Limits the recursion depth of the parser.

parser/Cargo.toml

@@ -13,7 +13,7 @@ version = "4.0.6"
 
 [dependencies]
 async-graphql-value = { path = "../value", version = "4.0.6" }
-pest = "2.1.3"
+pest = "2.2.1"
 serde = { version = "1.0.125", features = ["derive"] }
 serde_json = "1.0.64"
 

parser/src/graphql.pest

@@ -16,7 +16,7 @@ selection_set = { "{" ~ selection+ ~ "}" }
 selection = { field | inline_fragment | fragment_spread }
 field = { alias? ~ name ~ arguments? ~ directives? ~ selection_set? }
 alias = { name ~ ":" }
-fragment_spread = { "..." ~ name ~ directives? }
+fragment_spread = { "..." ~ !type_condition ~ name ~ directives? }
 inline_fragment = { "..." ~ type_condition? ~ directives? ~ selection_set }
 
 fragment_definition = { "fragment" ~ name ~ type_condition ~ directives? ~ selection_set }

parser/src/lib.rs

@@ -78,6 +78,8 @@ pub enum Error {
     },
     /// The document does not contain any operation.
     MissingOperation,
+    /// Recursion limit exceeded.
+    RecursionLimitExceeded,
 }
 
 impl Error {
@@ -106,6 +108,7 @@ impl Error {
                 ErrorPositions::new_2(*second, *first)
             }
             Self::MissingOperation => ErrorPositions::new_0(),
+            Self::RecursionLimitExceeded => ErrorPositions::new_0(),
         }
     }
 }
@@ -126,6 +129,7 @@ impl Display for Error {
                 write!(f, "fragment {} is defined twice", fragment)
             }
             Self::MissingOperation => f.write_str("document does not contain an operation"),
+            Self::RecursionLimitExceeded => f.write_str("recursion limit exceeded."),
         }
     }
 }

parser/src/parse/executable.rs

@@ -2,6 +2,17 @@ use async_graphql_value::Name;
 
 use super::*;
 
+const MAX_RECURSION_DEPTH: usize = 64;
+
+macro_rules! recursion_depth {
+    ($remaining_depth:ident) => {{
+        if $remaining_depth == 0 {
+            return Err(Error::RecursionLimitExceeded);
+        }
+        $remaining_depth - 1
+    }};
+}
+
 /// Parse a GraphQL query document.
 ///
 /// # Errors
@@ -10,13 +21,10 @@ use super::*;
 pub fn parse_query<T: AsRef<str>>(input: T) -> Result<ExecutableDocument> {
     let mut pc = PositionCalculator::new(input.as_ref());
 
-    let items = parse_definition_items(
-        exactly_one(GraphQLParser::parse(
-            Rule::executable_document,
-            input.as_ref(),
-        )?),
-        &mut pc,
-    )?;
+    eprintln!("1");
+    let pairs = GraphQLParser::parse(Rule::executable_document, input.as_ref())?;
+    eprintln!("2");
+    let items = parse_definition_items(exactly_one(pairs), &mut pc)?;
 
     let mut operations = None;
     let mut fragments: HashMap<_, Positioned<FragmentDefinition>> = HashMap::new();
@@ -149,7 +157,7 @@ fn parse_operation_definition_item(
                     ty: OperationType::Query,
                     variable_definitions: Vec::new(),
                     directives: Vec::new(),
-                    selection_set: parse_selection_set(pair, pc)?,
+                    selection_set: parse_selection_set(pair, pc, MAX_RECURSION_DEPTH)?,
                 },
             },
             _ => unreachable!(),
@@ -172,7 +180,7 @@ fn parse_named_operation_definition(
         parse_variable_definitions(pair, pc)
     })?;
     let directives = parse_opt_directives(&mut pairs, pc)?;
-    let selection_set = parse_selection_set(pairs.next().unwrap(), pc)?;
+    let selection_set = parse_selection_set(pairs.next().unwrap(), pc, MAX_RECURSION_DEPTH)?;
 
     debug_assert_eq!(pairs.next(), None);
 
@@ -231,6 +239,7 @@ fn parse_variable_definition(
 fn parse_selection_set(
     pair: Pair<Rule>,
     pc: &mut PositionCalculator,
+    remaining_depth: usize,
 ) -> Result<Positioned<SelectionSet>> {
     debug_assert_eq!(pair.as_rule(), Rule::selection_set);
 
@@ -240,31 +249,41 @@ fn parse_selection_set(
         SelectionSet {
             items: pair
                 .into_inner()
-                .map(|pair| parse_selection(pair, pc))
+                .map(|pair| parse_selection(pair, pc, remaining_depth))
                 .collect::<Result<_>>()?,
         },
         pos,
     ))
 }
 
-fn parse_selection(pair: Pair<Rule>, pc: &mut PositionCalculator) -> Result<Positioned<Selection>> {
+fn parse_selection(
+    pair: Pair<Rule>,
+    pc: &mut PositionCalculator,
+    remaining_depth: usize,
+) -> Result<Positioned<Selection>> {
     debug_assert_eq!(pair.as_rule(), Rule::selection);
 
     let pos = pc.step(&pair);
     let pair = exactly_one(pair.into_inner());
 
     Ok(Positioned::new(
         match pair.as_rule() {
-            Rule::field => Selection::Field(parse_field(pair, pc)?),
+            Rule::field => Selection::Field(parse_field(pair, pc, remaining_depth)?),
             Rule::fragment_spread => Selection::FragmentSpread(parse_fragment_spread(pair, pc)?),
-            Rule::inline_fragment => Selection::InlineFragment(parse_inline_fragment(pair, pc)?),
+            Rule::inline_fragment => {
+                Selection::InlineFragment(parse_inline_fragment(pair, pc, remaining_depth)?)
+            }
             _ => unreachable!(),
         },
         pos,
     ))
 }
 
-fn parse_field(pair: Pair<Rule>, pc: &mut PositionCalculator) -> Result<Positioned<Field>> {
+fn parse_field(
+    pair: Pair<Rule>,
+    pc: &mut PositionCalculator,
+    remaining_depth: usize,
+) -> Result<Positioned<Field>> {
     debug_assert_eq!(pair.as_rule(), Rule::field);
 
     let pos = pc.step(&pair);
@@ -277,7 +296,7 @@ fn parse_field(pair: Pair<Rule>, pc: &mut PositionCalculator) -> Result<Position
     })?;
     let directives = parse_opt_directives(&mut pairs, pc)?;
     let selection_set = parse_if_rule(&mut pairs, Rule::selection_set, |pair| {
-        parse_selection_set(pair, pc)
+        parse_selection_set(pair, pc, recursion_depth!(remaining_depth))
     })?;
 
     debug_assert_eq!(pairs.next(), None);
@@ -325,6 +344,7 @@ fn parse_fragment_spread(
 fn parse_inline_fragment(
     pair: Pair<Rule>,
     pc: &mut PositionCalculator,
+    remaining_depth: usize,
 ) -> Result<Positioned<InlineFragment>> {
     debug_assert_eq!(pair.as_rule(), Rule::inline_fragment);
 
@@ -335,7 +355,8 @@ fn parse_inline_fragment(
         parse_type_condition(pair, pc)
     })?;
     let directives = parse_opt_directives(&mut pairs, pc)?;
-    let selection_set = parse_selection_set(pairs.next().unwrap(), pc)?;
+    let selection_set =
+        parse_selection_set(pairs.next().unwrap(), pc, recursion_depth!(remaining_depth))?;
 
     debug_assert_eq!(pairs.next(), None);
 
@@ -366,7 +387,7 @@ fn parse_fragment_definition_item(
     let name = parse_name(pairs.next().unwrap(), pc)?;
     let type_condition = parse_type_condition(pairs.next().unwrap(), pc)?;
     let directives = parse_opt_directives(&mut pairs, pc)?;
-    let selection_set = parse_selection_set(pairs.next().unwrap(), pc)?;
+    let selection_set = parse_selection_set(pairs.next().unwrap(), pc, MAX_RECURSION_DEPTH)?;
 
     debug_assert_eq!(pairs.next(), None);