[2725] | 1 | /* vi: set sw=4 ts=4: */
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| 2 | /*
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| 3 | * micro lpd
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| 4 | *
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| 5 | * Copyright (C) 2008 by Vladimir Dronnikov <dronnikov@gmail.com>
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| 6 | *
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| 7 | * Licensed under GPLv2, see file LICENSE in this source tree.
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| 8 | */
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| 9 |
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| 10 | /*
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| 11 | * A typical usage of BB lpd looks as follows:
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| 12 | * # tcpsvd -E 0 515 lpd [SPOOLDIR] [HELPER-PROG [ARGS...]]
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| 13 | *
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| 14 | * This starts TCP listener on port 515 (default for LP protocol).
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| 15 | * When a client connection is made (via lpr) lpd first changes its
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| 16 | * working directory to SPOOLDIR (current dir is the default).
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| 17 | *
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| 18 | * SPOOLDIR is the spool directory which contains printing queues
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| 19 | * and should have the following structure:
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| 20 | *
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| 21 | * SPOOLDIR/
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| 22 | * <queue1>
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| 23 | * ...
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| 24 | * <queueN>
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| 25 | *
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| 26 | * <queueX> can be of two types:
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| 27 | * A. a printer character device, an ordinary file or a link to such;
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| 28 | * B. a directory.
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| 29 | *
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| 30 | * In case A lpd just dumps the data it receives from client (lpr) to the
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| 31 | * end of queue file/device. This is non-spooling mode.
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| 32 | *
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| 33 | * In case B lpd enters spooling mode. It reliably saves client data along
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| 34 | * with control info in two unique files under the queue directory. These
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| 35 | * files are named dfAXXXHHHH and cfAXXXHHHH, where XXX is the job number
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| 36 | * and HHHH is the client hostname. Unless a printing helper application
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| 37 | * is specified lpd is done at this point.
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| 38 | *
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| 39 | * NB: file names are produced by peer! They actually may be anything at all.
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| 40 | * lpd only sanitizes them (by removing most non-alphanumerics).
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| 41 | *
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| 42 | * If HELPER-PROG (with optional arguments) is specified then lpd continues
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| 43 | * to process client data:
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| 44 | * 1. it reads and parses control file (cfA...). The parse process
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| 45 | * results in setting environment variables whose values were passed
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| 46 | * in control file; when parsing is complete, lpd deletes control file.
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| 47 | * 2. it spawns specified helper application. It is then
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| 48 | * the helper application who is responsible for both actual printing
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| 49 | * and deleting of processed data file.
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| 50 | *
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| 51 | * A good lpr passes control files which when parsed provides the following
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| 52 | * variables:
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| 53 | * $H = host which issues the job
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| 54 | * $P = user who prints
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| 55 | * $C = class of printing (what is printed on banner page)
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| 56 | * $J = the name of the job
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| 57 | * $L = print banner page
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| 58 | * $M = the user to whom a mail should be sent if a problem occurs
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| 59 | *
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| 60 | * We specifically filter out and NOT provide:
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| 61 | * $l = name of datafile ("dfAxxx") - file whose content are to be printed
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| 62 | *
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| 63 | * lpd provides $DATAFILE instead - the ACTUAL name
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| 64 | * of the datafile under which it was saved.
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| 65 | * $l would be not reliable (you would be at mercy of remote peer).
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| 66 | *
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| 67 | * Thus, a typical helper can be something like this:
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| 68 | * #!/bin/sh
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| 69 | * cat ./"$DATAFILE" >/dev/lp0
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| 70 | * mv -f ./"$DATAFILE" save/
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| 71 | */
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| 72 |
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[3232] | 73 | //usage:#define lpd_trivial_usage
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| 74 | //usage: "SPOOLDIR [HELPER [ARGS]]"
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| 75 | //usage:#define lpd_full_usage "\n\n"
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| 76 | //usage: "SPOOLDIR must contain (symlinks to) device nodes or directories"
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| 77 | //usage: "\nwith names matching print queue names. In the first case, jobs are"
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| 78 | //usage: "\nsent directly to the device. Otherwise each job is stored in queue"
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| 79 | //usage: "\ndirectory and HELPER program is called. Name of file to print"
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| 80 | //usage: "\nis passed in $DATAFILE variable."
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| 81 | //usage: "\nExample:"
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| 82 | //usage: "\n tcpsvd -E 0 515 softlimit -m 999999 lpd /var/spool ./print"
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| 83 |
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[2725] | 84 | #include "libbb.h"
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| 85 |
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| 86 | // strip argument of bad chars
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| 87 | static char *sane(char *str)
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| 88 | {
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| 89 | char *s = str;
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| 90 | char *p = s;
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| 91 | while (*s) {
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| 92 | if (isalnum(*s) || '-' == *s || '_' == *s) {
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| 93 | *p++ = *s;
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| 94 | }
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| 95 | s++;
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| 96 | }
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| 97 | *p = '\0';
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| 98 | return str;
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| 99 | }
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| 100 |
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| 101 | static char *xmalloc_read_stdin(void)
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| 102 | {
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| 103 | // SECURITY:
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| 104 | size_t max = 4 * 1024; // more than enough for commands!
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[3232] | 105 | return xmalloc_reads(STDIN_FILENO, &max);
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[2725] | 106 | }
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| 107 |
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| 108 | int lpd_main(int argc, char *argv[]) MAIN_EXTERNALLY_VISIBLE;
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| 109 | int lpd_main(int argc UNUSED_PARAM, char *argv[])
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| 110 | {
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| 111 | int spooling = spooling; // for compiler
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| 112 | char *s, *queue;
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| 113 | char *filenames[2];
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| 114 |
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| 115 | // goto spool directory
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| 116 | if (*++argv)
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| 117 | xchdir(*argv++);
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| 118 |
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| 119 | // error messages of xfuncs will be sent over network
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| 120 | xdup2(STDOUT_FILENO, STDERR_FILENO);
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| 121 |
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| 122 | // nullify ctrl/data filenames
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| 123 | memset(filenames, 0, sizeof(filenames));
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| 124 |
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| 125 | // read command
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| 126 | s = queue = xmalloc_read_stdin();
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| 127 | // we understand only "receive job" command
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| 128 | if (2 != *queue) {
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| 129 | unsupported_cmd:
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| 130 | printf("Command %02x %s\n",
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| 131 | (unsigned char)s[0], "is not supported");
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| 132 | goto err_exit;
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| 133 | }
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| 134 |
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| 135 | // parse command: "2 | QUEUE_NAME | '\n'"
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| 136 | queue++;
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| 137 | // protect against "/../" attacks
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| 138 | // *strchrnul(queue, '\n') = '\0'; - redundant, sane() will do
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| 139 | if (!*sane(queue))
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| 140 | return EXIT_FAILURE;
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| 141 |
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| 142 | // queue is a directory -> chdir to it and enter spooling mode
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| 143 | spooling = chdir(queue) + 1; // 0: cannot chdir, 1: done
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| 144 | // we don't free(s), we might need "queue" var later
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| 145 |
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| 146 | while (1) {
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| 147 | char *fname;
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| 148 | int fd;
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| 149 | // int is easier than ssize_t: can use xatoi_positive,
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| 150 | // and can correctly display error returns (-1)
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| 151 | int expected_len, real_len;
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| 152 |
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| 153 | // signal OK
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| 154 | safe_write(STDOUT_FILENO, "", 1);
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| 155 |
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| 156 | // get subcommand
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| 157 | // valid s must be of form: "SUBCMD | LEN | space | FNAME"
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| 158 | // N.B. we bail out on any error
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| 159 | s = xmalloc_read_stdin();
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| 160 | if (!s) { // (probably) EOF
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| 161 | char *p, *q, var[2];
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| 162 |
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| 163 | // non-spooling mode or no spool helper specified
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| 164 | if (!spooling || !*argv)
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| 165 | return EXIT_SUCCESS; // the only non-error exit
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| 166 | // spooling mode but we didn't see both ctrlfile & datafile
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| 167 | if (spooling != 7)
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| 168 | goto err_exit; // reject job
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| 169 |
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| 170 | // spooling mode and spool helper specified -> exec spool helper
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| 171 | // (we exit 127 if helper cannot be executed)
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| 172 | var[1] = '\0';
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| 173 | // read and delete ctrlfile
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| 174 | q = xmalloc_xopen_read_close(filenames[0], NULL);
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| 175 | unlink(filenames[0]);
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| 176 | // provide datafile name
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| 177 | // we can use leaky setenv since we are about to exec or exit
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| 178 | xsetenv("DATAFILE", filenames[1]);
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| 179 | // parse control file by "\n"
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| 180 | while ((p = strchr(q, '\n')) != NULL && isalpha(*q)) {
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| 181 | *p++ = '\0';
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| 182 | // q is a line of <SYM><VALUE>,
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| 183 | // we are setting environment string <SYM>=<VALUE>.
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| 184 | // Ignoring "l<datafile>", exporting others:
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| 185 | if (*q != 'l') {
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| 186 | var[0] = *q++;
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| 187 | xsetenv(var, q);
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| 188 | }
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| 189 | q = p; // next line
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| 190 | }
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| 191 | // helper should not talk over network.
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| 192 | // this call reopens stdio fds to "/dev/null"
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| 193 | // (no daemonization is done)
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| 194 | bb_daemonize_or_rexec(DAEMON_DEVNULL_STDIO | DAEMON_ONLY_SANITIZE, NULL);
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| 195 | BB_EXECVP_or_die(argv);
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| 196 | }
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| 197 |
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| 198 | // validate input.
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| 199 | // we understand only "control file" or "data file" cmds
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| 200 | if (2 != s[0] && 3 != s[0])
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| 201 | goto unsupported_cmd;
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| 202 | if (spooling & (1 << (s[0]-1))) {
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| 203 | printf("Duplicated subcommand\n");
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| 204 | goto err_exit;
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| 205 | }
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| 206 | // get filename
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| 207 | *strchrnul(s, '\n') = '\0';
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| 208 | fname = strchr(s, ' ');
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| 209 | if (!fname) {
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| 210 | // bad_fname:
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| 211 | printf("No or bad filename\n");
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| 212 | goto err_exit;
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| 213 | }
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| 214 | *fname++ = '\0';
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| 215 | // // s[0]==2: ctrlfile, must start with 'c'
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| 216 | // // s[0]==3: datafile, must start with 'd'
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| 217 | // if (fname[0] != s[0] + ('c'-2))
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| 218 | // goto bad_fname;
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| 219 | // get length
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| 220 | expected_len = bb_strtou(s + 1, NULL, 10);
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| 221 | if (errno || expected_len < 0) {
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| 222 | printf("Bad length\n");
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| 223 | goto err_exit;
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| 224 | }
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| 225 | if (2 == s[0] && expected_len > 16 * 1024) {
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| 226 | // SECURITY:
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| 227 | // ctrlfile can't be big (we want to read it back later!)
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| 228 | printf("File is too big\n");
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| 229 | goto err_exit;
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| 230 | }
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| 231 |
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| 232 | // open the file
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| 233 | if (spooling) {
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| 234 | // spooling mode: dump both files
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| 235 | // job in flight has mode 0200 "only writable"
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| 236 | sane(fname);
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| 237 | fd = open3_or_warn(fname, O_CREAT | O_WRONLY | O_TRUNC | O_EXCL, 0200);
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| 238 | if (fd < 0)
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| 239 | goto err_exit;
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| 240 | filenames[s[0] - 2] = xstrdup(fname);
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| 241 | } else {
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| 242 | // non-spooling mode:
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| 243 | // 2: control file (ignoring), 3: data file
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| 244 | fd = -1;
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| 245 | if (3 == s[0])
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| 246 | fd = xopen(queue, O_RDWR | O_APPEND);
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| 247 | }
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| 248 |
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| 249 | // signal OK
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| 250 | safe_write(STDOUT_FILENO, "", 1);
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| 251 |
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| 252 | // copy the file
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| 253 | real_len = bb_copyfd_size(STDIN_FILENO, fd, expected_len);
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| 254 | if (real_len != expected_len) {
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| 255 | printf("Expected %d but got %d bytes\n",
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| 256 | expected_len, real_len);
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| 257 | goto err_exit;
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| 258 | }
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| 259 | // get EOF indicator, see whether it is NUL (ok)
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| 260 | // (and don't trash s[0]!)
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| 261 | if (safe_read(STDIN_FILENO, &s[1], 1) != 1 || s[1] != 0) {
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| 262 | // don't send error msg to peer - it obviously
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| 263 | // doesn't follow the protocol, so probably
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| 264 | // it can't understand us either
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| 265 | goto err_exit;
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| 266 | }
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| 267 |
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| 268 | if (spooling) {
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| 269 | // chmod completely downloaded file as "readable+writable"
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| 270 | fchmod(fd, 0600);
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| 271 | // accumulate dump state
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| 272 | // N.B. after all files are dumped spooling should be 1+2+4==7
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| 273 | spooling |= (1 << (s[0]-1)); // bit 1: ctrlfile; bit 2: datafile
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| 274 | }
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| 275 |
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| 276 | free(s);
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| 277 | close(fd); // NB: can do close(-1). Who cares?
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| 278 |
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| 279 | // NB: don't do "signal OK" write here, it will be done
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| 280 | // at the top of the loop
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| 281 | } // while (1)
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| 282 |
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| 283 | err_exit:
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| 284 | // don't keep corrupted files
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| 285 | if (spooling) {
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| 286 | #define i spooling
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| 287 | for (i = 2; --i >= 0; )
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| 288 | if (filenames[i])
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| 289 | unlink(filenames[i]);
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| 290 | }
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| 291 | return EXIT_FAILURE;
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| 292 | }
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