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/", 2 for the two dots ('.'), HOST_NAME_MAX
  48  * for the hostname, and two LEN_ULONGs for time and pid. */
  49 #define TMPNAMLEN 1 + 4 + 2 + HOST_NAME_MAX + LEN_ULONG + LEN_ULONG
  50
  51 /* Use this macro to perform some operation and saving the value errno
  52  * had before that operation.
  53  */
  54 #define save_errno(op) {                                                \
  55     int olderrno = errno;                                               \
  56     op;                                                                 \
  57     errno = olderrno;                                                   \
  58 }
  59
  60 static char ident[] = "$Id$";
  61
  62 /* Write all of buf, even if write(2) is interrupted. */
  63 static ssize_t
  64 full_write(int fd, const char *buf, size_t nbytes)
  65 {
  66     ssize_t r, w = 0;
  67
  68     /* Loop until nbytes of buf have been written. */
  69     while (w < nbytes) {
  70         /* Keep trying until write succeeds without interruption. */
  71         do {
  72             r = write(fd, buf + w, nbytes - w);
  73         } while (r < 0 && errno == EINTR);
  74
  75         if (r < 0) {
  76             return r;
  77         }
  78
  79         w += r;
  80     }
  81
  82     return w;
  83 }
  84
  85 /* Find a filename for the message according to the algorithm
  86  * documented in the maildir(5) manual page from qmail
  87  * (http://www.qmail.org/qmail-manual-html/man5/maildir.html).
  88  */
  89 static void
  90 get_filename(char *fn)
  91 {
  92     pid_t pid;
  93     char host[HOST_NAME_MAX + 1];
  94     int try;
  95     time_t now;
  96     struct tm t;
  97     char *buildfn;              /* used to build up the fn */
  98     struct stat statbuf;
  99
 100     pid = getpid();
 101
 102     if (gethostname(host, sizeof(host)) != 0) {
 103         err(MDELIVER_EXITCODE, "Failed gethostname");
 104     }
 105
 106     for (try = 0; ; try++) {
 107         now = time(NULL);
 108         if (now == -1) {
 109             err(MDELIVER_EXITCODE, "Failed time()");
 110         }
 111
 112         if (gmtime_r(&now, &t) == NULL) {
 113             err(MDELIVER_EXITCODE, "Failed gmtime_r()");
 114         }
 115
 116         buildfn = fn + sprintf(fn, "tmp/");
 117         buildfn += strftime(buildfn, LEN_ULONG + 1, "%s.", &t);
 118         buildfn += snprintf(buildfn, LEN_ULONG + 1, "%d.", pid);
 119         buildfn += sprintf(buildfn, "%s", host);
 120
 121         if (stat(fn, &statbuf) != 0) {
 122             if (errno == ENOENT) {
 123                 /* Every failure point in this program relies on errno
 124                  * describing what went wrong.  This is the one
 125                  * failure we *want*, so it is important to restore
 126                  * errno to 0 (success) before returning.
 127                  */
 128                 errno = 0;
 129                 break;
 130             }
 131         }
 132
 133         if (try == 2) {
 134             errx(MDELIVER_EXITCODE, "Attempted filename exists.");
 135         }
 136
 137         sleep(2);
 138     }
 139 }
 140
 141 /* Strip the non-RFC2822-compliant 'From ' line some busted-ass
 142  * mailers (such as Postfix) add as the first line of input.  This bit
 143  * of historical gunk originated with Berkeley mbox files, which use
 144  * this line to indicate the beginning of a message.  Postfix should
 145  * only add such a line when it is acting as an MDA and delivering to
 146  * a Berkeley mbox; the data written to an external MDA should be the
 147  * raw RFC2822 message.  >sigh<
 148  */
 149 /* buf is passed only as an (early, evil) space optimization). */
 150 static void
 151 strip_from(int fd, char *buf, char *fn)
 152 {
 153     ssize_t r;
 154
 155     /* Yes, read(2) can be interrupted and read fewer bytes than
 156      * requested.  However, i'm only asking for five bytes here.  I
 157      * have tested this program extensively and it handles large
 158      * volumes of mail correctly every day on my systems.  This holds
 159      * up my original opinion that expecting to be able to get five
 160      * bytes safely is not an unreasonable demand.  If i can't get
 161      * five measly bytes, something is probably wrong, so bomb.
 162      */
 163     r = read(STDIN_FILENO, buf, 5);
 164     if (r != 5) {
 165         save_errno( unlink(fn) );
 166         err(MDELIVER_EXITCODE, "Failed read from stdin");
 167     }
 168
 169     if (strncmp(buf, "From ", 5) == 0) {
 170         while ((r = read(STDIN_FILENO, buf, 1)) > 0
 171                || (r == -1 && errno == EINTR)) {
 172             if (buf[0] == '\n') {
 173                 break;
 174             }
 175         }
 176
 177         if (r == -1) {
 178             save_errno( unlink(fn) );
 179             err(MDELIVER_EXITCODE, "Failed read from stdin");
 180         }
 181     } else {
 182         if (full_write(fd, buf, r) != r) {
 183             save_errno( unlink(fn) );
 184             err(MDELIVER_EXITCODE, "Failed write(%s)", fn);
 185         }
 186     }
 187 }
 188
 189 /* Copy the file from INFD to OUTFD in blocks of BUFSIZE bytes (stored
 190  * in BUF).  BUF must point to a buffer of at least BUFSIZE bytes;
 191  * we're not dealing with null-terminated strings here.
 192  *
 193  * Note that OUTFD is closed before returning; this is necessary to
 194  * ensure the file was fully written on some filesystems, such as NFS.
 195  */
 196 static void
 197 copy_file(int infd, int outfd, char *buf, size_t bufsize, char *fn)
 198 {
 199     ssize_t r;
 200
 201     while ((r = read(infd, buf, bufsize)) > 0
 202            || (r == -1 && errno == EINTR)) {
 203         if (full_write(outfd, buf, r) != r) {
 204             save_errno( unlink(fn) );
 205             err(MDELIVER_EXITCODE, "Failed write(%s)", fn);
 206         }
 207     }
 208
 209     if (r == -1) {
 210         save_errno( unlink(fn) );
 211         err(MDELIVER_EXITCODE, "Failed read");
 212     }
 213
 214     if (fsync(outfd) < 0) {
 215         save_errno( unlink(fn) );
 216         err(MDELIVER_EXITCODE, "Failed fsync(%s)", fn);
 217     }
 218
 219     if (close(outfd) < 0) {
 220         save_errno( unlink(fn) );
 221         err(MDELIVER_EXITCODE, "Failed close(%s)", fn);
 222     }
 223 }
 224
 225 static void
 226 deliver(char *maildir, char *newfn)
 227 {
 228     char fn[TMPNAMLEN];
 229     int fd, tmpfd;
 230     char buf[BUFSIZ];           /* Allocated here only as an (early,
 231                                  * evil) space optimization. */
 232
 233     if (chdir(maildir) != 0) {
 234         err(MDELIVER_EXITCODE, "Failed chdir(%s)", maildir);
 235     }
 236
 237     get_filename(fn);
 238
 239     fd = open(fn, O_WRONLY | O_EXCL | O_CREAT, 0600);
 240     if (fd < 0) {
 241         err(MDELIVER_EXITCODE, "Failed open(%s)", fn);
 242     }
 243
 244     /* From this point, we have a tmp file, so if someting fails we
 245      * must try to unlink it before bombing. */
 246
 247     strip_from(fd, buf, fn);
 248     copy_file(STDIN_FILENO, fd, buf, BUFSIZ, fn);
 249
 250     strcpy(newfn, fn);
 251     memcpy(newfn, "new", 3);
 252
 253     tmpfd = open(newfn, O_WRONLY | O_EXCL | O_CREAT, 0600);
 254     if (tmpfd < 0) {
 255         /* XXX: what error message to use? */
 256         err(MDELIVER_EXITCODE, "Failed open(%s)", newfn);
 257     }
 258     close(tmpfd);
 259
 260     if (rename(fn, newfn) != 0) {
 261         save_errno( unlink(newfn) );
 262         save_errno( unlink(fn) );
 263         err(MDELIVER_EXITCODE, "Failed rename(%s, new)", fn);
 264     }
 265 }
 266
 267 /* Run a program to process the new message. */
 268 static void
 269 run_processor(char *home, char *newfn)
 270 {
 271     pid_t pid;
 272     char command[PATH_MAX];
 273     FILE *errfile;
 274     char *fail;
 275     int olderrno;
 276     int fd;
 277
 278     if ((pid = vfork()) > 0) {
 279         return;
 280     } else if (pid == 0) {
 281         snprintf(command, PATH_MAX, "%s/%s", home, ".mdeliver-processor");
 282         execl(command, command, newfn, NULL);
 283         if (errno == ENOENT) {
 284             /* Not having a processor is not an error. */
 285             _exit(0);
 286         }
 287         fail = "exec";
 288     } else {
 289         fail = "vfork";
 290     }
 291     olderrno = errno;
 292
 293     /* If we got here fork or exec failed, so try to write an error
 294      * message where later mail processors can find it.  We really
 295      * can't do anything about it if this fails. */
 296     memcpy(newfn, "err", 3);
 297     mkdir("err", 0700);
 298     fd = open(newfn, O_WRONLY | O_EXCL | O_CREAT, 0644);
 299     if (fd >= 0) {
 300         errfile = fdopen(fd, "w");
 301         if (errfile) {
 302             fprintf(errfile, "%s:%d\n", fail, olderrno);
 303             fflush(errfile);
 304         }
 305         fsync(fd);
 306         close(fd);
 307     }
 308
 309     _exit(0);
 310 }
 311
 312 int
 313 main(int argc, char *argv[])
 314 {
 315     char *home;
 316     char newfn[TMPNAMLEN];
 317
 318     if (argv[1] && argv[1][0] == '-' && argv[1][1] == 'v') {
 319         puts(ident);
 320         return 0;
 321     }
 322
 323     if (!(home = getenv("HOME"))) {
 324         err(MDELIVER_EXITCODE, "Failed getenv(HOME)");
 325     }
 326
 327     if (chdir(home) != 0) {
 328         err(MDELIVER_EXITCODE, "Failed chdir(HOME)");
 329     }
 330
 331     deliver("Maildir", newfn);
 332
 333     run_processor(home, newfn);
 334
 335     /* Always return 0 because deliver exits if it fails, and if it
 336      * succeeds we cannot return a failure code to the MTA. */
 337     return 0;
 338 }