From fd6d67001c762919ad3769865285a5a8c76630a1 Mon Sep 17 00:00:00 2001
From: Christian Poessinger <christian@poessinger.com>
Date: Sun, 9 Feb 2020 10:44:23 +0100
Subject: snmp: T1931: harden logic when re-reading config fpr encrypted keys

---
 src/conf_mode/snmp.py | 71 +++++++++++++++++++++++++++++----------------------
 1 file changed, 40 insertions(+), 31 deletions(-)

diff --git a/src/conf_mode/snmp.py b/src/conf_mode/snmp.py
index 6cccf2032..cd63d6d62 100755
--- a/src/conf_mode/snmp.py
+++ b/src/conf_mode/snmp.py
@@ -743,8 +743,8 @@ def apply(snmp):
         # Passwords are not available immediately in the configuration file,
         # after daemon startup - we wait until they have been processed by
         # snmpd, which we see when a magic line appears in this file.
-        snmpReady = False
-        while not snmpReady:
+        ready = False
+        while not ready:
             while not os.path.exists(config_file_user):
                 sleep(0.1)
 
@@ -752,37 +752,46 @@ def apply(snmp):
                 for line in f:
                     # Search for our magic string inside the file
                     if '**** DO NOT EDIT THIS FILE ****' in line:
-                        snmpReady = True
+                        ready = True
                         break
 
-        # Back in the Perl days the configuration was re-read and any
-        # plaintext password inside the configuration was replaced by
-        # the encrypted one which can be found in 'config_file_user'
-        with open(config_file_user, 'r') as f:
-            engineID = ''
-            for line in f:
-                if line.startswith('oldEngineID'):
-                    string = line.split(' ')
-                    engineID = string[1]
-
-                if line.startswith('usmUser'):
-                    string = line.split(' ')
-                    cfg = {
-                        'user': string[4].replace(r'"', ''),
-                        'auth_pw': string[8],
-                        'priv_pw': string[10]
-                    }
-                    # No need to take care about the VyOS internal user
-                    if cfg['user'] == snmp['vyos_user']:
-                        continue
-
-                    # Now update the running configuration
-                    #
-                    # Currently when executing os.system() the environment does not have the vyos_libexec_dir variable set, see T685
-                    os.system('vyos_libexec_dir=/usr/libexec/vyos /opt/vyatta/sbin/my_set service snmp v3 user "{0}" auth encrypted-key {1} > /dev/null'.format(cfg['user'], cfg['auth_pw']))
-                    os.system('vyos_libexec_dir=/usr/libexec/vyos /opt/vyatta/sbin/my_set service snmp v3 user "{0}" privacy encrypted-key {1} > /dev/null'.format(cfg['user'], cfg['priv_pw']))
-                    os.system('vyos_libexec_dir=/usr/libexec/vyos /opt/vyatta/sbin/my_delete service snmp v3 user "{0}" auth plaintext-key > /dev/null'.format(cfg['user']))
-                    os.system('vyos_libexec_dir=/usr/libexec/vyos /opt/vyatta/sbin/my_delete service snmp v3 user "{0}" privacy plaintext-key > /dev/null'.format(cfg['user']))
+        # net-snmp is now regenerating the configuration file in the background
+        # thus we need to re-open and re-read the file as the content changed.
+        # After that we can no read the encrypted password from the config and
+        # replace the CLI plaintext password with its encrypted version.
+        ready = False
+        while not ready:
+            while not os.path.exists(config_file_user):
+                sleep(0.1)
+
+            with open(config_file_user, 'r') as f:
+                engineID = ''
+                for line in f:
+                    if line.startswith('oldEngineID'):
+                        string = line.split(' ')
+                        engineID = string[1]
+
+                    if line.startswith('usmUser'):
+                        string = line.split(' ')
+                        cfg = {
+                            'user': string[4].replace(r'"', ''),
+                            'auth_pw': string[8],
+                            'priv_pw': string[10]
+                        }
+                        # No need to take care about the VyOS internal user
+                        if cfg['user'] == snmp['vyos_user']:
+                            continue
+
+                        # Now update the running configuration
+                        #
+                        # Currently when executing os.system() the environment does not have the vyos_libexec_dir variable set, see T685
+                        os.system('vyos_libexec_dir=/usr/libexec/vyos /opt/vyatta/sbin/my_set service snmp v3 user "{0}" auth encrypted-key {1} > /dev/null'.format(cfg['user'], cfg['auth_pw']))
+                        os.system('vyos_libexec_dir=/usr/libexec/vyos /opt/vyatta/sbin/my_set service snmp v3 user "{0}" privacy encrypted-key {1} > /dev/null'.format(cfg['user'], cfg['priv_pw']))
+                        os.system('vyos_libexec_dir=/usr/libexec/vyos /opt/vyatta/sbin/my_delete service snmp v3 user "{0}" auth plaintext-key > /dev/null'.format(cfg['user']))
+                        os.system('vyos_libexec_dir=/usr/libexec/vyos /opt/vyatta/sbin/my_delete service snmp v3 user "{0}" privacy plaintext-key > /dev/null'.format(cfg['user']))
+
+                        # set marker
+                        ready = True
 
         # Enable AgentX in FRR
         os.system('vtysh -c "configure terminal" -c "agentx" >/dev/null')
-- 
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