if the euid!=owner of the userns, the kernel returns EPERM when trying
to write the uidmap and there is no CAP_SYS_ADMIN in the parent
namespace.
Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>
Some distributions, notably Fedora, have the following order of nsswitch
modules by default:
passwd: sss files
group: sss files
The advantage of serving local users through SSSD is that the nss_sss
module has a fast mmapped-cache that speeds up NSS lookups compared to
accessing the disk an opening the files on each NSS request.
Traditionally, this has been done with the help of nscd, but using nscd
in parallel with sssd is cumbersome, as both SSSD and nscd use their own
independent caching, so using nscd in setups where sssd is also serving
users from some remote domain (LDAP, AD, ...) can result in a bit of
unpredictability.
More details about why Fedora chose to use sss before files can be found
on e.g.:
https://fedoraproject.org//wiki/Changes/SSSDCacheForLocalUsers
or:
https://docs.pagure.org/SSSD.sssd/design_pages/files_provider.html
Now, even though sssd watches the passwd and group files with the help
of inotify, there can still be a small window where someone requests a
user or a group, finds that it doesn't exist, adds the entry and checks
again. Without some support in shadow-utils that would explicitly drop
the sssd caches, the inotify watch can fire a little late, so a
combination of commands like this:
getent passwd user || useradd user; getent passwd user
can result in the second getent passwd not finding the newly added user
as the racy behaviour might still return the cached negative hit from
the first getent passwd.
This patch more or less copies the already existing support that
shadow-utils had for dropping nscd caches, except using the "sss_cache"
tool that sssd ships.
This allows shadow-utils to build on systems like Adélie, which have no
<utmp.h> header or `struct utmp`. We use a <utmpx.h>-based daemon,
utmps[1], which uses `struct utmpx` only.
Tested both `login` and `logoutd` with utmps and both work correctly.
[1]: http://skarnet.org/software/utmps/
Enable the automake feature to produce silent output by default.
When compiling code, we now see things like:
$ make
CC addgrps.o
CC age.o
CC audit_help.o
...
This can be disabled via configure's --disable-silent-rules or
by passing V=1 to make.
Custom output (like in the man subdirs) don't (yet) respect this
feature. More work will be needed to clean those up.
Since xz is fairly common nowadays, and is typically smaller/faster than
bzip2 for people to decompress, switch shadow over too. We also merge
the two init locations into configure.ac to match newer autotools style.
The min automake version is bumped to 1.11 too since that's when xz was
released.
The autoconf/automake guys want AC_INIT to be passed the details of the
package directly rather than going through AM_INIT_AUTOMAKE. Update them
both to use the newer style.
This also allows us to pass in contact details for the project.
We set the minimum autoconf version to 2.64 as that's the first one to
support passing the homepage URL in to AC_INIT. That's a pretty old
release by now, so it shouldn't be a problem.
