feature: ssl.create_ctx and tcp:setsslctx

[detailyang]

This is a sister PR at lua-nginx-module/pull/997.

I refer to Node.js JS Design as a guide. Now the API is the fowllong:

local ssl = require "ngx.ssl"
local ctx, err = ssl.create_ctx{
    method = "SSLv23_method", #default SSLv23_method
    cert = "pem-data", #parsed by ssl.parse_pem_cert
    priv_key = "pem-data", #parsed by ssl.parse_pem_priv_key
}

if ctx ~= nil then
    return error("create ssl ctx error" .. err)
end

-- we can cache the ctx object in a cache like lua-resty-lrucache

local sock = ngx.socket.tcp()
local ok, err = sock:setsslctx(ctx) #the setsslctx is a Lua function atop FFI whcich been implement on lua-resty-core
sock:sslhandshake(...)

Now we proivde 3 arguments as the follwoing to feed SSL_CTX object.

• method
  Openssl protocols are listed as OPENSSL PROTOCOL METHODS
• cert
  Optional certificate in PEM format which can be parsed by ssl.parse_pem_cert
• priv_key
  Optional private keys in PEM format which can be parsed by ssl.parse_pem_priv_key

It 's convenient that if we want to expose more arguments to user in future if we want.

Now it is not ready to provide the README document. when we agree on the API Design, I will provide.

@agentzh @thibaultcha @doujiang24

Can have a look at this PR ? Many thanks :D

[detailyang]

After refactor the codebase, these is a little different things. We remove the method argument, and provide the protocols argument. The protocols argument is the SSL.PROTOCOL_SSLv2|PROTOCOL_SSLv3|PROTOCOL_TLSv1|PROTOCOL_TLSv1_1|PROTOCOL_TLSv1_2

[doujiang24]

bor can accept multiple arguments, like:

resty -e " ngx.say(bit.bor(1, 2, 4)); "
7

[detailyang]

gotcha

[doujiang24]

I think local protocols = options.protocols or options.protocols can be simpler :)

[detailyang]

gotcha local protocols = options.protocols or default_protocols

[doujiang24]

better use nil instead false here?

[detailyang]

Agree. I found other statements is also using nil rather than false.

[detailyang]

Now the CI failed since the newest luacheck ignore the custom API of coroutine.

I create a PR to supplement these API or we can specify the older version of luacheck in travis.yml

[detailyang]

CI passed after merge newest commit on master branch :D

[agentzh]

Better put a blank line before this line for aesthetic considerations.

[agentzh]

Please be consistent with the style in lib/ngx/ssl.lua.

[agentzh]

You know that we can safely omit the parentheses here?

[agentzh]

We do not need to assign to ctx here.

[agentzh]

I thikn we can just omit the PROTOCOL_ prefix from these keys. They are not really needed IMHO.

[detailyang]

Fix the issue as the following and rebase the newest codebase:

• omit prefix PROTOCOL
• alignment
• no need to assign ctx again after ffi_gc
• omit parentheses only one argument

Sorry for duplicated commits because of wrong usage of git rebase