sparesults: avoid stack overflow errors on too many nested triples

lib/oxrdf/src/parser.rs

@@ -8,6 +8,10 @@ use std::error::Error;
 use std::fmt;
 use std::str::{Chars, FromStr};
 
+/// This limit is set in order to avoid stack overflow error when parsing nested triples due to too many recursive calls.
+/// The actual limit value is a wet finger compromise between not failing to parse valid files and avoiding to trigger stack overflow errors.
+const MAX_NUMBER_OF_NESTED_TRIPLES: usize = 512;
+
 impl FromStr for NamedNode {
     type Err = TermParseError;
 
@@ -95,7 +99,7 @@ impl FromStr for Term {
     /// ).into());
     /// ```
     fn from_str(s: &str) -> Result<Self, TermParseError> {
-        let (term, left) = read_term(s)?;
+        let (term, left) = read_term(s, 0)?;
         if !left.is_empty() {
             return Err(TermParseError::msg("Invalid term serialization"));
         }
@@ -293,12 +297,17 @@ fn read_literal(s: &str) -> Result<(Literal, &str), TermParseError> {
     }
 }
 
-fn read_term(s: &str) -> Result<(Term, &str), TermParseError> {
+fn read_term(s: &str, number_of_recursive_calls: usize) -> Result<(Term, &str), TermParseError> {
     let s = s.trim();
     if let Some(remain) = s.strip_prefix("<<") {
-        let (subject, remain) = read_term(remain)?;
+        if number_of_recursive_calls == MAX_NUMBER_OF_NESTED_TRIPLES {
+            return Err(TermParseError::msg(
+                "Too many nested triples. The parser fails here to avoid a stack overflow.",
+            ));
+        }
+        let (subject, remain) = read_term(remain, number_of_recursive_calls + 1)?;
         let (predicate, remain) = read_named_node(remain)?;
-        let (object, remain) = read_term(remain)?;
+        let (object, remain) = read_term(remain, number_of_recursive_calls + 1)?;
         let remain = remain.trim_start();
         if let Some(remain) = remain.strip_prefix(">>") {
             #[cfg(feature = "rdf-star")]

lib/sparesults/src/csv.rs

@@ -326,17 +326,18 @@ mod tests {
     }
 
     #[test]
-    fn test_bad_tsv() -> io::Result<()> {
-        let bad_tsvs = vec![
+    fn test_bad_tsv() {
+        let mut bad_tsvs = vec![
             "?", "?p", "?p?o", "?p\n<", "?p\n_", "?p\n_:", "?p\n\"", "?p\n<<",
         ];
+        let a_lot_of_strings = format!("?p\n{}\n", "<".repeat(100_000));
+        bad_tsvs.push(&a_lot_of_strings);
         for bad_tsv in bad_tsvs {
-            if let TsvQueryResultsReader::Solutions { mut solutions, .. } =
-                TsvQueryResultsReader::read(Cursor::new(bad_tsv))?
+            if let Ok(TsvQueryResultsReader::Solutions { mut solutions, .. }) =
+                TsvQueryResultsReader::read(Cursor::new(bad_tsv))
             {
-                while solutions.read_next()?.is_some() {}
+                while let Ok(Some(_)) = solutions.read_next() {}
             }
         }
-        Ok(())
     }
 }

lib/sparesults/src/json.rs

@@ -8,6 +8,10 @@ use oxrdf::*;
 use std::collections::BTreeMap;
 use std::io::{self, BufRead, Write};
 
+/// This limit is set in order to avoid stack overflow error when parsing nested triples due to too many recursive calls.
+/// The actual limit value is a wet finger compromise between not failing to parse valid files and avoiding to trigger stack overflow errors.
+const MAX_NUMBER_OF_NESTED_TRIPLES: usize = 256;
+
 pub fn write_boolean_json_result<W: Write>(sink: W, value: bool) -> io::Result<W> {
     let mut writer = JsonWriter::from_writer(sink);
     writer.write_event(JsonEvent::StartObject)?;
@@ -239,14 +243,21 @@ impl<R: BufRead> JsonSolutionsReader<R> {
                             key
                         ))
                     })?;
-                    new_bindings[k] = Some(self.read_value()?)
+                    new_bindings[k] = Some(self.read_value(0)?)
                 }
                 _ => return Err(SyntaxError::msg("Invalid result serialization").into()),
             }
         }
     }
 
-    fn read_value(&mut self) -> Result<Term, ParseError> {
+    fn read_value(&mut self, number_of_recursive_calls: usize) -> Result<Term, ParseError> {
+        if number_of_recursive_calls == MAX_NUMBER_OF_NESTED_TRIPLES {
+            return Err(SyntaxError::msg(format!(
+                "Too many nested triples ({}). The parser fails here to avoid a stack overflow.",
+                MAX_NUMBER_OF_NESTED_TRIPLES
+            ))
+            .into());
+        }
         enum Type {
             Uri,
             BNode,
@@ -279,9 +290,11 @@ impl<R: BufRead> JsonSolutionsReader<R> {
                     "value" => state = Some(State::Value),
                     "xml:lang" => state = Some(State::Lang),
                     "datatype" => state = Some(State::Datatype),
-                    "subject" => subject = Some(self.read_value()?),
-                    "predicate" => predicate = Some(self.read_value()?),
-                    "object" => object = Some(self.read_value()?),
+                    "subject" => subject = Some(self.read_value(number_of_recursive_calls + 1)?),
+                    "predicate" => {
+                        predicate = Some(self.read_value(number_of_recursive_calls + 1)?)
+                    }
+                    "object" => object = Some(self.read_value(number_of_recursive_calls + 1)?),
                     _ => {
                         return Err(SyntaxError::msg(format!(
                             "Unexpected key in term serialization: '{}'",