[U-Boot] [PATCH 14/18] tpm: add TPM2_PCR_Read command support

[Miquel Raynal]

Add support for the TPM2_PCR_Read command.

Change the command file and the help accordingly.

Signed-off-by: Miquel Raynal <miquel.raynal at bootlin.com>
---
 cmd/tpm.c     | 23 ++++++++++++++---------
 include/tpm.h |  4 ++--
 lib/tpm.c     | 56 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 71 insertions(+), 12 deletions(-)

diff --git a/cmd/tpm.c b/cmd/tpm.c
index 3f284f0adf..8630571b1a 100644
--- a/cmd/tpm.c
+++ b/cmd/tpm.c
@@ -362,21 +362,25 @@ static int do_tpm_pcr_extend(cmd_tbl_t *cmdtp, int flag,
 }
 
 static int do_tpm_pcr_read(cmd_tbl_t *cmdtp, int flag,
-		int argc, char * const argv[])
+			   int argc, char * const argv[])
 {
-	uint32_t index, count, rc;
+	bool is_tpmv2 = (tpm_get_specification() == 2);
+	u32 index, rc;
+	unsigned int updates;
 	void *data;
 
-	if (argc != 4)
+	if (argc != 3)
 		return CMD_RET_USAGE;
+
 	index = simple_strtoul(argv[1], NULL, 0);
 	data = (void *)simple_strtoul(argv[2], NULL, 0);
-	count = simple_strtoul(argv[3], NULL, 0);
 
-	rc = tpm_pcr_read(index, data, count);
+	rc = tpm_pcr_read(index, data, &updates);
 	if (!rc) {
-		puts("Named PCR content:\n");
-		print_byte_string(data, count);
+		printf("Named PCR %u content (known updates: %d):\n", index,
+		       is_tpmv2 ? updates : -1);
+		print_byte_string(data, !is_tpmv2 ? TPM1_DIGEST_LENGTH :
+						    TPM2_DIGEST_LENGTH);
 	}
 
 	return report_return_code(rc);
@@ -1038,12 +1042,13 @@ U_BOOT_CMD(tpm, CONFIG_SYS_MAXARGS, 1, do_tpm,
 "    - Add a new measurement to a PCR.  Update PCR <index> with\n"
 "      <digest_in>. It must be a 20 byte digest for TPMv1 or a SHA256\n"
 "      digest of 32 bytes for TPMv2. Value of the PCR is given at <digest_out>\n"
-"  pcr_read index addr count\n"
-"    - Read <count> bytes from PCR <index> to memory address <addr>.\n"
 "  pcr_extend index <digest_in>\n"
 "    - Add a new measurement to a PCR.  Update PCR <index> with\n"
 "      <digest_in>. It must be a 20 byte digest for TPMv1 or a SHA256\n"
 "      digest of 32 bytes for TPMv2.\n"
+"  pcr_read <index> <digest_in>\n"
+"    - Read PCR <index> to memory address <digest_in> (20B with TPMv1, 64B with\n"
+"       TPMv2).\n"
 #ifdef CONFIG_TPM_AUTH_SESSIONS
 "Authorization Sessions\n"
 "  oiap\n"
diff --git a/include/tpm.h b/include/tpm.h
index b88ad4b2f4..2df2ea3c5b 100644
--- a/include/tpm.h
+++ b/include/tpm.h
@@ -571,10 +571,10 @@ int tpm2_pcr_extend(u32 index, const uint8_t *digest);
  *
  * @param index		index of the PCR
  * @param data		output buffer for contents of the named PCR
- * @param count		size of output buffer
+ * @param updates	optional out parameter: number of updates for this PCR
  * @return return code of the operation
  */
-uint32_t tpm_pcr_read(uint32_t index, void *data, size_t count);
+int tpm_pcr_read(u32 index, void *data, unsigned int *updates);
 
 /**
  * Issue a TSC_PhysicalPresence command.  TPM physical presence flag
diff --git a/lib/tpm.c b/lib/tpm.c
index e74530d538..925b21e2d6 100644
--- a/lib/tpm.c
+++ b/lib/tpm.c
@@ -568,7 +568,7 @@ int tpm2_pcr_extend(u32 index, const uint8_t *digest)
 	return tpm_sendrecv_command(command_v2,	NULL, NULL);
 }
 
-uint32_t tpm_pcr_read(uint32_t index, void *data, size_t count)
+int tpm1_pcr_read(u32 index, void *data)
 {
 	const uint8_t command[14] = {
 		0x0, 0xc1, 0x0, 0x0, 0x0, 0xe, 0x0, 0x0, 0x0, 0x15,
@@ -596,6 +596,60 @@ uint32_t tpm_pcr_read(uint32_t index, void *data, size_t count)
 	return 0;
 }
 
+int tpm2_pcr_read(u32 index, void *data, unsigned int *updates)
+{
+	u8 command_v2[COMMAND_BUFFER_SIZE] = {
+		STRINGIFY16(TPM2_ST_NO_SESSIONS), /* TAG */
+		STRINGIFY32(20),		/* Command size */
+		STRINGIFY32(TPM2_CC_PCR_READ),	/* Command code */
+
+		/* TPML_PCR_SELECTION */
+		STRINGIFY32(1),			/* Number of selections */
+		STRINGIFY16(TPM2_ALG_SHA256),	/* Algorithm of the hash */
+		3,				/* Array size for selection */
+		/* STRINGIFY32(bitmap(index) << 8) Selected PCR bitmap */
+	};
+	size_t response_len = COMMAND_BUFFER_SIZE;
+	u8 response[COMMAND_BUFFER_SIZE];
+	unsigned int counter = 0;
+	u8 pcr_sel[3] = {};
+	int ret;
+
+	if (!is_tpmv2)
+		return TPM_LIB_ERROR;
+
+	if (index >= 24)
+		return TPM_LIB_ERROR;
+
+	pcr_sel[index / 8] = BIT(index % 8);
+	if (pack_byte_string(command_v2, COMMAND_BUFFER_SIZE, "bbb",
+			     17, pcr_sel[0], 18, pcr_sel[1], 19, pcr_sel[2]))
+		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_LENGTH, data,
+			       TPM2_DIGEST_LENGTH))
+		return TPM_LIB_ERROR;
+
+	if (updates)
+		*updates = counter;
+
+	return 0;
+}
+
+int tpm_pcr_read(u32 index, void *data, unsigned int *updates)
+{
+	if (!is_tpmv2)
+		return tpm1_pcr_read(index, data);
+	else
+		return tpm2_pcr_read(index, data, updates);
+}
+
 uint32_t tpm_tsc_physical_presence(uint16_t presence)
 {
 	const uint8_t command[12] = {
-- 
2.14.1