Bug 1286977 - proftpd: unbounded SFTP extended attribute key/values
proftpd: unbounded SFTP extended attribute key/values
Status: NEW
Product: Security Response
Classification: Other
Component: vulnerability (Show other bugs)
unspecified
All Linux
medium Severity medium
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Assigned To: Red Hat Product Security
impact=moderate,public=20151129,repor...
: Security
Depends On: 1286978 1286979
Blocks:
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Reported: 2015-12-01 04:34 EST by Martin Prpič
Modified: 2015-12-18 02:25 EST (History)
4 users (show)

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Doc Type: Bug Fix
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Description Martin Prpič 2015-12-01 04:34:21 EST
The following flaw was found in proftpd:

Part of the SFTP handshake involves "extensions", which are key/value pairs, comprised of strings. In SSH, strings are encoded for network transport as a 32-bit length, followed by the bytes.

The mod_sftp module currently places no bounds/length limitations when reading these SFTP extension key/value data from the network. A malicious attacker might attempt to encode large values, and allocate more memory than is necessary.

To avoid undue resource exhaustion by a remote client, mod_sftp should place a limit on the maximum length of acceptable extension keys/values.

Upstream bug:

http://bugs.proftpd.org/show_bug.cgi?id=4210

Upstream patch:

https://github.com/proftpd/proftpd/pull/171
Comment 1 Martin Prpič 2015-12-01 04:34:48 EST
Created proftpd tracking bugs for this issue:

Affects: fedora-all [bug 1286978]
Affects: epel-all [bug 1286979]
Comment 2 Paul Howarth 2015-12-01 09:27:05 EST
Is it worth waiting for a CVE number for this issue to put in the package changelog before pushing an update?
Comment 3 Martin Prpič 2015-12-01 09:29:47 EST
(In reply to Paul Howarth from comment #2)
> Is it worth waiting for a CVE number for this issue to put in the package
> changelog before pushing an update?

Definitely not, I'd go ahead and push the update referencing this BZ.
Comment 4 Fedora Update System 2015-12-11 18:53:02 EST
proftpd-1.3.5a-5.fc23 has been pushed to the Fedora 23 stable repository. If problems still persist, please make note of it in this bug report.
Comment 5 Fedora Update System 2015-12-11 20:54:06 EST
proftpd-1.3.5a-5.fc22 has been pushed to the Fedora 22 stable repository. If problems still persist, please make note of it in this bug report.
Comment 6 Fedora Update System 2015-12-18 02:25:28 EST
proftpd-1.3.5a-2.el7 has been pushed to the Fedora EPEL 7 stable repository. If problems still persist, please make note of it in this bug report.

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