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 static void
  73 deliver(char *maildir, char *newfn)
  74 {
  75     char fn[TMPNAMLEN], host[HOST_NAME_MAX + 1];
  76     char *buildfn;              /* used to build up the fn */
  77     time_t now;
  78     struct tm *t;
  79     pid_t pid;
  80     struct stat statbuf;
  81     int try;
  82     int fd, r;
  83     char buf[BUFSIZ];
  84
  85     if (chdir(maildir) != 0) {
  86         err(EX_TEMPFAIL, "Failed chdir(%s)", maildir);
  87     }
  88
  89     pid = getpid();
  90     gethostname(host, sizeof(host));
  91
  92     for (try = 0; ; try++) {
  93         now = time(NULL);
  94         t = gmtime(&now);
  95
  96         buildfn = fn + sprintf(fn, "tmp/");
  97         buildfn += strftime(buildfn, LEN_ULONG + 1, "%s.", t);
  98         buildfn += snprintf(buildfn, LEN_ULONG + 1, "%d.", pid);
  99         buildfn += sprintf(buildfn, "%s", host);
 100
 101         if (stat(fn, &statbuf) != 0) {
 102             if (errno == ENOENT) {
 103                 break;
 104             }
 105         }
 106
 107         if (try == 2) {
 108             errx(EX_TEMPFAIL, "Attempted filename exists.");
 109         }
 110
 111         sleep(2);
 112     }
 113
 114     fd = open(fn, O_WRONLY | O_EXCL | O_CREAT, 0600);
 115     if (fd < 0) {
 116         err(EX_TEMPFAIL, "Failed open(%s)", fn);
 117     }
 118
 119     /* From this point, we have a tmp file, so if someting fails we
 120      * must try to unlink it before bombing. */
 121
 122     {
 123         r = read(STDIN_FILENO, buf, 5);
 124         if (r != 5) {
 125             unlink(fn);
 126             err(EX_TEMPFAIL, "Failed read from stdin");
 127         }
 128
 129         if (strncmp(buf, "From ", 5)) {
 130             while ((r = read(STDIN_FILENO, buf, 1)) > 0
 131                    || (r == -1 && errno == EINTR)) {
 132                 if (buf[0] == '\n') {
 133                     break;
 134                 }
 135             }
 136
 137             if (r == -1) {
 138                 unlink(fn);
 139                 err(EX_TEMPFAIL, "Failed read from stdin");
 140             }
 141         } else {
 142             if (full_write(fd, buf, r) != r) {
 143                 unlink(fn);
 144                 err(EX_TEMPFAIL, "Failed write(%s)", fn);
 145             }
 146         }
 147     }
 148
 149     while ((r = read(STDIN_FILENO, buf, BUFSIZ)) > 0
 150            || (r == -1 && errno == EINTR)) {
 151         if (full_write(fd, buf, r) != r) {
 152             unlink(fn);
 153             err(EX_TEMPFAIL, "Failed write(%s)", fn);
 154         }
 155     }
 156
 157     if (r == -1) {
 158         unlink(fn);
 159         err(EX_TEMPFAIL, "Failed read from stdin");
 160     }
 161
 162     if (fsync(fd) < 0) {
 163         unlink(fn);
 164         err(EX_TEMPFAIL, "Failed fsync(%s)", fn);
 165     }
 166     if (close(fd) < 0) {
 167         unlink(fn);
 168         err(EX_TEMPFAIL, "Failed close(%s)", fn);
 169     }
 170
 171     strcpy(newfn, fn);
 172     memcpy(newfn, "new", 3);
 173
 174     if (rename(fn, newfn) != 0) {
 175         unlink(fn);
 176         err(EX_TEMPFAIL, "Failed rename(%s, new)", fn);
 177     }
 178 }
 179
 180 int
 181 main(int argc, char *argv[])
 182 {
 183     char *home;
 184     char newfn[TMPNAMLEN];
 185     pid_t pid;
 186     FILE *errfile;
 187     char *fail;
 188     int fd;
 189
 190     if (argv[1] && argv[1][0] == '-' && argv[1][1] == 'v') {
 191         puts(rcsid);
 192         return 0;
 193     }
 194
 195     if (!(home = getenv("HOME"))) {
 196         err(EX_TEMPFAIL, "Failed getenv(HOME)");
 197     }
 198
 199     if (chdir(home) != 0) {
 200         err(EX_TEMPFAIL, "Failed chdir(HOME)");
 201     }
 202
 203     deliver("Maildir", newfn);
 204
 205     if (argv[1]) {
 206         if ((pid = fork()) > 0) {
 207             return 0;
 208         } else if (pid == 0) {
 209             argv[0] = argv[1];
 210             argv[1] = newfn;
 211             execv(argv[0], argv);
 212             fail = "exec";
 213         } else {
 214             fail = "fork";
 215         }
 216
 217         /* If we got here fork or exec failed, so try to write an
 218          * error message where later mail processors can find it.  We
 219          * really can't do anything about it if this fails. */
 220         memcpy(newfn, "err", 3);
 221         mkdir("err", 0700);
 222         fd = open(newfn, O_WRONLY | O_EXCL | O_CREAT, 0644);
 223         errfile = fdopen(fd, "w");
 224         if (errfile) {
 225             fprintf(errfile, "%s:%d\n", fail, errno);
 226         }
 227     }
 228
 229     /* Always return 0 because deliver exits if it fails, and if it
 230      * succeeds we cannot return a failure code to the MTA. */
 231     return 0;
 232 }