Replace Vec<u8> with [u8; 32] for contract storage key (#2184)

* Replace Vec<u8> with [u8; 32] for contract storage key

* Read storage keys from sandbox memory into fixed size buffer

* Increment `impl_version`

substrate/srml/contract/src/wasm/runtime.rs

@@ -177,6 +177,26 @@ fn read_sandbox_memory<E: Ext>(
 	Ok(buf)
 }
 
+/// Read designated chunk from the sandbox memory into the supplied buffer, consuming
+/// an appropriate amount of gas.
+///
+/// Returns `Err` if one of the following conditions occurs:
+///
+/// - calculating the gas cost resulted in overflow.
+/// - out of gas
+/// - requested buffer is not within the bounds of the sandbox memory.
+fn read_sandbox_memory_into_buf<E: Ext>(
+	ctx: &mut Runtime<E>,
+	ptr: u32,
+	buf: &mut [u8],
+) -> Result<(), sandbox::HostError> {
+	charge_gas(ctx.gas_meter, ctx.schedule, RuntimeToken::ReadMemory(buf.len() as u32))?;
+
+	ctx.memory().get(ptr, buf)?;
+
+	Ok(())
+}
+
 /// Write the given buffer to the designated location in the sandbox memory, consuming
 /// an appropriate amount of gas.
 ///
@@ -228,14 +248,15 @@ define_env!(Env, <E: Ext>,
 	//   where the value to set is placed. If `value_non_null` is set to 0, then this parameter is ignored.
 	// - value_len: the length of the value. If `value_non_null` is set to 0, then this parameter is ignored.
 	ext_set_storage(ctx, key_ptr: u32, value_non_null: u32, value_ptr: u32, value_len: u32) => {
-		let key = read_sandbox_memory(ctx, key_ptr, 32)?;
+		let mut key = [0; 32];
+		read_sandbox_memory_into_buf(ctx, key_ptr, &mut key)?;
 		let value =
 			if value_non_null != 0 {
 				Some(read_sandbox_memory(ctx, value_ptr, value_len)?)
 			} else {
 				None
 			};
-		ctx.ext.set_storage(&key, value);
+		ctx.ext.set_storage(key, value);
 
 		Ok(())
 	},
@@ -247,7 +268,8 @@ define_env!(Env, <E: Ext>,
 	// - key_ptr: pointer into the linear memory where the key
 	//   of the requested value is placed.
 	ext_get_storage(ctx, key_ptr: u32) -> u32 => {
-		let key = read_sandbox_memory(ctx, key_ptr, 32)?;
+		let mut key = [0; 32];
+		read_sandbox_memory_into_buf(ctx, key_ptr, &mut key)?;
 		if let Some(value) = ctx.ext.get_storage(&key) {
 			ctx.scratch_buf = value;
 			Ok(0)