1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
use crate::codec::{Error, Decode, Input};
const DECODE_MAX_DEPTH_MSG: &str = "Maximum recursion depth reached when decoding";
pub trait DecodeLimit: Sized {
fn decode_with_depth_limit(limit: u32, input: &[u8]) -> Result<Self, Error>;
fn decode_all_with_depth_limit(limit: u32, input: &[u8]) -> Result<Self, Error>;
}
struct DepthTrackingInput<'a, I> {
input: &'a mut I,
depth: u32,
max_depth: u32,
}
impl<'a, I:Input> Input for DepthTrackingInput<'a, I> {
fn remaining_len(&mut self) -> Result<Option<usize>, Error> {
self.input.remaining_len()
}
fn read(&mut self, into: &mut [u8]) -> Result<(), Error> {
self.input.read(into)
}
fn read_byte(&mut self) -> Result<u8, Error> {
self.input.read_byte()
}
fn descend_ref(&mut self) -> Result<(), Error> {
self.input.descend_ref()?;
self.depth += 1;
if self.depth > self.max_depth {
Err(DECODE_MAX_DEPTH_MSG.into())
} else {
Ok(())
}
}
fn ascend_ref(&mut self) {
self.input.ascend_ref();
self.depth -= 1;
}
}
impl<T: Decode> DecodeLimit for T {
fn decode_all_with_depth_limit(limit: u32, input: &[u8]) -> Result<Self, Error> {
let mut input = DepthTrackingInput {
input: &mut &input[..],
depth: 0,
max_depth: limit,
};
let res = T::decode(&mut input)?;
if input.input.is_empty() {
Ok(res)
} else {
Err(crate::decode_all::DECODE_ALL_ERR_MSG.into())
}
}
fn decode_with_depth_limit(limit: u32, input: &[u8]) -> Result<Self, Error> {
let mut input = DepthTrackingInput {
input: &mut &input[..],
depth: 0,
max_depth: limit,
};
T::decode(&mut input)
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::Encode;
#[test]
fn decode_limit_works() {
type NestedVec = Vec<Vec<Vec<Vec<u8>>>>;
let nested: NestedVec = vec![vec![vec![vec![1]]]];
let encoded = nested.encode();
let decoded = NestedVec::decode_with_depth_limit(3, &encoded).unwrap();
assert_eq!(decoded, nested);
assert!(NestedVec::decode_with_depth_limit(2, &encoded).is_err());
}
}