The presence of optional Response Header fields causes response parsing to fail.

[ximon18]

Split out from ximon18/keyls#13 (comment).

This causes this code to be incompatible with Securosys Cloud HSM as it provides the "Server Correlation Value" in the response which is legal according to KMIP 1.4 specification specification section 6.1 Server Correlation Value.

KMIP specification 1.4 section 7.2 Operations defines the Response Header as follows:

Object	REQUIRED in Message	Comment
Response Header	Yes	Structure
Protocol Version	Yes	See 6.1
Time Stamp	Yes	See 6.5
Nonce	No	See 2.1.14
Attestation Type	No, MAY be repeated	REQUIRED in Attestation Required error message if client set Attestation Capable Indicator to True in the request, see 9.1.3.2.36
Client Correlation Value	No	See 6.18
Server Correlation Value	No	See 6.19
Batch Count	Yes	See 6.14

While the response parsing code defines ResponseHeader like so:

/// See KMIP 1.0 section 7.2 [Operations](https://docs.oasis-open.org/kmip/spec/v1.0/os/kmip-spec-1.0-os.html#_Toc262581257).
#[derive(Clone, Copy, Debug, Deserialize, Serialize, PartialEq, Eq)]
#[serde(rename = "0x42007A")]
pub struct ResponseHeader {
    #[serde(rename = "0x420069")]
    pub protocol_version: ProtocolVersion,

    #[serde(rename = "0x420092")]
    pub timestamp: i64,

    #[serde(rename = "0x42000D")]
    pub batch_count: i32,
}

Normally with Serde undefined fields are ignored by default if present when deserializing. But with the (legacy, as we have a new parser but are not yet using it for responses, only for requests) response parser in kmip-protocol that isn't the case, the parsing gets confused if the optional fields are present, presenting an error such as:

Error: Deserialize error: Error while deserializing the response: Expected KMIP TTLV type Integer (0x02) but found TextString (0x07)

These missing fields should be defined as Option types.

[ximon18]

Part of the reason for this oversight is likely that the officlal KMIP 1.1 test suite (the last version which describes tests in TTLV format rather than XML), of which part is implemented by this crate, doesn't have any test cases that include the optional response header fields.

[ximon18]

Additionally, none of the optional fields existed in KMIP 1.0 or KMIP 1.1. The Nonce and Attestation Type fields appear first in the KMIP 1.2 specification. The Client Correlation Value and Server Correlation Value fields appear first in the KMIP 1.4 specification.