daemon/http: HTTP response codes

Fixes #728 (closed)

Related #618 (closed)

Currently:

• Replies with 400 when a GET query has no DNS query in it (the basic case in #728 (closed))
• Replies with 404 when querying unknown endpoints (anything other than /doh or /dns-query)
• Replies with 431 when a header is too large

To do:

• Reply with 400 when the POST body is malformed (but only if DNS itself cannot deal with it, then it is 200 as per RFC 8484)
• Reply with 413 when the POST body is too long (attempted but not working at the moment) (changed to 400)
• Reply with 414 when the GET URL is too long (changed to 400)
• Check RFCs for more codes
• Make sure the way it's currently simply calling http_send_response on error does not cause any problems
• Possibly more?

daemon/http.c

@@ -58,6 +58,7 @@ enum http_status {
 	HTTP_STATUS_NOT_FOUND                       = 404,
 	HTTP_STATUS_PAYLOAD_TOO_LARGE               = 413,
 	HTTP_STATUS_REQUEST_HEADER_FIELDS_TOO_LARGE = 431,
+	HTTP_STATUS_NOT_IMPLEMENTED                 = 501,
 };
 
 struct http_data {
@@ -201,7 +202,7 @@ static int check_uri(const char* uri_path)
 	}
 
 	if (ret) /* no endpoint found */
-		return -1;
+		return kr_error(ENOENT);
 
 	/* FIXME This also passes for GET when no variables are provided.
 	 * Fixing it doesn't seem straightforward, since :method may not be
@@ -367,9 +368,8 @@ static int header_callback(nghttp2_session *h2, const nghttp2_frame *frame,
 				kr_log_debug(DOH,
 					"[%p] stream %d: header too large (%zu B), refused\n",
 					(void *)h2, stream_id, valuelen);
-				http_send_response(ctx, stream_id, NULL,
+				return http_send_response(ctx, stream_id, NULL,
 						HTTP_STATUS_REQUEST_HEADER_FIELDS_TOO_LARGE);
-				return 0;
 			}
 
 			/* Copy the user-provided header name to keep the original case. */
@@ -387,9 +387,11 @@ static int header_callback(nghttp2_session *h2, const nghttp2_frame *frame,
 	}
 
 	if (!strcasecmp(":path", (const char *)name)) {
-		if (check_uri((const char *)value) < 0) {
-			http_send_response(ctx, stream_id, NULL, HTTP_STATUS_NOT_FOUND);
-			return 0;
+		int uri_result = check_uri((const char *)value);
+		if (uri_result == kr_error(ENOENT)) {
+			return http_send_response(ctx, stream_id, NULL, HTTP_STATUS_NOT_FOUND);
+		} else if (uri_result < 0) {
+			return http_send_response(ctx, stream_id, NULL, HTTP_STATUS_BAD_REQUEST);
 		}
 
 		kr_assert(ctx->uri_path == NULL);
@@ -405,8 +407,11 @@ static int header_callback(nghttp2_session *h2, const nghttp2_frame *frame,
 			ctx->current_method = HTTP_METHOD_GET;
 		} else if (!strcasecmp("post", (const char *)value)) {
 			ctx->current_method = HTTP_METHOD_POST;
+		} else if (!strcasecmp("head", (const char *)value)) {
+			ctx->current_method = HTTP_METHOD_HEAD;
 		} else {
 			ctx->current_method = HTTP_METHOD_NONE;
+			return http_send_response(ctx, stream_id, NULL, HTTP_STATUS_NOT_IMPLEMENTED);
 		}
 	}
 
@@ -491,7 +496,9 @@ static int submit_to_wirebuffer(struct http_ctx *ctx, int32_t stream_id)
 	len = ctx->buf_pos - sizeof(uint16_t);
 	if (len <= 0 || len > KNOT_WIRE_MAX_PKTSIZE) {
 		kr_log_debug(DOH, "[%p] invalid dnsmsg size: %zd B\n", (void *)ctx->h2, len);
-		http_send_response(ctx, stream_id, NULL, HTTP_STATUS_PAYLOAD_TOO_LARGE);
+		http_send_response(ctx, stream_id, NULL, (len <= 0)
+				? HTTP_STATUS_BAD_REQUEST
+				: HTTP_STATUS_PAYLOAD_TOO_LARGE);
 		ret = -1;
 		goto cleanup;
 	}
@@ -523,10 +530,10 @@ static int on_frame_recv_callback(nghttp2_session *h2, const nghttp2_frame *fram
 		return NGHTTP2_ERR_CALLBACK_FAILURE;
 
 	if ((frame->hd.flags & NGHTTP2_FLAG_END_STREAM) && ctx->incomplete_stream == stream_id) {
-		if (ctx->current_method == HTTP_METHOD_GET) {
+		if (ctx->current_method == HTTP_METHOD_GET || ctx->current_method == HTTP_METHOD_HEAD) {
 			if (process_uri_path(ctx, ctx->uri_path, stream_id) < 0) {
-				http_send_response(ctx, stream_id, NULL, HTTP_STATUS_BAD_REQUEST);
-				return 0;  /* End processing - don't submit to wirebuffer. */
+				/* End processing - don't submit to wirebuffer. */
+				return http_send_response(ctx, stream_id, NULL, HTTP_STATUS_BAD_REQUEST);
 			}
 		}
 
@@ -735,6 +742,13 @@ static int http_send_response(struct http_ctx *ctx, int32_t stream_id,
 	auto_free char *size = NULL;
 	auto_free char *max_age = NULL;
 
+	if (ctx->current_method == HTTP_METHOD_HEAD && prov) {
+		/* HEAD method is the same as GET but only returns headers,
+		 * so let's clean up the data here as we don't need it. */
+		free(prov->source.ptr);
+		prov = NULL;
+	}
+
 	if (prov) {
 		data = (struct http_data*)prov->source.ptr;
 		const char *directive_max_age = "max-age=";
@@ -783,6 +797,10 @@ static int http_send_response(struct http_ctx *ctx, int32_t stream_id,
 		return 0;
 	}
 
+	if (status != HTTP_STATUS_OK) {
+		nghttp2_submit_rst_stream(h2, NGHTTP2_FLAG_NONE, stream_id, NGHTTP2_NO_ERROR);
+	}
+
 	return 0;
 }