SSE BOF R. Moskowitz
Internet-Draft HTT Consulting
Intended status: Standards Track I. Faynberg
Expires: December 29, 2017 Stargazers Consulting, LLC
H. Lu
Retired
S. Hares
Hickory Hill Consulting
P. Giacomin
FreeLance
June 27, 2017
Session Security Envelope
draft-moskowitz-sse-05
Abstract
This memo specifies the details of the Session Security Envelope
(SSE). SSE is a session protocol aiming to guarantee
confidentiality, integrity and authentication completely
independently by the underlying context, namely network and transport
layers. A single session using the SEE protocol can include a single
transport session or multiple transport sessions. This mean that SSE
can survive the break-down in network and transport layers or to
attacks carried against them. SSE is also applicable in networks
lacking in classic inter-networking and transport protocols SSE
relies on modern AEAD block cipher modes of operations, a class of
block cipher modes which allows, at the same time, to authenticate
the message while encrypting a part of it.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 29, 2017.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terms and Definitions . . . . . . . . . . . . . . . . . . . . 3
2.1. Requirements Terminology . . . . . . . . . . . . . . . . 3
2.2. Notations . . . . . . . . . . . . . . . . . . . . . . . . 3
2.3. Definitions . . . . . . . . . . . . . . . . . . . . . . . 3
3. SSE Security Boundary . . . . . . . . . . . . . . . . . . . . 3
4. API . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
5. Packet format . . . . . . . . . . . . . . . . . . . . . . . . 5
5.1. SSE compact format . . . . . . . . . . . . . . . . . . . 5
5.2. SSE Large Format . . . . . . . . . . . . . . . . . . . . 6
5.3. SSE Extreme Format . . . . . . . . . . . . . . . . . . . 7
5.4. Header Fields . . . . . . . . . . . . . . . . . . . . . . 8
5.5. AEAD integration . . . . . . . . . . . . . . . . . . . . 9
6. Packet processing and State Machine . . . . . . . . . . . . . 9
6.1. Establishing a session . . . . . . . . . . . . . . . . . 9
6.2. Processing Outgoing Application Data . . . . . . . . . . 9
6.3. Processing Incoming Application Data . . . . . . . . . . 9
7. Negotiating SSE . . . . . . . . . . . . . . . . . . . . . . . 10
7.1. Using IKEv2 . . . . . . . . . . . . . . . . . . . . . . . 10
7.2. Using HIP . . . . . . . . . . . . . . . . . . . . . . . . 10
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
9. Security Considerations . . . . . . . . . . . . . . . . . . . 10
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
10.1. Normative References . . . . . . . . . . . . . . . . . . 11
10.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
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1. Introduction
This memo specifies the details of the Session Security Envelope
(SSE). SSE is a session protocol aiming to guarantee
confidentiality, integrity and authentication completely
independently by the underlying context, namely network and transport
layers. A single SSE session can span a single transport session or
multiple transport sessions. These transport sessions can use the
same transport layer protocol (E.g. TCP) or use different transport
protocols. SSE can survive the break-down in network and transport
layers or to attacks carried against them. Moreover SSE will relies
on modern AEAD block cipher modes of operations, a class of block
cipher modes which allows, at the same time, to authenticate the
message while encrypting a part of it.
2. Terms and Definitions
2.1. Requirements Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. .
2.2. Notations
This section will contain notations
2.3. Definitions
AEAD Block Cypher: (definition needed)
SSE: Session Specific Envelope
3. SSE Security Boundary
The security boundary comes at layer above the IP transport layers
(TCP, SCTP, UDP). This security allows the data to be secure prior
to entering into a specific transport layer. A single SSE session
can span 1 or N transport protocol connections. The multiple
transport connections running under an SSE session may all use one
protocol (e.g. TCP) or multiple protocols (e.g. TCP, SCTP, UDP).
The higher layer security boundary provides a common security layer.
4. API
The initial API is part of a shim with socket call over a TCP socket.
s = int socket(int domain, int type, int protocol)
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where:
domain: AF_INET and AF_INET6 supported
type: SOCK_SECURE
protocol: Transport protocol (TCP (6), UDP (6), SCTP (132))
int setsockopt(int sockfd, int level, int optname,
const void *optval, socklen_t optlen);
int getsocketopt(int sockfd, int level, int optname
const void *optval, socket
where:
sockfd: # socket file descriptor
optname: # option name (see below)
optval; # points to *sse_transport structure;
optlen; # length of option
optval values:
ADD_SSE_Transport[1]; # add transport to SSE
DELETE_SSE_Transport[2]; # delete transport to SSE
Query_SSE_Transport [3]; # Query transport
optval *sse_transport[MAX_SSE_TRANSPORTS]; - for add/deletes
struct *sse_add_transport
int nt_sockfd; # new transport socket
int protocol; # new protocol
);
int getsockopt(int sockfd, int level, int optname,
void *optval, socklen_t *optlen);
int setsockopt(int sockfd, int level, int optname,
const void *optval, socklen_t optlen);
Figure 1 - Example SSE Socket API
Note: The prototype for this SECURE_SOCKET is on a FREEBSD OS.
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5. Packet format
An SSE PDU is a Session Layer PDU (SPDU). In order to accommodate
various use cases three formats are available for the PDU. The only
difference between those formats is the size of length and sequence
number fields. Following these fields is the encrypted payload and
Integrity Check Value (ICV). Encrypted payload and ICV has a
substructure depending on the choice of encryption algorithm and
mode.
5.1. SSE compact format
SSE compact format aims to provide a Session Security Layer to
applications leveraging on constrained network media with packet size
limitations or high cost per bit transport.
In the SSE compact format:
SPI is 24 bits.
FLAGS is 8 bits.
Length is 12 bits
Sequence Number is 20 bits
12 bits of Length allows (2^12) 4096 bytes in the Encrypted Payload
(does not include the ICV). 20 bits in the Sequence Number allows to
send (2^20) 1048576 packets before renegotiating the key. (The ICV
length is set by the KMP parameters, so the length is known and
therefore is not included in the length calculation)
The SPI internally is 32 bits to maintain SPI length consistancy.
The high order 8 bits are always ZERO, allowing for only sending the
lower 24 bits in the header.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SPI | FLAGS |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Encrypted Payload and ICV (Variable) |
~ ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2 - Compact format
5.2. SSE Large Format
SSE large format aims provide a Session Security Layer to
applications which have common sizes of transport packets.
In the SSE compact format:
SPI is 32 bits.
FLAGS is 8 bits.
Length is 32 bits
Sequence Number is 32 bits
32 bits of Length allows (2^32)or ~4Gbytes in the Encrypted Payload
(does not include the ICV). 32 bits in the Sequence Number allows to
send (2^32) ~40 billion packets packets before renegotiating the key.
The 32 bits of length allows an IPv6 jumbogram to be included as in
the SSE Large Format Payload
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SPI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESERVED | FLAGS |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Encrypted Payload and ICV (Variable) |
~ ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3 - Large Format
5.3. SSE Extreme Format
SSE large format aims provide a Session Security Layer to high
performance networks.
In the SSE compact format:
SPI is 32 bits.
FLAGS is 8 bits.
Length is 32 bits
Sequence Number is 64 bits
32 bits of Length allows (2^32) 4294967296 bytes (4Gbytes) in the
Encrypted Payload (excluding the ICV). 32 bits in the Sequence Number
allows to send (2^64) 18446744073709551616 (around 18 * 10^18)
packets before renegotiating the key.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SPI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESERVED | FLAGS |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Encrypted Payload and ICV (Variable) |
~ ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4 - Extreme Format
5.4. Header Fields
SPI is the Security Parameter Index, a 32 bit number received from
the external KMP. It is the index into the Security Association and
is typically unidirectional. That is each direction in has its own
SPI. A KMP for a unicast communication would provide the two SPIs.
Multicast is different. Depending on the requirements, there can be
one SPI for all transmitters or one per transmitter.
The compact format only transmits 24 bits of the 32 bit SPI. The SPI
is internally kept as both the 32 bits SPI from the KMP and a 24 bit
truncated SPI (with the 8 high order bits of zero). If this
truncation results in a duplicate SPI, the negotiation is rejected
and the KMP is called again.
Length is the length in bytes of the encrypted payload. This does
not include the ICV. The length of the ICV depends on the block
cipher settings.
FLAGS is a set of 8 options flags. Bit 7 is the GPComp
[I-D.moskowitz-gpcomp] bit compression option bit.
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| C|
+-+-+-+-+-+-+-+-+
Figure 5 - FLAGS field
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Sequence Number is a, strictly increasing by 1, counter. When the
field cannot be increased without wrapping a key renegotiation MUST
be performed. Please note that this Sequence Number has not the same
meaning and implications of a Transport Layer sequence number, hence
increasing by 1 is a good idea.
Note: It is common practice to rekey some time BEFORE the number
space is exhausted.
5.5. AEAD integration
SSE MUST use AEAD block cipher modes. AEAD block cypher modes will
ensure confidentiality on the payload and integrity of both the
payload and the headers (SPI, length and sequence number).
6. Packet processing and State Machine
SSE will spawn across several ports and protocols, hence each
listened port and protocol can be a different SSE instance. See
Architecture Draft.
6.1. Establishing a session
An application can establish a session via the SSE API, which in turn
will interact with a KMP daemon. SSE instance will get all
parameters related to the session from the KMP daemon.
Editorial note: Is this a local vulnerability?
6.2. Processing Outgoing Application Data
After having established an SSE session, an application can send
application- level data using the normal socket calls. The SSE layer
will encapsulate the packet, and send it on the appropriate transport
session. The application doesn't need to know SPI, sequence number
or key. The local SSE knows these facts, and keeps it within the SSE
data associated with a set of transport connections.
6.3. Processing Incoming Application Data
After having established an SSE session, the packets will be sent to
the transport layer for de-encapsulation. After header removal, the
socket processing will hand it to the SEE processing for security
check. If the packet is deemed secure, the socket will remove the
SSE envelope. The application see the byte stream as data from a
transport connection.
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The application doesn't need to know SPI, sequence number or key,
relying on a fake connection. (but its local SSE instance knows it,
hence the application own memory where those are stored).
7. Negotiating SSE
The use of SSE and its options (e.g. AES mode of operation) should
be part of the communication start up process. Although SSE can be
manually set up, this may result in a lack of crypto agility . That
is, only one algorithm is used and cannot easily be changed. Thus
manual set up for SSE should be limited to testing needs.
7.1. Using IKEv2
At set up, and application may call IKEv2 [RFC7296]. Currently there
are no defined options for SSE in IKEv2 and it have to be amended.
It should be able to follow ESP in Transport Mode [RFC4303].
7.2. Using HIP
At set up, and application may call HIPv2 [RFC7401] or HIP-DEX
[I-D.ietf-hip-dex].
HIP does not currently include a negotiation for SSE. SSE can be
added by assigning a HIP parameter value for an SSE Transform that is
higher than ESP. A value of 4101 can be used for this purpose. The
negotiation will mirror the ESP transform negotiation [RFC7402] and
be carried in the R1 and I2 payloads as is ESP transform. This
parameter and negotiation may be explicitly expanded here at in a
later revision.
8. IANA Considerations
IANA is requested to assign a HIP parameter value for the SSE
Transform. This parameter value should be higher than ESP. A value
of 4101 is recommended.
9. Security Considerations
As SSE uses an AEAD block cipher, it is vulnerable to attack if a
sequence number is reused for a given key. Thus implementations of
SSE MUST provide for rekeying prior to Sequence Number rollover. An
implementation should never assume that for a given context, the
sequence number space will never be exhausted. Key Management
Protocols like IKEv2 [RFC7296] or HIP [RFC7401] could be used to
provide for rekeying management. The KMP SHOULD not create a network
layer fate-sharing limitation.
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As any security protocol can be used for a resource exhaustion
attack, implementations should consider methods to mitigate flooding
attacks of messages with valid SPIs but invalid content. Even with
the ICV check, resources are still consumed to validate the ICV.
SSE makes no attempt to recommend the ICV length. For constrained
network implementations, other sources should guide the
implementation as to ICV length selection. The ICV length selection
SHOULD be the the responsibility of the KMP.
As with any layered security protocol, SSE makes no claims of
protecting lower or higher processes in the communication stack.
Each layer's risks and liabilities need be addressed at that level.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
10.2. Informative References
[I-D.ietf-hip-dex]
Moskowitz, R. and R. Hummen, "HIP Diet EXchange (DEX)",
draft-ietf-hip-dex-05 (work in progress), February 2017.
[I-D.moskowitz-gpcomp]
Moskowitz, R., Hares, S., Faynberg, I., Lu, H., and P.
Giacomin, "GPCOMP", draft-moskowitz-gpcomp-01 (work in
progress), October 2016.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)",
RFC 4303, DOI 10.17487/RFC4303, December 2005,
<http://www.rfc-editor.org/info/rfc4303>.
[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
Kivinen, "Internet Key Exchange Protocol Version 2
(IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
2014, <http://www.rfc-editor.org/info/rfc7296>.
[RFC7401] Moskowitz, R., Ed., Heer, T., Jokela, P., and T.
Henderson, "Host Identity Protocol Version 2 (HIPv2)",
RFC 7401, DOI 10.17487/RFC7401, April 2015,
<http://www.rfc-editor.org/info/rfc7401>.
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[RFC7402] Jokela, P., Moskowitz, R., and J. Melen, "Using the
Encapsulating Security Payload (ESP) Transport Format with
the Host Identity Protocol (HIP)", RFC 7402,
DOI 10.17487/RFC7402, April 2015,
<http://www.rfc-editor.org/info/rfc7402>.
Authors' Addresses
Robert Moskowitz
HTT Consulting
Oak Park, MI 48237
Email: rgm@labs.htt-consult.com
Igor Faynberg
Stargazers Consulting, LLC
East Brunswick, NJ 08816
USA
Email: igorfaynberg@gmail.com
Huilan Lu
Retired
Email: huilanlu2@gmail.com
Susan Hares
Hickory Hill Consulting
7453 Hickory Hill
Saline, MI 48176
USA
Email: shares@ndzh.com
Pierpaolo Giacomin
FreeLance
Email: yrz@anche.no
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