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freebsd/crypto/openssh/ssh.c

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/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
* All rights reserved
* Created: Sat Mar 18 16:36:11 1995 ylo
* Ssh client program. This program can be used to log into a remote machine.
* The software supports strong authentication, encryption, and forwarding
* of X11, TCP/IP, and authentication connections.
*
* Modified to work with SSL by Niels Provos <provos@citi.umich.edu> in Canada.
*
* $FreeBSD$
*/
#include "includes.h"
RCSID("$Id: ssh.c,v 1.40 2000/02/20 20:05:19 markus Exp $");
#include "xmalloc.h"
#include "ssh.h"
#include "packet.h"
#include "buffer.h"
#include "authfd.h"
#include "readconf.h"
#include "uidswap.h"
/* Flag indicating whether IPv4 or IPv6. This can be set on the command line.
Default value is AF_UNSPEC means both IPv4 and IPv6. */
int IPv4or6 = AF_UNSPEC;
/* Flag indicating whether debug mode is on. This can be set on the command line. */
int debug_flag = 0;
int tty_flag = 0;
/*
* Flag indicating that nothing should be read from stdin. This can be set
* on the command line.
*/
int stdin_null_flag = 0;
/*
* Flag indicating that ssh should fork after authentication. This is useful
* so that the pasphrase can be entered manually, and then ssh goes to the
* background.
*/
int fork_after_authentication_flag = 0;
/*
* General data structure for command line options and options configurable
* in configuration files. See readconf.h.
*/
Options options;
/*
* Name of the host we are connecting to. This is the name given on the
* command line, or the HostName specified for the user-supplied name in a
* configuration file.
*/
char *host;
/* socket address the host resolves to */
struct sockaddr_storage hostaddr;
/*
* Flag to indicate that we have received a window change signal which has
* not yet been processed. This will cause a message indicating the new
* window size to be sent to the server a little later. This is volatile
* because this is updated in a signal handler.
*/
volatile int received_window_change_signal = 0;
/* Value of argv[0] (set in the main program). */
char *av0;
/* Flag indicating whether we have a valid host private key loaded. */
int host_private_key_loaded = 0;
/* Host private key. */
RSA *host_private_key = NULL;
/* Original real UID. */
uid_t original_real_uid;
/* Prints a help message to the user. This function never returns. */
void
usage()
{
fprintf(stderr, "Usage: %s [options] host [command]\n", av0);
fprintf(stderr, "Options:\n");
fprintf(stderr, " -l user Log in using this user name.\n");
fprintf(stderr, " -n Redirect input from /dev/null.\n");
fprintf(stderr, " -a Disable authentication agent forwarding.\n");
#ifdef AFS
fprintf(stderr, " -k Disable Kerberos ticket and AFS token forwarding.\n");
#endif /* AFS */
fprintf(stderr, " -x Disable X11 connection forwarding.\n");
fprintf(stderr, " -i file Identity for RSA authentication (default: ~/.ssh/identity).\n");
fprintf(stderr, " -t Tty; allocate a tty even if command is given.\n");
fprintf(stderr, " -v Verbose; display verbose debugging messages.\n");
fprintf(stderr, " -V Display version number only.\n");
fprintf(stderr, " -P Don't allocate a privileged port.\n");
fprintf(stderr, " -q Quiet; don't display any warning messages.\n");
fprintf(stderr, " -f Fork into background after authentication.\n");
fprintf(stderr, " -e char Set escape character; ``none'' = disable (default: ~).\n");
fprintf(stderr, " -c cipher Select encryption algorithm: "
"``3des'', "
"``blowfish''\n");
fprintf(stderr, " -p port Connect to this port. Server must be on the same port.\n");
fprintf(stderr, " -L listen-port:host:port Forward local port to remote address\n");
fprintf(stderr, " -R listen-port:host:port Forward remote port to local address\n");
fprintf(stderr, " These cause %s to listen for connections on a port, and\n", av0);
fprintf(stderr, " forward them to the other side by connecting to host:port.\n");
fprintf(stderr, " -C Enable compression.\n");
fprintf(stderr, " -g Allow remote hosts to connect to forwarded ports.\n");
fprintf(stderr, " -4 Use IPv4 only.\n");
fprintf(stderr, " -6 Use IPv6 only.\n");
fprintf(stderr, " -o 'option' Process the option as if it was read from a configuration file.\n");
exit(1);
}
/*
* Connects to the given host using rsh (or prints an error message and exits
* if rsh is not available). This function never returns.
*/
void
rsh_connect(char *host, char *user, Buffer * command)
{
char *args[10];
int i;
log("Using rsh. WARNING: Connection will not be encrypted.");
/* Build argument list for rsh. */
i = 0;
#ifndef _PATH_RSH
#define _PATH_RSH "/usr/bin/rsh"
#endif
args[i++] = _PATH_RSH;
/* host may have to come after user on some systems */
args[i++] = host;
if (user) {
args[i++] = "-l";
args[i++] = user;
}
if (buffer_len(command) > 0) {
buffer_append(command, "\0", 1);
args[i++] = buffer_ptr(command);
}
args[i++] = NULL;
if (debug_flag) {
for (i = 0; args[i]; i++) {
if (i != 0)
fprintf(stderr, " ");
fprintf(stderr, "%s", args[i]);
}
fprintf(stderr, "\n");
}
execv(_PATH_RSH, args);
perror(_PATH_RSH);
exit(1);
}
/*
* Main program for the ssh client.
*/
int
main(int ac, char **av)
{
int i, opt, optind, type, exit_status, ok, authfd;
u_short fwd_port, fwd_host_port;
char *optarg, *cp, buf[256];
Buffer command;
struct winsize ws;
struct stat st;
struct passwd *pw, pwcopy;
int interactive = 0, dummy;
uid_t original_effective_uid;
int plen;
/*
* Save the original real uid. It will be needed later (uid-swapping
* may clobber the real uid).
*/
original_real_uid = getuid();
original_effective_uid = geteuid();
/* If we are installed setuid root be careful to not drop core. */
if (original_real_uid != original_effective_uid) {
struct rlimit rlim;
rlim.rlim_cur = rlim.rlim_max = 0;
if (setrlimit(RLIMIT_CORE, &rlim) < 0)
fatal("setrlimit failed: %.100s", strerror(errno));
}
/*
* Use uid-swapping to give up root privileges for the duration of
* option processing. We will re-instantiate the rights when we are
* ready to create the privileged port, and will permanently drop
* them when the port has been created (actually, when the connection
* has been made, as we may need to create the port several times).
*/
temporarily_use_uid(original_real_uid);
/*
* Set our umask to something reasonable, as some files are created
* with the default umask. This will make them world-readable but
* writable only by the owner, which is ok for all files for which we
* don't set the modes explicitly.
*/
umask(022);
/* Save our own name. */
av0 = av[0];
/* Initialize option structure to indicate that no values have been set. */
initialize_options(&options);
/* Parse command-line arguments. */
host = NULL;
/* If program name is not one of the standard names, use it as host name. */
if (strchr(av0, '/'))
cp = strrchr(av0, '/') + 1;
else
cp = av0;
if (strcmp(cp, "rsh") != 0 && strcmp(cp, "ssh") != 0 &&
strcmp(cp, "rlogin") != 0 && strcmp(cp, "slogin") != 0)
host = cp;
for (optind = 1; optind < ac; optind++) {
if (av[optind][0] != '-') {
if (host)
break;
if ((cp = strchr(av[optind], '@'))) {
if(cp == av[optind])
usage();
options.user = av[optind];
*cp = '\0';
host = ++cp;
} else
host = av[optind];
continue;
}
opt = av[optind][1];
if (!opt)
usage();
if (strchr("eilcpLRo", opt)) { /* options with arguments */
optarg = av[optind] + 2;
if (strcmp(optarg, "") == 0) {
if (optind >= ac - 1)
usage();
optarg = av[++optind];
}
} else {
if (av[optind][2])
usage();
optarg = NULL;
}
switch (opt) {
case '4':
IPv4or6 = AF_INET;
break;
case '6':
IPv4or6 = AF_INET6;
break;
case 'n':
stdin_null_flag = 1;
break;
case 'f':
fork_after_authentication_flag = 1;
stdin_null_flag = 1;
break;
case 'x':
options.forward_x11 = 0;
break;
case 'X':
options.forward_x11 = 1;
break;
case 'g':
options.gateway_ports = 1;
break;
case 'P':
options.use_privileged_port = 0;
break;
case 'a':
options.forward_agent = 0;
break;
#ifdef AFS
case 'k':
options.kerberos_tgt_passing = 0;
options.afs_token_passing = 0;
break;
#endif
case 'i':
if (stat(optarg, &st) < 0) {
fprintf(stderr, "Warning: Identity file %s does not exist.\n",
optarg);
break;
}
if (options.num_identity_files >= SSH_MAX_IDENTITY_FILES)
fatal("Too many identity files specified (max %d)",
SSH_MAX_IDENTITY_FILES);
options.identity_files[options.num_identity_files++] =
xstrdup(optarg);
break;
case 't':
tty_flag = 1;
break;
case 'v':
case 'V':
fprintf(stderr, "SSH Version %s, protocol version %d.%d.\n",
SSH_VERSION, PROTOCOL_MAJOR, PROTOCOL_MINOR);
fprintf(stderr, "Compiled with SSL.\n");
if (opt == 'V')
exit(0);
debug_flag = 1;
options.log_level = SYSLOG_LEVEL_DEBUG;
break;
case 'q':
options.log_level = SYSLOG_LEVEL_QUIET;
break;
case 'e':
if (optarg[0] == '^' && optarg[2] == 0 &&
(unsigned char) optarg[1] >= 64 && (unsigned char) optarg[1] < 128)
options.escape_char = (unsigned char) optarg[1] & 31;
else if (strlen(optarg) == 1)
options.escape_char = (unsigned char) optarg[0];
else if (strcmp(optarg, "none") == 0)
options.escape_char = -2;
else {
fprintf(stderr, "Bad escape character '%s'.\n", optarg);
exit(1);
}
break;
case 'c':
options.cipher = cipher_number(optarg);
if (options.cipher == -1) {
fprintf(stderr, "Unknown cipher type '%s'\n", optarg);
exit(1);
}
break;
case 'p':
options.port = atoi(optarg);
break;
case 'l':
options.user = optarg;
break;
case 'R':
if (sscanf(optarg, "%hu/%255[^/]/%hu", &fwd_port, buf,
&fwd_host_port) != 3 &&
sscanf(optarg, "%hu:%255[^:]:%hu", &fwd_port, buf,
&fwd_host_port) != 3) {
fprintf(stderr, "Bad forwarding specification '%s'.\n", optarg);
usage();
/* NOTREACHED */
}
add_remote_forward(&options, fwd_port, buf, fwd_host_port);
break;
case 'L':
if (sscanf(optarg, "%hu/%255[^/]/%hu", &fwd_port, buf,
&fwd_host_port) != 3 &&
sscanf(optarg, "%hu:%255[^:]:%hu", &fwd_port, buf,
&fwd_host_port) != 3) {
fprintf(stderr, "Bad forwarding specification '%s'.\n", optarg);
usage();
/* NOTREACHED */
}
add_local_forward(&options, fwd_port, buf, fwd_host_port);
break;
case 'C':
options.compression = 1;
break;
case 'o':
dummy = 1;
if (process_config_line(&options, host ? host : "", optarg,
"command-line", 0, &dummy) != 0)
exit(1);
break;
default:
usage();
}
}
/* Check that we got a host name. */
if (!host)
usage();
/* check if RSA support exists */
if (rsa_alive() == 0) {
extern char *__progname;
fprintf(stderr,
"%s: no RSA support in libssl and libcrypto. See ssl(8).\n",
__progname);
exit(1);
}
/* Initialize the command to execute on remote host. */
buffer_init(&command);
/*
* Save the command to execute on the remote host in a buffer. There
* is no limit on the length of the command, except by the maximum
* packet size. Also sets the tty flag if there is no command.
*/
if (optind == ac) {
/* No command specified - execute shell on a tty. */
tty_flag = 1;
} else {
/* A command has been specified. Store it into the
buffer. */
for (i = optind; i < ac; i++) {
if (i > optind)
buffer_append(&command, " ", 1);
buffer_append(&command, av[i], strlen(av[i]));
}
}
/* Cannot fork to background if no command. */
if (fork_after_authentication_flag && buffer_len(&command) == 0)
fatal("Cannot fork into background without a command to execute.");
/* Allocate a tty by default if no command specified. */
if (buffer_len(&command) == 0)
tty_flag = 1;
/* Do not allocate a tty if stdin is not a tty. */
if (!isatty(fileno(stdin))) {
if (tty_flag)
fprintf(stderr, "Pseudo-terminal will not be allocated because stdin is not a terminal.\n");
tty_flag = 0;
}
/* Get user data. */
pw = getpwuid(original_real_uid);
if (!pw) {
fprintf(stderr, "You don't exist, go away!\n");
exit(1);
}
/* Take a copy of the returned structure. */
memset(&pwcopy, 0, sizeof(pwcopy));
pwcopy.pw_name = xstrdup(pw->pw_name);
pwcopy.pw_passwd = xstrdup(pw->pw_passwd);
pwcopy.pw_uid = pw->pw_uid;
pwcopy.pw_gid = pw->pw_gid;
pwcopy.pw_dir = xstrdup(pw->pw_dir);
pwcopy.pw_shell = xstrdup(pw->pw_shell);
pw = &pwcopy;
/* Initialize "log" output. Since we are the client all output
actually goes to the terminal. */
log_init(av[0], options.log_level, SYSLOG_FACILITY_USER, 0);
/* Read per-user configuration file. */
snprintf(buf, sizeof buf, "%.100s/%.100s", pw->pw_dir, SSH_USER_CONFFILE);
read_config_file(buf, host, &options);
/* Read systemwide configuration file. */
read_config_file(HOST_CONFIG_FILE, host, &options);
/* Fill configuration defaults. */
fill_default_options(&options);
/* reinit */
log_init(av[0], options.log_level, SYSLOG_FACILITY_USER, 0);
if (options.user == NULL)
options.user = xstrdup(pw->pw_name);
if (options.hostname != NULL)
host = options.hostname;
/* Find canonic host name. */
if (strchr(host, '.') == 0) {
struct addrinfo hints;
struct addrinfo *ai = NULL;
int errgai;
memset(&hints, 0, sizeof(hints));
hints.ai_family = IPv4or6;
hints.ai_flags = AI_CANONNAME;
hints.ai_socktype = SOCK_STREAM;
errgai = getaddrinfo(host, NULL, &hints, &ai);
if (errgai == 0) {
if (ai->ai_canonname != NULL)
host = xstrdup(ai->ai_canonname);
freeaddrinfo(ai);
}
}
/* Disable rhosts authentication if not running as root. */
if (original_effective_uid != 0 || !options.use_privileged_port) {
options.rhosts_authentication = 0;
options.rhosts_rsa_authentication = 0;
}
/*
* If using rsh has been selected, exec it now (without trying
* anything else). Note that we must release privileges first.
*/
if (options.use_rsh) {
/*
* Restore our superuser privileges. This must be done
* before permanently setting the uid.
*/
restore_uid();
/* Switch to the original uid permanently. */
permanently_set_uid(original_real_uid);
/* Execute rsh. */
rsh_connect(host, options.user, &command);
fatal("rsh_connect returned");
}
/* Restore our superuser privileges. */
restore_uid();
/*
* Open a connection to the remote host. This needs root privileges
* if rhosts_{rsa_}authentication is enabled.
*/
ok = ssh_connect(host, &hostaddr, options.port,
options.connection_attempts,
!options.rhosts_authentication &&
!options.rhosts_rsa_authentication,
original_real_uid,
options.proxy_command);
/*
* If we successfully made the connection, load the host private key
* in case we will need it later for combined rsa-rhosts
* authentication. This must be done before releasing extra
* privileges, because the file is only readable by root.
*/
if (ok) {
host_private_key = RSA_new();
if (load_private_key(HOST_KEY_FILE, "", host_private_key, NULL))
host_private_key_loaded = 1;
}
/*
* Get rid of any extra privileges that we may have. We will no
* longer need them. Also, extra privileges could make it very hard
* to read identity files and other non-world-readable files from the
* user's home directory if it happens to be on a NFS volume where
* root is mapped to nobody.
*/
/*
* Note that some legacy systems need to postpone the following call
* to permanently_set_uid() until the private hostkey is destroyed
* with RSA_free(). Otherwise the calling user could ptrace() the
* process, read the private hostkey and impersonate the host.
* OpenBSD does not allow ptracing of setuid processes.
*/
permanently_set_uid(original_real_uid);
/*
* Now that we are back to our own permissions, create ~/.ssh
* directory if it doesn\'t already exist.
*/
snprintf(buf, sizeof buf, "%.100s/%.100s", pw->pw_dir, SSH_USER_DIR);
if (stat(buf, &st) < 0)
if (mkdir(buf, 0755) < 0)
error("Could not create directory '%.200s'.", buf);
/* Check if the connection failed, and try "rsh" if appropriate. */
if (!ok) {
if (options.port != 0)
log("Secure connection to %.100s on port %hu refused%.100s.",
host, options.port,
options.fallback_to_rsh ? "; reverting to insecure method" : "");
else
log("Secure connection to %.100s refused%.100s.", host,
options.fallback_to_rsh ? "; reverting to insecure method" : "");
if (options.fallback_to_rsh) {
rsh_connect(host, options.user, &command);
fatal("rsh_connect returned");
}
exit(1);
}
/* Expand ~ in options.identity_files. */
for (i = 0; i < options.num_identity_files; i++)
options.identity_files[i] =
tilde_expand_filename(options.identity_files[i], original_real_uid);
/* Expand ~ in known host file names. */
options.system_hostfile = tilde_expand_filename(options.system_hostfile,
original_real_uid);
options.user_hostfile = tilde_expand_filename(options.user_hostfile,
original_real_uid);
/* Log into the remote system. This never returns if the login fails. */
ssh_login(host_private_key_loaded, host_private_key,
host, (struct sockaddr *)&hostaddr, original_real_uid);
/* We no longer need the host private key. Clear it now. */
if (host_private_key_loaded)
RSA_free(host_private_key); /* Destroys contents safely */
/* Close connection cleanly after attack. */
cipher_attack_detected = packet_disconnect;
/* Enable compression if requested. */
if (options.compression) {
debug("Requesting compression at level %d.", options.compression_level);
if (options.compression_level < 1 || options.compression_level > 9)
fatal("Compression level must be from 1 (fast) to 9 (slow, best).");
/* Send the request. */
packet_start(SSH_CMSG_REQUEST_COMPRESSION);
packet_put_int(options.compression_level);
packet_send();
packet_write_wait();
type = packet_read(&plen);
if (type == SSH_SMSG_SUCCESS)
packet_start_compression(options.compression_level);
else if (type == SSH_SMSG_FAILURE)
log("Warning: Remote host refused compression.");
else
packet_disconnect("Protocol error waiting for compression response.");
}
/* Allocate a pseudo tty if appropriate. */
if (tty_flag) {
debug("Requesting pty.");
/* Start the packet. */
packet_start(SSH_CMSG_REQUEST_PTY);
/* Store TERM in the packet. There is no limit on the
length of the string. */
cp = getenv("TERM");
if (!cp)
cp = "";
packet_put_string(cp, strlen(cp));
/* Store window size in the packet. */
if (ioctl(fileno(stdin), TIOCGWINSZ, &ws) < 0)
memset(&ws, 0, sizeof(ws));
packet_put_int(ws.ws_row);
packet_put_int(ws.ws_col);
packet_put_int(ws.ws_xpixel);
packet_put_int(ws.ws_ypixel);
/* Store tty modes in the packet. */
tty_make_modes(fileno(stdin));
/* Send the packet, and wait for it to leave. */
packet_send();
packet_write_wait();
/* Read response from the server. */
type = packet_read(&plen);
if (type == SSH_SMSG_SUCCESS)
interactive = 1;
else if (type == SSH_SMSG_FAILURE)
log("Warning: Remote host failed or refused to allocate a pseudo tty.");
else
packet_disconnect("Protocol error waiting for pty request response.");
}
/* Request X11 forwarding if enabled and DISPLAY is set. */
if (options.forward_x11 && getenv("DISPLAY") != NULL) {
char line[512], proto[512], data[512];
FILE *f;
int forwarded = 0, got_data = 0, i;
#ifdef XAUTH_PATH
/* Try to get Xauthority information for the display. */
snprintf(line, sizeof line, "%.100s list %.200s 2>/dev/null",
XAUTH_PATH, getenv("DISPLAY"));
f = popen(line, "r");
if (f && fgets(line, sizeof(line), f) &&
sscanf(line, "%*s %s %s", proto, data) == 2)
got_data = 1;
if (f)
pclose(f);
#endif /* XAUTH_PATH */
/*
* If we didn't get authentication data, just make up some
* data. The forwarding code will check the validity of the
* response anyway, and substitute this data. The X11
* server, however, will ignore this fake data and use
* whatever authentication mechanisms it was using otherwise
* for the local connection.
*/
if (!got_data) {
u_int32_t rand = 0;
strlcpy(proto, "MIT-MAGIC-COOKIE-1", sizeof proto);
for (i = 0; i < 16; i++) {
if (i % 4 == 0)
rand = arc4random();
snprintf(data + 2 * i, sizeof data - 2 * i, "%02x", rand & 0xff);
rand >>= 8;
}
}
/*
* Got local authentication reasonable information. Request
* forwarding with authentication spoofing.
*/
debug("Requesting X11 forwarding with authentication spoofing.");
x11_request_forwarding_with_spoofing(proto, data);
/* Read response from the server. */
type = packet_read(&plen);
if (type == SSH_SMSG_SUCCESS) {
forwarded = 1;
interactive = 1;
} else if (type == SSH_SMSG_FAILURE)
log("Warning: Remote host denied X11 forwarding.");
else
packet_disconnect("Protocol error waiting for X11 forwarding");
}
/* Tell the packet module whether this is an interactive session. */
packet_set_interactive(interactive, options.keepalives);
/* Clear agent forwarding if we don\'t have an agent. */
authfd = ssh_get_authentication_socket();
if (authfd < 0)
options.forward_agent = 0;
else
ssh_close_authentication_socket(authfd);
/* Request authentication agent forwarding if appropriate. */
if (options.forward_agent) {
debug("Requesting authentication agent forwarding.");
auth_request_forwarding();
/* Read response from the server. */
type = packet_read(&plen);
packet_integrity_check(plen, 0, type);
if (type != SSH_SMSG_SUCCESS)
log("Warning: Remote host denied authentication agent forwarding.");
}
/* Initiate local TCP/IP port forwardings. */
for (i = 0; i < options.num_local_forwards; i++) {
debug("Connections to local port %d forwarded to remote address %.200s:%d",
options.local_forwards[i].port,
options.local_forwards[i].host,
options.local_forwards[i].host_port);
channel_request_local_forwarding(options.local_forwards[i].port,
options.local_forwards[i].host,
options.local_forwards[i].host_port,
options.gateway_ports);
}
/* Initiate remote TCP/IP port forwardings. */
for (i = 0; i < options.num_remote_forwards; i++) {
debug("Connections to remote port %d forwarded to local address %.200s:%d",
options.remote_forwards[i].port,
options.remote_forwards[i].host,
options.remote_forwards[i].host_port);
channel_request_remote_forwarding(options.remote_forwards[i].port,
options.remote_forwards[i].host,
options.remote_forwards[i].host_port);
}
/* If requested, let ssh continue in the background. */
if (fork_after_authentication_flag)
if (daemon(1, 1) < 0)
fatal("daemon() failed: %.200s", strerror(errno));
/*
* If a command was specified on the command line, execute the
* command now. Otherwise request the server to start a shell.
*/
if (buffer_len(&command) > 0) {
int len = buffer_len(&command);
if (len > 900)
len = 900;
debug("Sending command: %.*s", len, buffer_ptr(&command));
packet_start(SSH_CMSG_EXEC_CMD);
packet_put_string(buffer_ptr(&command), buffer_len(&command));
packet_send();
packet_write_wait();
} else {
debug("Requesting shell.");
packet_start(SSH_CMSG_EXEC_SHELL);
packet_send();
packet_write_wait();
}
/* Enter the interactive session. */
exit_status = client_loop(tty_flag, tty_flag ? options.escape_char : -1);
/* Close the connection to the remote host. */
packet_close();
/* Exit with the status returned by the program on the remote side. */
exit(exit_status);
}
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