tpm: add TPM2_PCR_Read command support

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>
Reviewed-by: Tom Rini <trini@konsulko.com>

diff --git a/cmd/tpm-v2.c b/cmd/tpm-v2.c
index 0a7a5c807412789d876126d1a78f9e61e6beeb7c..ea2da97e2a7399ce13bda117b4951527248af745 100644 (file)
--- 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 25bb15af393f7dd20c8543186a3c90bb55194909..2b8600a185cadf7d6e6de39d94552f8e641ac8ad 100644 (file)
--- 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 476b4ee0d083bd4f136e6a9c840a7ab0826ba343..7d3834c0e4057364016bafcb0e0627938a9ef232 100644 (file)
--- 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;
+}