PAM module state (created in pam_sm_authenticate and referenced later
in pam_sm_setcred and pam_sm_acct_mgmt). However, the krb5_ccache
structure shares some data members with the krb5_context structure
that was used in its creation. Since a new krb5_context is created
and destroyed at each PAM entry point, this inevitably caused the
krb5_ccache structure to reference free'd memory.
Now instead of storing a pointer to the krb5_ccache structure,
we store the name of the cache (e.g. `MEMORY:0x123CACHE') in
pam_sm_authenticate, and resolve the name in the other entry points.
This bug was uncovered by phkmalloc's free'd memory scrubbing.
Approved by: re (jhb)
7c2274dc95