tutorials: root_of_trust: add 'suspicious' SRAM dump demo application

Author: pqcfox

examples/tutorials/root_of_trust/suspicious_service/Makefile

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+# Makefile for user application
+
+# Specify this directory relative to the current application.
+TOCK_USERLAND_BASE_DIR = ../../../../
+
+PACKAGE_NAME = org.tockos.tutorials.attestation.suspicious
+
+# 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/suspicious_service/README.md

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+Hardware Root of Trust (HWRoT) "Suspicious" Userspace Attack Application
+------------------------------------------------------------------------
+
+This application implements a basic SRAM dump attack on the encryption servicde
+application in the Hardware Root of Trust demo.
+
+This is part of a tutorial which improves the encryption application in multiple
+steps and mounts multiple attacks on it. A writeup for the tutorial is available
+at https://book.tockos.org/.
+
+Specific abilities of this version (assuming `#define` constants set correctly):
+
+* Allows dumping application's own SRAM
+* Allows attempting dumping of the encryption service application's SRAM 

examples/tutorials/root_of_trust/suspicious_service/main.c

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+#include "libtock/tock.h"
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <libtock/kernel/ipc.h>
+
+#define ENCRYPTION_SRAM_START  0x2000A000
+#define ENCRYPTION_SRAM_END    0x2000BFFF
+#define SELF_SRAM_START        0x2000C000
+#define SELF_SRAM_END          0x2000CFFF
+
+#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.suspicious", 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;
+}
+
+static void dump_memory(uint32_t *start, uint32_t *end, const char *label) {
+  for (uint32_t *addr = start; addr < end; addr++) {
+    printf("[%s] %p: %08lX\n", label, addr, *addr);
+  }
+}
+
+int main(void) {
+  returncode_t ret;
+
+  // Wait to receive the signal to start from the app selector.
+  wait_for_start();
+
+  // Set up logging service.
+  ret = setup_logging();
+  if (ret < 0) {
+    printf("ERROR: cannot set up logging\n");
+  }
+
+  // Dump our own SRAM.
+  ret = log_to_screen("Dumping own SRAM...");
+  if (ret < 0) {
+    printf("ERROR: cannot log to screen\n");
+  }
+  dump_memory((uint32_t *)SELF_SRAM_START, (uint32_t *)SELF_SRAM_END, "SELF");
+  ret = log_to_screen("Dumping own SRAM complete!");
+  if (ret < 0) {
+    printf("ERROR: cannot log to screen\n");
+  }
+
+  // Dump the encryption service SRAM.
+  ret = log_to_screen("Dumping encryption SRAM...");
+  if (ret < 0) {
+    printf("ERROR: cannot log to screen\n");
+  }
+  dump_memory((uint32_t *)ENCRYPTION_SRAM_START, (uint32_t *)ENCRYPTION_SRAM_END, "ENCRYPTION");
+  ret = log_to_screen("Dumping encryption SRAM complete!");
+  if (ret < 0) {
+    printf("ERROR: cannot log to screen\n");
+  }
+  
+  return 0;
+}