TCP Authentication Option (TCP-AO) Test Vectors

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TSV TCPM TCP authentication option test vector This document provides test vectors to validate implementations of the two mandatory authentication algorithms specified for the TCP Authentication Option over both IPv4 and IPv6. This includes validation of the key derivation function (KDF) based on a set of test connection parameters as well as validation of the message authentication code (MAC). Vectors are provided for both currently required pairs of KDF and MAC algorithms: KDF_HMAC_SHA1 and HMAC- SHA-1-96, and KDF_AES_128_CMAC and AES-128-CMAC-96. The vectors also validate both whole TCP segments as well as segments whose options are excluded for middlebox traversal.

Introduction This document provides test vectors to validate the correct implementation of the TCP Authentication Option (TCP-AO) and its mandatory cryptographic algorithms defined in . It includes the specification of all endpoint parameters to generate the variety of TCP segments covered by different keys and MAC coverage, i.e., both the default case and the variant where TCP options are ignored for middlebox traversal. It also includes both default key derivation functions (KDFs) and MAC generation algorithms and lists common pitfalls of implementing the algorithms correctly. The experimental extension to support NAT traversal is not included in the provided test vectors. This document provides test vectors from multiple implementations that have been validated against each other for interoperability.

Conventions Used in This Document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only when, they appear in all capitals, as shown here.

Input Test Vectors

TCP Connection Parameters The following parameters are used throughout this suite of test vectors. The terms 'active' and 'passive' are used as defined for TCP .

TCP-AO Parameters The following values are used for all exchanges. This suite does not test key switchover. The KeyIDs are as indicated for TCP-AO . The Master_Key is used to derive the traffic keys .

Active (client) side KeyID: 61 decimal (0x3d hexadecimal)
Passive (server) side KeyID: 84 decimal (0x54 hexadecimal)
Master_Key: "testvector" (length = 10 bytes)

Active (Client) Side Parameters The following endpoint parameters are used on the active side of the TCP connection, i.e., the side that initiates the TCP SYN.

For IPv4: 10.11.12.13 (dotted decimal)
For IPv6: fd00::1 (IPv6 hexadecimal)
TCP port: (varies)

Passive (Server) Side Parameters The following endpoint parameters are used for the passive side of the TCP connection, i.e., the side that responds with a TCP SYN-ACK.

For IPv4: 172.27.28.29 (dotted decimal)
For IPv6: fd00::2 (IPv6 hexadecimal)
TCP port = 179 decimal (BGP)

Other IP Fields and Options No IP options are used in these test vectors. All IPv4 packets use the following other parameters : Differentiated Services Code Point (DSCP) = 111000 binary (CS7) as is typical for BGP, Explicit Congestion Notification (ECN) = 00 binary, set the Don't Fragment (DF) bit, and clear the More Fragments (MF) bit. IPv4 uses a TTL of 255 decimal; IPv6 uses a hop limit of 255 decimal. All IPv6 packets use the following other parameters : traffic class = 0xe0 hexadecimal (DSCP = 111000 binary CS7, as is typical for BGP, with ECN = 00 binary) and no Extension Headers (EHs).

Other TCP Fields and Options The SYN and SYN-ACK segments include Maximum Segment Size (MSS) , No Operation (NOP), Window Scale , Selective Acknowledgment (SACK) permitted , Timestamp , and TCP-AO , in that order. All other example segments include NOP, NOP, Timestamp, and TCP-AO, in that order. All segment urgent (URG) pointers are zero . All segments with data set the push (PSH) flag . Each TCP connection below uses the Initial Sequence Numbers (ISNs) as indicated at the front of each corresponding section.

IPv4 SHA-1 Output Test Vectors The SHA-1 KDF and MAC algorithms, KDF_HMAC_SHA1 and HMAC-SHA-1-96, are computed as specified for TCP-AO . In the following sections, all values are indicated as 2-digit hexadecimal values with spacing per line representing the contents of 16 consecutive bytes, as is typical for data dumps. The IP/TCP data indicates the entire IP packet, including the TCP segment and its options (whether covered by TCP-AO or not, as indicated), including TCP-AO.

HMAC-SHA-1-96 (Default - Covers TCP Options)

Send (Client) SYN (Covers Options)

Receive (Server) SYN-ACK (Covers Options)

Send (Client) Non-SYN (Covers Options)

Receive (Server) Non-SYN (Covers Options)

HMAC-SHA-1-96 (Omits TCP Options)

Send (Client) SYN (Omits Options)

Receive (Server) SYN-ACK (Omits Options)

Send (Client) Non-SYN (Omits Options)

Receive (Server) Non-SYN (Omits Options)

IPv4 AES-128 Output Test Vectors The AES-128 KDF and MAC algorithms, KDF_AES_128_CMAC and AES-128-CMAC-96, are computed as specified for TCP-AO . In the following sections, all values are indicated as 2-digit hexadecimal values with spacing per line representing the contents of 16 consecutive bytes, as is typical for data dumps. The IP/TCP data indicates the entire IP packet, including the TCP segment and its options (whether covered by TCP-AO or not, as indicated), including TCP-AO.

AES-128-CMAC-96 (Default - Covers TCP Options)

Send (Client) SYN (Covers Options)

Receive (Server) SYN-ACK (Covers Options)

Send (Client) Non-SYN (Covers Options)

Receive (Server) Non-SYN (Covers Options)

AES-128-CMAC-96 (Omits TCP Options)

Send (Client) SYN (Omits Options)

Receive (Server) SYN-ACK (Omits Options)

Send (Client) Non-SYN (Omits Options)

Receive (Server) Non-SYN (Omits Options)

IPv6 SHA-1 Output Test Vectors The SHA-1 KDF and MAC algorithms, KDF_HMAC_SHA1 and HMAC-SHA-1-96, are computed as specified for TCP-AO .

HMAC-SHA-1-96 (Default - Covers TCP Options)

Send (Client) SYN (Covers Options)

Receive (Server) SYN-ACK (Covers Options)

Send (Client) Non-SYN (Covers Options)

Receive (Server) Non-SYN (Covers Options)

HMAC-SHA-1-96 (Omits TCP Options)

Send (Client) SYN (Omits Options)

Receive (Server) SYN-ACK (Omits Options)

Send (Client) Non-SYN (Omits Options)

Receive (Server) Non-SYN (Omits Options)

IPv6 AES-128 Output Test Vectors The AES-128 KDF and MAC algorithms, KDF_AES_128_CMAC and AES-128-CMAC-96, are computed as specified for TCP-AO .

AES-128-CMAC-96 (Default - Covers TCP Options)

Send (Client) SYN (Covers Options)

Receive (Server) SYN-ACK (Covers Options)

Send (Client) Non-SYN (Covers Options)

Receive (Server) Non-SYN (Covers Options)

AES-128-CMAC-96 (Omits TCP Options)

Send (Client) SYN (Omits Options)

Receive (Server) SYN-ACK (Omits Options)

Send (Client) Non-SYN (Omits Options)

Receive (Server) Non-SYN (Omits Options)

Observed Implementation Errors The following is a partial list of implementation errors that this set of test vectors is intended to validate.

Algorithm Issues

The underlying implementation of HMAC-SHA-1-96 or AES-128-CMAC-96 does not pass their corresponding test vectors .
The SNE algorithm does not consider corner cases, possibly because the pseudocode in was not intended as complete, as discussed in , the latter of which includes its own validation sequence.

Algorithm Parameters

KDF context length is incorrect, e.g., it does not include TCP header length + payload length (it should, per TCP-AO).
KDF calculation does not start from counter i = 1 (it should, per TCP-AO crypto algorithms).
KDF calculation does not include output length in bits, contained in two bytes in network byte order (it should, per the TCP-AO crypto algorithms).
KDF uses keys generated from current TCP segment sequence numbers (KDF should use only local and remote ISNs or zero, as indicated in TCP-AO).

String Handling Issues The strings indicated in TCP-AO and its algorithms are indicated as a sequence of bytes of known length. In some implementations, string lengths are indicated by a terminal value (e.g., zero in C). This terminal value is not included as part of the string for calculations.

The password includes the last zero-byte (it should not).
The label "TCP-AO" includes the last zero byte (it should not).

Header Coverage Issues

TCP checksum and/or MAC is not zeroed properly before calculation (both should be).
TCP header is not included in the MAC calculation (it should be).
TCP options are not included in the MAC calculation by default.

There is a separate parameter in the Master Key Tuple (MKT) to ignore options; this document provides test vectors for both options-included and options-excluded cases.

Security Considerations This document is intended to assist in the validation of implementations of TCP-AO to further enable its more widespread use as a security mechanism to authenticate not only TCP payload contents but the TCP headers and protocol. The Master_Key of "testvector" used here for test vector generation SHOULD NOT be used operationally.

IANA Considerations This document has no IANA actions.

References Normative References Informative References

Acknowledgments This work benefited from feedback from and as well as discussions on the IETF TCPM email list and with the IESG. This document was initially prepared using 2-Word-v2.0.template.dot.