The _checkPolkitPrivilege function in serviceHelper.py in Back In Time (aka backintime) 1.1.18 and earlier uses a deprecated polkit authorization method (unix-process) that is subject to a race condition (time of check, time of use). With this authorization method, the owner of a process requesting a polkit operation is checked by polkitd via /proc//status, by which time the requesting process may have been replaced by a different process with the same PID that has different privileges then the original requester.
The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Backintime | Backintime_project | * | 1.1.18 (including) |
| Backintime | Ubuntu | artful | * |
| Backintime | Ubuntu | esm-apps/xenial | * |
| Backintime | Ubuntu | precise | * |
| Backintime | Ubuntu | trusty | * |
| Backintime | Ubuntu | upstream | * |
| Backintime | Ubuntu | xenial | * |
| Backintime | Ubuntu | yakkety | * |
| Backintime | Ubuntu | zesty | * |
A race condition occurs within concurrent environments, and it is effectively a property of a code sequence. Depending on the context, a code sequence may be in the form of a function call, a small number of instructions, a series of program invocations, etc. A race condition violates these properties, which are closely related:
A race condition exists when an “interfering code sequence” can still access the shared resource, violating exclusivity. The interfering code sequence could be “trusted” or “untrusted.” A trusted interfering code sequence occurs within the product; it cannot be modified by the attacker, and it can only be invoked indirectly. An untrusted interfering code sequence can be authored directly by the attacker, and typically it is external to the vulnerable product.