Overview of CALEA Conformance Proposed Standard

PTSC-LAES-2006-084R6

Manish Karir,

Merit – Research and Development

Outline

1. Architectural Assumptions – Internet Access Service Provider Model– Electronic Surveillance Model– Vocabulary Building

2. CALEA Functions– Functional Breakdown of Components– Architecture, Interfaces and Intercept Access

Points

3. CALEA conformance– Timing Requirements– CmII/CmC Packet Formats and Encapsulation– General IASP Requirements

4. Re-Cap and Conclusions

Internet Access Services Model

Source: PTSC-LAES-2006-084R6

Internet Access and Services ModelThree Aspects to Gaining Access

1. Reg-F - Registration Function:» The act of a user getting access to the

network (e.g. login/authentication of any sort)

2. Res-F - Reservation Function:» The user requesting resources from the

network (e.g. requesting an IP address, temporary addresses are not included)

3. PT-F - Packet Transfer Function:» Transfer of Layer-3 packets to/from the

Internet

Electronic Surveillance ModelComponents and Responsibilities

1. Service Provider AdministrationResponsible for the Access and Delivery

Functions2. Access Function (AF)

Consists of one or more Intercept Access Points (IAPs)

3. Delivery Function (DF)Transfer of data from the Access

Function to the Collection Function

4. Law Enforcement AdministrationControls the LEA collection function

5. Collection Function (CF)Location where the communication

intercepts are stored

Law EnforcementResponsibility

Internet Access Service Provider Responsibility

Electronic Surveillance Model

Source: PTSC-LAES-2006-084R6

More Definitions /Acronyms LI - Lawful Intercept CmII - Communication Identifying Information

(e.g. packet headers…but more…) CmC - Communication Content (e.g. the packets) IAP - Intercept Access Point Combinations:

– AACmII - Access Associated CmII– CACmII - Content Associated CmII– CmC-IAPs - The point in the network where

communication content is intercepted– CmII-IAPs - The point in the network where

communication headers are intercepted– Note: CmC-IAPs might be different from CmII-

IAPs

The 3 Key Concepts1. CmC - Communication Content

– Captured at CmC-IAPs, full packets– Packets are passed to Delivery

Function(DF)– The DF transfers these to the LEA

Collection Function (CF)

2. AACmII - Access Associated CmII– Essentially login/logout and authorization

activity– DHCP IP address assigned– Information provided to CF via the DF cont.

The 3 Key Conceptscont.

3. CACmII - Content Associated CmII - 2 methods– Intercept packet stream to/from subject

and extract IP header information, port information is optional,(but might be authorized) finally deliver all header information to DF or deliver summary records

– Sample subjects flows such that no flow can exist without being sampled and deliver summary records to LEA

Functional Breakdown

CmC/CmII Access Function (AF):– Responsible for identifying/isolating

CmC/CmII for the subject and presenting it to the MF/DF

CmC/CmII Mediation Function (MF):– Responsible for the presentation of

captured information into the appropriate format for delivery to LEA

CmC/CmII Deliver Function (DF):– Responsible transmitting data from IASP to

the collection function of the LEA

Functional Lawful Intercept Architecture

Source: PTSC-LAES-2006-084R6

DFApplication

7

6

5

4

3

2

1

A-PDU

DF -DM (A-PDU)

IASPDomain

A-PDUDemarcation

Point

Delivery Method

OSIProtocol Stack

CmC & CmII

Delivery Function

A-PDU = Application Protocol Data Unit (formatted for ŌeÕinterface)DF-DM (A -PDU) = encapsulated A - PDU sent by the Delivery Function Õs Delivery Method

ŌeÕ

PhysicalDemarcation

Point

CF

Application7

6

5

4

3

2

1

LEA

Domain

CollectionFunction

Delivery

Method

OSIProtocol Stack A -A -PDU C mC & C mII

Packet Delivery Interface DF-CF Interface

Source: PTSC-LAES-2006-084R6

Intercept Access Points

Delivery Timing Requirements1. Event Timestamps: Each intercepted message

should contain an accurate timestamp – CmII: timestamp should be accurate to within

200ms– CmC: timestamps need to be provided with

each packet

2. Event Timing: Intercepted messages should be sent to LEA within specified time window– CmII should be sent by the DF to the CF within

8 seconds 95% of the time– CmC: ???

Timing Requirements

Source: PTSC-LAES-2006-084R6

T1 is dependent in IASPT2 is jointly determined by IASP and LEA by choice of agreed upon protocols and facilities

CmII Access Messages

Access Messages: Notify LEA of access related functions performed by the subject including:

Access Attempt (login) - subject begins the network authentication process

Access Accepted - sent when subject has successfully authenticated with network AAA

Access Failed - user provides invalid username/ password or MAC address

cont.

CmII Access Messagescont.

Access Session End (logout) - subject initiates disconnect

Access Rejected - network rejects login attempt e.g. user is already logged in somewhere else and network does not allow multiple logins

Signaling Message Report - (RADIUS, DIAMETER, etc.) may be used in place of the previous messages

CmII Packet Data Messages

Packet Data Messages: Notify LEA of data related events performed by the subject

Packet Data Session Start - sent when subject completes login and and IP address has been assigned

Packet Data Session Failed - login is successful but no IP address, e.g. DHCP pool exhausted

Packet Data Session End - session timeout

CmII Packet Data Messages

Packet Data Messages: Notify LEA of data related events performed by the subject

Packet Data Session Already Established - when surveillance starts after subject login

Packet Data Header Report - packet header reports on a per-packet basis

Packet Summary Report - periodic summary reports of packet header data

Example CmII Message Formats

Information Element M/O/C Condition

Case Identity MIAP System Identity MTime Stamp MContent Identifier MHeader Set M

Access AcceptedCmII Message

Information Element M/O/C Conditions

Case Identity M

IAP System Identity M

Time Stamp M

Subscriber Identity M

Access Method C Provide when known.

Network Access Node Identity C Provide when known.

IP Address C Provide when known.

Access Session Identity M

Access Session Characteristics C Provide when known.

Location Information C Provide when reasonably available and lawfullylawfully authorized.

Protocol Signal O

Packet Header Data Report CmII Message

CmC Message Delivery Options SCTE Datagram Format ATIS IAS Datagram

– Encapsulation Approach - one packet per encapsulated datagram

– UDP/IP based encapsulation; TCP or other transport protocols are optional

– IC-APDU - Protocol Data Unit Approach - multiple packets per Datagram

We focus on the IAS Datagram approach as it is the simplest

IAS Datagram Encapsulation Approach One intercepted packet in

each encapsulated UDP datagram

Src IP is the address of DF Dst IP is address of CF

Port numbers in UDP header may be agreed upon by LEA and IASP

ContentID field is ASCII value that allows correlation between CmC and CmII

Encapsulation IP Header

Encapsulation UDP Header

Content ID

Time Stamp

Intercepted Packet

**Timestamp is RFC3339 compliant: YYYY-MDDThh:mm:ss.sssZ**Intercepted Packet includes all headers

IAS Datagram - APDU Approach

A simple extension of theencapsulation approach, to include multiple intercepted packets in a single encapsulated packet.

Encapsulation IP Header

Encapsulation UDP Header

Number of CmC-APDUs

Length of 1st CmC-APDU

Length of 2nd CmC-APDU

Length of last CmC-APDU

1st CmC-APDU

2nd CmC-APDU

Last CmC-APDU

Content ID

Time Stamp

Sequence Number

Intercepted Packet

Subject IdentificationTwo Aspects

1. Login Identification:

– When network requires authentication prior to use

– CmC and CmII is performed only after subject has been identified on the network

– After login; subject can be identified via unique IP address or session identifier assigned to subject during login

cont.

Subject IdentificationTwo Aspects, cont.

2. Equipment Identification:

– When network does not require authentication prior to use

– Subject is identified via unique address or interface

– Intercept in this scenario may be based on MAC address, IP address or physical/logical port

Six IASP Requirements

1. Privacy: IASP shall not monitor or permanently record subjects communications

2. Isolation: IASP shall ensure that only the subjects communication is intercepted

3. Transparency: IASP shall perform the intercept in a manner such that the subject cannot reasonably detect that intercept is being performed

cont.

Six IASP Requirementscont.

4. Encryption/Compression: IASP shall deliver the intercept data unencrypted or provide the LEA with encryption method and keys. IASP shall provide data uncompressed or identify means to decompress

5. Security/Integrity: IASP shall ensure unaltered delivery of intercept data. Security is to be negotiated between IASP and LEA

6. Performance/Quality: IASP should be able to perform multiple intercepts at the same time

Re-cap and Conclusions

• This is a simplified overview of the standard- Not a substitute for a detailed reading

and interpretation.• This is a broad introduction to the draft

standard. - Terminology used- Rough of the structure of the

proposed standardcont.

Re-cap and Conclusions – Remember:

1. The standard itself is unclear in certain areas, for example:– The use of encryption by IASP to protect

the CmC– Specifics such as what is the caseID and

how is it different from content identifier, IAP system identity, subscriber ID etc.

– Implementation details such as what are the sizes of the various fields in the packet headers, what are the timing requirements for CmC delivery

2. Important to remember that it is still a “draft” standard and subject to revision.