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Date: Sun, 13 Apr 2014 21:12:19 -0400
From: Peter Malone <peter@...ermalone.org>
To: fulldisclosure@...lists.org
Subject: Re: [FD] Two Possible Vulnerabilities in courier-imapd?
Correction, the second one isn't a format string vulnerability at all.
Don't know what I was thinking there - my bad.
On Sun, 2014-04-13 at 20:00 -0400, Peter Malone wrote:
> Hi there,
>
> Lets take a look at two functions in courier-imap 4.15. The first one is
> emptytrash(), and the second one is store_mailbox().
>
>
> void emptytrash()
> {
> char *dir, *all_settings, *next_folder, *folder, *p;
> unsigned l;
>
> all_settings=getenv("IMAP_EMPTYTRASH");
> return;
>
> all_settings=strdup(all_settings);
> if (!all_settings)
> return;
>
> if (strchr(all_settings, ':') == 0 &&
> strchr(all_settings, ',') == 0)
> {
> l=atoi(all_settings);
>
> if (l <= 0)
> l=1;
>
> maildir_getnew(".", trash, NULL, NULL);
> if ((dir=maildir_folderdir(".", trash)))
> {
> maildir_purge(dir, l * 24 * 60 * 60);
> free(dir);
> }
> free(all_settings);
> return;
> }
>
> for (folder=all_settings; folder && *folder; )
> {
> if (*folder == ',')
> {
> ++folder;
> continue;
> }
> next_folder=strchr(folder, ',');
> if (next_folder)
> *next_folder++=0;
>
> p=strchr(folder, ':');
> if (!p)
> {
> folder=next_folder;
> continue;
> }
>
> *p++=0;
>
> l=atoi(p);
> if (l <= 0) l=1;
>
> maildir_getnew(".", folder, NULL, NULL);
> if ((dir=maildir_folderdir(".", folder)))
> {
> maildir_purge(dir, l * 24 * 60 * 60);
> free(dir);
> }
> folder=next_folder;
> }
> free(all_settings);
> }
>
> The interesting parts of this function are
> all_settings=getenv("IMAP_EMPTYTRASH");
> free(all_settings);
>
> Setting IMAP_EMPTYTRASH to something like "%s:%d%d%d%s%s%s" should cause
> the application to crash.
>
> Moving on to store_mailbox()... this function is too big to paste in
> this mail, but if we focus on lines 744 - 757:
> if (fflush(fp) || ferror(fp))
> {
> fprintf(stderr,
> "ERR: error storing a message, user=%s, errno=%d
> \n",
> getenv("AUTHENTICATED"), errno);
>
> fclose(fp);
> unlink(tmpname);
> writes(tag);
> writes(nowrite);
> free(tmpname);
> free(newname);
> return (-1);
> }
>
> I believe the above fprintf call is a format string vulnerability.
>
> I'm going to continue to look into this, however in the meantime I
> welcome your input regarding these two functions.
>
> Regards,
> Peter.
>
>
> _______________________________________________
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> http://nmap.org/mailman/listinfo/fulldisclosure
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