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 tarball for details.
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/
75 // strip argument of bad chars
76 static char *sane(char *str)
81 if (isalnum(*s) || '-' == *s || '_' == *s) {
90 // we can use leaky setenv since we are about to exec or exit
91 static void exec_helper(char **filenames, char **argv) ATTRIBUTE_NORETURN;
92 static void exec_helper(char **filenames, char **argv)
99 // read and delete ctrlfile
100 q = xmalloc_open_read_close(filenames[0], NULL);
101 unlink(filenames[0]);
102 // provide datafile name
103 xsetenv("DATAFILE", filenames[1]);
104 // parse control file by "\n"
105 while ((p = strchr(q, '\n')) != NULL
109 // q is a line of <SYM><VALUE>,
110 // we are setting environment string <SYM>=<VALUE>.
111 // Ignoring "l<datafile>", exporting others:
119 // we are the helper, we wanna be silent.
120 // this call reopens stdio fds to "/dev/null"
121 // (no daemonization is done)
122 bb_daemonize_or_rexec(DAEMON_DEVNULL_STDIO | DAEMON_ONLY_SANITIZE, NULL);
123 BB_EXECVP(*argv, argv);
124 exit(127); // it IS error if helper cannot be executed!
127 static char *xmalloc_read_stdin(void)
130 size_t max = 4 * 1024; // more than enough for commands!
131 return xmalloc_reads(STDIN_FILENO, NULL, &max);
134 int lpd_main(int argc, char *argv[]) MAIN_EXTERNALLY_VISIBLE;
135 int lpd_main(int argc ATTRIBUTE_UNUSED, char *argv[])
137 int spooling = spooling; // for compiler
141 // goto spool directory
145 // error messages of xfuncs will be sent over network
146 xdup2(STDOUT_FILENO, STDERR_FILENO);
148 // nullify ctrl/data filenames
149 memset(filenames, 0, sizeof(filenames));
152 s = queue = xmalloc_read_stdin();
153 // we understand only "receive job" command
156 printf("Command %02x %s\n",
157 (unsigned char)s[0], "is not supported");
161 // parse command: "2 | QUEUE_NAME | '\n'"
163 // protect against "/../" attacks
164 // *strchrnul(queue, '\n') = '\0'; - redundant, sane() will do
168 // queue is a directory -> chdir to it and enter spooling mode
169 spooling = chdir(queue) + 1; // 0: cannot chdir, 1: done
170 // we don't free(s), we might need "queue" var later
175 // int is easier than ssize_t: can use xatoi_u,
176 // and can correctly display error returns (-1)
177 int expected_len, real_len;
180 safe_write(STDOUT_FILENO, "", 1);
183 // valid s must be of form: "SUBCMD | LEN | space | FNAME"
184 // N.B. we bail out on any error
185 s = xmalloc_read_stdin();
186 if (!s) { // (probably) EOF
187 if (spooling /* && 7 != spooling - always true */) {
188 // we didn't see both ctrlfile & datafile!
191 // one of only two non-error exits
196 // we understand only "control file" or "data file" cmds
197 if (2 != s[0] && 3 != s[0])
198 goto unsupported_cmd;
199 if (spooling & (1 << (s[0]-1))) {
200 printf("Duplicated subcommand\n");
204 *strchrnul(s, '\n') = '\0';
205 fname = strchr(s, ' ');
208 printf("No or bad filename\n");
212 // // s[0]==2: ctrlfile, must start with 'c'
213 // // s[0]==3: datafile, must start with 'd'
214 // if (fname[0] != s[0] + ('c'-2))
217 expected_len = bb_strtou(s + 1, NULL, 10);
218 if (errno || expected_len < 0) {
219 printf("Bad length\n");
222 if (2 == s[0] && expected_len > 16 * 1024) {
224 // ctrlfile can't be big (we want to read it back later!)
225 printf("File is too big\n");
231 // spooling mode: dump both files
232 // job in flight has mode 0200 "only writable"
234 fd = open3_or_warn(fname, O_CREAT | O_WRONLY | O_TRUNC | O_EXCL, 0200);
237 filenames[s[0] - 2] = xstrdup(fname);
239 // non-spooling mode:
240 // 2: control file (ignoring), 3: data file
243 fd = xopen(queue, O_RDWR | O_APPEND);
247 real_len = bb_copyfd_size(STDIN_FILENO, fd, expected_len);
248 if (real_len != expected_len) {
249 printf("Expected %d but got %d bytes\n",
250 expected_len, real_len);
253 // get ACK and see whether it is NUL (ok)
254 // (and don't trash s[0]!)
255 if (safe_read(STDIN_FILENO, &s[1], 1) != 1 || s[1] != 0) {
256 // don't send error msg to peer - it obviously
257 // doesn't follow the protocol, so probably
258 // it can't understand us either
263 // chmod completely downloaded file as "readable+writable"
265 // accumulate dump state
266 // N.B. after all files are dumped spooling should be 1+2+4==7
267 spooling |= (1 << (s[0]-1)); // bit 1: ctrlfile; bit 2: datafile
271 close(fd); // NB: can do close(-1). Who cares?
273 // spawn spool helper and exit if all files are dumped
274 if (7 == spooling && *argv) {
276 safe_write(STDOUT_FILENO, "", 1);
277 // does not return (exits 0)
278 exec_helper(filenames, argv);
283 // don't keep corrupted files
286 for (i = 2; --i >= 0; )
288 unlink(filenames[i]);