Let certmanager and sshsignhost authenticate to Vault by kubernetes auth

Both helpers are run server-side by generate() during catalog compilation and
only speak AppRole, whose token_bound_cidrs pin them to the six legacy VM
masters, so the autoscaled k8s compilers cannot obtain a token and any compile
needing a cert or a signed host key fails there.

- Add a kubernetes login branch that reads the service account JWT and posts it
  to auth/<k8s_mount>/login, selected by an auth_method config key
- Add auth_method, k8s_mount, k8s_role and jwt_path class parameters, defaulting
  to approle so the VM masters render and behave as before
- Render role_id and approle_path only for the approle case
- Report a missing JWT, a rejected login or an unknown auth_method on stderr
  instead of falling back or raising
- Point sshsignhost at the sshca mount and signhost role that Vault actually has

Needs terraform-vault #152, already applied.

hieradata/roles/infra/puppet/master.yaml

@@ -47,9 +47,9 @@ profiles::helpers::certmanager::vault_config:
 
 profiles::helpers::sshsignhost::vault_config:
   addr: 'https://vault.service.consul:8200'
-  mount_point: 'ssh-host-signer'
+  mount_point: 'sshca'
   approle_path: 'approle'
-  role_name: 'hostrole'
+  role_name: 'signhost'
   output_path: '/tmp/sshsignhost'
   role_id: "%{lookup('sshsignhost::role_id')}"
 

site/profiles/manifests/helpers/certmanager.pp

@@ -7,6 +7,10 @@ class profiles::helpers::certmanager (
   Stdlib::AbsolutePath  $venv_path = "${base_path}/venv",
   Stdlib::AbsolutePath  $config_path = "${base_path}/config.yaml",
   Hash                  $vault_config = {},
+  Enum['approle','kubernetes'] $auth_method = 'approle',
+  String[1]             $k8s_mount = 'k8s/au/syd1',
+  String[1]             $k8s_role = 'puppet_certmanager',
+  Stdlib::AbsolutePath  $jwt_path = '/var/run/secrets/kubernetes.io/serviceaccount/token',
   String                $owner = 'root',
   String                $group = 'root',
   Boolean               $systempkgs = false,
@@ -16,6 +20,14 @@ class profiles::helpers::certmanager (
 
   if $::facts['python3_version'] {
 
+    # class parameters supply the auth defaults; $vault_config may override them
+    $vault_settings = {
+      'auth_method' => $auth_method,
+      'k8s_mount'   => $k8s_mount,
+      'k8s_role'    => $k8s_role,
+      'jwt_path'    => $jwt_path,
+    } + $vault_config
+
     $python_version = $version ? {
       'system' => $::facts['python3_version'],
       default  => $version,

site/profiles/manifests/helpers/sshsignhost.pp

@@ -7,6 +7,10 @@ class profiles::helpers::sshsignhost (
   Stdlib::AbsolutePath  $venv_path = "${base_path}/venv",
   Stdlib::AbsolutePath  $config_path = "${base_path}/config.yaml",
   Hash                  $vault_config = {},
+  Enum['approle','kubernetes'] $auth_method = 'approle',
+  String[1]             $k8s_mount = 'k8s/au/syd1',
+  String[1]             $k8s_role = 'puppet_sshsigner',
+  Stdlib::AbsolutePath  $jwt_path = '/var/run/secrets/kubernetes.io/serviceaccount/token',
   String                $owner = 'root',
   String                $group = 'root',
   Boolean               $systempkgs = false,
@@ -16,6 +20,14 @@ class profiles::helpers::sshsignhost (
 
   if $::facts['python3_version'] {
 
+    # class parameters supply the auth defaults; $vault_config may override them
+    $vault_settings = {
+      'auth_method' => $auth_method,
+      'k8s_mount'   => $k8s_mount,
+      'k8s_role'    => $k8s_role,
+      'jwt_path'    => $jwt_path,
+    } + $vault_config
+
     $python_version = $version ? {
       'system' => $::facts['python3_version'],
       default  => $version,

site/profiles/templates/helpers/certmanager.erb

@@ -1,6 +1,7 @@
 #!<%= @venv_path %>/bin/python
 
 import argparse
+import sys
 import requests
 import json
 import os
@@ -25,14 +26,50 @@ def authenticate_approle(vault_config):
         auth_response = response.json()
         return auth_response['auth']['client_token']
     else:
-        print(f"Error authenticating with AppRole: {response.text}")
+        print(f"Error authenticating with AppRole: {response.text}", file=sys.stderr)
         return None
 
+class VaultAuthError(Exception):
+    pass
+
+def authenticate_kubernetes(vault_config):
+    jwt_path = vault_config.get('jwt_path') or '/var/run/secrets/kubernetes.io/serviceaccount/token'
+    try:
+        with open(jwt_path, 'r') as file:
+            jwt = file.read().strip()
+    except OSError as error:
+        raise VaultAuthError(f"cannot read service account token '{jwt_path}': {error}")
+    if not jwt:
+        raise VaultAuthError(f"service account token '{jwt_path}' is empty")
+    url = f"{vault_config['addr']}/v1/auth/{vault_config['k8s_mount']}/login"
+    payload = {
+        "role": vault_config['k8s_role'],
+        "jwt": jwt,
+    }
+    response = requests.post(url, json=payload, verify=False)
+    if response.status_code != 200:
+        raise VaultAuthError(
+            f"kubernetes login as role '{vault_config['k8s_role']}' on mount "
+            f"'{vault_config['k8s_mount']}' was rejected ({response.status_code}): {response.text}"
+        )
+    return response.json()['auth']['client_token']
+
+def authenticate(vault_config):
+    auth_method = vault_config.get('auth_method', 'approle')
+    if auth_method == 'approle':
+        client_token = authenticate_approle(vault_config)
+        if not client_token:
+            raise VaultAuthError("approle login was rejected")
+        return client_token
+    if auth_method == 'kubernetes':
+        return authenticate_kubernetes(vault_config)
+    raise VaultAuthError(f"unsupported auth_method '{auth_method}': expected 'approle' or 'kubernetes'")
+
 def request_certificate(common_name, alt_names, ip_sans, expiry_days, vault_config):
-    # Authenticate using AppRole and get a token
-    client_token = authenticate_approle(vault_config)
-    if not client_token:
-        print("Failed to authenticate with Vault using AppRole.")
+    try:
+        client_token = authenticate(vault_config)
+    except VaultAuthError as error:
+        print(f"Failed to authenticate with Vault: {error}", file=sys.stderr)
         return None
 
     url = f"{vault_config['addr']}/v1/{vault_config['mount_point']}/issue/{vault_config['role_name']}"
@@ -47,7 +84,7 @@ def request_certificate(common_name, alt_names, ip_sans, expiry_days, vault_conf
     if response.status_code == 200:
         return response.json()
     else:
-        print(f"Error requesting certificate: {response.text}")
+        print(f"Error requesting certificate: {response.text}", file=sys.stderr)
         return None
 
 def save_cert_files(certificate_response, common_name, compress, config, json_output):
@@ -95,7 +132,8 @@ def main(config_file):
         else:
             save_cert_files(certificate_response, args.common_name, args.compress, config, False)
     else:
-        print("Failed to obtain certificate.")
+        print("Failed to obtain certificate.", file=sys.stderr)
+        exit(1)
 
 if __name__ == "__main__":
     config_file = '<%= @config_path %>'

site/profiles/templates/helpers/certmanager_config.yaml.erb

@@ -1,7 +1,14 @@
 vault:
-  addr: '<%= @vault_config['addr'] %>'
-  role_id: '<%= @vault_config['role_id'] %>'
-  approle_path: '<%= @vault_config['approle_path'] %>'
-  mount_point: '<%= @vault_config['mount_point'] %>'
-  role_name: '<%= @vault_config['role_name'] %>'
-output_path: '<%= @vault_config['output_path'] %>'
+  addr: '<%= @vault_settings['addr'] %>'
+  auth_method: '<%= @vault_settings['auth_method'] %>'
+<% if @vault_settings['auth_method'] == 'kubernetes' -%>
+  k8s_mount: '<%= @vault_settings['k8s_mount'] %>'
+  k8s_role: '<%= @vault_settings['k8s_role'] %>'
+  jwt_path: '<%= @vault_settings['jwt_path'] %>'
+<% else -%>
+  role_id: '<%= @vault_settings['role_id'] %>'
+  approle_path: '<%= @vault_settings['approle_path'] %>'
+<% end -%>
+  mount_point: '<%= @vault_settings['mount_point'] %>'
+  role_name: '<%= @vault_settings['role_name'] %>'
+output_path: '<%= @vault_settings['output_path'] %>'

site/profiles/templates/helpers/sshsignhost.erb

@@ -1,5 +1,6 @@
 #!<%= @venv_path %>/bin/python
 import argparse
+import sys
 import requests
 import json
 import yaml
@@ -22,14 +23,50 @@ def authenticate_approle(vault_config):
         auth_response = response.json()
         return auth_response['auth']['client_token']
     else:
-        print(f"Error authenticating with AppRole: {response.text}")
+        print(f"Error authenticating with AppRole: {response.text}", file=sys.stderr)
         return None
 
+class VaultAuthError(Exception):
+    pass
+
+def authenticate_kubernetes(vault_config):
+    jwt_path = vault_config.get('jwt_path') or '/var/run/secrets/kubernetes.io/serviceaccount/token'
+    try:
+        with open(jwt_path, 'r') as file:
+            jwt = file.read().strip()
+    except OSError as error:
+        raise VaultAuthError(f"cannot read service account token '{jwt_path}': {error}")
+    if not jwt:
+        raise VaultAuthError(f"service account token '{jwt_path}' is empty")
+    url = f"{vault_config['addr']}/v1/auth/{vault_config['k8s_mount']}/login"
+    payload = {
+        "role": vault_config['k8s_role'],
+        "jwt": jwt,
+    }
+    response = requests.post(url, json=payload, verify=False)
+    if response.status_code != 200:
+        raise VaultAuthError(
+            f"kubernetes login as role '{vault_config['k8s_role']}' on mount "
+            f"'{vault_config['k8s_mount']}' was rejected ({response.status_code}): {response.text}"
+        )
+    return response.json()['auth']['client_token']
+
+def authenticate(vault_config):
+    auth_method = vault_config.get('auth_method', 'approle')
+    if auth_method == 'approle':
+        client_token = authenticate_approle(vault_config)
+        if not client_token:
+            raise VaultAuthError("approle login was rejected")
+        return client_token
+    if auth_method == 'kubernetes':
+        return authenticate_kubernetes(vault_config)
+    raise VaultAuthError(f"unsupported auth_method '{auth_method}': expected 'approle' or 'kubernetes'")
+
 def sign_ssh_certificate(vault_config, public_key, valid_principals, ttl):
-    # Authenticate using AppRole and get a token
-    client_token = authenticate_approle(vault_config)
-    if not client_token:
-        print("Failed to authenticate with Vault using AppRole.")
+    try:
+        client_token = authenticate(vault_config)
+    except VaultAuthError as error:
+        print(f"Failed to authenticate with Vault: {error}", file=sys.stderr)
         return None
 
     # Prepare the SSH certificate signing request
@@ -47,7 +84,7 @@ def sign_ssh_certificate(vault_config, public_key, valid_principals, ttl):
     if response.status_code == 200:
         return response.json()
     else:
-        print(f"Error requesting certificate: {response.text}")
+        print(f"Error requesting certificate: {response.text}", file=sys.stderr)
         return None
 
 def main(config_file):
@@ -75,7 +112,7 @@ def main(config_file):
         else:
             print(response['data']['signed_key'])
     else:
-        print("Error: The response does not contain the expected data.")
+        print("Error: The response does not contain the expected data.", file=sys.stderr)
         exit(1)
 
 if __name__ == "__main__":

site/profiles/templates/helpers/sshsignhost_config.yaml.erb

@@ -1,7 +1,14 @@
 vault:
-  addr: '<%= @vault_config['addr'] %>'
-  role_id: '<%= @vault_config['role_id'] %>'
-  approle_path: '<%= @vault_config['approle_path'] %>'
-  mount_point: '<%= @vault_config['mount_point'] %>'
-  role_name: '<%= @vault_config['role_name'] %>'
-output_path: '<%= @vault_config['output_path'] %>'
+  addr: '<%= @vault_settings['addr'] %>'
+  auth_method: '<%= @vault_settings['auth_method'] %>'
+<% if @vault_settings['auth_method'] == 'kubernetes' -%>
+  k8s_mount: '<%= @vault_settings['k8s_mount'] %>'
+  k8s_role: '<%= @vault_settings['k8s_role'] %>'
+  jwt_path: '<%= @vault_settings['jwt_path'] %>'
+<% else -%>
+  role_id: '<%= @vault_settings['role_id'] %>'
+  approle_path: '<%= @vault_settings['approle_path'] %>'
+<% end -%>
+  mount_point: '<%= @vault_settings['mount_point'] %>'
+  role_name: '<%= @vault_settings['role_name'] %>'
+output_path: '<%= @vault_settings['output_path'] %>'