The resolv/res_debug.c function p_secstodate (which is a public
function exported from libresolv, taking an unsigned long argument)
does:
struct tm timebuf;
time = __gmtime_r(&clock, &timebuf);
time->tm_year += 1900;
time->tm_mon += 1;
sprintf(output, "%04d%02d%02d%02d%02d%02d",
time->tm_year, time->tm_mon, time->tm_mday,
time->tm_hour, time->tm_min, time->tm_sec);
If __gmtime_r returns NULL (because the year overflows the range of
int), this will dereference a null pointer. Otherwise, if the
computed year does not fit in four characters, this will cause a
buffer overrun of the fixed-size 15-byte buffer. With current GCC
mainline, there is a compilation failure because of the possible
buffer overrun.
I couldn't find a specification for how this function is meant to
behave, but Paul pointed to RFC 4034 as relevant to the cases where
this function is called from within glibc. The function's interface
is inherently problematic when dates beyond Y2038 might be involved,
because of the ambiguity in how to interpret 32-bit timestamps as such
dates (the RFC suggests interpreting times as being within 68 years of
the present date, which would mean some kind of interface whose
behavior depends on the present date).
This patch works on the basis of making a minimal fix in preparation
for obsoleting the function. The function is made to handle times in
the interval [0, 0x7fffffff] only, on all platforms, with <overflow>
used as the output string in other cases (and errno set to EOVERFLOW
in such cases). This seems to be a reasonable state for the function
to be in when made a compat symbol by a future patch, being compatible
with any existing uses for existing timestamps without trying to work
for later timestamps. Results independent of the range of time_t also
simplify the testcase.
I couldn't persuade GCC to recognize the ranges of the struct tm
fields by adding explicit range checks with a call to
__builtin_unreachable if outside the range (this looks similar to
<https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80776>), so having added
a range check on the input, this patch then disables the
-Wformat-overflow= warning for the sprintf call (I prefer that to the
use of strftime, as being more transparently correct without knowing
what each of %m and %M etc. is).
I do not know why this build failure should be new with mainline GCC
(that is, I don't know what GCC change might have introduced it, when
the basic functionality for such warnings was already in GCC 7).
I do not know if this is a security issue (that is, if there are
plausible ways in which a date before -999 or after 9999 from an
untrusted source might end up in this function). The system clock is
arguably an untrusted source (in that e.g. NTP is insecure), but
probably not to that extent (NTP can't communicate such wild
timestamps), and uses from within glibc are limited to 32-bit inputs.
Tested with build-many-glibcs.py that this restores the build for arm
with yesterday's mainline GCC. Also tested for x86_64 and x86.
[BZ #22463]
* resolv/res_debug.c: Include <libc-diag.h>.
(p_secstodate): Assert time_t at least as wide as u_long. On
overflow, use integer seconds since the epoch as output, or use
"<overflow>" as output and set errno to EOVERFLOW if integer
seconds since the epoch would be 14 or more characters.
(p_secstodate) [__GNUC_PREREQ (7, 0)]: Disable -Wformat-overflow=
for sprintf call.
* resolv/tst-p_secstodate.c: New file.
* resolv/Makefile (tests): Add tst-p_secstodate.
($(objpfx)tst-p_secstodate): Depend on $(objpfx)libresolv.so.
res_hnok rejected some host names used on the Internet, such as
www-.example.com. res_hnok and res_dnok failed to perform basic syntax
checking on DNS domain names.
Also fix res_mailok, res_ownok.
Remove the bogus targets (and source) that supposedly build ga_test.
This code was added to resolv very early in the development process
but does not appear to be an actual test program. The target for
building this file is tests but because the glibc Make system is
built the way it is, the target is overriden by higher-level tests
targets and, therefore, the ga_test program is never built. Removing
the target and the source code makes the resolv/Makefile less confusing.
Tested by building and running 'make check' on 64 bit host running
Kernel 4.10.0-19 configured with
--prefix=/home/hawkinsw/code/glibc-build/install
--enable-hardcoded-path-in-tests
--disable-mathvec
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Various subdirectories of glibc include Banner files to put some text
in the output of executing libc.so.6, under "Available extensions".
Some of those subdirectories (e.g. crypt) may originally have been
add-ons (and so optional, so a particular glibc build might or might
not have included them), but except for libidn they aren't now (or if
only included in some builds, in the case of soft-fp, the inclusion
depends on the architecture for which glibc is configured rather than
having any glibc configuration for which it's an optional feature),
and it doesn't seem useful for the libc.so.6 output to call out a few
features like that.
This patch removes the non-add-on Banner files, updating contrib.texi
where they noted contributions not otherwise mentioned there.
Tested for x86_64.
* crypt/Banner: Remove file.
* nptl/Banner: Likewise.
* resolv/Banner: Likewise.
* soft-fp/Banner: Likewise.
* nptl/Makefile ($(objpfx)banner.h): Remove rule.
($(objpfx)version.d): Remove dependency on banner.h.
($(objpfx)version.os): Likewise.
* nptl/version.c (banner): Do not include banner.h.
* manual/contrib.texi: Update entries for Richard Henderson, Jakub
Jelinek and BIND code.
The old code uses errno as the primary indicator for success or
failure. This is wrong because errno is only set for specific
combinations of the status return value and the h_errno variable.
This patch consolidates all the non cancellable writev calls to use
the __writev_nocancel identifier. For non cancellable targets it will
be just a macro to call the default respective symbol while on Linux
will be a internal one.
Checked on x86_64-linux-gnu, x86_64-linux-gnu-x32, and i686-linux-gnu.
* gmon/gmon.c (write_hist): Replace writev_not_cancel_no_status with
__writev_nocancel_nostatus.
(write_call_graph): Likewise.
(write_bb_counts): Likewise.
* resolv/herror.c (herror): Likewise.
* sysdeps/generic/not-cancel.h (writev_not_cancel_no_status): Remove
macro.
(__writev_nocancel_nostatus): New macro.
* sysdeps/unix/sysv/linux/not-cancel.h (writev_not_cancel_no_status):
Remove macro.
(__writev_nocancel_nostatus): New function.
A dot-less host name without an /etc/resolv.conf file caused an
assertion failure in update_from_conf because the function would not
deal correctly with the empty search list case.
Thanks to Andreas Schwab for debugging assistence.
This commit enhances the stub resolver to reload the configuration
in the per-thread _res object if the /etc/resolv.conf file has
changed. The resolver checks whether the application has modified
_res and will not overwrite the _res object in that case.
The struct resolv_context mechanism is used to check the
configuration file only once per name lookup.
This commit adds the remaining unchanging members (which are loaded
from /etc/resolv.conf) to struct resolv_conf.
The extended name server list is currently not used by the stub
resolver. The switch depends on a cleanup: The _u._ext.nssocks
array stores just a single socket, and needs to be replaced with
a single socket value.
(The compatibility gethostname implementation does not use the
extended addres sort list, either. Updating the compat code is
not worthwhile.)
This change uses the extended resolver state in struct resolv_conf to
store the search list. If applications have not patched the _res
object directly, this extended search list will be used by the stub
resolver during name resolution.
This change provides additional resolver configuration state which
is not exposed through the _res ABI. It reuses the existing
initstamp field in the supposedly-private part of _res. Some effort
is undertaken to avoid memory safety issues introduced by applications
which directly patch the _res object.
With this commit, only the initstamp field is moved into struct
resolv_conf. Additional members will be added later, eventually
migrating the entire resolver configuration.
struct resolv_context objects provide a temporary resolver context
which does not change during a name lookup operation. Only when the
outmost context is created, the stub resolver configuration is
verified to be current (at present, only against previous res_init
calls). Subsequent attempts to obtain the context will reuse the
result of the initial verification operation.
struct resolv_context can also be extended in the future to store
data which needs to be deallocated during thread cancellation.
Some Linux kernels have very aggressive ICMP rate limiting on the
loopback interface. This commit introduces a minimal echoing DNS server
inside the network namespace, so that there is no need for ICMP error
messages anymore.
