Kaprica Security (KPRCA)
This CB emulates an online job application form. An applicant moves through several pages of grouped questions (Candiate Info, Education, Address, etc etc) and is forced to enter each question on the form before continuing to the next page. The pages are seqential and, once completed, can be revisited using the "prev" command. Completed pages can have indivial questions updated with new answers or an applicant can simply review his or her answers.
Once the form is completed the user can "submit" the form by exiting, or "discard" by using ctrl-c. The two are functionally equivalent, but we would hate to feel like someone didn't have a chance to throw their application away.
The code attempts to model a web interface. Each input has a textfield, a buffer to hold the response, and a verification function that makes sure the input is valid.
And applicant can enter input when asked a question, or navigate accross the application with the following commands:
All commands begin with '' and may be entered at any time during the CB prev
When an entry is updated with the **update function a compare is made using
strncmp between the existing entry data and the data the entry is to be updated with. If this check passes, the new data is copied over the old data using
strcpy. The logical flaw is that the length argument to
strncmp is the length of the old data, not the new data. Since entries are stored on the heap, if the newer data is significantly bigger than the old data, a heap based buffer overflow can occur.
CWE-120: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') CWE-122: Heap-based Buffer Overflow
This problem requires competitors to be able to pass all the data validation checks to get to the vulnerable
update function. If then requires them to reason about associated with scommon issues tring manipulation functions and issues associated with unbounded copies to data on the heap.
Curated by Lunge Technology, LLC. Questions or comments? Send us email