1 /* vi: set sw=4 ts=4: */
5 * Copyright (C) 2008 by Vladimir Dronnikov <dronnikov@gmail.com>
7 * Licensed under GPLv2, see file LICENSE in this source tree.
11 * A typical usage of BB lpd looks as follows:
12 * # tcpsvd -E 0 515 lpd [SPOOLDIR] [HELPER-PROG [ARGS...]]
14 * This starts TCP listener on port 515 (default for LP protocol).
15 * When a client connection is made (via lpr) lpd first changes its
16 * working directory to SPOOLDIR (current dir is the default).
18 * SPOOLDIR is the spool directory which contains printing queues
19 * and should have the following structure:
26 * <queueX> can be of two types:
27 * A. a printer character device, an ordinary file or a link to such;
30 * In case A lpd just dumps the data it receives from client (lpr) to the
31 * end of queue file/device. This is non-spooling mode.
33 * In case B lpd enters spooling mode. It reliably saves client data along
34 * with control info in two unique files under the queue directory. These
35 * files are named dfAXXXHHHH and cfAXXXHHHH, where XXX is the job number
36 * and HHHH is the client hostname. Unless a printing helper application
37 * is specified lpd is done at this point.
39 * NB: file names are produced by peer! They actually may be anything at all.
40 * lpd only sanitizes them (by removing most non-alphanumerics).
42 * If HELPER-PROG (with optional arguments) is specified then lpd continues
43 * to process client data:
44 * 1. it reads and parses control file (cfA...). The parse process
45 * results in setting environment variables whose values were passed
46 * in control file; when parsing is complete, lpd deletes control file.
47 * 2. it spawns specified helper application. It is then
48 * the helper application who is responsible for both actual printing
49 * and deleting of processed data file.
51 * A good lpr passes control files which when parsed provides the following
53 * $H = host which issues the job
54 * $P = user who prints
55 * $C = class of printing (what is printed on banner page)
56 * $J = the name of the job
57 * $L = print banner page
58 * $M = the user to whom a mail should be sent if a problem occurs
60 * We specifically filter out and NOT provide:
61 * $l = name of datafile ("dfAxxx") - file whose content are to be printed
63 * lpd provides $DATAFILE instead - the ACTUAL name
64 * of the datafile under which it was saved.
65 * $l would be not reliable (you would be at mercy of remote peer).
67 * Thus, a typical helper can be something like this:
69 * cat ./"$DATAFILE" >/dev/lp0
70 * mv -f ./"$DATAFILE" save/
73 //usage:#define lpd_trivial_usage
74 //usage: "SPOOLDIR [HELPER [ARGS]]"
75 //usage:#define lpd_full_usage "\n\n"
76 //usage: "SPOOLDIR must contain (symlinks to) device nodes or directories"
77 //usage: "\nwith names matching print queue names. In the first case, jobs are"
78 //usage: "\nsent directly to the device. Otherwise each job is stored in queue"
79 //usage: "\ndirectory and HELPER program is called. Name of file to print"
80 //usage: "\nis passed in $DATAFILE variable."
82 //usage: "\n tcpsvd -E 0 515 softlimit -m 999999 lpd /var/spool ./print"
86 // strip argument of bad chars
87 static char *sane(char *str
)
92 if (isalnum(*s
) || '-' == *s
|| '_' == *s
) {
101 static char *xmalloc_read_stdin(void)
104 size_t max
= 4 * 1024; // more than enough for commands!
105 return xmalloc_reads(STDIN_FILENO
, &max
);
108 int lpd_main(int argc
, char *argv
[]) MAIN_EXTERNALLY_VISIBLE
;
109 int lpd_main(int argc UNUSED_PARAM
, char *argv
[])
111 int spooling
= spooling
; // for compiler
115 // goto spool directory
119 // error messages of xfuncs will be sent over network
120 xdup2(STDOUT_FILENO
, STDERR_FILENO
);
122 // nullify ctrl/data filenames
123 memset(filenames
, 0, sizeof(filenames
));
126 s
= queue
= xmalloc_read_stdin();
127 // we understand only "receive job" command
130 printf("Command %02x %s\n",
131 (unsigned char)s
[0], "is not supported");
135 // parse command: "2 | QUEUE_NAME | '\n'"
137 // protect against "/../" attacks
138 // *strchrnul(queue, '\n') = '\0'; - redundant, sane() will do
142 // queue is a directory -> chdir to it and enter spooling mode
143 spooling
= chdir(queue
) + 1; // 0: cannot chdir, 1: done
144 // we don't free(s), we might need "queue" var later
149 // int is easier than ssize_t: can use xatoi_positive,
150 // and can correctly display error returns (-1)
151 int expected_len
, real_len
;
154 safe_write(STDOUT_FILENO
, "", 1);
157 // valid s must be of form: "SUBCMD | LEN | space | FNAME"
158 // N.B. we bail out on any error
159 s
= xmalloc_read_stdin();
160 if (!s
) { // (probably) EOF
163 // non-spooling mode or no spool helper specified
164 if (!spooling
|| !*argv
)
165 return EXIT_SUCCESS
; // the only non-error exit
166 // spooling mode but we didn't see both ctrlfile & datafile
168 goto err_exit
; // reject job
170 // spooling mode and spool helper specified -> exec spool helper
171 // (we exit 127 if helper cannot be executed)
173 // read and delete ctrlfile
174 q
= xmalloc_xopen_read_close(filenames
[0], NULL
);
175 unlink(filenames
[0]);
176 // provide datafile name
177 // we can use leaky setenv since we are about to exec or exit
178 xsetenv("DATAFILE", filenames
[1]);
179 // parse control file by "\n"
180 while ((p
= strchr(q
, '\n')) != NULL
&& isalpha(*q
)) {
182 // q is a line of <SYM><VALUE>,
183 // we are setting environment string <SYM>=<VALUE>.
184 // Ignoring "l<datafile>", exporting others:
191 // helper should not talk over network.
192 // this call reopens stdio fds to "/dev/null"
193 // (no daemonization is done)
194 bb_daemonize_or_rexec(DAEMON_DEVNULL_STDIO
| DAEMON_ONLY_SANITIZE
, NULL
);
195 BB_EXECVP_or_die(argv
);
199 // we understand only "control file" or "data file" cmds
200 if (2 != s
[0] && 3 != s
[0])
201 goto unsupported_cmd
;
202 if (spooling
& (1 << (s
[0]-1))) {
203 printf("Duplicated subcommand\n");
207 *strchrnul(s
, '\n') = '\0';
208 fname
= strchr(s
, ' ');
211 printf("No or bad filename\n");
215 // // s[0]==2: ctrlfile, must start with 'c'
216 // // s[0]==3: datafile, must start with 'd'
217 // if (fname[0] != s[0] + ('c'-2))
220 expected_len
= bb_strtou(s
+ 1, NULL
, 10);
221 if (errno
|| expected_len
< 0) {
222 printf("Bad length\n");
225 if (2 == s
[0] && expected_len
> 16 * 1024) {
227 // ctrlfile can't be big (we want to read it back later!)
228 printf("File is too big\n");
234 // spooling mode: dump both files
235 // job in flight has mode 0200 "only writable"
237 fd
= open3_or_warn(fname
, O_CREAT
| O_WRONLY
| O_TRUNC
| O_EXCL
, 0200);
240 filenames
[s
[0] - 2] = xstrdup(fname
);
242 // non-spooling mode:
243 // 2: control file (ignoring), 3: data file
246 fd
= xopen(queue
, O_RDWR
| O_APPEND
);
250 safe_write(STDOUT_FILENO
, "", 1);
253 real_len
= bb_copyfd_size(STDIN_FILENO
, fd
, expected_len
);
254 if (real_len
!= expected_len
) {
255 printf("Expected %d but got %d bytes\n",
256 expected_len
, real_len
);
259 // get EOF indicator, see whether it is NUL (ok)
260 // (and don't trash s[0]!)
261 if (safe_read(STDIN_FILENO
, &s
[1], 1) != 1 || s
[1] != 0) {
262 // don't send error msg to peer - it obviously
263 // doesn't follow the protocol, so probably
264 // it can't understand us either
269 // chmod completely downloaded file as "readable+writable"
271 // accumulate dump state
272 // N.B. after all files are dumped spooling should be 1+2+4==7
273 spooling
|= (1 << (s
[0]-1)); // bit 1: ctrlfile; bit 2: datafile
277 close(fd
); // NB: can do close(-1). Who cares?
279 // NB: don't do "signal OK" write here, it will be done
280 // at the top of the loop
284 // don't keep corrupted files
287 for (i
= 2; --i
>= 0; )
289 unlink(filenames
[i
]);