1/* vi: set sw=4 ts=4: */ 2/* 3 * micro lpd 4 * 5 * Copyright (C) 2008 by Vladimir Dronnikov <dronnikov@gmail.com> 6 * 7 * Licensed under GPLv2, see file LICENSE in this source tree. 8 */ 9 10/* 11 * A typical usage of BB lpd looks as follows: 12 * # tcpsvd -E 0 515 lpd [SPOOLDIR] [HELPER-PROG [ARGS...]] 13 * 14 * This starts TCP listener on port 515 (default for LP protocol). 15 * When a client connection is made (via lpr) lpd first changes its 16 * working directory to SPOOLDIR (current dir is the default). 17 * 18 * SPOOLDIR is the spool directory which contains printing queues 19 * and should have the following structure: 20 * 21 * SPOOLDIR/ 22 * <queue1> 23 * ... 24 * <queueN> 25 * 26 * <queueX> can be of two types: 27 * A. a printer character device, an ordinary file or a link to such; 28 * B. a directory. 29 * 30 * In case A lpd just dumps the data it receives from client (lpr) to the 31 * end of queue file/device. This is non-spooling mode. 32 * 33 * In case B lpd enters spooling mode. It reliably saves client data along 34 * with control info in two unique files under the queue directory. These 35 * files are named dfAXXXHHHH and cfAXXXHHHH, where XXX is the job number 36 * and HHHH is the client hostname. Unless a printing helper application 37 * is specified lpd is done at this point. 38 * 39 * NB: file names are produced by peer! They actually may be anything at all. 40 * lpd only sanitizes them (by removing most non-alphanumerics). 41 * 42 * If HELPER-PROG (with optional arguments) is specified then lpd continues 43 * to process client data: 44 * 1. it reads and parses control file (cfA...). The parse process 45 * results in setting environment variables whose values were passed 46 * in control file; when parsing is complete, lpd deletes control file. 47 * 2. it spawns specified helper application. It is then 48 * the helper application who is responsible for both actual printing 49 * and deleting of processed data file. 50 * 51 * A good lpr passes control files which when parsed provides the following 52 * variables: 53 * $H = host which issues the job 54 * $P = user who prints 55 * $C = class of printing (what is printed on banner page) 56 * $J = the name of the job 57 * $L = print banner page 58 * $M = the user to whom a mail should be sent if a problem occurs 59 * 60 * We specifically filter out and NOT provide: 61 * $l = name of datafile ("dfAxxx") - file whose content are to be printed 62 * 63 * lpd provides $DATAFILE instead - the ACTUAL name 64 * of the datafile under which it was saved. 65 * $l would be not reliable (you would be at mercy of remote peer). 66 * 67 * Thus, a typical helper can be something like this: 68 * #!/bin/sh 69 * cat ./"$DATAFILE" >/dev/lp0 70 * mv -f ./"$DATAFILE" save/ 71 */ 72//config:config LPD 73//config: bool "lpd (5.5 kb)" 74//config: default y 75//config: help 76//config: lpd is a print spooling daemon. 77 78//applet:IF_LPD(APPLET(lpd, BB_DIR_USR_SBIN, BB_SUID_DROP)) 79 80//kbuild:lib-$(CONFIG_LPD) += lpd.o 81 82//usage:#define lpd_trivial_usage 83//usage: "SPOOLDIR [HELPER [ARGS]]" 84//usage:#define lpd_full_usage "\n\n" 85//usage: "SPOOLDIR must contain (symlinks to) device nodes or directories" 86//usage: "\nwith names matching print queue names. In the first case, jobs are" 87//usage: "\nsent directly to the device. Otherwise each job is stored in queue" 88//usage: "\ndirectory and HELPER program is called. Name of file to print" 89//usage: "\nis passed in $DATAFILE variable." 90//usage: "\nExample:" 91//usage: "\n tcpsvd -E 0 515 softlimit -m 999999 lpd /var/spool ./print" 92 93#include "libbb.h" 94 95// strip argument of bad chars 96static char *sane(char *str) 97{ 98 char *s = str; 99 char *p = s; 100 while (*s) { 101 if (isalnum(*s) || '-' == *s || '_' == *s) { 102 *p++ = *s; 103 } 104 s++; 105 } 106 *p = '\0'; 107 return str; 108} 109 110static char *xmalloc_read_stdin(void) 111{ 112 // SECURITY: 113 size_t max = 4 * 1024; // more than enough for commands! 114 return xmalloc_reads(STDIN_FILENO, &max); 115} 116 117int lpd_main(int argc, char *argv[]) MAIN_EXTERNALLY_VISIBLE; 118int lpd_main(int argc UNUSED_PARAM, char *argv[]) 119{ 120 int spooling = spooling; // for compiler 121 char *s, *queue; 122 char *filenames[2]; 123 124 // goto spool directory 125 if (*++argv) 126 xchdir(*argv++); 127 128 // error messages of xfuncs will be sent over network 129 xdup2(STDOUT_FILENO, STDERR_FILENO); 130 131 // nullify ctrl/data filenames 132 memset(filenames, 0, sizeof(filenames)); 133 134 // read command 135 s = queue = xmalloc_read_stdin(); 136 // we understand only "receive job" command 137 if (2 != *queue) { 138 unsupported_cmd: 139 printf("Command %02x %s\n", 140 (unsigned char)s[0], "is not supported"); 141 goto err_exit; 142 } 143 144 // parse command: "2 | QUEUE_NAME | '\n'" 145 queue++; 146 // protect against "/../" attacks 147 // *strchrnul(queue, '\n') = '\0'; - redundant, sane() will do 148 if (!*sane(queue)) 149 return EXIT_FAILURE; 150 151 // queue is a directory -> chdir to it and enter spooling mode 152 spooling = chdir(queue) + 1; // 0: cannot chdir, 1: done 153 // we don't free(s), we might need "queue" var later 154 155 while (1) { 156 char *fname; 157 int fd; 158 // int is easier than ssize_t: can use xatoi_positive, 159 // and can correctly display error returns (-1) 160 int expected_len, real_len; 161 162 // signal OK 163 safe_write(STDOUT_FILENO, "", 1); 164 165 // get subcommand 166 // valid s must be of form: "SUBCMD | LEN | space | FNAME" 167 // N.B. we bail out on any error 168 s = xmalloc_read_stdin(); 169 if (!s) { // (probably) EOF 170 char *p, *q, var[2]; 171 172 // non-spooling mode or no spool helper specified 173 if (!spooling || !*argv) 174 return EXIT_SUCCESS; // the only non-error exit 175 // spooling mode but we didn't see both ctrlfile & datafile 176 if (spooling != 7) 177 goto err_exit; // reject job 178 179 // spooling mode and spool helper specified -> exec spool helper 180 // (we exit 127 if helper cannot be executed) 181 var[1] = '\0'; 182 // read and delete ctrlfile 183 q = xmalloc_xopen_read_close(filenames[0], NULL); 184 unlink(filenames[0]); 185 // provide datafile name 186 // we can use leaky setenv since we are about to exec or exit 187 xsetenv("DATAFILE", filenames[1]); 188 // parse control file by "\n" 189 while ((p = strchr(q, '\n')) != NULL && isalpha(*q)) { 190 *p++ = '\0'; 191 // q is a line of <SYM><VALUE>, 192 // we are setting environment string <SYM>=<VALUE>. 193 // Ignoring "l<datafile>", exporting others: 194 if (*q != 'l') { 195 var[0] = *q++; 196 xsetenv(var, q); 197 } 198 q = p; // next line 199 } 200 // helper should not talk over network. 201 // this call reopens stdio fds to "/dev/null". 202 bb_daemon_helper(DAEMON_DEVNULL_STDIO); 203 BB_EXECVP_or_die(argv); 204 } 205 206 // validate input. 207 // we understand only "control file" or "data file" cmds 208 if (2 != s[0] && 3 != s[0]) 209 goto unsupported_cmd; 210 if (spooling & (1 << (s[0]-1))) { 211 puts("Duplicated subcommand"); 212 goto err_exit; 213 } 214 // get filename 215 chomp(s); 216 fname = strchr(s, ' '); 217 if (!fname) { 218// bad_fname: 219 puts("No or bad filename"); 220 goto err_exit; 221 } 222 *fname++ = '\0'; 223// // s[0]==2: ctrlfile, must start with 'c' 224// // s[0]==3: datafile, must start with 'd' 225// if (fname[0] != s[0] + ('c'-2)) 226// goto bad_fname; 227 // get length 228 expected_len = bb_strtou(s + 1, NULL, 10); 229 if (errno || expected_len < 0) { 230 puts("Bad length"); 231 goto err_exit; 232 } 233 if (2 == s[0] && expected_len > 16 * 1024) { 234 // SECURITY: 235 // ctrlfile can't be big (we want to read it back later!) 236 puts("File is too big"); 237 goto err_exit; 238 } 239 240 // open the file 241 if (spooling) { 242 // spooling mode: dump both files 243 // job in flight has mode 0200 "only writable" 244 sane(fname); 245 fd = open3_or_warn(fname, O_CREAT | O_WRONLY | O_TRUNC | O_EXCL, 0200); 246 if (fd < 0) 247 goto err_exit; 248 filenames[s[0] - 2] = xstrdup(fname); 249 } else { 250 // non-spooling mode: 251 // 2: control file (ignoring), 3: data file 252 fd = -1; 253 if (3 == s[0]) 254 fd = xopen(queue, O_RDWR | O_APPEND); 255 } 256 257 // signal OK 258 safe_write(STDOUT_FILENO, "", 1); 259 260 // copy the file 261 real_len = bb_copyfd_size(STDIN_FILENO, fd, expected_len); 262 if (real_len != expected_len) { 263 printf("Expected %d but got %d bytes\n", 264 expected_len, real_len); 265 goto err_exit; 266 } 267 // get EOF indicator, see whether it is NUL (ok) 268 // (and don't trash s[0]!) 269 if (safe_read(STDIN_FILENO, &s[1], 1) != 1 || s[1] != 0) { 270 // don't send error msg to peer - it obviously 271 // doesn't follow the protocol, so probably 272 // it can't understand us either 273 goto err_exit; 274 } 275 276 if (spooling) { 277 // chmod completely downloaded file as "readable+writable" 278 fchmod(fd, 0600); 279 // accumulate dump state 280 // N.B. after all files are dumped spooling should be 1+2+4==7 281 spooling |= (1 << (s[0]-1)); // bit 1: ctrlfile; bit 2: datafile 282 } 283 284 free(s); 285 close(fd); // NB: can do close(-1). Who cares? 286 287 // NB: don't do "signal OK" write here, it will be done 288 // at the top of the loop 289 } // while (1) 290 291 err_exit: 292 // don't keep corrupted files 293 if (spooling) { 294#define i spooling 295 for (i = 2; --i >= 0; ) 296 if (filenames[i]) 297 unlink(filenames[i]); 298 } 299 return EXIT_FAILURE; 300} 301