Implement it as an inline function, and add restrict and ATTR_STRING()
and ATTR_ACCESS() as appropriate.
Reviewed-by: "Serge E. Hallyn" <serge@hallyn.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
Implement it as an inline function, and add restrict and ATTR_STRING()
and ATTR_ACCESS() as appropriate.
Reviewed-by: "Serge E. Hallyn" <serge@hallyn.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
In the case of is_unsigned() and is_signed(), the natural thing would be
to compare to 0:
#define is_unsigned(x) (((typeof(x)) -1) > 0)
#define is_signed(x) (((typeof(x)) -1) < 0)
However, that would trigger -Wtype-limits, so we compare against 1,
which silences that, and does the same job.
Signed-off-by: Alejandro Colomar <alx@kernel.org>
This macro makes sure that the first argument is an array, and
calculates its size.
Reviewed-by: "Serge E. Hallyn" <serge@hallyn.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
Adding function check_fds to new file fd.c. The function check_fds
should be called in every setuid/setgid program.
Co-developed-by: Alejandro Colomar <alx@kernel.org>
The function should never be used; it's always used via its wrapper
macro. To simplify, and reduce chances of confusion: remove the
function, and implement the macro directly in terms of
stpcpy(mempcpy(strnlen())).
Update the documentation, and improve the example, which was rather
confusing.
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Cc: Iker Pedrosa <ipedrosa@redhat.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
This fixes build with glibc-2.33 (newer glibc merged libdl and libpthread
into libc):
```
libtool: link: x86_64-pc-linux-gnu-gcc -isystem /usr/include/bsd -DLIBBSD_OVERLAY -O2 -pipe -Wl,-O1 -o login login.o login_nopam.o -Wl,--as-needed ../lib/.libs/libshadow.a -lcrypt -lsystemd -lpam -lpam_misc -lbsd
/usr/lib/gcc/x86_64-pc-linux-gnu/13/../../../../x86_64-pc-linux-gnu/bin/ld: ../lib/.libs/libshadow.a(libshadow_la-nss.o): undefined reference to symbol 'dlclose@@GLIBC_2.2.5'
/usr/lib/gcc/x86_64-pc-linux-gnu/13/../../../../x86_64-pc-linux-gnu/bin/ld: /lib64/libdl.so.2: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status
```
In Debian, the needed macro from libtool seems to be in libltdl-dev.
Signed-off-by: Sam James <sam@gentoo.org>
Uses of this macro indicate a code smell, but in some cases, libc
functions require breaking const correctness. Use this macro to wrap
casts in such cases, so that we limit the danger of the cast.
It only permits discarding const. Discarding any other qualifiers, or
doing other type changes should result in a compile-time error.
Link: <https://software.codidact.com/posts/286575/287345#answer-287345>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
These functions reject negative numbers, instead of silently converting
them into unsigned, which strtou[l]l(3) do.
Reviewed-by: Iker Pedrosa <ipedrosa@redhat.com>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
This wrapper calculates the destination buffer's size, to avoid errors
in the size calculation.
A curious fact: this macro did exist in Version 7 Unix (with a slightly
different name). I found it by chance, investigating the origins of
strncpy(3) and strncat(3) in V7, after Branden suggested me to do so,
related to recent discussions about string_copying(7).
alx@debian:~/src/unix/unix/Research-V7$ grepc SCPYN .
./usr/src/cmd/login.c:#define SCPYN(a, b) strncpy(a, b, sizeof(a))
Our implementation is slightly better, because using nitems() we're
protected against passing a pointer instead of an array, and it's also
conceptually more appropriate: for wide characters, it would be
#define WCSNCPY(dst, src) wcsncpy(dst, src, NITEMS(dst))
Cc: "G. Branden Robinson" <branden@debian.org>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
As other x...() wrappers around functions that allocate, these wrappers
are like [v]asprintf(3), but exit on failure.
Reviewed-by: Iker Pedrosa <ipedrosa@redhat.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
It wraps strlcpy(3bsd) so that it performs some steps that one might
forget, or might be prone to accidents:
- It calculates the size of the destination buffer, and makes sure it's
an array (otherwise, using sizeof(dst) would be very bad).
- It calculates if there's truncation, returning an easy-to-use value.
BTW, this macro doesn't have any issues of double evaluation, because
sizeof() doesn't evaluate its argument (unless it's a VLA, but then
the static_assert(3) within SIZEOF_ARRAY() makes sure VLAs are not
allowed).
Cc: Christian Göttsche <cgzones@googlemail.com>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Iker Pedrosa <ipedrosa@redhat.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
There's no standard function that copies from a null-padded character
sequence into a string.
A few standard functions can be workarounded to do that:
- strncat(3): This function is designed to catenate from a null-padded
character sequence into a string. The catch is that there's no
*cpy() equivalent of it --strncpy(3) is not at all related to
strncat(3); don't be fooled by the confusing name--, so one would
need to zero the first byte before the call to strncat(3). It also
has the inconvenient that it returns a useless value.
- strncpy(3): This function is designed to copy from a string to a
null-padded character sequence; the opposite of what we want to do.
If one passes the size of src instead of the size of dst, and then
manually zeroes the last byte of the dst buffer, something similar
to what we want happens. However, this does more than what we want:
it also padds with NUL the remaining bytes after the terminating NUL.
That extra work can confuse maintainers to believe that it's
necessary. That is exactly what happens in logout.c.
src/logoutd.c-46- /*
src/logoutd.c-47- * ut_user may not have the terminating NUL.
src/logoutd.c-48- */
src/logoutd.c:49: strncpy (user, ut->ut_user, sizeof (ut->ut_user));
src/logoutd.c-50- user[sizeof (ut->ut_user)] = '\0';
In that logout.c case --and in most invocations of strncpy(3), which
is usually a wrong tool-- the extra work is not wanted, so it's
preferrable to use the right tool, a function that does exactly
what's needed and nothing more than that. That tool is zustr2stp().
Read string_copying(7) for a more complete comparison of string copying
functions.
Cc: Christian Göttsche <cgzones@googlemail.com>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Iker Pedrosa <ipedrosa@redhat.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
There's no need to have these as macros, so use functions, which are a
lot safer: there's no need to worry about multiple evaluation of args,
and there's also more type safety. Compiler warnings are also simpler,
as they don't dump all the nested macros.
Cc: Christian Göttsche <cgzones@googlemail.com>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Iker Pedrosa <ipedrosa@redhat.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
Recently, we removed support for 'struct utmpx'. We did it because utmp
and utmpx are identical, and while POSIX specifies utmpx (and not utmp),
GNU/Linux documentation seems to favor utmp. Also, this project
defaulted to utmp, so changing to utmpx would be more dangerous than
keeping old defaults, even if it's supposed to be the same.
Now, I just found more code that didn't make much sense: lib/utent.c
provides definitions for getutent(3) and friends in case the system
doesn't provide them, but we don't provide prototypes for those
definitions, so code using the functions would have never compiled.
Let's just remove these definitions as dead code.
Fixes: 3be7b9d75a ("Remove traces of utmpx")
Fixes: 170b76cdd1 ("Disable utmpx permanently")
Cc: Serge Hallyn <serge@hallyn.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
strlcpy(3) might not be visible since it is declared in <bsd/string.h>.
This can lead to warnings, like:
fields.c: In function 'change_field':
fields.c:103:17: warning: implicit declaration of function 'strlcpy'; did you mean 'strncpy'? [-Wimplicit-function-declaration]
103 | strlcpy (buf, cp, maxsize);
| ^~~~~~~
| strncpy
../lib/fields.c:103:17: warning: type of 'strlcpy' does not match original declaration [-Wlto-type-mismatch]
103 | strlcpy (buf, cp, maxsize);
| ^
/usr/include/bsd/string.h:44:8: note: return value type mismatch
44 | size_t strlcpy(char *dst, const char *src, size_t siz);
| ^
/usr/include/bsd/string.h:44:8: note: type 'size_t' should match type 'int'
/usr/include/bsd/string.h:44:8: note: 'strlcpy' was previously declared here
/usr/include/bsd/string.h:44:8: note: code may be misoptimized unless '-fno-strict-aliasing' is used
There's a better way to do this, and I hope to clean that up,
but this fixes out of tree builds for me right now.
Closes#386
Signed-off-by: Serge Hallyn <serge@hallyn.com>
Closes#154
When starting any operation to do with subuid delegation, check
nsswitch for a module to use. If none is specified, then use
the traditional /etc/subuid and /etc/subgid files.
Currently only one module is supported, and there is no fallback
to the files on errors. Several possibilities could be considered:
1. in case of connection error, fall back to files
2. in case of unknown user, also fall back to files
etc...
When non-files nss module is used, functions to edit the range
are not supported. It may make sense to support it, but it also
may make sense to require another tool to be used.
libsubordinateio also uses the nss_ helpers. This is how for instance
lxc could easily be converted to supporting nsswitch.
Add a set of test cases, including a dummy libsubid_zzz module. This
hardcodes values such that:
'ubuntu' gets 200000 - 300000
'user1' gets 100000 - 165536
'error' emulates an nss module error
'unknown' emulates a user unknown to the nss module
'conn' emulates a connection error ot the nss module
Changes to libsubid:
Change the list_owner_ranges api: return a count instead of making the array
null terminated.
This is a breaking change, so bump the libsubid abi major number.
Rename free_subuid_range and free_subgid_range to ungrant_subuid_range,
because otherwise it's confusing with free_subid_ranges which frees
memory.
Run libsubid tests in jenkins
Switch argument order in find_subid_owners
Move the db locking into subordinateio.c
Signed-off-by: Serge Hallyn <serge@hallyn.com>
With this, it is possible for Linux distributors to store their
supplied default configuration files somewhere below /usr, while
/etc only contains the changes made by the user. The new option
--enable-vendordir defines where the shadow suite should additional
look for login.defs if this file is not in /etc.
libeconf is a key/value configuration file reading library, which
handles the split of configuration files in different locations
and merges them transparently for the application.
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>
