diplodocus.org Git - mdeliver/blob - mdeliver.c

   1 /* mdeliver.c -- Deliver a message to a Maildir.
   2  *
   3  * $Id$
   4  *
   5  * This program is in the public domain.
   6  *
   7  * mdeliver is a simple, robust MDA.  It delivers a single message
   8  * from stdin to the user's Maildir and executes (in the background) a
   9  * single program with the message filename as the first argument.
  10  * Additional arguments may be specified; see main() below for
  11  * details.
  12  *
  13  * This program does not conform strictly to POSIX.  However, the two
  14  * nonstandard interfaces it relies upon (<err.h> and <sysexits.h>)
  15  * are widespread and easily enough replaced if necessary.
  16  */
  17
  18 #include <sys/types.h>
  19 #include <sys/stat.h>
  20
  21 #include <err.h>
  22 #include <errno.h>
  23 #include <fcntl.h>
  24 #include <limits.h>
  25 #include <stdio.h>
  26 #include <stdlib.h>
  27 #include <string.h>
  28 #include <time.h>
  29 #include <unistd.h>
  30
  31 #ifndef MDELIVER_EXITCODE
  32 #include <sysexits.h>
  33 #define MDELIVER_EXITCODE EX_TEMPFAIL
  34 #endif
  35
  36 #if !defined(HOST_NAME_MAX)
  37 #if defined MAXHOSTNAMELEN
  38 #define HOST_NAME_MAX MAXHOSTNAMELEN
  39 #else
  40 #define HOST_NAME_MAX 64
  41 #endif
  42 #endif
  43
  44 /* holds 2^128 - 1 in decimal, plus '\0' */
  45 #define LEN_ULONG 40
  46
  47 /* 1 for '\0', 4 for "tmp/", HOST_NAME_MAX for the hostname, and two
  48  * LEN_ULONGs for time and pid. */
  49 #define TMPNAMLEN 1 + 4 + HOST_NAME_MAX + LEN_ULONG + LEN_ULONG
  50
  51 static char rcsid[] = "$Id$";
  52
  53 /* Write all of buf, even if write(2) is interrupted. */
  54 static ssize_t
  55 full_write(int fd, const char *buf, size_t nbytes)
  56 {
  57     ssize_t r, w = 0;
  58
  59     /* Loop until nbytes of buf have been written. */
  60     while (w < nbytes) {
  61         /* Keep trying until write succeeds without interruption. */
  62         do {
  63             r = write(fd, buf + w, nbytes - w);
  64         } while (r < 0 && errno == EINTR);
  65
  66         if (r < 0) {
  67             return r;
  68         }
  69
  70         w += r;
  71     }
  72
  73     return w;
  74 }
  75
  76 /* Find a filename for the message according to the algorithm
  77  * documented in the maildir(5) manual page from qmail
  78  * (http://www.qmail.org/qmail-manual-html/man5/maildir.html).
  79  */
  80 static void
  81 get_filename(char *fn)
  82 {
  83     pid_t pid;
  84     char host[HOST_NAME_MAX + 1];
  85     int try;
  86     time_t now;
  87     struct tm *t;
  88     char *buildfn;              /* used to build up the fn */
  89     struct stat statbuf;
  90
  91     pid = getpid();
  92
  93     if (gethostname(host, sizeof(host)) != 0) {
  94         err(MDELIVER_EXITCODE, "Failed gethostname");
  95     }
  96
  97     for (try = 0; ; try++) {
  98         now = time(NULL);
  99         t = gmtime(&now);
 100
 101         buildfn = fn + sprintf(fn, "tmp/");
 102         buildfn += strftime(buildfn, LEN_ULONG + 1, "%s.", t);
 103         buildfn += snprintf(buildfn, LEN_ULONG + 1, "%d.", pid);
 104         buildfn += sprintf(buildfn, "%s", host);
 105
 106         if (stat(fn, &statbuf) != 0) {
 107             if (errno == ENOENT) {
 108                 /* Every failure point in this program relies on errno
 109                  * describing what went wrong.  This is the one
 110                  * failure we *want*, so it is important to restore
 111                  * errno to 0 (success) before returning.
 112                  */
 113                 errno = 0;
 114                 break;
 115             }
 116         }
 117
 118         if (try == 2) {
 119             errx(MDELIVER_EXITCODE, "Attempted filename exists.");
 120         }
 121
 122         sleep(2);
 123     }
 124 }
 125
 126 /* Strip the non-RFC2822-compliant 'From ' line some busted-ass
 127  * mailers (such as Postfix) add as the first line of input.  This bit
 128  * of historical gunk originated with Berkeley mbox files, which use
 129  * this line to indicate the beginning of a message.  Postfix should
 130  * only add such a line when it is acting as an MDA and delivering to
 131  * a Berkeley mbox; the data written to an external MDA should be the
 132  * raw RFC2822 message.  >sigh<
 133  */
 134 /* buf is passed only as an (early, evil) space optimization). */
 135 static void
 136 strip_from(int fd, char *buf, char *fn)
 137 {
 138     ssize_t r;
 139
 140     r = read(STDIN_FILENO, buf, 5);
 141     if (r != 5) {
 142         unlink(fn);
 143         err(MDELIVER_EXITCODE, "Failed read from stdin");
 144     }
 145
 146     if (strncmp(buf, "From ", 5) == 0) {
 147         while ((r = read(STDIN_FILENO, buf, 1)) > 0
 148                || (r == -1 && errno == EINTR)) {
 149             if (buf[0] == '\n') {
 150                 break;
 151             }
 152         }
 153
 154         if (r == -1) {
 155             unlink(fn);
 156             err(MDELIVER_EXITCODE, "Failed read from stdin");
 157         }
 158     } else {
 159         if (full_write(fd, buf, r) != r) {
 160             unlink(fn);
 161             err(MDELIVER_EXITCODE, "Failed write(%s)", fn);
 162         }
 163     }
 164 }
 165
 166 /* Copy the message from stdin to fd. */
 167 /* buf is passed only as an (early, evil) space optimization). */
 168 static void
 169 copy_message(int fd, char *buf, char *fn)
 170 {
 171     ssize_t r;
 172
 173     while ((r = read(STDIN_FILENO, buf, BUFSIZ)) > 0
 174            || (r == -1 && errno == EINTR)) {
 175         if (full_write(fd, buf, r) != r) {
 176             unlink(fn);
 177             err(MDELIVER_EXITCODE, "Failed write(%s)", fn);
 178         }
 179     }
 180
 181     if (r == -1) {
 182         unlink(fn);
 183         err(MDELIVER_EXITCODE, "Failed read from stdin");
 184     }
 185
 186     if (fsync(fd) < 0) {
 187         unlink(fn);
 188         err(MDELIVER_EXITCODE, "Failed fsync(%s)", fn);
 189     }
 190
 191     if (close(fd) < 0) {
 192         unlink(fn);
 193         err(MDELIVER_EXITCODE, "Failed close(%s)", fn);
 194     }
 195 }
 196
 197 static void
 198 deliver(char *maildir, char *newfn)
 199 {
 200     char fn[TMPNAMLEN];
 201     int fd;
 202     char buf[BUFSIZ];           /* Allocated here only as an (early,
 203                                  * evil) space optimization. */
 204
 205     if (chdir(maildir) != 0) {
 206         err(MDELIVER_EXITCODE, "Failed chdir(%s)", maildir);
 207     }
 208
 209     get_filename(fn);
 210
 211     fd = open(fn, O_WRONLY | O_EXCL | O_CREAT, 0600);
 212     if (fd < 0) {
 213         err(MDELIVER_EXITCODE, "Failed open(%s)", fn);
 214     }
 215
 216     /* From this point, we have a tmp file, so if someting fails we
 217      * must try to unlink it before bombing. */
 218
 219     strip_from(fd, buf, fn);
 220     copy_message(fd, buf, fn);
 221
 222     strcpy(newfn, fn);
 223     memcpy(newfn, "new", 3);
 224
 225     if (rename(fn, newfn) != 0) {
 226         unlink(fn);
 227         err(MDELIVER_EXITCODE, "Failed rename(%s, new)", fn);
 228     }
 229 }
 230
 231 int
 232 main(int argc, char *argv[])
 233 {
 234     char *home;
 235     char newfn[TMPNAMLEN];
 236     pid_t pid;
 237     FILE *errfile;
 238     char *fail;
 239     int fd;
 240
 241     if (argv[1] && argv[1][0] == '-' && argv[1][1] == 'v') {
 242         puts(rcsid);
 243         return 0;
 244     }
 245
 246     if (!(home = getenv("HOME"))) {
 247         err(MDELIVER_EXITCODE, "Failed getenv(HOME)");
 248     }
 249
 250     if (chdir(home) != 0) {
 251         err(MDELIVER_EXITCODE, "Failed chdir(HOME)");
 252     }
 253
 254     deliver("Maildir", newfn);
 255
 256     if (argv[1]) {
 257         if ((pid = fork()) > 0) {
 258             return 0;
 259         } else if (pid == 0) {
 260             argv[0] = argv[1];
 261             argv[1] = newfn;
 262             execv(argv[0], argv);
 263             fail = "exec";
 264         } else {
 265             fail = "fork";
 266         }
 267
 268         /* If we got here fork or exec failed, so try to write an
 269          * error message where later mail processors can find it.  We
 270          * really can't do anything about it if this fails. */
 271         memcpy(newfn, "err", 3);
 272         mkdir("err", 0700);
 273         fd = open(newfn, O_WRONLY | O_EXCL | O_CREAT, 0644);
 274         errfile = fdopen(fd, "w");
 275         if (errfile) {
 276             fprintf(errfile, "%s:%d\n", fail, errno);
 277         }
 278     }
 279
 280     /* Always return 0 because deliver exits if it fails, and if it
 281      * succeeds we cannot return a failure code to the MTA. */
 282     return 0;
 283 }