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