Added kill switch. (#25)

CMakeLists.txt

@@ -12,10 +12,16 @@ set(CMAKE_RUNTIME_OUTPUT_DIRECTORY build)
 
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-unused-result -Wreturn-type")
 
+#-------Bootstrap contract-------
+
 add_executable(bootstrap_contract
     bootstrap-contract/bootstrap_contract.cpp
 )
 
+#-------Sashimono Agent-------
+
+add_subdirectory(src/killswitch)
+
 add_executable(sagent
     src/conf.cpp
     src/comm/comm_handler.cpp
@@ -32,6 +38,7 @@ add_executable(sagent
 )
 
 target_link_libraries(sagent
+    killswitch
     libsodium.a
     libboost_stacktrace_backtrace.a
     sqlite3

src/killswitch/CMakeLists.txt

@@ -0,0 +1,38 @@
+###
+# Compile-time timestamping library
+# 
+
+# Adapted from https://github.com/kraiskil/cmake_timestamp
+# This is only used for the Sashimono Agent kill switch.
+
+#CMake 3.12 made using OBJECT libraries much nicer, so we use that.
+cmake_minimum_required(VERSION 3.12)
+
+# Set CMake variable BUILD_TIME to 'now'. This 'now' is the time
+# when CMake is run, not when the target builder (e.g. make) is run.
+string(TIMESTAMP BUILD_TIME "%s" UTC)
+
+# Compile the library that contains the global variables
+add_library( killswitch OBJECT killswitch.c)
+target_compile_definitions(
+	killswitch
+	PRIVATE -DBUILD_TIME="${BUILD_TIME}"
+)
+target_include_directories( killswitch
+	PUBLIC
+		$<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>
+)
+
+#Add a dummy target that removes the CMake variable BUILD_TIME from CMake's cache.
+#this forces CMake to be-rerun when we hit this target.
+add_custom_target(
+	clear_cache
+	COMMAND ${CMAKE_COMMAND} -U BUILD_TIME ${CMAKE_BINARY_DIR}
+)
+
+#Have the cache clearing be run before trying to build the killswitch library.
+#This (I think) is the same as a PRE_BUILD custom_command. But PRE_BUILD is
+#available for VS generators only, on others it is synonymous to PRE_LINK,
+#i.e. "post compile"
+add_dependencies(killswitch clear_cache)
+

src/killswitch/killswitch.c

@@ -0,0 +1,25 @@
+#include <stdint.h>
+#include <stdbool.h>
+#include <stdlib.h>
+
+// BUILD_TIME symbol is populated via CMAKE build.
+const char *build_time_sec_str = BUILD_TIME;
+uint64_t MAX_LIMIT_SEC = 60 * 24 * 3600;
+uint64_t build_time_sec = 0;
+
+/**
+ * Returns true if kill switch is activated (allowed time has expired).
+ * Otherwise returns false (can keep using Sashimono Agent).
+ * @param epoch_ms Current time in epoch milliseconds.
+ */
+bool kill_switch(const uint64_t epoch_ms)
+{
+    if (build_time_sec == 0)
+    {
+        char *eptr;
+        build_time_sec = strtoull(build_time_sec_str, &eptr, 10);
+    }
+
+    const uint64_t epoch_sec = epoch_ms / 1000;
+    return !(epoch_sec > build_time_sec && (epoch_sec - build_time_sec) <= MAX_LIMIT_SEC);
+}

src/killswitch/killswitch.h

@@ -0,0 +1,18 @@
+#ifndef KILLSWITCH_H
+#define KILLSWITCH_H
+
+#include <stdint.h>
+#include <stdbool.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+bool kill_switch(const uint64_t epoch_ms);
+
+#ifdef __cplusplus
+};
+#endif
+
+#endif
+

src/killswitch/readme.txt

@@ -0,0 +1,4 @@
+Based on https://github.com/kraiskil/cmake_timestamp
+
+This whole folder exists to get the CMAKE compile/link time into the binary so we can perform
+Sashimono Agent time-based kill switch check. This folder must be removed when we no longer need the kill switch.

src/main.cpp

@@ -10,6 +10,8 @@
 #include "crypto.hpp"
 #include "hp_manager.hpp"
 #include "version.hpp"
+#include "util/util.hpp"
+#include "killswitch/killswitch.h"
 
 #define PARSE_ERROR                                          \
     {                                                        \
@@ -139,6 +141,12 @@ int main(int argc, char **argv)
     }
     else if (conf::ctx.command == "run")
     {
+        if (kill_switch(util::get_epoch_milliseconds()))
+        {
+            std::cerr << "Sashimono Agent usage limit failure.\n";
+            return -1;
+        }
+
         if (conf::init() != 0)
             return -1;