--- 1/draft-ietf-dhc-sedhcpv6-13.txt 2016-10-09 01:15:57.222374406 -0700 +++ 2/draft-ietf-dhc-sedhcpv6-14.txt 2016-10-09 01:15:57.278375907 -0700 @@ -1,124 +1,127 @@ DHC Working Group S. Jiang Internet-Draft Huawei Technologies Co., Ltd Intended status: Standards Track L. Li -Expires: January 9, 2017 Y. Cui +Expires: April 11, 2017 Y. Cui Tsinghua University T. Jinmei Infoblox Inc. T. Lemon Nominum, Inc. D. Zhang - July 8, 2016 + October 8, 2016 Secure DHCPv6 - draft-ietf-dhc-sedhcpv6-13 + draft-ietf-dhc-sedhcpv6-14 Abstract DHCPv6 includes no deployable security mechanism that can protect end-to-end communication between DHCP clients and servers. This memo describes a mechanism for using public key cryptography to provide such security. The mechanism provides encryption in all cases, and can be used for authentication based either on pre-sharing of - authorized certificates, or else using trust-on-first-use. + authorized certificates. 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 9, 2017. + This Internet-Draft will expire on April 11, 2017. Copyright Notice Copyright (c) 2016 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 . . . . . . . . . . . . . . . . . . . . . . . . 2 + 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Requirements Language and Terminology . . . . . . . . . . . . 3 - 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 + 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Security Issues of DHCPv6 . . . . . . . . . . . . . . . . . . 4 5. Secure DHCPv6 Overview . . . . . . . . . . . . . . . . . . . 5 5.1. Solution Overview . . . . . . . . . . . . . . . . . . . . 5 5.2. New Components . . . . . . . . . . . . . . . . . . . . . 6 - 5.3. Support for Algorithm Agility . . . . . . . . . . . . . . 6 - 5.4. Applicability . . . . . . . . . . . . . . . . . . . . . . 7 + 5.3. Support for Algorithm Agility . . . . . . . . . . . . . . 7 + 5.4. Caused change to RFC3315 . . . . . . . . . . . . . . . . 7 + 5.5. Applicability . . . . . . . . . . . . . . . . . . . . . . 8 6. DHCPv6 Client Behavior . . . . . . . . . . . . . . . . . . . 8 - 7. DHCPv6 Server Behavior . . . . . . . . . . . . . . . . . . . 11 - 8. Relay Agent Behavior . . . . . . . . . . . . . . . . . . . . 13 - 9. Extensions for Secure DHCPv6 . . . . . . . . . . . . . . . . 14 - 9.1. New DHCPv6 Options . . . . . . . . . . . . . . . . . . . 14 - 9.1.1. Certificate Option . . . . . . . . . . . . . . . . . 14 - 9.1.2. Signature option . . . . . . . . . . . . . . . . . . 15 - 9.1.3. Increasing-number Option . . . . . . . . . . . . . . 17 - 9.1.4. Encrypted-message Option . . . . . . . . . . . . . . 17 - 9.2. New DHCPv6 Messages . . . . . . . . . . . . . . . . . . . 18 - 9.3. Status Codes . . . . . . . . . . . . . . . . . . . . . . 18 - 10. Security Considerations . . . . . . . . . . . . . . . . . . . 19 - 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 - 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 21 - 13. Change log [RFC Editor: Please remove] . . . . . . . . . . . 21 - 14. Open Issues [RFC Editor: Please remove] . . . . . . . . . . . 23 - 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 23 - 15.1. Normative References . . . . . . . . . . . . . . . . . . 23 - 15.2. Informative References . . . . . . . . . . . . . . . . . 25 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25 + 7. DHCPv6 Server Behavior . . . . . . . . . . . . . . . . . . . 12 + 8. Relay Agent Behavior . . . . . . . . . . . . . . . . . . . . 14 + 9. Processing Rules . . . . . . . . . . . . . . . . . . . . . . 14 + 9.1. Increasing Number Check . . . . . . . . . . . . . . . . . 14 + 10. Extensions for Secure DHCPv6 . . . . . . . . . . . . . . . . 15 + 10.1. New DHCPv6 Options . . . . . . . . . . . . . . . . . . . 15 + 10.1.1. Certificate Option . . . . . . . . . . . . . . . . . 15 + 10.1.2. Signature option . . . . . . . . . . . . . . . . . . 16 + 10.1.3. Increasing-number Option . . . . . . . . . . . . . . 18 + 10.1.4. Encrypted-message Option . . . . . . . . . . . . . . 18 + 10.2. New DHCPv6 Messages . . . . . . . . . . . . . . . . . . 19 + 10.3. Status Codes . . . . . . . . . . . . . . . . . . . . . . 19 + 11. Security Considerations . . . . . . . . . . . . . . . . . . . 20 + 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 + 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 22 + 14. Change log [RFC Editor: Please remove] . . . . . . . . . . . 22 + 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 24 + 15.1. Normative References . . . . . . . . . . . . . . . . . . 24 + 15.2. Informative References . . . . . . . . . . . . . . . . . 26 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26 1. Introduction The Dynamic Host Configuration Protocol for IPv6 (DHCPv6, [RFC3315]) allows DHCPv6 servers to flexibly provide addressing and other configuration information relating to local network infrastructure to DHCP clients. The protocol provides no deployable security mechanism, and consequently is vulnerable to various attacks. This document provides a brief summary of the security vulnerabilities of the DHCPv6 protocol and then describes a new extension to the protocol that provides two additional types of security: o authentication of the DHCPv6 client and the DHCPv6 server to defend against active attacks, such as spoofing. o encryption between the DHCPv6 client and the DHCPv6 server in - order to protect the DHCPv6 from pervasive monitoring. + order to protect the DHCPv6 communication from pervasive + monitoring. The extension specified in this document applies only to end-to-end communication between DHCP servers and clients. Options added by relay agents in Relay-Forward messages, and options other than the client message in Relay-Reply messages sent by DHCP servers, are not protected. Such communications are already protected using the - mechanism described described in section 21.1 in [RFC3315]. + mechanism described in section 21.1 in [RFC3315]. This extension introduces two new DHCPv6 messages: the Encrypted- Query and the Encrypted-Response messages. It defines four new DHCPv6 options: the Certificate, the Signature, the Increasing- number, and the Encrypted-message options. The Certificate, Signature, and Increasing-number options are used for authentication. The Encryption-Query message, Encryption-Response message and Encrypted-message option are used for encryption. 2. Requirements Language and Terminology @@ -203,21 +206,21 @@ particular link, the client will be unable to communicate with a DHCP server. If the client chooses to communicate with a server, it uses the Encrypted-Query message to encapsulate its communications to the DHCP server. The server responds with Encrypted-Response messages. Normal DHCP messages are encapsulated in these two new messages using the new defined Encrypted-message option. Besides the Encrypted- message option, the Signature option is defined to verify the integrity of the DHCPv6 messages and then authentication of client - and server. The Increasing number is defined to detect replay + and server. The Increasing number option is defined to detect replay attack. +-------------+ +-------------+ |DHCPv6 Client| |DHCPv6 Server| +-------------+ +-------------+ | Information-request | |----------------------------------------->| | Option Request option | | | | Reply | @@ -248,242 +251,234 @@ private key pair and then obtain a certificate that signs the public key. The Certificate option is defined to carry the certificate of the sender. o A signature generated using the private key which is used by the receiver to verify the integrity of the DHCPv6 messages and then authentication of the client/server. The Signature option is defined to carry the signature. o A Increasing-number that can be used to detect replayed packet. - The Increasing-number option is defined to carry a strictly- - increasing serial number. Timestamp is one of the possible - implementation choice. + The Timestamp is one of the possible implementation choices. The + Increasing-number option is defined to carry a strictly-increasing + serial number. o The Encrypted-message option that contains the encrypted DHCPv6 message. o The Encrypted-Query message that is sent from the secure DHCPv6 client to the secure DHCPv6 server. The Encrypted-Query message MUST contain the Encrypted-message option. In addition, the Server Identifier option MUST be contained if it is contained in the original DHCPv6 message. The Encrypted-Query message MUST NOT - contain other options except the Server Identifier option and - Encrypted-message option. + contain other options except the above options. o The Encrypted-Response message that is sent from the secure DHCPv6 server to the secure DHCPv6 client. The Encrypted-Response - message contains the Encrypted-message option. The Encrypted- - Response message MUST NOT contain other options except Encrypted- - message option. + message MUST contain the Encrypted-message option. The Encrypted- + Response message MUST NOT contain any other options except it. 5.3. Support for Algorithm Agility In order to provide a means of addressing problems that may emerge with existing hash algorithms, signature algorithm and encryption algorithms in the future, this document provides a mechanism to - support algotirhm agility. The support for algorithm agility in this + support algorithm agility. The support for algorithm agility in this document is mainly a algorithm notification mechanism between the client and the server. The same client and server SHOULD use the - various algorithm in a single communication session. + same algorithm in a single communication session. If the server does not support the algorithm used by the client, the server SHOULD reply with an AlgorithmNotSupported status code - (defined in Section 9.3) to the client. Upon receiving this status + (defined in Section 10.3) to the client. Upon receiving this status code, the client MAY resend the message protected with the mandatory algorithm. -5.4. Applicability +5.4. Caused change to RFC3315 + + This protocol changes DHCPv6 message exchanges quite substantially: + previously, the client first sends a Solicit message, gets possibly + multiple Advertise messages, chooses the server (= sender of one of + the Advertises) that would be best for the client, and then sends a + Request to that chosen server. Now the server selection is done at + the key exchange phase (the initial Information-request and Reply + exchange). In addition, the Solicit and Rebind messages can be sent + only to a single server. If the client doesn't like the Advertise it + could restart the whole process, but it will be more expensive, and + there's no guarantee that other servers can provide a better + Advertise. For the privacy consideration, we have to give up the + previous server selection feature. + + [RFC3315] provides an additional mechanism for preventing off-network + timing attacks using the Reconfigure message: the Reconfigure Key + authentication method. Secure DHCPv6 can protect the Reconfigure + message using the encryption method. So the Reconfigure Key + authentication method SHOULD NOT be used if Secure DHCPv6 is applied. + +5.5. Applicability In principle, secure DHCPv6 is applicable in any environment where physical security on the link is not assured and attacks on DHCPv6 are a concern. In practice, however, authenticated and encrypted DHCPv6 configuration will rely on some operational assumptions mainly regarding public key distribution and management. In order to achieve the more wide use of secure DHCPv6, opportunistic security - [RFC7435] can be applied for secure DHCPv6 deployment, which allows + [RFC7435] can be applied to secure DHCPv6 deployment, which allows DHCPv6 encryption in environments where support for authentication is not available. - In some scenario where authentication is not available, secure DHCPv6 - provides encryption without authentication to achieve the wide - deployment of secure DHCPv6. - - Secure DHCPv6 provides authentication and encryption based either on - pre-sharing of authorized certificates, or else using trust-on-first- - use. The One feasible environment in an early deployment stage would - be enterprise networks. In such networks the security policy tends - to be strict and it will be easier to manage client hosts. One - trivial deployment scenario is therefore to manually pre-configure - client with the trusted servers' public key and manually register - clients' public keys for the server. It may also be possible to - deploy an internal PKI to make this less reliant on manual - operations, although it is currently subject to future study - specifically how to integrate such a PKI into the DHCPv6 service for - the network. + Secure DHCPv6 can achieve authentication and encryption based on pre- + sharing of authorized certificates. The One feasible environment in + an early deployment stage would be enterprise networks. In + enterprise networks, the client is manually pre-configured with the + trusted servers' public key and the server is also manually pre- + configured with the trusted clients' public keys. In some scenario, + such as coffee shop where the certificate cannot be validated and + don't want to be blocked from the Internet, then the DHCPv6 + configuration process can be encrypted without authentication. Note that this deployment scenario based on manual operation is not different very much from the existing, shared-secret based authentication mechanisms defined in [RFC3315] in terms of operational costs. However, Secure DHCPv6 is still securer than the shared-secret mechanism in that even if clients' keys stored for the server are stolen that does not mean an immediate threat as these are public keys. In addition, if some kind of PKI is used with Secure DHCPv6, even if the initial installation of the certificates is done manually, it will help reduce operational costs of revocation in case a private key (especially that of the server) is compromised. - It is believed that Secure DHCPv6 could be more widely applicable - with integration of generic PKI so that it will be more easily - deployed. But such a deployment requires more general issues with - PKI deployment be addressed, and it is currently unknown whether we - can find practical deployment scenarios. It is subject to future - study and experiments, and out of scope of this document. - 6. DHCPv6 Client Behavior - For the secure DHCPv6 client, a certificate is needed for client - authentication. The client is pre-configured with a certificate and - its corresponding private key. If the client is pre-configured with - public key but not with a certificate, it can generate the self- - signed certificate for client authentication. + The secure DHCPv6 client is pre-configured with a certificate and its + corresponding private key for client authentication. If the client + is pre-configured with public key but not with a certificate, it can + generate the self-signed certificate. The secure DHCPv6 client sends Information-request message as per [RFC3315]. The Information-request message is used by the DHCPv6 client to request the server's identity verification information without having addresses, prefixes or any non-security options assigned to it. The Information-request message MUST NOT include any - DHCPv6 options except ORO option to minimize client's privacy - information leakage. The Option Request option in the Information- - request message MUST contain the option code of the Certificate - option. + other DHCPv6 options except the ORO option to minimize client's + privacy information leakage. The Option Request option in the + Information-request message MUST contain the option code of the + Certificate option. When receiving the Reply messages from DHCPv6 servers, a secure DHCPv6 client discards any DHCPv6 messages that meet any of the following conditions: o the Signature option is missing, o multiple Signature options are present, o the Certificate option is missing. And then the client first checks the support of the hash algorithm, - signature algorithm and encryption algorithm that the server used. - If the check fails, the Reply message is dropped. If the hash - algorithm field is zero, the signature algorithm and hash algorithm - are not separated. The corresponding hash algorithm is fixed - according the signature algorithm. If all the algorithms are - supported, the client then checks the authority of this server. The - client also uses the same algorithms in the return messages. - - The client validates the certificates through the pre-configured - local trusted certificates list or other methods. A certificate that - finds a match in the local trust certificates list is treated as - verified. The message transaction-id is used as the identifier of - the authenticated server's public key for further message encryption. + signature algorithm and encryption algorithm that the server + supports. If the check fails, the Reply message is dropped. If the + hash algorithm field is zero, then it indicates that the hash + algorithm is fixed according to the corresponding signature + algorithm. If all the algorithms are supported, then the client also + uses the same algorithms in the return messages. - At this point, the client has either recognized the certificate of - the server, or decided to drop the message. + Then the client checks the authority of the server. The client + validates the certificates through the pre-configured local trusted + certificates list or other methods. A certificate that finds a match + in the local trust certificates list is treated as verified. The + message transaction-id is used as the identifier of the authenticated + server's public key for further message encryption. At this point, + the client has either recognized the certificate of the server, or + decided to drop the message. The client MUST now authenticate the server by verifying the signature and checking increasing number, if there is a Increasing- number option. The order of two procedures is left as an implementation decision. It is RECOMMENDED to check increasing number first, because signature verification is much more computationally expensive. If the decrypted message contains the - Increasing-number option, the client checks it by comparing it with - the stored number on the client. The client has one stable stored - number for replay attack detection. The initial value of the stable - stored number is zero. If the contained number is higher than the - stored number, then the DHCPv6 message passes the increasing-number - check and the value of the stored number is changed into the value of - the Increasing-number option. If contained number is lower than the - stored number on the server, the server MUST drop the DHCPv6 message. + Increasing-number option, the client checks it according to the rule + defined in Section 9.1. For the message without an Increasing-number + option, according to the client's local policy, it MAY be acceptable + or rejected. If the server rejects such a message, the increasing + number check fails. The Signature field verification MUST show that the signature has - been calculated as specified in Section 9.1.2. Only the messages + been calculated as specified in Section 10.1.2. Only the messages that get through both the signature verification and increasing number check (if there is a Increasing-number option) are accepted. Reply message that does not pass the above tests MUST be discarded. If there are multiple authenticated DHCPv6 certs, the client selects - one DHCPv6 cert for the following network parameters configuration. - The selected DHCPv6 cert may corresponds to multiple DHCPv6 servers. - The client can also choose other implementation method depending on - the client's local policy if the defined protocol can also run - normally. For example, the client can try multiple transactions - (each encrypted with different public key) at the "same" time. + one DHCPv6 cert. The client can also choose other implementation + method depending on the client's local policy if the defined protocol + can also run normally. For example, the client can try multiple + transactions (each encrypted with different public key) at the "same" + time. It should be noted that the selected certificate may + correspond to multiple DHCPv6 servers. If there are no authenticated DHCPv6 certs or existing servers fail authentication, the client should retry a number of times. The client conducts the server discovery process as per section 18.1.5 of [RFC3315] to avoid the packet storm. In this way, it is difficult for the rogue server to beat out a busy "real" server. And then the client takes some alternative action depending on its local policy, - such as attempting to use an unsecured DHCPv6 server. In some - scenario, such as laptops in coffee room, clients are always not pre- - configured the sufficient information for server authentication and - can accept DHCPv6 encryption without DHCPv6 authentication. In such - scenario, if some DHCPv6 servers fail authentication because the - server's certificate is not in the trusted certs' list, and then the - client selects one DHCPv6 server and record the server's public key - for the future encrypted DHCPv6 configuration process. + such as attempting to use an unsecured DHCPv6 server. Once the server has been authenticated, the DHCPv6 client sends the Encrypted-Query message to the DHCPv6 server. The Encrypted-Query message contains the Encrypted-message option, which MUST be - constructed as explained in Section 9.1.4. In addition, the Server - Identifier option MUST be contained if it is in the original message - (i.e. Request, Renew, Decline, Release) to avoid the extra - decryption for the DHCPv6 servers not for it. The Encrypted-message - option contains the DHCPv6 message that is encrypted using the public - key contained in the selected cert. The Server Identifier option is - externally visible to avoid decryption cost by those unselected - servers. The Encrypted-Query message MUST NOT contain other DHCPv6 - option except the Server Identifier option and Encrypted-Message - option. + constructed as explained in Section 10.1.4. In addition, the Server + Identifier option MUST be included if it is in the original message + (i.e. Request, Renew, Decline, Release) to avoid the need for other + servers receiving the message to attempt to decrypt it. The + Encrypted-message option contains the DHCPv6 message that is + encrypted using the public key contained in the selected cert. The + Encrypted-Query message MUST NOT contain any other DHCPv6 option + except the Server Identifier option and Encrypted-Message option. - If the received Reply message indicates the request of the client's - certificate information through the Option Request option, the first - DHCPv6 message sent from the client to the server, such as Solicit - message, MUST contain the Certificate option, Signature option and - Increasing-number option for client authentication. The encryption - text SHOULD be formatted as explain in [RFC5652]. The Certificate - option MUST be constructed as explained in Section 9.1.1. In - addition, one and only one Signature option MUST be contained, which - MUST be constructed as explained in Section 9.1.2. One and only one - Increasing-number option SHOULD be contained, which MUST be - constructed as explained in Section 9.1.3. + The first DHCPv6 message sent from the client to the server, such as + Solicit message, MUST contain the Certificate option, Signature + option and Increasing-number option for client authentication. The + encryption text SHOULD be formatted as explain in [RFC5652]. The + Certificate option MUST be constructed as explained in + Section 10.1.1. It should be noted that a client's certificate for + the mandatory algorithm MUST be contained to ensure that the Reply + message with the error code can be encrypted using the mandatory + algorithm. In addition, one and only one Signature option MUST be + contained, which MUST be constructed as explained in Section 10.1.2. + One and only one Increasing-number option SHOULD be contained, which + MUST be constructed as explained in Section 10.1.3. If the client has multiple certificates with different public/private - key pairs, the message transaction-id is used as the identifier of - the client's private key for decryption. In addition, the subsequent - encrypted DHCPv6 message can contain the Increasing-number option to - defend against replay attack. + key pairs, the message transaction-id is also used as the identifier + of the client's private key for decryption. In addition, the + subsequent encrypted DHCPv6 message can contain the Increasing-number + option to defend against replay attack. For the received Encrypted-Response message, the client MUST drop the Encrypted-Response message if other DHCPv6 option except Encrypted- message option is contained. Then, the client extracts the Encrypted-message option and decrypts it using its private key to obtain the original DHCPv6 message. Then it handles the message as per [RFC3315]. If the decrypted DHCPv6 message contains the - Increasing-number option, the DHCPv6 client MUST drop the DHCPv6 - message with the lower number. If the client fails to get the proper - parameters from the chosen server, it sends the Encrypted-Query - message to another authenticated server for parameters configuration - until the client obtains the proper parameters. + Increasing-number option, the DHCPv6 client checks it according to + the rule defined in Section 9.1. If the client fails to get the + proper parameters from the chosen server, it sends the Encrypted- + Query message to another authenticated server for parameters + configuration until the client obtains the proper parameters. - When the client receives a Reply message with an error status code, - the error status code indicates the failure reason on the server - side. According to the received status code, the client MAY take - follow-up action: + When the decrypted message is Reply message with an error status + code, the error status code indicates the failure reason on the + server side. According to the received status code, the client MAY + take follow-up action: o Upon receiving an AlgorithmNotSupported error status code, the client SHOULD resend the message protected with one of the mandatory algorithms. o Upon receiving an AuthenticationFail error status code, the client is not able to build up the secure communication with the server. However, there may be other DHCPv6 servers available that successfully complete authentication. The client MAY use the AuthenticationFail as a hint and switch to other certificate if it @@ -491,123 +486,121 @@ status code as if it had not been received. But it SHOULD NOT retry with the same certificate. However, if the client decides to retransmit using the same certificate after receiving AuthenticationFail, it MUST NOT retransmit immediately and MUST follow normal retransmission routines defined in [RFC3315]. o Upon receiving a DecryptionFail error status code, the client MAY resend the message following normal retransmission routines defined in [RFC3315]. - o Upon receiving a IncreasingnumFail error status code, the client - MAY resend the message with an adjusted Increasing-number option - according to the returned clock from the DHCPv6 server. + o Upon receiving a ReplayDetected error status code, the client MAY + resend the message with an adjusted Increasing-number option + according to the returned number from the DHCPv6 server. o Upon receiving a SignatureFail error status code, the client MAY resend the message following normal retransmission routines defined in [RFC3315]. 7. DHCPv6 Server Behavior - For the secure DHCPv6 server, a certificate is needed for server - authentication. The server is pre-configured with a certificate and - its corresponding private key. If the server is pre-configured with - public key but not with a certificate, it can generate the self- - signed certificate for server authentication. + The secure DHCPv6 server is pre-configured with a certificate and its + corresponding private key for server authentication. If the server + is pre-configured with public key but not with a certificate, it can + generate the self-signed certificate. When the DHCPv6 server receives the Information-request message and the contained Option Request option identifies the request is for the server certificate information, it replies with a Reply message to the client. The Reply message MUST contain the requested Certificate - option, which MUST be constructed as explained in Section 9.1.1, and + option, which MUST be constructed as explained in Section 10.1.1, and Server Identifier option. In addition, the Reply message MUST contain one and only one Signature option, which MUST be constructed - as explained in Section 9.1.2. Besides, the Reply message SHOULD + as explained in Section 10.1.2. Besides, the Reply message SHOULD contain one and only one Increasing-number option, which MUST be - constructed as explained in Section 9.1.3. In addition, if client + constructed as explained in Section 10.1.3. In addition, if client authentication is needed, then the ORO option in the Reply message contains the code of the certificate option to indicate the request of the client certificate information. Upon the receipt of Encrypted-Query message, the server MUST drop the - message if the other DHCPv6 option except Server Identifier option - and Encrypted-message option is contained. Then, the server checks - the Server Identifier option if the Encrypted-Query message contains - the Server Identifier option. The DHCPv6 server drops the message - that is not for it, thus not paying cost to decrypt messages not for - it. It decrypts the Encrypted-message option using its private key - if it is the target server. + message if the other DHCPv6 option is contained except Server + Identifier option and Encrypted-message option. Then, the server + checks the Server Identifier option if the Encrypted-Query message + contains it. The DHCPv6 server drops the message that is not for it, + thus not paying cost to decrypt messages. It decrypts the Encrypted- + message option using its private key if it is the target server. If + the decryption fails, the server SHOULD send an encrypted Reply + message with a DecryptionFail error status code, defined in + Section 10.3, back to the client. - If the secure DHPCv6 need client authentication and decrypted message - is a Solicit/Information-request message which contains the + If secure DHCPv6 server needs client authentication and decrypted + message is a Solicit/Information-request message which contains the information for client authentication, the secure DHCPv6 server discards the received message that meets any of the following conditions: o the Signature option is missing, o multiple Signature options are present, o the Certificate option is missing. - In such failure, the server replies with an UnspecFail (value 1, - [RFC3315]) error status code. + In such failure, the server SHOULD send an encrypted Reply message + with an UnspecFail (value 1, [RFC3315]) error status code to the + client. The server SHOULD first check the support of the hash function, - signature algorithm, encryption algorithm that the client used. If - the hash algorithm field is zero, then the signature algorithm and - hash algorithm are not separated. The corresponding hash algorithm - is fixed according the signature algorithm. If the check fails, the - server SHOULD reply with an AlgorithmNotSupported error status code, - defined in Section 9.3, back to the client. If all the algorithms - are supported, the server then checks the authority of this client. + signature algorithm, encryption algorithm that the client supports. + If the hash algorithm field is zero, then the corresponding hash + algorithm is fixed according to the signature algorithm. If the + check fails, the server SHOULD reply with an AlgorithmNotSupported + error status code, defined in Section 10.3, back to the client. + Because the server does not support the acknowledged algorithm, the + Reply message with the AlgorithmNotSupported error status code is + encrypted with the mandatory algorithm. If all the algorithms are + supported, the server then checks the authority of this client. The server validates the client's certificate through the local pre- configured trusted certificates list. A certificate that finds a match in the local trust certificates list is treated as verified. The message that fails authentication validation MUST be dropped. In such failure, the DHCPv6 server replies with an AuthenticationFail - error status code, defined in Section 9.3, back to the client. At - this point, the server has either recognized the authentication of - the client, or decided to drop the message. + error status code, defined in Section 10.3, back to the client. The + Reply message with the AuthenticationFail error status code is also + encrypted. At this point, the server has either recognized the + authentication of the client, or decided to drop the message. If the decrypted message contains the Increasing-number option, the - server checks it by comparing it with the stored number on the - server. The server has one stable stored number for replay attack - detection. The initial value of the stable stored number is zero. - If the contained number is higher than the stored number, the value - of the stored number is changed into the value of the Increasing- - number option. If contained number is lower than the stored number - on the server, the server MUST drop the DHCPv6 message and a - IncreasingnumFail error status code, defined in Section 9.3, should - be sent back to the client. Depending on server's local policy, the - message without a Increasing-number option MAY be acceptable or - rejected. If the server rejects such a message, a IncreasingnumFail - error status code should be sent back to the client. The Reply - message that carries the IncreasingnumFail error status code carries - a Increasing-number option, which indicates the server's storage - number for the client to use. + server checks it according to the rule defined in Section 9.1. If + the check fails, an encrypted Reply message with a ReplayDetected + error status code, defined in Section 10.3, should be sent back to + the client. In addition, a Increasing-number option is carried to + indicate the server's stored number for the client to use. According + to the server's local policy, the message without an Increasing- + number option MAY be acceptable or rejected. If the server rejects + such a message, the server processes it as the increasing number + check fails. The Signature field verification MUST show that the signature has - been calculated as specified in Section 9.1.2. Only the clients that - get through both the signature verification and increasing number - check (if there is a Increasing-number option) are accepted as + been calculated as specified in Section 10.1.2. If the signature + check fails, the DHCPv6 server SHOULD send an encrypted Reply message + with a SignatureFail error status code. Only the clients that get + through both the signature verification and increasing number check + (if there is a Increasing-number option) are accepted as authenticated clients and continue to be handled their message as - defined in [RFC3315]. Clients that do not pass the above tests MUST - be treated as unauthenticated clients. The DHCPv6 server SHOULD - reply a SignatureFail error status code, defined in Section 9.3, for - the signature verification failure. + defined in [RFC3315]. Once the client has been authenticated, the DHCPv6 server sends the Encrypted-response message to the DHCPv6 client. The Encrypted- response message MUST only contain the Encrypted-message option, - which MUST be constructed as explained in Section 9.1.4. The + which MUST be constructed as explained in Section 10.1.4. The encryption text SHOULD be formatted as explain in [RFC5652]. The Encrypted-message option contains the encrypted DHCPv6 message that is encrypted using the authenticated client's public key. To provide the replay protection, the Increasing-number option can be contained in the encrypted DHCPv6 message. 8. Relay Agent Behavior When a DHCPv6 relay agent receives an Encrypted-query or Encrypted- response message, it may not recognize this message. The unknown @@ -626,32 +619,67 @@ or server. Relay agent is RECOMMENDED to cache server announcements to form the list of the available DHCPv6 server certs. If the relay agent receives the Information-request message, then it replies with a list of server certs available locally. In this way, the client can be confident of a quick response, and therefore treat the lack of a quick response as an indication that no authenticated DHCP servers exist. -9. Extensions for Secure DHCPv6 +9. Processing Rules + +9.1. Increasing Number Check + + In order to check the Increasing-number option, defined in + Section 10.1.3, the client/server has one stable stored number for + replay attack detection. The server should keep a record of the + increasing number forever. And the client keeps a record of the + increasing number during the transaction with the DHCPv6 server. In + addition, the client can forget the increasing number information + after the transaction is finished. + + It is essential to remember that the increasing number is finite. + All arithmetic dealing with sequence numbers must be performed modulo + 2^64. This unsigned arithmetic preserves the relationship of + sequence numbers as they cycle from 2^64 - 1 to 0 again. + + In order to check the Increasing-number option, the following + comparison is needed. The symbol ">=" means "more or equal" (modulo + 2^64). + + NUM.STO = the stored number in the client/server + + NUM.REC = the acknowledged number from the received message + + The Increasing-number option in the received message passes the + increasing number check if it meets the following condition: + + NUM.REC >= NUM.STO + + And then, the value of NUM.STO is changed into the value of NUM.REC. + + The increasing number check fails if NUM.REC is less than NUM.STO. + +10. Extensions for Secure DHCPv6 This section describes the extensions to DHCPv6. Four new DHCPv6 options, two new DHCPv6 messages and five new status codes are defined. -9.1. New DHCPv6 Options +10.1. New DHCPv6 Options -9.1.1. Certificate Option +10.1.1. Certificate Option - The Certificate option carries the certificate of the client/server. - The format of the Certificate option is described as follows: + The Certificate option carries the certificate(s) of the client/ + server. The format of the Certificate option is described as + follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OPTION_CERTIFICATE | option-len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | EA-id | | +-+-+-+-+-+-+-+-+ . . Certificate (variable length) . . . @@ -662,26 +690,26 @@ option-len 1 + Length of certificate in octets. EA-id Encryption Algorithm id. The encryption algorithm is used for the encrypted DHCPv6 configuration process. This design is adopted in order to provide encryption algorithm agility. The value is from the Encryption Algorithm for Secure DHCPv6 registry in IANA. A registry of the initial assigned values is defined in Section 12. - Certificate A variable-length field containing certificate. The + Certificate A variable-length field containing certificates. The encoding of certificate and certificate data MUST be in format as defined in Section 3.6, [RFC7296]. The support of X.509 certificate is mandatory. -9.1.2. Signature option +10.1.2. Signature option The Signature option allows a signature that is signed by the private key to be attached to a DHCPv6 message. The Signature option could be in any place within the DHCPv6 message while it is logically created after the entire DHCPv6 header and options. It protects the entire DHCPv6 header and options, including itself. The format of the Signature option is described as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 @@ -734,43 +762,45 @@ the next octet boundary if its size is not a multiple of 8 bits. The padding length depends on the signature algorithm, which is indicated in the SA-id field. Note: If Secure DHCPv6 is used, the DHCPv6 message is encrypted in a way that the authentication mechanism defined in RFC3315 does not understand. So the Authentication option SHOULD NOT be used if Secure DHCPv6 is applied. -9.1.3. Increasing-number Option +10.1.3. Increasing-number Option The Increasing-number option carries the number which is higher than the local stored number on the client/server. It adds the anti- replay protection to the DHCPv6 messages. It is optional. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -| OPTION_INCREASINGNUM | option-len | + | OPTION_INCREASING_NUM | option-len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | -| InreasingNum (32-bit) | + | InreasingNum (64-bit) | + | | + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -option-code OPTION_INCREASINGNUM (TBA3). + option-code OPTION_INCREASING_NUM (TBA3). -option-len 4, in octets. + option-len 8, in octets. -IncreasingNum A number which is higher than the local stored number on the - client/server for the replay attack detection. + IncreasingNum A number for the replay attack detection which is more + or equal compared with the local stored number. -9.1.4. Encrypted-message Option +10.1.4. Encrypted-message Option The Encrypted-message option carries the encrypted DHCPv6 message with the recipient's public key. The format of the Encrypted-message option is: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | option-code | option-len | @@ -786,21 +816,21 @@ option-code OPTION_ENCRYPTED_MSG (TBA4). option-len Length of the encrypted DHCPv6 message. encrypted DHCPv6 message A variable length field containing the encrypted DHCPv6 message sent by the client or the server. In Encrypted-Query message, it contains encrypted DHCPv6 message sent by a client. In Encrypted-response message, it contains encrypted DHCPv6 message sent by a server. -9.2. New DHCPv6 Messages +10.2. New DHCPv6 Messages Two new DHCPv6 messages are defined to achieve the DHCPv6 encryption: Encrypted-Query and Encrypted-Response. Both the DHCPv6 messages defined in this document share the following format: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | msg-type | transaction-id | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ @@ -811,46 +841,48 @@ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: The format of Encrypted-Query and Encrypted-Response Messages msg-type Identifier of the message type. It can be either Encrypted-Query (TBA5) or DHCPv6-Response (TBA6). transaction-id The transaction ID for this message exchange. - options The Encrypted-Query message MUST only contain the - Server Identifier option or Encrypted-message option. - The Encrypted-Response message MUST only contain the + options The Encrypted-Query message MUST contain the + Encrypted-message option and MUST contain the Server + Identifier option if the message in the Encrypted- + message option has a Server Identifier option. The + Encrypted-Response message MUST only contain the Encrypted-message option. -9.3. Status Codes +10.3. Status Codes The following new status codes, see Section 5.4 of [RFC3315] are defined. o AlgorithmNotSupported (TBD7): indicates that the DHCPv6 server does not support algorithms that sender used. o AuthenticationFail (TBD8): indicates that the message from the DHCPv6 client fails authentication check. - o IncreasingnumFail (TBD9): indicates the message from DHCPv6 client + o ReplayDetected (TBD9): indicates the message from DHCPv6 client fails the increasing number check. o SignatureFail (TBD10): indicates the message from DHCPv6 client fails the signature check. o DecryptionFail (TBD11): indicates the message from DHCPv6 client fails the DHCPv6 message decryption. -10. Security Considerations +11. Security Considerations This document provides the authentication and encryption mechanisms for DHCPv6. [RFC6273] has analyzed possible threats to the hash algorithms used in SEND. Since Secure DHCPv6 defined in this document uses the same hash algorithms in similar way to SEND, analysis results could be applied as well: current attacks on hash functions do not constitute any practical threat to the digital signatures used in the signature algorithm in Secure DHCPv6. @@ -859,44 +891,44 @@ number option, may have to face the risk of replay attacks. There are some mandatory algorithm for encryption algorithm in this document. It may be at some point that the mandatory algorithm is no longer safe to use. If the client tries more than one cert for client authentication, the server can easily get a client that implements this to enumerate its entire cert list and probably learn a lot about a client that way. -11. IANA Considerations +12. IANA Considerations This document defines four new DHCPv6 [RFC3315] options. The IANA is requested to assign values for these four options from the DHCPv6 Option Codes table of the DHCPv6 Parameters registry maintained in http://www.iana.org/assignments/dhcpv6-parameters. The four options are: - The Certificate Option (TBA1), described in Section 9.1.1. + The Certificate Option (TBA1), described in Section 10.1.1. - The Signature Option (TBA2), described in Section 9.1.2. + The Signature Option (TBA2), described in Section 10.1.2. - The Increasing-number Option (TBA3),described in Section 9.1.3. + The Increasing-number Option (TBA3),described in Section 10.1.3. - The Encrypted-message Option (TBA4), described in Section 9.1.4. + The Encrypted-message Option (TBA4), described in Section 10.1.4. The IANA is also requested to assign value for these two messages from the DHCPv6 Message Types table of the DHCPv6 Parameters registry maintained in http://www.iana.org/assignments/dhcpv6-parameters. The two messages are: - The Encrypted-Query Message (TBA5), described in Section 9.2. + The Encrypted-Query Message (TBA5), described in Section 10.2. - The Encrypted-Response Message (TBA6), described in Section 9.2. + The Encrypted-Response Message (TBA6), described in Section 10.2. The IANA is also requested to add three new registry tables to the DHCPv6 Parameters registry maintained in http://www.iana.org/assignments/dhcpv6-parameters. The three tables are the Hash Algorithm for Secure DHCPv6 table, the Signature Algorithm for Secure DHCPv6 table and the Encryption Algorithm for Secure DHCPv6 table. Initial values for these registries are given below. Future assignments are to be made through Standards Action [RFC5226]. @@ -923,44 +955,51 @@ Encryption algorithm for Secure DHCPv6. The values in this table are 8-bit unsigned integers. The following initial values are assigned for encryption algorithm for Secure DHCPv6 in this document: Name | Value | RFCs -------------------+---------+-------------- RSA | 0x01 | this document IANA is requested to assign the following new DHCPv6 Status Codes, - defined in Section 9.3, in the DHCPv6 Parameters registry maintained + defined in Section 10.3, in the DHCPv6 Parameters registry maintained in http://www.iana.org/assignments/dhcpv6-parameters: Code | Name | Reference ---------+-----------------------+-------------- TBD7 | AlgorithmNotSupported | this document TBD8 | AuthenticationFail | this document - TBD9 | IncreasingnumFail | this document + TBD9 | ReplayDetected | this document TBD10 | SignatureFail | this document TBD11 | DecryptionFail | this document -12. Acknowledgements +13. Acknowledgements The authors would like to thank Tomek Mrugalski, Bernie Volz, Jianping Wu, Randy Bush, Yiu Lee, Sean Shen, Ralph Droms, Jari Arkko, Sean Turner, Stephen Farrell, Christian Huitema, Stephen Kent, Thomas Huth, David Schumacher, Francis Dupont, Gang Chen, Suresh Krishnan, Fred Templin, Robert Elz, Nico Williams, Erik Kline, Alan DeKok, Bernard Aboba, Sam Hartman, Qi Sun, Zilong Liu and other members of the IETF DHC working group for their valuable comments. This document was produced using the xml2rfc tool [RFC2629]. -13. Change log [RFC Editor: Please remove] +14. Change log [RFC Editor: Please remove] + + draft-ietf-dhc-sedhcpv6-14: For the deployment part, Tofu is out of + scope and take Opportunistic security into consideration; Increasing + number option is changed into 64 bits; Increasing number check is a + separate section; IncreasingnumFail error status code is changed into + ReplayDetected error status code; Add the section of "caused change + to RFC3315"; draft-ietf-dhc-sedhcpv6-13: Change the Timestamp option into Increasing-number option and the corresponding check method; Delete the OCSP stampling part for the certificate check; Add the scenario where the hash and signature algorithms cannot be separated; Add the comparison with RFC7824 and RFC7844; Add the encryption text format and reference of RFC5652. Add the consideration of scenario where multiple DHCPv6 servers share one common DHCPv6 server. Add the statement that Encrypted-Query and Encrypted-Response messages can only contain certain options: Server Identifier option and Encrypted- @@ -1048,33 +1087,20 @@ Ted Lemon, Bernie Volz, Ralph Droms. Separated Public Key/ Certificate option into two options. Refined many detailed processes. 2013-10-08. draft-jiang-dhc-sedhcpv6-00: original version, this draft is a replacement of draft-ietf-dhc-secure-dhcpv6, which reached IESG and dead because of consideration regarding to CGA. The authors followed the suggestion from IESG making a general public key based mechanism. 2013-06-29. -14. Open Issues [RFC Editor: Please remove] - - The Reply message with the error status code may contain the client - identifier option, then the client's privacy information may be - disclosed. The possible way is that we encrypts the Reply message. - But if the error is AlogorithmNotSupported, then the server cannot - encrypt the message with the algorithm used by client. - - We need to add some explanation on why TOFU is out of scope - currently. TOFU is tricky to get it right. If it is included, then - operator may skip necessary setup for security. TOFU may be included - in the future work. - 15. References 15.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6