allow configurable forbidden header

When the HTTP library is not used as a proxy, removing of the
forbidden headers by default may not make sense. This change makes it
configurable via the `WasiHttpView`, which keeps the default behavior.

Author: xofyarg

crates/wasi-http/src/types.rs

@@ -121,8 +121,8 @@ pub trait WasiHttpView: IoView {
     }
 
     /// Whether a given header should be considered forbidden and not allowed.
-    fn is_forbidden_header(&mut self, _name: &HeaderName) -> bool {
-        false
+    fn is_forbidden_header(&mut self, name: &HeaderName) -> bool {
+        is_default_forbidden_header(name)
     }
 
     /// Number of distinct write calls to the outgoing body's output-stream
@@ -269,8 +269,8 @@ impl<T: WasiHttpView> WasiHttpView for WasiHttpImpl<T> {
     }
 }
 
-/// Returns `true` when the header is forbidden according to this [`WasiHttpView`] implementation.
-pub(crate) fn is_forbidden_header(view: &mut dyn WasiHttpView, name: &HeaderName) -> bool {
+/// Returns `true` when the header is forbidden according to the default list.
+pub(crate) fn is_default_forbidden_header(name: &HeaderName) -> bool {
     static FORBIDDEN_HEADERS: [HeaderName; 9] = [
         hyper::header::CONNECTION,
         HeaderName::from_static("keep-alive"),
@@ -283,7 +283,7 @@ pub(crate) fn is_forbidden_header(view: &mut dyn WasiHttpView, name: &HeaderName
         HeaderName::from_static("http2-settings"),
     ];
 
-    FORBIDDEN_HEADERS.contains(name) || view.is_forbidden_header(name)
+    FORBIDDEN_HEADERS.contains(name)
 }
 
 /// Removes forbidden headers from a [`hyper::HeaderMap`].
@@ -292,7 +292,7 @@ pub(crate) fn remove_forbidden_headers(
     headers: &mut hyper::HeaderMap,
 ) {
     let forbidden_keys = Vec::from_iter(headers.keys().filter_map(|name| {
-        if is_forbidden_header(view, name) {
+        if view.is_forbidden_header(name) {
             Some(name.clone())
         } else {
             None

crates/wasi-http/src/types_impl.rs

@@ -7,7 +7,7 @@ use crate::{
     types::{
         FieldMap, HostFields, HostFutureIncomingResponse, HostIncomingRequest,
         HostIncomingResponse, HostOutgoingRequest, HostOutgoingResponse, HostResponseOutparam,
-        is_forbidden_header, remove_forbidden_headers,
+        remove_forbidden_headers,
     },
 };
 use anyhow::{Context, anyhow};
@@ -125,7 +125,7 @@ where
                 Err(_) => return Ok(Err(types::HeaderError::InvalidSyntax)),
             };
 
-            if is_forbidden_header(self, &header) {
+            if self.is_forbidden_header(&header) {
                 return Ok(Err(types::HeaderError::Forbidden));
             }
 
@@ -196,7 +196,7 @@ where
             Err(_) => return Ok(Err(types::HeaderError::InvalidSyntax)),
         };
 
-        if is_forbidden_header(self, &header) {
+        if self.is_forbidden_header(&header) {
             return Ok(Err(types::HeaderError::Forbidden));
         }
 
@@ -228,7 +228,7 @@ where
             Err(_) => return Ok(Err(types::HeaderError::InvalidSyntax)),
         };
 
-        if is_forbidden_header(self, &header) {
+        if self.is_forbidden_header(&header) {
             return Ok(Err(types::HeaderError::Forbidden));
         }
 
@@ -248,7 +248,7 @@ where
             Err(_) => return Ok(Err(types::HeaderError::InvalidSyntax)),
         };
 
-        if is_forbidden_header(self, &header) {
+        if self.is_forbidden_header(&header) {
             return Ok(Err(types::HeaderError::Forbidden));
         }