Session rekeying support in OpenSSH
Darren Tucker
dtucker at zip.com.au
Thu May 16 17:08:53 EST 2013
On Wed, May 15, 2013 at 11:37:50AM +1000, Darren Tucker wrote:
> On Mon, May 13, 2013 at 11:40:43PM +1000, Darren Tucker wrote:
> > Looks like it wouldn't be hard to add, but what problem are you trying
> > to solve?
>
> As usual it wasn't quite as simple as I initially thought, but this adds
> an optional second parameter to RekeyLimit in the client and adds
> RekeyLimit to the server. Basically you should just be able to add
> "RekeyLimit 1G 1h" to the config files on both the client and server.
>
> Patch is against -current but should apply to 6.2p1 with some fuzz.
The changes to RekeyLimit have been committed and will be in the 6.3
release. Here's the same changes against the just-released 6.2p2.
Index: clientloop.c
===================================================================
RCS file: /var/cvs/openssh/clientloop.c,v
retrieving revision 1.237
diff -u -p -r1.237 clientloop.c
--- clientloop.c 9 Jan 2013 04:55:51 -0000 1.237
+++ clientloop.c 16 May 2013 06:46:59 -0000
@@ -583,7 +583,7 @@ client_wait_until_can_do_something(fd_se
{
struct timeval tv, *tvp;
int timeout_secs;
- time_t minwait_secs = 0;
+ time_t minwait_secs = 0, server_alive_time = 0, now = time(NULL);
int ret;
/* Add any selections by the channel mechanism. */
@@ -632,12 +632,16 @@ client_wait_until_can_do_something(fd_se
*/
timeout_secs = INT_MAX; /* we use INT_MAX to mean no timeout */
- if (options.server_alive_interval > 0 && compat20)
+ if (options.server_alive_interval > 0 && compat20) {
timeout_secs = options.server_alive_interval;
+ server_alive_time = now + options.server_alive_interval;
+ }
+ if (options.rekey_interval > 0 && compat20 && !rekeying)
+ timeout_secs = MIN(timeout_secs, packet_get_rekey_timeout());
set_control_persist_exit_time();
if (control_persist_exit_time > 0) {
timeout_secs = MIN(timeout_secs,
- control_persist_exit_time - time(NULL));
+ control_persist_exit_time - now);
if (timeout_secs < 0)
timeout_secs = 0;
}
@@ -669,8 +673,15 @@ client_wait_until_can_do_something(fd_se
snprintf(buf, sizeof buf, "select: %s\r\n", strerror(errno));
buffer_append(&stderr_buffer, buf, strlen(buf));
quit_pending = 1;
- } else if (ret == 0)
- server_alive_check();
+ } else if (ret == 0) {
+ /*
+ * Timeout. Could have been either keepalive or rekeying.
+ * Keepalive we check here, rekeying is checked in clientloop.
+ */
+ if (server_alive_time != 0 && server_alive_time <= time(NULL))
+ server_alive_check();
+ }
+
}
static void
Index: monitor.c
===================================================================
RCS file: /var/cvs/openssh/monitor.c,v
retrieving revision 1.155
diff -u -p -r1.155 monitor.c
--- monitor.c 11 Dec 2012 23:44:39 -0000 1.155
+++ monitor.c 16 May 2013 06:46:59 -0000
@@ -1799,6 +1799,10 @@ monitor_apply_keystate(struct monitor *p
if (options.compression)
mm_init_compression(pmonitor->m_zlib);
+ if (options.rekey_limit || options.rekey_interval)
+ packet_set_rekey_limits((u_int32_t)options.rekey_limit,
+ (time_t)options.rekey_interval);
+
/* Network I/O buffers */
/* XXX inefficient for large buffers, need: buffer_init_from_string */
buffer_clear(packet_get_input());
Index: packet.c
===================================================================
RCS file: /var/cvs/openssh/packet.c,v
retrieving revision 1.188.2.1
diff -u -p -r1.188.2.1 packet.c
--- packet.c 10 May 2013 03:41:34 -0000 1.188.2.1
+++ packet.c 16 May 2013 06:46:59 -0000
@@ -58,6 +58,7 @@
#include <string.h>
#include <unistd.h>
#include <signal.h>
+#include <time.h>
#include "xmalloc.h"
#include "buffer.h"
@@ -165,9 +166,14 @@ struct session_state {
Newkeys *newkeys[MODE_MAX];
struct packet_state p_read, p_send;
+ /* Volume-based rekeying */
u_int64_t max_blocks_in, max_blocks_out;
u_int32_t rekey_limit;
+ /* Time-based rekeying */
+ time_t rekey_interval; /* how often in seconds */
+ time_t rekey_time; /* time of last rekeying */
+
/* Session key for protocol v1 */
u_char ssh1_key[SSH_SESSION_KEY_LENGTH];
u_int ssh1_keylen;
@@ -1009,6 +1015,7 @@ packet_send2(void)
/* after a NEWKEYS message we can send the complete queue */
if (type == SSH2_MSG_NEWKEYS) {
active_state->rekeying = 0;
+ active_state->rekey_time = time(NULL);
while ((p = TAILQ_FIRST(&active_state->outgoing))) {
type = p->type;
debug("dequeue packet: %u", type);
@@ -1933,13 +1940,33 @@ packet_need_rekeying(void)
(active_state->max_blocks_out &&
(active_state->p_send.blocks > active_state->max_blocks_out)) ||
(active_state->max_blocks_in &&
- (active_state->p_read.blocks > active_state->max_blocks_in));
+ (active_state->p_read.blocks > active_state->max_blocks_in)) ||
+ (active_state->rekey_interval != 0 && active_state->rekey_time +
+ active_state->rekey_interval <= time(NULL));
}
void
-packet_set_rekey_limit(u_int32_t bytes)
+packet_set_rekey_limits(u_int32_t bytes, time_t seconds)
{
+ debug3("rekey after %lld bytes, %d seconds", (long long)bytes,
+ (int)seconds);
active_state->rekey_limit = bytes;
+ active_state->rekey_interval = seconds;
+ /*
+ * We set the time here so that in post-auth privsep slave we count
+ * from the completion of the authentication.
+ */
+ active_state->rekey_time = time(NULL);
+}
+
+time_t
+packet_get_rekey_timeout(void)
+{
+ time_t seconds;
+
+ seconds = active_state->rekey_time + active_state->rekey_interval -
+ time(NULL);
+ return (seconds <= 0 ? 1 : seconds);
}
void
Index: packet.h
===================================================================
RCS file: /var/cvs/openssh/packet.h,v
retrieving revision 1.60
diff -u -p -r1.60 packet.h
--- packet.h 10 Feb 2012 21:19:21 -0000 1.60
+++ packet.h 16 May 2013 06:46:59 -0000
@@ -115,7 +115,8 @@ do { \
} while (0)
int packet_need_rekeying(void);
-void packet_set_rekey_limit(u_int32_t);
+void packet_set_rekey_limits(u_int32_t, time_t);
+time_t packet_get_rekey_timeout(void);
void packet_backup_state(void);
void packet_restore_state(void);
Index: readconf.c
===================================================================
RCS file: /var/cvs/openssh/readconf.c,v
retrieving revision 1.174.6.2
diff -u -p -r1.174.6.2 readconf.c
--- readconf.c 5 Apr 2013 00:18:58 -0000 1.174.6.2
+++ readconf.c 16 May 2013 06:46:59 -0000
@@ -562,39 +562,54 @@ parse_yesnoask:
case oRekeyLimit:
arg = strdelim(&s);
if (!arg || *arg == '\0')
- fatal("%.200s line %d: Missing argument.", filename, linenum);
- if (arg[0] < '0' || arg[0] > '9')
- fatal("%.200s line %d: Bad number.", filename, linenum);
- orig = val64 = strtoll(arg, &endofnumber, 10);
- if (arg == endofnumber)
- fatal("%.200s line %d: Bad number.", filename, linenum);
- switch (toupper(*endofnumber)) {
- case '\0':
- scale = 1;
- break;
- case 'K':
- scale = 1<<10;
- break;
- case 'M':
- scale = 1<<20;
- break;
- case 'G':
- scale = 1<<30;
- break;
- default:
- fatal("%.200s line %d: Invalid RekeyLimit suffix",
- filename, linenum);
+ fatal("%.200s line %d: Missing argument.", filename,
+ linenum);
+ if (strcmp(arg, "default") == 0) {
+ val64 = 0;
+ } else {
+ if (arg[0] < '0' || arg[0] > '9')
+ fatal("%.200s line %d: Bad number.", filename,
+ linenum);
+ orig = val64 = strtoll(arg, &endofnumber, 10);
+ if (arg == endofnumber)
+ fatal("%.200s line %d: Bad number.", filename,
+ linenum);
+ switch (toupper(*endofnumber)) {
+ case '\0':
+ scale = 1;
+ break;
+ case 'K':
+ scale = 1<<10;
+ break;
+ case 'M':
+ scale = 1<<20;
+ break;
+ case 'G':
+ scale = 1<<30;
+ break;
+ default:
+ fatal("%.200s line %d: Invalid RekeyLimit "
+ "suffix", filename, linenum);
+ }
+ val64 *= scale;
+ /* detect integer wrap and too-large limits */
+ if ((val64 / scale) != orig || val64 > UINT_MAX)
+ fatal("%.200s line %d: RekeyLimit too large",
+ filename, linenum);
+ if (val64 != 0 && val64 < 16)
+ fatal("%.200s line %d: RekeyLimit too small",
+ filename, linenum);
}
- val64 *= scale;
- /* detect integer wrap and too-large limits */
- if ((val64 / scale) != orig || val64 > UINT_MAX)
- fatal("%.200s line %d: RekeyLimit too large",
- filename, linenum);
- if (val64 < 16)
- fatal("%.200s line %d: RekeyLimit too small",
- filename, linenum);
if (*activep && options->rekey_limit == -1)
options->rekey_limit = (u_int32_t)val64;
+ if (s != NULL) { /* optional rekey interval present */
+ if (strcmp(s, "none") == 0) {
+ (void)strdelim(&s); /* discard */
+ break;
+ }
+ intptr = &options->rekey_interval;
+ goto parse_time;
+ }
break;
case oIdentityFile:
@@ -1202,6 +1217,7 @@ initialize_options(Options * options)
options->no_host_authentication_for_localhost = - 1;
options->identities_only = - 1;
options->rekey_limit = - 1;
+ options->rekey_interval = -1;
options->verify_host_key_dns = -1;
options->server_alive_interval = -1;
options->server_alive_count_max = -1;
@@ -1339,6 +1355,8 @@ fill_default_options(Options * options)
options->enable_ssh_keysign = 0;
if (options->rekey_limit == -1)
options->rekey_limit = 0;
+ if (options->rekey_interval == -1)
+ options->rekey_interval = 0;
if (options->verify_host_key_dns == -1)
options->verify_host_key_dns = 0;
if (options->server_alive_interval == -1)
Index: readconf.h
===================================================================
RCS file: /var/cvs/openssh/readconf.h,v
retrieving revision 1.83.6.2
diff -u -p -r1.83.6.2 readconf.h
--- readconf.h 5 Apr 2013 00:18:58 -0000 1.83.6.2
+++ readconf.h 16 May 2013 06:46:59 -0000
@@ -110,6 +110,7 @@ typedef struct {
int enable_ssh_keysign;
int64_t rekey_limit;
+ int rekey_interval;
int no_host_authentication_for_localhost;
int identities_only;
int server_alive_interval;
Index: servconf.c
===================================================================
RCS file: /var/cvs/openssh/servconf.c,v
retrieving revision 1.231
diff -u -p -r1.231 servconf.c
--- servconf.c 12 Feb 2013 00:02:08 -0000 1.231
+++ servconf.c 16 May 2013 06:46:59 -0000
@@ -20,6 +20,7 @@
#include <netinet/in_systm.h>
#include <netinet/ip.h>
+#include <ctype.h>
#include <netdb.h>
#include <pwd.h>
#include <stdio.h>
@@ -110,6 +111,8 @@ initialize_server_options(ServerOptions
options->permit_user_env = -1;
options->use_login = -1;
options->compression = -1;
+ options->rekey_limit = -1;
+ options->rekey_interval = -1;
options->allow_tcp_forwarding = -1;
options->allow_agent_forwarding = -1;
options->num_allow_users = 0;
@@ -249,6 +252,10 @@ fill_default_server_options(ServerOption
options->use_login = 0;
if (options->compression == -1)
options->compression = COMP_DELAYED;
+ if (options->rekey_limit == -1)
+ options->rekey_limit = 0;
+ if (options->rekey_interval == -1)
+ options->rekey_interval = 0;
if (options->allow_tcp_forwarding == -1)
options->allow_tcp_forwarding = FORWARD_ALLOW;
if (options->allow_agent_forwarding == -1)
@@ -320,7 +327,7 @@ typedef enum {
sX11Forwarding, sX11DisplayOffset, sX11UseLocalhost,
sStrictModes, sEmptyPasswd, sTCPKeepAlive,
sPermitUserEnvironment, sUseLogin, sAllowTcpForwarding, sCompression,
- sAllowUsers, sDenyUsers, sAllowGroups, sDenyGroups,
+ sRekeyLimit, sAllowUsers, sDenyUsers, sAllowGroups, sDenyGroups,
sIgnoreUserKnownHosts, sCiphers, sMacs, sProtocol, sPidFile,
sGatewayPorts, sPubkeyAuthentication, sXAuthLocation, sSubsystem,
sMaxStartups, sMaxAuthTries, sMaxSessions,
@@ -422,6 +429,7 @@ static struct {
{ "permituserenvironment", sPermitUserEnvironment, SSHCFG_GLOBAL },
{ "uselogin", sUseLogin, SSHCFG_GLOBAL },
{ "compression", sCompression, SSHCFG_GLOBAL },
+ { "rekeylimit", sRekeyLimit, SSHCFG_ALL },
{ "tcpkeepalive", sTCPKeepAlive, SSHCFG_GLOBAL },
{ "keepalive", sTCPKeepAlive, SSHCFG_GLOBAL }, /* obsolete alias */
{ "allowtcpforwarding", sAllowTcpForwarding, SSHCFG_ALL },
@@ -800,14 +808,14 @@ process_server_config_line(ServerOptions
const char *filename, int linenum, int *activep,
struct connection_info *connectinfo)
{
- char *cp, **charptr, *arg, *p;
- int cmdline = 0, *intptr, value, value2, n;
+ char *cp, **charptr, *arg, *p, *endofnumber;
+ int cmdline = 0, *intptr, value, value2, n, port, scale;
SyslogFacility *log_facility_ptr;
LogLevel *log_level_ptr;
ServerOpCodes opcode;
- int port;
u_int i, flags = 0;
size_t len;
+ long long orig, val64;
const struct multistate *multistate_ptr;
cp = line;
@@ -1118,6 +1126,59 @@ process_server_config_line(ServerOptions
multistate_ptr = multistate_compression;
goto parse_multistate;
+ case sRekeyLimit:
+ arg = strdelim(&cp);
+ if (!arg || *arg == '\0')
+ fatal("%.200s line %d: Missing argument.", filename,
+ linenum);
+ if (strcmp(arg, "default") == 0) {
+ val64 = 0;
+ } else {
+ if (arg[0] < '0' || arg[0] > '9')
+ fatal("%.200s line %d: Bad number.", filename,
+ linenum);
+ orig = val64 = strtoll(arg, &endofnumber, 10);
+ if (arg == endofnumber)
+ fatal("%.200s line %d: Bad number.", filename,
+ linenum);
+ switch (toupper(*endofnumber)) {
+ case '\0':
+ scale = 1;
+ break;
+ case 'K':
+ scale = 1<<10;
+ break;
+ case 'M':
+ scale = 1<<20;
+ break;
+ case 'G':
+ scale = 1<<30;
+ break;
+ default:
+ fatal("%.200s line %d: Invalid RekeyLimit "
+ "suffix", filename, linenum);
+ }
+ val64 *= scale;
+ /* detect integer wrap and too-large limits */
+ if ((val64 / scale) != orig || val64 > UINT_MAX)
+ fatal("%.200s line %d: RekeyLimit too large",
+ filename, linenum);
+ if (val64 != 0 && val64 < 16)
+ fatal("%.200s line %d: RekeyLimit too small",
+ filename, linenum);
+ }
+ if (*activep && options->rekey_limit == -1)
+ options->rekey_limit = (u_int32_t)val64;
+ if (cp != NULL) { /* optional rekey interval present */
+ if (strcmp(cp, "none") == 0) {
+ (void)strdelim(&cp); /* discard */
+ break;
+ }
+ intptr = &options->rekey_interval;
+ goto parse_time;
+ }
+ break;
+
case sGatewayPorts:
intptr = &options->gateway_ports;
multistate_ptr = multistate_gatewayports;
@@ -1718,6 +1779,8 @@ copy_set_server_options(ServerOptions *d
M_CP_INTOPT(max_authtries);
M_CP_INTOPT(ip_qos_interactive);
M_CP_INTOPT(ip_qos_bulk);
+ M_CP_INTOPT(rekey_limit);
+ M_CP_INTOPT(rekey_interval);
/* See comment in servconf.h */
COPY_MATCH_STRING_OPTS();
@@ -2005,6 +2068,8 @@ dump_config(ServerOptions *o)
printf("ipqos %s ", iptos2str(o->ip_qos_interactive));
printf("%s\n", iptos2str(o->ip_qos_bulk));
+
+ printf("rekeylimit %lld %d\n", o->rekey_limit, o->rekey_interval);
channel_print_adm_permitted_opens();
}
Index: servconf.h
===================================================================
RCS file: /var/cvs/openssh/servconf.h,v
retrieving revision 1.99
diff -u -p -r1.99 servconf.h
--- servconf.h 9 Jan 2013 04:56:45 -0000 1.99
+++ servconf.h 16 May 2013 06:46:59 -0000
@@ -176,6 +176,9 @@ typedef struct {
char *authorized_keys_command;
char *authorized_keys_command_user;
+ int64_t rekey_limit;
+ int rekey_interval;
+
char *version_addendum; /* Appended to SSH banner */
u_int num_auth_methods;
Index: serverloop.c
===================================================================
RCS file: /var/cvs/openssh/serverloop.c,v
retrieving revision 1.173
diff -u -p -r1.173 serverloop.c
--- serverloop.c 7 Dec 2012 02:07:47 -0000 1.173
+++ serverloop.c 16 May 2013 06:47:00 -0000
@@ -277,7 +277,7 @@ client_alive_check(void)
*/
static void
wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
- u_int *nallocp, u_int max_time_milliseconds)
+ u_int *nallocp, u_int64_t max_time_milliseconds)
{
struct timeval tv, *tvp;
int ret;
@@ -563,7 +563,7 @@ server_loop(pid_t pid, int fdin_arg, int
int wait_status; /* Status returned by wait(). */
pid_t wait_pid; /* pid returned by wait(). */
int waiting_termination = 0; /* Have displayed waiting close message. */
- u_int max_time_milliseconds;
+ u_int64_t max_time_milliseconds;
u_int previous_stdout_buffer_bytes;
u_int stdout_buffer_bytes;
int type;
@@ -826,6 +826,7 @@ server_loop2(Authctxt *authctxt)
{
fd_set *readset = NULL, *writeset = NULL;
int rekeying = 0, max_fd, nalloc = 0;
+ u_int64_t rekey_timeout_ms = 0;
debug("Entering interactive session for SSH2.");
@@ -854,8 +855,13 @@ server_loop2(Authctxt *authctxt)
if (!rekeying && packet_not_very_much_data_to_write())
channel_output_poll();
+ if (options.rekey_interval > 0 && compat20 && !rekeying)
+ rekey_timeout_ms = packet_get_rekey_timeout() * 1000;
+ else
+ rekey_timeout_ms = 0;
+
wait_until_can_do_something(&readset, &writeset, &max_fd,
- &nalloc, 0);
+ &nalloc, rekey_timeout_ms);
if (received_sigterm) {
logit("Exiting on signal %d", (int)received_sigterm);
Index: ssh_config
===================================================================
RCS file: /var/cvs/openssh/ssh_config,v
retrieving revision 1.28
diff -u -p -r1.28 ssh_config
--- ssh_config 12 Jan 2010 08:40:27 -0000 1.28
+++ ssh_config 16 May 2013 06:47:00 -0000
@@ -45,3 +45,4 @@
# PermitLocalCommand no
# VisualHostKey no
# ProxyCommand ssh -q -W %h:%p gateway.example.com
+# RekeyLimit 1G 1h
Index: ssh_config.5
===================================================================
RCS file: /var/cvs/openssh/ssh_config.5,v
retrieving revision 1.161
diff -u -p -r1.161 ssh_config.5
--- ssh_config.5 9 Jan 2013 05:12:19 -0000 1.161
+++ ssh_config.5 16 May 2013 06:47:00 -0000
@@ -931,8 +931,9 @@ The default is
This option applies to protocol version 2 only.
.It Cm RekeyLimit
Specifies the maximum amount of data that may be transmitted before the
-session key is renegotiated.
-The argument is the number of bytes, with an optional suffix of
+session key is renegotiated, optionally followed a maximum amount of
+time that may pass before the session key is renegotiated.
+The first argument is specified in bytes and may have a suffix of
.Sq K ,
.Sq M ,
or
@@ -943,6 +944,17 @@ The default is between
and
.Sq 4G ,
depending on the cipher.
+The optional second value is specified in seconds and may use any of the
+units documented in the
+.Sx TIME FORMATS
+section of
+.Xr sshd_config 5 .
+The default value for
+.Cm RekeyLimit
+is
+.Dq default none ,
+which means that rekeying is performed after the cipher's default amount
+of data has been sent or received and no time based rekeying is done.
This option applies to protocol version 2 only.
.It Cm RemoteForward
Specifies that a TCP port on the remote machine be forwarded over
Index: sshconnect2.c
===================================================================
RCS file: /var/cvs/openssh/sshconnect2.c,v
retrieving revision 1.184.2.1
diff -u -p -r1.184.2.1 sshconnect2.c
--- sshconnect2.c 5 Apr 2013 00:13:31 -0000 1.184.2.1
+++ sshconnect2.c 16 May 2013 06:47:00 -0000
@@ -197,8 +197,9 @@ ssh_kex2(char *host, struct sockaddr *ho
if (options.kex_algorithms != NULL)
myproposal[PROPOSAL_KEX_ALGS] = options.kex_algorithms;
- if (options.rekey_limit)
- packet_set_rekey_limit((u_int32_t)options.rekey_limit);
+ if (options.rekey_limit || options.rekey_interval)
+ packet_set_rekey_limits((u_int32_t)options.rekey_limit,
+ (time_t)options.rekey_interval);
/* start key exchange */
kex = kex_setup(myproposal);
Index: sshd.c
===================================================================
RCS file: /var/cvs/openssh/sshd.c,v
retrieving revision 1.420
diff -u -p -r1.420 sshd.c
--- sshd.c 12 Feb 2013 00:04:48 -0000 1.420
+++ sshd.c 16 May 2013 06:47:00 -0000
@@ -2355,6 +2355,10 @@ do_ssh2_kex(void)
if (options.kex_algorithms != NULL)
myproposal[PROPOSAL_KEX_ALGS] = options.kex_algorithms;
+ if (options.rekey_limit || options.rekey_interval)
+ packet_set_rekey_limits((u_int32_t)options.rekey_limit,
+ (time_t)options.rekey_interval);
+
myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
/* start key exchange */
Index: sshd_config
===================================================================
RCS file: /var/cvs/openssh/sshd_config,v
retrieving revision 1.91
diff -u -p -r1.91 sshd_config
--- sshd_config 12 Feb 2013 00:02:09 -0000 1.91
+++ sshd_config 16 May 2013 06:47:00 -0000
@@ -29,6 +29,9 @@
#KeyRegenerationInterval 1h
#ServerKeyBits 1024
+# Ciphers and keying
+#RekeyLimit default none
+
# Logging
# obsoletes QuietMode and FascistLogging
#SyslogFacility AUTH
Index: sshd_config.5
===================================================================
RCS file: /var/cvs/openssh/sshd_config.5,v
retrieving revision 1.163
diff -u -p -r1.163 sshd_config.5
--- sshd_config.5 12 Feb 2013 00:02:09 -0000 1.163
+++ sshd_config.5 16 May 2013 06:47:00 -0000
@@ -799,6 +799,7 @@ Available keywords are
.Cm PermitRootLogin ,
.Cm PermitTunnel ,
.Cm PubkeyAuthentication ,
+.Cm RekeyLimit ,
.Cm RhostsRSAAuthentication ,
.Cm RSAAuthentication ,
.Cm X11DisplayOffset ,
@@ -993,6 +994,33 @@ Specifies whether public key authenticat
The default is
.Dq yes .
Note that this option applies to protocol version 2 only.
+.It Cm RekeyLimit
+Specifies the maximum amount of data that may be transmitted before the
+session key is renegotiated, optionally followed a maximum amount of
+time that may pass before the session key is renegotiated.
+The first argument is specified in bytes and may have a suffix of
+.Sq K ,
+.Sq M ,
+or
+.Sq G
+to indicate Kilobytes, Megabytes, or Gigabytes, respectively.
+The default is between
+.Sq 1G
+and
+.Sq 4G ,
+depending on the cipher.
+The optional second value is specified in seconds and may use any of the
+units documented in the
+.Sx TIME FORMATS
+section of
+.Xr sshd_config 5 .
+The default value for
+.Cm RekeyLimit
+is
+.Dq default none ,
+which means that rekeying is performed after the cipher's default amount
+of data has been sent or received and no time based rekeying is done.
+This option applies to protocol version 2 only.
.It Cm RevokedKeys
Specifies revoked public keys.
Keys listed in this file will be refused for public key authentication.
--
Darren Tucker (dtucker at zip.com.au)
GPG key 8FF4FA69 / D9A3 86E9 7EEE AF4B B2D4 37C9 C982 80C7 8FF4 FA69
Good judgement comes with experience. Unfortunately, the experience
usually comes from bad judgement.
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