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mpt: enforce embedded subnode RLP size < 32 in branch/extension validation #1498

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mpt: enforce embedded subnode RLP size < 32 in branch/extension validation #1498

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17 changes: 16 additions & 1 deletion python/mpt/src/mpt/utils.cairo
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Original file line number Diff line number Diff line change
Expand Up @@ -14,7 +14,7 @@ from ethereum.prague.trie import (
SubnodesStruct,
bytes_to_nibble_list,
)
from ethereum_rlp.rlp import Extended, ExtendedEnum, ExtendedImpl, decode
from ethereum_rlp.rlp import Extended, ExtendedEnum, ExtendedImpl, decode, encode
from ethereum_types.bytes import Bytes, BytesStruct
from starkware.cairo.common.alloc import alloc
from starkware.cairo.common.math_cmp import is_le_felt
Expand Down Expand Up @@ -184,6 +184,11 @@ func check_branch_node(node: BranchNode) {
if (x.value.sequence.value.len == 0) {
raise_ValueError('LTTwoNonNullSubnodes');
}
// Embedded nodes must have RLP encoding size < 32
let encoded = encode(x);
if (encoded.value.len >= 32) {
raise_ValueError('EmbeddedNodeTooLarge');
}
}

// Check that the second subnode is not None and not empty
Expand All @@ -201,6 +206,11 @@ func check_branch_node(node: BranchNode) {
if (y.value.sequence.value.len == 0) {
raise_ValueError('LTTwoNonNullSubnodes');
}
// Embedded nodes must have RLP encoding size < 32
let encoded = encode(y);
if (encoded.value.len >= 32) {
raise_ValueError('EmbeddedNodeTooLarge');
}
}

return ();
Expand Down Expand Up @@ -273,6 +283,11 @@ func check_extension_node(node: ExtensionNode, parent_node: OptionalInternalNode
if (sequence_variant.len == 0) {
raise_ValueError('EmptySubnode');
}
// Embedded node must have RLP encoding size < 32
let encoded = encode(subnode);
if (encoded.value.len >= 32) {
raise_ValueError('EmbeddedNodeTooLarge');
}
return ();
}

Expand Down
15 changes: 15 additions & 0 deletions python/mpt/src/mpt/utils.py
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Original file line number Diff line number Diff line change
Expand Up @@ -91,6 +91,15 @@ def check_branch_node(node: BranchNode) -> None:
if len(non_null_subnodes) < 2:
raise ValueError("LTTwoNonNullSubnodes")

# For each embedded subnode (represented as a list), ensure its RLP encoding is < 32 bytes
for subnode in node.subnodes:
if subnode in (None, b""):
continue
if isinstance(subnode, list):
encoded = rlp.encode(subnode)
if len(encoded) >= 32:
raise ValueError("EmbeddedNodeTooLarge")


def check_leaf_node(path: Bytes, node: LeafNode) -> None:
"""
Expand Down Expand Up @@ -121,3 +130,9 @@ def check_extension_node(node: ExtensionNode, parent: Optional[InternalNode]) ->

if parent is not None and isinstance(parent, ExtensionNode):
raise ValueError("InvalidParent")

# If subnode is embedded (represented as a list), ensure its RLP encoding is < 32 bytes
if isinstance(node.subnode, list):
encoded = rlp.encode(node.subnode)
if len(encoded) >= 32:
raise ValueError("EmbeddedNodeTooLarge")