#include "config.h"
#include <libssh/callbacks.h>
#include <libssh/server.h>
#include <poll.h>
#ifdef HAVE_ARGP_H
#include <argp.h>
#endif
#include <fcntl.h>
#ifdef HAVE_LIBUTIL_H
#include <libutil.h>
#endif
#include <pthread.h>
#ifdef HAVE_PTY_H
#include <pty.h>
#endif
#include <signal.h>
#include <stdlib.h>
#ifdef HAVE_UTMP_H
#include <utmp.h>
#endif
#ifdef HAVE_UTIL_H
#include <util.h>
#endif
#include <sys/ioctl.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <stdio.h>
#ifndef BUF_SIZE
#define BUF_SIZE 1048576
#endif
#ifndef KEYS_FOLDER
#ifdef _WIN32
#define KEYS_FOLDER
#else
#define KEYS_FOLDER "/etc/ssh/"
#endif
#endif
#define SESSION_END (SSH_CLOSED | SSH_CLOSED_ERROR)
#define SFTP_SERVER_PATH "/usr/lib/sftp-server"
static void set_default_keys(ssh_bind sshbind,
int rsa_already_set,
int dsa_already_set,
int ecdsa_already_set) {
if (!rsa_already_set) {
ssh_bind_options_set(sshbind, SSH_BIND_OPTIONS_RSAKEY,
KEYS_FOLDER "ssh_host_rsa_key");
}
if (!dsa_already_set) {
ssh_bind_options_set(sshbind, SSH_BIND_OPTIONS_DSAKEY,
KEYS_FOLDER "ssh_host_dsa_key");
}
if (!ecdsa_already_set) {
ssh_bind_options_set(sshbind, SSH_BIND_OPTIONS_ECDSAKEY,
KEYS_FOLDER "ssh_host_ecdsa_key");
}
ssh_bind_options_set(sshbind, SSH_BIND_OPTIONS_HOSTKEY,
KEYS_FOLDER "ssh_host_ed25519_key");
}
#define DEF_STR_SIZE 1024
char authorizedkeys[DEF_STR_SIZE] = {0};
char username[128] = "myuser";
char password[128] = "mypassword";
#ifdef HAVE_ARGP_H
const char *argp_program_version = "libssh server example "
SSH_STRINGIFY(LIBSSH_VERSION);
const char *argp_program_bug_address = "<libssh@libssh.org>";
static char doc[] = "libssh -- a Secure Shell protocol implementation";
static char args_doc[] = "BINDADDR";
static struct argp_option options[] = {
{
.name = "port",
.key = 'p',
.arg = "PORT",
.flags = 0,
.doc = "Set the port to bind.",
.group = 0
},
{
.name = "hostkey",
.key = 'k',
.arg = "FILE",
.flags = 0,
.doc = "Set a host key. Can be used multiple times. "
"Implies no default keys.",
.group = 0
},
{
.name = "dsakey",
.key = 'd',
.arg = "FILE",
.flags = 0,
.doc = "Set the dsa key.",
.group = 0
},
{
.name = "rsakey",
.key = 'r',
.arg = "FILE",
.flags = 0,
.doc = "Set the rsa key.",
.group = 0
},
{
.name = "ecdsakey",
.key = 'e',
.arg = "FILE",
.flags = 0,
.doc = "Set the ecdsa key.",
.group = 0
},
{
.name = "authorizedkeys",
.key = 'a',
.arg = "FILE",
.flags = 0,
.doc = "Set the authorized keys file.",
.group = 0
},
{
.name = "user",
.key = 'u',
.arg = "USERNAME",
.flags = 0,
.doc = "Set expected username.",
.group = 0
},
{
.name = "pass",
.key = 'P',
.arg = "PASSWORD",
.flags = 0,
.doc = "Set expected password.",
.group = 0
},
{
.name = "no-default-keys",
.key = 'n',
.arg = NULL,
.flags = 0,
.doc = "Do not set default key locations.",
.group = 0
},
{
.name = "verbose",
.key = 'v',
.arg = NULL,
.flags = 0,
.doc = "Get verbose output.",
.group = 0
},
{NULL, 0, NULL, 0, NULL, 0}
};
static error_t parse_opt (int key, char *arg, struct argp_state *state) {
ssh_bind sshbind = state->input;
static int no_default_keys = 0;
static int rsa_already_set = 0, dsa_already_set = 0, ecdsa_already_set = 0;
switch (key) {
case 'n':
no_default_keys = 1;
break;
case 'p':
ssh_bind_options_set(sshbind, SSH_BIND_OPTIONS_BINDPORT_STR, arg);
break;
case 'd':
ssh_bind_options_set(sshbind, SSH_BIND_OPTIONS_DSAKEY, arg);
dsa_already_set = 1;
break;
case 'k':
ssh_bind_options_set(sshbind, SSH_BIND_OPTIONS_HOSTKEY, arg);
no_default_keys = 1;
break;
case 'r':
ssh_bind_options_set(sshbind, SSH_BIND_OPTIONS_RSAKEY, arg);
rsa_already_set = 1;
break;
case 'e':
ssh_bind_options_set(sshbind, SSH_BIND_OPTIONS_ECDSAKEY, arg);
ecdsa_already_set = 1;
break;
case 'a':
strncpy(authorizedkeys, arg, DEF_STR_SIZE-1);
break;
case 'u':
strncpy(username, arg, sizeof(username) - 1);
break;
case 'P':
strncpy(password, arg, sizeof(password) - 1);
break;
case 'v':
ssh_bind_options_set(sshbind, SSH_BIND_OPTIONS_LOG_VERBOSITY_STR,
"3");
break;
case ARGP_KEY_ARG:
if (state->arg_num >= 1) {
argp_usage (state);
}
ssh_bind_options_set(sshbind, SSH_BIND_OPTIONS_BINDADDR, arg);
break;
case ARGP_KEY_END:
if (state->arg_num < 1) {
argp_usage (state);
}
if (!no_default_keys) {
set_default_keys(sshbind,
rsa_already_set,
dsa_already_set,
ecdsa_already_set);
}
break;
default:
return ARGP_ERR_UNKNOWN;
}
return 0;
}
static struct argp argp = {options, parse_opt, args_doc, doc, NULL, NULL, NULL};
#else
static int parse_opt(int argc, char **argv, ssh_bind sshbind) {
int no_default_keys = 0;
int rsa_already_set = 0;
int dsa_already_set = 0;
int ecdsa_already_set = 0;
int key;
while((key = getopt(argc, argv, "a:d:e:k:np:P:r:u:v")) != -1) {
if (key == 'n') {
no_default_keys = 1;
} else if (key == 'p') {
ssh_bind_options_set(sshbind, SSH_BIND_OPTIONS_BINDPORT_STR, optarg);
} else if (key == 'd') {
ssh_bind_options_set(sshbind, SSH_BIND_OPTIONS_DSAKEY, optarg);
dsa_already_set = 1;
} else if (key == 'k') {
ssh_bind_options_set(sshbind, SSH_BIND_OPTIONS_HOSTKEY, optarg);
no_default_keys = 1;
} else if (key == 'r') {
ssh_bind_options_set(sshbind, SSH_BIND_OPTIONS_RSAKEY, optarg);
rsa_already_set = 1;
} else if (key == 'e') {
ssh_bind_options_set(sshbind, SSH_BIND_OPTIONS_ECDSAKEY, optarg);
ecdsa_already_set = 1;
} else if (key == 'a') {
strncpy(authorizedkeys, optarg, DEF_STR_SIZE-1);
} else if (key == 'u') {
strncpy(username, optarg, sizeof(username) - 1);
} else if (key == 'P') {
strncpy(password, optarg, sizeof(password) - 1);
} else if (key == 'v') {
ssh_bind_options_set(sshbind, SSH_BIND_OPTIONS_LOG_VERBOSITY_STR,
"3");
} else {
break;
}
}
if (key != -1) {
printf("Usage: %s [OPTION...] BINDADDR\n"
"libssh %s -- a Secure Shell protocol implementation\n"
"\n"
" -a, --authorizedkeys=FILE Set the authorized keys file.\n"
" -d, --dsakey=FILE Set the dsa key.\n"
" -e, --ecdsakey=FILE Set the ecdsa key.\n"
" -k, --hostkey=FILE Set a host key. Can be used multiple times.\n"
" Implies no default keys.\n"
" -n, --no-default-keys Do not set default key locations.\n"
" -p, --port=PORT Set the port to bind.\n"
" -P, --pass=PASSWORD Set expected password.\n"
" -r, --rsakey=FILE Set the rsa key.\n"
" -u, --user=USERNAME Set expected username.\n"
" -v, --verbose Get verbose output.\n"
" -?, --help Give this help list\n"
"\n"
"Mandatory or optional arguments to long options are also mandatory or optional\n"
"for any corresponding short options.\n"
"\n"
"Report bugs to <libssh@libssh.org>.\n",
argv[0], SSH_STRINGIFY(LIBSSH_VERSION));
return -1;
}
if (optind != argc - 1) {
printf("Usage: %s [OPTION...] BINDADDR\n", argv[0]);
return -1;
}
ssh_bind_options_set(sshbind, SSH_BIND_OPTIONS_BINDADDR, argv[optind]);
if (!no_default_keys) {
set_default_keys(sshbind,
rsa_already_set,
dsa_already_set,
ecdsa_already_set);
}
return 0;
}
#endif
struct channel_data_struct {
pid_t pid;
socket_t pty_master;
socket_t pty_slave;
socket_t child_stdin;
socket_t child_stdout;
socket_t child_stderr;
ssh_event event;
struct winsize *winsize;
};
struct session_data_struct {
ssh_channel channel;
int auth_attempts;
int authenticated;
};
static int data_function(ssh_session session, ssh_channel channel, void *data,
uint32_t len, int is_stderr, void *userdata) {
struct channel_data_struct *cdata = (struct channel_data_struct *) userdata;
(void) session;
(void) channel;
(void) is_stderr;
if (len == 0 || cdata->pid < 1 || kill(cdata->pid, 0) < 0) {
return 0;
}
return write(cdata->child_stdin, (char *) data, len);
}
static int pty_request(ssh_session session, ssh_channel channel,
const char *term, int cols, int rows, int py, int px,
void *userdata) {
struct channel_data_struct *cdata = (struct channel_data_struct *)userdata;
(void) session;
(void) channel;
(void) term;
cdata->winsize->ws_row = rows;
cdata->winsize->ws_col = cols;
cdata->winsize->ws_xpixel = px;
cdata->winsize->ws_ypixel = py;
if (openpty(&cdata->pty_master, &cdata->pty_slave, NULL, NULL,
cdata->winsize) != 0) {
fprintf(stderr, "Failed to open pty\n");
return SSH_ERROR;
}
return SSH_OK;
}
static int pty_resize(ssh_session session, ssh_channel channel, int cols,
int rows, int py, int px, void *userdata) {
struct channel_data_struct *cdata = (struct channel_data_struct *)userdata;
(void) session;
(void) channel;
cdata->winsize->ws_row = rows;
cdata->winsize->ws_col = cols;
cdata->winsize->ws_xpixel = px;
cdata->winsize->ws_ypixel = py;
if (cdata->pty_master != -1) {
return ioctl(cdata->pty_master, TIOCSWINSZ, cdata->winsize);
}
return SSH_ERROR;
}
static int exec_pty(const char *mode, const char *command,
struct channel_data_struct *cdata) {
switch(cdata->pid = fork()) {
case -1:
close(cdata->pty_master);
close(cdata->pty_slave);
fprintf(stderr, "Failed to fork\n");
return SSH_ERROR;
case 0:
close(cdata->pty_master);
if (login_tty(cdata->pty_slave) != 0) {
exit(1);
}
execl("/bin/sh", "sh", mode, command, NULL);
exit(0);
default:
close(cdata->pty_slave);
cdata->child_stdout = cdata->child_stdin = cdata->pty_master;
}
return SSH_OK;
}
static int exec_nopty(const char *command, struct channel_data_struct *cdata) {
int in[2], out[2], err[2];
if (pipe(in) != 0) {
goto stdin_failed;
}
if (pipe(out) != 0) {
goto stdout_failed;
}
if (pipe(err) != 0) {
goto stderr_failed;
}
switch(cdata->pid = fork()) {
case -1:
goto fork_failed;
case 0:
close(in[1]);
close(out[0]);
close(err[0]);
dup2(in[0], STDIN_FILENO);
dup2(out[1], STDOUT_FILENO);
dup2(err[1], STDERR_FILENO);
close(in[0]);
close(out[1]);
close(err[1]);
execl("/bin/sh", "sh", "-c", command, NULL);
exit(0);
}
close(in[0]);
close(out[1]);
close(err[1]);
cdata->child_stdin = in[1];
cdata->child_stdout = out[0];
cdata->child_stderr = err[0];
return SSH_OK;
fork_failed:
close(err[0]);
close(err[1]);
stderr_failed:
close(out[0]);
close(out[1]);
stdout_failed:
close(in[0]);
close(in[1]);
stdin_failed:
return SSH_ERROR;
}
static int exec_request(ssh_session session, ssh_channel channel,
const char *command, void *userdata) {
struct channel_data_struct *cdata = (struct channel_data_struct *) userdata;
(void) session;
(void) channel;
if(cdata->pid > 0) {
return SSH_ERROR;
}
if (cdata->pty_master != -1 && cdata->pty_slave != -1) {
return exec_pty("-c", command, cdata);
}
return exec_nopty(command, cdata);
}
static int shell_request(ssh_session session, ssh_channel channel,
void *userdata) {
struct channel_data_struct *cdata = (struct channel_data_struct *) userdata;
(void) session;
(void) channel;
if(cdata->pid > 0) {
return SSH_ERROR;
}
if (cdata->pty_master != -1 && cdata->pty_slave != -1) {
return exec_pty("-l", NULL, cdata);
}
return SSH_OK;
}
static int subsystem_request(ssh_session session, ssh_channel channel,
const char *subsystem, void *userdata) {
if (strcmp(subsystem, "sftp") == 0) {
return exec_request(session, channel, SFTP_SERVER_PATH, userdata);
}
return SSH_ERROR;
}
static int auth_password(ssh_session session, const char *user,
const char *pass, void *userdata) {
struct session_data_struct *sdata = (struct session_data_struct *) userdata;
(void) session;
if (strcmp(user, username) == 0 && strcmp(pass, password) == 0) {
sdata->authenticated = 1;
return SSH_AUTH_SUCCESS;
}
sdata->auth_attempts++;
return SSH_AUTH_DENIED;
}
static int auth_publickey(ssh_session session,
const char *user,
struct ssh_key_struct *pubkey,
char signature_state,
void *userdata)
{
struct session_data_struct *sdata = (struct session_data_struct *) userdata;
(void) user;
(void) session;
if (signature_state == SSH_PUBLICKEY_STATE_NONE) {
return SSH_AUTH_SUCCESS;
}
if (signature_state != SSH_PUBLICKEY_STATE_VALID) {
return SSH_AUTH_DENIED;
}
if (authorizedkeys[0]) {
ssh_key key = NULL;
int result;
struct stat buf;
if (stat(authorizedkeys, &buf) == 0) {
result = ssh_pki_import_pubkey_file( authorizedkeys, &key );
if ((result != SSH_OK) || (key==NULL)) {
fprintf(stderr,
"Unable to import public key file %s\n",
authorizedkeys);
} else {
result = ssh_key_cmp( key, pubkey, SSH_KEY_CMP_PUBLIC );
ssh_key_free(key);
if (result == 0) {
sdata->authenticated = 1;
return SSH_AUTH_SUCCESS;
}
}
}
}
sdata->authenticated = 0;
return SSH_AUTH_DENIED;
}
static ssh_channel channel_open(ssh_session session, void *userdata) {
struct session_data_struct *sdata = (struct session_data_struct *) userdata;
sdata->channel = ssh_channel_new(session);
return sdata->channel;
}
static int process_stdout(socket_t fd, int revents, void *userdata) {
char buf[BUF_SIZE];
int n = -1;
ssh_channel channel = (ssh_channel) userdata;
if (channel != NULL && (revents & POLLIN) != 0) {
n = read(fd, buf, BUF_SIZE);
if (n > 0) {
ssh_channel_write(channel, buf, n);
}
}
return n;
}
static int process_stderr(socket_t fd, int revents, void *userdata) {
char buf[BUF_SIZE];
int n = -1;
ssh_channel channel = (ssh_channel) userdata;
if (channel != NULL && (revents & POLLIN) != 0) {
n = read(fd, buf, BUF_SIZE);
if (n > 0) {
ssh_channel_write_stderr(channel, buf, n);
}
}
return n;
}
static void handle_session(ssh_event event, ssh_session session) {
int n;
int rc = 0;
struct winsize wsize = {
.ws_row = 0,
.ws_col = 0,
.ws_xpixel = 0,
.ws_ypixel = 0
};
struct channel_data_struct cdata = {
.pid = 0,
.pty_master = -1,
.pty_slave = -1,
.child_stdin = -1,
.child_stdout = -1,
.child_stderr = -1,
.event = NULL,
.winsize = &wsize
};
struct session_data_struct sdata = {
.channel = NULL,
.auth_attempts = 0,
.authenticated = 0
};
struct ssh_channel_callbacks_struct channel_cb = {
.userdata = &cdata,
.channel_pty_request_function = pty_request,
.channel_pty_window_change_function = pty_resize,
.channel_shell_request_function = shell_request,
.channel_exec_request_function = exec_request,
.channel_data_function = data_function,
.channel_subsystem_request_function = subsystem_request
};
struct ssh_server_callbacks_struct server_cb = {
.userdata = &sdata,
.auth_password_function = auth_password,
.channel_open_request_session_function = channel_open,
};
if (authorizedkeys[0]) {
server_cb.auth_pubkey_function = auth_publickey;
ssh_set_auth_methods(session, SSH_AUTH_METHOD_PASSWORD | SSH_AUTH_METHOD_PUBLICKEY);
} else
ssh_set_auth_methods(session, SSH_AUTH_METHOD_PASSWORD);
ssh_callbacks_init(&server_cb);
ssh_callbacks_init(&channel_cb);
ssh_set_server_callbacks(session, &server_cb);
if (ssh_handle_key_exchange(session) != SSH_OK) {
fprintf(stderr, "%s\n", ssh_get_error(session));
return;
}
ssh_event_add_session(event, session);
n = 0;
while (sdata.authenticated == 0 || sdata.channel == NULL) {
if (sdata.auth_attempts >= 3 || n >= 100) {
return;
}
if (ssh_event_dopoll(event, 100) == SSH_ERROR) {
fprintf(stderr, "%s\n", ssh_get_error(session));
return;
}
n++;
}
ssh_set_channel_callbacks(sdata.channel, &channel_cb);
do {
if (ssh_event_dopoll(event, -1) == SSH_ERROR) {
ssh_channel_close(sdata.channel);
}
if (cdata.event != NULL || cdata.pid == 0) {
continue;
}
cdata.event = event;
if (cdata.child_stdout != -1) {
if (ssh_event_add_fd(event, cdata.child_stdout, POLLIN, process_stdout,
sdata.channel) != SSH_OK) {
fprintf(stderr, "Failed to register stdout to poll context\n");
ssh_channel_close(sdata.channel);
}
}
if (cdata.child_stderr != -1){
if (ssh_event_add_fd(event, cdata.child_stderr, POLLIN, process_stderr,
sdata.channel) != SSH_OK) {
fprintf(stderr, "Failed to register stderr to poll context\n");
ssh_channel_close(sdata.channel);
}
}
} while(ssh_channel_is_open(sdata.channel) &&
(cdata.pid == 0 || waitpid(cdata.pid, &rc, WNOHANG) == 0));
close(cdata.pty_master);
close(cdata.child_stdin);
close(cdata.child_stdout);
close(cdata.child_stderr);
ssh_event_remove_fd(event, cdata.child_stdout);
ssh_event_remove_fd(event, cdata.child_stderr);
if (kill(cdata.pid, 0) < 0 && WIFEXITED(rc)) {
rc = WEXITSTATUS(rc);
ssh_channel_request_send_exit_status(sdata.channel, rc);
} else if (cdata.pid > 0) {
kill(cdata.pid, SIGKILL);
}
ssh_channel_send_eof(sdata.channel);
ssh_channel_close(sdata.channel);
for (n = 0; n < 50 && (ssh_get_status(session) & SESSION_END) == 0; n++) {
ssh_event_dopoll(event, 100);
}
}
#ifdef WITH_FORK
static void sigchld_handler(int signo) {
(void) signo;
while (waitpid(-1, NULL, WNOHANG) > 0);
}
#else
static void *session_thread(void *arg) {
ssh_session session = arg;
ssh_event event;
event = ssh_event_new();
if (event != NULL) {
handle_session(event, session);
ssh_event_free(event);
} else {
fprintf(stderr, "Could not create polling context\n");
}
ssh_disconnect(session);
ssh_free(session);
return NULL;
}
#endif
int main(int argc, char **argv) {
ssh_bind sshbind;
ssh_session session;
int rc;
#ifdef WITH_FORK
struct sigaction sa;
sa.sa_handler = sigchld_handler;
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_RESTART | SA_NOCLDSTOP;
if (sigaction(SIGCHLD, &sa, NULL) != 0) {
fprintf(stderr, "Failed to register SIGCHLD handler\n");
return 1;
}
#endif
rc = ssh_init();
if (rc < 0) {
fprintf(stderr, "ssh_init failed\n");
return 1;
}
sshbind = ssh_bind_new();
if (sshbind == NULL) {
fprintf(stderr, "ssh_bind_new failed\n");
ssh_finalize();
return 1;
}
#ifdef HAVE_ARGP_H
argp_parse(&argp, argc, argv, 0, 0, sshbind);
#else
if (parse_opt(argc, argv, sshbind) < 0) {
ssh_bind_free(sshbind);
ssh_finalize();
return 1;
}
#endif
if(ssh_bind_listen(sshbind) < 0) {
fprintf(stderr, "%s\n", ssh_get_error(sshbind));
ssh_bind_free(sshbind);
ssh_finalize();
return 1;
}
while (1) {
session = ssh_new();
if (session == NULL) {
fprintf(stderr, "Failed to allocate session\n");
continue;
}
if(ssh_bind_accept(sshbind, session) != SSH_ERROR) {
#ifdef WITH_FORK
ssh_event event;
switch(fork()) {
case 0:
sa.sa_handler = SIG_DFL;
sigaction(SIGCHLD, &sa, NULL);
ssh_bind_free(sshbind);
event = ssh_event_new();
if (event != NULL) {
handle_session(event, session);
ssh_event_free(event);
} else {
fprintf(stderr, "Could not create polling context\n");
}
ssh_disconnect(session);
ssh_free(session);
exit(0);
case -1:
fprintf(stderr, "Failed to fork\n");
}
#else
pthread_t tid;
rc = pthread_create(&tid, NULL, session_thread, session);
if (rc == 0) {
pthread_detach(tid);
continue;
}
fprintf(stderr, "Failed to pthread_create\n");
#endif
} else {
fprintf(stderr, "%s\n", ssh_get_error(sshbind));
}
ssh_disconnect(session);
ssh_free(session);
}
ssh_bind_free(sshbind);
ssh_finalize();
return 0;
}