oweals/tinc.git
13 years agoVery primitive ECDSA signed ECDH key exchange for the meta protocol.
Guus Sliepen [Thu, 7 Jul 2011 20:30:55 +0000 (22:30 +0200)]
Very primitive ECDSA signed ECDH key exchange for the meta protocol.

Nonces and hash of the ID requests should be included in the seed for the PRF.

13 years agoRead ECDSA keys.
Guus Sliepen [Thu, 7 Jul 2011 20:28:25 +0000 (22:28 +0200)]
Read ECDSA keys.

13 years agoImplement ECDSA sign and verify operations.
Guus Sliepen [Thu, 7 Jul 2011 20:27:17 +0000 (22:27 +0200)]
Implement ECDSA sign and verify operations.

Very basic at the moment, doesn't hash the input first,
and uses OpenSSL's DER encoded signature as output.

13 years agoBump minor protocol to indicate ECDH capability for UDP session keys.
Guus Sliepen [Tue, 5 Jul 2011 19:29:31 +0000 (21:29 +0200)]
Bump minor protocol to indicate ECDH capability for UDP session keys.

13 years agoAdd a minor number to the protocol version.
Guus Sliepen [Tue, 5 Jul 2011 19:19:48 +0000 (21:19 +0200)]
Add a minor number to the protocol version.

13 years agoRound up the size of the secret parts after splitting it in two.
Guus Sliepen [Mon, 4 Jul 2011 05:51:47 +0000 (07:51 +0200)]
Round up the size of the secret parts after splitting it in two.

13 years agoAdd ECDSA key import.
Guus Sliepen [Sun, 3 Jul 2011 21:44:43 +0000 (23:44 +0200)]
Add ECDSA key import.

13 years agoFinish base64 decoding routine.
Guus Sliepen [Sun, 3 Jul 2011 21:33:56 +0000 (23:33 +0200)]
Finish base64 decoding routine.

13 years agoHave tincctl generate ECDSA keys.
Guus Sliepen [Sun, 3 Jul 2011 20:25:29 +0000 (22:25 +0200)]
Have tincctl generate ECDSA keys.

The generate-keys command now generates both an RSA and an ECDSA keypair,
but one can generate-rsa-keys or generate-ecdsa-keys to just generate one type.

13 years agoAdd ECDSA key generation.
Guus Sliepen [Sun, 3 Jul 2011 20:15:00 +0000 (22:15 +0200)]
Add ECDSA key generation.

13 years agoBase64 encoding and decoding functions.
Guus Sliepen [Sun, 3 Jul 2011 20:13:58 +0000 (22:13 +0200)]
Base64 encoding and decoding functions.

13 years agoCleanups in ECDH code.
Guus Sliepen [Sun, 3 Jul 2011 20:13:34 +0000 (22:13 +0200)]
Cleanups in ECDH code.

13 years agoNo need to keep around pointers to EC_GROUP.
Guus Sliepen [Sun, 3 Jul 2011 19:21:37 +0000 (21:21 +0200)]
No need to keep around pointers to EC_GROUP.

13 years agoProper use of PRF.
Guus Sliepen [Sun, 3 Jul 2011 14:30:49 +0000 (16:30 +0200)]
Proper use of PRF.

13 years agoUse PRF.
Guus Sliepen [Sun, 3 Jul 2011 13:59:49 +0000 (15:59 +0200)]
Use PRF.

13 years agoAdd PRF to derive key material from the ECDH shared secret.
Guus Sliepen [Sun, 3 Jul 2011 13:26:58 +0000 (15:26 +0200)]
Add PRF to derive key material from the ECDH shared secret.

It is modelled after the pseudorandom function from RFC4346 (TLS 1.1), the only
significant change is the use of SHA512 and Whirlpool instead of MD5 and SHA1.

13 years agoSupport ECDH key exchange.
Guus Sliepen [Sun, 3 Jul 2011 11:17:28 +0000 (13:17 +0200)]
Support ECDH key exchange.

REQ_KEY requests have an extra field indicating key exchange version.
If it is present and > 0, the sender supports ECDH. If the receiver also
does, then it will generate a new keypair and sends the public key in a
ANS_KEY request with "ECDH:" prefixed. The ans_key_h() function will
compute the shared secret, which, at the moment,is used as is to set the
cipher and HMAC keys. However, this must be changed to use a proper KDF.
In the future, the ECDH key exchange must also be signed.

13 years agoPreliminary implementation of Elliptic Curve Diffie-Hellman Ephemeral key exchange.
Guus Sliepen [Mon, 27 Jun 2011 19:52:23 +0000 (21:52 +0200)]
Preliminary implementation of Elliptic Curve Diffie-Hellman Ephemeral key exchange.

13 years agoAdd manpage for tinc-gui.
Guus Sliepen [Sun, 26 Jun 2011 11:15:44 +0000 (13:15 +0200)]
Add manpage for tinc-gui.

13 years agoRemove debug messages that were printed to stdout.
Guus Sliepen [Sun, 26 Jun 2011 11:14:48 +0000 (13:14 +0200)]
Remove debug messages that were printed to stdout.

13 years agoUpdate documentation to mention pidfiles instead of controlcookies.
Guus Sliepen [Sun, 26 Jun 2011 10:59:11 +0000 (12:59 +0200)]
Update documentation to mention pidfiles instead of controlcookies.

13 years agoDon't react to escape character in tincctl top.
Guus Sliepen [Sun, 26 Jun 2011 10:58:50 +0000 (12:58 +0200)]
Don't react to escape character in tincctl top.

Not only the ESC key generates an escape character, but many other keys
do as well, such as arrow keys.

13 years agoUse pidfile in tinc-gui as well.
Guus Sliepen [Sun, 26 Jun 2011 10:51:25 +0000 (12:51 +0200)]
Use pidfile in tinc-gui as well.

13 years agoReally stable sorting of tincctl top output.
Guus Sliepen [Sat, 25 Jun 2011 20:20:39 +0000 (22:20 +0200)]
Really stable sorting of tincctl top output.

13 years agoAdd +git to the version string.
Guus Sliepen [Sat, 25 Jun 2011 19:38:59 +0000 (21:38 +0200)]
Add +git to the version string.

13 years agoMake pid files backwards compatible and add address of listening socket.
Guus Sliepen [Sat, 25 Jun 2011 19:35:27 +0000 (21:35 +0200)]
Make pid files backwards compatible and add address of listening socket.

The pid is now written first, so that a version 1.0.x tincd can be used to stop
a running version 1.1 tincd.  Getsockname() is used to determine the address of
the first listening socket, so that tincctl can connect to the local tincd even
if AddressFamily = ipv6, or if BindToAddress or BindToInterface is used.

13 years agoRename controlcookie file to pidfile.
Guus Sliepen [Sat, 25 Jun 2011 19:21:36 +0000 (21:21 +0200)]
Rename controlcookie file to pidfile.

13 years agoDon't call exit_control() if we didn't do init_control().
Guus Sliepen [Sat, 25 Jun 2011 19:16:13 +0000 (21:16 +0200)]
Don't call exit_control() if we didn't do init_control().

13 years agoRe-add support for SIGALRM.
Guus Sliepen [Sat, 25 Jun 2011 18:20:07 +0000 (20:20 +0200)]
Re-add support for SIGALRM.

13 years agoMerge Tinc.py into tinc-gui to simplify make install.
Guus Sliepen [Sat, 25 Jun 2011 15:39:02 +0000 (17:39 +0200)]
Merge Tinc.py into tinc-gui to simplify make install.

Autoconf/automake's Python support is strange.

13 years agoThank Scott Lamb, Sven-Haegar Koch and Loïc Grenié in the NEWS file.
Guus Sliepen [Sat, 25 Jun 2011 15:11:05 +0000 (17:11 +0200)]
Thank Scott Lamb, Sven-Haegar Koch and Loïc Grenié in the NEWS file.

13 years agoEnsure the right files end up in the tarball after make dist.
Guus Sliepen [Sat, 25 Jun 2011 15:08:40 +0000 (17:08 +0200)]
Ensure the right files end up in the tarball after make dist.

13 years agoReleasing 1.1pre1. release-1.1pre1
Guus Sliepen [Sat, 25 Jun 2011 13:28:54 +0000 (15:28 +0200)]
Releasing 1.1pre1.

13 years agoEnsure that the texinfo manual can be converted to HTML.
Guus Sliepen [Sat, 25 Jun 2011 13:28:13 +0000 (15:28 +0200)]
Ensure that the texinfo manual can be converted to HTML.

Somehow commit 2c30af6c90926340a89748c63cc453b1c0b5a589 was not properly
merged.

13 years agoUpdate manpages and info manual.
Guus Sliepen [Sat, 25 Jun 2011 12:52:47 +0000 (14:52 +0200)]
Update manpages and info manual.

13 years agoAdd Makefile.am in gui/.
Guus Sliepen [Fri, 24 Jun 2011 22:32:45 +0000 (00:32 +0200)]
Add Makefile.am in gui/.

This ensures the gui source will be included in the tarball with make dist,
and will be installed with make install.

13 years agoDon't use AM_CONDITIONAL for CURSES.
Guus Sliepen [Fri, 24 Jun 2011 22:06:06 +0000 (00:06 +0200)]
Don't use AM_CONDITIONAL for CURSES.

For some reason, this doesn't work when cross-compiling for Windows.

13 years agoDon't call event_del() from the mtuevent handler, always send_mtu_probe() in ans_key_h().
Guus Sliepen [Fri, 24 Jun 2011 20:49:18 +0000 (22:49 +0200)]
Don't call event_del() from the mtuevent handler, always send_mtu_probe() in ans_key_h().

13 years agoDelete mtuevent if it is not used.
Guus Sliepen [Fri, 24 Jun 2011 20:10:03 +0000 (22:10 +0200)]
Delete mtuevent if it is not used.

Keeping it around prevents ans_key_h() from restarting PMTU discovery.

13 years agoMerge branch 'master' of git://tinc-vpn.org/tinc into 1.1
Guus Sliepen [Fri, 24 Jun 2011 19:40:55 +0000 (21:40 +0200)]
Merge branch 'master' of git://tinc-vpn.org/tinc into 1.1

Conflicts:
NEWS
README
configure.in
src/Makefile.am

13 years agoReleasing 1.0.15. release-1.0.15
Guus Sliepen [Fri, 24 Jun 2011 12:50:20 +0000 (14:50 +0200)]
Releasing 1.0.15.

13 years agoRemove redundant @CFLAGS@ from AM_CFLAGS.
Guus Sliepen [Fri, 24 Jun 2011 10:27:04 +0000 (12:27 +0200)]
Remove redundant @CFLAGS@ from AM_CFLAGS.

13 years agoNo need to check for pselect() in tinc 1.1.
Guus Sliepen [Tue, 21 Jun 2011 21:08:05 +0000 (23:08 +0200)]
No need to check for pselect() in tinc 1.1.

13 years agoOnly log UDP address changes at the appropriate debug levels.
Guus Sliepen [Tue, 21 Jun 2011 21:06:53 +0000 (23:06 +0200)]
Only log UDP address changes at the appropriate debug levels.

13 years agoReopen log file after SIGHUP.
Guus Sliepen [Mon, 6 Jun 2011 19:19:30 +0000 (21:19 +0200)]
Reopen log file after SIGHUP.

This was missed by the previous merge.

13 years agoMerge branch 'master' of git://tinc-vpn.org/tinc into 1.1
Guus Sliepen [Mon, 6 Jun 2011 18:42:15 +0000 (20:42 +0200)]
Merge branch 'master' of git://tinc-vpn.org/tinc into 1.1

Conflicts:
NEWS
configure.in
doc/tincd.8.in
lib/pidfile.c
lib/pidfile.h
lib/xalloc.h
lib/xmalloc.c
src/conf.c
src/conf.h
src/connection.c
src/connection.h
src/event.c
src/graph.c
src/graph.h
src/net.c
src/net.h
src/node.h
src/openssl/crypto.c
src/process.c
src/protocol.c
src/protocol_key.c
src/route.c

13 years agoClean up digests when freeing a connection_t.
Guus Sliepen [Mon, 6 Jun 2011 18:12:33 +0000 (20:12 +0200)]
Clean up digests when freeing a connection_t.

13 years agoImproved --logfile option.
Guus Sliepen [Mon, 6 Jun 2011 14:26:11 +0000 (16:26 +0200)]
Improved --logfile option.

Instead of UNIX time, the log messages now start with the time in RFC3339
format, which human-readable and still easy for the computer to parse and sort.
The HUP signal will also cause the log file to be closed and reopened, which is
useful when log rotation is used. If there is an error while opening the log
file, this is logged to stderr.

13 years agoAttribution for Loïc Grenié.
Guus Sliepen [Sat, 4 Jun 2011 09:27:54 +0000 (11:27 +0200)]
Attribution for Loïc Grenié.

13 years agoNearly tickless tinc.
Loïc Grenié [Sat, 4 Jun 2011 07:05:23 +0000 (09:05 +0200)]
Nearly tickless tinc.

Use pselect instead of select in main_loop (if available). This lets
tincd sleeps as long as there is nothing to do.

13 years agoDon't ignore SIGCHLD, system() needs it.
Guus Sliepen [Fri, 3 Jun 2011 13:50:20 +0000 (15:50 +0200)]
Don't ignore SIGCHLD, system() needs it.

But we do ignore SIGPIPE, and tinc 1.0.x signals that are no longer used
(SIGUSR1 and SIGUSR2), since the default handler of these signals is to
terminate tincd immediately.

13 years agoFix format strings for Windows.
Guus Sliepen [Thu, 2 Jun 2011 22:46:56 +0000 (00:46 +0200)]
Fix format strings for Windows.

Windows doesn't like %zd, so cast (s)size_t to int. Also, some shorts were
incorrectly printed with %d instead of %hd.

13 years agoUse send() when writing to sockets, and the return type is ssize_t.
Guus Sliepen [Thu, 2 Jun 2011 22:34:30 +0000 (00:34 +0200)]
Use send() when writing to sockets, and the return type is ssize_t.

13 years agoSmall fixes for Windows.
Guus Sliepen [Thu, 2 Jun 2011 21:40:27 +0000 (23:40 +0200)]
Small fixes for Windows.

13 years agoEven simpler signal handling.
Guus Sliepen [Thu, 2 Jun 2011 20:14:53 +0000 (22:14 +0200)]
Even simpler signal handling.

13 years agoRemove debugging message that was accidentily left in.
Guus Sliepen [Thu, 2 Jun 2011 19:29:11 +0000 (21:29 +0200)]
Remove debugging message that was accidentily left in.

13 years agoDon't treat packets coming in via TCP as having zero length.
Guus Sliepen [Thu, 2 Jun 2011 19:16:57 +0000 (21:16 +0200)]
Don't treat packets coming in via TCP as having zero length.

13 years agoFix nodes joining the VPN after tincctl top started.
Guus Sliepen [Thu, 2 Jun 2011 19:14:50 +0000 (21:14 +0200)]
Fix nodes joining the VPN after tincctl top started.

13 years agoMake traffic statistics more readable with configurable scaling.
Guus Sliepen [Thu, 2 Jun 2011 18:48:18 +0000 (20:48 +0200)]
Make traffic statistics more readable with configurable scaling.

13 years agoMore stable sorting in tincctl top.
Guus Sliepen [Thu, 2 Jun 2011 18:27:16 +0000 (20:27 +0200)]
More stable sorting in tincctl top.

Although we use qsort(), which is not guaranteed to be stable, resorting the
previously sorted array is more stable than recreating and resorting the array
each time.

13 years agoFix some compiler and cppcheck warnings.
Guus Sliepen [Thu, 2 Jun 2011 16:22:26 +0000 (18:22 +0200)]
Fix some compiler and cppcheck warnings.

13 years agoRemove support for the Ethertap device.
Guus Sliepen [Thu, 2 Jun 2011 16:07:50 +0000 (18:07 +0200)]
Remove support for the Ethertap device.

13 years agoRemove unused functions and variables.
Guus Sliepen [Thu, 2 Jun 2011 15:57:53 +0000 (17:57 +0200)]
Remove unused functions and variables.

13 years agoDon't #include <alloca.h> anymore.
Guus Sliepen [Thu, 2 Jun 2011 15:55:29 +0000 (17:55 +0200)]
Don't #include <alloca.h> anymore.

13 years agoDrop the GNU memcmp.c implementation.
Guus Sliepen [Thu, 2 Jun 2011 15:53:35 +0000 (17:53 +0200)]
Drop the GNU memcmp.c implementation.

13 years agoDrop the GNU malloc.c, realloc.c, and xmalloc.c.
Guus Sliepen [Thu, 2 Jun 2011 15:45:06 +0000 (17:45 +0200)]
Drop the GNU malloc.c, realloc.c, and xmalloc.c.

We live in the 21st century, and we require C99 semantics, so we do not need to
work around buggy libcs. The xmalloc() and related functions are now static
inline functions.

13 years agoSimplify signal handling.
Guus Sliepen [Thu, 2 Jun 2011 15:14:30 +0000 (17:14 +0200)]
Simplify signal handling.

We don't override any signal handlers anymore except those for SIGPIPE and
SIGCHLD. Fatal signals (SIGSEGV, SIGBUS etc.) will terminate tincd and
optionally dump core.  The previous behaviour was to terminate gracefully and
try to restart, but that usually failed and made any core dump useless.

13 years agoRemove outgoing event in free_connection().
Guus Sliepen [Sun, 29 May 2011 20:34:19 +0000 (22:34 +0200)]
Remove outgoing event in free_connection().

13 years agoInitialise priority field to zero for packets read from the VPN interface.
Guus Sliepen [Sun, 29 May 2011 20:14:35 +0000 (22:14 +0200)]
Initialise priority field to zero for packets read from the VPN interface.

13 years agoCosmetic fix when pressing 's' in tincctl top.
Guus Sliepen [Sun, 29 May 2011 20:12:37 +0000 (22:12 +0200)]
Cosmetic fix when pressing 's' in tincctl top.

13 years agoShow hostname and port in error message when connecting to a running tincd.
Guus Sliepen [Sun, 29 May 2011 20:10:54 +0000 (22:10 +0200)]
Show hostname and port in error message when connecting to a running tincd.

13 years agodo_outgoing_connection() may delete a failed connection, and the structure
Sven-Haegar Koch [Sun, 29 May 2011 19:53:21 +0000 (21:53 +0200)]
do_outgoing_connection() may delete a failed connection, and the structure
must not be accessed afterwards.

13 years agosrc/net_socket.c bind_to_address(): Use after free in error path.
Sven-Haegar Koch [Sun, 29 May 2011 19:35:31 +0000 (21:35 +0200)]
src/net_socket.c bind_to_address(): Use after free in error path.

13 years agoAllow tincctl to connect to something besides localhost.
Guus Sliepen [Sun, 29 May 2011 12:41:05 +0000 (14:41 +0200)]
Allow tincctl to connect to something besides localhost.

This would allow tincctl to connect to a remote tincd, or to a local tincd that
isn't listening on localhost, for example if it is using the BindToInterface or
BindToAddress options.

13 years agoRemove a few unnecessary #includes.
Guus Sliepen [Sat, 28 May 2011 21:46:56 +0000 (23:46 +0200)]
Remove a few unnecessary #includes.

Some spotted by Michael Tokarev.

13 years agoRemove newlines from log messages.
Guus Sliepen [Sat, 28 May 2011 21:42:18 +0000 (23:42 +0200)]
Remove newlines from log messages.

13 years agoFix sparse warnings and add an extra sprinkling of const.
Guus Sliepen [Sat, 28 May 2011 21:36:52 +0000 (23:36 +0200)]
Fix sparse warnings and add an extra sprinkling of const.

This is more or less the equivalent of Sven-Haegar Koch's fixes in the 1.1
branch.

13 years agofgets() returns NULL on error, not < 0
Sven-Haegar Koch [Sat, 28 May 2011 01:48:07 +0000 (03:48 +0200)]
fgets() returns NULL on error, not < 0

13 years agosparse fixup: warning: Using plain integer as NULL pointer
Sven-Haegar Koch [Sat, 28 May 2011 01:46:39 +0000 (03:46 +0200)]
sparse fixup: warning: Using plain integer as NULL pointer

13 years agosparse fixup: warning: non-ANSI function declaration of function '...'
Sven-Haegar Koch [Sat, 28 May 2011 01:57:20 +0000 (03:57 +0200)]
sparse fixup: warning: non-ANSI function declaration of function '...'

13 years agosparse fixup: warning: symbol '...' was not declared. Should it be static?
Sven-Haegar Koch [Sat, 28 May 2011 01:56:06 +0000 (03:56 +0200)]
sparse fixup: warning: symbol '...' was not declared. Should it be static?

13 years agosparse fixup: error: too many arguments for function send_key_changed
Sven-Haegar Koch [Sat, 28 May 2011 01:12:03 +0000 (03:12 +0200)]
sparse fixup: error: too many arguments for function send_key_changed

13 years agosparse fixup: error: dubious one-bit signed bitfield
Sven-Haegar Koch [Sat, 28 May 2011 01:08:31 +0000 (03:08 +0200)]
sparse fixup: error: dubious one-bit signed bitfield

13 years agoUse same definition for xalloc_fail_func as is really used.
Sven-Haegar Koch [Sat, 28 May 2011 00:57:40 +0000 (02:57 +0200)]
Use same definition for xalloc_fail_func as is really used.

13 years agoRemoved two newlines from the end of log messages which created empty lines.
Sven-Haegar Koch [Fri, 27 May 2011 23:36:10 +0000 (01:36 +0200)]
Removed two newlines from the end of log messages which created empty lines.

13 years agoFixed error logging on "Input buffer full" condition.
Sven-Haegar Koch [Fri, 27 May 2011 23:33:45 +0000 (01:33 +0200)]
Fixed error logging on "Input buffer full" condition.

13 years agoMake return value of SetPriorityClass() behave the same as setpriority().
Guus Sliepen [Sun, 22 May 2011 13:56:04 +0000 (15:56 +0200)]
Make return value of SetPriorityClass() behave the same as setpriority().

13 years agoAdd the ability to dump all traffic going through route() over a control connection.
Guus Sliepen [Sun, 22 May 2011 12:17:30 +0000 (14:17 +0200)]
Add the ability to dump all traffic going through route() over a control connection.

One can get the packet stream in pcap format, which can be decoded using
tcpdump, for example:

tincctl -n <netname> pcap | tcpdump -r -

13 years agoReset tcplen after use.
Guus Sliepen [Sun, 22 May 2011 12:02:27 +0000 (14:02 +0200)]
Reset tcplen after use.

13 years agoCheck if an event is initialized before calling event_del().
Guus Sliepen [Sun, 22 May 2011 11:15:27 +0000 (13:15 +0200)]
Check if an event is initialized before calling event_del().

Libevent prints a warning to stderr if we do that.

13 years agoAlways compact the buffer if it has reached MAXBUFSIZE.
Guus Sliepen [Sun, 22 May 2011 11:15:05 +0000 (13:15 +0200)]
Always compact the buffer if it has reached MAXBUFSIZE.

13 years agoCompact input buffer before trying to read instead of after.
Guus Sliepen [Sun, 22 May 2011 10:56:51 +0000 (12:56 +0200)]
Compact input buffer before trying to read instead of after.

Also log an error when the input buffer contains more than MAXBUFSIZE bytes
already, instead of silently claiming the other side closed the connection.

13 years agoFix some compiler warnings.
Guus Sliepen [Tue, 17 May 2011 08:58:22 +0000 (10:58 +0200)]
Fix some compiler warnings.

13 years agoUse GetItemCount() on ListCtrls instead of directly accessing ItemCount.
Guus Sliepen [Tue, 17 May 2011 08:57:30 +0000 (10:57 +0200)]
Use GetItemCount() on ListCtrls instead of directly accessing ItemCount.

13 years agoAdd top.h.
Guus Sliepen [Mon, 16 May 2011 07:48:19 +0000 (09:48 +0200)]
Add top.h.

13 years agoAdd tincctl.h.
Guus Sliepen [Mon, 16 May 2011 07:46:54 +0000 (09:46 +0200)]
Add tincctl.h.

13 years agoNicer top command.
Guus Sliepen [Sun, 15 May 2011 14:30:13 +0000 (16:30 +0200)]
Nicer top command.

- Configurable refresh interval.
- Switch between cumulative count or current rate.
- Configurable sorting.

13 years agoAllow inserting items in the middle of a list.
Guus Sliepen [Sun, 15 May 2011 14:29:54 +0000 (16:29 +0200)]
Allow inserting items in the middle of a list.

13 years agoAdd a very primitive "top" command to tincctl.
Guus Sliepen [Sun, 15 May 2011 11:16:48 +0000 (13:16 +0200)]
Add a very primitive "top" command to tincctl.

13 years agoAdd an autoconf check for the curses library.
Guus Sliepen [Sun, 15 May 2011 10:06:21 +0000 (12:06 +0200)]
Add an autoconf check for the curses library.