rma: extract getting RMA Dev ID into a separate method

This CL extracts get_rma_device_id() that can be used by rma_auth and
other cr50 components.

BRANCH=none
BUG=b:136091350
TEST=Verify that RSU Device ID reported through vNVRAM that uses this
     new method mathes the same ID calculated from device ID in G2FA
     certificate. See CL:1677238 for the exact method.

Change-Id: I08f58dbd8f838f1e595601ec4532792acda62428
Signed-off-by: Andrey Pronin <apronin@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/1677237
Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>
(cherry picked from commit b7aba9d023d3c7273904860cb81bd7d3bd12e47f)
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/1684233
Tested-by: Vadim Bendebury <vbendeb@chromium.org>
Commit-Queue: Vadim Bendebury <vbendeb@chromium.org>
(cherry picked from commit 0b8bdaa0836febcdfdd2165cdca5114a9127bd6a)
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/1705742
(cherry picked from commit 2a555934de5c7927dce413d05c2f3b3e4dbbac70)

2 files changed, 32 insertions, 19 deletions

diff --git a/common/rma_auth.c b/common/rma_auth.c
index 60089bef6a..6a4430f8b8 100644
--- a/common/rma_auth.c
+++ b/common/rma_auth.c
@@ -167,6 +167,26 @@ static void p256_get_pub_key_and_secret(uint8_t pub_key[P256_NBYTES],
 }
 #endif
 
+void get_rma_device_id(uint8_t rma_device_id[RMA_DEVICE_ID_SIZE])
+{
+	uint8_t *chip_unique_id;
+	int chip_unique_id_size = system_get_chip_unique_id(&chip_unique_id);
+
+	/* Smaller unique chip IDs will fill rma_device_id only partially. */
+	if (chip_unique_id_size <= RMA_DEVICE_ID_SIZE) {
+		/* The size matches, let's just copy it as is. */
+		memcpy(rma_device_id, chip_unique_id, chip_unique_id_size);
+	} else {
+		/*
+		 * The unique chip ID size exceeds space allotted in
+		 * rma_challenge:device_id, let's use first few bytes of
+		 * its hash.
+		 */
+		hash_buffer(rma_device_id, RMA_DEVICE_ID_SIZE,
+			    chip_unique_id, chip_unique_id_size);
+	}
+}
+
 /**
  * Create a new RMA challenge/response
  *
@@ -179,10 +199,8 @@ int rma_create_challenge(void)
 	uint8_t secret[32];
 	struct rma_challenge c;
 	struct board_id bid;
-	uint8_t *device_id;
 	uint8_t *cptr = (uint8_t *)&c;
 	uint64_t t;
-	int unique_device_id_size;
 
 	/* Clear the current challenge and authcode, if any */
 	memset(challenge, 0, sizeof(challenge));
@@ -202,22 +220,7 @@ int rma_create_challenge(void)
 		return EC_ERROR_UNKNOWN;
 
 	memcpy(c.board_id, &bid.type, sizeof(c.board_id));
-
-	unique_device_id_size = system_get_chip_unique_id(&device_id);
-
-	/* Smaller unique device IDs will fill c.device_id only partially. */
-	if (unique_device_id_size <= sizeof(c.device_id)) {
-		/* The size matches, let's just copy it as is. */
-		memcpy(c.device_id, device_id, unique_device_id_size);
-	} else {
-		/*
-		 * The unique device ID size exceeds space allotted in
-		 * rma_challenge:device_id, let's use first few bytes of
-		 * its hash.
-		 */
-		hash_buffer(c.device_id, sizeof(c.device_id),
-			    device_id, unique_device_id_size);
-	}
+	get_rma_device_id(c.device_id);
 
 	/* Calculate a new ephemeral key pair and the shared secret. */
 #ifdef CONFIG_RMA_AUTH_USE_P256
diff --git a/include/rma_auth.h b/include/rma_auth.h
index 698f4a71e9..0a4d7c7e71 100644
--- a/include/rma_auth.h
+++ b/include/rma_auth.h
@@ -21,6 +21,8 @@
 #define RMA_CHALLENGE_GET_VERSION(vkidbyte) ((vkidbyte) >> 6)
 #define RMA_CHALLENGE_GET_KEY_ID(vkidbyte) ((vkidbyte) & 0x3f)
 
+#define RMA_DEVICE_ID_SIZE 8
+
 struct __packed rma_challenge {
 	/* Top 2 bits are protocol version; bottom 6 are server KeyID */
 	uint8_t version_key_id;
@@ -32,7 +34,7 @@ struct __packed rma_challenge {
 	uint8_t board_id[4];
 
 	/* Device ID */
-	uint8_t device_id[8];
+	uint8_t device_id[RMA_DEVICE_ID_SIZE];
 };
 
 /* Size of encoded challenge and response, and buffer sizes to hold them */
@@ -68,4 +70,12 @@ const char *rma_get_challenge(void);
  */
 int rma_try_authcode(const char *code);
 
+/**
+ * Get the device ID returned in RMA response.
+ *
+ * @param rma_device_id		Pointer to the buffer that will be filled with
+ * the ID. The buffer must be of size RMA_DEVICE_ID_SIZE.
+ */
+void get_rma_device_id(uint8_t rma_device_id[RMA_DEVICE_ID_SIZE]);
+
 #endif