CVS log for src/libexec/ftpd/conf.c

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Default branch: MAIN

Pull up following revision(s) (requested by lukem in ticket #1905):

	libexec/ftpd/conf.c: revision 1.65

Fix uninitialized memory usage in count_users()

If the file was previously empty, pids table is not set, the code however used
pids[0] which is uninitialized in this case. In some scenarios it may lead to
propagate garbage value from pids[0] to the file and cause writing outside of
allocated memory.

OK lukem@

Pull up following revision(s) (requested by lukem in ticket #1741):

	libexec/ftpd/conf.c: revision 1.65

Fix uninitialized memory usage in count_users()

If the file was previously empty, pids table is not set, the code however used
pids[0] which is uninitialized in this case. In some scenarios it may lead to
propagate garbage value from pids[0] to the file and cause writing outside of
allocated memory.

OK lukem@

Pull up following revision(s) (requested by lukem in ticket #388):

	libexec/ftpd/conf.c: revision 1.65

Fix uninitialized memory usage in count_users()

If the file was previously empty, pids table is not set, the code however used
pids[0] which is uninitialized in this case. In some scenarios it may lead to
propagate garbage value from pids[0] to the file and cause writing outside of
allocated memory.

OK lukem@

Fix uninitialized memory usage in count_users()

If the file was previously empty, pids table is not set, the code however used
pids[0] which is uninitialized in this case. In some scenarios it may lead to
propagate garbage value from pids[0] to the file and cause writing outside of
allocated memory.

OK lukem@

sync with (a bit old) head

Resync to 2012-11-19 00:00:00 UTC

include pwd.h for password stuff

remove gcc-4.5 hack

Sync with HEAD.

Third (and last) commit. See http://mail-index.netbsd.org/source-changes/2009/05/13/msg221222.html

Fix WARNS=4 issues (const & sign mismatches, etc)
Ensure various ftpd.conf values can't exceed their underlying types.

Sync w/ -current. 34 merge conflicts to follow.

sync with head.

Don't use non-standard "u_<foo>" types.
Strip trailing whitespace (as well as ':'s) off PAM password prompts.
Improve some debug logging related to PAM.

sync with head.

Remove clause 3 and 4 from TNF licenses

sync with head.

sync with HEAD

Switch from lockf() to (more portable) fcntl() locking

fix volatile and initialization issues, from Anon Ymous

debug -> ftpd_debug
xstrdup -> ftpd_strdup

Fix comment about DEFAULT_UMASK.
Pointed out in private mail by Tetsuya Isaki and Dmitry Sivachenko.

* Add recvbufsize configuration option
  This allows for setting the passive socket's SO_RCVBUF.  Option works
  similarly to the current sendbufsize configuration option.
* Change how recveive_data() works
  When reading data from the socket for passive transfers to the server,
  receive_data() now works very similar to send_data_with_read().  Reads
  from the network are now done using either the filesystem block size or
  the configuration option readsize chunks.
* Crank version.h
  [Changes discussed with lukem.]

* Add hidesymlinks configuration option
  This adds a -L to all ls command arguments so that the file or directory
  the link references is listed rather than the link itself.  This was
  inspired by IRIX ftpd's -S option.
  [Discussed with lukem some time ago.]
* Crank version.h [right Luke? :-)]

change _PATH_FOO to _NAME_FOO where FOO is not a path. I'll discuss with
luke what is the best way to fix this.

Pullup rev 1.47-1.52 (requested by he in ticket #1739)

Update to NetBSD ftpd 20040809.  Fixes SA#2004-009.

Pullup rev 1.41-1.52 (requested by he in ticket #158)

Update to NetBSD ftpd 20040809.  Fixes SA#2004-009.

Pullup rev 1.52 (requested by lukem in ticket #757)

* Fix yacc parser error recovery so that setjmp(3)/longjmp(3) is unnecessary.
* Fix SIGURG handler to set an urgflag that's later tested, rather than
  abusing setjmp(3)/longjmp(3).
* Use "volatile sig_atomic_t" as the type of variables modified by sig handlers.
* Use sigaction(3) instead of signal(3) to set the signal handlers.
* Only set the main SIGALRM handler once.  If we need to change it,
  cache the old handler and restore appropriately...
* Remove a bunch of signal races by improving the signal handlers.
* Fix memory leak with 'ESPV ALL'.
* Clean up the debug message in reply(); use vsnprintf(3) instead of vsyslog(3).
* Rework parsing of OOB commands to _not_ use the yacc parser, since the
  latter isn't reentrant and the hacks to work around that are ugly.
  We now examine urgflag at appropriate locations and call handleoobcmd()
  if it's set.  Since the only OOB commands we currently implement are
  ABOR and STAT, this isn't an issue.

Fixes from (or inspired by) OpenBSD:
* Fix yacc parser error recovery so that setjmp(3)/longjmp(3) is unnecessary.
* Fix SIGURG handler to set an urgflag that's later tested, rather than
  abusing setjmp(3)/longjmp(3).
* Use "volatile sig_atomic_t" as the type of variables modified by sig handlers.
* Use sigaction(3) instead of signal(3) to set the signal handlers.
* Only set the main SIGALRM handler once.  If we need to change it,
  cache the old handler and restore appropriately...
* Remove a bunch of signal races by improving the signal handlers.
* Fix memory leak with 'ESPV ALL'.

My stuff:
* Clean up the debug message in reply(); use vsnprintf(3) instead of vsyslog(3).
* Rework parsing of OOB commands to _not_ use the yacc parser, since the
  latter isn't reentrant and the hacks to work around that are ugly.
  We now examine urgflag at appropriate locations and call handleoobcmd()
  if it's set.  Since the only OOB commands we currently implement are
  ABOR and STAT, this isn't an issue.  (I also can't find the reference in
  RFC2228 where MIC, CONF & ENC are OOB-only commands.  Go figure.)
  I could clean up the is_oob stuff some more, but the remaining stuff
  in ftpcmd.y is harmless and it's unnecessary churn right this moment.

- convert to using libc's strsuftoll(3)
- use LLT (aka 'long long type') for all numeric class parameters
- improve description of various ftpd.conf(5) options
- statcmd(): print out:  mmapsize readsize writesize sendbufsize sendlowat

audit use of strto* - beware of ERANGE, as well as typecast on result.

Enable GLOB_BRACE for ftpd.conf(5)'s `notify' directive.
Now it's much easier to list multiple files...

Added CONF_LL macro, which understands raw 'strsuftoll' conf variables.

Add optional mmap(2)/write(2) support for binary file transfer.
The default is read(2)/write(2).  Note that the sosend_loan needs
some more work for better performance when a file isn't cached.

Add two new ftpd.conf(5) directives:
- 'denyquick'; deny a connection so tagged by ftpusers(5) after the USER
  command instead of the PASS command. whilst this might provide some
  info leakage of accounts names if you have some `real' or `chroot'
  users enabled and not others, it does prevent accidental entering of
  such passwords if you have all such users denied. This option is
  strongly recommended on anonymous-only servers.
  Functionality requested by Rob Windsor in [bin/12602]
- 'private'; don't display class related information in the output of STAT.
  For paranoid admins.

- enable case insensitive fnmatch(3)ing for hostname globs in ftpusers(5)
- enable WARNS=2

a few changes from Mike Heffner <mheffner@vt.edu> in private email:
- totally clear a glob buffer before use, because FreeBSD depends on
  some of the other fields being cleared (other than just gl_offs)
- in strend(), ensure that the source string isn't too large
- remove unnecessarily complicated sizing of proctitle, since snprintf()
  will truncate it anyway

s/tise/tize/ in docco, add "advertize" as synonym for "advertise"

Initialize a pointer needed when expanding the %C "display file escape
sequence".

crank copyrights of files changed this year
remove superfluous byte_count update in send_file_list
crank version

Pull up revision 1.39 (requested by christos):
  Fixes buffer overflow problems in glob(3).  Adds and uses GLOB_LIMIT
  to prevent denial of service attacks.

sync ftpd to -current with the following revisions (for lukem/christos):
	Makefile	1.43-1.44
	cmds.c		1.7-1.8,  1.10-1.12
	conf.c		1.35-1.40
	extern.h	1.32-1.38
	ftpcmd.y	1.53-1.59
	ftpd.8		1.58-1.63
	ftpd.c		1.102-1.104,  1.106-1.122
	ftpd.conf.5	1.12-1.15
	ftpusers.5	1.8
	logwtmp.c	1.16
	popen.c		1.23-1.25
	version.h	1.28

a quick summary of user-visible changes;
	- fix glob DoS by using GLOB_LIMIT
	- add ftpd.conf directives `advertise', `maxfilesize', `sanenames'
	- add flags: -P dataport, -X - wuftpd style log entries,
	  -q/-Q - (en|dis)able pidfiles, -u/-U - (en|dis)able utmp,
	  -w/-W - (en|dis)able wtmp

don't leak globbed memory.

Use GLOB_LIMIT. Also fix a bug where gl_offs was not initialized and could
contain trash.

don't support t(erabyte) as a suffix in strsuftoll() #ifdef NO_LONG_LONG

Features:

* Add ftpd.conf(5) directive `advertise'; change the address that is
  advertised to the client for PASV transfers. this may be useful in
  certain firewall/NAT environments.

  Feature requested in [bin/9606] by Scott Presnell.

* Add -X option; syslog wu-ftpd style xferlog messages, prefixed with
  `xferlog: '.  An example line from syslog (wrapped):
	Dec 16 18:50:24 odysseus ftpd[571]: xferlog: Sat Dec 16 18:50:24 2000
	2 localhost 3747328 /pub/WLW2K601.EXE b _ o a lukem@ FTP 0 * c

  These messages can be converted to a wu-ftpd style xferlog file
  suitable for parsing with third-party tools with something like:
	grep 'xferlog: ' /var/log/xferlog | \
	    sed -e 's/^.*xferlog: //' >wuxferlog

  The format is the same as the wu-ftpd xferlog entries (with the leading
  syslog stuff), but different from the wu-ftpd syslogged xferlog entries
  because the latter is not as easy to convert into the standard xferlog
  file format.

  The choice to only syslog the xferlog messages rather than append to
  a /var/log/xferlog file was made because the latter doesn't work to
  well in the situation where the logfile is rotated and compressed and
  a long-running ftpd still has a file-descriptor to the now nonexistant
  xferlog file, and the log message will then get lost.

  Feature requested in [bin/11651] by Hubert Feyrer.


Fixes:

* In ftpd(8), clarify the -a and -c options.

* More clarifications in ftpd.conf(5).

* Ensure that all ftpd.conf commands set a parameter back to sane defaults
  if an argument of `none' or bad settings are given.

* Support the `chroot' directive for `REAL' users too (for consistency).

* For `GUEST' users, store the supplied password in pw->pw_passwd for use
  later in the xferlog.

* If show_chdir_messages() is given a code of -1, flush the cache of
  visited directories.  Invoke show_chdir_messages(-1) in end_login().

* Only syslog session stats if logging is requested.

* Rename logcmd() -> logxfer(), and dolog() -> logremotehost().

* Use cprintf() instead of fprintf() where appropriate.

* Minor KNF, and make a couple of functions static that were declared static.

- new ftpd.conf directives:
	maxfilesize	set the maximum size of uploaded files
	sanenames	if set, only permit uploaded filenames that contain
			characters from the set "-+,._A-Za-z0-9" and that
			don't start with `.'

- new/changed command line options:
	-e emailaddr	define email address for %E (see below)
	-P dataport	use dataport as the dataport (instead of ctrlport-1)
	-q		use pid files to count users	[default]
	-Q		don't use pid files to count users
	-u		write entries to utmp
	-U		don't write entries to utmp	[default]
	-w		write entries to wtmp		[default]
	-W		don't write entries to wtmp

	  NOTE:	-U used to mean `write utmp entries'. Its meaning has changed
		so that it's orthogonal with -q/-Q and -w/-W. This isn't
		considered a major problem, because using -U isn't going to
		enable something you don't want, but will disable something
		you did want (which is safer).

- new display file escape sequences:
	%E	email address
	%s	literal `s' if the previous %M or %N wasn't ``1''.
	%S	literal `S' if the previous %M or %N wasn't ``1''.

- expand the description of building ~ftp/incoming to cover the
  appropriate ftpd.conf(5) directives (which are defaults, but it pays
  to explicitly explain them)

- replace strsuftoi() with strsuftoll(), which returns a long long if
  supported, otherwise a long

- rework the way that check_modify and check_upload are done in the yacc
  parser; they're merged into a common check_write() function which is
  called explicitly

- merge all ftpclass `flag variables' into a single bitfield-based flag element

- move various common bits of parse_conf() into a couple of macros

- clean up some comments

changes to improve portability:
* replace union sockunion {} with struct sockinet {}, and modify the code
  accordingly. this is possibly more portable, as it doesn't rely upon
  the structure alignment within the union for our own stuff.  uses local
  su_len unless HAVE_SOCKADDR_SA_LEN is defined (set ifdef BSD4_4)
  (XXX: haven't tested the ipv6 stuff)
* always use getaddrinfo() and getnameinfo() instead of maintaining two code
  paths. (lukemftpd will provide replacements for these on older systems)
* use lockf() instead of open(.., O_EXLOCK) to lock the pid file
* minor KNF
* clean up long long support: create helper #defines and use as appropriate:
        #define		NO_LONG_LONG	! NO_LONG_LONG
        -------		------------	--------------
        LLF		"%ld"		"%lld"
        LLFP(x)		"%" x "ld"	"%" x "lld"
        LLT		long		long long
        ULLF		"%lu"		"%llu"
        ULLFP(x)	"%" x "lu"	"%" x "llu"
        ULLT		unsigned long	unsigned long long
        STRTOLL(x,y,z)	strtol(x,y,z)	strtoll(x,y,z)

user visible changes (besides checking the cvs log):
* make checkportcmd the default
* add -r; force permanent drop of root privs after login
* add -V vers; change version string to vers
* add -H; act as -h `hostname`
* permanently drop root privs if it makes sense to do so (e.g; logging in as
  guest/chroot user on a port > 1024)
* fix reference to draft-ietf-ftpext-mlst-11
* add ftpd.conf directives: chroot, homedir
* fix base64_encode() and generation of the unique fact
* crank version to 20000723

* make checkportcmd the default. this breaks third-party proxy ftp but
  prevents the ftp bounce attack, and we should be secure out of the
  box, not require users to tweak obscure stuff.
* allow the version string reported to clients to be changed with '-V vers'.
  if vers is empty or `-', don't report a version.
* if -r is given, permanently drop root privs
* if not a REAL user (i.e, GUEST or CHROOT), and ftpd is running on a port
  > IPPORT_RESERVED+1, permanently drop root privs
* don't bother reverting to root privs to logout of wtmp/utmp; since the
  file descriptor is already open this isn't necessary.
* fix the binding of the port for the PORT/LPRT/EPRT connection to be the
  ctrl_addr.su_port-1, not hardcoded to `20' (this was broken in the ipv6
  merge). if root privs have been dropped, and this would be a port <
  IPPORT_RESERVED, use a random port instead (which isn't RFC959 compliant
  but it doesn't appear that many clients care).
* prevent login of a new user if privs have been dropped and already logged
  in as a REAL user (existing check already stops GUEST & CHROOT users).
* move the port check stuff into a separate port_check() function, and use
  for PORT, LPRT, and EPRT checks. inspired by freebsd
* minor KNF
* minor man page cleanup

* add two new ftpd.conf(5) directives:
	chroot	specify dir to chroot to for GUEST and CHROOT users, to
		override -a anondir or the user's homedir.
	homedir	specify dir to change to upon login; also used for ~ expansion
		and $HOME for subprocesses)
  both of these can take % escapes: %u (username), %d (homedir), %c (class).
* fix NLST to take a pathname not a STRING, so that ~ expansion works
* modify CWD to use the homedir parsed from curclass.homedir
* implement format_path(dst, src), to parse src expanding % escapes (see above)
  into dst.
* rename format_file() to display_file()

More -Wformat cleanups.

Sync w/ netbsd-1-5-base.

various fixes suggested by Robert Elz:
* implement closedataconn() and use appropriately (including in mlsd())
* only put leading space in front of MLST output (not MLSD output)
* MLSD: only output pdir and cdir entries when the type fact is requested.
* change error code for giving MLSD a non-directory from 550 to 501
* remove MLSx Type fact support for UNIX.* for now; it's not standardised yet.
* do a check_login when MLSD and MLST are given no args
* detect & complain about null facts in OPTS MLST
* cache getgroups() at login instead of calling each time in fact_perm()

other mods:
* implement cprintf(); as per fprintf() but increments total_bytes{,_out}
* implement CPUTC(); as per putc() but increments total_bytes{,_out}
* implement base64_encode()
* fact_unique() display base64 encoding of dev_t and ino_t rather than
  hex output; should scale if size of those changes
* change reply() so that a negative code acts as the initial line in a reply,
  code == 0 prefixes the line with 4 spaces, and code > 0 works as before.
  deprecate lreply(code, ) and lreply(0, ) in favour of reply(-code, ) and
  reply(0, ) respectively.
* use cprintf() and CPUTC() appropriately (often instead of printf(),
  lreply(-2, ) or lreply(-1, ).
  now we actually account for the data sent by MLST and MLSD.
* remove DEBUG support for sending MLSD output to control connection instead
  of data connection (my ftp client now supports MLSD :-)

convert to ANSI C as per style guide

suppress verbose messages from CWD and post-login if the first
character of the anonymous password is `-'.

* add ftpd.conf directive `portrange class min max', which allows specification
  of the port range used by passive connections. based on work in [bin/9158]
  from Takahiro Kambe <taca@sky.yamashina.kyoto.jp>
* change the way global variables are defined and extern-ed to be more
  consistent.

fix problem where ftpd.conf lines would match everything if there was
no template defined. noted by Vebjorn Ljosa <ljosa@initio.no>

* new ftpd.conf directive:
	template class [refclass]
  following directives for refclass will apply to class as well.
  this makes setting up a `template' class with many default settings
  easy, whilst allowing for class-specific overrides
* prevent crash when the optional limitfile wasn't given to limit
* document count_users()
* document default setting of limit in ftpd.conf(5)
* crank version

features:
* add connection limits (`limit' keyword in ftpd.conf)
* move initialisation of curclass from parse_conf() to new function
  init_curclass()
* implement count_users(), which determines the number of users in a given
  class. a file - /var/run/ftpd.pids-<class> - is used to store a list
  of pids in use (effectively an array of pid_t's), and its size is reduced
  as necessary.
* new % modifiers in format_file:
	%c	class
	%M	maximum connection count
	%N	current connection count
* always end_login()s, even for refused connections

bugs fixed:
* remove \n from %T output
* fix some inconsistencies in the man pages
* ensure that both `ftp' *and* `anonymous' are allowed in ftpusers.
  (this was accidently broken in a recent commit to be ``or'' not ``and'')
* use MAXPATHLEN not MAXPATHLEN+1
* crank copyright date on modified files
* crank version

Pull up to last week's -current.

* change format of /etc/ftpusers lines from
	userglob [allow|deny]
  to
	userglob[@host] [allow|deny  [classname]]
  where class is a userdefined classname.
  - if host is given it may either be a CIDR address (e.g, `1.2.3.0/24') or a
    hostglob (e.g, `*.foo.com'), and the remote host is matched against that.
  - if classname is given, use that to match entries in ftpd.conf (defaults
    to `guest' for `anonymous'/`ftp' logins, `chroot' for users found in
    /etc/ftpchroot, and `real' for everyone else.

* implement new /etc/ftpd.conf directives:
    classtype classname type	set type of classname to GUEST, CHROOT, or REAL
    motd classname file		file to use instead of /etc/motd
    rateget classname rate	set rateget throttle to rate
    rateput classname rate	set rateput throttle to rate
    upload classname		allow/deny uploads (STOU, STOR, APPE). if
				denied, also acts as `modify deny'.

* implement new `SITE' commands:
    RATEGET	as per /etc/ftpd.conf rateget, but cannot exceed that
    RATEPUT	as per /etc/ftpd.conf rateput, but cannot exceed that

* implement format_file(), which outputs a file to the user, parsing %
  escapes. use to print /etc/ftpwelcome, /etc/motd, and the `display' file.

* implement strsuftoi() (from ftp(1)), which parses a number and
  optional suffix (for use with rateget, etc)

* don't bother seteuid(0) ; bind(...) ; seteuid(pw->pw_uid), since
  we don't need reserved ports (at wasn't getting them anyway).

* update & reorder copyrights

* use strlcpy() as appropriate

* change ftpd_popen() to take char *argv[] instead of char *cmd.
  the string tokenisation must be performed by the caller (which is
  generally easy because it's almost always a static command).
* change do_conversion() to return a char *argv[] instead of char *cmd.
  tokenisation of the command is done internally.
* change retrieve() to take char *argv[] instead of char *cmd.
  (to take advantage of the above changes).  fixes [bin/8173]
* use fparseln() instead of fgetln()
* store conversions in listed order (rather than reverse order)
* use stringlists instead of handrolling code to manage an argv.

check return val of sl_init() and sl_add()

more kerberos5 fixes

* fix a problem in retrieve() where arguments to commands weren't working
  (this was broken in the last commit). problem noticed by simonb@
* don't display the stderr output of the internal ls.
* modify usage of lreply so that generally only one `XXX-' code per
  `block' is displayed; the rest of the lines have four spaces instead.
  i find this easier to read.
* fix a couple places where byte accounting wasn't correct

features/fixes:
* implement xferstats. full stats are displayed for `STAT', and a
  summary is displayed upon exit (and syslogged).  inspired by wu-ftpd.
* wrap data xfers in {send,receive}_data with alarm() timeouts. this
  should remove the majority of the `hanging ftpd' problems that
  people were still seeing.  inspired by wu-ftpd.
* link with ../../bin/ls, so that bin/ls is not required under a
  chroot()ed area for `LIST' to work.  based on [bin/4497] from
  "Soren S.  Jorvang" <soren@t.dk>
* migrate code from util.c into ftpd.c, so that it doesn't conflict
  with ls' util.c.
* remove man page comment about ~ftp/bin/ls being necessary.
* bump version to 7.2.0.
* syslog xfer time with xfer stats.
* if appropriate, syslog error message with command.

internal code stuff:
* change arguments of various functions from `char *' to `const char *'.
* define PLURAL(x) macro, which returns `' if x == 1, `s' otherwise.
  use macro appropriately
* lreply(): a code of -1 means ``send line as is''. a code of 0
  means ``send line with 4 space prefix''. don't print a space after
  the `-' for any other code.
* logcmd(): add `const struct timeval *elapsed' and `const char *error'
  for more flexible error reporting

Make this build with KERBEROS5 defined.

* actually commit the changes which add support for recognising RFC 2228
  commands (even if we don't do anything with them)
* in logcmd(), syslog why realpath() failed (if it did).

* replace LOG(CMD|BYTES) macros with logcmd(), which is a cleaner
  solution with less code replication. use realpath() in logcmd() so
  that all logged filenames are sane.
* support `REST STREAM' in `FEAT' reply (from draft-ietf-ftpext-mlst-05)
* in 'HELP', suffix unimplemented commands with `-' instead of `*'; the
  former is easier to differentiate from `+'.
* deprecate curdir() now that logcmd() doesn't use it.
* ensure all filename buffers are at least MAXPATHLEN+1 in size.
* move jmp_buf errcatch out of extern.h, removing need to #include <setjmp.h>
  in every file.

* complete fix for `multiple replies returned for single parse error'
  problem; move `hasyyerrored' state flag out of yylex() so that
  check_{login,modify} can also set it.
* check result of check_login for PORT command
* set initial timeout before the "setjmp(); for(;;) yyparse()",
  otherwise an invalid command after login incorrectly sets the timeout
  to 5 minutes (rather than what was set in ftpd.conf)
* replace (char *)0 with NULL
* move yyerror() from ftpd.c to ftpcmd.y
* remove need for -Dunix, by using the version string from ftpd.c
  (instead of `BSD-199506')
* move all extern-ed vars into extern.h

Add the ability to disable passive connects in ftpd.conf (breaks RFC1123,
STD3, but needed in some firewall environments).

Show/log the strerror(errno) string when getcwd fails

Fix some problems with failed getcwd commands, reported in PR bin/5531
by Saitoh Masanobu <msaitoh@spa.is.uec.ac.jp>.

Need <time.h> for time(), localtime() and ctime() prototypes.

pull up from trunk:  fixes from lukem.

log debug stuff using LOG_DEBUG not LOG_INFO

pull up from trunk:  cleanup and a fix to previous (from lukem).

* change checkportcmd syntax to `checkportcmd class [off]' (as per `modify')
* display current setting of checkportcmd in STAT
* ensure that curclass.checkportcmd is initialised to 0
* document default setting of checkportcmd in ftpd(8)
* cleanup code a bit, putting code for "checkportcmd" in alphabetical order

pull up from trunk:  add a "checkportcmd <class>" option that stops ftp bounce attacks.

add a "checkportcmd <class>" option that stops ftp bounce attacks.

Use S_IS*(), not S_IF*.

implement '-c confdir', which allows the specification of an alternate
directory to look for the various configuration files, overriding /etc.
From Matthias Scheler <tron@lyssa.owl.de> in [bin/4133]

* don't depend upon buffer returned by fgetln() to remain. fix mainly
  from Tatoku Ogaito <tacha@tera.fukui-med.ac.jp> in [bin/3967]
* fgetln() doesn't \0 terminate its string. look for the \n and replace
  it with \0 (if no \n, ignore the line - it's most likely corrupt)
* more intensive checks on strdup() returns (not a current mem leak,
  but depended upon code elsewhere to cleanup - not good)
* cleanup some syslog error messages

Fix files using old TNF copyright notice

missed some warnings.

- Pass gcc -Wall
- Fix incorrect const poisoning
- Fix ftpd_popen to dynamically allocate strings to avoid buffer overruns.

* implement /etc/ftpd.conf, which adds support for the following features,
  controllable on a per class (which is one of: real, chroot, guest,
  all or none) basis:
    * on-the-fly execution of a command to build the file (a ``conversion''),
      providing support for "get dirname.tar" and the like.
    * displaying the contents of a file when a directory is entered
      for the first time.
    * maximum value for timeout (replaces -T).
    * control usage of CHMOD, DELE, MKD, RMD, UMASK; replacing -DINSECURE_GUEST.
    * notifying the user of the existance of a files matching a glob
      pattern when a directory is entered for the first time.
    * default value for timeout (replaces -t).
    * default umask (replaces -DGUEST_CMASK and -u).
  The conversion, display, and notify functionality was based on code by
  Simon Burge <simonb@telstra.com.au>.
* clean up and re-order parts of the man page into subsections.
* STAT displays the settings defined for the class of the current user.
* bump version from 6.00 to 7.00, because of ftpd.conf.
* deprecate -DGUEST_CMASK and -DINSECURE_GUEST in the Makefile, and
  -t, -T and -u, as ftpd.conf allows finer control of these.
* add "nostderr" argument to ftpd_popen(), because you don't want the
  stderr stream mixing with the stdout stream during a conversion,
  as this can corrupt the stream.