394eebed66
lpr: more robust error reporting *: introduce and use xchroot libbb: full_read/write now will report partial data counts prior to error isdirectory.c: style fixes lpd_main 249 486 +237 xchroot - 29 +29 get_response_or_say_and_die 110 139 +29 full_write 52 60 +8 full_read 55 63 +8 static.newline 1 - -1 switch_root_main 404 400 -4 chpst_main 1089 1079 -10 getopt32 1370 1359 -11 chroot_main 115 101 -14 ------------------------------------------------------------------------------ (add/remove: 1/1 grow/shrink: 4/4 up/down: 311/-40) Total: 271 bytes text data bss dec hex filename 798472 728 7484 806684 c4f1c busybox_old 798775 728 7484 806987 c504b busybox_unstripped
116 lines
3.1 KiB
C
116 lines
3.1 KiB
C
/* vi: set sw=4 ts=4: */
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/*
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* micro lpd
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*
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* Copyright (C) 2008 by Vladimir Dronnikov <dronnikov@gmail.com>
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*
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* Licensed under GPLv2, see file LICENSE in this tarball for details.
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*/
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#include "libbb.h"
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// TODO: xmalloc_reads is vulnerable to remote OOM attack!
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int lpd_main(int argc, char *argv[]) MAIN_EXTERNALLY_VISIBLE;
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int lpd_main(int argc, char *argv[])
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{
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int spooling;
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char *s, *queue;
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// read command
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s = xmalloc_reads(STDIN_FILENO, NULL);
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// we understand only "receive job" command
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if (2 != *s) {
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unsupported_cmd:
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printf("Command %02x %s\n",
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(unsigned char)s[0], "is not supported");
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return EXIT_FAILURE;
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}
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// spool directory contains either links to real printer devices or just simple files
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// these links or files are called "queues"
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// OR
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// if a directory named as given queue exists within spool directory
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// then LPD enters spooling mode and just dumps both control and data files to it
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// goto spool directory
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if (argv[1])
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xchdir(argv[1]);
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// parse command: "\x2QUEUE_NAME\n"
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queue = s + 1;
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*strchrnul(s, '\n') = '\0';
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// protect against "/../" attacks
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if (queue[0] == '.' || strstr(queue, "/."))
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return EXIT_FAILURE;
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// queue is a directory -> chdir to it and enter spooling mode
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spooling = chdir(queue) + 1; /* 0: cannot chdir, 1: done */
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xdup2(STDOUT_FILENO, STDERR_FILENO);
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while (1) {
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char *fname;
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int fd;
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// int is easier than ssize_t: can use xatoi_u,
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// and can correctly display error returns (-1)
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int expected_len, real_len;
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// signal OK
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write(STDOUT_FILENO, "", 1);
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// get subcommand
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s = xmalloc_reads(STDIN_FILENO, NULL);
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if (!s)
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return EXIT_SUCCESS; // probably EOF
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// we understand only "control file" or "data file" cmds
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if (2 != s[0] && 3 != s[0])
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goto unsupported_cmd;
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*strchrnul(s, '\n') = '\0';
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// valid s must be of form: SUBCMD | LEN | SP | FNAME
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// N.B. we bail out on any error
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fname = strchr(s, ' ');
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if (!fname) {
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printf("Command %02x %s\n",
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(unsigned char)s[0], "lacks filename");
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return EXIT_FAILURE;
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}
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*fname++ = '\0';
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if (spooling) {
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// spooling mode: dump both files
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// make "/../" attacks in file names ineffective
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xchroot(".");
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// job in flight has mode 0200 "only writable"
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fd = xopen3(fname, O_CREAT | O_WRONLY | O_TRUNC | O_EXCL, 0200);
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} else {
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// non-spooling mode:
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// 2: control file (ignoring), 3: data file
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fd = -1;
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if (3 == s[0])
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fd = xopen(queue, O_RDWR | O_APPEND);
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}
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expected_len = xatoi_u(s + 1);
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real_len = bb_copyfd_size(STDIN_FILENO, fd, expected_len);
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if (spooling && real_len != expected_len) {
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unlink(fname); // don't keep corrupted files
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printf("Expected %d but got %d bytes\n",
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expected_len, real_len);
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return EXIT_FAILURE;
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}
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// get ACK and see whether it is NUL (ok)
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if (read(STDIN_FILENO, s, 1) != 1 || s[0] != 0) {
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// don't send error msg to peer - it obviously
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// don't follow the protocol, so probably
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// it can't understand us either
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return EXIT_FAILURE;
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}
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// chmod completely downloaded job as "readable+writable"
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if (spooling)
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fchmod(fd, 0600);
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close(fd); // NB: can do close(-1). Who cares?
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free(s);
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} /* while (1) */
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}
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