[cli-sessions] Add support for cli-sessions feature (sonic-net#99)

Add support for cli-sessions feature

What I did:
Added handlers for new SSH_SERVER and SERIAL_CONSOLE attributes.

Why I did it:

Give ability to:
configure limit for active login sessions.
configure ssh-server / serial console autologout timeout
configure sysrq-capabilities (enable / disable)

How I did it

Add new service that responsible for serial configuration;
Update existing flows for extended ssh-server configurations in hostcfgd;
Add YANG model to support new configuration.

How I verified it:

Configure, reconfigure, and reset all new parameters, check if applicapple parameters was updated in the system.
Added unittests.

Author: i-davydenko

data/templates/limits.conf.j2

@@ -66,4 +66,8 @@
 # ftp             -       chroot          /ftp
 # @student        -       maxlogins       4
 
+{% if max_sessions and max_sessions | int > 0 -%}
+* - maxsyslogins {{ max_sessions }}
+{% endif -%}
+
 # End of file

scripts/hostcfgd

@@ -54,9 +54,14 @@ LINUX_DEFAULT_PASS_MAX_DAYS = 99999
 LINUX_DEFAULT_PASS_WARN_AGE = 7
 
 # Ssh min-max values
-SSH_MIN_VALUES={"authentication_retries": 3, "login_timeout": 1, "ports": 1}
-SSH_MAX_VALUES={"authentication_retries": 100, "login_timeout": 600, "ports": 65535}
-SSH_CONFIG_NAMES={"authentication_retries": "MaxAuthTries" , "login_timeout": "LoginGraceTime"}
+SSH_MIN_VALUES={"authentication_retries": 3, "login_timeout": 1, "ports": 1,
+                "inactivity_timeout": 0, "max_sessions": 0}
+SSH_MAX_VALUES={"authentication_retries": 100, "login_timeout": 600,
+                "ports": 65535, "inactivity_timeout": 35000,
+                "max_sessions": 100}
+SSH_CONFIG_NAMES={"authentication_retries": "MaxAuthTries",
+                  "login_timeout": "LoginGraceTime", "ports": "Port",
+                  "inactivity_timeout": "ClientAliveInterval"}
 
 ACCOUNT_NAME = 0 # index of account name
 AGE_DICT = { 'MAX_DAYS': {'REGEX_DAYS': r'^PASS_MAX_DAYS[ \t]*(?P<max_days>-?\d*)', 'DAYS': 'max_days', 'CHAGE_FLAG': '-M '},
@@ -1101,9 +1106,15 @@ class SshServer(object):
                 syslog.syslog(syslog.LOG_ERR, "Ssh {} {} out of range".format(key, value))
             elif key in SSH_CONFIG_NAMES:
                 # search replace configuration - if not in config file - append
+                if key == "inactivity_timeout":
+                    # translate min to sec.
+                    value = int(value) * 60
                 kv_str = "{} {}".format(SSH_CONFIG_NAMES[key], str(value)) # name +' '+ value format
                 modify_single_file_inplace(SSH_CONFG_TMP,['-E', "/^#?" + SSH_CONFIG_NAMES[key]+"/{h;s/.*/"+
                  kv_str + "/};${x;/^$/{s//" + kv_str + "/;H};x}"])
+            elif key in ['max_sessions']:
+                # Ignore, these parameters handled in other modules
+                continue
             else:
                 syslog.syslog(syslog.LOG_ERR, "Failed to update sshd config file - wrong key {}".format(key))
 
@@ -1318,16 +1329,31 @@ class PamLimitsCfg(object):
         self.config_db = config_db
         self.hwsku = ""
         self.type = ""
+        self.max_sessions = None
 
     # Load config from ConfigDb and render config file/
     def update_config_file(self):
         device_metadata = self.config_db.get_table('DEVICE_METADATA')
-        if "localhost" not in device_metadata:
+        ssh_server_policies = {}
+        try: 
+            ssh_server_policies = self.config_db.get_table('SSH_SERVER')
+        except KeyError:
+            """Dont throw except in case we don`t have SSH_SERVER config."""
+            pass
+	
+        if "localhost" not in device_metadata and "POLICIES" not in ssh_server_policies:
             return
 
         self.read_localhost_config(device_metadata["localhost"])
+        self.read_max_sessions_config(ssh_server_policies.get("POLICIES", None))
         self.render_conf_file()
 
+    # Read max_sessions config
+    def read_max_sessions_config(self, ssh_server_policies):
+        if ssh_server_policies is not None:
+            max_sess_cfg = ssh_server_policies.get('max_sessions', 0)
+            self.max_sessions = max_sess_cfg if max_sess_cfg != 0 else None
+
     # Read localhost config
     def read_localhost_config(self, localhost):
         if "hwsku" in localhost:
@@ -1344,7 +1370,6 @@ class PamLimitsCfg(object):
     def render_conf_file(self):
         env = jinja2.Environment(loader=jinja2.FileSystemLoader('/'), trim_blocks=True)
         env.filters['sub'] = sub
-
         try:
             template_file = os.path.abspath(PAM_LIMITS_CONF_TEMPLATE)
             template = env.get_template(template_file)
@@ -1358,7 +1383,8 @@ class PamLimitsCfg(object):
             template = env.get_template(template_file)
             limits_conf = template.render(
                                         hwsku=self.hwsku,
-                                        type=self.type)
+                                        type=self.type,
+                                        max_sessions=self.max_sessions)
             with open(LIMITS_CONF, 'w') as f:
                 f.write(limits_conf)
         except Exception as e:
@@ -1690,6 +1716,39 @@ class FipsCfg(object):
         syslog.syslog(syslog.LOG_INFO, f'FipsCfg: update the FIPS enforce option {self.enforce}.')
         loader.set_fips(image, self.enforce)
 
+
+class SerialConsoleCfg:
+
+    def __init__(self):
+        self.cache = {}
+
+    def load(self, cli_sessions_conf):
+        self.cache = cli_sessions_conf or {}
+        syslog.syslog(syslog.LOG_INFO,
+                      f'SerialConsoleCfg: Initial config: {self.cache}')
+
+    def update_serial_console_cfg(self, key, data):
+        '''
+            Apply config flow:
+                inactivity_timeout | set here AND in ssh_config flow | serial-config.service restarted.
+                max_sessions | set by PamLimitsCfg | serial-config.service DOESNT restarted.
+                sysrq_capabilities | set here | serial-config.service restarted.
+        '''
+
+        if self.cache.get(key, {}) != data:
+            ''' Config changed, need to restart the serial-config.service '''
+            syslog.syslog(syslog.LOG_INFO, f'Set serial-config parameter {key} value: {data}')
+            try:
+                run_cmd(['sudo', 'service', 'serial-config', 'restart'],
+                        True, True)
+            except Exception:
+                syslog.syslog(syslog.LOG_ERR, f'Failed to update {key} serial-config.service config')
+                return
+            self.cache.update({key: data})
+
+        return
+
+
 class HostConfigDaemon:
     def __init__(self):
         self.state_db_conn = DBConnector(STATE_DB, 0)
@@ -1741,6 +1800,9 @@ class HostConfigDaemon:
         # Initialize FipsCfg
         self.fipscfg = FipsCfg(self.state_db_conn)
 
+        # Initialize SerialConsoleCfg
+        self.serialconscfg = SerialConsoleCfg()
+
     def load(self, init_data):
         aaa = init_data['AAA']
         tacacs_global = init_data['TACPLUS']
@@ -1763,6 +1825,7 @@ class HostConfigDaemon:
         ntp_global = init_data.get(swsscommon.CFG_NTP_GLOBAL_TABLE_NAME)
         ntp_servers = init_data.get(swsscommon.CFG_NTP_SERVER_TABLE_NAME)
         ntp_keys = init_data.get(swsscommon.CFG_NTP_KEY_TABLE_NAME)
+        serial_console = init_data.get('SERIAL_CONSOLE', {})
 
         self.aaacfg.load(aaa, tacacs_global, tacacs_server, radius_global, radius_server, ldap_global, ldap_server)
         self.iptables.load(lpbk_table)
@@ -1771,11 +1834,12 @@ class HostConfigDaemon:
         self.sshscfg.load(ssh_server)
         self.devmetacfg.load(dev_meta)
         self.mgmtifacecfg.load(mgmt_ifc, mgmt_vrf)
-
         self.rsyslogcfg.load(syslog_cfg, syslog_srv)
         self.dnscfg.load(dns)
         self.fipscfg.load(fips_cfg)
         self.ntpcfg.load(ntp_global, ntp_servers, ntp_keys)
+        self.serialconscfg.load(serial_console)
+        self.pamLimitsCfg.update_config_file()
 
         # Update AAA with the hostname
         self.aaacfg.hostname_update(self.devmetacfg.hostname)
@@ -1797,6 +1861,8 @@ class HostConfigDaemon:
 
     def ssh_handler(self, key, op, data):
         self.sshscfg.policies_update(key, data)
+        self.pamLimitsCfg.update_config_file()
+
         syslog.syslog(syslog.LOG_INFO, 'SSH Update: key: {}, op: {}, data: {}'.format(key, op, data))
 
     def tacacs_server_handler(self, key, op, data):
@@ -1922,6 +1988,10 @@ class HostConfigDaemon:
         data = self.config_db.get_table("FIPS")
         self.fipscfg.fips_handler(data)
 
+    def serial_console_config_handler(self, key, op, data):
+        syslog.syslog(syslog.LOG_INFO, 'SERIAL_CONSOLE table handler...')
+        self.serialconscfg.update_serial_console_cfg(key, data)
+
     def wait_till_system_init_done(self):
         # No need to print the output in the log file so using the "--quiet"
         # flag
@@ -1951,6 +2021,8 @@ class HostConfigDaemon:
         self.config_db.subscribe('LDAP_SERVER', make_callback(self.ldap_server_handler))
         self.config_db.subscribe('PASSW_HARDENING', make_callback(self.passwh_handler))
         self.config_db.subscribe('SSH_SERVER', make_callback(self.ssh_handler))
+        # Handle SERIAL_CONSOLE
+        self.config_db.subscribe('SERIAL_CONSOLE', make_callback(self.serial_console_config_handler))
         # Handle IPTables configuration
         self.config_db.subscribe('LOOPBACK_INTERFACE', make_callback(self.lpbk_handler))
         # Handle updates to src intf changes in radius

tests/hostcfgd/hostcfgd_test.py

@@ -121,6 +121,48 @@ def test_loopback_update(self):
             ])
 
 
+class TestSerialConsoleCfgd(TestCase):
+    """
+        Test hostcfd daemon - SerialConsoleCfg
+    """
+    def setUp(self):
+        MockConfigDb.CONFIG_DB['SERIAL_CONSOLE'] = {
+            'POLICIES': {'inactivity-timeout': '15', 'sysrq-capabilities': 'disabled'}
+        }
+
+    def tearDown(self):
+        MockConfigDb.CONFIG_DB = {}
+
+    def test_serial_console_update_cfg(self):
+        with mock.patch('hostcfgd.subprocess') as mocked_subprocess:
+            popen_mock = mock.Mock()
+            attrs = {'communicate.return_value': ('output', 'error')}
+            popen_mock.configure_mock(**attrs)
+            mocked_subprocess.Popen.return_value = popen_mock
+
+            serialcfg = hostcfgd.SerialConsoleCfg()
+            serialcfg.update_serial_console_cfg(
+                'POLICIES', MockConfigDb.CONFIG_DB['SERIAL_CONSOLE']['POLICIES'])
+            mocked_subprocess.check_call.assert_has_calls([
+                call(['sudo', 'service', 'serial-config', 'restart']),
+            ])
+
+    def test_serial_console_is_caching_config(self):
+        with mock.patch('hostcfgd.subprocess') as mocked_subprocess:
+            popen_mock = mock.Mock()
+            attrs = {'communicate.return_value': ('output', 'error')}
+            popen_mock.configure_mock(**attrs)
+            mocked_subprocess.Popen.return_value = popen_mock
+
+            serialcfg = hostcfgd.SerialConsoleCfg()
+            serialcfg.cache['POLICIES'] = MockConfigDb.CONFIG_DB['SERIAL_CONSOLE']['POLICIES']
+
+            serialcfg.update_serial_console_cfg(
+                'POLICIES', MockConfigDb.CONFIG_DB['SERIAL_CONSOLE']['POLICIES'])
+
+            mocked_subprocess.check_call.assert_not_called()
+
+
 class TestHostcfgdDaemon(TestCase):
 
     def setUp(self):

tests/hostcfgd/sample_output/SSH_SERVER/sshd_config.old

@@ -118,4 +118,4 @@ Subsystem	sftp	/usr/lib/openssh/sftp-server
 #	PermitTTY no
 #	ForceCommand cvs server
 PermitRootLogin yes
-ClientAliveInterval 120
+ClientAliveInterval 900

tests/hostcfgd/sample_output/SSH_SERVER_default_values/sshd_config

@@ -118,4 +118,4 @@ Subsystem	sftp	/usr/lib/openssh/sftp-server
 #	PermitTTY no
 #	ForceCommand cvs server
 PermitRootLogin yes
-ClientAliveInterval 120
+ClientAliveInterval 900

tests/hostcfgd/sample_output/SSH_SERVER_modify_all/sshd_config

@@ -119,4 +119,4 @@ Subsystem	sftp	/usr/lib/openssh/sftp-server
 #	PermitTTY no
 #	ForceCommand cvs server
 PermitRootLogin yes
-ClientAliveInterval 120
+ClientAliveInterval 900

tests/hostcfgd/sample_output/SSH_SERVER_modify_authentication_retries/sshd_config

@@ -118,4 +118,4 @@ Subsystem	sftp	/usr/lib/openssh/sftp-server
 #	PermitTTY no
 #	ForceCommand cvs server
 PermitRootLogin yes
-ClientAliveInterval 120
+ClientAliveInterval 900

tests/hostcfgd/sample_output/SSH_SERVER_modify_login_timeout/sshd_config

@@ -118,4 +118,4 @@ Subsystem	sftp	/usr/lib/openssh/sftp-server
 #	PermitTTY no
 #	ForceCommand cvs server
 PermitRootLogin yes
-ClientAliveInterval 120
+ClientAliveInterval 900

tests/hostcfgd/sample_output/SSH_SERVER_modify_ports/sshd_config

@@ -120,4 +120,4 @@ Subsystem	sftp	/usr/lib/openssh/sftp-server
 #	PermitTTY no
 #	ForceCommand cvs server
 PermitRootLogin yes
-ClientAliveInterval 120
+ClientAliveInterval 900

tests/hostcfgd/test_ssh_server_vectors.py

@@ -11,6 +11,8 @@
                         "authentication_retries": "6",
                         "login_timeout": "120",
                         "ports": "22",
+                        "inactivity_timeout": "15",
+                        "max_sessions": "0",
                     }
                 },
                 "DEVICE_METADATA": {
@@ -35,6 +37,12 @@
                         "num_dumps": "3",
                         "memory": "0M-2G:256M,2G-4G:320M,4G-8G:384M,8G-:448M"
                     }
+                },
+                "SERIAL_CONSOLE": {
+                    "POLICIES":{
+                        "inactivity_timeout": "15",
+                        "sysrq_capabilities": "disabled"
+                    }
                 }
             },
             "modify_authentication_retries":{
@@ -43,6 +51,8 @@
                         "authentication_retries": "12",
                         "login_timeout": "120",
                         "ports": "22",
+                        "inactivity_timeout": "15",
+                        "max_sessions": "0",
                     }
                 },
                 "DEVICE_METADATA": {
@@ -67,6 +77,12 @@
                         "num_dumps": "3",
                         "memory": "0M-2G:256M,2G-4G:320M,4G-8G:384M,8G-:448M"
                     }
+                },
+                "SERIAL_CONSOLE": {
+                    "POLICIES":{
+                        "inactivity_timeout": "15",
+                        "sysrq_capabilities": "disabled"
+                    }
                 }
             },
             "modify_login_timeout":{
@@ -75,6 +91,8 @@
                         "authentication_retries": "6",
                         "login_timeout": "60",
                         "ports": "22",
+                        "inactivity_timeout": "15",
+                        "max_sessions": "0",
                     }
                 },
                 "DEVICE_METADATA": {
@@ -99,6 +117,12 @@
                         "num_dumps": "3",
                         "memory": "0M-2G:256M,2G-4G:320M,4G-8G:384M,8G-:448M"
                     }
+                },
+                "SERIAL_CONSOLE": {
+                    "POLICIES":{
+                        "inactivity_timeout": "15",
+                        "sysrq_capabilities": "disabled"
+                    }
                 }
             },
             "modify_ports":{
@@ -107,6 +131,8 @@
                         "authentication_retries": "6",
                         "login_timeout": "120",
                         "ports": "22,23,24",
+                        "inactivity_timeout": "15",
+                        "max_sessions": "0",
                     }
                 },
                 "DEVICE_METADATA": {
@@ -132,13 +158,21 @@
                         "memory": "0M-2G:256M,2G-4G:320M,4G-8G:384M,8G-:448M"
                     }
                 },
+                "SERIAL_CONSOLE": {
+                    "POLICIES":{
+                        "inactivity_timeout": "15",
+                        "sysrq_capabilities": "disabled"
+                    }
+                }
             },
             "modify_all":{
                 "SSH_SERVER": {
                     "POLICIES":{
                         "authentication_retries": "16",
                         "login_timeout": "140",
                         "ports": "22,222",
+                        "inactivity_timeout": "15",
+                        "max_sessions": "0",
                     }
                 },
                 "DEVICE_METADATA": {
@@ -163,6 +197,12 @@
                         "num_dumps": "3",
                         "memory": "0M-2G:256M,2G-4G:320M,4G-8G:384M,8G-:448M"
                     }
+                },
+                "SERIAL_CONSOLE": {
+                    "POLICIES":{
+                        "inactivity_timeout": "15",
+                        "sysrq_capabilities": "disabled"
+                    }
                 }
             }
         }