feat: grpc-web plugin supports trailers as part of response body

apisix/plugins/grpc-web.lua

@@ -13,45 +13,64 @@
 -- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 -- See the License for the specific language governing permissions and
 -- limitations under the License.
-
-local ngx               = ngx
-local ngx_arg           = ngx.arg
-local core              = require("apisix.core")
-local req_set_uri       = ngx.req.set_uri
+local ngx = ngx
+local ngx_arg = ngx.arg
+local core = require("apisix.core")
+local req_set_uri = ngx.req.set_uri
 local req_set_body_data = ngx.req.set_body_data
-local decode_base64     = ngx.decode_base64
-local encode_base64     = ngx.encode_base64
-
+local decode_base64 = ngx.decode_base64
+local encode_base64 = ngx.encode_base64
 
 local ALLOW_METHOD_OPTIONS = "OPTIONS"
 local ALLOW_METHOD_POST = "POST"
 local CONTENT_ENCODING_BASE64 = "base64"
 local CONTENT_ENCODING_BINARY = "binary"
 local DEFAULT_CORS_ALLOW_ORIGIN = "*"
-local DEFAULT_CORS_ALLOW_METHODS = ALLOW_METHOD_POST
-local DEFAULT_CORS_ALLOW_HEADERS = "content-type,x-grpc-web,x-user-agent"
+local DEFAULT_CORS_ALLOW_METHODS = "POST, OPTIONS"
+local DEFAULT_CORS_ALLOW_HEADERS = "content-type,x-grpc-web,x-user-agent,grpc-accept-encoding"
 local DEFAULT_PROXY_CONTENT_TYPE = "application/grpc"
+local DEFAULT_CORS_ALLOW_EXPOSE_HEADERS = "grpc-status,grpc-message"
+
+local GRPC_WEB_TRAILER_FRAME_HEADER = string.char(128, 0, 0, 0)
+local GRPC_WEB_REQ_TRAILERS_DEFAULT = {
+    ["grpc-status"] = "0",
+    ["grpc-message"] = "OK"
+}
 
+local CRLF = "\r\n"
 
 local plugin_name = "grpc-web"
 
 local schema = {
     type = "object",
-    properties = {},
+    properties = {
+        strip_path = {
+            description = "include prefix matched by path pattern in the path used for " ..
+                "upstream call, appropriate for prefix matching path " ..
+                "patterns with the format <package>.<service>/*",
+            type = "boolean",
+            default = false
+        },
+        enable_in_body_trailers_on_success = {
+            description = "append standard grpc-web in-body trailers frame in response body",
+            type = "boolean",
+            default = false
+        }
+    }
 }
 
 local grpc_web_content_encoding = {
     ["application/grpc-web"] = CONTENT_ENCODING_BINARY,
     ["application/grpc-web-text"] = CONTENT_ENCODING_BASE64,
     ["application/grpc-web+proto"] = CONTENT_ENCODING_BINARY,
-    ["application/grpc-web-text+proto"] = CONTENT_ENCODING_BASE64,
+    ["application/grpc-web-text+proto"] = CONTENT_ENCODING_BASE64
 }
 
 local _M = {
     version = 0.1,
     priority = 505,
     name = plugin_name,
-    schema = schema,
+    schema = schema
 }
 
 function _M.check_schema(conf)
@@ -87,11 +106,18 @@ function _M.access(conf, ctx)
     -- set grpc path
     if not (ctx.curr_req_matched and ctx.curr_req_matched[":ext"]) then
         core.log.error("routing configuration error, grpc-web plugin only supports ",
-                       "`prefix matching` pattern routing")
+            "`prefix matching` pattern routing")
         return 400
     end
 
-    local path = ctx.curr_req_matched[":ext"]
+    local path
+    if conf.strip_path and ctx.curr_req_matched._path:byte(-1) == core.string.byte("*") and
+        ctx.curr_req_matched[":ext"]:byte(1) ~= core.string.byte("/") then
+        path = string.sub(ctx.curr_req_matched._path, 1, -2) .. ctx.curr_req_matched[":ext"]
+    else
+        path = ctx.curr_req_matched[":ext"]
+    end
+
     if path:byte(1) ~= core.string.byte("/") then
         path = "/" .. path
     end
@@ -129,24 +155,47 @@ function _M.header_filter(conf, ctx)
     if not ctx.cors_allow_origins then
         core.response.set_header("Access-Control-Allow-Origin", DEFAULT_CORS_ALLOW_ORIGIN)
     end
+    core.response.set_header("Access-Control-Expose-Headers", DEFAULT_CORS_ALLOW_EXPOSE_HEADERS)
     core.response.set_header("Content-Type", ctx.grpc_web_mime)
+    core.response.clear_header_as_body_modified()
 end
 
 function _M.body_filter(conf, ctx)
     -- If the MIME extension type description of the gRPC-Web standard is not obtained,
     -- indicating that the request is not based on the gRPC Web specification,
     -- the processing of the request body will be ignored
+    -- If response body is not empty, in-body trailers required by gRPC-Web
+    -- are added to the end of response body
     -- https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-WEB.md
     -- https://github.com/grpc/grpc-web/blob/master/doc/browser-features.md#cors-support
     if not ctx.grpc_web_mime then
         return
     end
 
+    if conf.enable_in_body_trailers_on_success then
+        local response = core.response.hold_body_chunk(ctx)
+        if response and string.len(response) ~= 0 then
+            local headers = ngx.resp.get_headers()
+            local trailers = " "
+            for trailer_key, trailer_default_value in pairs(GRPC_WEB_REQ_TRAILERS_DEFAULT) do
+                local trailer_value = headers[trailer_key]
+
+                if trailer_value == nil then
+                    trailer_value = trailer_default_value
+                end
+
+                trailers = trailers .. trailer_key .. ":" .. trailer_value .. CRLF
+            end
+
+            response = response .. GRPC_WEB_TRAILER_FRAME_HEADER .. trailers
+            ngx_arg[1] = response
+        end
+    end
+
     if ctx.grpc_web_encoding == CONTENT_ENCODING_BASE64 then
         local chunk = ngx_arg[1]
         chunk = encode_base64(chunk)
         ngx_arg[1] = chunk
     end
 end
-
 return _M

t/plugin/grpc-web.t

@@ -95,8 +95,8 @@ node ./t/plugin/grpc-web/client.js TEXT STREAM
 OPTIONS /grpc/web/a6.RouteService/GetRoute
 --- error_code: 204
 --- response_headers
-Access-Control-Allow-Methods: POST
-Access-Control-Allow-Headers: content-type,x-grpc-web,x-user-agent
+Access-Control-Allow-Methods: POST, OPTIONS
+Access-Control-Allow-Headers: content-type,x-grpc-web,x-user-agent,grpc-accept-encoding
 Access-Control-Allow-Origin: *
 
 
@@ -227,3 +227,17 @@ Content-Type: application/grpc-web
 --- response_headers
 Access-Control-Allow-Origin: http://test.com
 Content-Type: application/grpc-web
+
+
+
+=== TEST 11: grpc-web access control expose headers for non grpc servers that don't implement grpc-web
+--- request
+POST /grpc/web/a6.RouteService/GetRoute
+{}
+--- more_headers
+Origin: http://test.com
+Content-Type: application/grpc-web
+--- response_headers
+Access-Control-Allow-Origin: http://test.com
+Content-Type: application/grpc-web
+Access-Control-Expose-Headers: grpc-status,grpc-message