vboot2: Add code and tests for verifying vb2_fw_preamble2

This is the last low-level data structure verification code for the
new data structures.  Subsequent changes are the next level up the
food chain.

BUG=chromium:423882
BRANCH=none
TEST=VBOOT2=1 make runtests

Change-Id: I2e45106c27447eb624c1ed562e40b98088249742
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/228360
Reviewed-by: Daisuke Nojiri <dnojiri@chromium.org>

4 files changed, 89 insertions, 5 deletions

diff --git a/firmware/2lib/2common2.c b/firmware/2lib/2common2.c
index 1dcf53d1..099f7c1f 100644
--- a/firmware/2lib/2common2.c
+++ b/firmware/2lib/2common2.c
@@ -366,3 +366,73 @@ int vb2_verify_keyblock2(struct vb2_keyblock2 *block,
 	/* If we're still here, no signature matched the key GUID */
 	return VB2_ERROR_KEYBLOCK_SIG_GUID;
 }
+
+int vb2_verify_fw_preamble2(struct vb2_fw_preamble2 *preamble,
+			    uint32_t size,
+			    const struct vb2_public_key *key,
+			    const struct vb2_workbuf *wb)
+{
+	struct vb2_signature2 *sig;
+	uint32_t min_offset = 0, hash_offset;
+	int rv, i;
+
+	/* Check magic number */
+	if (preamble->c.magic != VB2_MAGIC_FW_PREAMBLE2)
+		return VB2_ERROR_PREAMBLE_MAGIC;
+
+	/* Make sure common header is good */
+	rv = vb2_verify_common_header(preamble, size);
+	if (rv)
+		return rv;
+
+	/*
+	 * Check for compatible version.  No need to check minor version, since
+	 * that's compatible across readers matching the major version, and we
+	 * haven't added any new fields.
+	 */
+	if (preamble->c.struct_version_major != VB2_FW_PREAMBLE2_VERSION_MAJOR)
+		return VB2_ERROR_PREAMBLE_HEADER_VERSION;
+
+	/* Make sure header is big enough */
+	if (preamble->c.fixed_size < sizeof(*preamble))
+		return VB2_ERROR_PREAMBLE_SIZE;
+
+	/* Make sure all hash signatures are inside */
+	hash_offset = preamble->hash_offset;
+	for (i = 0; i < preamble->hash_count; i++, hash_offset = min_offset) {
+		/* Make sure signature is inside preamble */
+		rv = vb2_verify_common_subobject(preamble, &min_offset,
+						 hash_offset);
+		if (rv)
+			return rv;
+
+		sig = (struct vb2_signature2 *)
+			((uint8_t *)preamble + hash_offset);
+
+		/* Verify the signature integrity */
+		rv = vb2_verify_signature2(
+				sig, preamble->c.total_size - hash_offset);
+		if (rv)
+			return rv;
+
+		/* Hashes must all be unsigned */
+		if (sig->sig_alg != VB2_SIG_NONE)
+			return VB2_ERROR_PREAMBLE_HASH_SIGNED;
+	}
+
+	/* Make sure signature is inside preamble */
+	rv = vb2_verify_common_subobject(preamble, &min_offset,
+					 preamble->sig_offset);
+	if (rv)
+		return rv;
+
+	/* Verify preamble signature */
+	sig = (struct vb2_signature2 *)((uint8_t *)preamble +
+					preamble->sig_offset);
+
+	rv = vb2_verify_data2(preamble, preamble->sig_offset, sig, key, wb);
+	if (rv)
+		return rv;
+
+	return VB2_SUCCESS;
+}
diff --git a/firmware/2lib/include/2common.h b/firmware/2lib/include/2common.h
index 0f7012cb..d26ccfce 100644
--- a/firmware/2lib/include/2common.h
+++ b/firmware/2lib/include/2common.h
@@ -410,7 +410,10 @@ int vb2_verify_keyblock2(struct vb2_keyblock2 *block,
 			 const struct vb2_public_key *key,
 			 const struct vb2_workbuf *wb);
 
-/* Size of work buffer sufficient for vb2_verify_fw_preamble() worst case */
+/*
+ * Size of work buffer sufficient for vb2_verify_fw_preamble() or
+ * vb2_verify_fw_preamble2() worst case.
+ */
 #define VB2_VERIFY_FIRMWARE_PREAMBLE_WORKBUF_BYTES VB2_VERIFY_DATA_WORKBUF_BYTES
 
 /**
@@ -429,4 +432,9 @@ int vb2_verify_fw_preamble(struct vb2_fw_preamble *preamble,
 			   const struct vb2_public_key *key,
 			   const struct vb2_workbuf *wb);
 
+int vb2_verify_fw_preamble2(struct vb2_fw_preamble2 *preamble,
+			    uint32_t size,
+			    const struct vb2_public_key *key,
+			    const struct vb2_workbuf *wb);
+
 #endif  /* VBOOT_REFERENCE_VBOOT_2COMMON_H_ */
diff --git a/firmware/2lib/include/2return_codes.h b/firmware/2lib/include/2return_codes.h
index 054655ee..4ff84468 100644
--- a/firmware/2lib/include/2return_codes.h
+++ b/firmware/2lib/include/2return_codes.h
@@ -302,6 +302,12 @@ enum vb2_return_code {
 	/* Kernel subkey outside preamble */
 	VB2_ERROR_PREAMBLE_KERNEL_SUBKEY_OUTSIDE,
 
+	/* Bad magic number */
+	VB2_ERROR_PREAMBLE_MAGIC,
+
+	/* Hash is signed */
+	VB2_ERROR_PREAMBLE_HASH_SIGNED,
+
         /**********************************************************************
 	 * Misc higher-level code errors
 	 */
diff --git a/firmware/2lib/include/2struct.h b/firmware/2lib/include/2struct.h
index e988f3f9..3f208325 100644
--- a/firmware/2lib/include/2struct.h
+++ b/firmware/2lib/include/2struct.h
@@ -491,9 +491,9 @@ struct vb2_keyblock2 {
 #define EXPECTED_VB2_KEYBLOCK2_SIZE (EXPECTED_VB2_STRUCT_COMMON_SIZE + 16)
 
 
-/* Current version of vb2_preamble2 struct */
-#define VB2_PREAMBLE2_VERSION_MAJOR 3
-#define VB2_PREAMBLE2_VERSION_MINOR 0
+/* Current version of vb2_fw_preamble2 struct */
+#define VB2_FW_PREAMBLE2_VERSION_MAJOR 3
+#define VB2_FW_PREAMBLE2_VERSION_MINOR 0
 
 /*
  * Firmware preamble
@@ -501,7 +501,7 @@ struct vb2_keyblock2 {
  * The preamble data must be arranged like this:
  *     1) vb2_fw_preamble2 header struct h
  *     2) Preamble description (pointed to by h.c.fixed_size)
- *     3) Hash table (pointed to by h.hash_table_offset)
+ *     3) Hashes (pointed to by h.hash_offset)
  *     4) Signature (pointed to by h.sig_offset)
  *
  * The signature 4) must cover all the data from 1), 2), 3).