Qt 5.9 | Qt Network | Secure Sockets Layer (SSL) Classes

Qt 5.9.9 Reference Documentation

# Secure Sockets Layer (SSL) Classes

The classes below provide support for secure network communication using the Secure Sockets Layer (SSL) protocol, using the OpenSSL Toolkit to perform encryption and protocol handling.

From Qt version 5.6 onwards, the officially supported version for OpenSSL is 1.0.0 or later.

QSsl | Declares enums common to all SSL classes in Qt Network
QSslCertificate | Convenient API for an X509 certificate
QSslCertificateExtension | API for accessing the extensions of an X509 certificate
QSslCipher | Represents an SSL cryptographic cipher
QSslConfiguration | Holds the configuration and state of an SSL connection
QSslDiffieHellmanParameters | Interface for Diffie-Hellman parameters for servers
QSslEllipticCurve | Represents an elliptic curve for use by elliptic-curve cipher algorithms
QSslError | SSL error
QSslKey | Interface for private and public keys
QSslPreSharedKeyAuthenticator | Authentication data for pre shared keys (PSK) ciphersuites
QSslSocket | SSL encrypted socket for both clients and servers

## Enabling and Disabling SSL Support

When building Qt from source, the configuration system checks for the presence of the `openssl/opensslv.h` header provided by source or developer packages of OpenSSL.

By default, an SSL-enabled Qt library dynamically loads any installed OpenSSL library at run-time. However, it is possible to link against the library at compile-time by configuring Qt with the `-openssl-linked` option.

When building a version of Qt linked against OpenSSL, the build system will attempt to link with libssl and libcrypt libraries located in the default location on the developer's system. This location is configurable: set the `OPENSSL_LIBS` environment variable to contain the linker options required to link Qt against the installed library. For example, on a Unix/Linux system:

      OPENSSL_LIBS='-L/opt/ssl/lib -lssl -lcrypto' ./configure -openssl-linked

To disable SSL support in a Qt build, configure Qt with the `-no-openssl` option.

## Import and Export Restrictions

Due to import and export restrictions in some parts of the world, we are unable to supply the OpenSSL Toolkit with Qt packages. Developers wishing to use SSL communication in their deployed applications should either ensure that their users have the appropriate libraries installed, or they should consult a suitably qualified legal professional to ensure that applications using code from the OpenSSL project are correctly certified for import and export in relevant regions of the world.