tpm: add TPM2_GetRandom command support

Add support for TPM2 GetRandom command

Signed-off-by: Dhananjay Phadke <dphadke@linux.microsoft.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

2 files changed, 57 insertions, 0 deletions

diff --git a/include/tpm-v2.h b/include/tpm-v2.h
index d53d2e4..f6c045d 100644
--- a/include/tpm-v2.h
+++ b/include/tpm-v2.h
@@ -70,6 +70,7 @@ enum tpm2_handles {
  * @TPM2_CC_DAM_RESET: TPM2_DictionaryAttackLockReset().
  * @TPM2_CC_DAM_PARAMETERS: TPM2_DictionaryAttackParameters().
  * @TPM2_CC_GET_CAPABILITY: TPM2_GetCapibility().
+ * @TPM2_CC_GET_RANDOM: TPM2_GetRandom().
  * @TPM2_CC_PCR_READ: TPM2_PCR_Read().
  * @TPM2_CC_PCR_EXTEND: TPM2_PCR_Extend().
  * @TPM2_CC_PCR_SETAUTHVAL: TPM2_PCR_SetAuthValue().
@@ -85,6 +86,7 @@ enum tpm2_command_codes {
 	TPM2_CC_DAM_PARAMETERS	= 0x013A,
 	TPM2_CC_NV_READ         = 0x014E,
 	TPM2_CC_GET_CAPABILITY	= 0x017A,
+	TPM2_CC_GET_RANDOM      = 0x017B,
 	TPM2_CC_PCR_READ	= 0x017E,
 	TPM2_CC_PCR_EXTEND	= 0x0182,
 	TPM2_CC_PCR_SETAUTHVAL	= 0x0183,
@@ -339,4 +341,15 @@ u32 tpm2_pcr_setauthvalue(struct udevice *dev, const char *pw,
 			  const ssize_t pw_sz, u32 index, const char *key,
 			  const ssize_t key_sz);
 
+/**
+ * Issue a TPM2_GetRandom command.
+ *
+ * @dev		TPM device
+ * @param data		output buffer for the random bytes
+ * @param count		size of output buffer
+ *
+ * @return return code of the operation
+ */
+u32 tpm2_get_random(struct udevice *dev, void *data, u32 count);
+
 #endif /* __TPM_V2_H */
diff --git a/lib/tpm-v2.c b/lib/tpm-v2.c
index 5a039f6..a4c352e 100644
--- a/lib/tpm-v2.c
+++ b/lib/tpm-v2.c
@@ -422,3 +422,47 @@ u32 tpm2_pcr_setauthvalue(struct udevice *dev, const char *pw,
 
 	return tpm_sendrecv_command(dev, command_v2, NULL, NULL);
 }
+
+u32 tpm2_get_random(struct udevice *dev, void *data, u32 count)
+{
+	const u8 command_v2[10] = {
+		tpm_u16(TPM2_ST_NO_SESSIONS),
+		tpm_u32(12),
+		tpm_u32(TPM2_CC_GET_RANDOM),
+	};
+	u8 buf[COMMAND_BUFFER_SIZE], response[COMMAND_BUFFER_SIZE];
+
+	const size_t data_size_offset = 10;
+	const size_t data_offset = 12;
+	size_t response_length = sizeof(response);
+	u32 data_size;
+	u8 *out = data;
+
+	while (count > 0) {
+		u32 this_bytes = min((size_t)count,
+				     sizeof(response) - data_offset);
+		u32 err;
+
+		if (pack_byte_string(buf, sizeof(buf), "sw",
+				     0, command_v2, sizeof(command_v2),
+				     sizeof(command_v2), this_bytes))
+			return TPM_LIB_ERROR;
+		err = tpm_sendrecv_command(dev, buf, response,
+					   &response_length);
+		if (err)
+			return err;
+		if (unpack_byte_string(response, response_length, "w",
+				       data_size_offset, &data_size))
+			return TPM_LIB_ERROR;
+		if (data_size > this_bytes)
+			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;
+}