ngx::http::NgxListIterator: ngx_str_t items are NgxStr, not str

The ngx_str_items in the header name and value are often untrusted
input, and may not have utf-8 contents. The use of ngx_str_t::to_str
in this iterator will panic when the contents are not utf-8. So, instead
of yielding a pair of strs here, yield a pair of &NgxStr, which is like
ngx_str_t but with more methods.

Author: pchickey

examples/awssig.rs

@@ -286,8 +286,16 @@ http_request_handler!(awssigv4_header_handler, |request: &mut Request| {
         // Copy only headers that will be used to sign the request
         let mut headers = HeaderMap::new();
         for (name, value) in request.headers_in_iterator() {
-            if name.to_lowercase() == "host" {
-                headers.insert(http::header::HOST, value.parse().unwrap());
+            if let Ok(name) = name.to_str() {
+                if name.to_lowercase() == "host" {
+                    if let Ok(value) = http::HeaderValue::from_bytes(value.as_bytes()) {
+                        headers.insert(http::header::HOST, value);
+                    } else {
+                        return core::Status::NGX_DECLINED;
+                    }
+                }
+            } else {
+                return core::Status::NGX_DECLINED;
             }
         }
         headers.insert("X-Amz-Date", datetime_now.parse().unwrap());
@@ -313,12 +321,11 @@ http_request_handler!(awssigv4_header_handler, |request: &mut Request| {
     request.add_header_in("authorization", signature.as_str());
     request.add_header_in("X-Amz-Date", datetime_now.as_str());
 
-    // done signing, let's print values we have in request.headers_out, request.headers_in
     for (name, value) in request.headers_out_iterator() {
-        ngx_log_debug_http!(request, "headers_out {}: {}", name, value);
+        ngx_log_debug_http!(request, "headers_out {name}: {value}",);
     }
     for (name, value) in request.headers_in_iterator() {
-        ngx_log_debug_http!(request, "headers_in  {}: {}", name, value);
+        ngx_log_debug_http!(request, "headers_in  {name}: {value}",);
     }
 
     core::Status::NGX_OK

src/http/request.rs

@@ -462,7 +462,7 @@ impl<'a> Iterator for NgxListIterator<'a> {
     // something like pub struct Header(ngx_table_elt_t);
     // then header would have key and value
 
-    type Item = (&'a str, &'a str);
+    type Item = (&'a NgxStr, &'a NgxStr);
 
     fn next(&mut self) -> Option<Self::Item> {
         let part = self.part.as_mut()?;
@@ -478,7 +478,12 @@ impl<'a> Iterator for NgxListIterator<'a> {
         }
         let header = &part.arr[self.i];
         self.i += 1;
-        Some((header.key.to_str(), header.value.to_str()))
+        unsafe {
+            Some((
+                NgxStr::from_ngx_str(header.key),
+                NgxStr::from_ngx_str(header.value),
+            ))
+        }
     }
 }