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cbor: allow user to control nesting (#329)

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* cbor: allow user to control nesting

 - Make the default read/write entrypoints allow infinite nesting.
 - Add {read,write}_nested() entrypoints that allow the crate user to
   control the depth of nesting that's allowed.
 - Along the way, convert the write[_nested] variants to return a
   `Result<(), EncoderError>` rather than a bool.  This exposes
   more failure information (and forces the caller to take notice
   of those tailures), and allows use of the ? operator.

* fixup: transmute error

Co-authored-by: kaczmarczyck <43844792+kaczmarczyck@users.noreply.github.com>
This commit is contained in:
David Drysdale
2021-06-18 17:39:54 +00:00
committed by GitHub
parent dbce426e9f
commit 0287a09573
10 changed files with 111 additions and 99 deletions
Download Patch File Download Diff File Expand all files Collapse all files

42
libraries/cbor/src/reader.rs
View File

@@ -37,11 +37,18 @@ pub enum DecoderError {
OutOfRangeIntegerValue,
}
/// Deserialize CBOR binary data to produce a single [`Value`], expecting that there
/// is no additional data.
/// Deserialize CBOR binary data to produce a single [`Value`], expecting that there is no additional data.
/// Supports arbitrarily nested CBOR (so the [`DecoderError::TooMuchNesting`] error is never emitted).
pub fn read(encoded_cbor: &[u8]) -> Result<Value, DecoderError> {
read_nested(encoded_cbor, None)
}
/// Deserialize CBOR binary data to produce a single [`Value`], expecting that there is no additional data. If
/// `max_nest` is `Some(max)`, then nested structures are only supported up to the given limit (returning
/// [`DecoderError::TooMuchNesting`] if the limit is hit).
pub fn read_nested(encoded_cbor: &[u8], max_nest: Option<i8>) -> Result<Value, DecoderError> {
let mut reader = Reader::new(encoded_cbor);
let value = reader.decode_complete_data_item(Reader::MAX_NESTING_DEPTH)?;
let value = reader.decode_complete_data_item(max_nest)?;
if !reader.remaining_cbor.is_empty() {
return Err(DecoderError::ExtraneousData);
}
@@ -53,8 +60,6 @@ struct Reader<'a> {
}
impl<'a> Reader<'a> {
const MAX_NESTING_DEPTH: i8 = 4;
pub fn new(cbor: &'a [u8]) -> Reader<'a> {
Reader {
remaining_cbor: cbor,
@@ -63,9 +68,9 @@ impl<'a> Reader<'a> {
pub fn decode_complete_data_item(
&mut self,
remaining_depth: i8,
remaining_depth: Option<i8>,
) -> Result<Value, DecoderError> {
if remaining_depth < 0 {
if remaining_depth.map_or(false, |d| d < 0) {
return Err(DecoderError::TooMuchNesting);
}
@@ -162,12 +167,12 @@ impl<'a> Reader<'a> {
fn read_array_content(
&mut self,
size_value: u64,
remaining_depth: i8,
remaining_depth: Option<i8>,
) -> Result<Value, DecoderError> {
// Don't set the capacity already, it is an unsanitized input.
let mut value_array = Vec::new();
for _ in 0..size_value {
value_array.push(self.decode_complete_data_item(remaining_depth - 1)?);
value_array.push(self.decode_complete_data_item(remaining_depth.map(|d| d - 1))?);
}
Ok(cbor_array_vec!(value_array))
}
@@ -175,17 +180,20 @@ impl<'a> Reader<'a> {
fn read_map_content(
&mut self,
size_value: u64,
remaining_depth: i8,
remaining_depth: Option<i8>,
) -> Result<Value, DecoderError> {
let mut value_map = Vec::<(Value, Value)>::new();
for _ in 0..size_value {
let key = self.decode_complete_data_item(remaining_depth - 1)?;
let key = self.decode_complete_data_item(remaining_depth.map(|d| d - 1))?;
if let Some(last_item) = value_map.last() {
if last_item.0 >= key {
return Err(DecoderError::OutOfOrderKey);
}
}
value_map.push((key, self.decode_complete_data_item(remaining_depth - 1)?));
value_map.push((
key,
self.decode_complete_data_item(remaining_depth.map(|d| d - 1))?,
));
}
Ok(cbor_map_collection!(value_map))
}
@@ -193,9 +201,9 @@ impl<'a> Reader<'a> {
fn read_tagged_content(
&mut self,
tag_value: u64,
remaining_depth: i8,
remaining_depth: Option<i8>,
) -> Result<Value, DecoderError> {
let inner_value = self.decode_complete_data_item(remaining_depth - 1)?;
let inner_value = self.decode_complete_data_item(remaining_depth.map(|d| d - 1))?;
Ok(cbor_tagged!(tag_value, inner_value))
}
@@ -679,7 +687,7 @@ mod test {
];
for cbor in cases {
let mut reader = Reader::new(&cbor);
assert!(reader.decode_complete_data_item(0).is_ok());
assert!(reader.decode_complete_data_item(Some(0)).is_ok());
}
let map_cbor = vec![
0xa2, // map of 2 pairs
@@ -690,11 +698,11 @@ mod test {
];
let mut reader = Reader::new(&map_cbor);
assert_eq!(
reader.decode_complete_data_item(1),
reader.decode_complete_data_item(Some(1)),
Err(DecoderError::TooMuchNesting)
);
reader = Reader::new(&map_cbor);
assert!(reader.decode_complete_data_item(2).is_ok());
assert!(reader.decode_complete_data_item(Some(2)).is_ok());
}
#[test]