypto_digest_init(enum vb2_hash_algorithm hash_alg,
+			       uint32_t data_size)
+{
+	return VB2_ERROR_EX_HWCRYPTO_UNSUPPORTED;
+}
+
+__attribute__((weak))
+int vb2ex_hwcrypto_digest_extend(const uint8_t *buf,
+				 uint32_t size)
+{
+	return VB2_ERROR_SHA_EXTEND_ALGORITHM;	/* Should not be called. */
+}
+
+__attribute__((weak))
+int vb2ex_hwcrypto_digest_finalize(uint8_t *digest,
+				   uint32_t digest_size)
+{
+	return VB2_ERROR_SHA_FINALIZE_ALGORITHM; /* Should not be called. */
+}