examples: Add ssh_server_fork example
Signed-off-by: Audrius Butkevicius <audrius.butkevicius@gmail.com> Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
This commit is contained in:
Audrius Butkevicius
Andreas Schneider
parent
00949383f4
commit
afe97d6cab
@ -48,6 +48,7 @@ endif(CMAKE_COMPILER_IS_GNUCC AND NOT MINGW AND NOT OS2)
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# HEADER FILES
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check_include_file(argp.h HAVE_ARGP_H)
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check_include_file(pty.h HAVE_PTY_H)
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check_include_file(utmp.h HAVE_UTMP_H)
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check_include_file(termios.h HAVE_TERMIOS_H)
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check_include_file(unistd.h HAVE_UNISTD_H)
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check_include_file(util.h HAVE_UTIL_H)
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@ -20,6 +20,9 @@
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/* Define to 1 if you have the <pty.h> header file. */
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#cmakedefine HAVE_PTY_H 1
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/* Define to 1 if you have the <utmp.h> header file. */
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#cmakedefine HAVE_UTMP_H 1
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/* Define to 1 if you have the <util.h> header file. */
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#cmakedefine HAVE_UTIL_H 1
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@ -29,6 +29,9 @@ if (UNIX AND NOT WIN32)
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if (HAVE_LIBUTIL)
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add_executable(samplesshd-tty samplesshd-tty.c)
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target_link_libraries(samplesshd-tty ${LIBSSH_SHARED_LIBRARY} ${ARGP_LIBRARIES} util)
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add_executable(ssh_server_fork ssh_server_fork.c)
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target_link_libraries(ssh_server_fork ${LIBSSH_SHARED_LIBRARY} ${ARGP_LIBRARIES} util)
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endif (HAVE_LIBUTIL)
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endif (WITH_SERVER)
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641
examples/ssh_server_fork.c
Normal file
641
examples/ssh_server_fork.c
Normal file
@ -0,0 +1,641 @@
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/* This is a sample implementation of a libssh based SSH server */
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/*
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Copyright 2014 Audrius Butkevicius
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This file is part of the SSH Library
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You are free to copy this file, modify it in any way, consider it being public
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domain. This does not apply to the rest of the library though, but it is
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allowed to cut-and-paste working code from this file to any license of
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program.
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The goal is to show the API in action.
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*/
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#include "config.h"
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#include <libssh/callbacks.h>
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#include <libssh/poll.h>
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#include <libssh/server.h>
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#ifdef HAVE_ARGP_H
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#include <argp.h>
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#endif
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#include <fcntl.h>
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#ifdef HAVE_LIBUTIL_H
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#include <libutil.h>
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#endif
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#ifdef HAVE_PTY_H
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#include <pty.h>
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#endif
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#include <signal.h>
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#include <stdlib.h>
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#ifdef HAVE_UTMP_H
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#include <utmp.h>
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#endif
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#ifdef HAVE_UTIL_H
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#include <util.h>
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#endif
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#include <sys/ioctl.h>
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#include <sys/wait.h>
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#ifndef KEYS_FOLDER
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#ifdef _WIN32
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#define KEYS_FOLDER
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#else
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#define KEYS_FOLDER "/etc/ssh/"
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#endif
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#endif
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#define USER "myuser"
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#define PASS "mypassword"
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#define BUF_SIZE 1048576
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#define SESSION_END (SSH_CLOSED | SSH_CLOSED_ERROR)
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#define SFTP_SERVER_PATH "/usr/lib/sftp-server"
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#ifdef HAVE_ARGP_H
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const char *argp_program_version = "libssh server example "
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SSH_STRINGIFY(LIBSSH_VERSION);
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const char *argp_program_bug_address = "<libssh@libssh.org>";
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/* Program documentation. */
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static char doc[] = "libssh -- a Secure Shell protocol implementation";
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/* A description of the arguments we accept. */
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static char args_doc[] = "BINDADDR";
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/* The options we understand. */
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static struct argp_option options[] = {
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{
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.name = "port",
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.key = 'p',
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.arg = "PORT",
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.flags = 0,
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.doc = "Set the port to bind.",
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.group = 0
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},
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{
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.name = "hostkey",
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.key = 'k',
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.arg = "FILE",
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.flags = 0,
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.doc = "Set the host key.",
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.group = 0
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},
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{
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.name = "dsakey",
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.key = 'd',
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.arg = "FILE",
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.flags = 0,
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.doc = "Set the dsa key.",
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.group = 0
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},
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{
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.name = "rsakey",
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.key = 'r',
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.arg = "FILE",
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.flags = 0,
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.doc = "Set the rsa key.",
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.group = 0
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},
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{
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.name = "verbose",
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.key = 'v',
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.arg = NULL,
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.flags = 0,
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.doc = "Get verbose output.",
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.group = 0
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},
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{NULL, 0, NULL, 0, NULL, 0}
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};
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/* Parse a single option. */
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static error_t parse_opt (int key, char *arg, struct argp_state *state) {
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/* Get the input argument from argp_parse, which we
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* know is a pointer to our arguments structure. */
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ssh_bind sshbind = state->input;
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switch (key) {
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case 'p':
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ssh_bind_options_set(sshbind, SSH_BIND_OPTIONS_BINDPORT_STR, arg);
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break;
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case 'd':
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ssh_bind_options_set(sshbind, SSH_BIND_OPTIONS_DSAKEY, arg);
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break;
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case 'k':
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ssh_bind_options_set(sshbind, SSH_BIND_OPTIONS_HOSTKEY, arg);
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break;
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case 'r':
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ssh_bind_options_set(sshbind, SSH_BIND_OPTIONS_RSAKEY, arg);
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break;
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case 'v':
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ssh_bind_options_set(sshbind, SSH_BIND_OPTIONS_LOG_VERBOSITY_STR,
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"3");
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break;
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case ARGP_KEY_ARG:
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if (state->arg_num >= 1) {
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/* Too many arguments. */
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argp_usage (state);
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}
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ssh_bind_options_set(sshbind, SSH_BIND_OPTIONS_BINDADDR, arg);
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break;
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case ARGP_KEY_END:
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if (state->arg_num < 1) {
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/* Not enough arguments. */
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argp_usage (state);
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}
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break;
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default:
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return ARGP_ERR_UNKNOWN;
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}
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return 0;
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}
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/* Our argp parser. */
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static struct argp argp = {options, parse_opt, args_doc, doc, NULL, NULL, NULL};
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#endif /* HAVE_ARGP_H */
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/* A userdata struct for channel. */
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struct channel_data_struct {
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/* pid of the child process the channel will spawn. */
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pid_t pid;
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/* For PTY allocation */
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socket_t pty_master;
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socket_t pty_slave;
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/* For communication with the child process. */
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socket_t stdin;
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socket_t stdout;
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/* Only used for subsystem and exec requests. */
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socket_t stderr;
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/* Event which is used to poll the above descriptors. */
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ssh_event event;
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/* Terminal size struct. */
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struct winsize *winsize;
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};
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/* A userdata struct for session. */
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struct session_data_struct {
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/* Pointer to the channel the session will allocate. */
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ssh_channel channel;
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int auth_attempts;
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int authenticated;
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};
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static int data_function(ssh_session session, ssh_channel channel, void *data,
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uint32_t len, int is_stderr, void *userdata) {
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struct channel_data_struct *cdata = (struct channel_data_struct *) userdata;
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(void) session;
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(void) channel;
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(void) is_stderr;
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if (len == 0 || cdata->pid < 1 || kill(cdata->pid, 0) < 0) {
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return 0;
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}
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return write(cdata->stdin, (char *) data, len);
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}
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static int pty_request(ssh_session session, ssh_channel channel,
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const char *term, int cols, int rows, int py, int px,
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void *userdata) {
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struct channel_data_struct *cdata = (struct channel_data_struct *)userdata;
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(void) session;
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(void) channel;
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(void) term;
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cdata->winsize->ws_row = rows;
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cdata->winsize->ws_col = cols;
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cdata->winsize->ws_xpixel = px;
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cdata->winsize->ws_ypixel = py;
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if (openpty(&cdata->pty_master, &cdata->pty_slave, NULL, NULL,
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cdata->winsize) != 0) {
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fprintf(stderr, "Failed to open pty\n");
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return SSH_ERROR;
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}
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return SSH_OK;
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}
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static int pty_resize(ssh_session session, ssh_channel channel, int cols,
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int rows, int py, int px, void *userdata) {
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struct channel_data_struct *cdata = (struct channel_data_struct *)userdata;
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(void) session;
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(void) channel;
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cdata->winsize->ws_row = rows;
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cdata->winsize->ws_col = cols;
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cdata->winsize->ws_xpixel = px;
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cdata->winsize->ws_ypixel = py;
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if (cdata->pty_master != -1) {
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return ioctl(cdata->pty_master, TIOCSWINSZ, cdata->winsize);
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}
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return SSH_ERROR;
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}
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static int exec_pty(const char *mode, const char *command,
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struct channel_data_struct *cdata) {
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switch(cdata->pid = fork()) {
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case -1:
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close(cdata->pty_master);
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close(cdata->pty_slave);
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fprintf(stderr, "Failed to fork\n");
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return SSH_ERROR;
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case 0:
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close(cdata->pty_master);
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if (login_tty(cdata->pty_slave) != 0) {
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exit(1);
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}
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execl("/bin/sh", "sh", mode, command, NULL);
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exit(0);
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default:
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close(cdata->pty_slave);
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/* pty fd is bi-directional */
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cdata->stdout = cdata->stdin = cdata->pty_master;
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}
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return SSH_OK;
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}
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static int exec_nopty(const char *command, struct channel_data_struct *cdata) {
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int in[2], out[2], err[2];
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/* Do the plumbing to be able to talk with the child process. */
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if (pipe(in) != 0) {
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goto stdin_failed;
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}
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if (pipe(out) != 0) {
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goto stdout_failed;
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}
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if (pipe(err) != 0) {
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goto stderr_failed;
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}
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switch(cdata->pid = fork()) {
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case -1:
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goto fork_failed;
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case 0:
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/* Finish the plumbing in the child process. */
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close(in[1]);
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close(out[0]);
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close(err[0]);
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dup2(in[0], STDIN_FILENO);
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dup2(out[1], STDOUT_FILENO);
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dup2(err[1], STDERR_FILENO);
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close(in[0]);
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close(out[1]);
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close(err[1]);
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/* exec the requested command. */
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execl("/bin/sh", "sh", "-c", command, NULL);
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exit(0);
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}
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close(in[0]);
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close(out[1]);
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close(err[1]);
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cdata->stdin = in[1];
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cdata->stdout = out[0];
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cdata->stderr = err[0];
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return SSH_OK;
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fork_failed:
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close(err[0]);
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close(err[1]);
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stderr_failed:
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close(out[0]);
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close(out[1]);
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stdout_failed:
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close(in[0]);
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close(in[1]);
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stdin_failed:
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return SSH_ERROR;
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}
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static int exec_request(ssh_session session, ssh_channel channel,
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const char *command, void *userdata) {
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struct channel_data_struct *cdata = (struct channel_data_struct *) userdata;
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(void) session;
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(void) channel;
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if(cdata->pid > 0) {
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return SSH_ERROR;
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}
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if (cdata->pty_master != -1 && cdata->pty_slave != -1) {
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return exec_pty("-c", command, cdata);
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}
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return exec_nopty(command, cdata);
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}
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static int shell_request(ssh_session session, ssh_channel channel,
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void *userdata) {
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struct channel_data_struct *cdata = (struct channel_data_struct *) userdata;
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(void) session;
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(void) channel;
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if(cdata->pid > 0) {
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return SSH_ERROR;
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}
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if (cdata->pty_master != -1 && cdata->pty_slave != -1) {
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return exec_pty("-l", NULL, cdata);
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}
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/* Client requested a shell without a pty, let's pretend we allow that */
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return SSH_OK;
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}
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static int subsystem_request(ssh_session session, ssh_channel channel,
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const char *subsystem, void *userdata) {
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/* subsystem requests behave simillarly to exec requests. */
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if (strcmp(subsystem, "sftp") == 0) {
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return exec_request(session, channel, SFTP_SERVER_PATH, userdata);
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}
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return SSH_ERROR;
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}
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static int auth_password(ssh_session session, const char *user,
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const char *pass, void *userdata) {
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struct session_data_struct *sdata = (struct session_data_struct *) userdata;
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(void) session;
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if (strcmp(user, USER) == 0 && strcmp(pass, PASS) == 0) {
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sdata->authenticated = 1;
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return SSH_AUTH_SUCCESS;
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}
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sdata->auth_attempts++;
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return SSH_AUTH_DENIED;
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}
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static ssh_channel channel_open(ssh_session session, void *userdata) {
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struct session_data_struct *sdata = (struct session_data_struct *) userdata;
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sdata->channel = ssh_channel_new(session);
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return sdata->channel;
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}
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static int process_stdout(socket_t fd, int revents, void *userdata) {
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char buf[BUF_SIZE];
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int n = -1;
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ssh_channel channel = (ssh_channel) userdata;
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if (channel != NULL && (revents & POLLIN) != 0) {
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n = read(fd, buf, BUF_SIZE);
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if (n > 0) {
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ssh_channel_write(channel, buf, n);
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}
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}
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return n;
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}
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static int process_stderr(socket_t fd, int revents, void *userdata) {
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char buf[BUF_SIZE];
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int n = -1;
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ssh_channel channel = (ssh_channel) userdata;
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if (channel != NULL && (revents & POLLIN) != 0) {
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n = read(fd, buf, BUF_SIZE);
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if (n > 0) {
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ssh_channel_write_stderr(channel, buf, n);
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}
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}
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return n;
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}
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static void handle_session(ssh_event event, ssh_session session) {
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int n, rc;
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/* Structure for storing the pty size. */
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struct winsize wsize = {
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.ws_row = 0,
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.ws_col = 0,
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.ws_xpixel = 0,
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.ws_ypixel = 0
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};
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/* Our struct holding information about the channel. */
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struct channel_data_struct cdata = {
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.pid = 0,
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.pty_master = -1,
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.pty_slave = -1,
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.stdin = -1,
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.stdout = -1,
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.stderr = -1,
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.event = NULL,
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.winsize = &wsize
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};
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/* Our struct holding information about the session. */
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struct session_data_struct sdata = {
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.channel = NULL,
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.auth_attempts = 0,
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.authenticated = 0
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};
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struct ssh_channel_callbacks_struct channel_cb = {
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.userdata = &cdata,
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.channel_pty_request_function = pty_request,
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.channel_pty_window_change_function = pty_resize,
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.channel_shell_request_function = shell_request,
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.channel_exec_request_function = exec_request,
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.channel_data_function = data_function,
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.channel_subsystem_request_function = subsystem_request
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};
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struct ssh_server_callbacks_struct server_cb = {
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.userdata = &sdata,
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.auth_password_function = auth_password,
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.channel_open_request_session_function = channel_open,
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};
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ssh_callbacks_init(&server_cb);
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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_set_auth_methods(session, SSH_AUTH_METHOD_PASSWORD);
|
||||
ssh_event_add_session(event, session);
|
||||
|
||||
n = 0;
|
||||
while (sdata.authenticated == 0 || sdata.channel == NULL) {
|
||||
/* If the user has used up all attempts, or if he hasn't been able to
|
||||
* authenticate in 10 seconds (n * 100ms), disconnect. */
|
||||
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 {
|
||||
/* Poll the main event which takes care of the session, the channel and
|
||||
* even our child process's stdout/stderr (once it's started). */
|
||||
if (ssh_event_dopoll(event, -1) == SSH_ERROR) {
|
||||
ssh_channel_close(sdata.channel);
|
||||
}
|
||||
|
||||
/* If child process's stdout/stderr has been registered with the event,
|
||||
* or the child process hasn't started yet, continue. */
|
||||
if (cdata.event != NULL || cdata.pid == 0) {
|
||||
continue;
|
||||
}
|
||||
/* Executed only once, once the child process starts. */
|
||||
cdata.event = event;
|
||||
/* If stdout valid, add stdout to be monitored by the poll event. */
|
||||
if (cdata.stdout != -1) {
|
||||
if (ssh_event_add_fd(event, cdata.stdout, POLLIN, process_stdout,
|
||||
sdata.channel) != SSH_OK) {
|
||||
fprintf(stderr, "Failed to register stdout to poll context\n");
|
||||
ssh_channel_close(sdata.channel);
|
||||
}
|
||||
}
|
||||
|
||||
/* If stderr valid, add stderr to be monitored by the poll event. */
|
||||
if (cdata.stderr != -1){
|
||||
if (ssh_event_add_fd(event, cdata.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.stdin);
|
||||
close(cdata.stdout);
|
||||
close(cdata.stderr);
|
||||
|
||||
/* Remove the descriptors from the polling context, since they are now
|
||||
* closed, they will always trigger during the poll calls. */
|
||||
ssh_event_remove_fd(event, cdata.stdout);
|
||||
ssh_event_remove_fd(event, cdata.stderr);
|
||||
|
||||
/* If the child process exited. */
|
||||
if (kill(cdata.pid, 0) < 0 && WIFEXITED(rc)) {
|
||||
rc = WEXITSTATUS(rc);
|
||||
ssh_channel_request_send_exit_status(sdata.channel, rc);
|
||||
/* If client terminated the channel or the process did not exit nicely,
|
||||
* but only if something has been forked. */
|
||||
} else if (cdata.pid > 0) {
|
||||
kill(cdata.pid, SIGKILL);
|
||||
}
|
||||
|
||||
ssh_channel_send_eof(sdata.channel);
|
||||
ssh_channel_close(sdata.channel);
|
||||
|
||||
/* Wait up to 5 seconds for the client to terminate the session. */
|
||||
for (n = 0; n < 50 && (ssh_get_status(session) & SESSION_END) == 0; n++) {
|
||||
ssh_event_dopoll(event, 100);
|
||||
}
|
||||
}
|
||||
|
||||
/* SIGCHLD handler for cleaning up dead children. */
|
||||
static void sigchld_handler(int signo) {
|
||||
(void) signo;
|
||||
while (waitpid(-1, NULL, WNOHANG) > 0);
|
||||
}
|
||||
|
||||
int main(int argc, char **argv) {
|
||||
ssh_bind sshbind;
|
||||
ssh_session session;
|
||||
ssh_event event;
|
||||
struct sigaction sa;
|
||||
|
||||
/* Set up SIGCHLD handler. */
|
||||
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;
|
||||
}
|
||||
|
||||
ssh_init();
|
||||
sshbind = ssh_bind_new();
|
||||
|
||||
ssh_bind_options_set(sshbind, SSH_BIND_OPTIONS_DSAKEY,
|
||||
KEYS_FOLDER "ssh_host_dsa_key");
|
||||
ssh_bind_options_set(sshbind, SSH_BIND_OPTIONS_RSAKEY,
|
||||
KEYS_FOLDER "ssh_host_rsa_key");
|
||||
|
||||
#ifdef HAVE_ARGP_H
|
||||
argp_parse(&argp, argc, argv, 0, 0, sshbind);
|
||||
#else
|
||||
(void) argc;
|
||||
(void) argv;
|
||||
#endif /* HAVE_ARGP_H */
|
||||
|
||||
if(ssh_bind_listen(sshbind) < 0) {
|
||||
fprintf(stderr, "%s\n", ssh_get_error(sshbind));
|
||||
return 1;
|
||||
}
|
||||
|
||||
while (1) {
|
||||
session = ssh_new();
|
||||
if (session == NULL) {
|
||||
fprintf(stderr, "Failed to allocate session\n");
|
||||
continue;
|
||||
}
|
||||
|
||||
/* Blocks until there is a new incoming connection. */
|
||||
if(ssh_bind_accept(sshbind, session) != SSH_ERROR) {
|
||||
switch(fork()) {
|
||||
case 0:
|
||||
/* Remove the SIGCHLD handler inherited from parent. */
|
||||
sa.sa_handler = SIG_DFL;
|
||||
sigaction(SIGCHLD, &sa, NULL);
|
||||
/* Remove socket binding, which allows us to restart the
|
||||
* parent process, without terminating existing sessions. */
|
||||
ssh_bind_free(sshbind);
|
||||
|
||||
event = ssh_event_new();
|
||||
if (event != NULL) {
|
||||
/* Blocks until the SSH session ends by either
|
||||
* child process exiting, or client disconnecting. */
|
||||
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 {
|
||||
fprintf(stderr, "%s\n", ssh_get_error(sshbind));
|
||||
}
|
||||
/* Since the session has been passed to a child fork, do some cleaning
|
||||
* up at the parent process. */
|
||||
ssh_disconnect(session);
|
||||
ssh_free(session);
|
||||
}
|
||||
|
||||
ssh_bind_free(sshbind);
|
||||
ssh_finalize();
|
||||
return 0;
|
||||
}
|
||||
Loading…
x
Reference in New Issue
Block a user