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.
These files list the set of subordinate uids and gids that users are allowed
to use. The expect use case is with the user namespace but other uses are
allowed.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
libmisc/copydir.c, lib/selinux.c: Move set_selinux_file_context()
and reset_selinux_file_context() from libmisc/copydir.c to
lib/selinux.c.
* lib/commonio.c: Use set_selinux_file_context() and
reset_selinux_file_context() instead of using the existing
database SELinux context to set the context for the newly created
files.
* lib/prototypes, libmisc/basename.c (Basename): Input is a
constant string.
* lib/prototypes.h, lib/spawn.h, lib/spawn.c, src/userdel.c,
lib/nscd.c, lib/Makefile.am: Delete spawn.h. Move from spawn.h to
prototypes.h.
* src/userdel.c: Remove unused variables.
* lib/nscd.c: Remove unused header files.
* lib/nscd.c: Add the program name to error messages.
* lib/nscd.c: Indicate when nscd does not terminate normally (signal).
* lib/spawn.c: Updated header.
* lib/spawn.c: Flush stdout and stderr to avoid inheriting from
ongoing buffers.
* lib/spawn.c: Avoid implicit conversion of pointer to boolean.
* lib/spawn.c: Replace perror by a complete message.
* lib/spawn.c: Continue to wait for the child if another child
terminates.
* lib/prototypes.h: The name field from cleanup_info_mod is a
constant string. (username).
* lib/Makefile.am: Added lib/spawn.c and lib/spawn.h.
* lib/nscd.c, lib/spawn.c, lib/spawn.h: It is not possible to
differentiate between an nscd failure, and a failure to execute
due to no nscd with posix_spawn. Use our own run_command routine.
* src/userdel.c: Use run_command()
entry validity before commits to databases.
* libmisc/fields.c, libmisc/Makefile.am, lib/fields.c,
lib/Makefile.am, po/POTFILES.in: fields.c moved from libmisc to
lib.
* NEWS: Add support for TCB.
* lib/tcbfuncs.h, lib/tcbfuncs.c, lib/Makefile.am: New library to
support TCB.
* lib/prototypes, libmisc/copydir.c (remove_tree): Add boolean
parameter remove_root.
* configure.in: Add conditional WITH_TCB.
* src/userdel.c, src/usermod.c: Add support for TCB. Update call to
remove_tree().
* src/pwconv.c, src/pwunconv.c: Should not be used with TCB enabled.
* src/vipw.c: Add support for TCB. Update call to remove_tree().
* src/useradd.c: Add support for TCB. Open the shadow file outside
of open_files().
* src/chage.c: Add support for TCB.
* src/Makefile.am: Install passwd sgid shadow when TCB is enabled.
* lib/getdefs.c, man/vipw.8.xml, man/login.defs.5.xml,
man/login.defs/TCB_AUTH_GROUP.xml, man/login.defs/USE_TCB.xml,
man/login.defs/TCB_SYMLINKS.xml, man/generate_mans.mak,
man/generate_mans.deps, man/Makefile.am: New configuration
parameters: TCB_AUTH_GROUP, TCB_SYMLINKS, USE_TCB.
* lib/shadowio.c, lib/commonio.c: Add support for TCB.
skey and md libraries...
* src/Makefile.am: ...Specify for each binary which library is
required. skey and md are required for the binaries with
authentication of the user (chfn, chsh, login, passwd, su). intl
is required for all. mcrypt is required for user (chfn, chsh,
login, passwd, su, sulogin) and group (newgrp, gpasswd)
authentication and for the creation of passwords (chpasswd,
chgpasswd, gpasswd, newusers, passwd).
