Note: This is a public test instance of Red Hat Bugzilla. The data contained within is a snapshot of the live data so any changes you make will not be reflected in the production Bugzilla. Email is disabled so feel free to test any aspect of the site that you want. File any problems you find or give feedback at bugzilla.redhat.com.
Bug 1154060 - curl: Disable out-of-protocol fallback to SSL 3.0
Summary: curl: Disable out-of-protocol fallback to SSL 3.0
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: curl
Version: 7.1
Hardware: Unspecified
OS: Unspecified
high
high
Target Milestone: rc
: ---
Assignee: Kamil Dudka
QA Contact: Stefan Kremen
URL:
Whiteboard:
Depends On: 1166567
Blocks: 1154059
TreeView+ depends on / blocked
 
Reported: 2014-10-17 12:28 UTC by Florian Weimer
Modified: 2015-11-19 07:06 UTC (History)
11 users (show)

Fixed In Version: curl-7.29.0-24.el7
Doc Type: Deprecated Functionality
Doc Text:
An out-of-protocol fallback to SSL version 3.0 was available with libcurl. Attackers could abuse the fallback to force downgrade of the SSL version. The fallback has been removed from libcurl. Users requiring this functionality can explicitly enable SSL 3.0 through the libcurl API.
Clone Of: 1154059
: 1166567 (view as bug list)
Environment:
Last Closed: 2015-11-19 07:06:48 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Bugzilla 1152789 0 high CLOSED CVE-2014-3566 SSL/TLS: Padding Oracle On Downgraded Legacy Encryption attack 2021-02-22 00:41:40 UTC
Red Hat Product Errata RHSA-2015:2159 0 normal SHIPPED_LIVE Moderate: curl security, bug fix, and enhancement update 2015-11-19 08:26:18 UTC

Description Florian Weimer 2014-10-17 12:28:07 UTC 
+++ This bug was initially created as a clone of Bug #1154059 +++

We should disable the retry-with-SSL-3.0 behavior in curl because it can be trivially triggered by an on-path attacker to cause a protocol downgrade, and SSL 3.0 has several known weaknesses.  This curl behavior is quite surprising because it is restricted to the NSS backend, and other systems which use the OpenSSL or GNUTLS backend do not share this behavior.

At this stage, it is best to leave SSL 3.0 enabled.  (The in-protocol version negotiation has not been broken, sosome TLS version will be used automatically if supported by the server.)

This might reintroduce bug 525496 and bug 527771, so a system-wide knob to re-enable the SSL 3.0 fallback might be necessary.  Perhaps the existence of a file like /etc/sysconfig/curl/enable-ssl-fallback could re-enable the old behavior.
Comment 2 Kamil Dudka 2014-10-29 14:26:08 UTC 
The code in question has been removed from upstream libcurl:

https://github.com/bagder/curl/compare/07048941a4...276741af4d
Comment 30 errata-xmlrpc 2015-11-19 07:06:48 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHSA-2015-2159.html
Note You need to log in before you can comment on or make changes to this bug.