Merge pull request #9108 from RasmusWL/promote-pam

Python: Promote `py/pam-auth-bypass`

Author: tausbn

python/ql/src/experimental/Security/CWE-285/PamAuthorization.qhelp renamed to python/ql/src/Security/CWE-285/PamAuthorization.qhelp

@@ -9,7 +9,9 @@
     <p>
       A
       <code>pam_authenticate</code>
-      only verifies the credentials of a user. It does not check if a user has an appropriate authorization to actually login. This means a user with a expired login or a password can still access the system.
+      only verifies the credentials of a user. It does not check if a user has an
+      appropriate authorization to actually login. This means a user with an expired
+      login or a password can still access the system.
     </p>
 
   </overview>
@@ -26,7 +28,9 @@
 
   <example>
     <p>
-      In the following example, the code only checks the credentials of a user. Hence, in this case, a user expired with expired creds can still login. This can be verified by creating a new user account, expiring it with
+      In the following example, the code only checks the credentials of a user. Hence,
+      in this case, a user with expired credentials can still login. This can be
+      verified by creating a new user account, expiring it with
       <code>chage -E0 `username` </code>
       and then trying to log in.
     </p>
@@ -46,4 +50,4 @@
       <a href="https://man7.org/linux/man-pages/man3/pam_acct_mgmt.3.html">pam_acct_mgmt</a>
     </li>
   </references>
-</qhelp>
+</qhelp>

python/ql/src/experimental/Security/CWE-285/PamAuthorization.ql renamed to python/ql/src/Security/CWE-285/PamAuthorization.ql

@@ -1,8 +1,9 @@
 /**
- * @name Authorization bypass due to incorrect usage of PAM
- * @description Using only the `pam_authenticate` call to check the validity of a login can lead to a authorization bypass.
+ * @name PAM authorization bypass due to incorrect usage
+ * @description Not using `pam_acct_mgmt` after `pam_authenticate` to check the validity of a login can lead to authorization bypass.
  * @kind problem
  * @problem.severity warning
+ * @security-severity 8.1
  * @precision high
  * @id py/pam-auth-bypass
  * @tags security
@@ -33,4 +34,5 @@ where
     acctMgmtCall = libPam().getMember("pam_acct_mgmt").getACall() and
     DataFlow::localFlow(handle, acctMgmtCall.getArg(0))
   )
-select authenticateCall, "This PAM authentication call may be lead to an authorization bypass."
+select authenticateCall,
+  "This PAM authentication call may lead to an authorization bypass, since 'pam_acct_mgmt' is not called afterwards."

python/ql/src/Security/CWE-285/PamAuthorizationBad.py

@@ -0,0 +1,19 @@
+libpam                    = CDLL(find_library("pam"))
+
+pam_authenticate          = libpam.pam_authenticate
+pam_authenticate.restype  = c_int
+pam_authenticate.argtypes = [PamHandle, c_int]
+
+def authenticate(username, password, service='login'):
+    def my_conv(n_messages, messages, p_response, app_data):
+        """
+        Simple conversation function that responds to any prompt where the echo is off with the supplied password
+        """
+        ...
+
+    handle = PamHandle()
+    conv   = PamConv(my_conv, 0)
+    retval = pam_start(service, username, byref(conv), byref(handle))
+
+    retval = pam_authenticate(handle, 0)
+    return retval == 0

python/ql/src/Security/CWE-285/PamAuthorizationGood.py

@@ -0,0 +1,25 @@
+libpam                    = CDLL(find_library("pam"))
+
+pam_authenticate          = libpam.pam_authenticate
+pam_authenticate.restype  = c_int
+pam_authenticate.argtypes = [PamHandle, c_int]
+
+pam_acct_mgmt          = libpam.pam_acct_mgmt
+pam_acct_mgmt.restype  = c_int
+pam_acct_mgmt.argtypes = [PamHandle, c_int]
+
+def authenticate(username, password, service='login'):
+    def my_conv(n_messages, messages, p_response, app_data):
+        """
+        Simple conversation function that responds to any prompt where the echo is off with the supplied password
+        """
+        ...
+
+    handle = PamHandle()
+    conv   = PamConv(my_conv, 0)
+    retval = pam_start(service, username, byref(conv), byref(handle))
+
+    retval = pam_authenticate(handle, 0)
+    if retval == 0:
+        retval = pam_acct_mgmt(handle, 0)
+    return retval == 0

python/ql/src/change-notes/2022-05-10-promote-pam-authentication-bypass.md

@@ -0,0 +1,4 @@
+---
+category: newQuery
+---
+* The query "PAM authorization bypass due to incorrect usage" (`py/pam-auth-bypass`) has been promoted from experimental to the main query pack. Its results will now appear by default. This query was originally [submitted as an experimental query by @porcupineyhairs](https://github.com/github/codeql/pull/8595).

python/ql/src/experimental/Security/CWE-285/PamAuthorizationBad.py

@@ -0,0 +1 @@
+| pam_test.py:48:18:48:44 | ControlFlowNode for pam_authenticate() | This PAM authentication call may lead to an authorization bypass, since 'pam_acct_mgmt' is not called afterwards. |