tpm: Add function to load keys via their parent's SHA1 hash

If we want to load a key into a TPM, we need to know the designated parent
key's handle, so that the TPM is able to insert the key at the correct place in
the key hierarchy.

However, if we want to load a key whose designated parent key we also
previously loaded ourselves, we first need to memorize this parent key's handle
(since the handles for the key are chosen at random when they are inserted into
the TPM). If we are, however, unable to do so, for example if the parent key is
loaded into the TPM during production, and its child key during the actual
boot, we must find a different mechanism to identify the parent key.

To solve this problem, we add a function that allows U-Boot to load a key into
the TPM using their designated parent key's SHA1 hash, and the corresponding
auth data.

Signed-off-by: Mario Six <mario.six@gdsys.cc>
Reviewed-by: Simon Glass <sjg@chromium.org>

1 files changed, 49 insertions, 0 deletions

diff --git a/cmd/tpm.c b/cmd/tpm.c
index 625fc43..91bd20d 100644
--- a/cmd/tpm.c
+++ b/cmd/tpm.c
@@ -592,6 +592,45 @@ static int do_tpm_oiap(cmd_tbl_t *cmdtp, int flag,
 	return report_return_code(err);
 }
 
+#ifdef CONFIG_TPM_LOAD_KEY_BY_SHA1
+static int do_tpm_load_key_by_sha1(cmd_tbl_t *cmdtp, int flag, int argc, char *
+				   const argv[])
+{
+	uint32_t parent_handle = 0;
+	uint32_t key_len, key_handle, err;
+	uint8_t usage_auth[DIGEST_LENGTH];
+	uint8_t parent_hash[DIGEST_LENGTH];
+	void *key;
+
+	if (argc < 5)
+		return CMD_RET_USAGE;
+
+	parse_byte_string(argv[1], parent_hash, NULL);
+	key = (void *)simple_strtoul(argv[2], NULL, 0);
+	key_len = simple_strtoul(argv[3], NULL, 0);
+	if (strlen(argv[4]) != 2 * DIGEST_LENGTH)
+		return CMD_RET_FAILURE;
+	parse_byte_string(argv[4], usage_auth, NULL);
+
+	err = tpm_find_key_sha1(usage_auth, parent_hash, &parent_handle);
+	if (err) {
+		printf("Could not find matching parent key (err = %d)\n", err);
+		return CMD_RET_FAILURE;
+	}
+
+	printf("Found parent key %08x\n", parent_handle);
+
+	err = tpm_load_key2_oiap(parent_handle, key, key_len, usage_auth,
+				 &key_handle);
+	if (!err) {
+		printf("Key handle is 0x%x\n", key_handle);
+		setenv_hex("key_handle", key_handle);
+	}
+
+	return report_return_code(err);
+}
+#endif /* CONFIG_TPM_LOAD_KEY_BY_SHA1 */
+
 static int do_tpm_load_key2_oiap(cmd_tbl_t *cmdtp, int flag,
 		int argc, char * const argv[])
 {
@@ -756,6 +795,10 @@ static cmd_tbl_t tpm_commands[] = {
 			 do_tpm_end_oiap, "", ""),
 	U_BOOT_CMD_MKENT(load_key2_oiap, 0, 1,
 			 do_tpm_load_key2_oiap, "", ""),
+#ifdef CONFIG_TPM_LOAD_KEY_BY_SHA1
+	U_BOOT_CMD_MKENT(load_key_by_sha1, 0, 1,
+			 do_tpm_load_key_by_sha1, "", ""),
+#endif /* CONFIG_TPM_LOAD_KEY_BY_SHA1 */
 	U_BOOT_CMD_MKENT(get_pub_key_oiap, 0, 1,
 			 do_tpm_get_pub_key_oiap, "", ""),
 #endif /* CONFIG_TPM_AUTH_SESSIONS */
@@ -826,6 +869,12 @@ U_BOOT_CMD(tpm, CONFIG_SYS_MAXARGS, 1, do_tpm,
 "    - loads a key data from memory address <key_addr>, <key_len> bytes\n"
 "      into TPM using the parent key <parent_handle> with authorization\n"
 "      <usage_auth> (20 bytes hex string).\n"
+#ifdef CONFIG_TPM_LOAD_KEY_BY_SHA1
+"  load_key_by_sha1 parent_hash key_addr key_len usage_auth\n"
+"    - loads a key data from memory address <key_addr>, <key_len> bytes\n"
+"      into TPM using the parent hash <parent_hash> (20 bytes hex string)\n"
+"      with authorization <usage_auth> (20 bytes hex string).\n"
+#endif /* CONFIG_TPM_LOAD_KEY_BY_SHA1 */
 "  get_pub_key_oiap key_handle usage_auth\n"
 "    - get the public key portion of a loaded key <key_handle> using\n"
 "      authorization <usage auth> (20 bytes hex string)\n"