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/* smtp-dummy - Dummy SMTP server that delivers mail to the given file
*
* Copyright © 2010 Carl Worth
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see http://www.gnu.org/licenses/ .
*
* Authors: Carl Worth <cworth@cworth.org>
*/
/* This (non-compliant) SMTP server listens on localhost, port 25025
* and delivers a mail received to the given filename, (specified as a
* command-line argument). It exists after the first client connection
* completes.
*
* It implements very little of the SMTP protocol, even less than
* specified as the minimum implementation in the SMTP RFC, (not
* implementing RSET, NOOP, nor VRFY). And it doesn't do any
* error-checking on the input.
*
* That is to say, if you use this program, you will very likely find
* cases where it doesn't do everything your SMTP client expects. You
* have been warned.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <netinet/ip.h>
#include <netdb.h>
#include <unistd.h>
#define STRNCMP_LITERAL(var, literal) \
strncmp ((var), (literal), sizeof (literal) - 1)
static void
receive_data_to_file (FILE *peer, FILE *output)
{
char *line = NULL;
size_t line_size;
ssize_t line_len;
while ((line_len = getline (&line, &line_size, peer)) != -1) {
if (STRNCMP_LITERAL (line, ".\r\n") == 0)
break;
if (line_len < 2)
continue;
if (line[line_len-1] == '\n' && line[line_len-2] == '\r') {
line[line_len-2] = '\n';
line[line_len-1] = '\0';
}
fprintf (output, "%s",
line[0] == '.' ? line + 1 : line);
}
free (line);
}
static int
process_command (FILE *peer, FILE *output, const char *command)
{
if (STRNCMP_LITERAL (command, "EHLO ") == 0) {
fprintf (peer, "502 not implemented\r\n");
fflush (peer);
} else if (STRNCMP_LITERAL (command, "HELO ") == 0) {
fprintf (peer, "250 localhost\r\n");
fflush (peer);
} else if (STRNCMP_LITERAL (command, "MAIL FROM:") == 0 ||
STRNCMP_LITERAL (command, "RCPT TO:") == 0) {
fprintf (peer, "250 OK\r\n");
fflush (peer);
} else if (STRNCMP_LITERAL (command, "DATA") == 0) {
fprintf (peer, "354 End data with <CR><LF>.<CR><LF>\r\n");
fflush (peer);
receive_data_to_file (peer, output);
fprintf (peer, "250 OK\r\n");
fflush (peer);
} else if (STRNCMP_LITERAL (command, "QUIT") == 0) {
fprintf (peer, "221 BYE\r\n");
fflush (peer);
return 1;
} else {
fprintf (stderr, "Unknown command: %s\n", command);
}
return 0;
}
static void
do_smtp_to_file (FILE *peer, FILE *output)
{
char *line = NULL;
size_t line_size;
ssize_t line_len;
fprintf (peer, "220 localhost smtp-dummy\r\n");
fflush (peer);
while ((line_len = getline (&line, &line_size, peer)) != -1) {
if (process_command (peer, output, line))
break;
}
free (line);
}
int
main (int argc, char *argv[])
{
char *output_filename;
FILE *peer_file, *output;
int sock, peer, err;
struct sockaddr_in addr, peer_addr;
struct hostent *hostinfo;
socklen_t peer_addr_len;
int reuse;
if (argc != 2) {
fprintf (stderr, "Usage: %s <output-file>\n", argv[0]);
return 1;
}
output_filename = argv[1];
output = fopen (output_filename, "w");
if (output == NULL) {
fprintf (stderr, "Failed to open %s for writing: %s\n",
output_filename, strerror (errno));
return 1;
}
sock = socket (AF_INET, SOCK_STREAM, 0);
if (sock == -1) {
fprintf (stderr, "Error: socket() failed: %s\n",
strerror (errno));
return 1;
}
reuse = 1;
err = setsockopt (sock, SOL_SOCKET, SO_REUSEADDR, &reuse, sizeof (reuse));
if (err) {
fprintf (stderr, "Error: setsockopt() failed: %s\n",
strerror (errno));
return 1;
}
hostinfo = gethostbyname ("localhost");
if (hostinfo == NULL) {
fprintf (stderr, "Unknown host: localhost\n");
return 1;
}
memset (&addr, 0, sizeof (addr));
addr.sin_family = AF_INET;
addr.sin_port = htons (25025);
addr.sin_addr = *(struct in_addr *) hostinfo->h_addr;
err = bind (sock, (struct sockaddr *) &addr, sizeof(addr));
if (err) {
fprintf (stderr, "Error: bind() failed: %s\n",
strerror (errno));
close (sock);
return 1;
}
err = listen (sock, 1);
if (err) {
fprintf (stderr, "Error: listen() failed: %s\n",
strerror (errno));
close (sock);
return 1;
}
peer_addr_len = sizeof (peer_addr);
peer = accept (sock, (struct sockaddr *) &peer_addr, &peer_addr_len);
if (peer == -1) {
fprintf (stderr, "Error: accept() failed: %s\n",
strerror (errno));
return 1;
}
peer_file = fdopen (peer, "w+");
if (peer_file == NULL) {
fprintf (stderr, "Error: fdopen() failed: %s\n",
strerror (errno));
return 1;
}
do_smtp_to_file (peer_file, output);
fclose (output);
fclose (peer_file);
close (sock);
return 0;
}
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