lua-resty-acme

Automatic Let's Encrypt certificate serving (RSA + ECC) and pure Lua implementation of the ACMEv2 protocol.

http-01 and tls-alpn-01 challenges are supported.

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Table of Contents

• Description
• Status
• Synopsis
• TODO
• Copyright and License
• See Also

Description

This library consists of two parts:

• resty.acme.autossl: automatic lifecycle management of Let's Encrypt certificates
• resty.acme.client: Lua implementation of ACME v2 protocol

Install using opm:

opm install fffonion/lua-resty-acme

Alternatively, to install using luarocks:

luarocks install lua-resty-acme
# manually install a luafilesystem
luarocks install luafilesystem

Note you will need to manually install luafilesystem when using LuaRocks. This is made to maintain backward compatibility.

This library uses an FFI-based openssl backend, which currently supports OpenSSL 1.1.1, 1.1.0 and 1.0.2 series.

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Status

Production.

Synopsis

Create account private key and fallback certs:

# create account key
openssl genpkey -algorithm RSA -pkeyopt rsa_keygen_bits:4096 -out /etc/openresty/account.key
# create fallback cert and key
openssl req -newkey rsa:2048 -nodes -keyout /etc/openresty/default.key -x509 -days 365 -out /etc/openresty/default.pem

Use the following example config:

events {}

http {
    resolver 8.8.8.8 ipv6=off;

    lua_shared_dict acme 16m;

    init_by_lua_block {
        require("resty.acme.autossl").init({
            -- setting the following to true
            -- implies that you read and accepted https://letsencrypt.org/repository/
            tos_accepted = true,
            -- uncomment following for first time setup
            -- staging = true,
            -- uncomment folloing to enable RSA + ECC double cert
            -- domain_key_types = { 'rsa', 'ecc' },
            -- uncomment following to enable tls-alpn-01 challenge
            -- enabled_challenge_handlers = { 'http-01', 'tls-alpn-01' },
            account_key_path = "/etc/openresty/account.key",
            account_email = "youemail@youdomain.com",
            domain_whitelist = { "example.com" },
        })
    }

    init_worker_by_lua_block {
        require("resty.acme.autossl").init_worker()
    }

    server {
        listen 80;
        listen 443 ssl;
        server_name example.com;

        # required to verify Let's Encrypt API
        lua_ssl_trusted_certificate /etc/ssl/certs/ca-certificates.crt;
        lua_ssl_verify_depth 2;

        # fallback certs, make sure to create them before hand
        ssl_certificate /etc/openresty/default.pem;
        ssl_certificate_key /etc/openresty/default.key;

        ssl_certificate_by_lua_block {
            require("resty.acme.autossl").ssl_certificate()
        }

        location /.well-known {
            content_by_lua_block {
                require("resty.acme.autossl").serve_http_challenge()
            }
        }
    }
}

When testing deployment, it's recommanded to uncomment the staging = true to allow an end-to-end test of your environment. This can avoid configuration failure result into too many requests that hits rate limiting on Let's Encrypt API.

By default autossl only creates RSA certificates. To use ECC certificates or both, uncomment domain_key_types = { 'rsa', 'ecc' }. Note that multiple certificate chain is only supported by NGINX 1.11.0 or later.

A certificate will be queued to create after Nginx seen request with such SNI, which might take tens of seconds to finish. During the meantime, requests with such SNI are responsed with the fallback certificate.

Note that domain_whitelist or domain_whitelist_callback must be set to include your domain that you wish to server autossl, to prevent potential abuse using fake SNI in SSL handshake. domain_whitelist defines a table that includes all domains should be included, and domain_whitelist_callback defines a function that accepts domain as parameter and return boolean to indicate if it should be included.

domain_whitelist = { "domain1.com", "domain2.com", "domain3.com" },

To match a pattern in your domain name, for example all subdomains under example.com, use:

domain_whitelist_callback = function(domain)
    return ngx.re.match(domain, [[\.example\.com$]], "jo")
end

Furthermore, since checking domain whitelist is running in certificate phase. It's possible to use cosocket API here. Do note that this will increase the SSL handshake latency.

domain_whitelist_callback = function(domain)
    -- send HTTP request
    local http = require("resty.http")
    local res, err = httpc:request_uri("http://example.com")
    -- access the storage
    local value, err = require("resty.acme.autossl").storage:get("key")
    -- do something to check the domain
    -- return is_domain_included
end}),

tls-alpn-01 challenge

tls-alpn-01 challenge is currently supported on Openresty 1.15.8.x and 1.17.8.x.

Click to expand sample config

events {}

http {
    resolver 8.8.8.8 ipv6=off;

    lua_shared_dict acme 16m;
    lua_shared_dict autossl_events 128k;

    init_by_lua_block {
        require("resty.acme.autossl").init({
            -- setting the following to true
            -- implies that you read and accepted https://letsencrypt.org/repository/
            tos_accepted = true,
            -- uncomment following for first time setup
            -- staging = true,
            -- uncomment folloing to enable RSA + ECC double cert
            -- domain_key_types = { 'rsa', 'ecc' },
            -- uncomment following to enable tls-alpn-01 challenge
            enabled_challenge_handlers = { 'http-01', 'tls-alpn-01' },
            account_key_path = "/etc/openresty/account.key",
            account_email = "youemail@youdomain.com",
            domain_whitelist = { "example.com" },
            storage_adapter = "file",
        })
    }
    init_worker_by_lua_block {
        require("resty.acme.autossl").init_worker()
    }

    # required to verify Let's Encrypt API
    lua_ssl_trusted_certificate /etc/ssl/certs/ca-certificates.crt;
    lua_ssl_verify_depth 2;

    server {
        listen 80;
        listen unix:/tmp/nginx-default.sock ssl;
        # listen unix:/tmp/nginx-default.sock ssl proxy_protocol;
        server_name example.com;

        # set_real_ip_from unix:;
        # real_ip_header proxy_protocol;

        # fallback certs, make sure to create them before hand
        ssl_certificate /etc/openresty/default.pem;
        ssl_certificate_key /etc/openresty/default.key;

        ssl_certificate_by_lua_block {
            require("resty.acme.autossl").ssl_certificate()
        }

        location /.well-known {
            content_by_lua_block {
                require("resty.acme.autossl").serve_http_challenge()
            }
        }
    }
}

stream {
    lua_shared_dict autossl_events 128k;
    init_worker_by_lua_block {

        require("resty.acme.autossl").init({
            -- setting the following to true
            -- implies that you read and accepted https://letsencrypt.org/repository/
            tos_accepted = true,
            -- uncomment following for first time setup
            -- staging = true,
            -- uncomment folloing to enable RSA + ECC double cert
            -- domain_key_types = { 'rsa', 'ecc' },
            -- uncomment following to enable tls-alpn-01 challenge
            enabled_challenge_handlers = { 'http-01', 'tls-alpn-01' },
            account_key_path = "/etc/openresty/account.key",
            account_email = "youemail@youdomain.com",
            domain_whitelist = { "example.com" },
            storage_adapter = "file"
        })
        require("resty.acme.autossl").init_worker()
    }

    map $ssl_preread_alpn_protocols $backend {
        ~\bacme-tls/1\b unix:/tmp/nginx-tls-alpn.sock;
        default unix:/tmp/nginx-default.sock;
    }

    server {
            listen 443;
            listen [::]:443;

            ssl_preread on;
            proxy_pass $backend;

            # proxy_protocol on;
    }

    server {
            listen unix:/tmp/nginx-tls-alpn.sock ssl;
            # listen nix:/tmp/nginx-tls-alpn.sock ssl proxy_protocol;
            ssl_certificate certs/default.pem;
            ssl_certificate_key certs/default.key;

            # requires --with-stream_realip_module
            # set_real_ip_from unix:;

            ssl_certificate_by_lua_block {
                    require("resty.acme.autossl").serve_tls_alpn_challenge()
            }

            content_by_lua_block {
                    ngx.exit(0)
            }
    }
}

In the above sample config, we set a http server and two stream server.

The very front stream server listens for 443 port and route to different upstream based on client ALPN. The tls-alpn-01 responder listens on unix:/tmp/nginx-tls-alpn.sock. All normal https traffic listens on unix:/tmp/nginx-default.sock.

                                                [stream server unix:/tmp/nginx-tls-alpn.sock ssl]
                                            Y / 
[stream server 443] --- ALPN is acme-tls ?
                                            N \
                                                [http server unix:/tmp/nginx-default.sock ssl]

• The config passed to require("resty.acme.autossl").init in both subsystem should be kept same as possible.
• tls-alpn-01 challenge handler doesn't need any third party dependency.
• You can enable http-01 and tls-alpn-01 challenge handlers at the same time.
• http and stream subsystem doesn't share shm, thus considering use a storage other than shm. If you must use shm, you will need to apply this patch.
• tls-alpn-01 challenge handler is considered experiemental.

resty.acme.autossl

A config table can be passed to resty.acme.autossl.init(), the default values are:

default_config = {
  -- accept term of service https://letsencrypt.org/repository/
  tos_accepted = false,
  -- if using the let's encrypt staging API
  staging = false,
  -- the path to account private key in PEM format
  account_key_path = nil,
  -- the account email to register
  account_email = nil,
  -- number of certificate cache, per type
  cache_size = 100,
  domain_key_paths = {
    -- the global domain RSA private key
    rsa = nil,
    -- the global domain ECC private key
    ecc = nil,
  },
  -- the private key algorithm to use, can be one or both of
  -- 'rsa' and 'ecc'
  domain_key_types = { 'rsa' },
  -- restrict registering new cert only with domain defined in this table
  domain_whitelist = nil,
  -- restrict registering new cert only with domain checked by this function
  domain_whitelist_callback = nil,
  -- the threshold to renew a cert before it expires, in seconds
  renew_threshold = 7 * 86400,
  -- interval to check cert renewal, in seconds
  renew_check_interval = 6 * 3600,
  -- the store certificates
  storage_adapter = "shm",
  -- the storage config passed to storage adapter
  storage_config = {
    shm_name = 'acme',
  },
}

If account_key_path is not specified, a new account key will be created everytime Nginx reloads configuration. Note this may trigger New Account rate limiting on Let's Encrypt API.

If domain_key_paths is not specified, a new private key will be generated for each certificate (4096-bits RSA and 256-bits prime256v1 ECC). Note that generating such key will block worker and will be especially noticable on VMs where entropy is low.

See also Storage Adapters below.

autossl.get_certkey

syntax: certkey, err = autossl.get_certkey(domain, type?)

Return the PEM-encoded certificate and private key for domain from storage. Optionally accepts a type parameter which can be "rsa" or "ecc"; if omitted, type will default to "rsa".

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resty.acme.client

client.new

syntax: c, err = client.new(config)

Create a ACMEv2 client.

Default values for config are:

default_config = {
  -- the ACME v2 API endpoint to use
  api_uri = "https://acme-v02.api.letsencrypt.org/directory",
  -- the account email to register
  account_email = nil,
  -- the account key in PEM format text
  account_key = nil,
  -- the account kid (as an URL)
  account_kid = nil,
  -- storage for challenge and IPC (TODO)
  storage_adapter = "shm",
  -- the storage config passed to storage adapter
  storage_config = {
    shm_name = "acme"
  },
  -- the challenge types enabled, selection of `http-01` and `tls-alpn-01`
  enabled_challenge_handlers = {"http-01"}
}

If account_kid is omitted, user must call client:new_account() to register a new account. Note that when using the same account_key, client:new_account() will return the same kid that is previosuly registered.

See also Storage Adapters below.

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client:init

syntax: err = client:init()

Initialize the client, requires availability of cosocket API. This function will login or register an account.

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client:order_certificate

syntax: err = client:order_certificate(domain,...)

Create a certificate with one or more domains. Note that wildcard domains are not supported as it can only be verified by dns-01 challenge.

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client:serve_http_challenge

syntax: client:serve_http_challenge()

Serve http-01 challenge. A common use case will be to put this as a content_by_* block for /.well-known path.

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client:serve_tls_alpn_challenge

syntax: client:serve_tls_alpn_challenge()

Serve tls-alpn-01 challenge. See this section on how to use this handler.

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Storage Adapters

Storage adapters are used in autossl or acme client to storage temporary or persistent data. Depending on the deployment environment, there're currently five storage adapters available to select from. To implement a custom storage adapter, please refer to this doc.

file

Filesystem based storage. Sample configuration:

storage_config = {
    dir = '/etc/openresty/storage',
}

If dir is omitted, the OS temporary directory will be used.

luafilesystem or luafilesystem-ffi is needed when using the file storage for renewal.

shm

Lua shared dict based storage. Note this storage is volatile between Nginx restarts (not reloads). Sample configuration:

storage_config = {
    shm_name = 'dict_name',
}

redis

Redis based storage. The default config is:

storage_config = {
    host = '127.0.0.1',
    port = 6379,
    database = 0,
    -- Redis authentication key
    auth = nil,
}

Redis >= 2.6.0 is required as this storage requires PEXPIRE.

vault

Hashicorp Vault based storage. Only KV V2 backend is supported. The default config is:

storage_config = {
    host = '127.0.0.1',
    port = 8200,
    -- secrets kv prefix path
    kv_path = "acme",
    -- Vault token
    token = nil,
    -- timeout in ms
    timeout = 2000,
    -- use HTTPS
    https = false,
    -- turn on tls verification
    tls_verify = true
    -- SNI used in request, default to host if omitted
    tls_server_name = nil,
}

consul

Hashicorp Consul based storage. The default config is:

storage_config = {
    host = '127.0.0.1',
    port = 8500,
    -- kv prefix path
    kv_path = "acme",
    -- Consul ACL token
    token = nil,
    -- timeout in ms
    timeout = 2000,
}

TODO

• autossl: ocsp staping

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Credits

• Improvements of file storage by @dbalagansky

Copyright and License

This module is licensed under the BSD license.

Copyright (C) 2019, by fffonion fffonion@gmail.com.

All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

• Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

• Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

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See Also

• Automatic Certificate Management Environment (ACME)
• haproxytech/haproxy-lua-acme The ACME Lua implementation used in HAProxy.
• GUI/lua-resty-auto-ssl
• lua-resty-openssl
• Let's Encrypt API rate limits

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