lpd: maintainer's update: now with spool helpers

function                                             old     new   delta
exec_helper                                            -     227    +227
sane                                                  66     117     +51
packed_usage                                       23806   23828     +22
lpd_main                                             486     504     +18
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 3/0 up/down: 318/0)             Total: 318 bytes
This commit is contained in:
Denis Vlasenko 2008-03-23 23:40:18 +00:00
parent c93b162248
commit a79428998d
2 changed files with 133 additions and 18 deletions

View File

@ -2108,10 +2108,10 @@
"losetup -f will show the first loop free loop device\n\n"
#define lpd_trivial_usage \
"SPOOLDIR"
"SPOOLDIR [HELPER [ARGS...]]"
#define lpd_full_usage \
"Example:" \
"\n tcpsvd -E 0 515 softlimit -m 99999 lpd /var/spool"
"\n tcpsvd -E 0 515 softlimit -m 999999 lpd /var/spool ./print"
#define lpq_trivial_usage \
"[-P queue[@host[:port]]] [-U USERNAME] [-d JOBID...] [-fs]"

View File

@ -6,10 +6,123 @@
*
* 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 means a network listener is started on port 515 (default for LP protocol).
* When a client connection is made (via lpr) lpd first change its working directory to SPOOLDIR.
*
* 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 or an ordinary file 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.
*
* 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 processed data file.
*
* A good lpr passes control files which when parsed provide 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
* $l = name of datafile ("dfAxxx") - file whose content are to be printed
*
* Thus, a typical helper can be something like this:
* #!/bin/sh
* cat "$l" >/dev/lp0
* mv -f "$l" save/
*
*/
#include "libbb.h"
// TODO: xmalloc_reads is vulnerable to remote OOM attack!
// strip argument of bad chars
static char *sane(char *str)
{
char *s = str;
char *p = s;
while (*s) {
if (isalnum(*s) || '-' == *s) {
*p++ = *s;
}
s++;
}
*p = '\0';
return str;
}
static void exec_helper(const char *fname, char **argv)
{
char *p, *q, *file;
char *our_env[12];
int env_idx;
// read control file
file = q = xmalloc_open_read_close(fname, NULL);
// delete control file
unlink(fname);
// parse control file by "\n"
env_idx = 0;
while ((p = strchr(q, '\n')) != NULL
&& isalpha(*q)
&& env_idx < ARRAY_SIZE(our_env)
) {
*p++ = '\0';
// here q is a line of <SYM><VALUE>
// let us set environment string <SYM>=<VALUE>
// N.B. setenv is leaky!
// We have to use putenv(malloced_str),
// and unsetenv+free (in parent)
our_env[env_idx] = xasprintf("%c=%s", *q, q+1);
putenv(our_env[env_idx]);
env_idx++;
// next line, plz!
q = p;
}
if (vfork() == 0) {
// CHILD
// we are the helper. we wanna be silent
// 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);
}
// PARENT (or vfork error)
// clean up...
free(file);
while (--env_idx >= 0) {
*strchrnul(our_env[env_idx], '=') = '\0';
unsetenv(our_env[env_idx]);
}
}
int lpd_main(int argc, char *argv[]) MAIN_EXTERNALLY_VISIBLE;
int lpd_main(int argc ATTRIBUTE_UNUSED, char *argv[])
{
@ -27,22 +140,16 @@ int lpd_main(int argc ATTRIBUTE_UNUSED, char *argv[])
return EXIT_FAILURE;
}
// spool directory contains either links to real printer devices or just simple files
// these links or files are called "queues"
// OR
// if a directory named as given queue exists within spool directory
// then LPD enters spooling mode and just dumps both control and data files to it
// goto spool directory
if (argv[1])
xchdir(argv[1]);
if (*++argv)
xchdir(*argv++);
// parse command: "\x2QUEUE_NAME\n"
queue = s + 1;
*strchrnul(s, '\n') = '\0';
// protect against "/../" attacks
if (queue[0] == '.' || strstr(queue, "/."))
if (!*sane(queue))
return EXIT_FAILURE;
// queue is a directory -> chdir to it and enter spooling mode
@ -80,10 +187,8 @@ int lpd_main(int argc ATTRIBUTE_UNUSED, char *argv[])
*fname++ = '\0';
if (spooling) {
// spooling mode: dump both files
// make "/../" attacks in file names ineffective
xchroot(".");
// job in flight has mode 0200 "only writable"
fd = xopen3(fname, O_CREAT | O_WRONLY | O_TRUNC | O_EXCL, 0200);
fd = xopen3(sane(fname), O_CREAT | O_WRONLY | O_TRUNC | O_EXCL, 0200);
} else {
// non-spooling mode:
// 2: control file (ignoring), 3: data file
@ -99,6 +204,20 @@ int lpd_main(int argc ATTRIBUTE_UNUSED, char *argv[])
expected_len, real_len);
return EXIT_FAILURE;
}
// chmod completely downloaded file as "readable+writable" ...
if (spooling) {
fchmod(fd, 0600);
// ... and accumulate dump state.
// N.B. after all files are dumped spooling should be 1+2+3==6
spooling += s[0];
}
close(fd); // NB: can do close(-1). Who cares?
// are all files dumped? -> spawn spool helper
if (6 == spooling && *argv) {
fname[0] = 'c'; // pass control file name
exec_helper(fname, argv);
}
// get ACK and see whether it is NUL (ok)
if (read(STDIN_FILENO, s, 1) != 1 || s[0] != 0) {
// don't send error msg to peer - it obviously
@ -106,10 +225,6 @@ int lpd_main(int argc ATTRIBUTE_UNUSED, char *argv[])
// it can't understand us either
return EXIT_FAILURE;
}
// chmod completely downloaded job as "readable+writable"
if (spooling)
fchmod(fd, 0600);
close(fd); // NB: can do close(-1). Who cares?
free(s);
} /* while (1) */
}