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ftpd: add idle and absolute timeouts. This is a security issue,

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otherwise ftpd may end up hanging indefinitely.

function                                             old     new   delta
timeout_handler                                        -     110    +110
ftpd_main                                           2019    2115     +96
packed_usage                                       25662   25685     +23
handle_upload_common                                 306     322     +16
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 3/0 up/down: 245/0)             Total: 245 bytes
This commit is contained in:
Denis Vlasenko 2009-03-16 16:19:53 +00:00
parent f2160b6a09
commit 20c8216897
2 changed files with 52 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
include/usage.h
View File

@ -1281,7 +1281,7 @@
"\n -f Force file system check" \
#define ftpd_trivial_usage \
"[-wvS] [DIR]"
"[-wvS] [-t N] [-T N] [DIR]"
#define ftpd_full_usage "\n\n" \
"FTP server\n" \
"\n" \
@ -1294,6 +1294,7 @@
"\n -w Allow upload" \
"\n -v Log to stderr" \
"\n -S Log to syslog" \
"\n -t,-T Idle and absolute timeouts" \
"\n DIR Change root to this directory" \
#define ftpget_trivial_usage \

70
networking/ftpd.c
View File

@ -8,11 +8,6 @@
*
* Only subset of FTP protocol is implemented but vast majority of clients
* should not have any problem. You have to run this daemon via inetd.
*
* Options:
* -w - enable FTP write commands
*
* TODO: implement "421 Timeout" thingy (alarm(60) while waiting for a cmd).
*/
#include "libbb.h"
@ -46,6 +41,7 @@
#define FTP_GIVEPWORD 331
#define FTP_RESTOK 350
#define FTP_RNFROK 350
#define FTP_TIMEOUT 421
#define FTP_BADSENDCONN 425
#define FTP_BADSENDNET 426
#define FTP_BADSENDFILE 451
@ -77,12 +73,16 @@ enum {
)
struct globals {
char *p_control_line_buf;
len_and_sockaddr *local_addr;
len_and_sockaddr *port_addr;
int pasv_listen_fd;
int proc_self_fd;
int local_file_fd;
int start_time;
int abs_timeout;
int timeout;
off_t local_file_pos;
off_t restart_pos;
len_and_sockaddr *local_addr;
len_and_sockaddr *port_addr;
char *ftp_cmd;
char *ftp_arg;
#if ENABLE_FEATURE_FTP_WRITE
@ -179,6 +179,33 @@ cmdio_write_raw(const char *p_text)
xwrite_str(STDOUT_FILENO, p_text);
}
static void
timeout_handler(int sig UNUSED_PARAM)
{
off_t pos;
int sv_errno = errno;
if (monotonic_sec() - G.start_time > G.abs_timeout)
goto timed_out;
if (!G.local_file_fd)
goto timed_out;
pos = xlseek(G.local_file_fd, 0, SEEK_CUR);
if (pos == G.local_file_pos)
goto timed_out;
G.local_file_pos = pos;
alarm(G.timeout);
errno = sv_errno;
return;
timed_out:
cmdio_write_raw(STR(FTP_TIMEOUT)" Timeout\r\n");
/* TODO: do we need to abort (as opposed to usual shutdown) data transfer? */
exit(1);
}
/* Simple commands */
static void
@ -488,6 +515,7 @@ handle_retr(void)
cmdio_write_error(FTP_FILEFAIL);
goto file_close_out;
}
G.local_file_fd = local_file_fd;
/* Now deactive O_NONBLOCK, otherwise we have a problem
* on DMAPI filesystems such as XFS DMAPI.
@ -506,11 +534,6 @@ handle_retr(void)
if (remote_fd < 0)
goto file_close_out;
/* TODO: if we'll implement timeout, this will need more clever handling.
* Perhaps alarm(N) + checking that current position on local_file_fd
* is advancing. As of now, peer may stall us indefinitely.
*/
bytes_transferred = bb_copyfd_eof(local_file_fd, remote_fd);
close(remote_fd);
if (bytes_transferred < 0)
@ -520,6 +543,7 @@ handle_retr(void)
file_close_out:
close(local_file_fd);
G.local_file_fd = 0;
}
/* List commands */
@ -753,6 +777,7 @@ handle_upload_common(int is_append, int is_unique)
goto close_local_and_bail;
return;
}
G.local_file_fd = local_file_fd;
if (offset)
xlseek(local_file_fd, offset, SEEK_SET);
@ -763,11 +788,6 @@ handle_upload_common(int is_append, int is_unique)
if (remote_fd < 0)
goto close_local_and_bail;
/* TODO: if we'll implement timeout, this will need more clever handling.
* Perhaps alarm(N) + checking that current position on local_file_fd
* is advancing. As of now, peer may stall us indefinitely.
*/
bytes_transferred = bb_copyfd_eof(remote_fd, local_file_fd);
close(remote_fd);
if (bytes_transferred < 0)
@ -777,6 +797,7 @@ handle_upload_common(int is_append, int is_unique)
close_local_and_bail:
close(local_file_fd);
G.local_file_fd = 0;
}
static void
@ -807,6 +828,8 @@ cmdio_get_cmd_and_arg(void)
uint32_t cmdval;
char *cmd;
alarm(G.timeout);
free(G.ftp_cmd);
len = 8 * 1024; /* Paranoia. Peer may send 1 gigabyte long cmd... */
G.ftp_cmd = cmd = xmalloc_reads(STDIN_FILENO, NULL, &len);
@ -878,17 +901,23 @@ int ftpd_main(int argc, char **argv)
{
smallint opts;
opts = getopt32(argv, "l1vS" USE_FEATURE_FTP_WRITE("w"));
INIT_G();
G.start_time = monotonic_sec();
G.abs_timeout = 1 * 60 * 60;
G.timeout = 2 * 60;
opt_complementary = "t+:T+";
opts = getopt32(argv, "l1vS" USE_FEATURE_FTP_WRITE("w") "t:T:", &G.timeout, &G.abs_timeout);
if (opts & (OPT_l|OPT_1)) {
/* Our secret backdoor to ls */
memset(&G, 0, sizeof(G));
/* TODO: pass -n too? */
xchdir(argv[2]);
argv[2] = (char*)"--";
return ls_main(argc, argv);
}
INIT_G();
G.local_addr = get_sock_lsa(STDIN_FILENO);
if (!G.local_addr) {
@ -927,6 +956,7 @@ int ftpd_main(int argc, char **argv)
setsockopt(STDIN_FILENO, SOL_SOCKET, SO_OOBINLINE, &const_int_1, sizeof(const_int_1));
cmdio_write_ok(FTP_GREET);
signal(SIGALRM, timeout_handler);
#ifdef IF_WE_WANT_TO_REQUIRE_LOGIN
{