fix(overflow): Fix integer overflows in BinaryEncoding and Pactus (#4592)

* fix(binary-coding): Avoid unsigned integer overflow

* fix(pactus): Avoid unsigned integer overflow

Author: satoshiotomakan

rust/chains/tw_pactus/src/types/amount.rs

@@ -5,7 +5,15 @@ pub struct Amount(pub i64);
 
 impl Encodable for Amount {
     fn encode(&self, w: &mut dyn std::io::Write) -> Result<(), Error> {
-        VarInt::from(self.0 as usize).encode(w)
+        let amount: usize = match self.0.try_into() {
+            Ok(amount) => amount,
+            Err(_) => {
+                return Err(Error::IoError(std::io::Error::from(
+                    std::io::ErrorKind::InvalidInput,
+                )));
+            },
+        };
+        VarInt::from(amount).encode(w)
     }
 
     fn encoded_size(&self) -> usize {

src/BinaryCoding.cpp

@@ -147,7 +147,9 @@ tuple<bool, string>  decodeString(const Data& in, size_t& indexInOut) {
     if (!get<0>(lenTup)) { return make_tuple(false, ""); }
     const auto len = get<1>(lenTup);
     // read bytes into string
-    if (in.size() < indexInOut + len) { return make_tuple(false, ""); }
+    if (in.size() < indexInOut || in.size() - indexInOut < len) {
+        return make_tuple(false, "");
+    }
     string result(in.data() + indexInOut, in.data() + indexInOut + len);
     indexInOut += len;
     return make_tuple(true, result);