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
parent
c93b162248
commit
a79428998d
@ -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]"
|
||||
|
||||
147
printutils/lpd.c
147
printutils/lpd.c
@ -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) */
|
||||
}
|
||||
|
||||
Loading…
Reference in New Issue
Block a user