[TLS] Draft-22 and Post-Handshake Authentication

"Short, Todd" <tshort@akamai.com> Tue, 02 January 2018 17:07 UTC

From: "Short, Todd" <tshort@akamai.com>
To: "<tls@ietf.org>" <tls@ietf.org>
Thread-Topic: Draft-22 and Post-Handshake Authentication
Thread-Index: AQHTg+wZTzn40m8IekqCxE+bMFdDSw==
Date: Tue, 02 Jan 2018 17:06:59 +0000
Message-ID: <401F3672-AF80-464B-9348-D91196E85E54@akamai.com>
Accept-Language: en-US
Content-Language: en-US
x-ms-exchange-messagesentrepresentingtype: 1
x-ms-exchange-transport-fromentityheader: Hosted
x-originating-ip: [172.19.44.203]
Content-Type: multipart/alternative; boundary="_000_401F3672AF80464B9348D91196E85E54akamaicom_"
MIME-Version: 1.0
X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:, , definitions=2018-01-02_13:, , signatures=0
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1711220000 definitions=main-1801020246
X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:, , definitions=2018-01-02_13:, , signatures=0
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1711220000 definitions=main-1801020247
Archived-At: <https://mailarchive.ietf.org/arch/msg/tls/rdnHoRsHCMfqPU5bd2czNgPXcfs>
Subject: [TLS] Draft-22 and Post-Handshake Authentication
X-BeenThere: tls@ietf.org
X-Mailman-Version: 2.1.22
Precedence: list
List-Id: "This is the mailing list for the Transport Layer Security working group of the IETF." <tls.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/tls>, <mailto:tls-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/tls/>
List-Post: <mailto:tls@ietf.org>
List-Help: <mailto:tls-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/tls>, <mailto:tls-request@ietf.org?subject=subscribe>
X-List-Received-Date: Tue, 02 Jan 2018 17:07:06 -0000

Question on Post-Handshake Authentication (PHA):

PHA can occur multiple times over a connection. The description for the "Handshake Context” is as follows (4.4):


   |           |                            |                          |
   | Post-     | ClientHello ... client     | client_application_traff |
   | Handshake | Finished +                 | ic_secret_N              |
   |           | CertificateRequest         |                          |
   +-----------+----------------------------+--------------------------+

Now, PHA costs of:

S>C: CertificateRequest

followed by:

C>S: Certificate+CertificateVerify+client Finished

This could be interpreted to mean that these PHA messages are included in the Handshake Context. However, Section 4.4.1 states:


   For concreteness, the transcript hash is always taken from the
   following sequence of handshake messages, starting at the first
   ClientHello and including only those messages that were sent:
   ClientHello, HelloRetryRequest, ClientHello, ServerHello,
   EncryptedExtensions, server CertificateRequest, server Certificate,


   server CertificateVerify, server Finished, EndOfEarlyData, client
   Certificate, client CertificateVerify, client Finished.


I want to confirm that the PHA handshake context consists only of the messages listed in section 4.4.1 from the initial handshake, and do not include any of the messages from intermediate PHA exchanges.

Thank you,

--
-Todd Short
// tshort@akamai.com<mailto:tshort@akamai.com>
// "One if by land, two if by sea, three if by the Internet."

[TLS] Draft-22 and Post-Handshake Authentication Short, Todd
Re: [TLS] Draft-22 and Post-Handshake Authenticat… Eric Rescorla