/* Run the given command line as if with exec. What we actually do is fork the
command line as a subprocess, then loop, relaying data between the socket and
the subprocess. This allows Ncat to handle SSL from the socket and give plain
text to the subprocess, and also allows things like logging and line delays.
Never returns. */
void netexec(struct fdinfo *info, char *cmdexec)
{
int child_stdin[2];
int child_stdout[2];
int pid;
int crlf_state;
char buf[DEFAULT_TCP_BUF_LEN];
int maxfd;
if (o.debug) {
switch (o.execmode) {
case EXEC_SHELL:
logdebug("Executing with shell: %s\n", cmdexec);
break;
#ifdef HAVE_LUA
case EXEC_LUA:
logdebug("Executing as lua script: %s\n", cmdexec);
break;
#endif
default:
logdebug("Executing: %s\n", cmdexec);
break;
}
}
if (pipe(child_stdin) == -1 || pipe(child_stdout) == -1)
bye("Can't create child pipes: %s", strerror(errno));
pid = fork();
if (pid == -1)
bye("Error in fork: %s", strerror(errno));
if (pid == 0) {
/* This is the child process. Exec the command. */
close(child_stdin[1]);
close(child_stdout[0]);
/* We might have turned off SIGPIPE handling in ncat_listen.c. Since
the child process SIGPIPE might mean that the connection got broken,
ignoring it could result in an infinite loop if the code here
ignores the error codes of read()/write() calls. So, just in case,
let's restore SIGPIPE so that writing to a broken pipe results in
killing the child process. */
Signal(SIGPIPE, SIG_DFL);
/* rearrange stdin and stdout */
Dup2(child_stdin[0], STDIN_FILENO);
Dup2(child_stdout[1], STDOUT_FILENO);
switch (o.execmode) {
char **cmdargs;
case EXEC_SHELL:
execl("/bin/sh", "sh", "-c", cmdexec, (void *) NULL);
break;
#ifdef HAVE_LUA
case EXEC_LUA:
lua_run();
break;
#endif
default:
cmdargs = cmdline_split(cmdexec);
execv(cmdargs[0], cmdargs);
break;
}
/* exec failed. */
die("exec");
}
close(child_stdin[0]);
close(child_stdout[1]);
maxfd = child_stdout[0];
if (info->fd > maxfd)
maxfd = info->fd;
/* This is the parent process. Enter a "caretaker" loop that reads from the
socket and writes to the suprocess, and reads from the subprocess and
writes to the socket. We exit the loop on any read error (or EOF). On a
write error we just close the opposite side of the conversation. */
crlf_state = 0;
for (;;) {
fd_set fds;
int r, n_r;
FD_ZERO(&fds);
FD_SET(info->fd, &fds);
FD_SET(child_stdout[0], &fds);
r = fselect(maxfd + 1, &fds, NULL, NULL, NULL);
if (r == -1) {
if (errno == EINTR)
continue;
else
break;
}
if (FD_ISSET(info->fd, &fds)) {
int pending;
do {
n_r = ncat_recv(info, buf, sizeof(buf), &pending);
if (n_r <= 0)
goto loop_end;
write_loop(child_stdin[1], buf, n_r);
} while (pending);
}
if (FD_ISSET(child_stdout[0], &fds)) {
char *crlf = NULL, *wbuf;
n_r = read(child_stdout[0], buf, sizeof(buf));
if (n_r <= 0)
break;
wbuf = buf;
if (o.crlf) {
if (fix_line_endings((char *) buf, &n_r, &crlf, &crlf_state))
wbuf = crlf;
}
ncat_send(info, wbuf, n_r);
if (crlf != NULL)
free(crlf);
}
}
loop_end:
#ifdef HAVE_OPENSSL
if (info->ssl != NULL) {
SSL_shutdown(info->ssl);
SSL_free(info->ssl);
}
#endif
close(info->fd);
exit(0);
}
/* Run the given command line as if with exec. What we actually do is fork the
command line as a subprocess, then loop, relaying data between the socket and
the subprocess. This allows Ncat to handle SSL from the socket and give plain
text to the subprocess, and also allows things like logging and line delays.
Never returns. */
void netexec(struct fdinfo *info, char *cmdexec)
{
int child_stdin[2];
int child_stdout[2];
int pid;
int crlf_state;
char buf[DEFAULT_TCP_BUF_LEN];
int maxfd;
if (o.debug) {
if (o.shellexec)
logdebug("Executing with shell: %s\n", cmdexec);
else
logdebug("Executing: %s\n", cmdexec);
}
if (pipe(child_stdin) == -1 || pipe(child_stdout) == -1)
bye("Can't create child pipes: %s", strerror(errno));
pid = fork();
if (pid == -1)
bye("Error in fork: %s", strerror(errno));
if (pid == 0) {
/* This is the child process. Exec the command. */
close(child_stdin[1]);
close(child_stdout[0]);
/* rearrange stdin and stdout */
Dup2(child_stdin[0], STDIN_FILENO);
Dup2(child_stdout[1], STDOUT_FILENO);
if (o.shellexec) {
execl("/bin/sh", "sh", "-c", cmdexec, (void *) NULL);
} else {
char **cmdargs;
cmdargs = cmdline_split(cmdexec);
execv(cmdargs[0], cmdargs);
}
/* exec failed.*/
die("exec");
}
close(child_stdin[0]);
close(child_stdout[1]);
maxfd = child_stdout[0];
if (info->fd > maxfd)
maxfd = info->fd;
/* This is the parent process. Enter a "caretaker" loop that reads from the
socket and writes to the suprocess, and reads from the subprocess and
writes to the socket. We exit the loop on any read error (or EOF). On a
write error we just close the opposite side of the conversation. */
crlf_state = 0;
for (;;) {
fd_set fds;
int r, n_r, n_w;
FD_ZERO(&fds);
FD_SET(info->fd, &fds);
FD_SET(child_stdout[0], &fds);
r = fselect(maxfd + 1, &fds, NULL, NULL, NULL);
if (r == -1) {
if (errno == EINTR)
continue;
else
break;
}
if (FD_ISSET(info->fd, &fds)) {
int pending;
do {
n_r = ncat_recv(info, buf, sizeof(buf), &pending);
if (n_r <= 0)
goto loop_end;
n_w = write_loop(child_stdin[1], buf, n_r);
} while (pending);
}
if (FD_ISSET(child_stdout[0], &fds)) {
char *crlf = NULL, *wbuf;
n_r = read(child_stdout[0], buf, sizeof(buf));
if (n_r <= 0)
break;
wbuf = buf;
if (o.crlf) {
if (fix_line_endings((char *) buf, &n_r, &crlf, &crlf_state))
wbuf = crlf;
}
n_w = ncat_send(info, wbuf, n_r);
if (crlf != NULL)
free(crlf);
}
}
loop_end:
#ifdef HAVE_OPENSSL
if (info->ssl != NULL) {
SSL_shutdown(info->ssl);
SSL_free(info->ssl);
}
#endif
close(info->fd);
exit(0);
}