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Fix flaws in LDAP DN checking
KDB_TL_USER_INFO tl-data is intended to be internal to the LDAP KDB module, and not used in disk or wire principal entries. Prevent kadmin clients from sending KDB_TL_USER_INFO tl-data by giving it a type number less than 256 and filtering out type numbers less than 256 in kadm5_create_principal_3(). (We already filter out low type numbers in kadm5_modify_principal()). In the LDAP KDB module, if containerdn and linkdn are both specified in a put_principal operation, check both linkdn and the computed standalone_principal_dn for container membership. To that end, factor out the checks into helper functions and call them on all applicable client-influenced DNs. CVE-2018-5729: In MIT krb5 1.6 or later, an authenticated kadmin user with permission to add principals to an LDAP Kerberos database can cause a null dereference in kadmind, or circumvent a DN container check, by supplying tagged data intended to be internal to the database module. Thanks to Sharwan Ram and Pooja Anil for discovering the potential null dereference. CVE-2018-5730: In MIT krb5 1.6 or later, an authenticated kadmin user with permission to add principals to an LDAP Kerberos database can circumvent a DN containership check by supplying both a "linkdn" and "containerdn" database argument, or by supplying a DN string which is a left extension of a container DN string but is not hierarchically within the container DN. ticket: 8643 (new) tags: pullup target_version: 1.16-next target_version: 1.15-next
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