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/*
* Part of Very Secure FTPd
* Licence: GPL v2
* Author: Chris Evans
* prelogin.c
*
* Code to parse the FTP protocol prior to a successful login.
*/
#include "prelogin.h"
#include "ftpcmdio.h"
#include "ftpcodes.h"
#include "str.h"
#include "vsftpver.h"
#include "tunables.h"
#include "oneprocess.h"
#include "twoprocess.h"
#include "sysdeputil.h"
#include "sysutil.h"
#include "session.h"
#include "banner.h"
#include "logging.h"
#include "ssl.h"
#include "features.h"
#include "defs.h"
#include "opts.h"
/* Functions used */
static void check_limits(struct vsf_session* p_sess);
static void emit_greeting(struct vsf_session* p_sess);
static void parse_username_password(struct vsf_session* p_sess);
static void handle_user_command(struct vsf_session* p_sess);
static void handle_pass_command(struct vsf_session* p_sess);
static void handle_get(struct vsf_session* p_sess);
static void check_login_delay();
static void check_login_fails(struct vsf_session* p_sess);
void
init_connection(struct vsf_session* p_sess)
{
if (tunable_setproctitle_enable)
{
vsf_sysutil_setproctitle("not logged in");
}
/* Before we talk to the remote, make sure an alarm is set up in case
* writing the initial greetings should block.
*/
vsf_cmdio_set_alarm(p_sess);
/* Check limits before doing an implicit SSL handshake, to avoid DoS
* attacks. This will result in plain text messages being sent to the SSL
* client, but we can live with that.
*/
check_limits(p_sess);
if (tunable_ssl_enable && tunable_implicit_ssl)
{
ssl_control_handshake(p_sess);
}
if (tunable_ftp_enable)
{
emit_greeting(p_sess);
}
parse_username_password(p_sess);
}
static void
check_limits(struct vsf_session* p_sess)
{
struct mystr str_log_line = INIT_MYSTR;
/* Check for client limits (standalone mode only) */
if (tunable_max_clients > 0 &&
p_sess->num_clients > tunable_max_clients)
{
str_alloc_text(&str_log_line, "Connection refused: too many sessions.");
vsf_log_line(p_sess, kVSFLogEntryConnection, &str_log_line);
vsf_cmdio_write_exit(p_sess, FTP_TOO_MANY_USERS,
"There are too many connected users, please try later.");
}
if (tunable_max_per_ip > 0 &&
p_sess->num_this_ip > tunable_max_per_ip)
{
str_alloc_text(&str_log_line,
"Connection refused: too many sessions for this address.");
vsf_log_line(p_sess, kVSFLogEntryConnection, &str_log_line);
vsf_cmdio_write_exit(p_sess, FTP_IP_LIMIT,
"There are too many connections from your internet address.");
}
if (!p_sess->tcp_wrapper_ok)
{
str_alloc_text(&str_log_line,
"Connection refused: tcp_wrappers denial.");
vsf_log_line(p_sess, kVSFLogEntryConnection, &str_log_line);
vsf_cmdio_write_exit(p_sess, FTP_IP_DENY, "Service not available.");
}
vsf_log_line(p_sess, kVSFLogEntryConnection, &str_log_line);
}
static void
emit_greeting(struct vsf_session* p_sess)
{
if (!str_isempty(&p_sess->banner_str))
{
vsf_banner_write(p_sess, &p_sess->banner_str, FTP_GREET);
str_free(&p_sess->banner_str);
vsf_cmdio_write(p_sess, FTP_GREET, "");
}
else if (tunable_ftpd_banner == 0)
{
vsf_cmdio_write(p_sess, FTP_GREET, "(vsFTPd " VSF_VERSION
")");
}
else
{
vsf_cmdio_write(p_sess, FTP_GREET, tunable_ftpd_banner);
}
}
static void
parse_username_password(struct vsf_session* p_sess)
{
while (1)
{
vsf_cmdio_get_cmd_and_arg(p_sess, &p_sess->ftp_cmd_str,
&p_sess->ftp_arg_str, 1);
if (tunable_ftp_enable)
{
if (str_equal_text(&p_sess->ftp_cmd_str, "USER"))
{
handle_user_command(p_sess);
}
else if (str_equal_text(&p_sess->ftp_cmd_str, "PASS"))
{
handle_pass_command(p_sess);
}
else if (str_equal_text(&p_sess->ftp_cmd_str, "QUIT"))
{
vsf_cmdio_write_exit(p_sess, FTP_GOODBYE, "Goodbye.");
}
else if (str_equal_text(&p_sess->ftp_cmd_str, "FEAT"))
{
handle_feat(p_sess);
}
else if (str_equal_text(&p_sess->ftp_cmd_str, "OPTS"))
{
handle_opts(p_sess);
}
else if (tunable_ssl_enable &&
str_equal_text(&p_sess->ftp_cmd_str, "AUTH") &&
!p_sess->control_use_ssl)
{
handle_auth(p_sess);
}
else if (tunable_ssl_enable &&
str_equal_text(&p_sess->ftp_cmd_str, "PBSZ"))
{
handle_pbsz(p_sess);
}
else if (tunable_ssl_enable &&
str_equal_text(&p_sess->ftp_cmd_str, "PROT"))
{
handle_prot(p_sess);
}
else if (str_isempty(&p_sess->ftp_cmd_str) &&
str_isempty(&p_sess->ftp_arg_str))
{
/* Deliberately ignore to avoid NAT device bugs, as per ProFTPd. */
}
else
{
vsf_cmdio_write(p_sess, FTP_LOGINERR,
"Please login with USER and PASS.");
}
}
else if (tunable_http_enable)
{
if (str_equal_text(&p_sess->ftp_cmd_str, "GET"))
{
handle_get(p_sess);
}
else
{
vsf_cmdio_write(p_sess, FTP_LOGINERR, "Bad HTTP verb.");
}
vsf_sysutil_exit(0);
}
}
}
static void
handle_get(struct vsf_session* p_sess)
{
p_sess->is_http = 1;
str_copy(&p_sess->http_get_arg, &p_sess->ftp_arg_str);
str_alloc_text(&p_sess->user_str, "FTP");
str_alloc_text(&p_sess->ftp_arg_str, "<http>");
handle_pass_command(p_sess);
}
static void
handle_user_command(struct vsf_session* p_sess)
{
/* SECURITY: If we're in anonymous only-mode, immediately reject
* non-anonymous usernames in the hope we save passwords going plaintext
* over the network
*/
int is_anon = 1;
str_copy(&p_sess->user_str, &p_sess->ftp_arg_str);
str_upper(&p_sess->ftp_arg_str);
if (!str_equal_text(&p_sess->ftp_arg_str, "FTP") &&
!str_equal_text(&p_sess->ftp_arg_str, "ANONYMOUS"))
{
is_anon = 0;
}
if (!tunable_local_enable && !is_anon)
{
vsf_cmdio_write(
p_sess, FTP_LOGINERR, "This FTP server is anonymous only.");
str_empty(&p_sess->user_str);
return;
}
if (is_anon && p_sess->control_use_ssl && !tunable_allow_anon_ssl &&
!tunable_force_anon_logins_ssl)
{
vsf_cmdio_write(
p_sess, FTP_LOGINERR, "Anonymous sessions may not use encryption.");
str_empty(&p_sess->user_str);
return;
}
if (tunable_ssl_enable && !is_anon && !p_sess->control_use_ssl &&
tunable_force_local_logins_ssl)
{
vsf_cmdio_write(
p_sess, FTP_LOGINERR, "Non-anonymous sessions must use encryption.");
vsf_sysutil_exit(0);
}
if (tunable_ssl_enable && is_anon && !p_sess->control_use_ssl &&
tunable_force_anon_logins_ssl)
{
vsf_cmdio_write(
p_sess, FTP_LOGINERR, "Anonymous sessions must use encryption.");
vsf_sysutil_exit(0);
}
if (tunable_userlist_enable)
{
int located = str_contains_line(&p_sess->userlist_str, &p_sess->user_str);
if ((located && tunable_userlist_deny) ||
(!located && !tunable_userlist_deny))
{
check_login_delay();
vsf_cmdio_write(p_sess, FTP_LOGINERR, "Permission denied.");
check_login_fails(p_sess);
str_empty(&p_sess->user_str);
return;
}
}
if (is_anon && tunable_no_anon_password)
{
/* Fake a password */
str_alloc_text(&p_sess->ftp_arg_str, "<no password>");
handle_pass_command(p_sess);
}
else
{
vsf_cmdio_write(p_sess, FTP_GIVEPWORD, "Please specify the password.");
}
}
static void
handle_pass_command(struct vsf_session* p_sess)
{
if (str_isempty(&p_sess->user_str))
{
vsf_cmdio_write(p_sess, FTP_NEEDUSER, "Login with USER first.");
return;
}
/* These login calls never return if successful */
if (tunable_one_process_model)
{
vsf_one_process_login(p_sess, &p_sess->ftp_arg_str);
}
else
{
vsf_two_process_login(p_sess, &p_sess->ftp_arg_str);
}
vsf_cmdio_write(p_sess, FTP_LOGINERR, "Login incorrect.");
check_login_fails(p_sess);
str_empty(&p_sess->user_str);
/* FALLTHRU if login fails */
}
static void check_login_delay()
{
if (tunable_delay_failed_login)
{
vsf_sysutil_sleep((double) tunable_delay_failed_login);
}
}
static void check_login_fails(struct vsf_session* p_sess)
{
if (++p_sess->login_fails >= tunable_max_login_fails)
{
vsf_sysutil_exit(0);
}
}
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