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Name

ngx.ssl - Lua API for controlling NGINX downstream SSL handshakes

Table of Contents

Status

This Lua module is production ready.

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"

        -- clear the fallback certificates and private keys
        -- set by the ssl_certificate and ssl_certificate_key
        -- directives above:
        local ok, err = ssl.clear_certs()
        if not ok then
            ngx.log(ngx.ERR, "failed to clear existing (fallback) certificates")
            return ngx.exit(ngx.ERROR)
        end

        -- 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 ok, err = ssl.set_der_cert(der_cert_chain)
        if not ok then
            ngx.log(ngx.ERR, "failed to set DER cert: ", err)
            return ngx.exit(ngx.ERROR)
        end

        -- assuming the user already defines the my_load_private_key()
        -- function herself.
        local pem_pkey = assert(my_load_private_key())
        local passphrase = "password" -- or nil

        local der_pkey, err = ssl.priv_key_pem_to_der(pem_pkey, passphrase)
        if not der_pkey then
            ngx.log(ngx.ERR, "failed to convert private key ",
                    "from PEM to DER: ", err)
            return ngx.exit(ngx.ERROR)
        end

        local ok, err = ssl.set_der_priv_key(der_pkey)
        if not ok then
            ngx.log(ngx.ERR, "failed to set DER private key: ", err)
            return ngx.exit(ngx.ERROR)
        end
    }

    location / {
        root html;
    }
}

Description

This Lua module provides API functions to control the SSL handshake process in contexts like ssl_certificate_by_lua* (of the ngx_lua module).

For web servers serving many (like millions of) https sites, it is often desired to lazily load and cache the SSL certificate chain and private key data for the https sites actually being served by a particular server. This Lua module provides API to support such use cases in the context of the ssl_certificate_by_lua* directive.

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

local ssl = require "ngx.ssl"

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Methods

clear_certs

syntax: ok, err = ssl.clear_certs()

context: ssl_certificate_by_lua*

Clears any existing SSL certificates and/or private keys set on the current SSL connection.

Returns true on success, or a nil value and a string describing the error otherwise.

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cert_pem_to_der

syntax: der_cert_chain, err = ssl.cert_pem_to_der(pem_cert_chain)

context: any

Converts the PEM-formatted SSL certificate chain data into the DER format (for later uses in the set_der_cert function, for example).

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

It is known that the openssl command-line utility may not convert the whole SSL certificate chain from PEM to DER correctly. So always use this Lua function to do the conversion. You can always use libraries like lua-resty-lrucache and/or ngx_lua APIs like lua_shared_dict to do the caching of the DER-formatted results, for example.

This function can be called in any context.

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set_der_cert

syntax: ok, err = ssl.set_der_cert(der_cert_chain)

context: ssl_certificate_by_lua*

Sets the DER-formatted SSL certificate chain data for the current SSL connection. Note that the DER data is directly in the Lua string argument. No external file names are supported here.

Returns true on success, or a nil value and a string describing the error otherwise.

Note that, the SSL certificate chain is usually encoded in the PEM format. So you need to use the cert_pem_to_der function to do the conversion first.

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priv_key_pem_to_der

syntax: der_priv_key, err = ssl.priv_key_pem_to_der(pem_priv_key, passphrase)

context: any

Converts the PEM-formatted SSL private key data into the DER format (for later uses in the set_der_priv_key function, for example).

The passphrase is the passphrase for pem_priv_key if the private key is password protected.

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

Alternatively, you can do the PEM to DER conversion offline with the openssl command-line utility, like below

openssl rsa -in key.pem -outform DER -out key.der

This function can be called in any context.

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set_der_priv_key

syntax: ok, err = ssl.set_der_priv_key(der_priv_key)

context: ssl_certificate_by_lua*

Sets the DER-formatted prviate key for the current SSL connection.

Returns true on success, or a nil value and a string describing the error otherwise.

Usually, the private keys are encoded in the PEM format. You can either use the priv_key_pem_to_der function to do the PEM to DER conversion or just use the openssl command-line utility offline, like below

openssl rsa -in key.pem -outform DER -out key.der

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server_name

syntax: name, err = ssl.server_name()

context: any

Returns the TLS SNI (Server Name Indication) name set by the client. Returns nil when the client does not set it.

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

Usually we use this SNI name as the domain name (like www.openresty.org) to identify the current web site while loading the corresponding SSL certificate chain and private key for the site.

Please note that not all https clients set the SNI name, so when the SNI name is missing from the client handshake request, we use the server IP address accessed by the client to identify the site. See the raw_server_addr method for more details.

This function can be called in any context where downstream https is used.

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server_port

syntax: port, err = ssl.server_port()

context: any

Returns the server port. Returns nil when server dont have a port.

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

This function can be called in any context where downstream https is used.

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raw_server_addr

syntax: addr_data, addr_type, err = ssl.raw_server_addr()

context: any

Returns the raw server address actually accessed by the client in the current SSL connection.

The first two return values are strings representing the address data and the address type, respectively. The address values are interpreted differently according to the address type values:

  • unix : The address data is a file path for the UNIX domain socket.
  • inet : The address data is a binary IPv4 address of 4 bytes long.
  • inet6 : The address data is a binary IPv6 address of 16 bytes long.

Returns two nil values and a Lua string describing the error.

The following code snippet shows how to print out the UNIX domain socket address and the IPv4 address as human-readable strings:

local ssl = require "ngx.ssl"
local byte = string.byte

local addr, addrtyp, err = ssl.raw_server_addr()
if not addr then
    ngx.log(ngx.ERR, "failed to fetch raw server addr: ", err)
    return
end

if addrtyp == "inet" then  -- IPv4
    ip = string.format("%d.%d.%d.%d", byte(addr, 1), byte(addr, 2),
                       byte(addr, 3), byte(addr, 4))
    print("Using IPv4 address: ", ip)

elseif addrtyp == "unix" then  -- UNIX
    print("Using unix socket file ", addr)

else  -- IPv6
    -- leave as an exercise for the readers
end

This function can be called in any context where downstream https is used.

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export_keying_material

syntax: key, err = ssl.export_keying_material(length, label, context)

context: set_by_lua*, rewrite_by_lua*, access_by_lua*, content_by_lua*, header_filter_by_lua*, body_filter_by_lua*, log_by_lua*

Return a key derived from the SSL master secret.

As described in RFC8446 section 7.5 this function returns key material that is derived from the SSL master secret and can be used on the application level. The returned key material is of the given length. Label is mandatory and requires a special format that is described in RFC5705 section 4. Context is optional but note that in TLSv1.2 and below a zero length context is treated differently from no context at all, and will result in different keying material being returned. In TLSv1.3 a zero length context is that same as no context at all and will result in the same keying material being returned.

The following code snippet shows how to derive a new key that can be used on the application level.

local ssl = require "ngx.ssl"

local key_length = 16
local label = "EXPERIMENTAL my label"
local context = "\x00\x01\x02\x03"

local key, err = ssl.export_keying_material(key_length, label, context)
if not key then
    ngx.log(ngx.ERR, "failed to derive key ", err)
    return
end

-- use key...

end

This function can be called in any context where downstream https is used.

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export_keying_material_early

syntax: key, err = ssl.export_keying_material_early(length, label, context)

context: set_by_lua*, rewrite_by_lua*, access_by_lua*, content_by_lua*, header_filter_by_lua*, body_filter_by_lua*, log_by_lua*

Returns a key derived from the SSL early exporter master secret.

As described in RFC8446 section 7.5 this function returns key material that is derived from the SSL early exporter master secret and can be used on the application level. The returned key material is of the given length. Label is mandatory and requires a special format that is described in RFC5705 section 4. This function is only usable with TLSv1.3, and derives keying material using the early_exporter_master_secret (as defined in the TLS 1.3 RFC). For the client, the early_exporter_master_secret is only available when the client attempts to send 0-RTT data. For the server, it is only available when the server accepts 0-RTT data.

The following code snippet shows how to derive a new key that can be used on the application level.

local ssl = require "ngx.ssl"

local key_length = 16
local label = "EXPERIMENTAL my label"
local context = "\x00\x01\x02\x03"

local key, err = ssl.export_keying_material_early(key_length, label, context)
if not key then
    ngx.log(ngx.ERR, "failed to derive key ", err)
    return
end

-- use key...

end

This function can be called in any context where downstream https TLS1.3 is used.

Back to TOC

raw_client_addr

syntax: addr_data, addr_type, err = ssl.raw_client_addr()

context: any

Returns the raw client address of the current SSL connection.

The first two return values are strings representing the address data and the address type, respectively. The address values are interpreted differently according to the address type values:

  • unix : The address data is a file path for the UNIX domain socket.
  • inet : The address data is a binary IPv4 address of 4 bytes long.
  • inet6 : The address data is a binary IPv6 address of 16 bytes long.

Returns two nil values and a Lua string describing the error.

The following code snippet shows how to print out the UNIX domain socket address and the IPv4 address as human-readable strings:

local ssl = require "ngx.ssl"
local byte = string.byte

local addr, addrtyp, err = ssl.raw_client_addr()
if not addr then
    ngx.log(ngx.ERR, "failed to fetch raw client addr: ", err)
    return
end

if addrtyp == "inet" then  -- IPv4
    ip = string.format("%d.%d.%d.%d", byte(addr, 1), byte(addr, 2),
                       byte(addr, 3), byte(addr, 4))
    print("Client IPv4 address: ", ip)

elseif addrtyp == "unix" then  -- UNIX
    print("Client unix socket file ", addr)

else  -- IPv6
    -- leave as an exercise for the readers
end

This function can be called in any context where downstream https is used.

This function was first introduced in lua-resty-core 0.1.14.

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get_tls1_version

syntax: ver, err = ssl.get_tls1_version()

context: any

Returns the TLS 1.x version number used by the current SSL connection. Returns nil and a string describing the error otherwise.

Typical return values are:

  • 0x0300(SSLv3)
  • 0x0301(TLSv1)
  • 0x0302(TLSv1.1)
  • 0x0303(TLSv1.2)
  • 0x0304(TLSv1.3)

This function can be called in any context where downstream https is used.

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get_tls1_version_str

syntax: ver, err = ssl.get_tls1_version_str()

context: any

Returns the TLS 1.x version string used by the current SSL connection. Returns nil and a string describing the error otherwise.

If the TLS 1.x version number used by the current SSL connection is not recognized, the return values will be nil and the string "unknown version".

Typical return values are:

  • SSLv3
  • TLSv1
  • TLSv1.1
  • TLSv1.2
  • TLSv1.3

This function can be called in any context where downstream https is used.

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parse_pem_cert

syntax: cert_chain, err = ssl.parse_pem_cert(pem_cert_chain)

context: any

Converts the PEM-formated SSL certificate chain data into an opaque cdata pointer (for later uses in the set_cert function, for example).

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

You can always use libraries like lua-resty-lrucache to cache the cdata result.

This function can be called in any context.

This function was first added in version 0.1.7.

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parse_pem_priv_key

syntax: priv_key, err = ssl.parse_pem_priv_key(pem_priv_key)

context: any

Converts the PEM-formatted SSL private key data into an opaque cdata pointer (for later uses in the set_priv_key function, for example).

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

This function can be called in any context.

This function was first added in version 0.1.7.

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parse_der_cert

syntax: cert_chain, err = ssl.parse_der_cert(der_cert_chain)

context: any

Converts the DER-formated SSL certificate chain data into an opaque cdata pointer (for later uses in the set_cert function, for example).

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

You can always use libraries like lua-resty-lrucache to cache the cdata result.

This function can be called in any context.

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parse_der_priv_key

syntax: priv_key, err = ssl.parse_der_priv_key(der_priv_key)

context: any

Converts the DER-formatted SSL private key data into an opaque cdata pointer (for later uses in the set_priv_key function, for example).

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

This function can be called in any context.

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set_cert

syntax: ok, err = ssl.set_cert(cert_chain)

context: ssl_certificate_by_lua*

Sets the SSL certificate chain opaque pointer returned by the parse_pem_cert or parse_der_certfunction for the current SSL connection.

Returns true on success, or a nil value and a string describing the error otherwise.

Note that this set_cert function will run slightly faster, in terms of CPU cycles wasted, than the set_der_cert variant, since the first function uses opaque cdata pointers which do not require any additional conversion needed to be performed by the SSL library during the SSL handshake.

This function was first added in version 0.1.7.

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set_priv_key

syntax: ok, err = ssl.set_priv_key(priv_key)

context: ssl_certificate_by_lua*

Sets the SSL private key opaque pointer returned by the parse_pem_priv_key or parse_der_priv_key function for the current SSL connection.

Returns true on success, or a nil value and a string describing the error otherwise.

Note that this set_priv_key function will run slightly faster, in terms of CPU cycles wasted, than the set_der_priv_key variant, since the first function uses opaque cdata pointers which do not require any additional conversion needed to be performed by the SSL library during the SSL handshake.

This function was first added in version 0.1.7.

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verify_client

syntax: ok, err = ssl.verify_client(ca_certs?, depth?)

context: ssl_certificate_by_lua*

Requires a client certificate during TLS handshake.

The ca_certs is the CA certificate chain opaque pointer returned by the parse_pem_cert function for the current SSL connection. The list of certificates will be sent to clients. Also, they will be added to trusted store. If omitted, will not send any CA certificate to clients.

The depth is the verification depth in the client certificates chain. If omitted, will use the value specified by ssl_verify_depth.

Returns true on success, or a nil value and a string describing the error otherwise.

Note that TLS is not terminated when verification fails. You need to examine Nginx variable $ssl_client_verify later to determine next steps.

This function was first added in version 0.1.20.

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get_client_random

syntax: client_random = ssl.get_client_random(outlen?)

context: any

Returns the random value sent from the client to the server during the initial SSL/TLS handshake.

The outlen parameter indicates the maximum length of the client_random value returned. If the outlen is zero, this function returns the total length of the client_random value. If omitted, will use the value 32.

This function can be called in any context where downstream https is used, but in the context of ssl_client_hello_by_lua*, it can not return the real client_random value, just a string filled with 0.

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get_req_ssl_pointer

syntax: ssl_ptr, err = ssl.get_req_ssl_pointer()

context: any

Retrieves the OpenSSL SSL* object for the current downstream connection.

Returns an FFI pointer on success, or a nil value and a string describing the error otherwise.

If you need to retain the pointer beyond the current phase then you will need to use OpenSSL's SSL_up_ref to increase the reference count. If you do, ensure that your reference is released with SSL_free.

This function was first added in version 0.1.16.

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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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