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libssh/libssh/server.c
2009-09-23 23:51:04 +02:00

868 строки
21 KiB
C

/*
* server.c - functions for creating a SSH server
*
* This file is part of the SSH Library
*
* Copyright (c) 2004-2005 by Aris Adamantiadis
*
* The SSH Library is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or (at your
* option) any later version.
*
* The SSH Library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
* License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with the SSH Library; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
* MA 02111-1307, USA.
*/
/**
* \defgroup ssh_server SSH Server
* \addtogroup ssh_server
* @{
*/
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "libssh/priv.h"
#include "libssh/libssh.h"
#include "libssh/server.h"
#include "libssh/ssh2.h"
#include "libssh/keyfiles.h"
#include "libssh/buffer.h"
#include "libssh/packet.h"
#include "libssh/socket.h"
#include "libssh/channels.h"
#include "libssh/session.h"
#ifdef _WIN32
#include <winsock2.h>
#define SOCKOPT_TYPE_ARG4 char
/* We need to provide hstrerror. Not we can't call the parameter h_errno because it's #defined */
static char *hstrerror(int h_errno_val) {
static char text[50] = {0};
snprintf(text, sizeof(text), "gethostbyname error %d\n", h_errno_val);
return text;
}
#else /* _WIN32 */
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#define SOCKOPT_TYPE_ARG4 int
#endif /* _WIN32 */
/* TODO FIXME: must use getaddrinfo */
static socket_t bind_socket(SSH_BIND *ssh_bind, const char *hostname,
int port) {
struct sockaddr_in myaddr;
struct hostent *hp=NULL;
socket_t s;
int opt = 1;
s = socket(PF_INET, SOCK_STREAM, 0);
if (s < 0) {
ssh_set_error(ssh_bind, SSH_FATAL, "%s", strerror(errno));
return -1;
}
#ifdef HAVE_GETHOSTBYNAME
hp = gethostbyname(hostname);
#endif
if (hp == NULL) {
ssh_set_error(ssh_bind, SSH_FATAL,
"Resolving %s: %s", hostname, hstrerror(h_errno));
close(s);
return -1;
}
memset(&myaddr, 0, sizeof(myaddr));
memcpy(&myaddr.sin_addr, hp->h_addr, hp->h_length);
myaddr.sin_family = hp->h_addrtype;
myaddr.sin_port = htons(port);
if (setsockopt(s, SOL_SOCKET, SO_REUSEADDR, (char *)&opt, sizeof(opt)) < 0) {
ssh_set_error(ssh_bind, SSH_FATAL,
"Setting socket options failed: %s", hstrerror(h_errno));
close(s);
return -1;
}
if (bind(s, (struct sockaddr *) &myaddr, sizeof(myaddr)) < 0) {
ssh_set_error(ssh_bind, SSH_FATAL, "Binding to %s:%d: %s",
hostname,
port,
strerror(errno));
close(s);
return -1;
}
return s;
}
SSH_BIND *ssh_bind_new(void) {
SSH_BIND *ptr;
ptr = malloc(sizeof(SSH_BIND));
if (ptr == NULL) {
return NULL;
}
ZERO_STRUCTP(ptr);
ptr->bindfd = -1;
return ptr;
}
void ssh_bind_set_options(SSH_BIND *ssh_bind, ssh_options options) {
ssh_bind->options = options;
}
int ssh_bind_listen(SSH_BIND *ssh_bind) {
const char *host;
int fd;
if (ssh_bind->options == NULL) {
return -1;
}
if (ssh_init() < 0) {
return -1;
}
host = ssh_bind->options->bindaddr;
if (host == NULL) {
host = "0.0.0.0";
}
fd = bind_socket(ssh_bind, host, ssh_bind->options->bindport);
if (fd < 0) {
return -1;
}
ssh_bind->bindfd = fd;
if (listen(fd, 10) < 0) {
ssh_set_error(ssh_bind, SSH_FATAL,
"Listening to socket %d: %s",
fd, strerror(errno));
close(fd);
return -1;
}
return 0;
}
void ssh_bind_set_blocking(SSH_BIND *ssh_bind, int blocking) {
ssh_bind->blocking = blocking ? 1 : 0;
}
socket_t ssh_bind_get_fd(SSH_BIND *ssh_bind) {
return ssh_bind->bindfd;
}
void ssh_bind_set_fd(SSH_BIND *ssh_bind, socket_t fd) {
ssh_bind->bindfd = fd;
}
void ssh_bind_fd_toaccept(SSH_BIND *ssh_bind) {
ssh_bind->toaccept = 1;
}
ssh_session ssh_bind_accept(SSH_BIND *ssh_bind) {
ssh_session session;
ssh_private_key dsa = NULL;
ssh_private_key rsa = NULL;
int fd = -1;
if (ssh_bind->bindfd < 0) {
ssh_set_error(ssh_bind, SSH_FATAL,
"Can't accept new clients on a not bound socket.");
return NULL;
}
if (ssh_bind->options->dsakey == NULL || ssh_bind->options->rsakey == NULL) {
ssh_set_error(ssh_bind, SSH_FATAL,
"DSA or RSA host key file must be set before accept()");
return NULL;
}
if (ssh_bind->options->dsakey) {
dsa = _privatekey_from_file(ssh_bind, ssh_bind->options->dsakey, TYPE_DSS);
if (dsa == NULL) {
return NULL;
}
}
if (ssh_bind->options->rsakey) {
rsa = _privatekey_from_file(ssh_bind, ssh_bind->options->rsakey, TYPE_RSA);
if (rsa == NULL) {
privatekey_free(dsa);
return NULL;
}
}
fd = accept(ssh_bind->bindfd, NULL, NULL);
if (fd < 0) {
ssh_set_error(ssh_bind, SSH_FATAL,
"Accepting a new connection: %s",
strerror(errno));
privatekey_free(dsa);
privatekey_free(rsa);
return NULL;
}
session = ssh_new();
if (session == NULL) {
ssh_set_error(ssh_bind, SSH_FATAL, "Not enough space");
privatekey_free(dsa);
privatekey_free(rsa);
return NULL;
}
session->server = 1;
session->version = 2;
session->options = ssh_options_copy(ssh_bind->options);
if (session->options == NULL) {
ssh_set_error(ssh_bind, SSH_FATAL, "No space left");
privatekey_free(dsa);
privatekey_free(rsa);
ssh_cleanup(session);
return NULL;
}
ssh_socket_free(session->socket);
session->socket = ssh_socket_new(session);
if (session->socket == NULL) {
privatekey_free(dsa);
privatekey_free(rsa);
ssh_cleanup(session);
return NULL;
}
ssh_socket_set_fd(session->socket,fd);
session->dsa_key = dsa;
session->rsa_key = rsa;
return session;
}
void ssh_bind_free(SSH_BIND *ssh_bind){
if (ssh_bind == NULL) {
return;
}
if (ssh_bind->bindfd >= 0) {
close(ssh_bind->bindfd);
}
ssh_bind->bindfd = -1;
if (ssh_bind->options) {
ssh_options_free(ssh_bind->options);
}
SAFE_FREE(ssh_bind);
}
extern char *supported_methods[];
static int server_set_kex(ssh_session session) {
KEX *server = &session->server_kex;
ssh_options options = session->options;
int i, j;
char *wanted;
ZERO_STRUCTP(server);
/*
* The program might ask for a specific cookie to be sent. Useful for server
* debugging
*/
if (options->wanted_cookie) {
memcpy(server->cookie, options->wanted_cookie, 16);
} else {
ssh_get_random(server->cookie, 16, 0);
}
if (session->dsa_key != NULL && session->rsa_key != NULL) {
if (ssh_options_set(options, SSH_OPTIONS_SERVER_HOSTKEY,
"ssh-dss,ssh-rsa") < 0) {
return -1;
}
} else if (session->dsa_key != NULL) {
if (ssh_options_set(options, SSH_OPTIONS_SERVER_HOSTKEY, "ssh-dss") < 0) {
return -1;
}
} else {
if (ssh_options_set(options, SSH_OPTIONS_SERVER_HOSTKEY, "ssh-rsa") < 0) {
return -1;
}
}
server->methods = malloc(10 * sizeof(char **));
if (server->methods == NULL) {
return -1;
}
for (i = 0; i < 10; i++) {
if ((wanted = options->wanted_methods[i]) == NULL) {
wanted = supported_methods[i];
}
server->methods[i] = strdup(wanted);
if (server->methods[i] == NULL) {
for (j = i - 1; j <= 0; j--) {
SAFE_FREE(server->methods[j]);
}
SAFE_FREE(server->methods);
return -1;
}
}
return 0;
}
static int dh_handshake_server(ssh_session session) {
ssh_string e;
ssh_string f;
ssh_string pubkey;
ssh_string sign;
ssh_public_key pub;
ssh_private_key prv;
if (packet_wait(session, SSH2_MSG_KEXDH_INIT, 1) != SSH_OK) {
return -1;
}
e = buffer_get_ssh_string(session->in_buffer);
if (e == NULL) {
ssh_set_error(session, SSH_FATAL, "No e number in client request");
return -1;
}
if (dh_import_e(session, e) < 0) {
ssh_set_error(session, SSH_FATAL, "Cannot import e number");
string_free(e);
return -1;
}
string_free(e);
if (dh_generate_y(session) < 0) {
ssh_set_error(session, SSH_FATAL, "Could not create y number");
return -1;
}
if (dh_generate_f(session) < 0) {
ssh_set_error(session, SSH_FATAL, "Could not create f number");
return -1;
}
f = dh_get_f(session);
if (f == NULL) {
ssh_set_error(session, SSH_FATAL, "Could not get the f number");
return -1;
}
switch(session->hostkeys){
case TYPE_DSS:
prv = session->dsa_key;
break;
case TYPE_RSA:
prv = session->rsa_key;
break;
default:
prv = NULL;
}
pub = publickey_from_privatekey(prv);
if (pub == NULL) {
ssh_set_error(session, SSH_FATAL,
"Could not get the public key from the private key");
string_free(f);
return -1;
}
pubkey = publickey_to_string(pub);
publickey_free(pub);
if (pubkey == NULL) {
ssh_set_error(session, SSH_FATAL, "Not enough space");
string_free(f);
return -1;
}
dh_import_pubkey(session, pubkey);
if (dh_build_k(session) < 0) {
ssh_set_error(session, SSH_FATAL, "Could not import the public key");
string_free(f);
return -1;
}
if (make_sessionid(session) != SSH_OK) {
ssh_set_error(session, SSH_FATAL, "Could not create a session id");
string_free(f);
return -1;
}
sign = ssh_sign_session_id(session, prv);
if (sign == NULL) {
ssh_set_error(session, SSH_FATAL, "Could not sign the session id");
string_free(f);
return -1;
}
/* Free private keys as they should not be readable after this point */
if (session->rsa_key) {
privatekey_free(session->rsa_key);
session->rsa_key = NULL;
}
if (session->dsa_key) {
privatekey_free(session->dsa_key);
session->dsa_key = NULL;
}
if (buffer_add_u8(session->out_buffer, SSH2_MSG_KEXDH_REPLY) < 0 ||
buffer_add_ssh_string(session->out_buffer, pubkey) < 0 ||
buffer_add_ssh_string(session->out_buffer, f) < 0 ||
buffer_add_ssh_string(session->out_buffer, sign) < 0) {
ssh_set_error(session, SSH_FATAL, "Not enough space");
buffer_reinit(session->out_buffer);
string_free(f);
string_free(sign);
return -1;
}
string_free(f);
string_free(sign);
if (packet_send(session) != SSH_OK) {
return -1;
}
if (buffer_add_u8(session->out_buffer, SSH2_MSG_NEWKEYS) < 0) {
buffer_reinit(session->out_buffer);
return -1;
}
if (packet_send(session) != SSH_OK) {
return -1;
}
ssh_log(session, SSH_LOG_PACKET, "SSH_MSG_NEWKEYS sent");
if (packet_wait(session, SSH2_MSG_NEWKEYS, 1) != SSH_OK) {
return -1;
}
ssh_log(session, SSH_LOG_PACKET, "Got SSH_MSG_NEWKEYS");
if (generate_session_keys(session) < 0) {
return -1;
}
/*
* Once we got SSH2_MSG_NEWKEYS we can switch next_crypto and
* current_crypto
*/
if (session->current_crypto) {
crypto_free(session->current_crypto);
}
/* FIXME TODO later, include a function to change keys */
session->current_crypto = session->next_crypto;
session->next_crypto = crypto_new();
if (session->next_crypto == NULL) {
return -1;
}
return 0;
}
/* Do the banner and key exchange */
int ssh_accept(ssh_session session) {
if (ssh_send_banner(session, 1) < 0) {
return -1;
}
session->alive = 1;
session->clientbanner = ssh_get_banner(session);
if (session->clientbanner == NULL) {
return -1;
}
if (server_set_kex(session) < 0) {
return -1;
}
if (ssh_send_kex(session, 1) < 0) {
return -1;
}
if (ssh_get_kex(session,1) < 0) {
return -1;
}
ssh_list_kex(session, &session->client_kex);
crypt_set_algorithms_server(session);
if (dh_handshake_server(session) < 0) {
return -1;
}
session->connected = 1;
return 0;
}
/**
* @brief Blocking write on channel for stderr.
*
* @param channel The channel to write to.
*
* @param data A pointer to the data to write.
*
* @param len The length of the buffer to write to.
*
* @return The number of bytes written, SSH_ERROR on error.
*
* @see channel_read()
*/
int channel_write_stderr(ssh_channel channel, const void *data, uint32_t len) {
return channel_write_common(channel, data, len, 1);
}
/* messages */
static int ssh_message_auth_reply_default(ssh_message msg,int partial) {
ssh_session session = msg->session;
char methods_c[128] = {0};
ssh_string methods = NULL;
int rc = SSH_ERROR;
enter_function();
if (buffer_add_u8(session->out_buffer, SSH2_MSG_USERAUTH_FAILURE) < 0) {
return rc;
}
if (session->auth_methods == 0) {
session->auth_methods = SSH_AUTH_METHOD_PUBLICKEY | SSH_AUTH_METHOD_PASSWORD;
}
if (session->auth_methods & SSH_AUTH_METHOD_PUBLICKEY) {
strcat(methods_c, "publickey,");
}
if (session->auth_methods & SSH_AUTH_METHOD_INTERACTIVE) {
strcat(methods_c, "keyboard-interactive,");
}
if (session->auth_methods & SSH_AUTH_METHOD_PASSWORD) {
strcat(methods_c, "password,");
}
if (session->auth_methods & SSH_AUTH_METHOD_HOSTBASED) {
strcat(methods_c, "hostbased,");
}
/* Strip the comma. */
methods_c[strlen(methods_c) - 1] = '\0'; // strip the comma. We are sure there is at
ssh_log(session, SSH_LOG_PACKET,
"Sending a auth failure. methods that can continue: %s", methods_c);
methods = string_from_char(methods_c);
if (methods == NULL) {
goto error;
}
if (buffer_add_ssh_string(msg->session->out_buffer, methods) < 0) {
goto error;
}
if (partial) {
if (buffer_add_u8(session->out_buffer, 1) < 0) {
goto error;
}
} else {
if (buffer_add_u8(session->out_buffer, 0) < 0) {
goto error;
}
}
rc = packet_send(msg->session);
error:
string_free(methods);
leave_function();
return rc;
}
static int ssh_message_channel_request_open_reply_default(ssh_message msg) {
ssh_log(msg->session, SSH_LOG_FUNCTIONS, "Refusing a channel");
if (buffer_add_u8(msg->session->out_buffer
, SSH2_MSG_CHANNEL_OPEN_FAILURE) < 0) {
goto error;
}
if (buffer_add_u32(msg->session->out_buffer,
htonl(msg->channel_request_open.sender)) < 0) {
goto error;
}
if (buffer_add_u32(msg->session->out_buffer,
htonl(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED)) < 0) {
goto error;
}
/* reason is an empty string */
if (buffer_add_u32(msg->session->out_buffer, 0) < 0) {
goto error;
}
/* language too */
if (buffer_add_u32(msg->session->out_buffer, 0) < 0) {
goto error;
}
return packet_send(msg->session);
error:
return SSH_ERROR;
}
static int ssh_message_channel_request_reply_default(ssh_message msg) {
uint32_t channel;
if (msg->channel_request.want_reply) {
channel = msg->channel_request.channel->remote_channel;
ssh_log(msg->session, SSH_LOG_PACKET,
"Sending a default channel_request denied to channel %d", channel);
if (buffer_add_u8(msg->session->out_buffer, SSH2_MSG_CHANNEL_FAILURE) < 0) {
return SSH_ERROR;
}
if (buffer_add_u32(msg->session->out_buffer, htonl(channel)) < 0) {
return SSH_ERROR;
}
return packet_send(msg->session);
}
ssh_log(msg->session, SSH_LOG_PACKET,
"The client doesn't want to know the request failed!");
return SSH_OK;
}
static int ssh_message_service_request_reply_default(ssh_message msg) {
/* The only return code accepted by specifications are success or disconnect */
return ssh_message_service_reply_success(msg);
}
int ssh_message_service_reply_success(ssh_message msg) {
struct ssh_string_struct *service;
ssh_session session=msg->session;
if (msg == NULL) {
return SSH_ERROR;
}
ssh_log(session, SSH_LOG_PACKET,
"Sending a SERVICE_ACCEPT for service %s", msg->service_request.service);
if (buffer_add_u8(session->out_buffer, SSH2_MSG_SERVICE_ACCEPT) < 0) {
return -1;
}
service=string_from_char(msg->service_request.service);
if (buffer_add_ssh_string(session->out_buffer, service) < 0) {
string_free(service);
return -1;
}
string_free(service);
return packet_send(msg->session);
}
int ssh_message_reply_default(ssh_message msg) {
if (msg == NULL) {
return -1;
}
switch(msg->type) {
case SSH_REQUEST_AUTH:
return ssh_message_auth_reply_default(msg, 0);
case SSH_REQUEST_CHANNEL_OPEN:
return ssh_message_channel_request_open_reply_default(msg);
case SSH_REQUEST_CHANNEL:
return ssh_message_channel_request_reply_default(msg);
case SSH_REQUEST_SERVICE:
return ssh_message_service_request_reply_default(msg);
default:
ssh_log(msg->session, SSH_LOG_PACKET,
"Don't know what to default reply to %d type",
msg->type);
break;
}
return -1;
}
char *ssh_message_service_service(ssh_message msg){
if (msg == NULL) {
return NULL;
}
return msg->service_request.service;
}
char *ssh_message_auth_user(ssh_message msg) {
if (msg == NULL) {
return NULL;
}
return msg->auth_request.username;
}
char *ssh_message_auth_password(ssh_message msg){
if (msg == NULL) {
return NULL;
}
return msg->auth_request.password;
}
/* Get the publickey of an auth request */
ssh_public_key ssh_message_auth_publickey(ssh_message msg){
if (msg == NULL) {
return NULL;
}
return msg->auth_request.public_key;
}
int ssh_message_auth_set_methods(ssh_message msg, int methods) {
if (msg == NULL || msg->session == NULL) {
return -1;
}
msg->session->auth_methods = methods;
return 0;
}
int ssh_message_auth_reply_success(ssh_message msg, int partial) {
if (msg == NULL) {
return SSH_ERROR;
}
if (partial) {
return ssh_message_auth_reply_default(msg, partial);
}
if (buffer_add_u8(msg->session->out_buffer,SSH2_MSG_USERAUTH_SUCCESS) < 0) {
return SSH_ERROR;
}
return packet_send(msg->session);
}
/* Answer OK to a pubkey auth request */
int ssh_message_auth_reply_pk_ok(ssh_message msg, ssh_string algo, ssh_string pubkey) {
if (msg == NULL) {
return SSH_ERROR;
}
if (buffer_add_u8(msg->session->out_buffer, SSH2_MSG_USERAUTH_PK_OK) < 0 ||
buffer_add_ssh_string(msg->session->out_buffer, algo) < 0 ||
buffer_add_ssh_string(msg->session->out_buffer, pubkey) < 0) {
return SSH_ERROR;
}
return packet_send(msg->session);
}
char *ssh_message_channel_request_open_originator(ssh_message msg){
return msg->channel_request_open.originator;
}
int ssh_message_channel_request_open_originator_port(ssh_message msg){
return msg->channel_request_open.originator_port;
}
char *ssh_message_channel_request_open_destination(ssh_message msg){
return msg->channel_request_open.destination;
}
int ssh_message_channel_request_open_destination_port(ssh_message msg){
return msg->channel_request_open.destination_port;
}
ssh_channel ssh_message_channel_request_channel(ssh_message msg){
return msg->channel_request.channel;
}
char *ssh_message_channel_request_pty_term(ssh_message msg){
return msg->channel_request.TERM;
}
int ssh_message_channel_request_pty_width(ssh_message msg){
return msg->channel_request.width;
}
int ssh_message_channel_request_pty_height(ssh_message msg){
return msg->channel_request.height;
}
int ssh_message_channel_request_pty_pxwidth(ssh_message msg){
return msg->channel_request.pxwidth;
}
int ssh_message_channel_request_pty_pxheight(ssh_message msg){
return msg->channel_request.pxheight;
}
char *ssh_message_channel_request_env_name(ssh_message msg){
return msg->channel_request.var_name;
}
char *ssh_message_channel_request_env_value(ssh_message msg){
return msg->channel_request.var_value;
}
char *ssh_message_channel_request_command(ssh_message msg){
return msg->channel_request.command;
}
char *ssh_message_channel_request_subsystem(ssh_message msg){
return msg->channel_request.subsystem;
}
/** @brief defines the SSH_MESSAGE callback
* @param session the current ssh session
* @param ssh_message_callback a function pointer to a callback taking the
* current ssh session and received message as parameters. the function returns
* 0 if the message has been parsed and treated sucessfuly, 1 otherwise (libssh
* must take care of the response).
*/
void ssh_set_message_callback(ssh_session session,
int(*ssh_message_callback)(ssh_session session, ssh_message msg)){
session->ssh_message_callback=ssh_message_callback;
}
int ssh_execute_message_callbacks(ssh_session session){
ssh_message msg=NULL;
int ret;
if(!session->ssh_message_list)
return SSH_OK;
if(session->ssh_message_callback){
while((msg=ssh_list_get_head(ssh_message , session->ssh_message_list)) != NULL){
ret=session->ssh_message_callback(session,msg);
if(ret==1){
ret = ssh_message_reply_default(msg);
if(ret != SSH_OK)
return ret;
}
}
} else {
while((msg=ssh_list_get_head(ssh_message , session->ssh_message_list)) != NULL){
ret = ssh_message_reply_default(msg);
if(ret != SSH_OK)
return ret;
}
}
return SSH_OK;
}
/** @}
*/
/* vim: set ts=2 sw=2 et cindent: */