Suggested edit for PIV/Guides/SSH_with_PIV_and_PKCS11

[tsuna]

The recommendation that "Homebrew users can use export OPENSC_LIBS=$(brew --prefix opensc)/lib." is incorrect at least as of MacOS Sierra (10.13.x). It will lead to:

$ ssh-add -s $OPENSC_LIBS/opensc-pkcs11.so
Enter passphrase for PKCS#11: 
Could not add card "/usr/local/opt/opensc/lib/opensc-pkcs11.so": agent refused operation

Because ssh-agent does not allow /usr/local/opt/opensc/lib/opensc-pkcs11.so. Instead the workaround is:

sudo ln -f `brew list opensc | grep lib/opensc-pkcs11.so` /usr/local/lib/opensc-pkcs11.so

Related issues: Homebrew/homebrew-core#16385 OpenSC/OpenSC#1007 OpenSC/OpenSC#1008 #88 #153

[klali]

thanks.

[dch]

this would be better expressed as find -E /usr/local/Cellar/opensc/ -name opensc-pkcs11.so -type f | head -1