1 files changed, 282 insertions, 0 deletions
diff --git a/release/src/router/busybox/printutils/lpd.c b/release/src/router/busybox/printutils/lpd.c
new file mode 100644
index 00000000..43c22948
--- /dev/null
+++ b/release/src/router/busybox/printutils/lpd.c
@@ -0,0 +1,282 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * micro lpd
+ *
+ * Copyright (C) 2008 by Vladimir Dronnikov <dronnikov@gmail.com>
+ *
+ * Licensed under GPLv2, see file LICENSE in this tarball for details.
+ */
+
+/*
+ * A typical usage of BB lpd looks as follows:
+ * # tcpsvd -E 0 515 lpd [SPOOLDIR] [HELPER-PROG [ARGS...]]
+ *
+ * This starts TCP listener on port 515 (default for LP protocol).
+ * When a client connection is made (via lpr) lpd first changes its
+ * working directory to SPOOLDIR (current dir is the default).
+ *
+ * SPOOLDIR is the spool directory which contains printing queues
+ * and should have the following structure:
+ *
+ * SPOOLDIR/
+ *      <queue1>
+ *      ...
+ *      <queueN>
+ *
+ * <queueX> can be of two types:
+ *      A. a printer character device, an ordinary file or a link to such;
+ *      B. a directory.
+ *
+ * In case A lpd just dumps the data it receives from client (lpr) to the
+ * end of queue file/device. This is non-spooling mode.
+ *
+ * In case B lpd enters spooling mode. It reliably saves client data along
+ * with control info in two unique files under the queue directory. These
+ * files are named dfAXXXHHHH and cfAXXXHHHH, where XXX is the job number
+ * and HHHH is the client hostname. Unless a printing helper application
+ * is specified lpd is done at this point.
+ *
+ * NB: file names are produced by peer! They actually may be anything at all.
+ * lpd only sanitizes them (by removing most non-alphanumerics).
+ *
+ * If HELPER-PROG (with optional arguments) is specified then lpd continues
+ * to process client data:
+ *      1. it reads and parses control file (cfA...). The parse process
+ *      results in setting environment variables whose values were passed
+ *      in control file; when parsing is complete, lpd deletes control file.
+ *      2. it spawns specified helper application. It is then
+ *      the helper application who is responsible for both actual printing
+ *      and deleting of processed data file.
+ *
+ * A good lpr passes control files which when parsed provides the following
+ * variables:
+ * $H = host which issues the job
+ * $P = user who prints
+ * $C = class of printing (what is printed on banner page)
+ * $J = the name of the job
+ * $L = print banner page
+ * $M = the user to whom a mail should be sent if a problem occurs
+ *
+ * We specifically filter out and NOT provide:
+ * $l = name of datafile ("dfAxxx") - file whose content are to be printed
+ *
+ * lpd provides $DATAFILE instead - the ACTUAL name
+ * of the datafile under which it was saved.
+ * $l would be not reliable (you would be at mercy of remote peer).
+ *
+ * Thus, a typical helper can be something like this:
+ * #!/bin/sh
+ * cat ./"$DATAFILE" >/dev/lp0
+ * mv -f ./"$DATAFILE" save/
+ */
+
+#include "libbb.h"
+
+// strip argument of bad chars
+static char *sane(char *str)
+{
+	char *s = str;
+	char *p = s;
+	while (*s) {
+		if (isalnum(*s) || '-' == *s || '_' == *s) {
+			*p++ = *s;
+		}
+		s++;
+	}
+	*p = '\0';
+	return str;
+}
+
+static char *xmalloc_read_stdin(void)
+{
+	// SECURITY:
+	size_t max = 4 * 1024; // more than enough for commands!
+	return xmalloc_reads(STDIN_FILENO, NULL, &max);
+}
+
+int lpd_main(int argc, char *argv[]) MAIN_EXTERNALLY_VISIBLE;
+int lpd_main(int argc UNUSED_PARAM, char *argv[])
+{
+	int spooling = spooling; // for compiler
+	char *s, *queue;
+	char *filenames[2];
+
+	// goto spool directory
+	if (*++argv)
+		xchdir(*argv++);
+
+	// error messages of xfuncs will be sent over network
+	xdup2(STDOUT_FILENO, STDERR_FILENO);
+
+	// nullify ctrl/data filenames
+	memset(filenames, 0, sizeof(filenames));
+
+	// read command
+	s = queue = xmalloc_read_stdin();
+	// we understand only "receive job" command
+	if (2 != *queue) {
+ unsupported_cmd:
+		printf("Command %02x %s\n",
+			(unsigned char)s[0], "is not supported");
+		goto err_exit;
+	}
+
+	// parse command: "2 | QUEUE_NAME | '\n'"
+	queue++;
+	// protect against "/../" attacks
+	// *strchrnul(queue, '\n') = '\0'; - redundant, sane() will do
+	if (!*sane(queue))
+		return EXIT_FAILURE;
+
+	// queue is a directory -> chdir to it and enter spooling mode
+	spooling = chdir(queue) + 1; // 0: cannot chdir, 1: done
+	// we don't free(s), we might need "queue" var later
+
+	while (1) {
+		char *fname;
+		int fd;
+		// int is easier than ssize_t: can use xatoi_u,
+		// and can correctly display error returns (-1)
+		int expected_len, real_len;
+
+		// signal OK
+		safe_write(STDOUT_FILENO, "", 1);
+
+		// get subcommand
+		// valid s must be of form: "SUBCMD | LEN | space | FNAME"
+		// N.B. we bail out on any error
+		s = xmalloc_read_stdin();
+		if (!s) { // (probably) EOF
+			char *p, *q, var[2];
+
+			// non-spooling mode or no spool helper specified
+			if (!spooling || !*argv)
+				return EXIT_SUCCESS; // the only non-error exit
+			// spooling mode but we didn't see both ctrlfile & datafile
+			if (spooling != 7)
+				goto err_exit; // reject job
+
+			// spooling mode and spool helper specified -> exec spool helper
+			// (we exit 127 if helper cannot be executed)
+			var[1] = '\0';
+			// read and delete ctrlfile
+			q = xmalloc_xopen_read_close(filenames[0], NULL);
+			unlink(filenames[0]);
+			// provide datafile name
+			// we can use leaky setenv since we are about to exec or exit
+			xsetenv("DATAFILE", filenames[1]);
+			// parse control file by "\n"
+			while ((p = strchr(q, '\n')) != NULL && isalpha(*q)) {
+				*p++ = '\0';
+				// q is a line of <SYM><VALUE>,
+				// we are setting environment string <SYM>=<VALUE>.
+				// Ignoring "l<datafile>", exporting others:
+				if (*q != 'l') {
+					var[0] = *q++;
+					xsetenv(var, q);
+				}
+				q = p; // next line
+			}
+			// helper should not talk over network.
+			// this call reopens stdio fds to "/dev/null"
+			// (no daemonization is done)
+			bb_daemonize_or_rexec(DAEMON_DEVNULL_STDIO | DAEMON_ONLY_SANITIZE, NULL);
+			BB_EXECVP(*argv, argv);
+			exit(127);
+		}
+
+		// validate input.
+		// we understand only "control file" or "data file" cmds
+		if (2 != s[0] && 3 != s[0])
+			goto unsupported_cmd;
+		if (spooling & (1 << (s[0]-1))) {
+			printf("Duplicated subcommand\n");
+			goto err_exit;
+		}
+		// get filename
+		*strchrnul(s, '\n') = '\0';
+		fname = strchr(s, ' ');
+		if (!fname) {
+// bad_fname:
+			printf("No or bad filename\n");
+			goto err_exit;
+		}
+		*fname++ = '\0';
+//		// s[0]==2: ctrlfile, must start with 'c'
+//		// s[0]==3: datafile, must start with 'd'
+//		if (fname[0] != s[0] + ('c'-2))
+//			goto bad_fname;
+		// get length
+		expected_len = bb_strtou(s + 1, NULL, 10);
+		if (errno || expected_len < 0) {
+			printf("Bad length\n");
+			goto err_exit;
+		}
+		if (2 == s[0] && expected_len > 16 * 1024) {
+			// SECURITY:
+			// ctrlfile can't be big (we want to read it back later!)
+			printf("File is too big\n");
+			goto err_exit;
+		}
+
+		// open the file
+		if (spooling) {
+			// spooling mode: dump both files
+			// job in flight has mode 0200 "only writable"
+			sane(fname);
+			fd = open3_or_warn(fname, O_CREAT | O_WRONLY | O_TRUNC | O_EXCL, 0200);
+			if (fd < 0)
+				goto err_exit;
+			filenames[s[0] - 2] = xstrdup(fname);
+		} else {
+			// non-spooling mode:
+			// 2: control file (ignoring), 3: data file
+			fd = -1;
+			if (3 == s[0])
+				fd = xopen(queue, O_RDWR | O_APPEND);
+		}
+
+		// signal OK
+		safe_write(STDOUT_FILENO, "", 1);
+
+		// copy the file
+		real_len = bb_copyfd_size(STDIN_FILENO, fd, expected_len);
+		if (real_len != expected_len) {
+			printf("Expected %d but got %d bytes\n",
+				expected_len, real_len);
+			goto err_exit;
+		}
+		// get EOF indicator, see whether it is NUL (ok)
+		// (and don't trash s[0]!)
+		if (safe_read(STDIN_FILENO, &s[1], 1) != 1 || s[1] != 0) {
+			// don't send error msg to peer - it obviously
+			// doesn't follow the protocol, so probably
+			// it can't understand us either
+			goto err_exit;
+		}
+
+		if (spooling) {
+			// chmod completely downloaded file as "readable+writable"
+			fchmod(fd, 0600);
+			// accumulate dump state
+			// N.B. after all files are dumped spooling should be 1+2+4==7
+			spooling |= (1 << (s[0]-1)); // bit 1: ctrlfile; bit 2: datafile
+		}
+
+		free(s);
+		close(fd); // NB: can do close(-1). Who cares?
+
+		// NB: don't do "signal OK" write here, it will be done
+		// at the top of the loop
+	} // while (1)
+
+ err_exit:
+	// don't keep corrupted files
+	if (spooling) {
+#define i spooling
+		for (i = 2; --i >= 0; )
+			if (filenames[i])
+				unlink(filenames[i]);
+	}
+	return EXIT_FAILURE;
+}