/* nullpop: A NOOP POP3 Server. Based on:
virtualmail-pop3d - a POP3 server with virtual domains support
This code is licensed under the GPL; it has several authors.
vm-pop3d is based on:
GNU POP3 - a small, fast, and efficient POP3 daemon
Copyright (C) 1999 Jakob 'sparky' Kaivo <jkaivo@nodomainname.net>
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 2, 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, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
#define _GNU_SOURCE
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <signal.h>
#include <sys/file.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <pwd.h>
#include <grp.h>
#include <syslog.h>
#include <ctype.h>
/* A command that doesn't exist */
#define BAD_COMMAND "Invalid command"
/* Incorrect number of arguments passed to a command */
#define BAD_ARGS "Invalid arguments"
/* An action on a message that doesn't exist */
#define NO_MESG "No such message"
/* A command that is known but not implemented */
#define NOT_IMPL "Not implemented"
/* The command argument was > 40 characters */
#define TOO_LONG "Argument too long"
/* Longest legal POP command */
#define POP_MAXCMDLEN 255
/* Maximum length of a hostname (is this defined somewhere else?) */
#ifndef MAXHOSTNAMELEN
#define MAXHOSTNAMELEN 64
#endif
#define OK 0
#define ERR_BAD_ARGS 2
#define ERR_NO_MESG 4
#define ERR_NOT_IMPL 5
#define ERR_BAD_CMD 6
#define ERR_TOO_LONG 8
#define ERR_NO_MEM 9
#define ERR_DEAD_SOCK 10
#define ERR_SIGNAL 11
#define ERR_FILE 12
#define ERR_NO_OFILE 13
#define ERR_TIMEOUT 14
unsigned int timeout;
int ifile;
FILE *ofile;
/* Prints out usage information and exits the program */
void
pop3_usage(char *argv0)
{
printf("Usage: %s [OPTIONS]\n", argv0);
printf("Runs the nullpop POP3 daemon.\n\n");
printf(" -t sets idle timeout to TIMEOUT seconds\n");
exit(2);
}
/* This is called if it needs to quit without going to the UPDATE stage.
This is used for conditions such as out of memory, a broken socket, or
being killed on a signal */
int
pop3_abquit(int reason)
{
switch (reason) {
case ERR_NO_MEM:
if (NULL != ofile)
fprintf(ofile, "-ERR Out of memory, quitting\r\n");
syslog(LOG_ERR, "Out of memory");
break;
case ERR_DEAD_SOCK:
if (NULL != ofile) /* should this even print to socket? */
fprintf(ofile, "-ERR Socket closed, quitting\r\n");
syslog(LOG_ERR, "Socket closed");
break;
case ERR_SIGNAL:
if (NULL != ofile)
fprintf(ofile, "-ERR Quitting on signal\r\n");
break;
case ERR_TIMEOUT:
if (NULL != ofile)
fprintf(ofile, "-ERR Session timed out\r\n");
else
syslog(LOG_INFO, "Session timed out for no user");
break;
case ERR_NO_OFILE:
syslog(LOG_ERR, "Quitting - couldn't open stream");
break;
default:
if (NULL != ofile)
fprintf(ofile, "-ERR Quitting (reason unknown)\r\n");
syslog(LOG_ERR, "Unknown quit");
break;
}
fflush(ofile);
exit(1);
}
/* Default signal handler to call the pop3_abquit() function */
void
pop3_signal(int signal)
{
syslog(LOG_ERR, "Quitting on signal: %d", signal);
pop3_abquit(ERR_SIGNAL);
}
/* Gets a line of input from the client */
char *
pop3_readline(int fd)
{
fd_set rfds;
struct timeval tv;
char buf[1024], *ret = NULL;
int available;
FD_ZERO(&rfds);
FD_SET(fd, &rfds);
tv.tv_sec = timeout;
tv.tv_usec = 0;
memset(buf, '\0', 1024);
while (strchr(buf, '\n') == NULL) {
if (timeout > 0) {
available = select(fd + 1, &rfds, NULL, NULL, &tv);
if (!available)
pop3_abquit(ERR_TIMEOUT);
}
if (read(fd, buf, 1024) < 1)
pop3_abquit(ERR_DEAD_SOCK);
if (ret == NULL) {
ret = malloc((strlen(buf) + 1) * sizeof(char));
strcpy(ret, buf);
} else {
ret = realloc(ret, (strlen(ret) + strlen(buf) + 1) * sizeof(char));
strcat(ret, buf);
}
}
return ret;
}
/* Takes a string as input and returns either the remainder of the string
after the first space, or a zero length string if no space */
char *
pop3_args(const char *cmd)
{
int space = -1, i = 0, len;
char *buf;
len = strlen(cmd) + 1;
buf = malloc(len * sizeof(char));
if (buf == NULL)
pop3_abquit(ERR_NO_MEM);
while (space < 0 && i < len) {
if (cmd[i] == ' ')
space = i + 1;
else if (cmd[i] == '\0' || cmd[i] == '\r' || cmd[i] == '\n')
len = i;
i++;
}
if (space < 0)
buf[0] = '\0';
else {
for (i = space; i < len; i++)
if (cmd[i] == '\0' || cmd[i] == '\r' || cmd[i] == '\n')
buf[i - space] = '\0';
else
buf[i - space] = cmd[i];
}
return buf;
}
/* This takes a string and returns the string up to the first space or end of
the string, whichever occurs first */
char *
pop3_cmd(const char *cmd)
{
char *buf;
int i = 0, len;
len = strlen(cmd) + 1;
buf = malloc(len * sizeof(char));
if (buf == NULL)
pop3_abquit(ERR_NO_MEM);
for (i = 0; i < len; i++) {
if (cmd[i] == ' ' || cmd[i] == '\0' || cmd[i] == '\r' || cmd[i] == '\n')
len = i;
else
buf[i] = cmd[i];
}
buf[i - 1] = '\0';
return buf;
}
/* The main part of the daemon. This function reads input from the client and
executes the proper functions. Also handles the bulk of error reporting. */
int
pop3_mainloop(int infile, int outfile)
{
int status = OK;
char *buf, *arg, *cmd;
struct sockaddr_in name;
int namelen = sizeof(name);
char *temp_domain;
ifile = infile;
ofile = fdopen(outfile, "w+");
if (ofile == NULL)
pop3_abquit(ERR_NO_OFILE);
if (getpeername(infile,
(struct sockaddr *) & name, (socklen_t *) & namelen) == 0) {
if ((temp_domain = (char *) inet_ntoa(name.sin_addr)))
syslog(LOG_INFO,"Connect from %s", temp_domain);
else
syslog(LOG_INFO, "Connection opened");
}
else
syslog(LOG_INFO, "Incoming connection opened");
fflush(ofile);
fprintf(ofile, "+OK POP3 \r\n");
for (;;) {
fflush(ofile);
status = OK;
buf = pop3_readline(ifile);
cmd = pop3_cmd(buf);
arg = pop3_args(buf);
if (strlen(arg) > POP_MAXCMDLEN || strlen(cmd) > POP_MAXCMDLEN)
status = ERR_TOO_LONG;
else if (strlen(cmd) > 4)
status = ERR_BAD_CMD;
else if (strncasecmp(cmd, "USER", 4) == 0) {
fprintf(ofile, "+OK\r\n");
status = OK;
} else if (strncasecmp(cmd, "PASS", 4) == 0) {
fprintf(ofile, "+OK\r\n");
status = OK;
} else if (strncasecmp(cmd, "QUIT", 4) == 0) {
fprintf(ofile, "+OK\r\n");
fflush(ofile);
break;
} else if (strncasecmp(cmd, "AUTH", 4) == 0) {
status = ERR_NOT_IMPL;
} else if (strncasecmp(cmd, "STAT", 4) == 0) {
fprintf(ofile, "+OK %d %d\r\n", 0, 0);
status = OK;
} else if (strncasecmp(cmd, "LIST", 4) == 0) {
if (strchr(arg, ' ') != NULL) {
status = ERR_BAD_ARGS;
} else if (strlen(arg) == 0) {
fprintf(ofile, "+OK\r\n");
fprintf(ofile, ".\r\n");
status = OK;
} else {
status = ERR_NO_MESG;
}
} else if (strncasecmp(cmd, "RETR", 4) == 0) {
if ((strlen(arg) == 0) || (strchr(arg, ' ') != NULL))
status = ERR_BAD_ARGS;
else
status = ERR_NO_MESG;
} else if (strncasecmp(cmd, "DELE", 4) == 0) {
if ((strlen(arg) == 0) || (strchr(arg, ' ') != NULL))
status = ERR_BAD_ARGS;
else
status = ERR_NO_MESG;
} else if (strncasecmp(cmd, "NOOP", 4) == 0) {
if (strlen(arg) != 0)
status = ERR_BAD_ARGS;
else {
fprintf(ofile, "+OK\r\n");
status = OK;
}
} else if (strncasecmp(cmd, "RSET", 4) == 0) {
if (strlen(arg) != 0)
status = ERR_BAD_ARGS;
else {
fprintf(ofile, "+OK\r\n");
status = OK;
}
} else if ((strncasecmp(cmd, "TOP", 3) == 0) && (strlen(cmd) == 3)) {
status = ERR_NO_MESG;
} else if (strncasecmp(cmd, "UIDL", 4) == 0) {
if (strchr(arg, ' ') != NULL)
status = ERR_BAD_ARGS;
else
status = ERR_NO_MESG;
} else if (strncasecmp(cmd, "CAPA", 4) == 0) {
if (strlen(arg) != 0)
status = ERR_BAD_ARGS;
else {
fprintf(ofile, "+OK Capability list follows\r\n");
fprintf(ofile, "TOP\r\n");
fprintf(ofile, "USER\r\n");
fprintf(ofile, "RESP-CODES\r\n");
fprintf(ofile, "UIDL\r\n");
fprintf(ofile, ".\r\n");
status = OK;
}
} else {
status = ERR_BAD_CMD;
}
if (status == OK)
fflush(ofile);
else if (status == ERR_BAD_ARGS)
fprintf(ofile, "-ERR " BAD_ARGS "\r\n");
else if (status == ERR_NO_MESG)
fprintf(ofile, "-ERR " NO_MESG "\r\n");
else if (status == ERR_NOT_IMPL)
fprintf(ofile, "-ERR " NOT_IMPL "\r\n");
else if (status == ERR_BAD_CMD)
fprintf(ofile, "-ERR " BAD_COMMAND "\r\n");
else if (status == ERR_TOO_LONG)
fprintf(ofile, "-ERR " TOO_LONG "\r\n");
free(buf);
free(cmd);
free(arg);
}
fflush(ofile);
return OK;
}
int
main(int argc, char **argv)
{
int c = 0;
timeout = 0; /* Timeout turned off */
/* Set the signal handlers */
signal(SIGINT, pop3_signal);
signal(SIGQUIT, pop3_signal);
signal(SIGTERM, pop3_signal);
/* Don't die when a process goes away unexpectedly.
Ignore write on a pipe with no reader. */
signal(SIGPIPE, SIG_IGN);
while ((c = getopt(argc, argv, "t:") && c)) {
switch (c) {
case 't':
timeout = atoi(optarg);
break;
default:
pop3_usage(argv[0]);
break;
}
}
/* Set up for syslog */
openlog("nullpop", LOG_PID, LOG_MAIL);
pop3_mainloop(fileno(stdin), fileno(stdout));
/* Close the syslog connection and exit */
closelog();
return OK;
}
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