doc: yama: Swap HTTP for HTTPS and replace dead link

Replace one dead link for the same person's original presentation on the
topic and swap an HTTP URL with HTTPS. While here, linkify the text to
make it more readable when rendered.

Link: https://lore.kernel.org/lkml/[e-mail]/
Co-developed-by: Alexander A. Klimov <[e-mail]>
Signed-off-by: Alexander A. Klimov <[e-mail]>
Signed-off-by: Kees Cook <[e-mail]>
Link: https://lore.kernel.org/r/202007091141.C008B89EC@keescook
Signed-off-by: Jonathan Corbet <[e-mail]>

Documentation/admin-guide/LSM/Yama.rst

···
 etc) to extract additional credentials and continue to expand the scope
 of their attack without resorting to user-assisted phishing.
 
-This is not a theoretical problem. SSH session hijacking
-(http://www.storm.net.nz/projects/7) and arbitrary code injection
-(http://c-skills.blogspot.com/2007/05/injectso.html) attacks already
+This is not a theoretical problem. `SSH session hijacking
+<https://www.blackhat.com/presentations/bh-usa-05/bh-us-05-boileau.pdf>`_
+and `arbitrary code injection
+<https://c-skills.blogspot.com/2007/05/injectso.html>`_ attacks already
 exist and remain possible if ptrace is allowed to operate as before.
 Since ptrace is not commonly used by non-developers and non-admins, system
 builders should be allowed the option to disable this debugging system.