Memory unauthorized access issues in byte2search in Cyrus IMAP

[Egoitz Aurrekoetxea]

Good morning,


I have been checking the Cyrus IMAP 2.3.19 and 2.3.18 code because I 
have observed some issues in UID SORT commands in the IMAP protocol. 
When performing a command

like ". UID SORT (SIZE) US-ASCII ALL TEXT avanzada" in a mailbox where 
matches were found caused you to obtain in a debug (or non debug I 
think) log the following entry :

Oct 31 09:17:21 hostname master[78064]: process 78268 exited, signaled 
to death by 11

Lines like this are seen when a process has been signaled by the kernel 
with signal 11. Have been reading this signal is sent to a proccess when 
it performs an unauthorized memory

access attemp (an out of the own variable, pointer... etc, storage 
room). After debugging the code with GDB and doing several checks, have 
seen the issue came from the byte2search()

function when a piece of the string s->substr was trying to be stored in 
b. Concretely the third if in the loop :


     for (i = 0, cur = 0; i < s->max_start; i++) {
     /* no more active offsets */
     if (s->starts[i] == -1)
         break;

     /* if we've passed one that's not ongoing, copy back */
     if (cur < i) {
         s->starts[cur] = s->starts[i];
     }
     /* check that the substring is still maching */
     if (b == s->substr[s->offset - s->starts[i]]) {


The issue was caused there because s->starts[i] in this place, was not 
being able to be accesed because it was pointing to to data outside 
s->starts. After searching where this array was being initialized

and it's memory allocated (which was in search_init function), I tried 
to allocate 10 bytes more for that pointer. After doing it, there were 
no more issues. So I tried allocating just one byte more which it seemed

to be enough too (at least for the patterns I have searched for). At 
this moment I understood this pointer (s->starts which was a 
search_state->substr pointer inside the search_state structure) was not 
having

enough room for all the content needed to be stored, or at least accesed 
when calling it. I checked then the code of Cyrus 2.3.18 and 2.3.19 but 
didn't see any kind of differences in the part of the memory

allocation (in search_init()) or usage (in bytesearch) for s->starts. I 
deciced to check Cyrus 2.4 code and I saw it's room was being allocated 
the following way :


     s->starts = xmalloc(s->max_start * sizeof(size_t));


instead of that in 2.3 was done :


     s->starts = xmalloc(s->max_start * sizeof(int));


So I understood s->starts should be allocated to the size of a size_t 
type defined variable size, instead to the size of an integer variable n 
times. After replacing it, has seen definitively all seemed to be

working. So wouldn't Cyrus 2.3 sources have this allocation in 
search_init done with sizeof(size_t) instead of the sizeof(int)?. I 
think this is important because else, when the first character of a

pattern is repeated more than one time, the pattern has a would say 
patlen of 8-9 bytes and matches exist in the mailbox, that search would 
end up with a proccess died due to a signal 11.


My env is FreeBSD RELENG_9_0 OS with a Cyrus 2.3.18_1 port. Am I wrong, 
shouldn't that allocation be changed?.


Thanks a lot for your time,

Best regards,


-- 


sarenet
*Egoitz Aurrekoetxea*
Departamento de sistemas
944 209 470
Parque Tecnológico. Edificio 103
48170 Zamudio (Bizkaia)
egoitz at sarenet.es <mailto:egoitz at sarenet.es>
www.sarenet.es <http://www.sarenet.es>

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