vboot2: Introduce vb2ex_hwcrypto API

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>

8 files changed, 96 insertions, 32 deletions

diff --git a/firmware/2lib/2api.c b/firmware/2lib/2api.c
index 5d2775f0..1a616d5b 100644
--- a/firmware/2lib/2api.c
+++ b/firmware/2lib/2api.c
@@ -118,5 +118,8 @@ int vb2api_extend_hash(struct vb2_context *ctx,
 
 	sd->hash_remaining_size -= size;
 
-	return vb2_digest_extend(dc, buf, size);
+	if (dc->using_hwcrypto)
+		return vb2ex_hwcrypto_digest_extend(buf, size);
+	else
+		return vb2_digest_extend(dc, buf, size);
 }
diff --git a/firmware/2lib/2sha_utility.c b/firmware/2lib/2sha_utility.c
index 47581ea4..6f76b4e7 100644
--- a/firmware/2lib/2sha_utility.c
+++ b/firmware/2lib/2sha_utility.c
@@ -84,6 +84,7 @@ int vb2_digest_init(struct vb2_digest_context *dc,
 		    enum vb2_hash_algorithm hash_alg)
 {
 	dc->hash_alg = hash_alg;
+	dc->using_hwcrypto = 0;
 
 	switch (dc->hash_alg) {
 #if VB2_SUPPORT_SHA1
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. */
+}
diff --git a/firmware/2lib/include/2api.h b/firmware/2lib/include/2api.h
index 1ce6a09f..0c5792d8 100644
--- a/firmware/2lib/include/2api.h
+++ b/firmware/2lib/include/2api.h
@@ -21,6 +21,7 @@
 #define VBOOT_2_API_H_
 #include <stdint.h>
 
+#include "2crypto.h"
 #include "2fw_hash_tags.h"
 #include "2guid.h"
 #include "2recovery_reasons.h"
@@ -364,4 +365,33 @@ int vb2ex_read_resource(struct vb2_context *ctx,
 			uint32_t size);
 
 void vb2ex_printf(const char *func, const char *fmt, ...);
+
+/**
+ * Initialize the hardware crypto engine to calculate a block-style digest.
+ *
+ * @param hash_alg	Hash algorithm to use
+ * @param data_size	Expected total size of data to hash
+ * @return VB2_SUCCESS, or non-zero error code (HWCRYPTO_UNSUPPORTED not fatal).
+ */
+int vb2ex_hwcrypto_digest_init(enum vb2_hash_algorithm hash_alg,
+			       uint32_t data_size);
+
+/**
+ * Extend the hash in the hardware crypto engine with another block of data.
+ *
+ * @param buf		Next data block to hash
+ * @param size		Length of data block in bytes
+ * @return VB2_SUCCESS, or non-zero error code.
+ */
+int vb2ex_hwcrypto_digest_extend(const uint8_t *buf, uint32_t size);
+
+/**
+ * Finalize the digest in the hardware crypto engine and extract the result.
+ *
+ * @param digest	Destination buffer for resulting digest
+ * @param digest_size	Length of digest buffer in bytes
+ * @return VB2_SUCCESS, or non-zero error code.
+ */
+int vb2ex_hwcrypto_digest_finalize(uint8_t *digest, uint32_t digest_size);
+
 #endif  /* VBOOT_2_API_H_ */
diff --git a/firmware/2lib/include/2crypto.h b/firmware/2lib/include/2crypto.h
index e930de84..559a8ed1 100644
--- a/firmware/2lib/include/2crypto.h
+++ b/firmware/2lib/include/2crypto.h
@@ -28,4 +28,35 @@ enum vb2_crypto_algorithm {
 	VB2_ALG_COUNT
 };
 
+/* Algorithm types for signatures */
+enum vb2_signature_algorithm {
+	/* Invalid or unsupported signature type */
+	VB2_SIG_INVALID = 0,
+
+	/*
+	 * No signature algorithm.  The digest is unsigned.  See
+	 * VB2_GUID_NONE_* above for key GUIDs to use with this algorithm.
+	 */
+	VB2_SIG_NONE = 1,
+
+	/* RSA algorithms of the given length in bits (1024-8192) */
+	VB2_SIG_RSA1024 = 2,  /* Warning!  This is likely to be deprecated! */
+	VB2_SIG_RSA2048 = 3,
+	VB2_SIG_RSA4096 = 4,
+	VB2_SIG_RSA8192 = 5,
+};
+
+/* Algorithm types for hash digests */
+enum vb2_hash_algorithm {
+	/* Invalid or unsupported digest type */
+	VB2_HASH_INVALID = 0,
+
+	/* SHA-1.  Warning: This is likely to be deprecated soon! */
+	VB2_HASH_SHA1 = 1,
+
+	/* SHA-256 and SHA-512 */
+	VB2_HASH_SHA256 = 2,
+	VB2_HASH_SHA512 = 3,
+};
+
 #endif /* VBOOT_REFERENCE_VBOOT_2CRYPTO_H_ */
diff --git a/firmware/2lib/include/2return_codes.h b/firmware/2lib/include/2return_codes.h
index 2cffc56f..53e0102b 100644
--- a/firmware/2lib/include/2return_codes.h
+++ b/firmware/2lib/include/2return_codes.h
@@ -446,6 +446,9 @@ enum vb2_return_code {
 	/* TPM clear owner not implemented */
 	VB2_ERROR_EX_TPM_CLEAR_OWNER_UNIMPLEMENTED,
 
+	/* Hardware crypto engine doesn't support this algorithm (non-fatal) */
+	VB2_ERROR_EX_HWCRYPTO_UNSUPPORTED,
+
 
         /**********************************************************************
 	 * Errors generated by host library (non-firmware) start here.
diff --git a/firmware/2lib/include/2sha.h b/firmware/2lib/include/2sha.h
index 58792369..221d1856 100644
--- a/firmware/2lib/include/2sha.h
+++ b/firmware/2lib/include/2sha.h
@@ -78,6 +78,9 @@ struct vb2_digest_context {
 
 	/* Current hash algorithm */
 	enum vb2_hash_algorithm hash_alg;
+
+	/* 1 if digest is computed with vb2ex_hwcrypto routines, else 0 */
+	int using_hwcrypto;
 };
 
 /**
diff --git a/firmware/2lib/include/2struct.h b/firmware/2lib/include/2struct.h
index c0cd9071..5e2757b6 100644
--- a/firmware/2lib/include/2struct.h
+++ b/firmware/2lib/include/2struct.h
@@ -9,37 +9,7 @@
 #ifndef VBOOT_REFERENCE_VBOOT_2STRUCT_H_
 #define VBOOT_REFERENCE_VBOOT_2STRUCT_H_
 #include <stdint.h>
-
-/* Algorithm types for signatures */
-enum vb2_signature_algorithm {
-	/* Invalid or unsupported signature type */
-	VB2_SIG_INVALID = 0,
-
-	/*
-	 * No signature algorithm.  The digest is unsigned.  See
-	 * VB2_GUID_NONE_* above for key GUIDs to use with this algorithm.
-	 */
-	VB2_SIG_NONE = 1,
-
-	/* RSA algorithms of the given length in bits (1024-8192) */
-	VB2_SIG_RSA1024 = 2,  /* Warning!  This is likely to be deprecated! */
-	VB2_SIG_RSA2048 = 3,
-	VB2_SIG_RSA4096 = 4,
-	VB2_SIG_RSA8192 = 5,
-};
-
-/* Algorithm types for hash digests */
-enum vb2_hash_algorithm {
-	/* Invalid or unsupported digest type */
-	VB2_HASH_INVALID = 0,
-
-	/* SHA-1.  Warning: This is likely to be deprecated soon! */
-	VB2_HASH_SHA1 = 1,
-
-	/* SHA-256 and SHA-512 */
-	VB2_HASH_SHA256 = 2,
-	VB2_HASH_SHA512 = 3,
-};
+#include "2crypto.h"
 
 /*
  * Key block flags.