snmp: T2687: precalculate snmpv3 encrypted keys

As of now when adding new credentials for any SNMPv3 user we submit the
credential either plaintext or encrypted. A plaintext credential will be hashed
by SNMPd in the background and then passed back into the CLI so it's not stored
in cleartext. This feels like the wrong way in changing the CLI content with
data produced by a 3rd party daemon which implements the service.

It feels like the tail wiggles the entire dog.

This should be changed in the following way:
- After retrieving the plaintext password from CLI, use Python to hash the key
  in advance
- Re-populate the encrypted key into the CLI and drop the plaintext one
- Generate service configuration and continue startup of SNMPd

This also fixes a race condition when SNMPd started up but not properly
provided the hasehd keys in the configuration resulting in a ConfigurationError.
Now as we also support binding SNMPd to a VRF this fixes a deadlock situation
on bootup as we can only bind late to the VRF and require up to 5 restarts of
the service - but the service will never start.

1 files changed, 89 insertions, 0 deletions

diff --git a/src/migration-scripts/snmp/1-to-2 b/src/migration-scripts/snmp/1-to-2
new file mode 100755
index 000000000..466a624e6
--- /dev/null
+++ b/src/migration-scripts/snmp/1-to-2
@@ -0,0 +1,89 @@
+#!/usr/bin/env python3
+#
+# Copyright (C) 2020 VyOS maintainers and contributors
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 or later as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from sys import argv, exit
+from vyos.configtree import ConfigTree
+
+def migrate_keys(config, path):
+    # authentication: rename node 'encrypted-key' -> 'encrypted-password'
+    config_path_auth = path + ['auth', 'encrypted-key']
+    if config.exists(config_path_auth):
+        config.rename(config_path_auth, 'encrypted-password')
+        config_path_auth = path + ['auth', 'encrypted-password']
+
+        # remove leading '0x' from string if present
+        tmp = config.return_value(config_path_auth)
+        if tmp.startswith(prefix):
+            tmp = tmp.replace(prefix, '')
+            config.set(config_path_auth, value=tmp)
+
+    # privacy: rename node 'encrypted-key' -> 'encrypted-password'
+    config_path_priv = path + ['privacy', 'encrypted-key']
+    if config.exists(config_path_priv):
+        config.rename(config_path_priv, 'encrypted-password')
+        config_path_priv = path + ['privacy', 'encrypted-password']
+
+        # remove leading '0x' from string if present
+        tmp = config.return_value(config_path_priv)
+        if tmp.startswith(prefix):
+            tmp = tmp.replace(prefix, '')
+            config.set(config_path_priv, value=tmp)
+
+if __name__ == '__main__':
+    if (len(argv) < 1):
+        print("Must specify file name!")
+        exit(1)
+
+    file_name = argv[1]
+
+    with open(file_name, 'r') as f:
+        config_file = f.read()
+
+    config = ConfigTree(config_file)
+    config_base = ['service', 'snmp', 'v3']
+
+    if not config.exists(config_base):
+        # Nothing to do
+        exit(0)
+    else:
+        # We no longer support hashed values prefixed with '0x' to unclutter
+        # CLI and also calculate the hases in advance instead of retrieving
+        # them after service startup - which was always a bad idea
+        prefix = '0x'
+
+        config_engineid = config_base + ['engineid']
+        if config.exists(config_engineid):
+            tmp = config.return_value(config_engineid)
+            if tmp.startswith(prefix):
+                tmp = tmp.replace(prefix, '')
+                config.set(config_engineid, value=tmp)
+
+        config_user = config_base + ['user']
+        if config.exists(config_user):
+            for user in config.list_nodes(config_user):
+                migrate_keys(config, config_user + [user])
+
+        config_trap = config_base + ['trap-target']
+        if config.exists(config_trap):
+            for trap in config.list_nodes(config_trap):
+                migrate_keys(config, config_trap + [trap])
+
+        try:
+            with open(file_name, 'w') as f:
+                f.write(config.to_string())
+        except OSError as e:
+            print("Failed to save the modified config: {}".format(e))
+            exit(1)