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Document a further fuzzer-found limitation #515

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Oct 11, 2023
Merged

Document a further fuzzer-found limitation #515

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8 changes: 5 additions & 3 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -194,9 +194,6 @@ While data structures with any of these attributes should generally roundtrip th
- externally tagged tuple variants with just one field (that are not newtype variants)
- tuples or arrays with just one element are not supported inside newtype variants with `#[enable(unwrap_variant_newtypes)]`
- a `ron::value::RawValue`
- internally tagged newtype variants and `#[serde(flatten)]`ed fields must not contain:
- a unit or a unit struct inside an untagged newtype variant
- an untagged unit variant
- untagged tuple / struct variants with no fields are not supported
- untagged tuple variants with just one field (that are not newtype variants) are not supported when the `#![enable(unwrap_variant_newtypes)]` extension is enabled
- serializing a `ron::value::RawValue` using a `PrettyConfig` may add leading and trailing whitespace and comments, which the `ron::value::RawValue` absorbs upon deserialization
Expand All @@ -214,6 +211,11 @@ Furthermore, serde imposes the following restrictions for data to roundtrip:
- a flattened tagged struct
- internally (or adjacently) tagged or untagged enum variants or `#[serde(flatten)]`ed fields must not contain:
- `i128` or `u128` values
- internally tagged newtype variants and `#[serde(flatten)]`ed fields must not contain:
- a unit or a unit struct inside an untagged newtype variant
- an untagged unit variant
- internally tagged newtype variants, which are `#[serde(flatten)]`ed together with other fields, must not contain:
- a unit or unit struct or an untagged unit variant

Please file a [new issue](https://github.com/ron-rs/ron/issues/new) if you come across a use case which is not listed among the above restrictions but still breaks.

Expand Down
60 changes: 17 additions & 43 deletions fuzz/fuzz_targets/bench/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -5191,7 +5191,7 @@ impl<'a> SerdeDataType<'a> {
{
return Err(arbitrary::Error::IncorrectFormat);
}
if matches!(representation, SerdeEnumRepresentation::InternallyTagged { tag: _ } if !inner.supported_inside_internally_tagged_newtype(&value, false))
if matches!(representation, SerdeEnumRepresentation::InternallyTagged { tag: _ } if !inner.supported_inside_internally_tagged_newtype(false))
{
return Err(arbitrary::Error::IncorrectFormat);
}
Expand Down Expand Up @@ -5472,7 +5472,6 @@ impl<'a> SerdeDataType<'a> {

fn supported_inside_internally_tagged_newtype(
&self,
value: &SerdeDataValue,
inside_untagged_newtype_variant: bool,
) -> bool {
// See https://github.com/serde-rs/serde/blob/ddc1ee564b33aa584e5a66817aafb27c3265b212/serde/src/private/ser.rs#L94-L336
Expand Down Expand Up @@ -5513,14 +5512,7 @@ impl<'a> SerdeDataType<'a> {
!inside_untagged_newtype_variant
}
SerdeDataType::Newtype { name: _, inner: ty } => {
if let SerdeDataValue::Newtype { inner: value } = value {
ty.supported_inside_internally_tagged_newtype(
value,
inside_untagged_newtype_variant,
)
} else {
false
}
ty.supported_inside_internally_tagged_newtype(inside_untagged_newtype_variant)
}
SerdeDataType::TupleStruct { name: _, fields: _ } => false,
SerdeDataType::Struct {
Expand All @@ -5533,53 +5525,27 @@ impl<'a> SerdeDataType<'a> {
variants,
representation,
} => {
let SerdeDataValue::Enum {
variant: variant_index,
value,
} = value
else {
return false;
};

let Some(ty) = variants.1.get(*variant_index as usize) else {
return false;
};

match (ty, value) {
(SerdeDataVariantType::Unit, SerdeDataVariantValue::Unit)
| (
SerdeDataVariantType::TaggedOther,
SerdeDataVariantValue::TaggedOther { .. },
) => {
variants.1.iter().all(|ty| match ty {
SerdeDataVariantType::Unit | SerdeDataVariantType::TaggedOther => {
// BUG: an untagged unit variant requires a unit,
// but it won't get one because it serialises itself as a unit,
// which is only serialised with the tag
!matches!(representation, SerdeEnumRepresentation::Untagged)
}
(
SerdeDataVariantType::Newtype { inner: ty },
SerdeDataVariantValue::Newtype { inner: value },
) => {
SerdeDataVariantType::Newtype { inner: ty } => {
if matches!(representation, SerdeEnumRepresentation::Untagged) {
ty.supported_inside_internally_tagged_newtype(value, true)
ty.supported_inside_internally_tagged_newtype(true)
} else {
true
}
}
(
SerdeDataVariantType::Tuple { fields: _ },
SerdeDataVariantValue::Struct { fields: _ },
) => !matches!(
SerdeDataVariantType::Tuple { fields: _ } => !matches!(
representation,
SerdeEnumRepresentation::Untagged
| SerdeEnumRepresentation::AdjacentlyTagged { .. }
),
(
SerdeDataVariantType::Struct { fields: _ },
SerdeDataVariantValue::Struct { fields: _ },
) => true,
_ => false,
}
SerdeDataVariantType::Struct { fields: _ } => true,
})
}
}
}
Expand Down Expand Up @@ -5802,6 +5768,14 @@ impl<'a> SerdeDataType<'a> {
has_unknown_key,
)
} else if is_flattened {
if matches!(representation, SerdeEnumRepresentation::InternallyTagged { tag: _ }) {
// BUG: an flattened internally tagged newtype alongside other flattened data
// must not contain a unit, unit struct, or untagged unit variant
if !inner.supported_inside_internally_tagged_newtype(true) {
return false;
}
}

if *has_flattened_map {
// BUG: a flattened map will also see the unknown key (serde)
return false;
Expand Down
87 changes: 87 additions & 0 deletions tests/502_known_bugs.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2800,6 +2800,93 @@ fn untagged_unit_variant_inside_flatten_struct_variant() {
);
}

#[test]
fn unit_inside_internally_tagged_newtype_variant_inside_multi_flatten_struct() {
#[derive(PartialEq, Debug, Serialize, Deserialize)]
struct AnotherFlattenedStruct {
hi: i32,
}

#[derive(PartialEq, Debug, Serialize, Deserialize)]
#[serde(tag = "tag")]
enum InternallyTagged {
Newtype(()),
}

#[derive(PartialEq, Debug, Serialize, Deserialize)]
struct FlattenedStruct {
ho: i32,
#[serde(flatten)]
a: InternallyTagged,
#[serde(flatten)]
b: AnotherFlattenedStruct,
}

assert_eq!(
check_roundtrip(
&FlattenedStruct {
ho: 24,
a: InternallyTagged::Newtype(()),
b: AnotherFlattenedStruct { hi: 42 },
},
PrettyConfig::default()
),
Err(Err(SpannedError {
code: Error::InvalidValueForType {
expected: String::from("unit"),
found: String::from("a map")
},
position: Position { line: 5, col: 1 }
}))
);
}

#[test]
fn untagged_unit_variant_inside_internally_tagged_newtype_variant_inside_multi_flatten_struct() {
#[derive(PartialEq, Debug, Serialize, Deserialize)]
#[serde(untagged)]
enum Untagged {
Unit,
}

#[derive(PartialEq, Debug, Serialize, Deserialize)]
struct AnotherFlattenedStruct {
hi: i32,
}

#[derive(PartialEq, Debug, Serialize, Deserialize)]
#[serde(tag = "tag")]
enum InternallyTagged {
Newtype(Untagged),
}

#[derive(PartialEq, Debug, Serialize, Deserialize)]
struct FlattenedStruct {
ho: i32,
#[serde(flatten)]
a: InternallyTagged,
#[serde(flatten)]
b: AnotherFlattenedStruct,
}

assert_eq!(
check_roundtrip(
&FlattenedStruct {
ho: 24,
a: InternallyTagged::Newtype(Untagged::Unit),
b: AnotherFlattenedStruct { hi: 42 },
},
PrettyConfig::default()
),
Err(Err(SpannedError {
code: Error::Message(String::from(
"data did not match any variant of untagged enum Untagged"
)),
position: Position { line: 5, col: 1 }
}))
);
}

fn check_roundtrip<T: PartialEq + std::fmt::Debug + Serialize + serde::de::DeserializeOwned>(
val: &T,
config: PrettyConfig,
Expand Down
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