s

Author: Chandra Pratap

tests/fuzz/fuzz-amount-arith.c

@@ -2,6 +2,7 @@
 #include <assert.h>
 #include <math.h>
 #include <common/amount.h>
+#include <common/overflows.h>
 #include <tests/fuzz/libfuzz.h>
 
 void init(int *argc, char ***argv) {}
@@ -109,9 +110,16 @@ void run(const uint8_t *data, size_t size) {
     {
         if (b.millisatoshis == 0)
             break;
+
+        // The assertion remains valid ONLY if there's no overflow
+        if (a.millisatoshis > UINT64_MAX - b.millisatoshis + 1) {
+            break;
+        }
+
         u64 ceil = amount_msat_ratio_ceil(a, b);
         u64 quotient = a.millisatoshis / b.millisatoshis;
         u64 remainder = a.millisatoshis % b.millisatoshis;
+
         assert(ceil == quotient + (remainder != 0));
         break;
     }
@@ -195,13 +203,22 @@ void run(const uint8_t *data, size_t size) {
     {
         u32 fee_base = (u32)(a.millisatoshis & UINT32_MAX);
         u32 fee_prop = (u32)(b.millisatoshis & UINT32_MAX);
-        if (amount_msat_add_fee(&a, fee_base, fee_prop)) {
-            struct amount_msat fee;
-            if (amount_msat_fee(&fee, a, fee_base, fee_prop)) {
-                assert(amount_msat_greater_eq(a, fee));
+
+        struct amount_msat original = a;
+        struct amount_msat fee;
+
+        if (amount_msat_fee(&fee, original, fee_base, fee_prop)) {
+            struct amount_msat total;
+            if (amount_msat_add(&total, original, fee)) {
+                assert(amount_msat_greater_eq(total, fee));
+
+                struct amount_msat expected_total;
+                assert(amount_msat_add(&expected_total, original, fee));
+                assert(amount_msat_eq(total, expected_total));
+
+                a = total;
             }
         }
-        break;
     }
 
     case OP_SUB_FEE:
@@ -210,8 +227,9 @@ void run(const uint8_t *data, size_t size) {
         u32 fee_prop = (u32)(b.millisatoshis & UINT32_MAX);
         struct amount_msat input = a;
         struct amount_msat output = amount_msat_sub_fee(input, fee_base, fee_prop);
+
         struct amount_msat fee;
-        if (amount_msat_fee(&fee, input, fee_base, fee_prop)) {
+        if (amount_msat_fee(&fee, output, fee_base, fee_prop)) {
             struct amount_msat sum;
             if (amount_msat_add(&sum, output, fee)) {
                 assert(amount_msat_less_eq(sum, input));
@@ -226,6 +244,10 @@ void run(const uint8_t *data, size_t size) {
             break;
         u32 fee_per_kw = (u32)(a.millisatoshis & UINT32_MAX);
         size_t weight = (size_t)(b.millisatoshis);
+
+        /* weights > 2^32 are not real tx and hence, discarded */
+        if (mul_overflows_u64(fee_per_kw, weight))
+            break;
         struct amount_sat fee = amount_tx_fee(fee_per_kw, weight);
         u64 expected = (fee_per_kw * weight) / MSAT_PER_SAT;
         assert(fee.satoshis == expected);