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Author SHA1 Message Date
Nicholas J. Kain
27c9e2c553 Improve fingerprinting to support DHCP relay agents. 
Mostly reverts the previous commit and instead teaches ndhc to properly
handle the case when it is communicating with a DHCP relay agent on
its local segment rather than directly with a DHCP server.
 2015-02-12 23:28:54 -05:00
Nicholas J. Kain
a395234a67 Support networks with relay agents that have the DHCP server on a 
different segment.

The network fingerprinting would never complete if the DHCP server was
on a different segment before this change, since it would be impossible
for the ARP messages sent by ndhc to ever reach the DHCP server
(and vice-versa).

Now just give up trying to find the hardware address after two tries
and assume that the DHCP server cannot be reached by ARP.

An alternative would be to fingerprint the relay agent instead, but
to do so would require a lot more work as the giaddr field is only
meaningful in the client->server message path, not in the
server->client path.  Thus it would require gathering the source IP
for DHCP replies sent by unicast or broadcast and ferrying along
this information to the ARP checking code where it would be used
in place of the DHCP server address.

This is entirely possible to do, but is quite a bit more work.
 2015-02-12 20:49:40 -05:00
Nicholas J. Kain
03fc696267 Update the man page and correct some formatting errors. 2015-02-12 19:03:09 -05:00
Nicholas J. Kain
9d8d653877 CMake: Do not try to test for the glibc version when cross-compiling. 2015-02-12 18:46:44 -05:00
Nicholas J. Kain
b792162113 Add CROSSCOMPILE_MACHINENAME environment variable for CMake that 
will allow the host machine type detection to be skipped and
the target MACHINENAME to be manually defined.
 2015-02-12 13:35:50 -05:00
Nicholas J. Kain
8e4ea0be72 CMake: Only add -lrt link dependency if glibc is detected. 2015-02-12 13:05:30 -05:00
Nicholas J. Kain
6f6aad211e Documentation update. 2015-01-10 18:34:51 -05:00
Nicholas J. Kain
9f87bd8b30 udp_checksum(): Clamp the value of the UDP packet header length. 
Without this change, it is possible for malicious UDP packets to
make the function read past the end of a buffer.

If this was ever a possibility in ndhc, the previous commit fixed
that issue, but there is no reason for udp_checksum() to have
such a subtle precondition to proper use.  This change also makes
it easier to audit correctness.
 2015-01-06 07:07:08 -05:00
Nicholas J. Kain
6548b5ce54 get_raw_packet(): Perform the UDP checksum after the packet length 
checks.

This change makes it easier to verify that there can be no reads
beyond a buffer end by udp_checksum().
 2015-01-06 04:32:58 -05:00
Nicholas J. Kain
c8dcf5a06b Make sure that received DHCP packets have a valid options end marker. 2015-01-06 04:02:52 -05:00
Nicholas J. Kain
94c107d465 Make sure all sockets are set NONBLOCK so that writes do not block. 2014-08-19 11:09:59 -04:00
Nicholas J. Kain
12114c9bae Add more explicit length checks for get_raw_packet. 2014-07-25 20:34:01 -04:00
Nicholas J. Kain
2518e0a2bc Use SO_LOCK_FILTER to ensure that BPF filters cannot be removed once attached. 
This facility was added to Linux in early 2013.  If it is not available,
the BPF will still be installed, but redundant checks will be performed
to guard against the BPF possibly being removed by an attacker.
 2014-06-13 22:37:37 -04:00
Nicholas J. Kain
56e30a0923 Fix the return value for nlmsg_get_error(). 2014-06-13 22:35:57 -04:00
Nicholas J. Kain
ae03b6dd8f Move the ip checksum code out to ncmlib. 2014-06-08 20:34:34 -04:00
Nicholas J. Kain
4a083d3367 get_dhcp_opt() didx argument should be passed as a reference rather 
than relying on the caller re-assigning to didx.  The previous
didx += get_dhcp_opt(...) was wrong and should have used =.
 2014-05-10 21:38:45 -04:00
Nicholas J. Kain
99e21004ea arp_min_close_fd() will always force the arp fd to be equal to -1, so 
there is no need to check force_reopen twice.
 2014-05-10 21:13:24 -04:00
Nicholas J. Kain
3721cc926b Documentation updates. 2014-04-24 18:29:52 -04:00
Nicholas J. Kain
6af0d26351 Remove the obsolete init script for Gentoo's network configuration system. 
My own machines use a process supervision system, so this script is
unmaintained and doesn't work anymore.
 2014-04-24 18:24:00 -04:00
Nicholas J. Kain
2420bed259 Accept no command line arguments without error. 2014-04-21 12:04:13 -04:00
Nicholas J. Kain
dbc91b0811 Background option in config files should be a boolval rathe than a value. 2014-04-21 09:02:58 -04:00
Nicholas J. Kain
034e2bb1db When sockd transfers a file descriptor to ndhc, close the fd in sockd. 
Since the transfer is conceptually a move, this is the correct thing to
do and prevents sockets from spuriously hanging around forever and
eventually exhausting the per process limit on fds.
 2014-04-17 11:04:00 -04:00
Nicholas J. Kain
07cbd88049 Just use raw sockets for listening to DHCP requests. A UDP SO_BROADCAST 
socket was previously used only for receiving RENEWING packets, and it
added needless complexity and was somewhat fragile.
 2014-04-16 01:00:36 -04:00
Nicholas J. Kain
ca85a6ba9f Style cleanups in dhcp.c. 2014-04-16 00:24:40 -04:00
Nicholas J. Kain
d8260b4e63 Print an error message when bind() fails when creating a UDP socket in sockd. 2014-04-16 00:24:13 -04:00
Nicholas J. Kain
0884d96d1e PR_SET_PDEATHSIG is not fully reliable, so instead maintain a pair of 
AF_UNIX SOCK_STREAM sockets between the master processes and each subprocess,
and poll for the HUP event.

At the same time, be specific about the events that are checked in epoll
when dispatching on an event.
 2014-04-15 23:19:24 -04:00
Nicholas J. Kain
e526adce19 Make the signal handling code use safe_read() and unify ifchd and sockd 
signals code.
 2014-04-15 20:55:13 -04:00
Nicholas J. Kain
baa394af9a UDP listen sockets should be requested with 'U' instead of 'u'. 2014-04-15 20:54:35 -04:00
Nicholas J. Kain
b3578737df Update the Makefile to build cfg.c from cfg.rl. 2014-04-15 20:50:54 -04:00
Nicholas J. Kain
b00444ab8b Bound the subprocess lifetime using prctl(PR_SET_PDEATHSIG, ...). 
The pipes wouldn't do this job anymore because they were unused and thus
never performed writes that would generate SIGPIPEs, so the pipes are
removed, too.
 2014-04-15 18:01:01 -04:00
Nicholas J. Kain
b3ce601f20 state.c: Print error messages if we fail to send DHCP packets. 2014-04-15 17:59:15 -04:00
Nicholas J. Kain
18604c5245 get_udp_unicast_socket() needs to have the client address as an argument 
when sending the request to sockd.

Also, print error messages if sockd returns an invalid fd (< 0).
 2014-04-15 17:55:28 -04:00
Nicholas J. Kain
a9055b5ca5 Update more message prints to prefix with the interface name. 2014-04-15 15:24:22 -04:00
Nicholas J. Kain
58b4ba768c If the IP header length does not match the size of the UDP packet received 
via the raw socket, print both lengths in the warning message.
 2014-04-15 15:23:52 -04:00
Nicholas J. Kain
730e5ef310 setpgid() can return EPERM if we are already a process group leader. 2014-04-15 15:02:20 -04:00
Nicholas J. Kain
e5834da6d3 Permit sendmsg in the seccomp syscall whitelist for all daemons. 2014-04-15 14:57:07 -04:00
Nicholas J. Kain
b5f0ccd88d In cfg.rl, when performing clear action, don't clear the cs member in ccfg. 2014-04-15 14:56:35 -04:00
Nicholas J. Kain
a777766cc6 Fix stupid typo in ndhc.c that would cause the clientid option to 
corrupt the start of the hostname option if both were specified.
 2014-04-15 14:55:50 -04:00
Nicholas J. Kain
8a9fbb6f09 Documentation updates. 2014-04-14 18:32:08 -04:00
Nicholas J. Kain
74ad01a086 Update the manual page. 2014-04-14 15:52:39 -04:00
Nicholas J. Kain
a501789e04 Parse config options with ragel and support a configuration file. 2014-04-14 15:06:31 -04:00
Nicholas J. Kain
51033d3664 Detect the glibc version in CMake and link librt if it is required. 
For the Makefile, unconditionally link librt with no detection.
 2014-04-07 19:14:31 -04:00
Nicholas J. Kain
d267c2c44b Use the raw capability interface via updated ncmlib rather than linking 
to libcap.
 2014-04-07 15:05:34 -04:00
Nicholas J. Kain
bb1ff7a506 arp.c: Make logging messages print the associated interface name. 2014-04-07 04:43:21 -04:00
Nicholas J. Kain
74678ef510 Use safe_recvmsg(). 2014-04-07 04:22:32 -04:00
Nicholas J. Kain
6804be2277 Use safe_sendto where necessary, and check for short writes. 
Also, change many log_lines to log_errors, mostly in ifset.c.
 2014-04-07 04:15:02 -04:00
Nicholas J. Kain
650da6a7fd Add recvfrom to the seccomp syscall whitelist. 2014-04-07 03:54:30 -04:00
Nicholas J. Kain
cab9162d8d Remove socketpair from the seccomp syscall filter whitelist. 
socketpair() is called only before privileges are dropped, so it does
not need to be in the whitelist.
 2014-04-07 03:44:53 -04:00
Nicholas J. Kain
5fa2030bab Use a socketpair rather than a pair of pipes for communication between 
ndhc and ifch, similar to sockd.  A single pipe is also maintained so
that SIGPIPE can bound the lifetime of an orphaned ifch process.
 2014-04-07 03:44:02 -04:00
Nicholas J. Kain
e2ee728982 Consolidate all of the global static variables in arp.c into a single 
struct, and use booleans where appropriate.
 2014-04-06 22:12:31 -04:00