From 7f3b1774dd248d4ebad91cc9de0fb1c561fab54b Mon Sep 17 00:00:00 2001
From: Adeeb <8762862+quillford@users.noreply.github.com>
Date: Thu, 30 Apr 2020 14:06:26 -0700
Subject: [PATCH] Chrysler: calculate checksum in can packer/parser (#255)

* calculate chrysler checksum in can packer/parser

* remove comment
---
 can/common.cc       | 32 ++++++++++++++++++++++++++++++++
 can/common.h        |  1 +
 can/common.pxd      |  3 ++-
 can/common_dbc.h    |  1 +
 can/dbc_template.cc |  2 ++
 can/packer.cc       |  3 +++
 can/parser.cc       |  5 +++++
 can/process_dbc.py  |  7 +++++++
 8 files changed, 53 insertions(+), 1 deletion(-)

diff --git a/can/common.cc b/can/common.cc
index 68c3ee0..b303391 100644
--- a/can/common.cc
+++ b/can/common.cc
@@ -35,6 +35,38 @@ unsigned int subaru_checksum(unsigned int address, uint64_t d, int l) {
   return s & 0xFF;
 }
 
+unsigned int chrysler_checksum(unsigned int address, uint64_t d, int l) {
+  /* This function does not want the checksum byte in the input data.
+  jeep chrysler canbus checksum from http://illmatics.com/Remote%20Car%20Hacking.pdf */
+  uint8_t checksum = 0xFF;
+  for (int j = 0; j < (l - 1); j++) {
+    uint8_t shift = 0x80;
+    uint8_t curr = (d >> 8*j) & 0xFF;
+    for (int i=0; i<8; i++) {
+      uint8_t bit_sum = curr & shift;
+      uint8_t temp_chk = checksum & 0x80U;
+      if (bit_sum != 0U) {
+        bit_sum = 0x1C;
+        if (temp_chk != 0U) {
+          bit_sum = 1;
+        }
+        checksum = checksum << 1;
+        temp_chk = checksum | 1U;
+        bit_sum ^= temp_chk;
+      } else {
+        if (temp_chk != 0U) {
+          bit_sum = 0x1D;
+        }
+        checksum = checksum << 1;
+        bit_sum ^= checksum;
+      }
+      checksum = bit_sum;
+      shift = shift >> 1;
+    }
+  }
+  return ~checksum & 0xFF;
+}
+
 // Static lookup table for fast computation of CRC8 poly 0x2F, aka 8H2F/AUTOSAR
 uint8_t crc8_lut_8h2f[256];
 
diff --git a/can/common.h b/can/common.h
index 841c060..dd91a6c 100644
--- a/can/common.h
+++ b/can/common.h
@@ -14,6 +14,7 @@
 unsigned int honda_checksum(unsigned int address, uint64_t d, int l);
 unsigned int toyota_checksum(unsigned int address, uint64_t d, int l);
 unsigned int subaru_checksum(unsigned int address, uint64_t d, int l);
+unsigned int chrysler_checksum(unsigned int address, uint64_t d, int l);
 void init_crc_lookup_tables();
 unsigned int volkswagen_crc(unsigned int address, uint64_t d, int l);
 unsigned int pedal_checksum(uint64_t d, int l);
diff --git a/can/common.pxd b/can/common.pxd
index 0082110..5519140 100644
--- a/can/common.pxd
+++ b/can/common.pxd
@@ -19,7 +19,8 @@ cdef extern from "common_dbc.h":
     PEDAL_COUNTER,
     VOLKSWAGEN_CHECKSUM,
     VOLKSWAGEN_COUNTER,
-    SUBARU_CHECKSUM
+    SUBARU_CHECKSUM,
+    CHRYSLER_CHECKSUM
 
   cdef struct Signal:
     const char* name
diff --git a/can/common_dbc.h b/can/common_dbc.h
index 317e805..e5c12ba 100644
--- a/can/common_dbc.h
+++ b/can/common_dbc.h
@@ -39,6 +39,7 @@ enum SignalType {
   VOLKSWAGEN_CHECKSUM,
   VOLKSWAGEN_COUNTER,
   SUBARU_CHECKSUM,
+  CHRYSLER_CHECKSUM,
 };
 
 struct Signal {
diff --git a/can/dbc_template.cc b/can/dbc_template.cc
index 439643a..f6d4988 100644
--- a/can/dbc_template.cc
+++ b/can/dbc_template.cc
@@ -31,6 +31,8 @@ const Signal sigs_{{address}}[] = {
       .type = SignalType::VOLKSWAGEN_COUNTER,
       {% elif checksum_type == "subaru" and sig.name == "CHECKSUM" %}
       .type = SignalType::SUBARU_CHECKSUM,
+      {% elif checksum_type == "chrysler" and sig.name == "CHECKSUM" %}
+      .type = SignalType::CHRYSLER_CHECKSUM,
       {% elif address in [512, 513] and sig.name == "CHECKSUM_PEDAL" %}
       .type = SignalType::PEDAL_CHECKSUM,
       {% elif address in [512, 513] and sig.name == "COUNTER_PEDAL" %}
diff --git a/can/packer.cc b/can/packer.cc
index 7efedfa..ba675a5 100644
--- a/can/packer.cc
+++ b/can/packer.cc
@@ -102,6 +102,9 @@ uint64_t CANPacker::pack(uint32_t address, const std::vector<SignalPackValue> &s
     } else if (sig.type == SignalType::SUBARU_CHECKSUM) {
       unsigned int chksm = subaru_checksum(address, ret, message_lookup[address].size);
       ret = set_value(ret, sig, chksm);
+    } else if (sig.type == SignalType::CHRYSLER_CHECKSUM) {
+      unsigned int chksm = chrysler_checksum(address, ReverseBytes(ret), message_lookup[address].size);
+      ret = set_value(ret, sig, chksm);
     } else {
       //WARN("CHECKSUM signal type not valid\n");
     }
diff --git a/can/parser.cc b/can/parser.cc
index 69fe374..315fd50 100644
--- a/can/parser.cc
+++ b/can/parser.cc
@@ -57,6 +57,11 @@ bool MessageState::parse(uint64_t sec, uint16_t ts_, uint8_t * dat) {
         if (!update_counter_generic(tmp, sig.b2)) {
         return false;
       }
+    } else if (sig.type == SignalType::CHRYSLER_CHECKSUM) {
+      if (chrysler_checksum(address, dat_le, size) != tmp) {
+        INFO("0x%X CHECKSUM FAIL\n", address);
+        return false;
+      }
     } else if (sig.type == SignalType::PEDAL_CHECKSUM) {
       if (pedal_checksum(dat_be, size) != tmp) {
         INFO("0x%X PEDAL CHECKSUM FAIL\n", address);
diff --git a/can/process_dbc.py b/can/process_dbc.py
index c39184d..1ca0db2 100755
--- a/can/process_dbc.py
+++ b/can/process_dbc.py
@@ -53,6 +53,13 @@ def process(in_fn, out_fn):
     checksum_start_bit = 0
     counter_start_bit = None
     little_endian = True
+  elif can_dbc.name.startswith(("chrysler_")):
+    checksum_type = "chrysler"
+    checksum_size = 8
+    counter_size = None
+    checksum_start_bit = 7
+    counter_start_bit = None
+    little_endian = False
   else:
     checksum_type = None
     checksum_size = None