Hi Chris,
---------------------OUTLINE----------------------------------
1, Problem statement
In reviewing the messages around the threats to the syslog protocol, it
appears that the priority of threats is as follows:
Primary:
Modification
Disclosure
Masquerading
Secondary:
Message stream modification
Not highly considered:
DoS
Traffic Analysis
Disclosure has been controversial in the discussions. It has been noted
that syslog messages are freeform text and the possibility of sending
sensitive information will always exist. This is all the more true if high
levels of debugging are enabled.
Note: This section will summary the security threats to SYSLOG discussed on
mailing list.
2, Introduction to TLS
2.1 How TLS works
TLS establishes a private end-to-end connection, optionally including strong
mutual authentication, using a variety of cryptosystems. Initially, a
handshake phase uses three subprotocols to set up a record layer,
authenticate endpoints, set parameters, as well as report errors. Then,
there is an ongoing layered record protocol that handles encryption,
compression, and reassembly for the remainder of the connection. Application
data protocol, such as SYSLOG, works as a client of record protocol.
2.2 Security Property
TLS security properties: Integrity verification (by Hash MAC with MD5 and
SHA1), Data origin authentication (by Certificate/signature along with hash
MAC), Confidentiality/Privacy (by encryption/decryption with DES, AES, RC2
etc), Anti-replay (by sequence number with integrity verification).
3, TLS to mitigate SYSLOG security threats
Integrity verification to counter modification
Data origin authentication to counter masquerading
Confidentiality/Privacy to counter disclosure
Anti-replay to counter message stream modification
4, Framework
4.1 Roles
SYSLOG sender works as TLS client and receiver as TLS server.
Note: It is possible to reverse the role, i.e. sender is TLS server. But it
looks odd and there is no obvious benefit observed right now.
Syslog relay can be either TLS client or server.
4.2 Protocol Port
A port number should be allocated.
5, Protocol Elements
5.1 Initiation
The Sender should initiate a connection to the Receiver on the appropriate
port and then send the TLS ClientHello to begin the TLS handshake. When the
TLS handshake has finished the Sender may then initiate the first SYSLOG
message.
Note: We need to define how syslog interpret the authentication certificates
exchanged by handshake protocol.
Note: We need to discuss what authentication we need: client authenticated
to server, server authenticated to client, or both (mutual authentication)
5.2 Sending data
All SYSLOG message MUST be sent as TLS "application data".
We need to discuss:
5.2.1, Multiple SYSLOG messages in one TLS message or one SYSLOG message in
one TLS message? How to parse TLS message into several SYSLOG messages in
the multiplexing mode?
5.2.2, Does SYSLOG message truncation will affect the transport?
5.3 Closure
Sender MUST send a closure alert before closing the connection. Sender which
are unprepared to receive any more data MAY choose not to wait for the
Receiver 's closure alert and simply close the connection, thus generating
an incomplete close on the Receiver side. Receiver MUST attempt to initiate
an exchange of closure alerts with the Sender before closing the connection.
Receiver MAY close the connection after sending the closure alert, thus
generating an incomplete close on the Sender side.
5.4 Relay
5.4.1 It seems expensive to a SYSLOG Relay to become TLS client or server.
Is it possible to relay SYSLOG message without TLS processing?
5.4.2 There are hostname or IP in SYSLOG message header. A implementation
should not check the hostname/IP against TLS certificate because of relay.
6 Security Consideration
6.1 Coexist of TLS and SYSLOG-SIGN
TLS and SYSLOG-SIGN address quite different security requirements. Data
origin authentication of TLS checks whether the data is received from the
SENDER (device or relay), but the SYSLOG-SIGN check whether the data
originates from a specific DEVICE.
The syslog-sign certificate and tls client certificate are not exchangeable
because a sender may be a relay. Another reason is sender may have several
certificates for different purpose.
6.2 Mutual Authentication?
-----Original Message-----
From: Chris Lonvick [mailto:[EMAIL PROTECTED]
Sent: Sunday, February 12, 2006 5:14 AM
To: Miao Fuyou
Cc: [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL PROTECTED]
Subject: RE: [Syslog] Coming to consensus on syslog threats
Hi Miao and Yuzhi,
As Tom Petch pointed out we do need to establish that a TLS transport will
address the threats we have described. Would you briefly outline how you
propose to utilize TLS to address Modification, Disclosure, Masquerading?
(Others can jump in here with more comments and concerns so the document
can get a good start.) Once we establish that I believe we can accept
your offer to write the document.
Many thanks,
Chris
On Wed, 8 Feb 2006, Miao Fuyou wrote:
>
> I and Yuzhi would like to edit a draft on syslog tls transport. We
> will get the draft posted ASAP.
>
> Miao
> [EMAIL PROTECTED]
>
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED]
> On Behalf Of Chris Lonvick
> Sent: Tuesday, February 07, 2006 10:10 PM
> To: [EMAIL PROTECTED]
> Subject: [Syslog] Coming to consensus on syslog threats
>
>
> Hi,
>
> In reviewing the messages around the threats to the syslog protocol,
> it appears that the priority of threats is as follows:
>
> Primary:
> Modification
> Disclosure
> Masquerading
>
> Secondary:
> Message stream modification
>
> Not highly considered:
> DoS
> Traffic Analysis
>
>
> Disclosure has been controversial in the discussions. It has been
> noted that syslog messages are freeform text and the possibility of
> sending sensitive information will always exist. This is all the more
> true if high levels of debugging are enabled.
>
> Also from the list, it appears that the use of TLS is supported and
> will address these threats. I will ask for volunteers to write
> syslog-protocol-tls and get it through the process.
>
> It looks like syslog-protocol and syslog-transport-udp are very close
> to being finished. I'd like to wrap those up and fully concentrate on
> syslog-transport-tls, syslog-sign, and syslog-device-mib.
> syslog-transport-tls will have to go through the process at the same
> time as syslog-protocol and syslog-transport-udp. I'll ask Rainer and
> Anton to please be patient while we complete this final document.
>
>
> With that, I'll propose the following Charter revision and Milestones.
>
> ---vvv---
>
> Syslog is a de-facto standard for logging system events. However, the
> protocol component of this event logging system has not been formally
> documented. While the protocol has been very useful and scalable, it
> has some known security problems which were documented in the
> INFORMATIONAL RFC 3164.
>
> The goal of this working group is to address the security and
> integrity problems, and to standardize the syslog protocol, transport,
> and a select set of mechanisms in a manner that considers the ease of
> migration between and the co-existence of existing versions and the
> standard.
>
> Reviews have shown that there are very few similarities between the
> message formats generated by heterogeneous systems. In fact, the only
> consistent commonality between messages is that all of them contain
> the <PRI> at the start. Additional testing has shown that as long as
> the <PRI> is present in a syslog message, all tested receivers will
> accept any generated message as a valid syslog message. In designing
> a standard syslog message format, this Working Group will retain the
> <PRI> at the start of the message and will introduce protocol
> versioning. Along these same lines, many different charsets have been
> used in syslog messages observed in the wild but no indication of the
> charset has been given in any message. The Working Group also feels
> that multiple charsets will not be beneficial to the community; much
> code would be needed to distinguish and interpret different charsets.
> For compatibility with existing implementations, the Working Group
> will allow that messages may still be sent that do not indicate the
> charset used. However, the Working Group will recommend that messages
> contain a way to identify the charset used for the message, and will
> also recommend a single default charset.
>
> syslog has traditionally been transported over UDP and this WG has
> already defined RFC 3195 for the reliable transport for the syslog
> messages. The WG will separate the UDP transport from the protocol so
> that others may define additional transports in the future.
>
> The threats that this WG will primarily address are modification,
> disclosure, and masquerading. A secondary threat is message stream
> modification. Threats that will not be addressed by this WG are DoS
> and traffic analysis. The primary attacks may be thwarted by a secure
> transport. However, it must be remembered that a great deal of the
> success of syslog has been attributed to its ease of implementation
> and relatively low maintenance level. The Working Group will consider
> those factors, as well as current implementations, when deciding upon
> a secure transport. The secondary threat of message stream
> modification can be addressed by a mechanism that will verify the
> end-to-end integrity and sequence of messages. The Working Group
> feels that these aspects may be addressed by a dissociated signature
> upon sent messages.
>
>
>
> - A document will be produced that describes a standardized syslog
> protocol. A mechanism will also be defined in this document that will
> provide a means to convey structured data.
>
> - A document will be produced that describes a standardized UDP
> transport for syslog.
>
> - A document will be produced that requires a secure transport for the
> delivery of syslog messages.
>
> - A document will be produced to describe the MIB for syslog entities.
>
> - A document will be produced that describes a standardized mechanism
> to sign syslog messages to provide integrity checking and source
> authentication.
>
>
> Milestones:
>
> Nov 2006 Submit Syslog Protocol to the IESG for consideration as a
> PROPOSED STANDARD.
> Nov 2006 Submit Syslog UDP Transport Mapping to the IESG for
> consideration as a PROPOSED STANDARD.
> Nov 2006 Submit Syslog TLS Transport Mapping to the IESG for
> consideration as a PROPOSED STANDARD.
> Nov 2006 Submit Syslog Device MIB to IESG for consideration as a
> PROPOSED STANDARD.
> Nov 2006 Submit a document that defines a message signing and
> ordering mechanism to the IESG for consideration as a
> PROPOSED STANDARD
>
>
> ---^^^---
>
> Thanks,
> Chris
>
> _______________________________________________
> Syslog mailing list
> [email protected] https://www1.ietf.org/mailman/listinfo/syslog
>
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