fix: Limit body read size of remote requests (CWE-409)

Reviewed-By: Jade Ellis <jade@ellis.link>

src/core/utils/mod.rs

@@ -11,6 +11,7 @@ pub mod json;
 pub mod math;
 pub mod mutex_map;
 pub mod rand;
+pub mod response;
 pub mod result;
 pub mod set;
 pub mod stream;

src/core/utils/response.rs

@@ -0,0 +1,51 @@
+use futures::StreamExt;
+use num_traits::ToPrimitive;
+
+use crate::Err;
+
+/// Reads the response body while enforcing a maximum size limit to prevent
+/// memory exhaustion.
+pub async fn limit_read(response: reqwest::Response, max_size: u64) -> crate::Result<Vec<u8>> {
+	if response.content_length().is_some_and(|len| len > max_size) {
+		return Err!(BadServerResponse("Response too large"));
+	}
+	let mut data = Vec::new();
+	let mut reader = response.bytes_stream();
+
+	while let Some(chunk) = reader.next().await {
+		let chunk = chunk?;
+		data.extend_from_slice(&chunk);
+
+		if data.len() > max_size.to_usize().expect("max_size must fit in usize") {
+			return Err!(BadServerResponse("Response too large"));
+		}
+	}
+
+	Ok(data)
+}
+
+/// Reads the response body as text while enforcing a maximum size limit to
+/// prevent memory exhaustion.
+pub async fn limit_read_text(
+	response: reqwest::Response,
+	max_size: u64,
+) -> crate::Result<String> {
+	let text = String::from_utf8(limit_read(response, max_size).await?)?;
+	Ok(text)
+}
+
+#[allow(async_fn_in_trait)]
+pub trait LimitReadExt {
+	async fn limit_read(self, max_size: u64) -> crate::Result<Vec<u8>>;
+	async fn limit_read_text(self, max_size: u64) -> crate::Result<String>;
+}
+
+impl LimitReadExt for reqwest::Response {
+	async fn limit_read(self, max_size: u64) -> crate::Result<Vec<u8>> {
+		limit_read(self, max_size).await
+	}
+
+	async fn limit_read_text(self, max_size: u64) -> crate::Result<String> {
+		limit_read_text(self, max_size).await
+	}
+}