Contents of /tags/mkinitrd-6_1_5/busybox/printutils/lpd.c
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Wed Aug 5 17:52:52 2009 UTC (15 years, 1 month ago) by niro
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Wed Aug 5 17:52:52 2009 UTC (15 years, 1 month ago) by niro
File MIME type: text/plain
File size: 8266 byte(s)
tagged 'mkinitrd-6_1_5'
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 tarball for details. |
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 | |
73 | #include "libbb.h" |
74 | |
75 | // strip argument of bad chars |
76 | static char *sane(char *str) |
77 | { |
78 | char *s = str; |
79 | char *p = s; |
80 | while (*s) { |
81 | if (isalnum(*s) || '-' == *s || '_' == *s) { |
82 | *p++ = *s; |
83 | } |
84 | s++; |
85 | } |
86 | *p = '\0'; |
87 | return str; |
88 | } |
89 | |
90 | static char *xmalloc_read_stdin(void) |
91 | { |
92 | // SECURITY: |
93 | size_t max = 4 * 1024; // more than enough for commands! |
94 | return xmalloc_reads(STDIN_FILENO, NULL, &max); |
95 | } |
96 | |
97 | int lpd_main(int argc, char *argv[]) MAIN_EXTERNALLY_VISIBLE; |
98 | int lpd_main(int argc UNUSED_PARAM, char *argv[]) |
99 | { |
100 | int spooling = spooling; // for compiler |
101 | char *s, *queue; |
102 | char *filenames[2]; |
103 | |
104 | // goto spool directory |
105 | if (*++argv) |
106 | xchdir(*argv++); |
107 | |
108 | // error messages of xfuncs will be sent over network |
109 | xdup2(STDOUT_FILENO, STDERR_FILENO); |
110 | |
111 | // nullify ctrl/data filenames |
112 | memset(filenames, 0, sizeof(filenames)); |
113 | |
114 | // read command |
115 | s = queue = xmalloc_read_stdin(); |
116 | // we understand only "receive job" command |
117 | if (2 != *queue) { |
118 | unsupported_cmd: |
119 | printf("Command %02x %s\n", |
120 | (unsigned char)s[0], "is not supported"); |
121 | goto err_exit; |
122 | } |
123 | |
124 | // parse command: "2 | QUEUE_NAME | '\n'" |
125 | queue++; |
126 | // protect against "/../" attacks |
127 | // *strchrnul(queue, '\n') = '\0'; - redundant, sane() will do |
128 | if (!*sane(queue)) |
129 | return EXIT_FAILURE; |
130 | |
131 | // queue is a directory -> chdir to it and enter spooling mode |
132 | spooling = chdir(queue) + 1; // 0: cannot chdir, 1: done |
133 | // we don't free(s), we might need "queue" var later |
134 | |
135 | while (1) { |
136 | char *fname; |
137 | int fd; |
138 | // int is easier than ssize_t: can use xatoi_u, |
139 | // and can correctly display error returns (-1) |
140 | int expected_len, real_len; |
141 | |
142 | // signal OK |
143 | safe_write(STDOUT_FILENO, "", 1); |
144 | |
145 | // get subcommand |
146 | // valid s must be of form: "SUBCMD | LEN | space | FNAME" |
147 | // N.B. we bail out on any error |
148 | s = xmalloc_read_stdin(); |
149 | if (!s) { // (probably) EOF |
150 | char *p, *q, var[2]; |
151 | |
152 | // non-spooling mode or no spool helper specified |
153 | if (!spooling || !*argv) |
154 | return EXIT_SUCCESS; // the only non-error exit |
155 | // spooling mode but we didn't see both ctrlfile & datafile |
156 | if (spooling != 7) |
157 | goto err_exit; // reject job |
158 | |
159 | // spooling mode and spool helper specified -> exec spool helper |
160 | // (we exit 127 if helper cannot be executed) |
161 | var[1] = '\0'; |
162 | // read and delete ctrlfile |
163 | q = xmalloc_xopen_read_close(filenames[0], NULL); |
164 | unlink(filenames[0]); |
165 | // provide datafile name |
166 | // we can use leaky setenv since we are about to exec or exit |
167 | xsetenv("DATAFILE", filenames[1]); |
168 | // parse control file by "\n" |
169 | while ((p = strchr(q, '\n')) != NULL && isalpha(*q)) { |
170 | *p++ = '\0'; |
171 | // q is a line of <SYM><VALUE>, |
172 | // we are setting environment string <SYM>=<VALUE>. |
173 | // Ignoring "l<datafile>", exporting others: |
174 | if (*q != 'l') { |
175 | var[0] = *q++; |
176 | xsetenv(var, q); |
177 | } |
178 | q = p; // next line |
179 | } |
180 | // helper should not talk over network. |
181 | // this call reopens stdio fds to "/dev/null" |
182 | // (no daemonization is done) |
183 | bb_daemonize_or_rexec(DAEMON_DEVNULL_STDIO | DAEMON_ONLY_SANITIZE, NULL); |
184 | BB_EXECVP(*argv, argv); |
185 | exit(127); |
186 | } |
187 | |
188 | // validate input. |
189 | // we understand only "control file" or "data file" cmds |
190 | if (2 != s[0] && 3 != s[0]) |
191 | goto unsupported_cmd; |
192 | if (spooling & (1 << (s[0]-1))) { |
193 | printf("Duplicated subcommand\n"); |
194 | goto err_exit; |
195 | } |
196 | // get filename |
197 | *strchrnul(s, '\n') = '\0'; |
198 | fname = strchr(s, ' '); |
199 | if (!fname) { |
200 | // bad_fname: |
201 | printf("No or bad filename\n"); |
202 | goto err_exit; |
203 | } |
204 | *fname++ = '\0'; |
205 | // // s[0]==2: ctrlfile, must start with 'c' |
206 | // // s[0]==3: datafile, must start with 'd' |
207 | // if (fname[0] != s[0] + ('c'-2)) |
208 | // goto bad_fname; |
209 | // get length |
210 | expected_len = bb_strtou(s + 1, NULL, 10); |
211 | if (errno || expected_len < 0) { |
212 | printf("Bad length\n"); |
213 | goto err_exit; |
214 | } |
215 | if (2 == s[0] && expected_len > 16 * 1024) { |
216 | // SECURITY: |
217 | // ctrlfile can't be big (we want to read it back later!) |
218 | printf("File is too big\n"); |
219 | goto err_exit; |
220 | } |
221 | |
222 | // open the file |
223 | if (spooling) { |
224 | // spooling mode: dump both files |
225 | // job in flight has mode 0200 "only writable" |
226 | sane(fname); |
227 | fd = open3_or_warn(fname, O_CREAT | O_WRONLY | O_TRUNC | O_EXCL, 0200); |
228 | if (fd < 0) |
229 | goto err_exit; |
230 | filenames[s[0] - 2] = xstrdup(fname); |
231 | } else { |
232 | // non-spooling mode: |
233 | // 2: control file (ignoring), 3: data file |
234 | fd = -1; |
235 | if (3 == s[0]) |
236 | fd = xopen(queue, O_RDWR | O_APPEND); |
237 | } |
238 | |
239 | // signal OK |
240 | safe_write(STDOUT_FILENO, "", 1); |
241 | |
242 | // copy the file |
243 | real_len = bb_copyfd_size(STDIN_FILENO, fd, expected_len); |
244 | if (real_len != expected_len) { |
245 | printf("Expected %d but got %d bytes\n", |
246 | expected_len, real_len); |
247 | goto err_exit; |
248 | } |
249 | // get EOF indicator, see whether it is NUL (ok) |
250 | // (and don't trash s[0]!) |
251 | if (safe_read(STDIN_FILENO, &s[1], 1) != 1 || s[1] != 0) { |
252 | // don't send error msg to peer - it obviously |
253 | // doesn't follow the protocol, so probably |
254 | // it can't understand us either |
255 | goto err_exit; |
256 | } |
257 | |
258 | if (spooling) { |
259 | // chmod completely downloaded file as "readable+writable" |
260 | fchmod(fd, 0600); |
261 | // accumulate dump state |
262 | // N.B. after all files are dumped spooling should be 1+2+4==7 |
263 | spooling |= (1 << (s[0]-1)); // bit 1: ctrlfile; bit 2: datafile |
264 | } |
265 | |
266 | free(s); |
267 | close(fd); // NB: can do close(-1). Who cares? |
268 | |
269 | // NB: don't do "signal OK" write here, it will be done |
270 | // at the top of the loop |
271 | } // while (1) |
272 | |
273 | err_exit: |
274 | // don't keep corrupted files |
275 | if (spooling) { |
276 | #define i spooling |
277 | for (i = 2; --i >= 0; ) |
278 | if (filenames[i]) |
279 | unlink(filenames[i]); |
280 | } |
281 | return EXIT_FAILURE; |
282 | } |