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
  14 #include <sys/types.h>
  15 #include <sys/stat.h>
  16
  17 #include <errno.h>
  18 #include <fcntl.h>
  19 #include <limits.h>
  20 #include <stdarg.h>
  21 #include <stdbool.h>
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <time.h>
  26 #include <unistd.h>
  27
  28 #ifndef EX_TEMPFAIL
  29 #ifdef QMAIL
  30 #define EX_TEMPFAIL 111
  31 #else
  32 #include <sysexits.h>
  33 #endif
  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 /* 4 for "tmp/", 2 for the two dots ('.'), HOST_NAME_MAX for the
  48  * hostname, two LEN_ULONGs for time and pid, and 1 for '\0', . */
  49 #define LEN_FILENAME 4 + 2 + HOST_NAME_MAX + LEN_ULONG + LEN_ULONG + 1
  50
  51 #define save_errno(op) {                                                \
  52     int olderrno = errno;                                               \
  53     op;                                                                 \
  54     errno = olderrno;                                                   \
  55 }
  56
  57 static char ident[] = "$Id$";
  58
  59 #define err(...) _err(true, __LINE__, __VA_ARGS__)
  60 #define errx(...) _err(false, __LINE__, __VA_ARGS__)
  61
  62 static void
  63 _err(bool want_strerror, int lineno, char *format, ...)
  64 {
  65     va_list ap;
  66
  67     fprintf(stderr, "mdeliver:%d:", lineno);
  68
  69     va_start(ap, format);
  70     vfprintf(stderr, format, ap);
  71     va_end(ap);
  72
  73     if (want_strerror) {
  74         perror("");
  75     } else {
  76         fputs("\n", stderr);
  77     }
  78
  79     exit(EX_TEMPFAIL);
  80 }
  81
  82 static void
  83 full_sleep(unsigned seconds)
  84 {
  85     while (seconds > 0) {
  86         seconds = sleep(seconds);
  87     }
  88 }
  89
  90 /* Write all of buf, even if write(2) is interrupted. */
  91 static ssize_t
  92 full_write(int fd, const char *buf, size_t nbytes)
  93 {
  94     ssize_t r, w = 0;
  95
  96     /* Loop until nbytes of buf have been written. */
  97     while (w < nbytes) {
  98         /* Keep trying until write succeeds without interruption. */
  99         do {
 100             r = write(fd, buf + w, nbytes - w);
 101         } while (r < 0 && errno == EINTR);
 102
 103         if (r < 0) {
 104             return r;
 105         }
 106
 107         w += r;
 108     }
 109
 110     return w;
 111 }
 112
 113 /* Find a filename for the message according to the algorithm
 114  * documented in the maildir(5) manual page from qmail
 115  * (http://www.qmail.org/qmail-manual-html/man5/maildir.html).
 116  */
 117 static void
 118 get_filename(char *fn)
 119 {
 120     pid_t pid;
 121     char host[HOST_NAME_MAX + 1];
 122     int try;
 123     time_t now;
 124     struct stat st;
 125
 126     pid = getpid();
 127
 128     if (gethostname(host, sizeof(host)) != 0) {
 129         err("gethostname");
 130     }
 131     /* http://www.opengroup.org/onlinepubs/009695399/functions/gethostname.html
 132      * "it is unspecified whether the returned name is null-terminated" */
 133     host[sizeof(host) - 1] = '\0';
 134
 135     for (try = 0; ; try++) {
 136         now = time(NULL);
 137         if (now == -1) {
 138             err("time");
 139         }
 140
 141         sprintf(fn, "tmp/%lu.%lu.%s",
 142                 (long unsigned)now, (long unsigned)pid, host);
 143
 144         if (stat(fn, &st) != 0) {
 145             if (errno == ENOENT) {
 146                 /* Every failure point in this program relies on errno
 147                  * describing what went wrong.  This is the one
 148                  * failure we *want*, so it is important to restore
 149                  * errno to 0 (success) before returning.
 150                  */
 151                 errno = 0;
 152                 break;
 153             }
 154         }
 155
 156         if (try == 2) {
 157             errx("Attempted filename exists.");
 158         }
 159
 160         full_sleep(2);
 161     }
 162 }
 163
 164 #ifndef QMAIL
 165 /* Strip the non-RFC2822-compliant 'From ' line some busted-ass
 166  * mailers (such as Postfix) add as the first line of input.  This bit
 167  * of historical gunk originated with Berkeley mbox files, which use
 168  * this line to indicate the beginning of a message.  Postfix should
 169  * only add such a line when it is acting as an MDA and delivering to
 170  * a Berkeley mbox; the data written to an external MDA should be the
 171  * raw RFC2822 message.  >sigh<
 172  */
 173 /* buf is passed only as an (early, evil) space optimization). */
 174 static void
 175 strip_from(int fd, char *buf, char *fn)
 176 {
 177     ssize_t r;
 178
 179     /* Yes, read(2) can be interrupted and read fewer bytes than
 180      * requested.  However, i'm only asking for five bytes here.  I
 181      * have tested this program extensively and it handles large
 182      * volumes of mail correctly every day on my systems.  This holds
 183      * up my original opinion that expecting to be able to get five
 184      * bytes safely is not an unreasonable demand.  If i can't get
 185      * five measly bytes, something is probably wrong, so bomb.
 186      */
 187     r = read(0, buf, 5);
 188     if (r != 5) {
 189         save_errno( unlink(fn) );
 190         err("read(0, 5)");
 191     }
 192
 193     if (strncmp(buf, "From ", 5) == 0) {
 194         while ((r = read(0, buf, 1)) > 0
 195                || (r == -1 && errno == EINTR)) {
 196             if (buf[0] == '\n') {
 197                 break;
 198             }
 199         }
 200
 201         if (r == -1) {
 202             save_errno( unlink(fn) );
 203             err("read(0, 1)");
 204         }
 205     } else {
 206         if (full_write(fd, buf, r) != r) {
 207             save_errno( unlink(fn) );
 208             err("write(%s)", fn);
 209         }
 210     }
 211 }
 212 #endif
 213
 214 /* Copy the file from INFD to OUTFD in blocks of BUFSIZE bytes (stored
 215  * in BUF).  BUF must point to a buffer of at least BUFSIZE bytes;
 216  * we're not dealing with null-terminated strings here.
 217  *
 218  * Note that OUTFD is closed before returning; this is necessary to
 219  * ensure the file was fully written on some filesystems, such as NFS.
 220  */
 221 static void
 222 copy_file(int infd, int outfd, char *buf, size_t bufsize, char *fn)
 223 {
 224     ssize_t r;
 225
 226     while ((r = read(infd, buf, bufsize)) > 0
 227            || (r == -1 && errno == EINTR)) {
 228         if (full_write(outfd, buf, r) != r) {
 229             save_errno( unlink(fn) );
 230             err("write(%s)", fn);
 231         }
 232     }
 233
 234     if (r == -1) {
 235         save_errno( unlink(fn) );
 236         err("read(%d, %d)", infd, bufsize);
 237     }
 238
 239     if (fsync(outfd) < 0) {
 240         save_errno( unlink(fn) );
 241         err("fsync(%s)", fn);
 242     }
 243
 244     if (close(outfd) < 0) {
 245         save_errno( unlink(fn) );
 246         err("close(%s)", fn);
 247     }
 248 }
 249
 250 static void
 251 deliver(char *maildir, char *sub, char *newfn)
 252 {
 253     char fn[LEN_FILENAME];
 254     int fd;
 255     char buf[BUFSIZ];           /* Allocated here only as an (early,
 256                                  * evil) space optimization. */
 257
 258     if (chdir(maildir) != 0) {
 259         err("chdir(%s)", maildir);
 260     }
 261
 262     get_filename(fn);
 263
 264     fd = open(fn, O_WRONLY | O_EXCL | O_CREAT, 0600);
 265     if (fd < 0) {
 266         err("open(%s)", fn);
 267     }
 268
 269     /* From this point, we have a tmp file, so if someting fails we
 270      * must try to unlink it before bombing. */
 271
 272 #ifdef QMAIL
 273     {
 274         char *buf;
 275         size_t len;
 276
 277         buf = getenv("RPLINE");
 278         len = strlen(buf);
 279         if (full_write(fd, buf, len) != len) {
 280             save_errno( unlink(fn) );
 281             err("write(%s)", fn);
 282         }
 283         buf = getenv("DTLINE");
 284         len = strlen(buf);
 285         if (full_write(fd, buf, len) != len) {
 286             save_errno( unlink(fn) );
 287             err("write(%s)", fn);
 288         }
 289     }
 290 #else
 291     strip_from(fd, buf, fn);
 292 #endif
 293
 294     copy_file(0, fd, buf, BUFSIZ, fn);
 295
 296     strcpy(newfn, fn);
 297     memcpy(newfn, sub, 3);
 298
 299     if (link(fn, newfn) != 0) {
 300         save_errno( unlink(fn) );
 301         err("link(%s, %s)", fn, newfn);
 302     }
 303     save_errno( unlink(fn) );
 304 }
 305
 306 /* Run a program to process the new message. */
 307 static void
 308 run_processor(char *home, char *newfn)
 309 {
 310     pid_t pid;
 311     char command[PATH_MAX];
 312     FILE *errfile;
 313     char *fail;
 314     int olderrno;
 315     int fd;
 316
 317     if ((pid = fork()) > 0) {
 318         return;
 319     } else if (pid == 0) {
 320         snprintf(command, sizeof(command), "%s/%s",
 321                  home, ".mdeliver-processor");
 322         execl(command, command, newfn, NULL);
 323         if (errno == ENOENT) {
 324             /* Not having a processor is not an error. */
 325             _exit(0);
 326         }
 327         fail = "exec";
 328     } else {
 329         fail = "fork";
 330     }
 331     olderrno = errno;
 332
 333     /* If we got here fork or exec failed, so try to write an error
 334      * message where later mail processors can find it.  We really
 335      * can't do anything about it if this fails. */
 336     memcpy(newfn, "err", 3);
 337     mkdir("err", 0700);
 338     fd = open(newfn, O_WRONLY | O_EXCL | O_CREAT, 0644);
 339     if (fd >= 0) {
 340         errfile = fdopen(fd, "w");
 341         if (errfile) {
 342             fprintf(errfile, "mdeliver:mdeliver.c:%d:%s: %s\n",
 343                     __LINE__, fail, strerror(olderrno));
 344             fflush(errfile);
 345         }
 346         fsync(fd);
 347         close(fd);
 348     }
 349
 350     if (fail[0] == 'e') {
 351         _exit(0);
 352     }
 353 }
 354
 355 int
 356 main(int argc, char *argv[])
 357 {
 358     char *home;
 359     char newfn[LEN_FILENAME];
 360     struct stat st;
 361
 362     if (argv[1] && argv[1][0] == '-' && argv[1][1] == 'v') {
 363         puts(ident);
 364         return 0;
 365     }
 366
 367     if ((home = getenv("HOME")) == NULL) {
 368         errx("HOME is not set.");
 369     }
 370
 371     if (chdir(home) != 0) {
 372         err("chdir(%s)", home);
 373     }
 374
 375     if (stat(".mdeliver-processor", &st) == 0) {
 376         deliver("Maildir", "mdp", newfn);
 377         run_processor(home, newfn);
 378     } else {
 379         deliver("Maildir", "new", newfn);
 380     }
 381
 382     return 0;
 383 }