[squid-announce] [ADVISORY] SQUID-2020:4 Multiple issues in HTTP Digest authentication

[Amos Jeffries]

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    Squid Proxy Cache Security Update Advisory SQUID-2020:4
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Advisory ID:        SQUID-2020:4
Date:               April 23, 2020
Summary:            Multiple issues
                    in HTTP Digest authentication.
Affected versions:  Squid 2.x -> 2.7.STABLE9
                    Squid 3.x -> 3.5.28
                    Squid 4.x -> 4.10
                    Squid 5.x -> 5.0.1
Fixed in version:   Squid 4.11 and 5.0.2
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    http://www.squid-cache.org/Advisories/SQUID-2020_4.txt
    http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-11945
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Problem Description:

 Due to an integer overflow bug Squid is vulnerable to credential
 replay and remote code execution attacks against HTTP Digest
 Authentication tokens.

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Severity:

 When memory pooling is used this problem allows a remote client
 to replay a sniffed Digest Authentication nonce to gain access
 to resources that are otherwise forbidden.

 When memory pooling is disabled this problem allows a remote
 client to perform remote code execution through the free'd nonce
 credentials.

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Updated Packages:

 This bug is fixed by Squid versions 4.11 and 5.0.2.

 In addition, patches addressing this problem for the stable
 releases can be found in our patch archives:

Squid 4:
 <http://www.squid-cache.org/Versions/v4/changesets/squid-4-eeebf0f37a72a2de08348e85ae34b02c34e9a811.patch>

 If you are using a prepackaged version of Squid then please refer
 to the package vendor for availability information on updated
 packages.

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Determining if your version is vulnerable:

 All Squid-2.x up to and including 2.4.STABLE7 are not vulnerable.

 All Squid-2.5 up to and including 2.7.STABLE9 are vulnerable.

 All Squid-2.x up to and including 2.7.STABLE9 configured with
 "auth_param digest" are vulnerable.

 All Squid-2.x up to and including 2.7.STABLE9 configured without
 "auth_param digest" are not vulnerable.

 All Squid-3.x up to and including 3.5.28 built with
 --disable-auth are not vulnerable.

 All Squid-3.2 up to and including 3.5.28 built with
 --disable-auth-digest are not vulnerable.

 All Squid-3.x up to and including 3.5.28 configured with
 "auth_param digest" are vulnerable.

 All Squid-3.x up to and including 3.5.28 configured without
 "auth_param digest" are not vulnerable.

 All Squid-4.x up to and including 4.10 built with
 --disable-auth are not vulnerable.

 All Squid-4.x up to and including 4.10 built with
 --disable-auth-digest are not vulnerable.

 All Squid-4.x up to and including 4.10 configured with
 "auth_param digest" are vulnerable.

 All Squid-4.x up to and including 4.10 configured without
 "auth_param digest" are not vulnerable.

 Squid-5.0.1 built with --disable-auth-digest is not vulnerable.

 Squid-5.0.1 configured with "auth_param digest" are vulnerable.

 Squid-5.0.1 configured without "auth_param digest" are not
 vulnerable.

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Workaround:

Either,

 Remove all "auth_param digest" lines from squid.conf

Or,

 Build Squid with --disable-auth-digest

Or,

 Build Squid with --disable-auth

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Contact details for the Squid project:

 For installation / upgrade support on binary packaged versions
 of Squid: Your first point of contact should be your binary
 package vendor.

 If your install and build Squid from the original Squid sources
 then the squid-users at lists.squid-cache.org mailing list is your
 primary support point. For subscription details see
 <http://www.squid-cache.org/Support/mailing-lists.html>.

 For reporting of non-security bugs in the latest STABLE release
 the squid bugzilla database should be used
 <http://bugs.squid-cache.org/>.

 For reporting of security sensitive bugs send an email to the
 squid-bugs at lists.squid-cache.org mailing list. It's a closed
 list (though anyone can post) and security related bug reports
 are treated in confidence until the impact has been established.

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Credits:

 This vulnerability was discovered by Clément Berthaux and
 Florian Guilbert of Synacktiv.

 Fixed by Maxime Desbrus of Synacktiv.

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Revision history:

 2019-11-20 13:39:07 UTC Initial Report
 2020-04-02 11:16:45 UTC Patches Released
 2020-04-20 20:08:14 UTC CVE Assignment
 2020-04-23 08:00:00 UTC Advisory Released
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END