CGA-TSIG: An Algorithm for Secure DNS Authentication and DNS Confidentiality
draft-rafiee-intarea-cga-tsig-08
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Expired".
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|
|---|---|---|---|
| Authors | Hosnieh Rafiee , Martin von Loewis , Christoph Meinel | ||
| Last updated | 2014-06-02 | ||
| Replaces | draft-rafiee-cga-tsig | ||
| RFC stream | (None) | ||
| Formats | |||
| Reviews | |||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | I-D Exists | |
| Telechat date | (None) | ||
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| Send notices to | (None) |
draft-rafiee-intarea-cga-tsig-08
DNS Extensions H. Rafiee
INTERNET-DRAFT Huawei
Updates RFC 2845 (if approved) M. v. Loewis
Intended Status: Standards Track C. Meinel
Hasso Plattner Institute
Expires: December 2, 2014 June 2, 2014
CGA-TSIG: An Algorithm for Secure DNS Authentication and DNS
Confidentiality
<draft-rafiee-intarea-cga-tsig-08.txt>
Abstract
This document describes a new mechanism for secure DNS authentication
and DNS data confidentiality. The purpose of this document is to
reduce human interaction during different DNS scenarios such as the
communications of resolvers to stub resolvers, recursive resolvers to
Authoritative Name Server, Dynamic DNS updates, (especially updating
PTR and FQDN records (RFC4703)) and zone transfers. This document
also considered for the support of both IPv4 and IPv6.
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 working
documents as Internet-Drafts. The list of current Internet-Drafts is
at http://datatracker.ietf.org/drafts/current.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 2, 2014.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved. This document is subject to
BCP 78 and the IETF Trust's Legal Provisions Relating to IETF
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Documents (http://trustee.ietf.org/license-info) in effect on the
date of publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Problem Statement . . . . . . . . . . . . . . . . . . . . 4
1.2. Current Solutions and Requirements . . . . . . . . . . . 5
1.2.1. Transaction SIGnature (TSIG) . . . . . . . . . . . . 5
1.2.2. DNS Security Extension (DNSSEC) . . . . . . . . . . . 5
2. Conventions Used In This Document . . . . . . . . . . . . . . 6
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Algorithm Overview . . . . . . . . . . . . . . . . . . . . . 7
4.1. CGA-TSIG . . . . . . . . . . . . . . . . . . . . . . . . 7
4.1.1. The CGA-TSIG DATA Structure . . . . . . . . . . . . 7
4.1.2. CGA-TSIG Data . . . . . . . . . . . . . . . . . . . 9
4.1.2.1. IPv6 Specific Data . . . . . . . . . . . . . . . 9
4.1.2.2. IPv4 Specific Data . . . . . . . . . . . . . . . 10
4.1.3. Generation of CGA-TSIG DATA . . . . . . . . . . . . 10
4.2. CGA-TSIGe . . . . . . . . . . . . . . . . . . . . . . . . 11
4.2.1. The CGA-TSIGe DATA Structure . . . . . . . . . . . . 11
4.2.1.1. Public Key Request . . . . . . . . . . . . . . . 12
4.2.1.2. Public Key Response . . . . . . . . . . . . . . . 13
4.2.2. Generation of CGA-TSIGe DATA . . . . . . . . . . . . 13
4.2.2.1. IPv6 Specifics . . . . . . . . . . . . . . . . . 13
4.2.2.2. IPv4 Scenario . . . . . . . . . . . . . . . . . . 16
4.2.3. Process of Encrypted DNS Message . . . . . . . . . . 17
5. CGA-TSIG/CGA-TSIGe Use Case Scenarios . . . . . . . . . . . . 17
5.1. DNS Zone Transfer . . . . . . . . . . . . . . . . . . . . 17
5.1.1. Verification Process . . . . . . . . . . . . . . . . 18
5.2. The FQDN Or PTR Update (IPv6 only) . . . . . . . . . . . 20
5.2.1. Verification Process . . . . . . . . . . . . . . . . 20
5.3. DNS Resolving Scenario (stub to recursive) . . . . . . . 21
5.3.1. Client Verification Process (CGA-TSIGe only) . . . . 21
5.3.2. Resolver Verification Process . . . . . . . . . . . . 22
5.4. DNS Resolving Scenario (Authoritative NS to Recursive NS) 23
6. SeND Is Not Supported (IPv6 only) . . . . . . . . . . . . . . 23
7. CGA-TSIG/CGA-TSIGe Sample Applications . . . . . . . . . . . 24
7.1. IP Spoofing . . . . . . . . . . . . . . . . . . . . . . 24
7.2. Resolver Configuration Attack . . . . . . . . . . . . . . 24
7.3. Exposing A Shared Secret . . . . . . . . . . . . . . . . 25
7.4. Replay Attack . . . . . . . . . . . . . . . . . . . . . 25
7.5. Data Confidentiality . . . . . . . . . . . . . . . . . . 25
8. Security Considerations . . . . . . . . . . . . . . . . . . . 25
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26
10. Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . 26
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10.1. A Sample Key Storage For CGA-TSIG . . . . . . . . . . . 26
10.2. Stored parameters in the node . . . . . . . . . . . . . 27
10.3. CGA Generation Script . . . . . . . . . . . . . . . . . 27
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 28
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 29
12.1. Normative . . . . . . . . . . . . . . . . . . . . . . . . 29
12.2. Informative . . . . . . . . . . . . . . . . . . . . . . . 30
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 32
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1. Introduction
Transaction SIGnature (TSIG) [RFC2845] is a protocol that provides
endpoint authentication and data integrity through the use of one-way
hashing and shared secret keys in order to establish a trust
relationship between two or more hosts, which can be either a client
and a server, or two servers. The TSIG keys, which are manually
exchanged between a group of hosts, need to be maintained in a secure
manner. This protocol is mostly used today to secure a Dynamic DNS
Update, or to assure a Slave Server that the zone transfer is from
the original Master Server and that it has not been corrupted. It
does this by verifying the signature using a cryptographic key that
is shared with the receiver.
Handling this shared secret in a secure manner and exchanging it does
not appear to be easy. This is especially true if the IP addresses
are dynamic or the shared secret is exposed to the attacker. To
address these existing problems with TSIG, as well as considering DNS
data protection (privacy), and to solve existing problems with the
current DNS security extensions, this document proposes two
algorithms which support both IPv4 and IPv6 scenarios. In the IPv6
scenario, the algorithms use Cryptographically Generated Addresses
(CGA) [RFC3972] or Secure Simple Addressing Scheme for IPv6
Autoconfiguration (SSAS) as a new algorithm in the TSIG Resource
Record (RR). CGA is an important option available in Secure Neighbor
Discovery (SeND) [RFC3971], which provides nodes with the necessary
proof of IP address ownership by providing a cryptographic binding
between a host's public key and its IP address without the need for
the introduction of infrastructure.
This document addresses the DNS data confidentiality by using both
asymmetric and symmetric cryptography. This document updates the
following sections in TSIG document:
- Section 4.2: The server MUST not generate a signed response to an
unsigned request => The server MUST not generate a signed response to
an unsigned request, unless the Algorithm Name filed contains
CGA-TSIG or CGA-TSIGe.
- Section 4.5.2: It MUST include the client's current time in the
time signed field, the server's current time (a u_int48_t) in the
other data field, and 6 in the other data length field => It MUST
include the client's current time in the time signed field, the
server's current time (a u_int48_t) in the other data field, and if
the Algorithm Name is CGA-TSIG or CGA-TSIGe, then add the length of
this client's current time to the total length of Other DATA field.
The client's current time in this case will be placed after the
CGA-TSIG/CGA-TSIGe Data.
1.1. Problem Statement
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There are several different methods where DNS records can become
compromised. Some examples of methods are DNS Spoofing; DNS
Amplification Attacks; Resolver Source IP Spoofing; Unauthorized DNS
Update; User Privacy Attack; and Human Intervention.
1.2. Current Solutions and Requirements
1.2.1. Transaction SIGnature (TSIG)
Advantages:
- Provide a secure level authentication
- Signs DNS messages
Disadvantages:
- Not scalable and applicable for specific scenarios. Currently there
is little deployment of TSIG for resolver authentication with
clients. One reason is that resolvers respond to anonymous queries
and can be located in any part of the network.
- Offline exchange of shared secrets. For each group of hosts there
needs to be one shared secret and the administrator will need to
manually add it to the DNS configuration file for each of these
hosts. This manual process will need to be invoked in the case where
one of these hosts is compromised and the shared secret is well known
to the attacker. It will also have to be invoked in the case where
any of these hosts needs to change their IP addresses, such as
privacy issues explained in RFC4941 [RFC4941], or when moving
networks, etc. The manual TSIG process for the exchange of shared
secrets makes it difficult to configure each new client with the
shared secret of a DNS server like a resolver. Another problem with
TSIG would be when this shared secret is leaked and makes it
necessary to repeat this process.
- Does not easily protect DNS data confidentiality. TSIG provides the
node with transaction level authentication and it is not used for
encrypting the content of DNS messages.
1.2.2. DNS Security Extension (DNSSEC)
Advantages:
- Signs DNS messages and provide data integrity
- Authorize a node to update certain zone file
Disadvantages:
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- Offline generation of the signature
DNSSEC [RFC6840] needs manual step for the configuration. For
instance, when a DNSSEC needs to sign the zone offline.
- IP spoofing
The public key verification in DNSSEC creates a chicken-and- egg
situation. In other words, the key for verifying messages should be
obtained from the DNSSEC server itself. This is why a query requester
needs to verify the key.
If this does not happen, DNSSEC is vulnerable to an IP spoofing
attack.
- Does not easily protect DNS data confidentiality for the resolver
scenario
Since a part of configuration is manual and DNS resolver needs to
answer to anonymous queries, it is not possible to exchange the DNS
keys with anonymous nodes over the internet. Even though it was
possible, there is still no clear solution to encrypt all the data
during DNS resolving scenario.
2. Conventions Used In This Document
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].
In this document, these words will appear with that interpretation
only when in ALL CAPS. Lower case uses of these words are not to be
interpreted as carrying RFC 2119 significance.
=> This sign in the document should be interpreted as "change to".
IPv6 only: this indicates that the explained approach can be used
only in IPv6 scenario
IPv4 only: this indicates that the explained approach can be used
only in IPv4 scenario
IPv4 and IPv6: This indicates that the explained approach can be used
in both IPv4 and IPv6 scenario and there are no differences.
3. Terminology
The terms used in this document have the following standard meaning:
- Bot: a malicious program that is installed on a node and allows an
attacker to control some functions of that node to send malicious
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messages.
- Name Server: A server that supports DNS service.
- Recursive Name Server: A Name Server that responds to all queries.
- Stub Resolver: A DNS resolver that is unable to resolve queries
recursively, and relies on a Recursive DNS Server to resolve queries.
- Authoritative Name Server: Provides answers to DNS queries that it
contains in its system configuration.
There are two types of Authoritative Name Servers:
1. Master Server (Primary ): A Master Server stores the original
copies of all zone records. Each Slave Server gets updated via a
special automatic updating mechanism within the DNS protocol. All
Slave Servers maintain identical copies of the master records.
2. Slave Server (Secondary): A Slave Server is an exact replica of
the master server.
- Root Name Server: An Authoritative Name Server for the root domain
(i.e., '.' (dot))
- Client: a client can be any computer (server, laptop, etc) that
only supports stub DNS servers and not other DNS services. It can be
a mail server, web server or a laptop computer.
- Node: a node can be anything such as a client, a DNS server
(resolver, authoritative) or a router.
- Host: all nodes except routers
4. Algorithm Overview
The following sections explain the CGA-TSIG data structure in IPv4
and IPv6 scenarios. A CGA-TSIG data structure is an option to the
TSIG Resource Record (RR).
4.1. CGA-TSIG
4.1.1. The CGA-TSIG DATA Structure
The CGA-TSIG data structure SHOULD be added to the Other DATA section
of the RDATA field in the TSIG Resource Record (RR) (see figures 1
and 2). The DNS RRTYPE MUST be set to TSIG [RFC2845]. The RDATA
Algorithm Name MUST be set to CGA-TSIG. The CGA-TSIG name is used
when there is no need for DNS data confidentiality. The CGA-TSIGe
(Please refer to section 4.2) is used when all parts of a DNS message
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should be encrypted to provide data confidentiality. The Name MUST be
set to root (.).This is the smallest possible value that can be used.
The MAC Size MUST be set to 0 when the Algorithm Name is CGA-TSIG.
A detailed explanation of the standard RDATA fields can be found in
section 2.3 [RFC2845]. This document focuses only on the new
structure added to the Other DATA section. These new fields are
CGA-TSIG Len and CGA-TSIG DATA. The TSIG RR is added to an additional
section of the DNS message.
+---------------------------------------+
| Algorithm Name |
| (CGA-TSIG) |
+---------------------------------------+
| Time Signed |
| |
+---------------------------------------+
| Fudge |
| |
+---------------------------------------+
| MAC Size |
| |
+---------------------------------------+
| MAC |
| |
+---------------------------------------+
| Original ID |
| |
+---------------------------------------+
| Error |
| |
+---------------------------------------+
| Other Len |
| |
+---------------------------------------+
| Other Data |
| |
+---------------------------------------+
Figure 1: Modified TSIG RDATA
The CGA-TSIG DATA Field and the CGA-TSIG Len will occupy the first
two slots of Other DATA. Figure 2 shows the layout. Any extra
options/data should be placed after CGA-TSIG field. CGA-TSIG Len is
the length of CGA-TSIG DATA in byte.
+---------------------------------------+
| CGA-TSIG Len |
| (2 bytes) |
+---------------------------------------+
| CGA-TSIG DATA |
| |
+---------------------------------------+
| Other Options |
| |
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+---------------------------------------+
Figure 2: Other DATA section of RDATA field
4.1.2. CGA-TSIG Data
The following table explains the CGA-TSIG data structure. Fields that
are marked (varies) are different depending on IPv6 or IPv4.
CGA-TSIG DATA Field Name Data Type Notes
--------------------------------------------------------------
AsyAlgorithm 15 octet Asymetric algorithm. IANA numeric value for RSA
algorithm 1.2.840.113549.1.1.1[RFC4055]
Type u_int16_t (varies) Name of algorithm
IP Tag 4 octet (varies) Tag used to identify the IP address
Parameters Len octet Length of parameters
Parameters variable (varies)
Signature Len octet Length of CGA signature
Signature variable Section 3.2.1 of this document
Old Pubkey Len variable Length of old public key field
Old Pubkey variable Old public key in ASN.1 DER format
(same format as public key)
Old Signature Len variable Length of old signature field
Old Signature variable Old signature generated by old
public key.
The IP Tag is one of the old IP addresses of the Node. A client's
public key can be associated with several IP addresses on a server.
The DNS server SHOULD store the IP addresses and the public keys to
indicate their association. If a client wants to add RRs by using a
new IP address, then the IP tag field will be zeroed out. The server
will then store the new IP address that was passed to it in storage.
If the client wants to replace an existing IP address in a DNS Server
with a new one, then the IP Tag field will be populated with the IP
address which is to be replaced. The DNS server will then look for
the IP address referenced by the IP tag stored and replace it with
the new one. This enables the client to update his own RRs using
multiple IP addresses while, at the same time, giving him the ability
to change IP addresses. If a Node changes its public key, then it
MUST add the old public key to the Old Pubkey field. It MUST also
retrieve the current time from the Time Signed field, sign it using
the old private key, and then add the signature to the old signature
field. This enables the verifier node to authenticate a host with a
new public key. The verification steps are explained in detail in
sections 5.1., 6.1 and 7.1.
4.1.2.1. IPv6 Specific Data
For IPv6, the Type field indicates the Interface ID generation
algorithm that is used in SeND (An Interface ID is the 64 rightmost
bits of an IPv6 address). The field allows for future development.
The default value for CGA is 1. IP Tag for IPv6 is 16 octets.
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4.1.2.2. IPv4 Specific Data
For IPv4, the Type field indicates the hashing function used to
generate the hash of (public key + IPv4). By default, it is SHA256.
This value SHOULD be set to 1 for SHA256 and other numeric
incremental value for other SHA algorithms. This allows for future
hashing functions.
4.1.3. Generation of CGA-TSIG DATA
In order to use CGA-TSIG as an authentication approach, some of the
parameters need to be cached during IP address generation. If no
parameters are available in the cache, please see section 6.
1. Obtain Require Parameters From Cache.
For IPv6, if the Type Field above is CGA, then the parameters that
SHOULD be cached are the modifier, algorithm type, location of the
public/private keys and the IP addresses of the host. For IPv4, the
location to the key pairs need to be cached in order to generate the
signature. If this node changes its IP address, it also needs to
cache the old IP address.
Note: If the node is a DNS server (resolver or Authoritative Name
Server) that does not support SeND but wants to use the CGA-TSIG
algorithm, a script can be used to generate the CGA parameters.
(Please refer to the section 10.2. appendix)
2. Generate Signature
The 128-bit CGA Message Type tag value for SeND is 0x086F CA5E 10B2
00C9 9C8C E001 6427 7C08. This value is concatenated with the entire
DNS message (Please refer to figure 3 and figure 4) and the private
key obtained from the cache. This signature MUST be added to the
signature field of the CGA-TSIG DATA record. The Time Signed field
uses the same timestamp in RDATA. This will prevent replay attacks by
changing the signature each time a Node sends a DNS message. The
format of DNS messages is explained in section 4.1.3 [RFC1035].
3. Generate Old Signature
If the Nodes generated new key pairs, they need to add the old public
key, signed by the old private key, to the CGA-TSIG DATA. A Node will
sign the new public key with the old private key, and then will add
the contents of this signature to the old signature field of CGA-TSIG
DATA. This step MUST be skipped when the Node did not generate new
key pairs.
+-----+------+--------+
|Type |Length|Reserved|
|1byte|1 byte| 1 byte |
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+---------------------+
| Header |
| 12 bytes |
+---------------------+
| Zone section |
| variable length |
+---------------------+
| prerequisite |
| variable length |
+---------------------+
| Update section |
| variable length |
+---------------------+
| Additional Data |
| variable length |
+---------------------+
Figure 3 DNS update message
+-----+------+--------+
|Type |Length|Reserved|
|1byte|1 byte| 1 byte |
+---------------------+
| Header |
| 12 bytes |
+---------------------+
| Question |
| variable length |
+---------------------+
| Answer |
| variable length |
+---------------------+
| Authority |
| variable length |
+---------------------+
| Additional Data |
| variable length |
+---------------------+
Figure 4 DNS Query message (section 4.)
4.2. CGA-TSIGe
One possible solution to provide the DNS server with data
confidentiality during DNS update or other DNS query processes is the
use of symmetric encryption with CGA-TSIG that is called CGA-TSIGe.
4.2.1. The CGA-TSIGe DATA Structure
The Node MUST set the Algorithm Type in TSIG RDATA to CGA-TSIGe.
Other sections of CGA-TSIGe DATA are similar to CGA-TSIG DATA. This
section only explains the differences between CGA-TSIG and CGA-TSIGe.
Figure 5 shows CGA-TSIGe DATA structure. The value of Message Hash is
the concatenation of the 3 bits hashing algorithm identifier with the
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hash of the whole DNS message (see figure 3 and 4 for the whole DNS
message). This is used for data integrity of the packet. For SHA256,
the value of hashing algorithm SHOULD set to 1. For other hashing
algorithms, this 3 bits SHOULD set to sequential value after one. The
field Message Hash Len is the length of Message Hash.
+---------------------------------------+
| AsyAlgorithm |
| |
+---------------------------------------+
| Type |
| |
+---------------------------------------+
| IP tag |
| (16 bytes) |
+---------------------------------------+
| Parameter Len |
| (1 byte) |
+---------------------------------------+
| Parameters |
| (variable) |
+---------------------------------------+
| Signature Len |
| (1 byte) |
+---------------------------------------+
| Signature |
| (variable) |
+---------------------------------------+
| old pubkey Len |
| (1 byte) |
+---------------------------------------+
| old pubkey |
| (variable) |
+---------------------------------------+
| old Signature Len |
| (1 byte) |
+---------------------------------------+
| old Signature |
| (variable) |
+---------------------------------------+
| Message Hash Len |
| (1 byte) |
+---------------------------------------+
| Message Hash |
| (variable) |
+---------------------------------------+
Figure 5 CGA-TSIGe DATA Field
4.2.1.1. Public Key Request
In the TSIG RDATA section, the Algorithm Name MUST be set to
'CGA-TSIGe', and the CGA-TSIGe Len field MUST be set to zero. This
alerts the DNS server that the other Node needs its public key for
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encryption purposes. This format is used if a Node does not want to
use DNSKEY RR [RFC3757] to retrieve the public key of the DNS server.
4.2.1.2. Public Key Response
The DATA structure is similar to CGA-TSIG. There is only a flag field
which indicates that it is a response to the public key request
message.
+---------------------------------------+
| AsyAlgorithm |
| |
+---------------------------------------+
| Type |
| |
+---------------------------------------+
| Parameter Len |
| (1 byte) |
+---------------------------------------+
| Parameters |
| (variable) |
+---------------------------------------+
| Signature |
| (variable) |
+---------------------------------------+
| Signature Len |
| (1 byte) |
+---------------------------------------+
| Signature |
| (variable) |
+---------------------------------------+
| Flag |
| (1 bit) |
+---------------------------------------+
Figure 6 CGA-TSIGe DATA Field (public key response)
4.2.2. Generation of CGA-TSIGe DATA
4.2.2.1. IPv6 Specifics
Nodes can securely obtain the IP address of DNS resolvers from the
DHCPv6 server (use SAVI-DHCP [savi-dhcp]); or from a DNS option of
Router Advertisement message [RFC6106] after authenticating with the
router via a trusted authority. The IP addresses can be generated
using CGA, SSAS or other mechanisms. (tjw:Last Sentence)
This is the same approach that a Node can use for obtaining a DNS
server IP address during a Dynamic DNS update. However, for a zone
transfer to avoid any malicious update to DNS server, it is
RECOMMENDED that this IP address is set manually on the DNS server
for the first time.
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1. Retrieve Public Key of DNS Server
To encrypt the DNS message using a symmetric algorithm for
performance purposes, first, a Node needs to retrieve the public key
of the DNS server. It is possible to use the current DNSKEY RR
[RFC3757] to send the public key of the DNS server. When the client
wants to update any records on the DNS server, it first sends a DNS
message asking for the public key of the DNS Server. The DNS Server
then answers this query and includes the public key contained in the
DNSKEY RR with the SEP flag set to zero (0). This indicates that it
is not the zone key. It is also possible to use the RR format
explained in section 4.2.1 of this document. The DNS server SHOULD
include CGA-TSIGe DATA so that the client can verify its IP address.
In this case, there will be a binding between a DNS Server's public
key and its IP address. If the Node can verify the DNS Server public
key (explained below), it goes to step 2. Otherwise it discards the
DNS message without further action.
2. Obtain Required Parameters From Cache.
This step is the same as what is explained in section 4.1.3.
3. Generation of Secret Key
After a successful verification, the Node generates a 16 byte random
number called a secret key. The Node can use any algorithm explained
in [RFC4086] to generate a good randomized value. It encrypts the
secret key using the DNS Server public key. Then, the Node sets the
MAC in TSIG RDATA to the digest of secret key and set the MAC Size to
the length of this digest. The DNS Server knows what to do with MAC
field from the Algorithm Type in TSIG. If it is CGA-TSIGe, then it
looks for this encrypted secret key.
4. Encryption of DNS message
The Node uses the secret key generated in the previous step to
encrypt the header, zone section, prerequisite, and update section
for the DNS update message (see figure7) or encrypt header, question,
answer, authority of a DNS Query (see figure 8). It then calculates
the length of a digest as a number of bytes in multiples of 8. For
example, if the digest is 242 bytes then 242 = (30 * 8) + 2.
Therefore, 6 bytes are added as padding, and then 31 is placed at the
beginning of digest (see figure 9). If there is no padding for the
digest then one zero-filled byte will be added at the end of digest.
This allows the DNS Server to interpret this digest as a long string.
+-----+------+--------+
|Type |Length|Reserved|
|1byte|1 byte| 1 byte |
+---------------------+
| Header |
| 12 bytes |
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+---------------------+
| Encrypted sections |
| variable length |
+---------------------+
| Additional Data |
| variable length |
+---------------------+
Figure 7 Encrypted DNS update message
+-----+------+--------+
|Type |Length|Reserved|
|1byte|1 byte| 1 byte |
+---------------------+
| Header |
| 12 bytes |
+---------------------+
| Encrypted sections |
| variable length |
+---------------------+
| Additional Data |
| variable length |
+---------------------+
Figure 8 Encrypted DNS Query message
+---------------------+
| Len of digest |
| (1 byte) |
+---------------------+
| digest |
| variable length |
+---------------------+
Figure 9 Digest format in DNS question section
The Node then adds a new header with the following sample data. This
will allow the DNS Server to process this message. CGA-TSIGe actually
uses the whole encrypted section as one single question followed by
additional data.
Field Sub-field Value Intrepretation
-------------------------------------------------------
ID 0xdb42 Response should have ID 0xdb42
Flags 0x0100
QR 0 It's a query
OPCODE 0 Standard query
TC 0 Not truncated
RD 1 Recursion requested
RA 0 Not meaningful for query
Z 0 Reserved
RCODE 0 Not meaningful for query
QDCOUNT 0x0001 One question follows
ANCOUNT 0x0000 No answers follow
NSCOUNT 0x0000 No records follow
ARCOUNT 0x0001 No additional records follow
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The digest will be interpreted like the following table.
Data Intrepretation
------------------------------------------
0x1f String of length 248 follows
0x777777.. String is xxxxxx
0x00 End of this string
5. Generation of Message Hash
In a case where a DNS Server responds to anonymous queries, as in a
DNS Resolver scenario, the Node executes SHA256 by default on the
whole DNS message. This includes the additional section and the TSIG
RR as a part of additional section of DNS message. It then computes
the Message Hash Len. In this case the message does not need to be
signed by the Node using its private key. This is because the DNS
Server does not expect to verify the Node and it only checks for the
message integrity (tjw:and confidentiality). In the case a message
contains Message Hash, the Node MUST set the Parameters Len ,
Signature Len, Old Pubkey Len and Old Signature Len to zero (0) and
it SHOULD skips steps 6 and 7.
6. Generation of Signature
This step is the same as what is explained in section 4.1.3.
7. Generation of Old Signature
This step is the same as what is explained in section 4.1.3.
4.2.2.2. IPv4 Scenario
The key pairs needs to be cached in order to generate a signature. If
this Node changes its IP address, it also needs to cache the old IP
address. Similar to the IPv6 scenario, the Node can obtain the hash
of (public key + IPv4) and the IPv4 address of the DNS server from a
DHCPv4 server. It can use [savi-dhcp]. If this Node is in unsecured
environment, it can manually add the hash of (public key + IPv4
address) of its trusted DNS server. This is especially true in the
Resolver scenario. The implementers SHOULD define a possibility for
users to change the default value for CGA-TSIGe.
1. Retrieves Public Key of DNS server
This is similar to IPv6 scenario.
2. Obtain Required Parameters From Cache.
This step is the same as what is explained in section 4.1.4.
3. Generation of Secret Key
4. Encryption of DNS Message
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5. Generation of Message Hash
All Three are similar to IPv6 scenario.
6. Generation of Signature
This step is the same as what is explained in section 4.1.4.
7. Generation of Old Signature
This step is the same as what is explained in section 4.1.4.
4.2.3. Process of Encrypted DNS Message
When the DNS server receives the message from any node with TSIG
RDATA Algorithm type set to CGA-TSIGe, it executes the following
steps:
1- Retrieves The Secret Key
The DNS server retrieves the secret key from MAC field. It then
decrypts this secret key using its own private key.
2- Decrypts the DNS Message
The DNS server decrypts the DNS server message using this secret key
and the symmetric algorithm, which by default is AES. The DNS server
can then start the verification process explained in the next
section.
5. CGA-TSIG/CGA-TSIGe Use Case Scenarios
5.1. DNS Zone Transfer
This section discusses the use of CGA-TSIGe for the secure
authentication and encryption of DNS messages exchanged between a
Master Server and a Slave Server. In the case of processing a DNS
zone update ([AI]XFR) for multiple DNS servers (authenticating two
DNS servers), there are three possible scenarios with regard to the
authentication process which differs from that of the authentication
of a Node (client) with one DNS server. This is needed for human
intervention. Since the zone contains important information, both DNS
servers MUST use CGA-TSIGe and encrypt the values. The only exception
is when CGA-TSIG is required for secure authentication and the data
encryption is handled by other protocols.
a. Add The DNS servers' IP address To A Slave Server Configuration
(IPv6 only)
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A DNS server administrator should only manually add the IP address of
the Master Server to the configuration file of the Slave Server. When
the DNS update message is processed, the Slave Server can
authenticate the Master Server based on the source IP address and
then, prove the ownership of this address by use of the CGA-TSIGe
option from the TSIG RR. This scenario will be valid until the IP
address in any of these DNS servers, changes.
To automate this process, the sender's public key of the DNS Update
message must be saved on the other DNS server, after the source IP
address has been successfully verified for the first time. In this
case, when the sender generates a new IP address by executing the CGA
algorithm using the same public key, the other DNS server can still
verify it and add its new IP address to the DNS configuration file
automatically.
b. Retrieve Public/Private Keys From A Third Party Trusted Authority
(TA) (IPv6 only)
The message exchange option of SeND [RFC3971] may be used for the
retrieval of third party certificates. This may be done automatically
from the TA by using the Certificate Path Solicitation and
Certificate Path Advertisement messages. Like in section 5.2, the
certificate should be saved on the DNS server for later use. Whenever
any of those servers want to generate a new IP address, the DNS
update process can be accomplished without human intervention.
c. Store The Hash of (public key + IPv4 address) to DNS configuration
file (IPv4 and IPv6)
An administrator needs to manually generate the hash of the
concatenation of public key with the IPv4 address of the authorized
node the DNS configuration file. Whenever a node wants to change its
IP address or public key, the DNS server can generates this value
automatically and compare with the old value it has and then after a
successful verification steps (it will be explain in next section),
it will replace the old hash value with the new one.
5.1.1. Verification Process
Sender authentication is necessary in order to prevent attackers from
making unauthorized modifications to DNS servers through the use of
spoofed DNS messages. The verification process uses the following
steps:
1. Verify The Signature (IPv4 and IPv6)
The Signature contained in CGA-TSIGe DATA should be verified. This
can be done by retrieving the public key and signature from CGA-TSIGe
DATA and using this public key to verify the signature. If the
verification process is successful, then execute step 2. Otherwise,
the message should be discarded.
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2. Check The Time Signed (IPv4 and IPv6)
The Time Signed value is obtained from TSIG RDATA and is called t(1).
The current system time is then obtained and converted to UTC time
and is called t(2). Fudge time is obtained from TSIG RDATA and is
called t(fudge). If t(1) is in the range of t(2) and t(2) minus/plus
t(Fudge) (see formula 1), then step 3 will be executed. Otherwise,
the message will be considered spoofed and discarded. The range is
used in consideration of the delays that can occur during its
transmission over TCP or UDP. Both times must use UTC time in order
to avoid differences in time based on different geographical
locations.
(t(1) - t(fudge)) <= t(2) <=(t(1) + t(fudge))
Formula: (1)
3. Execute The CGA Verification (IPv6 only)
These steps are in section 5 of [RFC3972]. If the sender of the DNS
message uses another algorithm, instead of CGA, then this step
becomes the verification step for that algorithm. If the verification
process is successful, then step 6 will be executed. Otherwise the
message will be discarded without further action.
4. Generate The Hash of (public key + IP address) (IPv4 only)
The DNS server retrieves the hashing Algorithm Type from the
CGA-TSIGe DATA structure. It then concatenates the Public Key with
the IP address of the update requester and executes the SHA256
algorithm (by default) or another algorithm identified in Type
section of CGA-TSIG DATA RRTYPE. It then compares it with the hash
value available in the DNS configuration. If they are the same, the
Update Message should be processed, otherwise, go to step 5.
5. Generate The Hash of (Old Public Key + IPv4 Address) (IPv4 only)
If the Old Public Key Length is zero, then skip this step and discard
the DNS update message. If the Old Public Key Length is not zero,
then the DNS server retrieves the hashing algorithm Type from the
CGA-TSIGe DATA structure. It then concatenates Old Public Key with
the IP address of the update requester and execute the SHA256
algorithm (by default) or another algorithm identified in Type
section of CGA-TSIGe DATA. It then compares it with the hash value
available in the DNS configuration. If they are the same, the Update
Message should be processed, otherwise, go to step 8.
6. Verify The Source IP Address (IPv6 only)
The source IP Address of the Update requester MUST be checked against
the one contained in the DNS configuration. If they are the same, the
Update Message should be processed, otherwise, proceed to step 7.
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7. Verify The Public Key (IPv6 only)
The DNS server checks whether or not the public key retrieved from
CGA-TSIGe DATA is the same as what is available in the cache where
the public keys and IP addresses are saved. If this Public Key is not
found in the cache, then the update will be rejected. Otherwise, when
the Old Public Key Length is not zero go to step 8.
8. Verify The Old Public Key (IPv4 and IPv6)
If the Old Public Key Length is zero, skip this step and discard the
DNS update message. If the Old Public Key Length is not zero, then
the DNS server will retrieve the Old Public Key from CGA-TSIGe DATA
and check to see if it is the same as what was saved in the DNS
server's cache. If they are the same, execute step 6, otherwise
discard the message.
7. Verify The Old Signature (IPv4 and IPv6)
The Old Signature contained in CGA-TSIGe DATA should be verified.
This can be done by retrieving the Old Public Key and the Old
Signature from CGA-TSIGe DATA and then using this Old Public Key to
verify the Old Signature. If the verification is successful, the
Update Message should be processed and the New Public Key should be
replaced with the Old Public Key in the DNS server. If the
verification process fails, discard the message.
5.2. The FQDN Or PTR Update (IPv6 only)
Normally the DHCPv6 server will update the client's RRs on their
behalf in the scenario where SeND is used as a secure NDP, the Nodes
will need to do this process unless a stateless DHCPv6 server is
available. CGA-TSIG/CGA-TSIGe can be used to give Nodes the ability
of doing this process themselves. In this case the clients need to
include the CGA-TSIG/CGA-TSIGe option to allow the DNS server to
verify them. The verification process is the same as that explained
in the next section except for step 4.
5.2.1. Verification Process
The verification steps are the same as those is explained in section
5.1.1, but removing step 4 and modifying step 5.
1. Verify The Signature
2. Check The Time Signed
3. Execute The CGA Verification
4. Verify The Public Key
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The DNS server checks if the public key retrieved from
CGA-TSIG/CGA-TSIGe DATA is the same as what was available in cache.
If no entry is found for this public key, and the FQDN or PTR is also
not available in the DNS server, then the DNS server will store the
public key of this Node and add this Node's PTR and FQDN. Otherwise
if any PTR is available, and the Node IP tag is empty, or there is
currently another public key associated with the Node's FQDN, then
the update will be skipped. Otherwise, if the Old Public Key Length
is not zero, go to step 5.
5. Verify The Public Key
6. Verify The Old Public Key
7. Verify The Old Signature
5.3. DNS Resolving Scenario (stub to recursive)
A DNS query request sent by a host, such as a client or a mail
server, does not need to generate CGA-TSIG DATA because the resolver
responds to anonymous queries. The Resolver's response SHOULD contain
the CGA-TSIG DATA field in order to verify him. However, the client
needs to include the TSIG RDATA and set the Algorithm Type to
CGA-TSIG, and it MUST set the CGA-TSIG Len to zero (0). This allows
the resolver to include CGA-TSIG in the client.
If the Node needs to deploy DNS data confidentiality, then it needs
to set the Algorithm Type to CGA-TSIGe and follows the step explained
in section 4.2.2. In this particular scenario, the Node MUST set
Message Hash in CGA-TSIGe. This allows the DNS server to ensure data
integrity without going to the process of message decryption.
In the generation of the CGA-TSIG/CGA-TSIGe for a Resolver, there is
no need to include the IP Tag. This is because the Resolvers do not
usually have several IP addresses so the client does not need to keep
several IP addresses for the same resolver.
5.3.1. Client Verification Process (CGA-TSIGe only)
1. Retrieves Hashing Algorithm From CGA-TSIGe
The resolver retrieves the hashing algorithm from CGA-TSIGe Type
field.
2. Executes Hashing Algorithm on DNS Message
The Resolver computes the SHA algorithm on the whole DNS message. It
compares this with the value obtained from Message Hash of CGA-TSIGe.
If they are the same, it decrypts the message using the shared secret
obtained from the MAC section of the Other DATA section of TSIG
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RRType.
5.3.2. Resolver Verification Process
When a Resolver responds to the client's query request for the first
time, the client saves its Public Key in a file. This allows the
client to verify this Resolver when it changes its IP Address due to
privacy or security concerns. The steps 2 and 3 of the verification
process are the same as those steps explained in section 5.1.1. These
steps are as follows:
1. Verify The Hash of Public Key (IPv4 only)
The client retrieves the SHA Algorithm Type from the Type section of
CGA-TSIG/CGA-TSIGe, concatenates the Resolver's Public Key with the
Resolver's IP address, and computes the SHA algorithm on the result.
The client compares this value with the value in its cache (received
securely from a DHCP server or manually set by client). If they are
the same, it stores its Public Key in its cache, and continues onto
the next step. Otherwise the message will be discarded.
2. Verify The Signature (IPv4 and IPv6)
The Signature contained in CGA-TSIG/CGA-TSIGe DATA can be verified by
retrieving the Public Key and Signature from the CGA-TSIG/CGA-TSIGe
DATA. If the verification process is successful, continue onto step
3, otherwise the message will be discarded.
3. Check The Time Signed (IPv4 and IPv6)
4. Execute The CGA Verification (IPv6 only)
5. Verify The Source IP Address (IPv6 only)
If the Resolver's source IP address is the same as that which is
known for the host or the length of Old Public Key is not zero (0),
then step 6 will be executed. Otherwise the message SHOULD be
discarded without further action.
6. Verify The Public Key (IPv6 only)
The client checks whether or not the Public Key retrieved from
CGA-TSIG/CGA-TSIGe DATA matches any Public Key that was previously
saved in the storage where the Public Key and IP addresses of
Resolvers are saved. If there is a match, then the message is
processed. If not, then step 7 will be executed.
7. Verify The Old Public Key (IPv4 and IPv6)
If the Old Public Key Length is zero (0), discard this message
without further action. If the Old Public Key Length is not zero(0),
then the host will retrieve the Old Public Key from
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CGA-TSIG/CGA-TSIGe DATA and will check whether or not it is the same
as what was saved in the host's storage where the Public Keys and IP
addresses are stored. If it is the same, then step 8 will be
executed.
8. Verify The Old Signature (IPv4 and IPv6)
The Old Signature contained in CGA-TSIG/CGA-TSIGe DATA can be
verified by retrieving the Old Public Key and Old Signature from
CGA-TSIG/CGA-TSIGe DATA and then using this Old Public Key to verify
the Old Signature. If the verification is successful, the DNS Message
should be processed and the New Public Key should be replaced with
the Old Public Key of the Resolver in the host. If the verification
process fails, then the message will be discarded.
5.4. DNS Resolving Scenario (Authoritative NS to Recursive NS)
This verification step of Authoritative Name Server to Recursive Name
Server is the same as that explained in section 5.3.1. In this case
the Recursive Name Server does not need to generate CGA-TSIG DATA,
but the Root Name Server does need to include it in order to enable
the Recursive Name Server to verify it. The Recursive Name Server
needs to include the TSIG RDATA and set the Algorithm Type to
CGA-TSIG. It MUST set the CGA-TSIG Len to zero (0). This allows the
Root Name Server to know when to include CGA-TSIG for verification
process in client.
In case the node needs to use DNS data confidentiality, then it needs
to set the Algorithm Type to CGA-TSIGe and follows the step explained
in section 4.2.2. In this particular scenario, the Node MUST set the
Message Hash in CGA-TSIGe. This allows the DNS server to ensure the
data integrity of this message without going to the process of
message decryption.
6. SeND Is Not Supported (IPv6 only)
In the case where there are no cache parameters available during the
IP Address generation, there are then two scenarios that come into
play here. In the first scenario there is the case where the sender
of a DNS message needs to generate a key pair and generate the
CGA-TSIG or CGA-TSIGe data structure as explained in section 4.1 or
section 4.2. The Node SHOULD skip the first section of the
verification processes explained in section 5.1.1, section 5.2.1, and
section 5.3.1.
In the second scenario, as explained in section 4.1.3 (step 1), it is
not necessary for the server to support the SeND or CGA algorithm.
The DNS administrator can make a one-time use of a CGA script to
generate the CGA parameters and then manually configure the IP
address of the DNS server. Later, the DNS server can use those values
as a means for authenticating other Nodes. The verifier Nodes also do
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not necessarily need to support SeND. They only need to support
CGA-TSIG.
In the third scenario, as explained in section 4.1.4, the Node can
use the same approach used for IPv4 and retrieve the hash of (Public
Key + IPv6 Address) from the DHCPv6 server.
7. CGA-TSIG/CGA-TSIGe Sample Applications
The purpose of CGA-TSIG and CGA-TSIGe is to minimize the human
intervention required to accomplish a shared secret or key exchange,
with the end result of providing data confidentiality to prevent DNS
spoofing. Minimizing the amount of human intervention reduces the
vulnerability to attacks introduced by human errors.
As explained above, CGA-TSIG and CGA-TSIGe can be used in different
scenarios. For the FQDN update scenario, CGA-TSIG is useful in
dynamic networks where the nodes want to change their IP addresses
frequently in order to maintain privacy. If the Dynamic Host
Configuration Protocol (DHCP) is in use, then the DHCP server can do
this update on behalf of the nodes in this network on a DNS server.
But with the Neighbor Discovery Protocol (NDP), there is no feature
available that allows the host security update process for its own
FQDN. In this case, CGA-TSIG can be a solution.
In the Resolver scenario, the Resolver can add the TSIG Resource
Record (RR) to the DNS query response and use the CGA-TSIG/CGA-TSIGe
algorithm to authenticate the result or DNS data protection. CGA-TSIG
assures the client that the query response comes from the true
originator and not from an attacker. CGA-TSIG/CGA-TSIGe also ensures
the integrity/and confidentiality of the data by signing and
encrypting the data.
There are several types of attacks that CGA-TSIG/CGA-TSIGe can
prevent. The use of CGA-TSIG will reduce the number of messages
needed between a client and a server in order to establish a secure
channel. To exchange the shared secret between a DNS Resolver and a
client, when TSIG is used, a minimum of four (4) messages are
required. By modifying [RFC2845] to use CGA-TSIG, this will decrease
the number of messages needed . The messages used in [RFC2930] (TKEY
RR) are not needed when CGA-TSIG is used.
7.1. IP Spoofing
This prevents the attack by finding a binding between the IP address
and the Public Key for both IPv4 and IPv6 , with different
approaches.
7.2. Resolver Configuration Attack
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When using CGA-TSIG/CGA-TSIGe, the DNS server (or client), would not
need further configuration. This reduces the possibility of human
errors being introduced into the DNS configurations. Since this type
of attack is predicated on human error, the chances of it occurring
are minimized.
7.3. Exposing A Shared Secret
Using CGA-TSIG/CGA-TSIGe will decrease the number of manual steps
required in generating the new shared secret and in exchanging it
among the hosts to update the old shared secret. This manual step is
required after a shared secret is leaked.
7.4. Replay Attack
Using the Time Signed value in the Signature modifies the content of
the Signature each time the Node generates and sends it to the DNS
server. If the attacker attempts to spoof the timestamp, the DNS
server will check this message by verifying the signature. In this
case, the verification process will fail preventing the replay
attack.
7.5. Data Confidentiality
Encrypting the whole DNS message will deny the attacker from knowing
the content of DNS messages. This will avoid zone walking and many
other attacks on DNS RRs.
8. Security Considerations
The approach explained in this draft, CGA-TSIG, is a solution for
securing DNS messages from spoofing type attacks like those explained
in section 3.
A problem that may arise here concerns attacks against the CGA
algorithm. In this section we will explain the possibility of such
attacks against CGA [5] and explain the available solutions that we
considered in this draft.
a) Discover an Alternative Key Pair Hashing of the Victim's Node
Address
In this case an attacker would have to find an alternate key pair
hashing of the victim's address. The probability for success of this
type of attack will rely on the security properties of the underlying
hash function, i.e., an attacker will need to break the second
pre-image resistance of that hash function. The attacker will perform
a second pre-image attack on a specific address in order to match
other CGA parameters using Hash1 and Hash2. The cost of doing this is
(2^59+1) * 2^(16*1). If the user uses a sufficient security level, it
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will be not feasible for an attacker to carry out this type of attack
due to the cost involved. Changing the IP address frequently will
also decrease the chance for this type of attack succeeding.
b) DoS to Kill a CGA Node
Sending a valid or invalid CGA signed message with high frequency
across the network can keep the destination node(s) busy with the
verification process. This type of DoS attack is not specific to CGA,
but it can be applied to any request-response protocol. One possible
solution ,to mitigate this attack, is to add a controller to the
verifier side of the process to determine how many messages a node
has received over a certain period of time from a specific node. If a
determined threshold rate is exceeded, then the node will stop
further receipt of incoming messages from that node.
c) CGA Privacy Implication
Due to the high computational complexity necessary for the creation
of a CGA, it is likely that once a node generates an acceptable CGA
it will continue its use at that subnet. The result is that nodes
using CGAs are still susceptible to privacy related attacks. One
solution to these types of attacks is setting a lifetime for the
address as explained in RFC 4941.
9. IANA Considerations
The IANA has allowed for choosing new algorithm(s) for use in the
TSIG Algorithm name. Algorithm name refers to the algorithm described
in this document. The requirement to have this name registered with
IANA is specified.
In section 4.1, Type should allow for the use of future optional
algorithms with regard to SeND. The default value for CGA might be 1.
Other algorithms would be assigned a new number sequentially. For
example, a new algorithm called SSAS [4,5] could be assigned a value
of 2.
IANA also needs to define a numeric algorithm number for ECC. The
similar way that is defined for RSA.
10. Appendix
10.1. A Sample Key Storage For CGA-TSIG
create table cgatsigkeys (
id INT auto_increment,
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pubkey VARCHAR(300),
primary key(id)
);
create table cgatsigips (
id INT auto_increment,
idkey INT,
IP VARCHAR(20),
FOREIGN KEY (idkey) REFERENCES cgatsigkeys(id)
primary key(id)
);
CGA-TSIG tables on mysql backend database
10.2. Stored parameters in the node
Here is a sample format of stored parameters in the node. For
example, the modifier is stored as bytes and each byte might be
separated by a comma (for example : 284,25,14,...). Algorithmtype is
the algorithm used in signing the message. Zero is the default
algorithm for RSA. Secval is the CGA Sec value that is, by default,
one. GIP is the global IP address of this node (for example:
2001:abc:def:1234:567:89a). oGIP is the old IP address of this node,
before the generation of the new IP address. Keys contains the path
where the CGA-TSIG algorithm can find the PEM format used for the
public/private keys (for example: /home/myuser/keys.pem ).
<?xml version="1.0" encoding="UTF-8"?>
<Details>
<CGATSIG>
<modifier value=""/>
<algorithmtype value="1.2.840.113549.1.1.1"/>
<secval value="1"/>
<GIP value=""/>
<oGIP value=""/>
<Keys value=""/>
</CGATSIG>
</Details>
XML file contains the cached DATA
10.3. CGA Generation Script
Here introduces a sample CGA generation script for the nodes that
does not support SeND.
byte[] modifier;
typedef int bool;
#define true 1
#define false 0
// length_of_digest : 8 leftmost bytes of digest.
//this function sets sec value on the first byte of digest
//since interface ID is only 8 bytes, it returns only 8 leftmost bytes of digest
byte[] set_secvalue(byte[] digest,int length_of_digest);
//this function compares the 16 by cga_sec_value bits of digest to zero
bool compare(byte[] digest, int cga_sec_value);
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//this function executes hashing function on cga_parameters
byte[] sha1(byte[] cga_parameters);
//this function reads public key from a file
byte[] read_public_key(char[] public_key_path);
//this function increments the modifier by one
increment(byte[] modifier);
//this function concatenates the input values.
byte[] concat(byte[], byte[],....);
//Write in a file
CacheCGAparameters(byte[] ipv6_address, byte[] modifier, char[]
public_key_path, int cga_sec_value, byte[] public_key_algorithm);
//--------------main function ------------------------
int main(char[] interface_name)
{
byte[] cga=cgagen("\\xxx\key.pub",prefix);
byte[] ipv6_address=concat(prefix,cga);
//set the CGA address on a desired interface
setIP(ipv6_address,"eth0\0");
CacheCGAparameters(ipv6_address,modifier,public_key_path, cga_sec_value,
'1.2.840.113549.1.1.1');
}
//------------------sample function for CGA Generation--------------
byte[] cgagen(char[] public_key_path, byte[] prefix, int cga_sec_value)
{
bool flag=true;
byte[] cga;
byte[] public_key=read_public_key(public_key_path);
modifier= randomnumber(16);
while(flag)
{
//concatinate all values
byte[] cgaparameters=concat(modifier,prefix,0,public_key);
byte[] digest=sha1(cgaparameters);
if(compare(digest,cga_sec_value)==false)
increment(modifier);
else
flag=false;
}
cga=set_secvalue(digest,8);
return cga;
}
//-------------Sample function for random number generator----
//random generator explained in ra_privacy draft
byte[] randomnumber(int length_byte)
{
byte[] num=new byte[length_byte];
srand(time(NULL));
for(int i=0;i<length_byte;i++)
num[i]=rand() %254;
}
11. Acknowledgements
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The continual improvement of this document is as a result of the
helps and assistance of its supporters.
The authors would like to thank all those people who directly helped
in improving this draft and all supporters of this draft, especially
Ralph Droms, Andrew Sullivan, Ted Lemon, Brian Haberman, Erik
Nordmark, Brian Dickson. The authors would like also to special
acknowledge the supports of NLnet Labs director and researchers; Olaf
Kolkman, Matthijs Mekking and their master student Marc Buijsman.
The authors would like to express their special appreciation and
thanks to Tim Wicinski who spent a lot of time to review, revise and
improve this draft.
12. References
12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to
Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3972] Aura, T., "Cryptographically Generated Addresses
(CGA)," RFC 3972, March 2005.
[RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander,
"SEcure Neighbor Discovery (SEND)", RFC 3971, March 2005.
[RFC2119] Bradner, S., "Key words for use in RFCs to
Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2930] Eastlake 3rd, D., "Secret Key Establishment for
DNS (TKEY RR)", RFC 2930, September 2000.
[RFC1035] Mockapetris, P., "Domain Names - Implementation
And Specification", RFC 1035, November 1987.
[RFC4941] Narten, T., Draves, R., Krishnan, S., "Privacy
Extensions for Stateless Address Autoconfiguration in
IPv6", RFC 4941, September 2007.
[RFC2136] Vixie, P. (Editor), Thomson, S., Rekhter, Y.,
Bound, J., "Dynamic Updates in the Domain Name System (DNS
UPDATE)", RFC 2136, April 1997.
[RFC2845] Vixie, P., Gudmundsson, O. , Eastlake 3rd, D.,
Wellington, B., " Secret Key Transaction Authentication for
DNS (TSIG)", RFC 2845, May 2000.
[RFC6106] Jeong, J., Park, S., Beloeil, L., Madanapalli,
S.,"IPv6 Router Advertisement Options for DNS
Configuration",RFC 6106, November 2010.
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[RFC4086] Eastlake, D., Schiller, J., and Crocker, D.,
"Randomness Requirements for Security", BCP 106, RFC
4086,June 2005.
[RFC4055] Schaad, J., Kaliski, B., and Housley, R.,
"Additional Algorithms and Identifiers for RSA Cryptography
for use in the Internet X.509 Public Key infrastructure
Certificate and Certificate Revocation List (CRL) Profile",
RFC 4055,June 2005.
[RFC6840] Weiler, S. and Blacka, D., "Clarifications and
Implementation Notes for DNS Security (DNSSEC)", RFC
6840,February 2013.
[RFC3757] Kolkman, O., Schlyter, J., and Lewis, E., "Domain
Name System KEY (DNSKEY) Resource Record (RR) Secure Entry
Point (SEP) Flag",RFC 3757,April 2004.
12.2. Informative References
[1] Aura, T., "Cryptographically Generated Addresses (CGA)",
Lecture Notes in Computer Science, Springer, vol. 2851/2003, pp.
29-43, 2003.
[2] Montenegro, G. and Castelluccia, C., "Statistically Unique
and Cryptographically Verifiable (SUCV) Identifiers and
Addresses," ISOC Symposium on Network and Distributed System
Security (NDSS 2002), the Internet Society, 2002.
[3] AlSa'deh, A., Rafiee, H., Meinel, C., "IPv6 Stateless Address
Autoconfiguration: Balancing Between Security, Privacy and
Usability". Lecture Notes in Computer Science, Springer(5th
International Symposium on Foundations & Practice of Security
(FPS). October 25 - 26, 2012 Montreal, QC, Canada), 2012.
[4] Rafiee, H., Meinel, C., "A Simple Secure Addressing
Generation Scheme for IPv6 AutoConfiguration (SSAS)". Work in
progress, http://tools.ietf.org/html/draft-rafiee-6man-ssas,
2013.
[5] Rafiee, H., Meinel, C., "A Simple Secure Addressing Scheme
for IPv6 AutoConfiguration (SSAS)", 11th International conference
on Privacy, Security and Trust (IEEE PST), 2013.
[6] AlSa'deh, A., Rafiee, H., Meinel, C., "Cryptographically
Generated Addresses (CGAs): Possible Attacks and Proposed
Mitigation Approaches," in proceedings of 12th IEEE International
Conference on Computer and Information Technology (IEEE CIT'12),
pp.332-339, 2012.
[7] Rafiee, H., Meinel, C., "A Secure, Flexible Framework for DNS
Authentication in IPv6 Autoconfiguration" in proceedings of The
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12th IEEE International Symposium on Network Computing and
Applications (IEEE NCA13), 2013.
[savi-dhcp] Bi, J., Wu, J., Yao, G, Baker, F.,"SAVI
Solution for DHCP",
http://tools.ietf.org/html/draft-ietf-savi-dhcp-23, April
2014
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Authors' Addresses
Hosnieh Rafiee
http://www.rozanak.com
Phone: +49 176 57 58 75 75
Email: ietf@rozanak.com
Christoph Meinel
Hasso-Plattner-Institute
Prof.-Dr.-Helmert-Str. 2-3
Potsdam, Germany
Email: meinel@hpi.uni-potsdam.de
Martin von Loewis
Hasso-Plattner-Institute
Prof.-Dr.-Helmert-Str. 2-3
Potsdam, Germany
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