From 3c6050277b54f536e7effbe850dcc970a27387ab Mon Sep 17 00:00:00 2001 From: =?utf8?q?Andr=C3=A9=20Draszik?= Date: Tue, 3 Oct 2017 16:55:52 +0100 Subject: [PATCH] tpm: add tpm_get_random() MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Add a function to obtain random data from the TPM. Signed-off-by: André Draszik Added commit message, add cast to min() Signed-off-by: Simon Glass Acked-by: Simon Glass --- include/tpm.h | 12 ++++++++++++ lib/tpm.c | 43 +++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 55 insertions(+) diff --git a/include/tpm.h b/include/tpm.h index f88388f353..2a7528dd48 100644 --- a/include/tpm.h +++ b/include/tpm.h @@ -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 */ diff --git a/lib/tpm.c b/lib/tpm.c index 5659fa5e18..d21bbcfb11 100644 --- a/lib/tpm.c +++ b/lib/tpm.c @@ -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; +} -- 2.25.1