tutorial: root_of_trust: add milestone one for encryption service

Author: pqcfox

examples/tutorials/root_of_trust/encryption_service_milestone_one/Makefile

@@ -0,0 +1,13 @@
+# Makefile for user application
+
+# Specify this directory relative to the current application.
+TOCK_USERLAND_BASE_DIR = ../../../../
+
+PACKAGE_NAME = org.tockos.tutorials.attestation.encryption
+
+# Which files to compile.
+C_SRCS := $(wildcard *.c)
+
+# Include userland master makefile. Contains rules and flags for actually
+# building the application.
+include $(TOCK_USERLAND_BASE_DIR)/AppMakefile.mk

examples/tutorials/root_of_trust/encryption_service_milestone_one/README.md

@@ -0,0 +1,15 @@
+Hardware Root of Trust (HWRoT) Demo Encryption Service Application
+------------------------------------------------------------------
+
+This application implements a basic UART encryption service for a mock hardware
+root of trust (HWRoT) which inputs user-provided plaintext and encrypts it using
+a fixed key stored in a kernel driver, returning the ciphertext to the user. 
+
+This is part of a tutorial which improves the application in multiple steps. A
+writeup for the tutorial is available at https://book.tockos.org/.
+
+Specific abilities of this version:
+
+* Allows logging to screen over IPC
+* Does NOT allow prompting for plaintext over returning results in hex over UART
+* Does NOT allow for encryping user-provided plaintext using an encryption oracle driver

examples/tutorials/root_of_trust/encryption_service_milestone_one/main.c

@@ -0,0 +1,96 @@
+#include "libtock/tock.h"
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <libtock-sync/interface/console.h>
+#include <libtock/kernel/ipc.h>
+
+#define LOG_WIDTH      32
+
+bool started          = false;
+bool log_done         = false;
+size_t screen_service = -1;
+char log_buf[LOG_WIDTH] __attribute__((aligned(LOG_WIDTH)));
+
+const char SCREEN_SERVICE_NAME[] = "org.tockos.tutorials.attestation.screen";
+
+static void ipc_callback(__attribute__ ((unused)) int   pid,
+                         __attribute__ ((unused)) int   len,
+                         __attribute__ ((unused)) int   arg2,
+                         __attribute__ ((unused)) void* ud) {
+  started = true;
+}
+
+static void log_done_callback(__attribute__ ((unused)) int   pid,
+                              __attribute__ ((unused)) int   len,
+                              __attribute__ ((unused)) int   arg2,
+                              __attribute__ ((unused)) void* ud) {
+  log_done = true;
+}
+
+static void wait_for_start(void) {
+  // Register an IPC callback and wait for it to be called by the
+  // screen app based on the user's app selection.
+  ipc_register_service_callback("org.tockos.tutorials.attestation.encryption", ipc_callback,
+                                NULL);
+  yield_for(&started);
+}
+
+static int setup_logging() {
+  returncode_t ret;
+
+  // Find the PID of the screen logging service
+  ret = ipc_discover(SCREEN_SERVICE_NAME, &screen_service);
+  if (ret != RETURNCODE_SUCCESS) {
+    printf("Screen logging service not found.\n");
+    return ret;
+  }
+
+  // Set up a callback and share so we can supply log messages
+  // and know when they've been completely logged.
+  ipc_register_client_callback(screen_service, log_done_callback, NULL);
+  ipc_share(screen_service, log_buf, LOG_WIDTH);
+
+  return 0;
+}
+
+static int log_to_screen(const char* message) {
+  returncode_t ret;
+
+  // Copy up to the log buffer's size of the message, with room for a null byte.
+  uint16_t len = strnlen(message, sizeof(log_buf) - 1);
+  memcpy(log_buf, message, len);
+
+  // Add the null byte.
+  log_buf[len] = '\0';
+
+  // Start the logging process.
+  ret = ipc_notify_service(screen_service);
+  if (ret != RETURNCODE_SUCCESS) {
+    printf("Failed to request a log to screen.\n");
+    return ret;
+  }
+
+  // Wait for the log to complete.
+  yield_for(&log_done);
+  log_done = false;
+
+  return 0;
+}
+
+int main(void) {
+  // Wait to receive the signal to start from the app selector.
+  wait_for_start();
+
+  // Set up logging service.
+  setup_logging();
+
+  // Test logging to screen over IPC.
+  char message_buf[32];
+  for (int i = 0; i < 10; i++) {
+    sprintf(message_buf, "Test message #%i...", i);
+    log_to_screen(message_buf);
+  }
+
+  return 0;
+}

examples/tutorials/root_of_trust/encryption_service_starter/README.md

@@ -2,7 +2,8 @@ Hardware Root of Trust (HWRoT) Demo Encryption Service Application
 ------------------------------------------------------------------
 
 This application implements a basic UART encryption service for a mock hardware
-root of trust (HWRoT) which inputs user-provided 
+root of trust (HWRoT) which inputs user-provided plaintext and encrypts it using
+a fixed key stored in a kernel driver, returning the ciphertext to the user. 
 
 This is part of a tutorial which improves the application in multiple steps. A
 writeup for the tutorial is available at https://book.tockos.org/.