Previously, the allocation was optimized for an outdated
deployment style (that of /etc/group alongside nss_db). The issue
here is that this results in extremely poor performance when using
SSSD, Winbind or nss_ldap.
There were actually two serious bugs here that have been addressed:
1) Running getgrent() loops won't work in most SSSD or Winbind
environments, as full group enumeration is disabled by default.
This could easily result in auto-allocating a group that was
already in use. (This might result in a security issue as well, if
the shared GID is a privileged group).
2) For system groups, the loop was always iterating through the
complete SYS_GID_MIN->SYS_GID_MAX range. On SSSD and Winbind, this
means hundreds of round-trips to LDAP (unless the GIDs were
specifically configured to be ignored by the SSSD or winbindd).
To a user with a slow connection to their LDAP server, this would
appear as if groupadd -r was hung. (Though it would eventually
complete).
This patch changes the algorithm to be more favorable for LDAP
environments, at the expense of some performance when using nss_db.
Given that the DB is a local service, this should have a negligible
effect from a user's perspective.
With the new algorithm, we simply first iterate through all entries
in the local database with gr_next(), recording the IDs that are in
use. We then start from the highest presumed-available entry and
call getgrgid() to see if it is available. We continue this until
we come to the first unused GID. We then select that and return it.
If we make it through all the remaining IDs without finding a free
one, we start over from the beginning of the range and try to find
room in one of the gaps in the range.
The patch was originally written by Stephen Gallagher and applied
identically also to the user allocation by Tomáš Mráz.
Signed-off-by: Serge Hallyn <serge@hallyn.com>
invalid configuration.
* libmisc/find_new_gid.c, libmisc/find_new_uid.c: Updated
comments.
* libmisc/find_new_gid.c, libmisc/find_new_uid.c: Be more strict
on the loop stop conditions. Stop if we passed the limit, even if
the limit itself was never noticed.
boolean.
* libmisc/basename.c: Avoid implicit conversion of pointer to
boolean.
* libmisc/basename.c, lib/prototypes.h (Basename): Return a
constant string.
* libmisc/basename.c, libmisc/obscure.c, lib/prototypes.h,
libmisc/xmalloc.c, libmisc/getdate.h, libmisc/system.c,
libmisc/getgr_nam_gid.c, libmisc/failure.c, libmisc/valid.c: Add
splint annotations.
* libmisc/chowndir.c: Avoid memory leak.
* libmisc/chowndir.c: Do not check *printf/*puts return value.
* libmisc/chowntty.c: Avoid implicit conversion between integer
types.
* libmisc/obscure.c: Return a bool when possible instead of int.
* libmisc/shell.c: Do not check *printf/*puts return value.
* libmisc/shell.c: Do not check execle return value.
* libmisc/setupenv.c: Avoid implicit conversion between integer
types.
* libmisc/xmalloc.c: size should not be zero to avoid returning
NULL pointers.
* libmisc/hushed.c: Do not check *printf/*puts return value.
* libmisc/system.c: Avoid implicit conversion of integer to
boolean. safe_system last argument is a boolean.
* libmisc/system.c: Check return value of dup2.
* libmisc/system.c: Do not check *printf/*puts return value.
* libmisc/system.c: Do not check execve return value.
* libmisc/salt.c: Do not check *printf/*puts return value.
* libmisc/loginprompt.c: Do not check gethostname return value.
* libmisc/find_new_gid.c, libmisc/find_new_uid.c: Do not check
gr_rewind/pw_rewind return value.
* libmisc/ttytype.c: Limit the number of parsed characters in the
sscanf format.
* libmisc/ttytype.c: Test if a type was really read.
* libmisc/sub.c: Do not check *printf/*puts return value.
* libmisc/sub.c: Avoid implicit conversion of integer to boolean.
* src/userdel.c: Fix typo in comment.
* src/userdel.c: Avoid implicit conversion of boolean to integer.
* src/userdel.c: safe_system last argument is a boolean.
* src/newusers.c: Avoid implicit conversion of boolean to integer.
* src/newusers.c: Avoid implicit conversion of integer to boolean.
* src/usermod.c: Add brackets.
* src/usermod.c: Avoid implicit conversion of characters or
integers to booleans.
* src/vipw.c: Avoid implicit conversion of integer to boolean.
* src/su.c: Avoid implicit conversion of integer to boolean.
* src/su.c: Add brackets.
* src/useradd.c: Avoid implicit conversion of characters or
integers to booleans.
no more used.
* lib/groupmem.c: Limit the scope of variable i.
* lib/shadow.c: Avoid implicit conversion of pointers and integers
to booleans.
* lib/shadow.c: Added brackets.
* libmisc/limits.c: Limit the scope of variable tmpmask.
* libmisc/copydir.c: Close opened file on failure.
* libmisc/loginprompt.c: Limit the scope of variable envc.
* libmisc/find_new_uid.c, libmisc/find_new_gid.c: Limit the scope
of variable id.
* NEWS, libmisc/find_new_gid.c, libmisc/find_new_uid.c: Since
system accounts are allocated from SYS_?ID_MIN to SYS_?ID_MAX in
reverse order, accounts are packed close to SYS_?ID_MAX if
SYS_?ID_MIN is already used but there are still dome gaps.
getpwent / getgrent for system accounts. Trying the low-IDs with
getpwuid / getgrgid should be more efficient on LDAP configured
systems with many accounts.
used_gids.
* libmisc/find_new_gid.c: Use getdef_ulong and cast to git_t to
get GID values.
* libmisc/find_new_gid.c: Use UL as a prefix for ulong values.
* libmisc/find_new_uid.c: Likewise.
* src/pwck.c: Only unlock files if they were locked before (e.g.
not in read-only mode).
* src/pwck.c: Quote the username in error messages (harmonization
with other messages).
* libmisc/find_new_gid.c: Fixed typo (s/grp->gr_gid/group_id/).
* libmisc/find_new_gid.c: Likewise.
Thanks to Peter Vrabec.
* NEWS, libmisc/find_new_gid.c, libmisc/find_new_uid.c: Build an
index of used IDs to avoid a database request for each id in the
allowed range (when the highest allowed ID is already used).
This speedups the addition of users or groups when the highest
allowed ID is already used. The additional memory usage of the
tools should be acceptable when UID_MAX/SYS_UID_MAX are set to a
reasonable number.
src/newusers.c, src/pwconv.c, src/chpasswd.c, src/logoutd.c,
src/chfn.c, src/groupmems.c, src/usermod.c, src/pwunconv.c,
src/expiry.c, src/groupdel.c, src/chgpasswd.c, src/useradd.c,
src/su.c, src/groupmod.c, src/passwd.c, src/pwck.c,
src/groupadd.c, src/chage.c, src/login.c, src/grpconv.c,
src/groups.c, src/grpunconv.c, src/chsh.c: Prog is now global (not
static to the file) so that it can be used by the helper functions
of libmisc.
* lib/prototypes.h: Added extern char *Prog.
* libmisc/find_new_gid.c, libmisc/find_new_uid.c: Indicate the
program name with the warning.
libmisc/find_new_uid.c, libmisc/Makefile.am, lib/prototypes.h:
Split find_new_ids.c into find_new_gid.c and find_new_uid.c to
ease the description of login.defs variables in the different
tools.
