The netgroups file parsing code tries to access the character before
the newline in parsed lines to see if it is a backslash (\). This
results in an access before the block allocated for the line if the
line is blank, i.e. does not have anything other than the newline
character. This doesn't seem like it will cause any crashes because
the byte belongs to the malloc metadata block and hence access to it
will always succeed.
There could be an invalid alteration in code flow where a blank line
is seen as a continuation due to the preceding byte *happening* to be
'\\'. This could be done by interposing malloc, but that's not really
a security problem since one could interpose getnetgrent_r itself and
achieve a similar 'exploit'.
The possibility of actually exploiting this is remote to impossible
since it also requires the previous line to end with a '\\', which
would happen only on invalid configurations.
AF_INET lookup in hosts file uses _nss_files_gethostbyname2_r, which
is not capable of returning a canonical name if it has found one.
This change adds _nss_files_gethostbyname3_r, which wraps around
_nss_files_gethostbyname2_r and then returns result.h_name as the
canonical name.
Currently for AF_INET lookups from the hosts file, buffer sizes larger
than INT_MAX silently overflow and may result in access beyond bounds
of a buffer. This happens when the number of results in an AF_INET
lookup in /etc/hosts are very large.
There are two aspects to the problem. One problem is that the size
computed from the buffer size is stored into an int, which results in
overflow for large sizes. Additionally, even if this size was
expanded, the function used to read content into the buffer (fgets)
accepts only int sizes. As a result, the fix is to have a function
wrap around fgets that calls it multiple times with int sizes if
necessary.
Fixes BZ #15339.
NSS_STATUS_UNAVAIL may mean that a necessary input resource is not
available. This could occur in a number of cases including when the
network is down, system runs out of file descriptors, etc. The
correct differentiator in such a case is the h_errno, which gives the
nature of failure. In case of failures other than a simple 'not
found', we set h_errno as NETDB_INTERNAL and let errno be the
identifier for the exact error.
These prototypes are duplicated in many places. Add a dedicated
header for holding prototypes for program-specific functions to
avoid that.
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
When glibc is built with --enable-static-nss, the warning that
using NSS symbols requires the nss shared objects to be present
is no longer true, as those symbols are built into libc. Suppress
the warning for those symbols by providing a new macro
(nss_interface_function) for the NSS functions that is defined as
static_link_warning in the normal case, and empty for static NSS.
limit
[BZ #14307]
* sysdeps/posix/getaddrinfo.c (gaih_inet): Increase the size of
the temporary buffer used to invoke __gethostbyname2_r,
__gethostbyaddr_r and gethostbyname4_r to make room for struct
host_data / struct gaih_addrtuple.
* resolv/nss_dns/dns-host.c (global scope): Move definition of
implementation constants MAX_NR_ALIASES and MAX_NR_ADDRS to
header file nss/nsswitch.h.
* nss/nsswitch.h (global scope): Add definition of implementation
constants MAX_NR_ALIASES and MAX_NR_ADDRS (moved from
resolv/nss_dns/dns-host.c).
Compiling on Linux/i586 I get these warnings:
nss_db/db-initgroups.c:60:3: warning: implicit declaration of function
'strlen' [-Wimplicit-function-declaration]
nss_db/db-initgroups.c:74:7: warning: implicit declaration of function
'strncmp' [-Wimplicit-function-declaration]
Fixed with inclusion of <string.h>
Siddhesh Poyarekar