CVE-2014-9422 (published 2015-02-19T11:59Z)

The check_rpcsec_auth function in kadmin/server/kadm_rpc_svc.c in kadmind in MIT Kerberos 5 (aka krb5) through 1.11.5, 1.12.x through 1.12.2, and 1.13.x before 1.13.1 allows remote authenticated users to bypass a kadmin/* authorization check and obtain administrative access by leveraging access to a two-component principal with an initial "kadmind" substring, as demonstrated by a "ka/x" principal.

Severity: MEDIUM
CVSS v2 base score: 6.1 (AV:N/AC:H/Au:S/C:P/I:P/A:C)

Weakness information:
cwe_id: CWE-284
cwe_name: Improper Access Control
description: The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor.
extended_description: 
            Access control involves the use of several protection mechanisms such as:
            
               Authentication (proving the identity of an actor)
               Authorization (ensuring that a given actor can access a resource), and
               Accountability (tracking of activities that were performed)
            
            When any mechanism is not applied or otherwise fails, attackers can compromise the security of the product by gaining privileges, reading sensitive information, executing commands, evading detection, etc.
            There are two distinct behaviors that can introduce access control weaknesses:
               
                  Specification: incorrect privileges, permissions, ownership, etc. are explicitly specified for either the user or the resource (for example, setting a password file to be world-writable, or giving administrator capabilities to a guest user). This action could be performed by the program or the administrator.
                  Enforcement: the mechanism contains errors that prevent it from properly enforcing the specified access control requirements (e.g., allowing the user to specify their own privileges, or allowing a syntactically-incorrect ACL to produce insecure settings). This problem occurs within the program itself, in that it does not actually enforce the intended security policy that the administrator specifies.
               
         
		 

Fix information:
repo_url: https://github.com/krb5/krb5
commit_details: repo_url: https://github.com/krb5/krb5
author: Greg Hudson
author_date: 2014-12-29 13:27:42-05:00
msg: Fix kadmind server validation [CVE-2014-9422]

[MITKRB5-SA-2015-001] In kadmind's check_rpcsec_auth(), use
data_eq_string() instead of strncmp() to check components of the
server principal, so that we don't erroneously match left substrings
of "kadmin", "history", or the realm.

ticket: 8057 (new)
target_version: 1.13.1
tags: pullup
repository: repo_url: https://github.com/krb5/krb5
repo_name: krb5/krb5
description: mirror of MIT krb5 repository
repo_language: C
owner: krb5
file_changes: filename: kadm_rpc_svc.c
change_type: ModificationType.MODIFY
diff: @@ -4,7 +4,7 @@
  *
  */
 
-#include <k5-platform.h>
+#include <k5-int.h>
 #include <gssrpc/rpc.h>
 #include <gssapi/gssapi_krb5.h> /* for gss_nt_krb5_name */
 #include <syslog.h>
@@ -296,14 +296,8 @@ check_rpcsec_auth(struct svc_req *rqstp)
      c1 = krb5_princ_component(kctx, princ, 0);
      c2 = krb5_princ_component(kctx, princ, 1);
      realm = krb5_princ_realm(kctx, princ);
-     if (strncmp(handle->params.realm, realm->data, realm->length) == 0
-	 && strncmp("kadmin", c1->data, c1->length) == 0) {
-
-	  if (strncmp("history", c2->data, c2->length) == 0)
-	       goto fail_princ;
-	  else
-	       success = 1;
-     }
+     success = data_eq_string(*realm, handle->params.realm) &&
+	     data_eq_string(*c1, "kadmin") && !data_eq_string(*c2, "history");
 
 fail_princ:
      if (!success) {

programming_language: C