openssl hangs and does not exit

On windows, simply typing winpty before your openssl command will do the trick. So, for example, you could create a certificate like so:

winpty openssl req -x509 -newkey rsa:2048 -keyout key.pem -out cert.pem -days XXX

It looks like some OpenSSL distributions for Windows are expecting an additional keypress, independant of standard input. Quit.txt gets correctly piped into openssl's STDIN (the server receives QUIT command), but nothing happens until you press any key.

This problem does not exist in Cygwin's version of OpenSSL. Unfortunatly base installation of Cygwin takes about 100 MB of disk space, but you can try to extract only openssl.exe and required libraries.

This method works:

echo QUIT | c:\cygwin\bin\openssl.exe s_client -showcerts -connect google.com:443 > cert.txt

If running under mingw64 on windows you can use the winpty program to correctly wrap the terminal

Eg creating alias under bash alias openssl='winpty openssl.exe'

Then openssl s_client -connect blah

Should work as expected