1 /* smtp-dummy - Dummy SMTP server that delivers mail to the given file
3 * Copyright © 2010 Carl Worth
5 * This program is free software: you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation, either version 3 of the License, or
8 * (at your option) any later version.
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
15 * You should have received a copy of the GNU General Public License
16 * along with this program. If not, see https://www.gnu.org/licenses/ .
18 * Authors: Carl Worth <cworth@cworth.org>
21 /* This (non-compliant) SMTP server listens on localhost, port 25025
22 * and delivers a mail received to the given filename, (specified as a
23 * command-line argument). It exists after the first client connection
26 * It implements very little of the SMTP protocol, even less than
27 * specified as the minimum implementation in the SMTP RFC, (not
28 * implementing RSET, NOOP, nor VRFY). And it doesn't do any
29 * error-checking on the input.
31 * That is to say, if you use this program, you will very likely find
32 * cases where it doesn't do everything your SMTP client expects. You
40 #include <sys/types.h>
41 #include <sys/socket.h>
42 #include <netinet/in.h>
46 #define STRNCMP_LITERAL(var, literal) \
47 strncmp ((var), (literal), sizeof (literal) - 1)
50 receive_data_to_file (FILE *peer, FILE *output)
56 while ((line_len = getline (&line, &line_size, peer)) != -1) {
57 if (STRNCMP_LITERAL (line, ".\r\n") == 0)
61 if (line[line_len - 1] == '\n' && line[line_len - 2] == '\r') {
62 line[line_len - 2] = '\n';
63 line[line_len - 1] = '\0';
65 fprintf (output, "%s",
66 line[0] == '.' ? line + 1 : line);
73 process_command (FILE *peer, FILE *output, const char *command)
75 if (STRNCMP_LITERAL (command, "EHLO ") == 0) {
76 fprintf (peer, "502 not implemented\r\n");
78 } else if (STRNCMP_LITERAL (command, "HELO ") == 0) {
79 fprintf (peer, "250 localhost\r\n");
81 } else if (STRNCMP_LITERAL (command, "MAIL FROM:") == 0 ||
82 STRNCMP_LITERAL (command, "RCPT TO:") == 0) {
83 fprintf (peer, "250 OK\r\n");
85 } else if (STRNCMP_LITERAL (command, "DATA") == 0) {
86 fprintf (peer, "354 End data with <CR><LF>.<CR><LF>\r\n");
88 receive_data_to_file (peer, output);
89 fprintf (peer, "250 OK\r\n");
91 } else if (STRNCMP_LITERAL (command, "QUIT") == 0) {
92 fprintf (peer, "221 BYE\r\n");
96 fprintf (stderr, "Unknown command: %s\n", command);
102 do_smtp_to_file (FILE *peer, FILE *output)
108 fprintf (peer, "220 localhost smtp-dummy\r\n");
111 while ((line_len = getline (&line, &line_size, peer)) != -1) {
112 if (process_command (peer, output, line))
120 main (int argc, char *argv[])
122 const char *progname;
123 char *output_filename;
124 FILE *peer_file = NULL, *output = NULL;
125 int sock = -1, peer, err;
126 struct sockaddr_in addr, peer_addr;
127 struct hostent *hostinfo;
128 socklen_t peer_addr_len;
137 for (; argc >= 2; argc--, argv++) {
138 if (argv[1][0] != '-')
140 if (strcmp (argv[1], "--") == 0) {
145 if (strcmp (argv[1], "--background") == 0) {
149 fprintf (stderr, "%s: unregognized option '%s'\n",
156 "Usage: %s [--background] <output-file>\n", progname);
160 output_filename = argv[1];
161 output = fopen (output_filename, "w");
162 if (output == NULL) {
163 fprintf (stderr, "Failed to open %s for writing: %s\n",
164 output_filename, strerror (errno));
169 sock = socket (AF_INET, SOCK_STREAM, 0);
171 fprintf (stderr, "Error: socket() failed: %s\n",
178 err = setsockopt (sock, SOL_SOCKET, SO_REUSEADDR, &reuse, sizeof (reuse));
180 fprintf (stderr, "Error: setsockopt() failed: %s\n",
186 hostinfo = gethostbyname ("localhost");
187 if (hostinfo == NULL) {
188 fprintf (stderr, "Unknown host: localhost\n");
193 memset (&addr, 0, sizeof (addr));
194 addr.sin_family = AF_INET;
196 addr.sin_addr = *(struct in_addr *) hostinfo->h_addr;
197 err = bind (sock, (struct sockaddr *) &addr, sizeof (addr));
199 fprintf (stderr, "Error: bind() failed: %s\n",
206 addrlen = sizeof (addr);
207 err = getsockname (sock, (struct sockaddr *) &addr, &addrlen);
209 fprintf (stderr, "Error: getsockname() failed: %s\n",
216 printf ("smtp_dummy_port='%d'\n", ntohs (addr.sin_port));
218 err = listen (sock, 1);
220 fprintf (stderr, "Error: listen() failed: %s\n",
230 printf ("smtp_dummy_pid='%d'\n", pid);
237 fprintf (stderr, "Error: fork() failed: %s\n",
243 /* Reached if pid == 0 (the child process). */
244 /* Close stdout so that the one interested in pid value will
246 close (STDOUT_FILENO);
247 /* dup2() will re-reserve fd of stdout (1) (opportunistically),
248 * in case fd of stderr (2) is open. If that was not open we
249 * don't care fd of stdout (1) either. */
250 dup2 (STDERR_FILENO, STDOUT_FILENO);
252 /* This process is now out of reach of shell's job control.
253 * To resolve the rare but possible condition where this
254 * "daemon" is started but never connected this process will
255 * (only) have 30 seconds to exist. */
259 peer_addr_len = sizeof (peer_addr);
260 peer = accept (sock, (struct sockaddr *) &peer_addr, &peer_addr_len);
262 fprintf (stderr, "Error: accept() failed: %s\n",
268 peer_file = fdopen (peer, "w+");
269 if (peer_file == NULL) {
270 fprintf (stderr, "Error: fdopen() failed: %s\n",
276 do_smtp_to_file (peer_file, output);