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Fix LDAP key data segmentation [CVE-2014-4345]
For principal entries having keys with multiple kvnos (due to use of -keepold), the LDAP KDB module makes an attempt to store all the keys having the same kvno into a single krbPrincipalKey attribute value. There is a fencepost error in the loop, causing currkvno to be set to the just-processed value instead of the next kvno. As a result, the second and all following groups of multiple keys by kvno are each stored in two krbPrincipalKey attribute values. Fix the loop to use the correct kvno value. CVE-2014-4345: In MIT krb5, when kadmind is configured to use LDAP for the KDC database, an authenticated remote attacker can cause it to perform an out-of-bounds write (buffer overrun) by performing multiple cpw -keepold operations. An off-by-one error while copying key information to the new database entry results in keys sharing a common kvno being written to different array buckets, in an array whose size is determined by the number of kvnos present. After sufficient iterations, the extra writes extend past the end of the (NULL-terminated) array. The NULL terminator is always written after the end of the loop, so no out-of-bounds data is read, it is only written. Historically, it has been possible to convert an out-of-bounds write into remote code execution in some cases, though the necessary exploits must be tailored to the individual application and are usually quite complicated. Depending on the allocated length of the array, an out-of-bounds write may also cause a segmentation fault and/or application crash. CVSSv2 Vector: AV:N/AC:M/Au:S/C:C/I:C/A:C/E:POC/RL:OF/RC:C [email@example.com: clarified commit message] [firstname.lastname@example.org: CVE summary, CVSSv2 vector] (cherry picked from commit 81c332e) ticket: 7980 version_fixed: 1.12.2 status: resolved
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