abi: decode signed numbers properly

Author: mhw0

src/abi.c

@@ -707,7 +707,7 @@ ETH_OP eth_abi_bytes(struct eth_abi *abi, uint8_t *bytes, size_t *len) {
 ETH_OP eth_abi_mpint(struct eth_abi *abi, mp_int *mpint) {
   struct ethc_abi_dynamic_type *ctype = NULL;
   uint8_t buf[32] = {0}, size = 0;
-  mp_int pow256, tmpint;
+  mp_int mask, tmpint;
   ETH_OP op;
 
   if (abi == NULL || mpint == NULL)
@@ -724,18 +724,18 @@ ETH_OP eth_abi_mpint(struct eth_abi *abi, mp_int *mpint) {
 
     // if the mpint is a negative number
     if (mp_cmp_d(&tmpint, 0) == MP_LT) {
-      if (mp_init(&pow256) != MP_OKAY) {
+      if (mp_init(&mask) != MP_OKAY) {
         mp_clear(&tmpint);
         return ETH_ERR_MP;
       }
 
-      if (mp_2expt(&pow256, 256) != MP_OKAY) {
-        mp_clear_multi(&tmpint, &pow256, NULL);
+      if (mp_2expt(&mask, 256) != MP_OKAY) {
+        mp_clear_multi(&tmpint, &mask, NULL);
         return ETH_ERR_MP;
       }
 
-      if (mp_add(&tmpint, &pow256, &tmpint) != MP_OKAY) {
-        mp_clear_multi(&tmpint, &pow256, NULL);
+      if (mp_add(&tmpint, &mask, &tmpint) != MP_OKAY) {
+        mp_clear_multi(&tmpint, &mask, NULL);
         return ETH_ERR_MP;
       }
     }
@@ -767,21 +767,21 @@ ETH_OP eth_abi_mpint(struct eth_abi *abi, mp_int *mpint) {
       return ETH_ERR_MP;
 
     // if the most significant bit is set (is negative)
-    if (s_mp_get_bit(mpint, 0xff) == MP_YES) {
-      if (mp_init(&pow256) != MP_OKAY)
+    if (buf[0] & 0x80) {
+      if (mp_init(&mask) != MP_OKAY)
         return ETH_ERR_MP;
 
-      if (mp_2expt(&pow256, 256) != MP_OKAY) {
-        mp_clear(&pow256);
+      if (mp_2expt(&mask, 256) != MP_OKAY) {
+        mp_clear(&mask);
         return ETH_ERR_MP;
       }
 
-      if (mp_sub(mpint, &pow256, mpint) != MP_OKAY) {
-        mp_clear(&pow256);
+      if (mp_sub(mpint, &mask, mpint) != MP_OKAY) {
+        mp_clear(&mask);
         return ETH_ERR_MP;
       }
 
-      mp_clear(&pow256);
+      mp_clear(&mask);
       return ETH_OK;
     }
 

test/test-eth-abi.c

@@ -247,13 +247,13 @@ void test_eth_abi_int64(void) {
 
 void test_eth_abi_mpint(void) {
   struct eth_abi abi0={0}, abi1={0};
-  mp_int int0, int1, int2, int3, int4;
+  mp_int int0, int1, int2, int3, int4, int5, int6;
   size_t hexlen;
   char *hex;
 
   diag("eth_abi_mpint()");
 
-  assert(mp_init_multi(&int0, &int1, &int2, &int3, &int4, NULL) == MP_OKAY);
+  assert(mp_init_multi(&int0, &int1, &int2, &int3, &int4, &int5, &int6, NULL) == MP_OKAY);
 
   assert(mp_read_radix(&int0, "ff", 16) == MP_OKAY);
   assert(mp_read_radix(&int1, "-256", 10) == MP_OKAY);
@@ -273,14 +273,19 @@ void test_eth_abi_mpint(void) {
   free(hex);
 
   assert(eth_abi_from_hex(&abi1,
-        "ffffffffffffffffffffffffffffffffffffffffffffffff830dcf6847e523d0", -1) == ETH_OK);
-  assert(mp_read_radix(&int3, "-9003312033254005808", 10) == ETH_OK);
+        "fffffffffffffffffffffffffffffffffffffffffffffffffffffffffff8dc56"
+        "0000000000000000000000000000000000000000000000000000000001f9b628", -1) == ETH_OK);
 
+  assert(eth_abi_mpint(&abi1, &int3) == ETH_OK);
   assert(eth_abi_mpint(&abi1, &int4) == ETH_OK);
 
-  ok(mp_cmp(&int3, &int4) == MP_EQ, "decode -9003312033254005808");
+  assert(mp_read_radix(&int5, "-467882", 10) == MP_OKAY);
+  assert(mp_read_radix(&int6, "33142312", 10) == MP_OKAY);
 
-  mp_clear_multi(&int0, &int1, &int2, &int3, &int4, NULL);
+  ok(mp_cmp(&int3, &int5) == MP_EQ, "decode -467882");
+  ok(mp_cmp(&int4, &int6) == MP_EQ, "decode 33142312");
+
+  mp_clear_multi(&int0, &int1, &int2, &int3, &int4, &int5, &int6, NULL);
 }
 
 void test_eth_abi_bytes8() {