# How does find-openssl work?
**URL:** https://discourse.cmake.org/t/how-does-find-openssl-work/13142
**Category:** Development
**Created:** [December 6, 2024, 9:18pm UTC](https://discourse.cmake.org/t/how-does-find-openssl-work/13142 "2024-12-06T21:18:04Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@rsalz](https://discourse.cmake.org/u/rsalz)
#### Post date: [December 6, 2024, 9:18pm UTC](https://discourse.cmake.org/t/how-does-find-openssl-work/13142/1 "2024-12-06T21:18:04Z")
I am working on a fork of OpenSSL, called QuicTLS. One of the things we are doing is switch from the customer Perl to a cmake build. A test is failing and I’m trying to figure out what I broke. The test is bringing in OQS library and I get the following error:
```auto
CMake Error at /usr/local/share/cmake-3.31/Modules/FindPackageHandleStandardArgs.cmake:233 (message):
Could NOT find OpenSSL, try to set the path to OpenSSL root folder in the
system variable OPENSSL_ROOT_DIR: (Required is at least version "1.1.1")
(found /home/runner/work/quictls/quictls/libcrypto.so, )
Call Stack (most recent call first):
/usr/local/share/cmake-3.31/Modules/FindPackageHandleStandardArgs.cmake:601 (_FPHSA_FAILURE_MESSAGE)
/usr/local/share/cmake-3.31/Modules/FindOpenSSL.cmake:691 (find_package_handle_standard_args)
CMakeLists.txt:133 (find_package)
-- Configuring incomplete, errors occurred!
```
How can I figure out what I broke?
---
### Author:  [@rsalz](https://discourse.cmake.org/u/rsalz)
#### Post date: [December 6, 2024, 9:33pm UTC](https://discourse.cmake.org/t/how-does-find-openssl-work/13142/2 "2024-12-06T21:33:12Z")
So it turns out that our QuicTLS fork merges opensslv.h into configuration.h. (I thought that CMake really wants just one config file, am I wrong?). For now I jammed something into opensslv.h. Could we maybe search BOTH files? Or is my assumption wrong? Tnx.
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### Author:  [@brad.king](https://discourse.cmake.org/u/brad.king)
#### Post date: [December 6, 2024, 9:43pm UTC](https://discourse.cmake.org/t/how-does-find-openssl-work/13142/3 "2024-12-06T21:43:53Z")
> [@rsalz](#):
>
> I thought that CMake really wants just one config file
That is the case for `find_package`’s “CONFIG” mode, which is used when explicitly requested or when no Find module is available. You can provide a `QuicTLSConfig.cmake` package configuration file by following the [cmake-packages(7)](https://cmake.org/cmake/help/v3.31/manual/cmake-packages.7.html) manual, and then your package can be found by `find_package(QuicTLS)` with no help from a find module. You should also provide an adjacent `QuicTLSConfigVersion.cmake` package version file to make versioning work.
A `find_package(OpenSSL)` call will use CMake’s `FindOpenSSL` module, which searches for individual artifacts. That module extracts the OpenSSL version number from `openssl/opensslv.h`, which is expected to exist as it is a [documented](https://docs.openssl.org/3.0/man3/OpenSSL_version/) part of OpenSSL’s public interface.
---
### Author:  [@rsalz](https://discourse.cmake.org/u/rsalz)
#### Post date: [December 6, 2024, 10:00pm UTC](https://discourse.cmake.org/t/how-does-find-openssl-work/13142/4 "2024-12-06T22:00:10Z")
Thanks. We want to maintain compatibility; I’ll have to think what to do.
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### Author:  [@rsalz](https://discourse.cmake.org/u/rsalz)
#### Post date: [January 9, 2025, 6:02pm UTC](https://discourse.cmake.org/t/how-does-find-openssl-work/13142/5 "2025-01-09T18:02:56Z")
Just to close the thread, I inverted the order of inclusion and call `configure_file` multiple times. Thanks!