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 rcsid[] = "$Id$";
  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         t = gmtime(&now);
 113         if (!t) {
 114             err(MDELIVER_EXITCODE, "Failed gmtime()");
 115         }
 116
 117         buildfn = fn + sprintf(fn, "tmp/");
 118         buildfn += strftime(buildfn, LEN_ULONG + 1, "%s.", t);
 119         buildfn += snprintf(buildfn, LEN_ULONG + 1, "%d.", pid);
 120         buildfn += sprintf(buildfn, "%s", host);
 121
 122         if (stat(fn, &statbuf) != 0) {
 123             if (errno == ENOENT) {
 124                 /* Every failure point in this program relies on errno
 125                  * describing what went wrong.  This is the one
 126                  * failure we *want*, so it is important to restore
 127                  * errno to 0 (success) before returning.
 128                  */
 129                 errno = 0;
 130                 break;
 131             }
 132         }
 133
 134         if (try == 2) {
 135             errx(MDELIVER_EXITCODE, "Attempted filename exists.");
 136         }
 137
 138         sleep(2);
 139     }
 140 }
 141
 142 /* Strip the non-RFC2822-compliant 'From ' line some busted-ass
 143  * mailers (such as Postfix) add as the first line of input.  This bit
 144  * of historical gunk originated with Berkeley mbox files, which use
 145  * this line to indicate the beginning of a message.  Postfix should
 146  * only add such a line when it is acting as an MDA and delivering to
 147  * a Berkeley mbox; the data written to an external MDA should be the
 148  * raw RFC2822 message.  >sigh<
 149  */
 150 /* buf is passed only as an (early, evil) space optimization). */
 151 static void
 152 strip_from(int fd, char *buf, char *fn)
 153 {
 154     ssize_t r;
 155
 156     /* Yes, read(2) can be interrupted and read fewer bytes than
 157      * requested.  However, i'm only asking for five bytes here.  I
 158      * have tested this program extensively and it handles large
 159      * volumes of mail correctly every day on my systems.  This holds
 160      * up my original opinion that expecting to be able to get five
 161      * bytes safely is not an unreasonable demand.  If i can't get
 162      * five measly bytes, something is probably wrong, so bomb.
 163      */
 164     r = read(STDIN_FILENO, buf, 5);
 165     if (r != 5) {
 166         save_errno( unlink(fn) );
 167         err(MDELIVER_EXITCODE, "Failed read from stdin");
 168     }
 169
 170     if (strncmp(buf, "From ", 5) == 0) {
 171         while ((r = read(STDIN_FILENO, buf, 1)) > 0
 172                || (r == -1 && errno == EINTR)) {
 173             if (buf[0] == '\n') {
 174                 break;
 175             }
 176         }
 177
 178         if (r == -1) {
 179             save_errno( unlink(fn) );
 180             err(MDELIVER_EXITCODE, "Failed read from stdin");
 181         }
 182     } else {
 183         if (full_write(fd, buf, r) != r) {
 184             save_errno( unlink(fn) );
 185             err(MDELIVER_EXITCODE, "Failed write(%s)", fn);
 186         }
 187     }
 188 }
 189
 190 /* Copy the file from INFD to OUTFD in blocks of BUFSIZE bytes (stored
 191  * in BUF).  BUF must point to a buffer of at least BUFSIZE bytes;
 192  * we're not dealing with null-terminated strings here.
 193  *
 194  * Note that OUTFD is closed before returning; this is necessary to
 195  * ensure the file was fully written on some filesystems, such as NFS.
 196  */
 197 static void
 198 copy_file(int infd, int outfd, char *buf, size_t bufsize, char *fn)
 199 {
 200     ssize_t r;
 201
 202     while ((r = read(infd, buf, bufsize)) > 0
 203            || (r == -1 && errno == EINTR)) {
 204         if (full_write(outfd, buf, r) != r) {
 205             save_errno( unlink(fn) );
 206             err(MDELIVER_EXITCODE, "Failed write(%s)", fn);
 207         }
 208     }
 209
 210     if (r == -1) {
 211         save_errno( unlink(fn) );
 212         err(MDELIVER_EXITCODE, "Failed read");
 213     }
 214
 215     if (fsync(outfd) < 0) {
 216         save_errno( unlink(fn) );
 217         err(MDELIVER_EXITCODE, "Failed fsync(%s)", fn);
 218     }
 219
 220     if (close(outfd) < 0) {
 221         save_errno( unlink(fn) );
 222         err(MDELIVER_EXITCODE, "Failed close(%s)", fn);
 223     }
 224 }
 225
 226 static void
 227 deliver(char *maildir, char *newfn)
 228 {
 229     char fn[TMPNAMLEN];
 230     int fd, tmpfd;
 231     char buf[BUFSIZ];           /* Allocated here only as an (early,
 232                                  * evil) space optimization. */
 233
 234     if (chdir(maildir) != 0) {
 235         err(MDELIVER_EXITCODE, "Failed chdir(%s)", maildir);
 236     }
 237
 238     get_filename(fn);
 239
 240     fd = open(fn, O_WRONLY | O_EXCL | O_CREAT, 0600);
 241     if (fd < 0) {
 242         err(MDELIVER_EXITCODE, "Failed open(%s)", fn);
 243     }
 244
 245     /* From this point, we have a tmp file, so if someting fails we
 246      * must try to unlink it before bombing. */
 247
 248     strip_from(fd, buf, fn);
 249     copy_file(STDIN_FILENO, fd, buf, BUFSIZ, fn);
 250
 251     strcpy(newfn, fn);
 252     memcpy(newfn, "new", 3);
 253
 254     tmpfd = open(newfn, O_WRONLY | O_EXCL | O_CREAT, 0600);
 255     if (tmpfd < 0) {
 256         /* XXX: what error message to use? */
 257         err(MDELIVER_EXITCODE, "Failed open(%s)", newfn);
 258     }
 259     close(tmpfd);
 260
 261     if (rename(fn, newfn) != 0) {
 262         save_errno( unlink(newfn) );
 263         save_errno( unlink(fn) );
 264         err(MDELIVER_EXITCODE, "Failed rename(%s, new)", fn);
 265     }
 266 }
 267
 268 /* Run a program to process the new message. */
 269 static void
 270 run_processor(char *home, char *newfn)
 271 {
 272     pid_t pid;
 273     char command[PATH_MAX];
 274     FILE *errfile;
 275     char *fail;
 276     int olderrno;
 277     int fd;
 278
 279     if ((pid = fork()) > 0) {
 280         return;
 281     } else if (pid == 0) {
 282         snprintf(command, PATH_MAX, "%s/%s", home, ".mdeliver-processor");
 283         execl(command, command, newfn, NULL);
 284         if (errno == ENOENT) {
 285             /* Not having a processor is not an error. */
 286             return;
 287         }
 288         fail = "exec";
 289     } else {
 290         fail = "fork";
 291     }
 292     olderrno = errno;
 293
 294     /* If we got here fork or exec failed, so try to write an error
 295      * message where later mail processors can find it.  We really
 296      * can't do anything about it if this fails. */
 297     memcpy(newfn, "err", 3);
 298     mkdir("err", 0700);
 299     fd = open(newfn, O_WRONLY | O_EXCL | O_CREAT, 0644);
 300     if (fd >= 0) {
 301         errfile = fdopen(fd, "w");
 302         if (errfile) {
 303             fprintf(errfile, "%s:%d\n", fail, olderrno);
 304             fflush(errfile);
 305         }
 306         fsync(fd);
 307         close(fd);
 308     }
 309 }
 310
 311 int
 312 main(int argc, char *argv[])
 313 {
 314     char *home;
 315     char newfn[TMPNAMLEN];
 316
 317     if (argv[1] && argv[1][0] == '-' && argv[1][1] == 'v') {
 318         puts(rcsid);
 319         return 0;
 320     }
 321
 322     if (!(home = getenv("HOME"))) {
 323         err(MDELIVER_EXITCODE, "Failed getenv(HOME)");
 324     }
 325
 326     if (chdir(home) != 0) {
 327         err(MDELIVER_EXITCODE, "Failed chdir(HOME)");
 328     }
 329
 330     deliver("Maildir", newfn);
 331
 332     run_processor(home, newfn);
 333
 334     /* Always return 0 because deliver exits if it fails, and if it
 335      * succeeds we cannot return a failure code to the MTA. */
 336     return 0;
 337 }