【DISCUSS】Add CORS Plugin

[li dequan]

Hi:

Add a CORS plugin to APISIX.

The following is the code of the cors plugin

--
-- Created by IntelliJ IDEA.
-- User: lidequan
-- Date: 2019-10-10
-- Time: 20:40
-- To change this template use File | Settings | File Templates.
--
local func = require("apisix.libs.func")
local core = require("apisix.core")
local ngx = require("ngx")

local schema = {
    type = "object",
    properties = {
        enable = { type = "boolean", default = true, enum = { true, false } },
        origin = {
            description = "Access-Control-Allow-Origin",
            type = "string",
            default = "*", -- 秒
        },
        methods = {
            description = "Access-Control-Allow-method",
            type = "string",
            default='GET, POST, OPTIONS, DELETE, PATCH, HEAD, CONNECT, TRACE',
        },
        headers = {
            description = "Access-Control-Allow-Headers",
            type   = "string",
            default = 
"DNT,X-Mx-ReqToken,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Authorization"
        },
        credentials ={
            description = "Access-Control-Allow-Credentials",
            type = "boolean",
            default = true,
            enum = { true, false }
        }
    }
}

local plugin_name = "odin-cors"

local _M = {
    version = 0.1,
    priority = 2901,
    name = plugin_name,
    schema = schema,
}

function _M.check_schema(conf)
    local ok, err = core.schema.check(schema, conf)

    if not ok then
        return false, err
    end

    return true
end

function _M.access(conf, ctx)
    if not conf.enable then
        return
    end

    local access_control_vars = {
        methods = "Access-Control-Allow-Methods",
        headers = "Access-Control-Allow-Headers",
        credentials = "Access-Control-Allow-Credentials"
    }

    -- 设置origin
    if not func.empty(conf.origin) then
        local headers = ngx.req.get_headers()
        if not func.empty(headers.origin) then
            local from, _, _ = ngx.re.find(conf.origin, headers.origin)
            if from then
                core.response.set_header("Access-Control-Allow-Origin", 
headers.origin)
            end
        end
    end

    for key, name in pairs(access_control_vars) do
        if conf[key] then
            core.response.set_header(name, conf[key])
        end
    end

end

return _M