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 /* 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     r = read(STDIN_FILENO, buf, 5);
 157     if (r != 5) {
 158         save_errno( unlink(fn) );
 159         err(MDELIVER_EXITCODE, "Failed read from stdin");
 160     }
 161
 162     if (strncmp(buf, "From ", 5) == 0) {
 163         while ((r = read(STDIN_FILENO, buf, 1)) > 0
 164                || (r == -1 && errno == EINTR)) {
 165             if (buf[0] == '\n') {
 166                 break;
 167             }
 168         }
 169
 170         if (r == -1) {
 171             save_errno( unlink(fn) );
 172             err(MDELIVER_EXITCODE, "Failed read from stdin");
 173         }
 174     } else {
 175         if (full_write(fd, buf, r) != r) {
 176             save_errno( unlink(fn) );
 177             err(MDELIVER_EXITCODE, "Failed write(%s)", fn);
 178         }
 179     }
 180 }
 181
 182 /* Copy the message from stdin to fd. */
 183 /* buf is passed only as an (early, evil) space optimization). */
 184 static void
 185 copy_message(int fd, char *buf, char *fn)
 186 {
 187     ssize_t r;
 188
 189     while ((r = read(STDIN_FILENO, buf, BUFSIZ)) > 0
 190            || (r == -1 && errno == EINTR)) {
 191         if (full_write(fd, buf, r) != r) {
 192             save_errno( unlink(fn) );
 193             err(MDELIVER_EXITCODE, "Failed write(%s)", fn);
 194         }
 195     }
 196
 197     if (r == -1) {
 198         save_errno( unlink(fn) );
 199         err(MDELIVER_EXITCODE, "Failed read from stdin");
 200     }
 201
 202     if (fsync(fd) < 0) {
 203         save_errno( unlink(fn) );
 204         err(MDELIVER_EXITCODE, "Failed fsync(%s)", fn);
 205     }
 206
 207     if (close(fd) < 0) {
 208         save_errno( unlink(fn) );
 209         err(MDELIVER_EXITCODE, "Failed close(%s)", fn);
 210     }
 211 }
 212
 213 static void
 214 deliver(char *maildir, char *newfn)
 215 {
 216     char fn[TMPNAMLEN];
 217     int fd;
 218     char buf[BUFSIZ];           /* Allocated here only as an (early,
 219                                  * evil) space optimization. */
 220
 221     if (chdir(maildir) != 0) {
 222         err(MDELIVER_EXITCODE, "Failed chdir(%s)", maildir);
 223     }
 224
 225     get_filename(fn);
 226
 227     fd = open(fn, O_WRONLY | O_EXCL | O_CREAT, 0600);
 228     if (fd < 0) {
 229         err(MDELIVER_EXITCODE, "Failed open(%s)", fn);
 230     }
 231
 232     /* From this point, we have a tmp file, so if someting fails we
 233      * must try to unlink it before bombing. */
 234
 235     strip_from(fd, buf, fn);
 236     copy_message(fd, buf, fn);
 237
 238     strcpy(newfn, fn);
 239     memcpy(newfn, "new", 3);
 240
 241     if (rename(fn, newfn) != 0) {
 242         save_errno( unlink(fn) );
 243         err(MDELIVER_EXITCODE, "Failed rename(%s, new)", fn);
 244     }
 245 }
 246
 247 int
 248 main(int argc, char *argv[])
 249 {
 250     char *home;
 251     char newfn[TMPNAMLEN];
 252     pid_t pid;
 253     FILE *errfile;
 254     char *fail;
 255     int olderrno;
 256     int fd;
 257
 258     if (argv[1] && argv[1][0] == '-' && argv[1][1] == 'v') {
 259         puts(rcsid);
 260         return 0;
 261     }
 262
 263     if (!(home = getenv("HOME"))) {
 264         err(MDELIVER_EXITCODE, "Failed getenv(HOME)");
 265     }
 266
 267     if (chdir(home) != 0) {
 268         err(MDELIVER_EXITCODE, "Failed chdir(HOME)");
 269     }
 270
 271     deliver("Maildir", newfn);
 272
 273     if (argv[1]) {
 274         if ((pid = fork()) > 0) {
 275             return 0;
 276         } else if (pid == 0) {
 277             argv[0] = argv[1];
 278             argv[1] = newfn;
 279             execv(argv[0], argv);
 280             fail = "exec";
 281         } else {
 282             fail = "fork";
 283         }
 284         olderrno = errno;
 285
 286         /* If we got here fork or exec failed, so try to write an
 287          * error message where later mail processors can find it.  We
 288          * really can't do anything about it if this fails. */
 289         memcpy(newfn, "err", 3);
 290         mkdir("err", 0700);
 291         fd = open(newfn, O_WRONLY | O_EXCL | O_CREAT, 0644);
 292         errfile = fdopen(fd, "w");
 293         if (errfile) {
 294             fprintf(errfile, "%s:%d\n", fail, olderrno);
 295         }
 296     }
 297
 298     /* Always return 0 because deliver exits if it fails, and if it
 299      * succeeds we cannot return a failure code to the MTA. */
 300     return 0;
 301 }