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Compile OpenSSL Crypto Only

G5 Cyber Security

TL;DR

This guide shows you how to build just the crypto part of OpenSSL, saving time and resources if you don’t need the SSL/TLS functionality. This is useful for applications that only require cryptographic operations like hashing or signing.

Steps

  1. Download OpenSSL Source Code
    • Visit the OpenSSL website and download the latest stable source code archive (e.g., a .tar.gz file).
    • Extract the archive using a command like:
    tar -xzf openssl-x.y.z.tar.gz
  2. Configure OpenSSL
    • Navigate into the extracted directory:
    cd openssl-x.y.z
  3. Run the configure script with specific options to disable SSL/TLS and enable only crypto features. This is the crucial step! Use these flags:
    • --prefix=/path/to/install: Specify where you want to install OpenSSL (replace /path/to/install).
    • -no-ssl: Disable SSL functionality.
    • -no-tls1_3: Disable TLSv1.3 functionality.
    • -shared: Build as a shared library (recommended for most use cases).
    4. ./config --prefix=/usr/local -no-ssl -no-tls1_3 -shared
  4. Build OpenSSL
    • Compile the source code:
    make
  5. This will take some time, but it should be faster than a full build.
  6. Test (Optional)
    • Run the test suite to verify the crypto part is working correctly:
    make test
  7. Note that some tests might fail if SSL/TLS functionality isn’t available, which is expected in this case.
  8. Install OpenSSL
    • Install the compiled libraries and headers:
    make install
  9. This will copy the files to the directory specified with --prefix during configuration.
  10. Configure Your Application
    • Update your application’s build system (e.g., Makefile, CMakeLists.txt) to link against the newly installed OpenSSL libraries. Make sure to include the correct include paths and library paths.
    • For example, in a Makefile:
    CFLAGS = -I/usr/local/include
    LDFLAGS = -L/usr/local/lib -lssl -lcrypto
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