Hyundai checksum (commaai#540)

* 3/5 hyundai checksums done

* cleanup

* these 3 should be universal across all hkg

* fix tests

* fix misra

board/safety/safety_hyundai.h

@@ -10,11 +10,11 @@ const CanMsg HYUNDAI_TX_MSGS[] = {{832, 0, 8}, {1265, 0, 4}, {1157, 0, 4}};
 
 // TODO: do checksum checks
 AddrCheckStruct hyundai_rx_checks[] = {
-  {.msg = {{608, 0, 8}}, .max_counter = 3U, .expected_timestep = 10000U},
+  {.msg = {{608, 0, 8}}, .check_checksum = true, .max_counter = 3U, .expected_timestep = 10000U},
   {.msg = {{897, 0, 8}}, .max_counter = 255U, .expected_timestep = 10000U},
   {.msg = {{902, 0, 8}}, .max_counter = 15U,  .expected_timestep = 10000U},
-  {.msg = {{916, 0, 8}}, .max_counter = 7U, .expected_timestep = 10000U},
-  {.msg = {{1057, 0, 8}}, .max_counter = 15U, .expected_timestep = 20000U},
+  {.msg = {{916, 0, 8}}, .check_checksum = true, .max_counter = 7U, .expected_timestep = 10000U},
+  {.msg = {{1057, 0, 8}}, .check_checksum = true, .max_counter = 15U, .expected_timestep = 20000U},
 };
 const int HYUNDAI_RX_CHECK_LEN = sizeof(hyundai_rx_checks) / sizeof(hyundai_rx_checks[0]);
 
@@ -38,10 +38,43 @@ static uint8_t hyundai_get_counter(CAN_FIFOMailBox_TypeDef *to_push) {
   return cnt;
 }
 
+static uint8_t hyundai_get_checksum(CAN_FIFOMailBox_TypeDef *to_push) {
+  int addr = GET_ADDR(to_push);
+
+  uint8_t chksum;
+  if (addr == 608) {
+    chksum = GET_BYTE(to_push, 7) & 0xF;
+  } else if (addr == 916) {
+    chksum = GET_BYTE(to_push, 6) & 0xF;
+  } else if (addr == 1057) {
+    chksum = GET_BYTE(to_push, 7) >> 4;
+  } else {
+    chksum = 0;
+  }
+  return chksum;
+}
+
+static uint8_t hyundai_compute_checksum(CAN_FIFOMailBox_TypeDef *to_push) {
+  int addr = GET_ADDR(to_push);
+
+  uint8_t chksum = 0;
+  // same algorithm, but checksum is in a different place
+  for (int i = 0; i < 8; i++) {
+    uint8_t b = GET_BYTE(to_push, i);
+    if (((addr == 608) && (i == 7)) || ((addr == 916) && (i == 6)) || ((addr == 1057) && (i == 7))) {
+      b &= (addr == 1057) ? 0x0FU : 0xF0U; // remove checksum
+    }
+    chksum += (b % 16U) + (b / 16U);
+  }
+  chksum = (16U - (chksum %  16U)) % 16U;
+  return chksum;
+}
+
 static int hyundai_rx_hook(CAN_FIFOMailBox_TypeDef *to_push) {
 
   bool valid = addr_safety_check(to_push, hyundai_rx_checks, HYUNDAI_RX_CHECK_LEN,
-                                 NULL, NULL, hyundai_get_counter);
+                                 hyundai_get_checksum, hyundai_compute_checksum,
+                                 hyundai_get_counter);
 
   bool unsafe_allow_gas = unsafe_mode & UNSAFE_DISABLE_DISENGAGE_ON_GAS;
 
@@ -191,7 +224,6 @@ static int hyundai_fwd_hook(int bus_num, CAN_FIFOMailBox_TypeDef *to_fwd) {
   return bus_fwd;
 }
 
-
 const safety_hooks hyundai_hooks = {
   .init = nooutput_init,
   .rx = hyundai_rx_hook,

tests/safety/common.py

@@ -32,8 +32,10 @@ def make_msg(bus, addr, length=8):
   return package_can_msg([addr, 0, b'\x00'*length, bus])
 
 class CANPackerPanda(CANPacker):
-  def make_can_msg_panda(self, name_or_addr, bus, values, counter=-1):
+  def make_can_msg_panda(self, name_or_addr, bus, values, counter=-1, fix_checksum=None):
     msg = self.make_can_msg(name_or_addr, bus, values, counter=-1)
+    if fix_checksum is not None:
+      msg = fix_checksum(msg)
     return package_can_msg(msg)
 
 class PandaSafetyTestBase(unittest.TestCase):

tests/safety/test_hyundai.py

@@ -16,6 +16,22 @@
 DRIVER_TORQUE_ALLOWANCE = 50
 DRIVER_TORQUE_FACTOR = 2
 
+# 4 bit checkusm used in some hyundai messages
+# lives outside the can packer because we never send this msg
+def checksum(msg):
+  addr, t, dat, bus = msg
+
+  chksum = 0
+  for i, b in enumerate(dat):
+    if addr in [608, 1057] and i == 7:
+      b &= 0x0F if addr == 1057 else 0xF0
+    elif addr == 916 and i == 6:
+      b &= 0xF0
+    chksum += sum(divmod(b, 16))
+  chksum = (16 - chksum) % 16
+  ret = bytearray(dat)
+  ret[6 if addr == 916 else 7] |= chksum << (4 if addr == 1057 else 0)
+  return addr, t, ret, bus
 
 class TestHyundaiSafety(common.PandaSafetyTest):
   TX_MSGS = [[832, 0], [1265, 0], [1157, 0]]
@@ -43,12 +59,12 @@ def _button_msg(self, buttons):
   def _gas_msg(self, val):
     values = {"CF_Ems_AclAct": val, "AliveCounter": self.cnt_gas % 4}
     self.__class__.cnt_gas += 1
-    return self.packer.make_can_msg_panda("EMS16", 0, values)
+    return self.packer.make_can_msg_panda("EMS16", 0, values, fix_checksum=checksum)
 
   def _brake_msg(self, brake):
     values = {"DriverBraking": brake, "AliveCounterTCS": self.cnt_brake % 8}
     self.__class__.cnt_brake += 1
-    return self.packer.make_can_msg_panda("TCS13", 0, values)
+    return self.packer.make_can_msg_panda("TCS13", 0, values, fix_checksum=checksum)
 
   def _speed_msg(self, speed):
     # panda safety doesn't scale, so undo the scaling
@@ -61,7 +77,7 @@ def _speed_msg(self, speed):
   def _pcm_status_msg(self, enabled):
     values = {"ACCMode": enabled, "CR_VSM_Alive": self.cnt_cruise % 16}
     self.__class__.cnt_cruise += 1
-    return self.packer.make_can_msg_panda("SCC12", 0, values)
+    return self.packer.make_can_msg_panda("SCC12", 0, values, fix_checksum=checksum)
 
   def _set_prev_torque(self, t):
     self.safety.set_desired_torque_last(t)