krb5: add copy_ccache_into_memory() Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>

KRB5: Move all ccache operations to krb5_child.c The credential cache operations must be now performed by the krb5_child completely, because the sssd_be process might be running as the sssd user who doesn't have access to the ccaches. src/providers/krb5/krb5_ccache.c is still linked against libsss_krb5 until we fix Kerberos ticket renewal as non-root. Also includes a new error code that indicates that the back end should remove the old ccache attribute -- the child can't do that if it's running as the user. Related: https://fedorahosted.org/sssd/ticket/2370 Reviewed-by: Sumit Bose <sbose@redhat.com> Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>

KRB5: Move checking for illegal RE to krb5_utils.c Otherwise we would have to link krb5_child with pcre and transfer the regex, which would be cumbersome. Check for illegal patterns when expanding the template instead. Related: https://fedorahosted.org/sssd/ticket/2370 Reviewed-by: Sumit Bose <sbose@redhat.com> Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>

KRB5: Move ccache-related functions to krb5_ccache.c Add a new module krb5_ccache.c that contains all ccache-related operations. The only user of this module shall be krb5_child.c as the other modules will run unprivileged and accessing the ccache requires either privileges of root or the ccache owner. Related: https://fedorahosted.org/sssd/ticket/2370 Reviewed-by: Sumit Bose <sbose@redhat.com> Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>