[U-Boot] [PATCH v4 20/32] tpm: add TPM2_PCR_Read command support

Miquel Raynal
2018-05-15T09:57:16Z

Add support for the TPM2_PCR_Read command.

Change the command file and the help accordingly.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
---
cmd/tpm-v2.c | 43 +++++++++++++++++++++++++++++++++++++++++++
include/tpm-v2.h | 13 +++++++++++++
lib/tpm-v2.c | 42 ++++++++++++++++++++++++++++++++++++++++++
3 files changed, 98 insertions(+)

diff --git a/cmd/tpm-v2.c b/cmd/tpm-v2.c
index df6cd6919c..49c22aaeaa 100644
--- a/cmd/tpm-v2.c
+++ b/cmd/tpm-v2.c
@@ -106,6 +106,44 @@ static int do_tpm2_pcr_extend(cmd_tbl_t *cmdtp, int flag, int argc,
return report_return_code(rc);
}

+static int do_tpm_pcr_read(cmd_tbl_t *cmdtp, int flag, int argc,
+ char * const argv[])
+{
+ struct udevice *dev;
+ struct tpm_chip_priv *priv;
+ u32 index, rc;
+ unsigned int updates;
+ void *data;
+ int ret;
+
+ if (argc != 3)
+ return CMD_RET_USAGE;
+
+ ret = uclass_first_device_err(UCLASS_TPM, &dev);
+ if (ret)
+ return ret;
+
+ priv = dev_get_uclass_priv(dev);
+ if (!priv)
+ return -EINVAL;
+
+ index = simple_strtoul(argv[1], NULL, 0);
+ if (index >= priv->pcr_count)
+ return -EINVAL;
+
+ data = map_sysmem(simple_strtoul(argv[2], NULL, 0), 0);
+
+ rc = tpm2_pcr_read(index, priv->pcr_select_min, data, &updates);
+ if (!rc) {
+ printf("PCR #%u content (%d known updates):\n", index, updates);
+ print_byte_string(data, TPM2_DIGEST_LEN);
+ }
+
+ unmap_sysmem(data);
+
+ return report_return_code(rc);
+}
+
static cmd_tbl_t tpm2_commands[] = {
U_BOOT_CMD_MKENT(info, 0, 1, do_tpm_info, "", ""),
U_BOOT_CMD_MKENT(init, 0, 1, do_tpm_init, "", ""),
@@ -113,6 +151,7 @@ static cmd_tbl_t tpm2_commands[] = {
U_BOOT_CMD_MKENT(self_test, 0, 1, do_tpm2_self_test, "", ""),
U_BOOT_CMD_MKENT(clear, 0, 1, do_tpm2_clear, "", ""),
U_BOOT_CMD_MKENT(pcr_extend, 0, 1, do_tpm2_pcr_extend, "", ""),
+ U_BOOT_CMD_MKENT(pcr_read, 0, 1, do_tpm_pcr_read, "", ""),
};

cmd_tbl_t *get_tpm_commands(unsigned int *size)
@@ -148,4 +187,8 @@ U_BOOT_CMD(tpm, CONFIG_SYS_MAXARGS, 1, do_tpm, "Issue a TPMv2.x command",
" Extend PCR #<pcr> with digest at <digest_addr>.\n"
" <pcr>: index of the PCR\n"
" <digest_addr>: address of a 32-byte SHA256 digest\n"
+"pcr_read <pcr> <digest_addr>\n"
+" Read PCR #<pcr> to memory address <digest_addr>.\n"
+" <pcr>: index of the PCR\n"
+" <digest_addr>: address to store the a 32-byte SHA256 digest\n"
);
diff --git a/include/tpm-v2.h b/include/tpm-v2.h
index 0706a925ce..b9f36b22ba 100644
--- a/include/tpm-v2.h
+++ b/include/tpm-v2.h
@@ -164,4 +164,17 @@ u32 tpm2_clear(u32 handle, const char *pw, const ssize_t pw_sz);
*/
u32 tpm2_pcr_extend(u32 index, const uint8_t *digest);

+/**
+ * Issue a TPM2_PCR_Read command.
+ *
+ * @idx Index of the PCR
+ * @idx_min_sz Minimum size in bytes of the pcrSelect array
+ * @data Output buffer for contents of the named PCR
+ * @updates Optional out parameter: number of updates for this PCR
+ *
+ * @return code of the operation
+ */
+u32 tpm2_pcr_read(u32 idx, unsigned int idx_min_sz, void *data,
+ unsigned int *updates);
+
#endif /* __TPM_V2_H */
diff --git a/lib/tpm-v2.c b/lib/tpm-v2.c
index 2696f8145d..a1f1dbc3d6 100644
--- a/lib/tpm-v2.c
+++ b/lib/tpm-v2.c
@@ -115,3 +115,45 @@ u32 tpm2_pcr_extend(u32 index, const uint8_t *digest)

return tpm_sendrecv_command(command_v2, NULL, NULL);
}
+
+u32 tpm2_pcr_read(u32 idx, unsigned int idx_min_sz, void *data,
+ unsigned int *updates)
+{
+ u8 idx_array_sz = max(idx_min_sz, DIV_ROUND_UP(idx, 8));
+ u8 command_v2[COMMAND_BUFFER_SIZE] = {
+ tpm_u16(TPM2_ST_NO_SESSIONS), /* TAG */
+ tpm_u32(17 + idx_array_sz), /* Length */
+ tpm_u32(TPM2_CC_PCR_READ), /* Command code */
+
+ /* TPML_PCR_SELECTION */
+ tpm_u32(1), /* Number of selections */
+ tpm_u16(TPM2_ALG_SHA256), /* Algorithm of the hash */
+ idx_array_sz, /* Array size for selection */
+ /* bitmap(idx) Selected PCR bitmap */
+ };
+ size_t response_len = COMMAND_BUFFER_SIZE;
+ u8 response[COMMAND_BUFFER_SIZE];
+ unsigned int pcr_sel_idx = idx / 8;
+ u8 pcr_sel_bit = BIT(idx % 8);
+ unsigned int counter = 0;
+ int ret;
+
+ if (pack_byte_string(command_v2, COMMAND_BUFFER_SIZE, "b",
+ 17 + pcr_sel_idx, pcr_sel_bit))
+ return TPM_LIB_ERROR;
+
+ ret = tpm_sendrecv_command(command_v2, response, &response_len);
+ if (ret)
+ return ret;
+
+ if (unpack_byte_string(response, response_len, "ds",
+ 10, &counter,
+ response_len - TPM2_DIGEST_LEN, data,
+ TPM2_DIGEST_LEN))
+ return TPM_LIB_ERROR;
+
+ if (updates)
+ *updates = counter;
+
+ return 0;
+}
--
2.14.1