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 get_filename(char *fn)
  74 {
  75     pid_t pid;
  76     char host[HOST_NAME_MAX + 1];
  77     int try;
  78     time_t now;
  79     struct tm *t;
  80     char *buildfn;              /* used to build up the fn */
  81     struct stat statbuf;
  82
  83     pid = getpid();
  84     gethostname(host, sizeof(host));
  85
  86     for (try = 0; ; try++) {
  87         now = time(NULL);
  88         t = gmtime(&now);
  89
  90         buildfn = fn + sprintf(fn, "tmp/");
  91         buildfn += strftime(buildfn, LEN_ULONG + 1, "%s.", t);
  92         buildfn += snprintf(buildfn, LEN_ULONG + 1, "%d.", pid);
  93         buildfn += sprintf(buildfn, "%s", host);
  94
  95         if (stat(fn, &statbuf) != 0) {
  96             if (errno == ENOENT) {
  97                 break;
  98             }
  99         }
 100
 101         if (try == 2) {
 102             errx(EX_TEMPFAIL, "Attempted filename exists.");
 103         }
 104
 105         sleep(2);
 106     }
 107 }
 108
 109 /* buf is passed only as an (early, evil) space optimization). */
 110 static void
 111 strip_from(int fd, char *buf, char *fn)
 112 {
 113     ssize_t r;
 114
 115     r = read(STDIN_FILENO, buf, 5);
 116     if (r != 5) {
 117         unlink(fn);
 118         err(EX_TEMPFAIL, "Failed read from stdin");
 119     }
 120
 121     if (strncmp(buf, "From ", 5)) {
 122         while ((r = read(STDIN_FILENO, buf, 1)) > 0
 123                || (r == -1 && errno == EINTR)) {
 124             if (buf[0] == '\n') {
 125                 break;
 126             }
 127         }
 128
 129         if (r == -1) {
 130             unlink(fn);
 131             err(EX_TEMPFAIL, "Failed read from stdin");
 132         }
 133     } else {
 134         if (full_write(fd, buf, r) != r) {
 135             unlink(fn);
 136             err(EX_TEMPFAIL, "Failed write(%s)", fn);
 137         }
 138     }
 139 }
 140
 141 /* buf is passed only as an (early, evil) space optimization). */
 142 static void
 143 copy_message(int fd, char *buf, char *fn)
 144 {
 145     ssize_t r;
 146
 147     while ((r = read(STDIN_FILENO, buf, BUFSIZ)) > 0
 148            || (r == -1 && errno == EINTR)) {
 149         if (full_write(fd, buf, r) != r) {
 150             unlink(fn);
 151             err(EX_TEMPFAIL, "Failed write(%s)", fn);
 152         }
 153     }
 154
 155     if (r == -1) {
 156         unlink(fn);
 157         err(EX_TEMPFAIL, "Failed read from stdin");
 158     }
 159
 160     if (fsync(fd) < 0) {
 161         unlink(fn);
 162         err(EX_TEMPFAIL, "Failed fsync(%s)", fn);
 163     }
 164
 165     if (close(fd) < 0) {
 166         unlink(fn);
 167         err(EX_TEMPFAIL, "Failed close(%s)", fn);
 168     }
 169 }
 170
 171 static void
 172 deliver(char *maildir, char *newfn)
 173 {
 174     char fn[TMPNAMLEN];
 175     int fd;
 176     char buf[BUFSIZ];           /* Allocated here only as an (early,
 177                                  * evil) space optimization. */
 178
 179     if (chdir(maildir) != 0) {
 180         err(EX_TEMPFAIL, "Failed chdir(%s)", maildir);
 181     }
 182
 183     get_filename(fn);
 184
 185     fd = open(fn, O_WRONLY | O_EXCL | O_CREAT, 0600);
 186     if (fd < 0) {
 187         err(EX_TEMPFAIL, "Failed open(%s)", fn);
 188     }
 189
 190     /* From this point, we have a tmp file, so if someting fails we
 191      * must try to unlink it before bombing. */
 192
 193     strip_from(fd, buf, fn);
 194     copy_message(fd, buf, fn);
 195
 196     strcpy(newfn, fn);
 197     memcpy(newfn, "new", 3);
 198
 199     if (rename(fn, newfn) != 0) {
 200         unlink(fn);
 201         err(EX_TEMPFAIL, "Failed rename(%s, new)", fn);
 202     }
 203 }
 204
 205 int
 206 main(int argc, char *argv[])
 207 {
 208     char *home;
 209     char newfn[TMPNAMLEN];
 210     pid_t pid;
 211     FILE *errfile;
 212     char *fail;
 213     int fd;
 214
 215     if (argv[1] && argv[1][0] == '-' && argv[1][1] == 'v') {
 216         puts(rcsid);
 217         return 0;
 218     }
 219
 220     if (!(home = getenv("HOME"))) {
 221         err(EX_TEMPFAIL, "Failed getenv(HOME)");
 222     }
 223
 224     if (chdir(home) != 0) {
 225         err(EX_TEMPFAIL, "Failed chdir(HOME)");
 226     }
 227
 228     deliver("Maildir", newfn);
 229
 230     if (argv[1]) {
 231         if ((pid = fork()) > 0) {
 232             return 0;
 233         } else if (pid == 0) {
 234             argv[0] = argv[1];
 235             argv[1] = newfn;
 236             execv(argv[0], argv);
 237             fail = "exec";
 238         } else {
 239             fail = "fork";
 240         }
 241
 242         /* If we got here fork or exec failed, so try to write an
 243          * error message where later mail processors can find it.  We
 244          * really can't do anything about it if this fails. */
 245         memcpy(newfn, "err", 3);
 246         mkdir("err", 0700);
 247         fd = open(newfn, O_WRONLY | O_EXCL | O_CREAT, 0644);
 248         errfile = fdopen(fd, "w");
 249         if (errfile) {
 250             fprintf(errfile, "%s:%d\n", fail, errno);
 251         }
 252     }
 253
 254     /* Always return 0 because deliver exits if it fails, and if it
 255      * succeeds we cannot return a failure code to the MTA. */
 256     return 0;
 257 }