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tpm: add tpm_get_random()

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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>
This commit is contained in:
André Draszik 2017-10-03 16:55:52 +01:00 • committed by Simon Glass
parent e8155dfe33
commit 3c6050277b
2 changed files with 55 additions and 0 deletions
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12
include/tpm.h
View file

@ -651,4 +651,16 @@ uint32_t tpm_flush_specific(uint32_t key_handle, uint32_t resource_type);
uint32_t tpm_find_key_sha1(const uint8_t auth[20], const uint8_t
pubkey_digest[20], uint32_t *handle);
#endif /* CONFIG_TPM_LOAD_KEY_BY_SHA1 */
/**
* Read random bytes from the TPM RNG. The implementation deals with the fact
* that the TPM may legally return fewer bytes than requested by retrying
* until @p count bytes have been received.
*
* @param data output buffer for the random bytes
* @param count size of output buffer
* @return return code of the operation
*/
uint32_t tpm_get_random(void *data, uint32_t count);
#endif /* __TPM_H */

43
lib/tpm.c
View file

@ -1049,3 +1049,46 @@ uint32_t tpm_find_key_sha1(const uint8_t auth[20], const uint8_t
#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;
}