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TODO: Add example traffic here (as plain text or Wireshark screenshot). {{attachment:Wireshark_1.2.9-OpenSSL_Cryptlib-CMP-Initial_Registration.png}}

Certificate Management Protocol (CMP)

CMP is a protocol for managing Public Key Infrastructures (PKI) based on X.509v3 certificates. Protocol messages are defined for certificate creation and management. It is used by commercial PKI products as Entrust Security Manager, Unicert, Insta Certifier and Cryptlib. An OpenSSL client side implementation is work in progess.

Protocol dependencies

  • CMP used its own "TCP-Messaging" protocol on top of TCP in the RFC 2510 version and also in some implementations of RFC 4210. The well known TCP port for CMP traffic is 829.

  • HTTP is nowadays commonly used for for RFC 4210 implementations as transport protocol. The Content-Type set in the HTTP header is "application/pkixcmp"

  • Some implementations might the above mentioned transport protocols in combination, i.e. TCP-Messaging-over-HTTP. In that case, the Content-Type set in the HTTP header should be the unofficial "application/pkixcmp-poll".
  • While there is no implementation known supporting it, transporting CMP over email (SMTP, POP etc.) or file transfer (FTP) is also mentioned in CMPtrans (see below).

Example traffic

Wireshark_1.2.9-OpenSSL_Cryptlib-CMP-Initial_Registration.png

Preference Settings

Wireshark_1.2.9_Windows-CMP_Preferences.png

Reassemble CMP-over-TCP message spanning multiple TCP segments:

When this preference is enabled, the CMP dissector will reassemble CMP messages, using TCP-Messaging protocol for transport, when it has been transmitted over more than one TCP segment.

Alternate TCP port:

This preference can be used to set the TCP port for TCP-Messaging when it is different than the well-known TCP port (829) for transporting CMP, which is used by default. This default is used when the preference is set to 0.

Alternate HTTP port:

This preference can be used to set an alternate TCP port in case of HTTP transport. This option should be set either when a TCP port is used which is not configured to be HTTP or when the Content-Type of the transmitted HTTP header is wrongfully not set to "application/pkixcmp". This preverence is disabled when the value is set to 0.

Alternate TCP-style-HTTP port:

This preference can be used to set an alternate TCP port in case of TCP-messaging over HTTP transport. This option should be set either when a TCP port is used which is not configured to be HTTP or when the Content-Type of the transmitted HTTP header is wrongfully not set to (the unofficial) "application/pkixcmp-poll". This preverence is disabled when the value is set to 0.

Example capture file

Display Filter

A complete list of CMP display filter fields can be found in the display filter reference

  • Show only the CMP based traffic:
     cmp 

Capture Filter

You cannot directly filter CMP while capturing. However, if you know the TCP port used (see above), you can filter on that one.

  • Capture only the TCP-Messaging CMP traffic over the default port (829):
     tcp port 829 

  • RFC 4210 Internet X.509 Public Key Infrastructure Certificate Management Protocols. This version obsoletes RFC 2510. According to the new RFC, the CMP transport protocol issues are handled in the separate CMPtrans document.

  • RFC 4211 Certificate Request Message Format is more or less bound to CMP. This Version obsoletes RFC 2511 and is used by RFC 4210

  • Last IETF CMPtrans draft This draft for CMPtrans is expired, hence there is no obligatory transport protocols spec available. There are obvious mistakes in it which may cause confusion. Implementations more or less adhere to it.

CMP (last edited 2013-02-16 10:47:51 by LTejas)