f39653e30
Denis Vlasenko
2008-03-24
Subject
lpd: debugging by Vladimir: he found vda's breakage (trashed s[0])!
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printutils/lpd.c+52 -42
| @@ -9,10 +9,11 @@ | |
| /* | |
| * A typical usage of BB lpd looks as follows: | |
| - | * # tcpsvd -E 0 515 lpd SPOOLDIR [HELPER-PROG [ARGS...]] |
| + | * # 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. |
| + | * This starts TCP listener on port 515 (default for LP protocol). |
| + | * When a client connection is made (via lpr) lpd first changes its |
| + | * working directory to SPOOLDIR (current dir is the default). |
| * | |
| * SPOOLDIR is the spool directory which contains printing queues | |
| * and should have the following structure: | |
| @@ -23,44 +24,50 @@ | |
| * <queueN> | |
| * | |
| * <queueX> can be of two types: | |
| - | * A. a printer character device or an ordinary file a link to such; |
| + | * A. a printer character device, an ordinary file or 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 |
| + | * 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. | |
| * | |
| - | * NB: file names are produced by peer! They actually may be anything at all! |
| + | * NB: file names are produced by peer! They actually may be anything at all. |
| * lpd only sanitizes them (by removing most non-alphanumerics). | |
| * | |
| - | * 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. |
| + | * 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 of processed data file. |
| * | |
| - | * A good lpr passes control files which when parsed provide the following variables: |
| + | * A good lpr passes control files which when parsed provides 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 | |
| + | * |
| + | * We specifically filter out and NOT provide: |
| * $l = name of datafile ("dfAxxx") - file whose content are to be printed | |
| * | |
| - | * lpd also provides $DATAFILE environment variable - the ACTUAL name |
| + | * lpd provides $DATAFILE instead - the ACTUAL name |
| * of the datafile under which it was saved. | |
| - | * $l is not reliable (you are at mercy of remote peer), DON'T USE IT. |
| + | * $l would be not reliable (you would be at mercy of remote peer). |
| * | |
| * Thus, a typical helper can be something like this: | |
| * #!/bin/sh | |
| - | * cat "$l" >/dev/lp0 |
| - | * mv -f "$l" save/ |
| + | * cat ./"$DATAFILE" >/dev/lp0 |
| + | * mv -f ./"$DATAFILE" save/ |
| */ | |
| #include "libbb.h" | |
| @@ -87,6 +94,8 @@ static void exec_helper(char **filenames, char **argv) | |
| char *p, *q; | |
| char var[2]; | |
| + | var[1] = '\0'; |
| + | |
| // read and delete ctrlfile | |
| q = xmalloc_open_read_close(filenames[0], NULL); | |
| unlink(filenames[0]); | |
| @@ -97,11 +106,13 @@ static void exec_helper(char **filenames, char **argv) | |
| && isalpha(*q) | |
| ) { | |
| *p++ = '\0'; | |
| - | // here q is a line of <SYM><VALUE> |
| - | // let us set environment string <SYM>=<VALUE> |
| - | var[0] = *q++; |
| - | var[1] = '\0'; |
| - | xsetenv(var, q); |
| + | // q is a line of <SYM><VALUE>, |
| + | // we are setting environment string <SYM>=<VALUE>. |
| + | // Ignoring "l<datafile>", exporting others: |
| + | if (*q != 'l') { |
| + | var[0] = *q++; |
| + | xsetenv(var, q); |
| + | } |
| // next line, plz! | |
| q = p; | |
| } | |
| @@ -110,7 +121,7 @@ static void exec_helper(char **filenames, char **argv) | |
| // (no daemonization is done) | |
| bb_daemonize_or_rexec(DAEMON_DEVNULL_STDIO | DAEMON_ONLY_SANITIZE, NULL); | |
| BB_EXECVP(*argv, argv); | |
| - | exit(0); |
| + | exit(127); // it IS error if helper cannot be executed! |
| } | |
| static char *xmalloc_read_stdin(void) | |
| @@ -124,7 +135,6 @@ int lpd_main(int argc, char *argv[]) MAIN_EXTERNALLY_VISIBLE; | |
| int lpd_main(int argc ATTRIBUTE_UNUSED, char *argv[]) | |
| { | |
| int spooling = spooling; // for compiler | |
| - | int seen; |
| char *s, *queue; | |
| char *filenames[2]; | |
| @@ -135,8 +145,8 @@ int lpd_main(int argc ATTRIBUTE_UNUSED, char *argv[]) | |
| // error messages of xfuncs will be sent over network | |
| xdup2(STDOUT_FILENO, STDERR_FILENO); | |
| - | filenames[0] = NULL; // ctrlfile name |
| - | filenames[1] = NULL; // datafile name |
| + | // nullify ctrl/data filenames |
| + | memset(filenames, 0, sizeof(filenames)); |
| // read command | |
| s = queue = xmalloc_read_stdin(); | |
| @@ -157,8 +167,7 @@ int lpd_main(int argc ATTRIBUTE_UNUSED, char *argv[]) | |
| // queue is a directory -> chdir to it and enter spooling mode | |
| spooling = chdir(queue) + 1; // 0: cannot chdir, 1: done | |
| - | seen = 0; |
| - | // we don't free(queue), we might need it later |
| + | // we don't free(s), we might need "queue" var later |
| while (1) { | |
| char *fname; | |
| @@ -175,7 +184,7 @@ int lpd_main(int argc ATTRIBUTE_UNUSED, char *argv[]) | |
| // N.B. we bail out on any error | |
| s = xmalloc_read_stdin(); | |
| if (!s) { // (probably) EOF | |
| - | if (spooling /* && 6 != spooling - always true */) { |
| + | if (spooling /* && 7 != spooling - always true */) { |
| // we didn't see both ctrlfile & datafile! | |
| goto err_exit; | |
| } | |
| @@ -187,11 +196,10 @@ int lpd_main(int argc ATTRIBUTE_UNUSED, char *argv[]) | |
| // we understand only "control file" or "data file" cmds | |
| if (2 != s[0] && 3 != s[0]) | |
| goto unsupported_cmd; | |
| - | if (seen & (s[0] - 1)) { |
| + | if (spooling & (1 << (s[0]-1))) { |
| printf("Duplicated subcommand\n"); | |
| goto err_exit; | |
| } | |
| - | seen &= (s[0] - 1); // bit 1: ctrlfile; bit 2: datafile |
| // get filename | |
| *strchrnul(s, '\n') = '\0'; | |
| fname = strchr(s, ' '); | |
| @@ -243,9 +251,10 @@ int lpd_main(int argc ATTRIBUTE_UNUSED, char *argv[]) | |
| goto err_exit; | |
| } | |
| // get ACK and see whether it is NUL (ok) | |
| - | if (safe_read(STDIN_FILENO, s, 1) != 1 || s[0] != 0) { |
| + | // (and don't trash s[0]!) |
| + | if (safe_read(STDIN_FILENO, &s[1], 1) != 1 || s[1] != 0) { |
| // don't send error msg to peer - it obviously | |
| - | // don't follow the protocol, so probably |
| + | // doesn't follow the protocol, so probably |
| // it can't understand us either | |
| goto err_exit; | |
| } | |
| @@ -254,14 +263,15 @@ int lpd_main(int argc ATTRIBUTE_UNUSED, char *argv[]) | |
| // chmod completely downloaded file as "readable+writable" | |
| fchmod(fd, 0600); | |
| // accumulate dump state | |
| - | // N.B. after all files are dumped spooling should be 1+2+3==6 |
| - | spooling += s[0]; |
| + | // N.B. after all files are dumped spooling should be 1+2+4==7 |
| + | spooling |= (1 << (s[0]-1)); // bit 1: ctrlfile; bit 2: datafile |
| } | |
| + | |
| free(s); | |
| close(fd); // NB: can do close(-1). Who cares? | |
| // spawn spool helper and exit if all files are dumped | |
| - | if (6 == spooling && *argv) { |
| + | if (7 == spooling && *argv) { |
| // signal OK | |
| safe_write(STDOUT_FILENO, "", 1); | |
| // does not return (exits 0) | |
| @@ -272,10 +282,10 @@ int lpd_main(int argc ATTRIBUTE_UNUSED, char *argv[]) | |
| err_exit: | |
| // don't keep corrupted files | |
| if (spooling) { | |
| - | if (filenames[0]) |
| - | unlink(filenames[0]); |
| - | if (filenames[1]) |
| - | unlink(filenames[1]); |
| + | #define i spooling |
| + | for (i = 2; --i >= 0; ) |
| + | if (filenames[i]) |
| + | unlink(filenames[i]); |
| } | |
| return EXIT_FAILURE; | |
| } | |