Add j2 template for enable pam_limit and limit SSH session (#10177)
#### Why I did it
When too many user login concurrently and run commands, SONiC may kernel panic on some device which has very limited memory.
#### How I did it
Add j2 template for setup pam_limit plugin for limit SSH session per-user.
#### How to verify it
Manually validate the j2 template can generate correct config file.
#### Which release branch to backport (provide reason below if selected)
- [x] 201811
- [ ] 201911
- [ ] 202006
- [x] 202012
- [x] 202106
- [x] 202111
#### Description for the changelog
Add j2 template for setup pam_limit plugin for limit SSH session per-user.
#### A picture of a cute animal (not mandatory but encouraged)
This commit is contained in:
Hua Liu
GitHub
parent
6e51779efb
commit
271ef69e60
69
src/sonic-host-services-data/templates/limits.conf.j2
Executable file
69
src/sonic-host-services-data/templates/limits.conf.j2
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@ -0,0 +1,69 @@
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# /etc/security/limits.conf
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#
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# This file generate by j2 template file: src/sonic-host-services-data/templates/limits.conf.j2
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#
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# Each line describes a limit for a user in the form:
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#
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# <domain> <type> <item> <value>
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#
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# Where:
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# <domain> can be:
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# - a user name
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# - a group name, with @group syntax
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# - the wildcard *, for default entry
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# - the wildcard %, can be also used with %group syntax,
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# for maxlogin limit
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# - NOTE: group and wildcard limits are not applied to root.
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# To apply a limit to the root user, <domain> must be
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# the literal username root.
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#
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# <type> can have the two values:
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# - "soft" for enforcing the soft limits
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# - "hard" for enforcing hard limits
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#
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# <item> can be one of the following:
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# - core - limits the core file size (KB)
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# - data - max data size (KB)
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# - fsize - maximum filesize (KB)
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# - memlock - max locked-in-memory address space (KB)
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# - nofile - max number of open file descriptors
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# - rss - max resident set size (KB)
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# - stack - max stack size (KB)
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# - cpu - max CPU time (MIN)
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# - nproc - max number of processes
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# - as - address space limit (KB)
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# - maxlogins - max number of logins for this user
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# - maxsyslogins - max number of logins on the system
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# - priority - the priority to run user process with
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# - locks - max number of file locks the user can hold
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# - sigpending - max number of pending signals
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# - msgqueue - max memory used by POSIX message queues (bytes)
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# - nice - max nice priority allowed to raise to values: [-20, 19]
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# - rtprio - max realtime priority
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# - chroot - change root to directory (Debian-specific)
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#
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#
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# <value> is related with <item>:
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# All items support the values -1, unlimited or infinity indicating
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# no limit, except for priority and nice.
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#
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# If a hard limit or soft limit of a resource is set to a valid value,
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# but outside of the supported range of the local system, the system
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# may reject the new limit or unexpected behavior may occur. If the
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# control value required is used, the module will reject the login if
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# a limit could not be set.
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#
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# <domain> <type> <item> <value>
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#
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# * soft core 0
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# root hard core 100000
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# * hard rss 10000
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# @student hard nproc 20
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# @faculty soft nproc 20
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# @faculty hard nproc 50
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# ftp hard nproc 0
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# ftp - chroot /ftp
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# @student - maxlogins 4
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# End of file
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12
src/sonic-host-services-data/templates/pam_limits.j2
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12
src/sonic-host-services-data/templates/pam_limits.j2
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#THIS IS AN AUTO-GENERATED FILE
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#
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# This file generate by j2 template file: src/sonic-host-services-data/templates/pam_limits.j2
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#
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# /etc/pam.d/pam-limits settings common to all services
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# This file is included from other service-specific PAM config files,
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# and should contain a list of the authentication modules that define
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# the central authentication scheme for use on the system
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# (e.g., /etc/shadow, LDAP, Kerberos, etc.). The default is to use the
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# traditional Unix authentication mechanisms.
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#
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# here are the per-package modules (the "Primary" block)
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@ -25,6 +25,10 @@ PAM_RADIUS_AUTH_CONF_TEMPLATE = "/usr/share/sonic/templates/pam_radius_auth.conf
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NSS_CONF = "/etc/nsswitch.conf"
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ETC_PAMD_SSHD = "/etc/pam.d/sshd"
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ETC_PAMD_LOGIN = "/etc/pam.d/login"
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PAM_LIMITS_CONF_TEMPLATE = "/usr/share/sonic/templates/pam_limits.j2"
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LIMITS_CONF_TEMPLATE = "/usr/share/sonic/templates/limits.conf.j2"
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PAM_LIMITS_CONF = "/etc/pam.d/pam-limits-conf"
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LIMITS_CONF = "/etc/security/limits.conf"
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# TACACS+
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TACPLUS_SERVER_PASSKEY_DEFAULT = ""
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@ -966,6 +970,64 @@ class NtpCfg(object):
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syslog.syslog(syslog.LOG_INFO, 'ntp server update, restarting ntp-config, ntp servers configured {}'.format(self.ntp_servers))
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run_cmd(cmd)
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class PamLimitsCfg(object):
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"""
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PamLimit Config Daemon
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1) The pam_limits PAM module sets limits on the system resources that can be obtained in a user-session.
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2) Purpose of this daemon is to render pam_limits config file.
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"""
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def __init__(self, config_db):
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self.config_db = config_db
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self.hwsku = ""
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self.type = ""
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# Load config from ConfigDb and render config file/
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def update_config_file(self):
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device_metadata = self.config_db.get_table('DEVICE_METADATA')
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if "localhost" not in device_metadata:
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return
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self.read_localhost_config(device_metadata["localhost"])
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self.render_conf_file()
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# Read localhost config
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def read_localhost_config(self, localhost):
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if "hwsku" in localhost:
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self.hwsku = localhost["hwsku"]
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else:
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self.hwsku = ""
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if "type" in localhost:
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self.type = localhost["type"]
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else:
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self.type = ""
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# Render pam_limits config files
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def render_conf_file(self):
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env = jinja2.Environment(loader=jinja2.FileSystemLoader('/'), trim_blocks=True)
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env.filters['sub'] = sub
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try:
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template_file = os.path.abspath(PAM_LIMITS_CONF_TEMPLATE)
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template = env.get_template(template_file)
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pam_limits_conf = template.render(
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hwsku=self.hwsku,
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type=self.type)
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with open(PAM_LIMITS_CONF, 'w') as f:
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f.write(pam_limits_conf)
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template_file = os.path.abspath(LIMITS_CONF_TEMPLATE)
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template = env.get_template(template_file)
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limits_conf = template.render(
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hwsku=self.hwsku,
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type=self.type)
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with open(LIMITS_CONF, 'w') as f:
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f.write(limits_conf)
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except Exception as e:
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syslog.syslog(syslog.LOG_ERR,
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"modify pam_limits config file failed with exception: {}"
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.format(e))
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class HostConfigDaemon:
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def __init__(self):
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# Just a sanity check to verify if the CONFIG_DB has been initialized
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@ -1007,6 +1069,9 @@ class HostConfigDaemon:
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self.hostname_cache=""
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self.aaacfg = AaaCfg()
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# Initialize PamLimitsCfg
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self.pamLimitsCfg = PamLimitsCfg(self.config_db)
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self.pamLimitsCfg.update_config_file()
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def load(self):
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aaa = self.config_db.get_table('AAA')
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