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Name

ngx.ocsp - Lua API for implementing OCSP stapling in ssl_certificate_by_lua*

Table of Contents

Status

This Lua module is currently considered experimental.

Synopsis

# Note: you do not need the following line if you are using
# OpenResty 1.9.7.2+.
lua_package_path "/path/to/lua-resty-core/lib/?.lua;;";

server {
    listen 443 ssl;
    server_name   test.com;

    # useless placeholders: just to shut up NGINX configuration
    # loader errors:
    ssl_certificate /path/to/fallback.crt;
    ssl_certificate_key /path/to/fallback.key;

    ssl_certificate_by_lua_block {
        local ssl = require "ngx.ssl"
        local ocsp = require "ngx.ocsp"
        local http = require "resty.http.simple"

        -- assuming the user already defines the my_load_certificate_chain()
        -- herself.
        local pem_cert_chain = assert(my_load_certificate_chain())

        local der_cert_chain, err = ssl.cert_pem_to_der(pem_cert_chain)
        if not der_cert_chain then
            ngx.log(ngx.ERR, "failed to convert certificate chain ",
                    "from PEM to DER: ", err)
            return ngx.exit(ngx.ERROR)
        end

        local ocsp_url, err = ocsp.get_ocsp_responder_from_der_chain(der_cert_chain)
        if not ocsp_url then
            ngx.log(ngx.ERR, "failed to get OCSP responder: ", err)
            return ngx.exit(ngx.ERROR)
        end

        print("ocsp_url: ", ocsp_url)

        -- use cosocket-based HTTP client libraries like lua-resty-http-simple
        -- to send the request (url + ocsp_req as POST params or URL args) to
        -- CA's OCSP server. assuming the server returns the OCSP response
        -- in the Lua variable, resp.

        local schema, host, port, ocsp_uri, err = parse_url(ocsp_url)

        local ocsp_req, err = ocsp.create_ocsp_request(der_cert_chain)
        if not ocsp_req then
            ngx.log(ngx.ERR, "failed to create OCSP request: ", err)
            return ngx.exit(ngx.ERROR)
        end

        local res, err = http.request(host, port, {
            path = ocsp_uri,
            headers = { Host = host,
                        ["Content-Type"] = "application/ocsp-request" },
            timeout = 10000,  -- 10 sec
            method = "POST",
            body = ocsp_req,
            maxsize = 102400,  -- 100KB
        })

        if not res then
            ngx.log(ngx.ERR, "OCSP responder query failed: ", err)
            return ngx.exit(ngx.ERROR)
        end

        local http_status = res.status

        if http_status ~= 200 then
            ngx.log(ngx.ERR, "OCSP responder returns bad HTTP status code ",
                    http_status)
            return ngx.exit(ngx.ERROR)
        end

        local ocsp_resp = res.body

        if ocsp_resp and #ocsp_resp > 0 then
            local ok, err = ocsp.validate_ocsp_response(ocsp_resp, der_cert_chain)
            if not ok then
                ngx.log(ngx.ERR, "failed to validate OCSP response: ", err)
                return ngx.exit(ngx.ERROR)
            end

            -- set the OCSP stapling
            ok, err = ocsp.set_ocsp_status_resp(ocsp_resp)
            if not ok then
                ngx.log(ngx.ERR, "failed to set ocsp status resp: ", err)
                return ngx.exit(ngx.ERROR)
            end
        end
    }

    location / {
        root html;
    }
}

Description

This Lua module provides API to perform OCSP queries, OCSP response validations, and OCSP stapling planting.

Usually, this module is used together with the ngx.ssl module in the context of ssl_certificate_by_lua* (of the ngx_lua module).

To load the ngx.ocsp module in Lua, just write

local ocsp = require "ngx.ocsp"

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Methods

get_ocsp_responder_from_der_chain

syntax: ocsp_url, err = ocsp.get_ocsp_responder_from_der_chain(der_cert_chain, max_len)

context: any

Extracts the OCSP responder URL (like "http://test.com/ocsp/") from the SSL server certificate chain in the DER format.

Usually the SSL server certificate chain is originally formatted in PEM. You can use the Lua API provided by the ngx.ssl module to do the PEM to DER conversion.

The optional max_len argument specifies the maximum length of OCSP URL allowed. This determines the buffer size; so do not specify an unnecessarily large value here. It defaults to the internal string buffer size used throughout this lua-resty-core library (usually default to 4KB).

In case of failures, returns nil and a string describing the error.

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create_ocsp_request

syntax: ocsp_req, err = ocsp.create_ocsp_request(der_cert_chain, max_len)

context: any

Builds an OCSP request from the SSL server certificate chain in the DER format, which can be used to send to the OCSP server for validation.

The optional max_len argument specifies the maximum length of the OCSP request allowed. This value determines the size of the internal buffer allocated, so do not specify an unnecessarily large value here. It defaults to the internal string buffer size used throughout this lua-resty-core library (usually defaults to 4KB).

In case of failures, returns nil and a string describing the error.

The raw OCSP response data can be used as the request body directly if the POST method is used for the OCSP request. But for GET requests, you need to do base64 encoding and then URL encoding on the data yourself before appending it to the OCSP URL obtained by the get_ocsp_responder_from_der_chain function.

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validate_ocsp_response

syntax: ok, err = ocsp.validate_ocsp_response(ocsp_resp, der_cert_chain, max_err_msg_len)

context: any

Validates the raw OCSP response data specified by the ocsp_resp argument using the SSL server certificate chain in DER format as specified in the der_cert_chain argument.

Returns true when the validation is successful.

In case of failures, returns nil and a string describing the failure. The maximum length of the error string is controlled by the optional max_err_msg argument (which defaults to the default internal string buffer size used throughout this lua-resty-core library, usually being 4KB).

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set_ocsp_status_resp

syntax: ok, err = ocsp.set_ocsp_status_resp(ocsp_resp)

context: ssl_certificate_by_lua*

Sets the OCSP response as the OCSP stapling for the current SSL connection.

Returns true in case of successes. If the SSL client does not send a "status request" at all, then this method still returns true but also with a string as the warning "no status req".

In case of failures, returns nil and a string describing the error.

The OCSP response is returned from CA's OCSP server. See the create_ocsp_request function for how to create an OCSP request and also validate_ocsp_response for how to validate the OCSP response.

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Community

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English Mailing List

The openresty-en mailing list is for English speakers.

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Chinese Mailing List

The openresty mailing list is for Chinese speakers.

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Bugs and Patches

Please report bugs or submit patches by

  1. creating a ticket on the GitHub Issue Tracker,
  2. or posting to the OpenResty community.

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Author

Yichun Zhang <agentzh@gmail.com> (agentzh), OpenResty Inc.

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Copyright and License

This module is licensed under the BSD license.

Copyright (C) 2015-2017, by Yichun "agentzh" Zhang, OpenResty Inc.

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

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