tpm: add tpm_get_random()
Add a function to obtain random data from the TPM.
Signed-off-by: André Draszik <adraszik@tycoint.com>
Added commit message, add cast to min()
Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/lib/tpm.c b/lib/tpm.c
index 5659fa5..d21bbcf 100644
--- a/lib/tpm.c
+++ b/lib/tpm.c
@@ -1049,3 +1049,46 @@
#endif /* CONFIG_TPM_LOAD_KEY_BY_SHA1 */
#endif /* CONFIG_TPM_AUTH_SESSIONS */
+
+uint32_t tpm_get_random(void *data, uint32_t count)
+{
+ const uint8_t command[14] = {
+ 0x0, 0xc1, /* TPM_TAG */
+ 0x0, 0x0, 0x0, 0xe, /* parameter size */
+ 0x0, 0x0, 0x0, 0x46, /* TPM_COMMAND_CODE */
+ };
+ const size_t length_offset = 10;
+ const size_t data_size_offset = 10;
+ const size_t data_offset = 14;
+ uint8_t buf[COMMAND_BUFFER_SIZE], response[COMMAND_BUFFER_SIZE];
+ size_t response_length = sizeof(response);
+ uint32_t data_size;
+ uint8_t *out = data;
+
+ while (count > 0) {
+ uint32_t this_bytes = min((size_t)count,
+ sizeof (response) - data_offset);
+ uint32_t err;
+
+ if (pack_byte_string(buf, sizeof(buf), "sd",
+ 0, command, sizeof(command),
+ length_offset, this_bytes))
+ return TPM_LIB_ERROR;
+ err = tpm_sendrecv_command(buf, response, &response_length);
+ if (err)
+ return err;
+ if (unpack_byte_string(response, response_length, "d",
+ data_size_offset, &data_size))
+ return TPM_LIB_ERROR;
+ if (data_size > count)
+ return TPM_LIB_ERROR;
+ if (unpack_byte_string(response, response_length, "s",
+ data_offset, out, data_size))
+ return TPM_LIB_ERROR;
+
+ count -= data_size;
+ out += data_size;
+ }
+
+ return 0;
+}