From 29fa0a369d28eedbf6741a7699ce257175275029 Mon Sep 17 00:00:00 2001
From: Shawn Tabrizi <shawntabrizi@gmail.com>
Date: Thu, 17 Jun 2021 12:51:36 +0100
Subject: [PATCH] Add XCM Decode Limit (#3273)
* Add XCM Decode Limit of 256
* use `decode_all_*`
* Update xcm/src/double_encoded.rs
---
polkadot/xcm/src/double_encoded.rs | 17 ++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)
diff --git a/polkadot/xcm/src/double_encoded.rs b/polkadot/xcm/src/double_encoded.rs
index d9ba93d7d6e..4bd5dc0eb59 100644
--- a/polkadot/xcm/src/double_encoded.rs
+++ b/polkadot/xcm/src/double_encoded.rs
@@ -15,7 +15,10 @@
// along with Polkadot. If not, see <http://www.gnu.org/licenses/>.
use alloc::vec::Vec;
-use parity_scale_codec::{Encode, Decode};
+use parity_scale_codec::{Encode, Decode, DecodeLimit};
+
+/// Maximum nesting level for XCM decoding.
+pub const MAX_XCM_DECODE_DEPTH: u32 = 8;
/// Wrapper around the encoded and decoded versions of a value.
/// Caches the decoded value once computed.
@@ -69,14 +72,22 @@ impl<T: Decode> DoubleEncoded<T> {
/// Returns a reference to the value in case of success and `Err(())` in case the decoding fails.
pub fn ensure_decoded(&mut self) -> Result<&T, ()> {
if self.decoded.is_none() {
- self.decoded = T::decode(&mut &self.encoded[..]).ok();
+ self.decoded = T::decode_all_with_depth_limit(
+ MAX_XCM_DECODE_DEPTH,
+ &mut &self.encoded[..],
+ ).ok();
}
self.decoded.as_ref().ok_or(())
}
/// Move the decoded value out or (if not present) decode `encoded`.
pub fn take_decoded(&mut self) -> Result<T, ()> {
- self.decoded.take().or_else(|| T::decode(&mut &self.encoded[..]).ok()).ok_or(())
+ self.decoded.take().or_else(|| {
+ T::decode_all_with_depth_limit(
+ MAX_XCM_DECODE_DEPTH,
+ &mut &self.encoded[..],
+ ).ok()
+ }).ok_or(())
}
/// Provides an API similar to `TryInto` that allows fallible conversion to the inner value type.
--
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