FindOpenSSL

Finds the installed OpenSSL encryption library and determines its version.

Added in version 3.20: Support for specifying version range when calling the find_package() command. When a version is requested, it can be specified as a single value as before, and now also a version range can be used. For a detailed description of version range usage and capabilities, refer to the find_package() command.

Added in version 3.18: Support for OpenSSL 3.0.

Components

This module supports the following optional components:

Crypto

Added in version 3.12.

Ensures that the OpenSSL crypto library is found.

SSL

Added in version 3.12.

Ensures that the OpenSSL ssl library is found.

Components can be optionally specified using a standard syntax:

find_package(OpenSSL [COMPONENTS <components>...])

If no components are requested, module by default searches for the Crypto as required and SSL as optional component.

Imported Targets

This module provides the following Imported Targets:

OpenSSL::Crypto

Added in version 3.4.

Target encapsulating the OpenSSL crypto library usage requirements, available only if the crypto library is found.

OpenSSL::SSL

Added in version 3.4.

Target encapsulating the OpenSSL ssl library usage requirements, available only if the ssl library is found. For convenience, this target also links OpenSSL::Crypto, since the ssl library depends on the crypto library.

OpenSSL::applink

Added in version 3.18.

Target encapsulating the OpenSSL application-side interface (openssl/applink.c) usage requirements, available only if OpenSSL is found and its version is at least 0.9.8.

This interface provides a glue between OpenSSL BIO layer and the Windows compiler runtime environment and may need to be compiled into projects when using MSVC. By linking this target, the other OpenSSL imported targets can be linked even if the project uses different MSVC runtime configuration. Linking this target on platforms other than MSVC has no effect.

Note

The interface file is added using the INTERFACE_SOURCES target property. Due to how interface sources are propagated in CMake, it is recommended to link the OpenSSL::applink target as PRIVATE to ensure that it is linked only once in the entire dependency graph of any library or executable:

target_link_libraries(project_target PRIVATE OpenSSL::applink)

Using other scopes for this target specifically can lead to unexpected issues during the build or link process, as both the ISO C and ISO C++ standards place very few requirements on how linking should behave.

Result Variables

This module defines the following variables:

OpenSSL_FOUND

Boolean indicating whether the OpenSSL library has been found. For backward compatibility, the OPENSSL_FOUND variable is also set to the same value.

OPENSSL_INCLUDE_DIR

The OpenSSL include directory.

OPENSSL_CRYPTO_LIBRARY

The OpenSSL crypto library.

OPENSSL_CRYPTO_LIBRARIES

The OpenSSL crypto library and its dependencies.

OPENSSL_SSL_LIBRARY

The OpenSSL ssl library.

OPENSSL_SSL_LIBRARIES

The OpenSSL ssl library and its dependencies.

OPENSSL_LIBRARIES

All OpenSSL libraries and their dependencies.

OPENSSL_VERSION

The OpenSSL version found. This is set to <major>.<minor>.<revision><patch> (e.g. 0.9.8s).

OPENSSL_APPLINK_SOURCE

The sources in the target OpenSSL::applink mentioned above. This variable is only defined if found OpenSSL version is at least 0.9.8 and the platform is MSVC.

Hints

This module accepts the following variables to control the search behavior:

OPENSSL_ROOT_DIR

Set to the root directory of an OpenSSL installation to search for the OpenSSL libraries in custom locations.

OPENSSL_USE_STATIC_LIBS

Added in version 3.4.

Set to TRUE to prefer static OpenSSL libraries over shared ones.

OPENSSL_MSVC_STATIC_RT

Added in version 3.5.

Set to TRUE to search for the OpenSSL libraries built with the MSVC static runtime (MT).

ENV{PKG_CONFIG_PATH}

On UNIX-like systems, pkg-config is used to locate OpenSSL. Set the PKG_CONFIG_PATH environment variable to specify alternate locations, which is useful on systems with multiple library installations.

Examples

Finding the OpenSSL crypto library and linking it to a project target:

find_package(OpenSSL)
target_link_libraries(project_target PRIVATE OpenSSL::Crypto)

The following example shows how to find the OpenSSL crypto and ssl libraries and link them to a project target. The SSL component is explicitly specified to ensure that the find module reports an error if the ssl library is not found:

find_package(OpenSSL COMPONENTS SSL)
target_link_libraries(project_target PRIVATE OpenSSL::SSL)