Swiftpack.co - Package - apple/swift-nio-ssl


SwiftNIO SSL is a Swift package that contains an implementation of TLS based on OpenSSL-compatible libraries (that is, any library that ships a libssl that is compatible with OpenSSL's). This package allows users of SwiftNIO to write protocol clients and servers that use TLS to secure data in flight.

The name is inspired primarily by the names of the libraries this package supports (e.g. OpenSSL, LibreSSL, and friends), and not because we don't know the name of the protocol. We know the protocol is TLS!

Using SwiftNIO SSL

SwiftNIO SSL provides two ChannelHandlers to use to secure a data stream: the OpenSSLClientHandler and the OpenSSLServerHandler. Each of these can be added to a Channel to secure the communications on that channel.

Additionally, we provide a number of low-level primitives for configuring your TLS connections. These will be shown below.

To secure a server connection, you will need a X.509 certificate chain in a file (either PEM or DER, but PEM is far easier), and the associated private key for the leaf certificate. These objects can then be wrapped up in a TLSConfiguration object that is used to initialize the ChannelHandler.

For example:

let configuration = TLSConfiguration.forServer(certificateChain: [.file("cert.pem")], privateKey: .file("key.pem")) 
let sslContext = try SSLContext(configuration: configuration)
let handler = try OpenSSLServerHandler(context: sslContext)
// Add the created handler to the pipeline.

For clients, it is a bit simpler as there is no need to have a certificate chain or private key (though clients may have these things). Setup for clients may be done like this:

let configuration = TLSConfiguration.forClient()
let sslContext = try SSLContext(configuration: configuration)
let handler = try OpenSSLClientHandler(context: sslContext)
// Add the created handler to the pipeline.


This binding can cause numerous issues during the build process on different systems, depending on the environment you're in. These will usually manifest as build errors, either during the compilation stage (due to missing development headers) or during the linker stage (due to an inability to find a library to link).

If you encounter any of these errors, here are your options.

Darwin (iOS, macOS, tvOS, ...)

If you target iOS/tv 12+ or macOS 10.14+ we recommend using swift-nio-transport-services which is SwiftNIO on top of Network.framework which supports TLS out of the box.

If you need to target older versions on macOS we recommend installing libressl from Homebrew (brew install libressl) as there is no easily-available copy of libssl.dylib with accompanying development headers.


On Linux distributions it is almost always possible to get development headers for the system copy of libssl (e.g. via apt-get install libssl-dev). If you encounter problems during the compile phase, try running this command.

In some unusual situations you may encounter problems during the link phase. This is usually the result of having an extremely locked down system that does not grant you sufficient permissions to the libssl.so on the system.


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1.4.0 - Jan 18, 2019

Semver Minor

  • Added support for removing TLS handlers from live connections without tearing those connections down ("unwrapping" TLS from a connection) (#54)
  • Made TLSConfiguration structures mutable. (#58)
  • Fixed crashes when issuing a certain pattern of repeated calls to Channel.close() while a TLS handler is in the pipeline. (#52)
  • Added support for extracting the public keys of TLS certificates during handshakes.

Semver Patch

  • Warnings and test cleanup. (#53, #61)

1.3.2 - Oct 29, 2018

Semver Patch

  • Added Android support. This is not currently under CI, so may regress. (#45)
  • Improved .gitignore. (#42)
  • Improved documentation. (#43)

1.3.1 - Sep 18, 2018

Semver Patch

  • Fixed a bug where receiving a CLOSE_NOTIFY in the same read call as application data would cause us to fail to emit that application data, leading to data loss. (#40)
  • Fixed an issue where release mode builds would fail due to duplicate symbol definitions. (#41)

1.3.0 - Sep 17, 2018

Semver Minor

  • Added support for OpenSSL 1.1 on all platforms. This is the first release that supports the OpenSSL 1.1 series of libraries. (#20)
  • Added support for OpenSSL 1.1.1. (#36, #37)
  • Added support for configuring TLS 1.3 ciphers explicitly (#38)

Semver Patch

  • Added custom ByteBufferBIO object to reduce the overhead of application data processing in OpenSSL. This leads to faster throughput. (#27)
  • Fixed some performance problems in the sample TLS echo server. (#28)
  • Testing improvements (#33).

1.2.1 - Sep 12, 2018

This release contains no code changes, and is exists purely for administrative purposes.