Bug 1446288 (CVE-2017-7482) - CVE-2017-7482 kernel: net/rxrpc: overflow in decoding of krb5 principal
Summary: CVE-2017-7482 kernel: net/rxrpc: overflow in decoding of krb5 principal
Keywords:
Status: CLOSED ERRATA
Alias: CVE-2017-7482
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 1451579 1451580 1451581 1451582 1451583 1451584 1451585 1464888 1466125 1466126 1466127
Blocks: 1446290
TreeView+ depends on / blocked
 
Reported: 2017-04-27 15:18 UTC by Andrej Nemec
Modified: 2021-02-17 02:12 UTC (History)
35 users (show)

Fixed In Version: kernel 4.12
Doc Type: If docs needed, set a value
Doc Text:
Keberos 5 tickets being decoded when using the RXRPC keys incorrectly assumes the size of a field. This could lead to the size-remaining variable wrapping and the data pointer going over the end of the buffer. This could possibly lead to memory corruption and possible privilege escalation.
Clone Of:
Environment:
Last Closed: 2019-06-08 03:11:37 UTC
Embargoed:

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System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2019:0641 0 None None None 2019-03-26 07:45:14 UTC

Description Andrej Nemec 2017-04-27 15:18:07 UTC 
When a kerberos 5 ticket is being decoded so that it can be loaded into an rxrpc-type key, the length of a variable-length field is checked to make sure that it's not going to overrun the allocated buffer space.

The data is padded to the nearest four-byte boundary and the code doesn't check for this extra four-byte aligned padding.  This can lead to the size-remaining variable wrapping and the data pointer accessing or reading past the end of the buffer.  The read functionality could allow for a 3 byte infoleak and the write flaw could allow for an uncontrolled 3 byte write to kernels slab memory.  This could lead to memory corruption and possible privilege escalation although no known exploit exists at the time of writing.

Discussion an a CVE-ID assignment:

http://seclists.org/oss-sec/2017/q2/602

Upstream fix
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=5f2f97656ada8d811d3c1bef503ced266fcd53a0
Comment 1 Andrej Nemec 2017-04-27 15:24:24 UTC 
Acknowledgments:

Name: Shi Lei (Qihoo 360 Gear Team)
Comment 3 Wade Mealing 2017-05-19 03:26:10 UTC 
Statement:

This issue does not affect the Linux kernel packages as shipped with Red Hat Enterprise Linux 5,6 and 7 as the module is not enabled on these systems.

This issue affects the Linux kernel packages as shipped with Red Hat Enterprise MRG-2.  Future Linux kernel updates for the respective releases may address this issue.
Comment 6 Wade Mealing 2017-06-26 08:06:23 UTC 
Created kernel tracking bugs for this issue:

Affects: fedora-all [bug 1464888]
Comment 8 Evgenii Shatokhin 2017-06-29 12:12:54 UTC 
As far as I can see in the kernel sources for the version 3.10.0-514.26.1 in RHEL 7, the affected code (from net/rxrpc/ar-key.c) is only built when CONFIG_AF_RXRPC is set. However, that kernel and at least some earlier ones have "# CONFIG_AF_RXRPC is not set" in their config files.

So RHEL 7 is actually not affected by this issue, right? Or, perhaps, I am missing something.
Comment 9 Wade Mealing 2017-07-04 01:13:48 UTC 
You're 100% right, I had originally grepped the config for CONFIG_RX_RPC not CONFIG_AF_RX_RPC.  Kernel-rt/MRG-2 still seems to use this as a module it remains affected.

Closing trackers for 6 and 7 adjusting statement.
Comment 10 Justin M. Forbes 2018-01-29 17:17:40 UTC 
This was fixed for Fedora with 4.11.8 stable updates
Comment 11 errata-xmlrpc 2019-03-26 07:45:12 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise MRG 2

Via RHSA-2019:0641 https://access.redhat.com/errata/RHSA-2019:0641
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