* src/su.c (check_perms): Do not silently truncate user name.
Reported-by: Paul Eggert <eggert@cs.ucla.edu>
Co-developed-by: Paul Eggert <eggert@cs.ucla.edu>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
Reviewed-by: Iker Pedrosa <ipedrosa@redhat.com>
This commit will serve to document why we shouldn't worry about the
truncation in the call to strlcpy(3). Since we have one more byte in
tmptty than in full_tty, truncation will produce a string that is at
least one byte longer than full_tty. Such a string could never compare
equal, so we're actually handling the truncation in a clever way. Maybe
too clever, but that's why I'm documenting it here.
Now, about the simplification itself:
Since we made sure that both full_tty and tmptty are null-terminated, we
can call strcmp(3) instead of strncmp(3). We can also simplify the
return logic avoiding one branch.
Cc: Paul Eggert <eggert@cs.ucla.edu>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
Reviewed-by: Iker Pedrosa <ipedrosa@redhat.com>
* libmisc/utmp.c (is_my_tty): Declare the parameter as a char array,
not char *, as it is not necessarily null-terminated.
Avoid a read overrun when reading 'tty', which comes from
'ut_utname'.
Reported-by: Paul Eggert <eggert@cs.ucla.edu>
Co-developed-by: Paul Eggert <eggert@cs.ucla.edu>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
Reviewed-by: Iker Pedrosa <ipedrosa@redhat.com>
* libmisc/date_to_str.c (date_to_str): Do not crash if gmtime(3)
returns NULL because the timestamp is far in the future.
Reported-by: Paul Eggert <eggert@cs.ucla.edu>
Co-developed-by: Paul Eggert <eggert@cs.ucla.edu>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
Reviewed-by: Iker Pedrosa <ipedrosa@redhat.com>
* lib/gshadow.c (sgetsgent): Use strcpy(3) not strlcpy(3),
since the string is known to fit.
Signed-off-by: Paul Eggert <eggert@cs.ucla.edu>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
Reviewed-by: Iker Pedrosa <ipedrosa@redhat.com>
* lib/fields.c (change_field): Don't point
before array start; that has undefined behavior.
Signed-off-by: Paul Eggert <eggert@cs.ucla.edu>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
Reviewed-by: Iker Pedrosa <ipedrosa@redhat.com>
* lib/fields.c (change_field): Since we know the string fits,
use strcpy(3) rather than strlcpy(3).
Signed-off-by: Paul Eggert <eggert@cs.ucla.edu>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
Reviewed-by: Iker Pedrosa <ipedrosa@redhat.com>
gettime.c:25:30: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
/*@observer@*/time_t gettime ()
^
void
shellcheck warns against using echo with flags, as posix sh won't
support it. It suggests using printf, so let's do that.
Signed-off-by: Serge Hallyn <serge@hallyn.com>
bc github...
For some reason, the first test - ONLY on github - seems to not
give the '$ ' prompt expected when you spawn 'su testsuite'.
So just run the first test twice, and ignore the first failure.
It messes with the expected results.
We can do better than this in the expect scripts, but let's
get things running for now.
Signed-off-by: Serge Hallyn <serge@hallyn.com>
write_mapping() will do the following:
openat(proc_dir_fd, map_file, O_WRONLY);
An attacker could create a directory containing a symlink named
"uid_map" pointing to any file owned by root, and thus allow him to
overwrite any root-owned file.
Closes#635
newuidmap and newgidmap currently take an integner pid as
the first argument, determining the process id on which to
act. Accept also "fd:N", where N must be an open file
descriptor to the /proc/pid directory for the process to
act upon. This way, if you
exec 10</proc/99
newuidmap fd:10 100000 0 65536
and pid 99 dies and a new process happens to take pid 99 before
newuidmap happens to do its work, then since newuidmap will use
openat() using fd 10, it won't change the mapping for the new
process.
Example:
// terminal 1:
serge@jerom ~/src/nsexec$ ./nsexec -W -s 0 -S 0 -U
about to unshare with 10000000
Press any key to exec (I am 129176)
// terminal 2:
serge@jerom ~/src/shadow$ exec 10</proc/129176
serge@jerom ~/src/shadow$ sudo chown root src/newuidmap src/newgidmap
serge@jerom ~/src/shadow$ sudo chmod u+s src/newuidmap
serge@jerom ~/src/shadow$ sudo chmod u+s src/newgidmap
serge@jerom ~/src/shadow$ ./src/newuidmap fd:10 0 100000 10
serge@jerom ~/src/shadow$ ./src/newgidmap fd:10 0 100000 10
// Terminal 1:
uid=0(root) gid=0(root) groups=0(root)
Signed-off-by: Serge Hallyn <serge@hallyn.com>
We can't use a pointer that was input to realloc(3), nor any pointers
that point to reallocated memory, without making sure that the memory
wasn't moved. If we do, the Behavior is Undefined.
Signed-off-by: Alejandro Colomar <alx@kernel.org>
Use of these macros, apart from the benefits mentioned in the commit
that adds the macros, has some other good side effects:
- Consistency in getting the size of the object from sizeof(type),
instead of a mix of sizeof(type) sometimes and sizeof(*p) other
times.
- More readable code: no casts, and no sizeof(), so also shorter lines
that we don't need to cut.
- Consistency in using array allocation calls for allocations of arrays
of objects, even when the object size is 1.
Cc: Valentin V. Bartenev <vbartenev@gmail.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
This macros have several benefits over the standard functions:
- The type of the allocated object (not the pointer) is specified as an
argument, which improves readability:
- It is directly obvious what is the type of the object just by
reading the macro call.
- It allows grepping for all allocations of a given type.
This is admittedly similar to using sizeof() to get the size of the
object, but we'll see why this is better.
- In the case of reallocation macros, an extra check is performed to
make sure that the previous pointer was compatible with the allocated
type, which can avoid some mistakes.
- The cast is performed automatically, with a pointer type derived from
the type of the object. This is the best point of this macro, since
it does an automatic cast, where there's no chance of typos.
Usually, programmers have to decide whether to cast or not the result
of malloc(3). Casts usually hide warnings, so are to be avoided.
However, these functions already return a void *, so a cast doesn't
really add much danger. Moreover, a cast can even add warnings in
this exceptional case, if the type of the cast is different than the
type of the assigned pointer. Performing a manual cast is still not
perfect, since there are chances that a mistake will be done, and
even ignoring accidents, they clutter code, hurting readability.
And now we have a cast that is synced with sizeof.
- Whenever the type of the object changes, since we perform an explicit
cast to the old type, there will be a warning due to type mismatch in
the assignment, so we'll be able to see all lines that are affected
by such a change. This is especially important, since changing the
type of a variable and missing to update an allocation call far away
from the declaration is easy, and the consequences can be quite bad.
Cc: Valentin V. Bartenev <vbartenev@gmail.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
We'll expand the contents in a following commit, so let's move the file
to a more generic name, have a dedicated header, and update includes.
Signed-off-by: Alejandro Colomar <alx@kernel.org>
Use the new header for xstrdup()
Signed-off-by: Alejandro Colomar <alx@kernel.org>
This is guaranteed by ISO C. Now that we require ISO C (and even POSIX)
to compile, we can simplify this code.
Signed-off-by: Alejandro Colomar <alx@kernel.org>
