Notes on OpenSSL and Qt

In Qt, working with SSL can be frustrating because of the inconsistent naming of the corresponding binary dynamic libraries, and Qt defaults to dynamically loading them, without providing any indication if they are missing.

Libraries name of openssl?

The "library" portion of OpenSSL consists of two libraries.

On posix system they are named:

libssl
libcrypto

while on Windows(32bit) they are named completely different:

libeay32
ssleay32

`qsslocket_openssl_symbols.cpp`

In this file, we can figure out how ssl libries are found and loaded.

static QPair<QSystemLibrary*, QSystemLibrary*> loadOpenSslWin32()
{
    QPair<QSystemLibrary*,QSystemLibrary*> pair;
    pair.first = 0;
    pair.second = 0;

    // When OpenSSL is built using MSVC then the libraries are named 'ssleay32.dll' and 'libeay32'dll'.
    // When OpenSSL is built using GCC then different library names are used (depending on the OpenSSL version)
    // The oldest version of a GCC-based OpenSSL which can be detected by the code below is 0.9.8g (released in 2007)
    if (!tryToLoadOpenSslWin32Library(QLatin1String("ssleay32"), QLatin1String("libeay32"), pair)) {
        if (!tryToLoadOpenSslWin32Library(QLatin1String("libssl-10"), QLatin1String("libcrypto-10"), pair)) {
            if (!tryToLoadOpenSslWin32Library(QLatin1String("libssl-8"), QLatin1String("libcrypto-8"), pair)) {
                tryToLoadOpenSslWin32Library(QLatin1String("libssl-7"), QLatin1String("libcrypto-7"), pair);
            }
        }
    }

    return pair;
}

ssl.pri

In this file, we can found how to link open at Qt-itself config time.

    # Add optional SSL libs
    # Static linking of OpenSSL with msvc:
    #   - Binaries http://slproweb.com/products/Win32OpenSSL.html
    #   - also needs -lUser32 -lAdvapi32 -lGdi32 -lCrypt32
    #   - libs in <OPENSSL_DIR>\lib\VC\static
    #   - configure: -openssl -openssl-linked -I <OPENSSL_DIR>\include -L <OPENSSL_DIR>\lib\VC\static OPENSSL_LIBS="-lUser32 -lAdvapi32 -lGdi32" OPENSSL_LIBS_DEBUG="-lssleay32MDd -llibeay32MDd" OPENSSL_LIBS_RELEASE="-lssleay32MD -llibeay32MD"

configure option

Options list here:

    -no-openssl ........ Do not compile support for OpenSSL.
 +  -openssl ........... Enable run-time OpenSSL support.
    -openssl-linked .... Enabled linked OpenSSL support.

Reference

http://www.ski-epic.com/2007_notes_on_openssl/index.html

1+1=10

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