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android_mt6572_jiabo/external/toybox/toys/pending/telnetd.c
FuQuan 3ff2876a30 first commit
2025-09-05 16:56:03 +08:00

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/* telnetd.c - Telnet Server
*
* Copyright 2013 Sandeep Sharma <sandeep.jack2756@gmail.com>
* Copyright 2013 Kyungwan Han <asura321@gmail.com>
*
USE_TELNETD(NEWTOY(telnetd, "w#<0b:p#<0>65535=23f:l:FSKi[!wi]", TOYFLAG_USR|TOYFLAG_BIN))
config TELNETD
bool "telnetd"
default n
help
Handle incoming telnet connections
-l LOGIN Exec LOGIN on connect
-f ISSUE_FILE Display ISSUE_FILE instead of /etc/issue
-K Close connection as soon as login exits
-p PORT Port to listen on
-b ADDR[:PORT] Address to bind to
-F Run in foreground
-i Inetd mode
-w SEC Inetd 'wait' mode, linger time SEC
-S Log to syslog (implied by -i or without -F and -w)
*/
#define FOR_telnetd
#include "toys.h"
#include <utmp.h>
GLOBALS(
char *login_path;
char *issue_path;
int port;
char *host_addr;
long w_sec;
int gmax_fd;
pid_t fork_pid;
)
# define IAC 255 /* interpret as command: */
# define DONT 254 /* you are not to use option */
# define DO 253 /* please, you use option */
# define WONT 252 /* I won't use option */
# define WILL 251 /* I will use option */
# define SB 250 /* interpret as subnegotiation */
# define SE 240 /* end sub negotiation */
# define NOP 241 /* No Operation */
# define TELOPT_ECHO 1 /* echo */
# define TELOPT_SGA 3 /* suppress go ahead */
# define TELOPT_TTYPE 24 /* terminal type */
# define TELOPT_NAWS 31 /* window size */
#define BUFSIZE 4*1024
struct term_session {
int new_fd, pty_fd;
pid_t child_pid;
int buff1_avail, buff2_avail;
int buff1_written, buff2_written;
int rem; //unprocessed data from socket
char buff1[BUFSIZE], buff2[BUFSIZE];
struct term_session *next;
};
struct term_session *session_list = NULL;
static void get_sockaddr(char *host, void *buf)
{
in_port_t port_num = htons(TT.port);
struct addrinfo hints, *result;
int status, af = AF_UNSPEC;
char *s;
// [ipv6]:port or exactly one :
if (*host == '[') {
host++;
s = strchr(host, ']');
if (s) *s++ = 0;
else error_exit("bad address '%s'", host-1);
af = AF_INET6;
} else {
s = strrchr(host, ':');
if (s && strchr(host, ':') == s) {
*s = 0;
af = AF_INET;
} else if (s && strchr(host, ':') != s) {
af = AF_INET6;
s = 0;
}
}
if (s++) {
char *ss;
unsigned long p = strtoul(s, &ss, 0);
if (!*s || *ss || p > 65535) error_exit("bad port '%s'", s);
port_num = htons(p);
}
memset(&hints, 0 , sizeof(struct addrinfo));
hints.ai_family = af;
hints.ai_socktype = SOCK_STREAM;
status = getaddrinfo(host, NULL, &hints, &result);
if (status) error_exit("bad address '%s' : %s", host, gai_strerror(status));
memcpy(buf, result->ai_addr, result->ai_addrlen);
freeaddrinfo(result);
if (af == AF_INET) ((struct sockaddr_in*)buf)->sin_port = port_num;
else ((struct sockaddr_in6*)buf)->sin6_port = port_num;
}
static void utmp_entry(void)
{
struct utmp entry;
struct utmp *utp_ptr;
pid_t pid = getpid();
utmpname(_PATH_UTMP);
setutent(); //start from start
while ((utp_ptr = getutent()) != NULL) {
if (utp_ptr->ut_pid == pid && utp_ptr->ut_type >= INIT_PROCESS) break;
}
if (!utp_ptr) entry.ut_type = DEAD_PROCESS;
time(&entry.ut_time);
setutent();
pututline(&entry);
}
static int listen_socket(void)
{
int s, af = AF_INET, yes = 1;
char buf[sizeof(struct sockaddr_storage)];
memset(buf, 0, sizeof(buf));
if (toys.optflags & FLAG_b) {
get_sockaddr(TT.host_addr, buf);
af = ((struct sockaddr *)buf)->sa_family;
} else {
((struct sockaddr_in*)buf)->sin_port = htons(TT.port);
((struct sockaddr_in*)buf)->sin_family = af;
}
s = xsocket(af, SOCK_STREAM, 0);
if (setsockopt(s, SOL_SOCKET, SO_REUSEADDR, (char *)&yes, sizeof(yes)) == -1)
perror_exit("setsockopt");
if (bind(s, (struct sockaddr *)buf, ((af == AF_INET)?
(sizeof(struct sockaddr_in)):(sizeof(struct sockaddr_in6)))) == -1) {
close(s);
perror_exit("bind");
}
if (listen(s, 1) < 0) perror_exit("listen");
return s;
}
static void write_issue(char *tty)
{
int size;
char ch = 0;
struct utsname u;
int fd = open(TT.issue_path, O_RDONLY);
if (fd < 0) return ;
uname(&u);
while ((size = readall(fd, &ch, 1)) > 0) {
if (ch == '\\' || ch == '%') {
if (readall(fd, &ch, 1) <= 0) perror_exit("readall!");
if (ch == 's') fputs(u.sysname, stdout);
if (ch == 'n'|| ch == 'h') fputs(u.nodename, stdout);
if (ch == 'r') fputs(u.release, stdout);
if (ch == 'm') fputs(u.machine, stdout);
if (ch == 'l') fputs(tty, stdout);
}
else if (ch == '\n') {
fputs("\n\r\0", stdout);
} else fputc(ch, stdout);
}
fflush(NULL);
close(fd);
}
static int new_session(int sockfd)
{
char *argv_login[2]; //arguments for execvp cmd, NULL
char tty_name[30]; //tty name length.
int fd, flags, i = 1;
char intial_iacs[] = {IAC, DO, TELOPT_ECHO, IAC, DO, TELOPT_NAWS,
IAC, WILL, TELOPT_ECHO, IAC, WILL, TELOPT_SGA };
setsockopt(sockfd, SOL_SOCKET, SO_KEEPALIVE, &i, sizeof(i));
flags = fcntl(sockfd, F_GETFL);
fcntl(sockfd, F_SETFL, flags | O_NONBLOCK);
if (toys.optflags & FLAG_i) fcntl((sockfd + 1), F_SETFL, flags | O_NONBLOCK);
writeall((toys.optflags & FLAG_i)?1:sockfd, intial_iacs, sizeof(intial_iacs));
if ((TT.fork_pid = forkpty(&fd, tty_name, NULL, NULL)) > 0) {
flags = fcntl(fd, F_GETFL);
fcntl(fd, F_SETFL, flags | O_NONBLOCK);
return fd;
}
if (TT.fork_pid < 0) perror_exit("fork");
write_issue(tty_name);
argv_login[0] = strdup(TT.login_path);
argv_login[1] = NULL;
execvp(argv_login[0], argv_login);
exit(EXIT_FAILURE);
}
static int handle_iacs(struct term_session *tm, int c, int fd)
{
char *curr ,*start,*end;
int i = 0;
curr = start = tm->buff2+tm->buff2_avail;
end = tm->buff2 + c -1;
tm->rem = 0;
while (curr <= end) {
if (*curr != IAC){
if (*curr != '\r') {
toybuf[i++] = *curr++;
continue;
} else {
toybuf[i++] = *curr++;
curr++;
if (curr < end && (*curr == '\n' || *curr == '\0'))
curr++;
continue;
}
}
if ((curr + 1) > end) {
tm->rem = 1;
break;
}
if (*(curr+1) == IAC) { //IAC as data --> IAC IAC
toybuf[i++] = *(curr+1);
curr += 2; //IAC IAC --> 2 bytes
continue;
}
if (*(curr + 1) == NOP || *(curr + 1) == SE) {
curr += 2;
continue;
}
if (*(curr + 1) == SB ) {
if (*(curr+2) == TELOPT_NAWS) {
struct winsize ws;
if ((curr+8) >= end) { //ensure we have data to process.
tm->rem = end - curr;
break;
}
ws.ws_col = (curr[3] << 8) | curr[4];
ws.ws_row = (curr[5] << 8) | curr[6];
ioctl(fd, TIOCSWINSZ, (char *)&ws);
curr += 9;
continue;
} else { //eat non-supported sub neg. options.
curr++, tm->rem++;
while (*curr != IAC && curr <= end) {
curr++;
tm->rem++;
}
if (*curr == IAC) {
tm->rem = 0;
continue;
} else break;
}
}
curr += 3; //skip non-supported 3 bytes.
}
memcpy(start, toybuf, i);
memcpy(start + i, end - tm->rem, tm->rem); //put remaining if we break;
return i;
}
static int dup_iacs(char *start, int fd, int len)
{
char arr[] = {IAC, IAC};
char *needle = NULL;
int ret = 0, c, count = 0;
while (len) {
if (*start == IAC) {
count = writeall(fd, arr, sizeof(arr));
if (count != 2) break; //short write
start++;
ret++;
len--;
continue;
}
needle = memchr(start, IAC, len);
if (needle) c = needle - start;
else c = len;
count = writeall(fd, start, c);
if (count < 0) break;
len -= count;
ret += count;
start += count;
}
return ret;
}
void telnetd_main(void)
{
errno = 0;
fd_set rd, wr;
struct term_session *tm = NULL;
struct timeval tv, *tv_ptr = NULL;
int pty_fd, new_fd, c = 0, w, master_fd = 0;
int inetd_m = toys.optflags & FLAG_i;
if (!(toys.optflags & FLAG_l)) TT.login_path = "/bin/login";
if (!(toys.optflags & FLAG_f)) TT.issue_path = "/etc/issue.net";
if (toys.optflags & FLAG_w) toys.optflags |= FLAG_F;
if (!inetd_m) {
master_fd = listen_socket();
fcntl(master_fd, F_SETFD, FD_CLOEXEC);
if (master_fd > TT.gmax_fd) TT.gmax_fd = master_fd;
if (!(toys.optflags & FLAG_F)) daemon(0, 0);
} else {
pty_fd = new_session(master_fd); //master_fd = 0
if (pty_fd > TT.gmax_fd) TT.gmax_fd = pty_fd;
tm = xzalloc(sizeof(struct term_session));
tm->child_pid = TT.fork_pid;
tm->new_fd = 0;
tm->pty_fd = pty_fd;
if (session_list) {
tm->next = session_list;
session_list = tm;
} else session_list = tm;
}
if ((toys.optflags & FLAG_w) && !session_list) {
tv.tv_sec = TT.w_sec;
tv.tv_usec = 0;
tv_ptr = &tv;
}
signal(SIGCHLD, generic_signal);
for (;;) {
FD_ZERO(&rd);
FD_ZERO(&wr);
if (!inetd_m) FD_SET(master_fd, &rd);
tm = session_list;
while (tm) {
if (tm->pty_fd > 0 && tm->buff1_avail < BUFSIZE) FD_SET(tm->pty_fd, &rd);
if (tm->new_fd >= 0 && tm->buff2_avail < BUFSIZE) FD_SET(tm->new_fd, &rd);
if (tm->pty_fd > 0 && (tm->buff2_avail - tm->buff2_written) > 0)
FD_SET(tm->pty_fd, &wr);
if (tm->new_fd >= 0 && (tm->buff1_avail - tm->buff1_written) > 0)
FD_SET(tm->new_fd, &wr);
tm = tm->next;
}
int r = select(TT.gmax_fd + 1, &rd, &wr, NULL, tv_ptr);
if (!r) return; //timeout
if (r < -1) continue;
if (!inetd_m && FD_ISSET(master_fd, &rd)) { //accept new connection
new_fd = accept(master_fd, NULL, NULL);
if (new_fd < 0) continue;
tv_ptr = NULL;
fcntl(new_fd, F_SETFD, FD_CLOEXEC);
if (new_fd > TT.gmax_fd) TT.gmax_fd = new_fd;
pty_fd = new_session(new_fd);
if (pty_fd > TT.gmax_fd) TT.gmax_fd = pty_fd;
tm = xzalloc(sizeof(struct term_session));
tm->child_pid = TT.fork_pid;
tm->new_fd = new_fd;
tm->pty_fd = pty_fd;
if (session_list) {
tm->next = session_list;
session_list = tm;
} else session_list = tm;
}
tm = session_list;
for (;tm;tm=tm->next) {
if (FD_ISSET(tm->pty_fd, &rd)) {
if ((c = read(tm->pty_fd, tm->buff1 + tm->buff1_avail,
BUFSIZE-tm->buff1_avail)) <= 0) break;
tm->buff1_avail += c;
if ((w = dup_iacs(tm->buff1 + tm->buff1_written, tm->new_fd + inetd_m,
tm->buff1_avail - tm->buff1_written)) < 0) break;
tm->buff1_written += w;
}
if (FD_ISSET(tm->new_fd, &rd)) {
if ((c = read(tm->new_fd, tm->buff2+tm->buff2_avail,
BUFSIZE-tm->buff2_avail)) <= 0) break;
c = handle_iacs(tm, c, tm->pty_fd);
tm->buff2_avail += c;
if ((w = write(tm->pty_fd, tm->buff2+ tm->buff2_written,
tm->buff2_avail - tm->buff2_written)) < 0) break;
tm->buff2_written += w;
}
if (FD_ISSET(tm->pty_fd, &wr)) {
if ((w = write(tm->pty_fd, tm->buff2 + tm->buff2_written,
tm->buff2_avail - tm->buff2_written)) < 0) break;
tm->buff2_written += w;
}
if (FD_ISSET(tm->new_fd, &wr)) {
if ((w = dup_iacs(tm->buff1 + tm->buff1_written, tm->new_fd + inetd_m,
tm->buff1_avail - tm->buff1_written)) < 0) break;
tm->buff1_written += w;
}
if (tm->buff1_written == tm->buff1_avail)
tm->buff1_written = tm->buff1_avail = 0;
if (tm->buff2_written == tm->buff2_avail)
tm->buff2_written = tm->buff2_avail = 0;
fflush(NULL);
}
// Loop to handle (unknown number of) SIGCHLD notifications
while (toys.signal) {
int status;
struct term_session *prev = NULL;
pid_t pid;
// funny little dance to avoid race conditions.
toys.signal = 0;
pid = waitpid(-1, &status, WNOHANG);
if (pid < 0) break;
toys.signal++;
for (tm = session_list; tm; tm = tm->next) {
if (tm->child_pid == pid) break;
prev = tm;
}
if (!tm) return; // reparented child we don't care about
if (toys.optflags & FLAG_i) exit(EXIT_SUCCESS);
if (!prev) session_list = session_list->next;
else prev->next = tm->next;
utmp_entry();
xclose(tm->pty_fd);
xclose(tm->new_fd);
free(tm);
}
}
}
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