Transaction SIGnature (TSIG) using CGA Algorithm in IPv6
draft-rafiee-intarea-cga-tsig-03
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".
|
|
|---|---|---|---|
| Authors | Hosnieh Rafiee , Martin von Loewis , Christoph Meinel | ||
| Last updated | 2013-07-08 | ||
| 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) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-rafiee-intarea-cga-tsig-03
DNS Extensions H. Rafiee
INTERNET-DRAFT M. v. Loewis
Updates RFC 2845 (if approved) C. Meinel
Intended Status: Standards Track Hasso Plattner Institute
Expires: January 8, 2014 July 8, 2013
Transaction SIGnature (TSIG) using CGA Algorithm in IPv6
draft-rafiee-intarea-cga-tsig-03.txt
Abstract
The first step in the Transaction SIGnature (TSIG) (RFC 2845) process
is the generation of a shared secret to be used between a DNS server
and a host. The second step consists of modifying the DNS
configuration so that the DNS server will know what key to use with
which host, because this shared secret is only valid between a pair
of hosts. This document, CGA-TSIG, proposes a possible way to
eliminate the human intervention needed for the generation and
exchange of keys between a DNS server and a host when SEcure Neighbor
Discovery (SEND) (RFC 3971) is used. CGA-TSIG will facilitate the
authentication process of a host with a DNS server and will reduce
the time needed to accomplish DNS Updates. It will also provide a
means for securing the authentication process between resolvers and
clients. CGA-TSIG will be added, as an extension, to TSIG in order to
provide data integrity and proof of IP address ownership. The current
signature generation and verification process used in TSIG will be
substituted with the use of the same parameters as are used in
generating a secure address in IPv6 networks, i.e., Cryptographically
Generated Addresses (CGA) (RFC 3972).
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 January 8, 2014.
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Copyright Notice
Copyright (c) 2012 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
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 . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions used in this document . . . . . . . . . . . . . . 3
3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3
3.1. IP Spoofing . . . . . . . . . . . . . . . . . . . . . . 5
3.2. DNS Dynamic Update Spoofing . . . . . . . . . . . . . . . 5
3.3. Resolver Configuration Attack . . . . . . . . . . . . . . 5
3.4. Exposing Shared Secret (key pairs) . . . . . . . . . . . 5
3.5. Replay attack . . . . . . . . . . . . . . . . . . . . . . 5
4. Algorithm Overview . . . . . . . . . . . . . . . . . . . . . 6
4.1. The CGA-TSIG DATA structure . . . . . . . . . . . . . . 6
4.2. Generation of CGA-TSIG DATA . . . . . . . . . . . . . . . 8
5. DNS Update communication . . . . . . . . . . . . . . . . . . 9
5.1. Verification process . . . . . . . . . . . . . . . . . . 10
6. Stub to resolver communication . . . . . . . . . . . . . . . 11
6.1. Verification process . . . . . . . . . . . . . . . . . . 11
7. DNS server to DNS server communication (zone transfer) . . . 12
7.1. Verification Process . . . . . . . . . . . . . . . . . . 13
8. No cache parameters available . . . . . . . . . . . . . . . . 14
9. Security Considerations . . . . . . . . . . . . . . . . . . . 14
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
11. Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . 15
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
13.1. Normative . . . . . . . . . . . . . . . . . . . . . . . . 17
13.2. Informative . . . . . . . . . . . . . . . . . . . . . . . 17
13.3. Informative . . . . . . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19
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1. Introduction
Transaction SIGnature (TSIG) [RFC2845] is a protocol that provides
endpoint authentication and data integrity by the use of one-way
hashing and shared secret keys in order to establish a trust
relationship between two hosts which can be either a client and a
server, or two servers. The TSIG keys, which are manually exchanged
between these two hosts, need to be maintained in a secure manner.
This protocol is today mostly used to secure a Dynamic Update, or to
give assurance to the slave name server, that the zone transfer is
from the original master name server and that it has not been spoofed
by hackers. It does this by verifying the signature using a
cryptographic key that is shared with the receiver.
It is possible to extend the TSIG protocol with the use of newly
defined algorithms. This document proposes to use Cryptographically
Generated Addresses (CGA) [RFC3972] 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 and its IP address without the need for the
introduction of a new infrastructure. CGA is a one-way hashing
algorithm used to generate Interface IDs for IPv6 addresses in a
secure manner. An interface ID consists of the rightmost 64 bits of
the 128 bit IPv6 address. CGA verifies the ownership of the sender's
IP address by finding a relationship between the sender's IP address
and his public key [1,2].
+------------------------------------------------+
| Subnet Prefix | Interface ID |
| (8 octets) | (8 octets) |
+------------------------------------------------+
Figure 1 IPv6 addresses
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.
3. Problem Statement
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This document addresses the authentication problems associated with
the need for hosts to change their IP addresses frequently in order
to maintain privacy. This problem presents itself in three different
scenarios: the authentication of a resolver with a client (stub), the
authentication of two hosts (a client and a DNS server) during the
DNS Update process, and the authentication of two DNS servers during
the zone transfer. The focus of this document is on the first two
problems, but it can also offer a possible solution to the third
problem.
The DNS Update process is vulnerable to several types of spoofing
attacks -- man in the middle, reflector , source IP spoofing, etc.
TSIG secures this process by providing the transaction level
authentication necessary by use of a shared secret. The current
problem with using TSIG is the need for the manual processing that is
required to generate and exchange the shared secrets. For each paired
host there needs to be one shared secret and the administrator needs
to manually add it to the DNS configuration file for each of these
hosts. So, whenever these two hosts change their IP addresses,
because of privacy issues as explained in RFC 4941 [RFC4941] or when
moving to another subnet within the same network, this manual process
will need to be invoked. The purpose of CGA-TSIG [7] is to minimize
the amount of human intervention required to accomplish this exchange
and, as a byproduct, to reduce the process's vulnerability to attacks
introduced by human errors when SEcure Neighbor Discovery (SEND) is
used for addressing purposes.
This same problem exists between a client and a DNS resolver. When a
client sends a DNS query to a resolver, an attacker can send a
response to this client containing the spoofed source IP address of
this resolver. The client checks the resolver's source IP address for
authentication. If the attacker spoofed the resolver's IP address,
and if the attacker responds faster than the legitimate resolver,
then the client's cache will be updated with the attacker's response.
The client does not have any way to authenticate the resolver. In the
above scenario, the resolver could add the TSIG Resource Record (RR)
to the DNS query response and use the CGA-TSIG algorithm in order to
permit a useful authentication of the result. CGA-TSIG assures the
client that the query response comes from the true originator and not
from an attacker. 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. A second reason is that the manual TSIG process makes it
difficult to configure each new client with the shared secret of the
resolver.
There are several types of attack that CGA-TSIG can prevent. Here we
will evaluate some of them. The use of CGA-TSIG will also reduce the
number of messages needed in exchange 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 messages are required for the establishment of a secure channel.
Modifying RFC 2845 to use CGA-TSIG will decrease the number of
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messages needed in the exchange. The messages used in RFC 2930 (TKEY
RR) are not needed when CGA-TSIG is used.
3.1. IP Spoofing
During the DNS Update process it is important that both communicating
parties know that the one that they are communicating with is the
actual owner of that IP address and that the messages are not being
sent from a spoofed IP address. This can be accomplished by the use
of the CGA algorithm which utilizes the node for IP address
verification of other nodes.
3.2. DNS Dynamic Update Spoofing
Dynamic Update Spoofing is eliminated because the signature contains
both the CGA parameters and the DNS update message. This will offer
proof of the sender's IP address ownership (CGA parameters) and the
validity of the update message.
3.3. Resolver Configuration Attack
When using CGA-TSIG, the DNS server, or the client, would not need
further configuration. This would reduce the possibility of human
errors being introduced into the DNS configuration file. Since this
type of attack is predicated on human error, the chances of it
occurring, when this extension is used, are minimized.
3.4. Exposing Shared Secret (key pairs)
In order to decrease the chances of attackers gaining unauthorized
access to private keys on a node, it is recommended that key pairs be
generated "on-the-fly".
3.5. 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 tries to spoof this value with another
timestamp, to show that the update message is current, the DNS server
checks this message by verifying the signature. In this case, the
verification process will fail thus also preventing the replay
attack.
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4. Algorithm Overview
The following sections explain the use of CGA for securing the DNS
process by adding a CGA-TSIG data structure to the TSIG Resource
Record (RR).
4.1. 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 2
and 3). The DNS RRTYPE must be set to TSIG [RFC2845]. The RDATA
Algorithm Name MUST be set to CGA-TSIG. A detailed explanation of the
standard RDATA fields can be found in section 2.3 RFC 2845. 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. If
another algorithm is used in place of CGA for SeND, such as SSAS [4 ,
5], then the CGA-TSIG Len will be the length for the parameters of
this algorithm and CGA-TSIG DATA will consist of the parameters
required for verification of that algorithm, like signature, public
key, etc.
+---------------------------------------+
| Algorithm Name |
| (CGA-TSIG) |
+---------------------------------------+
| Time Signed |
| |
+---------------------------------------+
| Fudge |
| |
+---------------------------------------+
| MAC Size |
| |
+---------------------------------------+
| Mac |
| |
+---------------------------------------+
| Original ID |
| |
+---------------------------------------+
| Error |
| |
+---------------------------------------+
| OTHER LEN |
| |
+---------------------------------------+
| OTHER DATA |
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| |
+---------------------------------------+
Figure 2 Modified TSIG RDATA
The CGA-TSIG DATA Field and the CGA-TSIG Len will occupy the first
two slots of Other DATA. Figure 3 shows the layout.
+---------------------------------------+
| CGA-TSIG Len |
| |
+---------------------------------------+
| CGA-TSIG DATA |
| |
+---------------------------------------+
| Other Options |
| |
+---------------------------------------+
Figure 3 Other DATA section of RDATA field
CGA-TSIG DATA Field Name Data Type Notes
--------------------------------------------------------------
Algorithm type u_int16_t Name of the algorithm
[RFC3972] RSA (by default) CGA
type u_int16_t Name of the algorithm used in
SEND
IP tag 16 octet the tag used to identify the IP
address
Parameters Len Octet the length of CGA parameters
Parameters variable CGA parameters Section 3 RFC 3972
Signature Len Octet the length of CGA signature
Signature variable Section 3.2.1 This document
old pubkey Len variable the length of old public key
field
old pubkey variable Old public key
old Signature Len variable the length of old signature field
old Signature variable Old signature generated by old
public key.
Type indicates the Interface ID generation algorithm that was used in
SeND. This field allows for the use of future, optional algorithms in
SeND. The default value for CGA is 1. The IP tag is a node's old IP
address. A client's public key can be associated with several IP
addresses on a server. The DNS server, or the DNS message verifier
node, SHOULD store the IP addresses and the public keys so as to
indicate their association to each other. If a client wants to add
RRs to the server by using a new IP address, then the IP tag field
will be set to binary zeros. The server will then store the new IP
address that was passed to it in storage. If the client wants to
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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 in its storage and replace that IP address 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 in order to
maintain privacy, then it MUST add the old public key to the old
pubkey field. It MUST also retrieve the current time from Time Signed
field, sign it using the old private key, and then add the digest
(signature) to the old signature field. This enables the verifier
node to authenticate a host with a new public key. The detailed
verification steps are explained in sections 5.1, 6.1 and 7.1.
4.2. 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 cache, please see section 8. If the Type
(section 4.1) 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 this host generated by the use of CGA.
1.Obtain required parameters from cache.
The CGA-TSIG algorithm obtains the old IP address, modifier, subnet
prefix, and public key from cache. It concatenates the old IP address
with the CGA parameters, i.e., modifier, subnet prefix, public key
and collision count (the order of CGA parameters are shown in section
3 RFC 3972). If the old IP address is not available, then CGA-TSIG
must set the old IP address (IP tag) to zero.
2. Generate signature
For signature generation, all CGA parameters (modifier, public key,
collision count and subnet prefix), that are concatenated with the
DNS update message, the IP tag and the Time Signed field, are signed
by using a RSA algorithm, the default, or any future algorithm used
in place of RSA, and the private key which was obtained from cache in
the first step. This signature must be added to the signature field
of the CGA-TSIG DATA. Time Signed is the same timestamp as is used in
RDATA. This value is the number of seconds since 1 January 1970 in
UTC obtained from the signature generator. This approach will prevent
replay attacks by changing the content of the signature each time a
node wants to send a DNS message. The format of DNS messages is
explained in section 4.1.2 RFC 1035 [RFC1035].
+---------------------------------------+
| Algorithm Name |
| |
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+---------------------------------------+
| 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) |
+---------------------------------------+
Figure 4 CGA-TSIG DATA Field
3. Generate old signature
If the nodes generated new key pairs, then they need to add the old
public key and message, signed by the old private key, to CGA-TSIG
DATA. A node will retrieve the timestamp from Time Signed, will use
the old private key to sign it, and then will add the content 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.
5. DNS Update communication
This section discusses the use of CGA-TSIG for the authentication of
a host in a DNS server. In this case, the messages sent from a host
will need to contain the CGA-TSIG option.
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5.1. 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 executes the following
steps:
1. Execute the CGA verification
These steps are found in section 5 RFC 3972. 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 2 will be executed. Otherwise the
message will be discarded without further action.
2. Check the Time Signed
The Time Signed value is obtained from TSIG RDATA and is called t1.
The current system time is then obtained and converted to UTC time
and is called t2. If t1 is in the range of t2 and t2 minus x minutes
(see formula 1, x minutes may vary according to transmission lag
time) then step 3 will be executed. Otherwise, the message will be
considered a spoofed message and the message should be discarded
without further action. 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.
t2-x <= t1 <= t2 (1)
3. Verify the signature
The signature contained in CGA-TSIG DATA should be verified. This can
be done by retrieving the public key and signature from CGA-TSIG DATA
and using this public key to verify the signature. If the
verification process is successful, then step 4 will be executed. If
the verification fails, then the message should be discarded without
further action.
4. Verify the public key
The DNS server checks whether or not the public key retrieved from
CGA-TSIG DATA is the same as what was available in the storage where
the public keys and IP addresses were saved. If no entry is found for
this public key in storage, then the DNS server adds this public key
to its storage and processes the Update Message. If it is available,
and it is the same as what is in storage, then the Update Message
should be processed. Otherwise step 5 will be executed.
5. Verify the old public key
If the old public key length is zero, then skip this step and discard
the DNS update message without further action. If the old public key
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length is not zero, then the DNS server will retrieve the old public
key from CGA-TSIG DATA and will check to see whether or not it is the
same as what was saved in the DNS server's storage where the public
keys and IP addresses are stored. If it is the same, then step 6 will
be executed, otherwise the message should be discarded without
further action.
6. Verify the old signature
The old signature contained in CGA-TSIG DATA should be verified. This
can be done by retrieving the old public key and the old signature
from CGA-TSIG DATA and then using this old public key to verify the
old signature. If the verification is successful, then 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, then the message should be discarded without further
action.
6. Stub to resolver communication
A DNS query request sent by a host, such as a client or a mail
server, does not need to include CGA-TSIG DATA because the resolver
responds to anonymous queries. But the resolver's response SHOULD
contain the CGA-TSIG DATA field in order to enable this client to
verify him.
In generation of the CGA-TSIG for a resolver, there is no need to
include the IP tag. This is because resolvers don't usually have
several IP addresses so the client does not need to keep several IP
addresses for the same resolver.
6.1. Verification process
When a resolver responds to the host'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 first 2 steps of the verification
process are the same as those steps explained in section 5.1 These
steps are as follows:
1. Execute the CGA verification
2. Check the Time Signed
3. Verify the Source IP address
If the resolver's source IP address is the same as that which is
known for the host, then step 4 will be executed. Otherwise the
message SHOULD be discarded without further action.
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4. Verify the signature
The signature contained in CGA-TSIG DATA should be verified. This can
be done by retrieving the public key and signature from CGA-TSIG DATA
and using this public key to verify the signature. If the
verification process is successful, then step 5 will be executed. If
the verification fails, then the message should be discarded without
further action.
5. Verify the public key
The host checks whether or not the public key retrieved from CGA-TSIG
DATA matches any public key that was previously saved in the storage
where the public keys and IP addresses of resolvers are saved. If
there is a match, then the message is processed. If not, then step 5
will be executed.
5. Verify the old public key
If the old public key length is zero, then skip this step and discard
the DNS query response without further action. If the old public key
length is not zero, then the host will retrieve the old public key
from CGA-TSIG 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 6 will be
executed, otherwise the message should be discarded without further
action.
6. Verify the old signature
The old signature contained in CGA-TSIG DATA should be verified. This
can be done by retrieving the old public key and old signature from
CGA-TSIG DATA and then using this old public key to verify the old
signature. If the verification is successful, then 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 should be discarded without further
action.
7. DNS server to DNS server communication (zone transfer)
In the case of processing a DNS update for multiple DNS servers
(authentication of two DNS servers), there are two 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
because of the need for human intervention.
a. Add the DNS servers' IP address to a slave configuration file
A DNS server administrator should only manually add the IP address of
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the master DNS server to the configuration file of the slave DNS
server. When the DNS update message is processed, the slave DNS
server can authenticate the master DNS server based on the source IP
address and then, prove the ownership of this address by use of the
CGA-TSIG option from the TSIG RR. This scenario will be valid until
the IP address in any of these DNS servers changes.
To automate this step's process, the DNS Update message sender's
public key 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)
The message exchange option of SEND [RFC3971] may be used for the
retrieval of the third party certificate. This may be done
automatically from the TA by using the Certificate Path Solicitation
and the Certificate Path Advertisement messages. Like in scenario b,
the certificate should be saved on the DNS server for later use for
the generation of its address or for the DNS update process. In this
case, whenever any of these servers want to generate a new IP
address, then the DNS update process can be accomplished
automatically without the need for human intervention.
7.1. Verification Process
The verification steps are the same as those is explained in section
5.1, but with one additional step.
1- Execute the CGA verification
2- Check the Time Signed
3- Verify the signature
4- Verify the source IP address
The source IP address of the Update requester MUST be checked against
the one contained in the DNS configuration file. If it is the same,
then the Update Message should be processed, otherwise, step 5 will
be executed.
5- Verify the public key
6- Verify the old public key
7- Verify the old signature
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8. No cache parameters available
In a case where there are no cache parameters available during the IP
address generation, the sender of DNS message needs to generate a key
pair and generate the CGA-TSIG data structure as explained in section
4. The node SHOULD skip the first section of verification processes
explained in section 5.1 , section 6.1 and section 7.1.
9. 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
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
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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.
10. 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.
11. Appendix
- A sample key storage for CGA-TSIG
create table cgatsigkeys (
id INT auto_increment,
pubkey VARCHAR(300),
primary key(id)
);
create table cgatsigips (
id INT auto_increment,
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idkey INT,
IP VARCHAR(20),
FOREIGN KEY (idkey) REFERENCES cgatsigkeys(id)
primary key(id)
);
CGA-TSIG tables on mysql backend database
- 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="0"/>
<secval value="1"/>
<GIP value=""/>
<oGIP value=""/>
<Keys value=""/>
</CGATSIG>
</Details>
XML file contains the cached DATA
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12. Acknowledgements
The author 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 and Brian Haberman.
13. References
13.1. 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.
13.2. Informative References
[RFC2845] Vixie, P., Gudmundsson, O. , Eastlake 3rd, D.,
Wellington, B., " Secret Key Transaction Authentication for
DNS (TSIG)", RFC 2845, May 2000.
13.3. 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
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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
12th IEEE International Symposium on Network Computing and
Applications (IEEE NCA13), 2013.
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Authors' Addresses
Hosnieh Rafiee
Hasso-Plattner-Institute
Prof.-Dr.-Helmert-Str. 2-3
Potsdam, Germany
Phone: +49 (0)331-5509-546
Email: ietf@rozanak.com
Dr. Christoph Meinel
(Professor)
Hasso-Plattner-Institute
Prof.-Dr.-Helmert-Str. 2-3
Potsdam, Germany
Email: meinel@hpi.uni-potsdam.de
Dr. Martin von Loewis
(Professor)
Hasso-Plattner-Institute
Prof.-Dr.-Helmert-Str. 2-3
Potsdam, Germany
Email: martin@v.loewis.de
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