A Protocol for Provisioning Resource Certificates

This RPKI certificate provisioning protocol is expressed as a simple request/response interaction, where the client passes a request to the server, and the server generates a corresponding response. The protocol is implemented as an exchange of messages. Messages are passed over an HTTPS transport connection that safeguards against interception and replay attacks. The HTTPS session uses mutually authenticated Transport Layer Security (TLS) . The TLS keys and associated certificate chain used to validate TLS transactions is assumed to have been previously communicated between the two entities, through mechanisms not defined in this protocol specification. The HTTPS connection will use 2 way (mutual) identification. A message exchange commences with the client initiating an HTTP POST with content type of "application/x-rpki", with the message object as the body. The server's response will similarly be the body of the response with a content type of "application/x-rpki". The content of the POST, and the server's response, will be a "well-formed" Cryptographic Message Syntax (CMS) object, encoded using the Distinguished Encoding Rules for ASN.1 (DER) , formatted in accordance with the CMS profile as specified in the following section. CMS is used as the signing format to sign the message object. The public part of the signing key and the associated certificate chain that is used to validate the CMS digital signature is assumed to have been communicated between the two entities, through mechanisms not defined in this protocol specification. The CMS keys and certificates MAY be the same as those used for TLS. The protocol's request / response interaction is assumed to be reliable, in that all requests will generate a matching response. The protocol requires sequential operation, where the server MUST NOT accept a client's request unless it has generated and sent a response to the client's previous request. Attempts by the client to initiate multiple requests in parallel MUST be detected by the server and rejected with an error response.

The format of the CMS object is:

The protocol objects are all instances of CMS signed-data objects, where the ContentType used is the signed-data type of id-data, namely id-signedData, OID = 1.2.840.113549.1.7.2.

According to , signed-data content types shall have the ASN.1 type SignedData:

The version is the syntax version number. It MUST be 3, corresponding to the signerInfo structure having version number 3.

The digestAlgorithms set MUST include only SHA-256, the OID for which is 2.16.840.1.101.3.4.2.1 . It MUST NOT contain any other algorithms.

encapContentInfo is the signed content, consisting of a content type identifier and the content itself.

The eContentType for the RPKI Protocol Message object is defined as id-ct-xml, and has the numerical value of 1.2.840.113549.1.9.16.1.28.

The content of a RPKI XML Protocol Object consists of a single protocol message, structured according to a define XML schema, as defined in subsequent sections of this document. The eContent field of the CMS object is formally defined using ASN.1 as:

The certificates field MUST be present, and MUST contain the EE certificate of the key pair whose private key value was used to sign the CMS. This MUST NOT be an RPKI certificate, and SHOULD be a certificate that is recognised to attest to the identity of the party that created the CMS object. This field MAY contain other certificates that a relying party may use to validate the digital signature of the CMS object.

This field MUST be present. The contents of the field are specified in .

SignerInfo is defined under CMS as:

The version number MUST be 3, corresponding with the choice of SubjectKeyIdentifier for the sid.

The sid is defined as:

In this profile, the sid MUST be a SubjectKeyIdentifier.

The digestAlgorithm MUST be SHA-256, the OID for which is 2.16.840.1.101.3.4.2.1.

Signed Attributes are defined as:

The signer MUST digitally sign a collection of attributes along with the content payload. Each attribute in the collection MUST be DER-encoded. The syntax for attributes is defined in , and the X.500 Directory provides a rich attribute syntax. A very simple subset of this syntax is used extensively in , where ATTRIBUTE.Type and ATTRIBUTE.id are the only parts of the ATTRIBUTE class that are employed. Each of the attributes used with this CMS profile has a single attribute value. Even though the syntax is defined as a SET OF AttributeValue, there MUST be exactly one instance of AttributeValue present. The SignedAttributes syntax within signerInfo is defined as a SET OF Attribute. The SignedAttributes MUST include only one instance of any particular attribute. The signer MUST include the content-type, message-digest and signing-time signed attributes. The signer MAY also include the binary-signing-time signed attribute. Other signed attributes that are deemed appropriate MAY also be included. The intent is to allow additional signed attributes to be included if a future need is identified. This does not cause an interoperability concern because unrecognized signed attributes are ignored at verification.

A content-type attribute is required to contain the same object identifier as the content type contained in the EncapsulatedContentInfo. The signer MUST include a content-type attribute containing the appropriate content type. Section 11.1 of defines the content-type attribute.

The signer MUST include a message-digest attribute, having as its value the output of a one-way hash function computed on the content that is being signed. Section 11.2 of defines the message-digest attribute.

The signing-time attribute MUST be present. The signing-time attribute specifies the time, based on the local system clock, when the digital signature was applied to the content. Section 11.3 of defines the content-type attribute.

The signer MAY include a binary-signing-time attribute, specifying the time at which the digital signature was applied to the content. If the binary-signing-time is present, the time that is represented MUST represent the same time value as the signing-time attribute. The binary-signing-time attribute is defined in .

The signatureAlgorithm MUST be RSA (rsaEncryption), the OID for which is 1.2.840.113549.1.1.1.

The signature value is defined as:

The signature characteristics are defined by the digest and signature algorithms.

unsignedAttrs MUST be omitted.

The following is the ASN.1 specification of the CMS signed object used by the RPKI provisioning protocol.

The XML template for all messages is as follows:

[payload] --------------------------------------------------------------- ]]> the value of this attribute is the version of this protocol. This document describes version 1. the value of this attribute is the agreed name of the message sender, as determined between the client and the server by prior arrangement. the value of this attribute is the agreed name of the message recipient, as determined between the client and the server by prior arrangement. the possible values of this attribute are "list", "list_response", "issue", "issue_response", "revoke", "revoke_response", and "error_response". Conforming parsers MUST reject any document with a version number they do not understand, or with any elements or attributes they do not understand. Servers must generate an error response when receiving such a request. Clients should generate an operator alert error when receiving such a response. A message in this protocol is a digitally signed object that makes use of CMS , and is encoded as DER. It uses the signed-data object contentType OID: 1.2.840.113549.1.7.2. The attribute "id-signingTime" (contentType OID: 1.2.840.113549.1.9.5) MUST be present in the CMS object. The encapsulated content of the CMS wrapping is an XML document. The remainder of this protocol specification omits this CMS wrapper and only discusses the XML document. Messages are checked using the following tests: Check the integrity of the HTTPS message and validate the TLS certificate using the PKI that has been determined by prior arrangement between client and server. Check that the CMS is well-formed. Check that the XML is well-formed. Check that the XML sender and recipient attributes reference a known client and this server's system respectively. Verify the digital signature using the public key provided in the certificate carried in the CMS wrapper. Validate the CMS-provided certificate using the PKI that has been determined by prior arrangement between client and server. Check that the value of the version number of the message is 1. The checks should generally be applied in the order specified here. Any errors encountered while checking items 1 through 6 would cause the server to generate an "HTTP 400 Bad Data" response to the HTTPS POST operation. An error in step 7 would cause the server to generate a "Request-Not-Performed" error response.

The value of the message "type" message attribute for this query is: type="list"

The value of the message "type" element for this response is: type="list_response"

[certificate] ... (repeated for each current certificate where the client is the certificate's subject) [issuer's certificate] ... (repeated for each of the issuer's resource class where the client has been allocated resources) --------------------------------------------------------------- ]]> Where the client has been allocated resources from multiple resource classes, then the response will contain multiple class elements, corresponding to the complete set of the issuer's resource classes where the client holds allocated resources. Those issuer's resource classes where the client holds no allocated resources will not be included in the response. Where the issuer has issued multiple certificates in a resource class signed with different keys (as may occur during a staged issuer-key rollover), only the most recent certificate issued with the currently "active" issuer's key will be listed in the response. Each "class" element describes a set of resources that are certified within the scope of a single certificate, referring to a single resource class with a common validation path. the value of this attribute is the issuer-assigned name of the issuer's Resource Class. in the context of a class element, the value of this attribute is a pointer to the issuer's CA certificate (i.e. a reference to the immediate superior certificate, being the CA-enabled certificate where the issuer is the certificate's subject). Its value is a comma-separated list of URIs, of which at least one MUST be an RSYNC URI. Any comma values within a URI MUST be escaped ("%2C"). The ordering of the list may be interpreted by the client as a relative preference for access methods as expressed by the publisher of this certificate. in the context of a class element, the value of this attribute is the set of AS numbers and AS number ranges that the issuer has allocated to the client within the scope of this resource class, presented in ASCII as a comma-separated list. The list elements are decimal integer values and ranges of decimal integers specified by the low and high value of the range with a hyphen delimiter, using the canonical order as described in , without leading zeros, and with no white space or punctuation other than the comma and the hyphen range designator (e.g.: resource_set_as="123,456-789,123456"). If there are no AS numbers in this Resource Class the empty set will be represented by a null string value ("") for this attribute. in the context of a class element, the value of this attribute is the set of IPv4 addresses that the issuer has allocated to the client within the scope of this resource class. The value is presented in ASCII as a comma-separated list of elements. Each element is either an address prefix using the notation of <dotted quad>/mask length, or a range specified as low and high range values in dotted quad notation with a hyphen delimiter. The list is presented in canonical order, as described in . The dotted quad notation is without leading zeros, and the list contains no white space or punctuation other than the period, forward slash, hyphen and comma. (e.g. resource_set_ipv4="192.0.2.0/26,192.0.2.66-192.0.2.76") If there are no IPv4 addresses in this resource class the empty set will be represented by a null string value ("") for this attribute. in the context of a class element, the value of this attribute is the set of IPv6 addresses that the issuer has allocated to the client within the scope of this resource class. The value is presented in ASCII as a comma-separated list of elements. Each element is either an address prefix using the notation of <hex nibble sequence>/mask length, or a range specified as low and high range values in hex nibble notation with a hyphen delimiter. Trailing zero nibbles are truncated and represented by '::'. The list is presented in canonical order, as described in . The hex nibble sequence notation is without leading zeros, and the list contains no white space or punctuation other than the colon, forward slash, hyphen and comma (e.g. resource_set_ipv6="2001:0DB8::/48,2001:0DB8:002::-2001:0DB8:005::"). The XML Schema data type is "http://www.w3.org/TR/xmlschema-2/#hexBinary" and value is case insensitive, with the canonical form being upper case. If there are no IPv6 addresses in this resource class the empty set will be represented by a null string value ("") for this attribute. The value of this attribute specified the date/time that would be set in the Validity notAfter field in any new certificate issued for this particular client within the scope of this resource class, should the client request a new certificate. The time format used for the value of this attribute is specified as ISO 8601 , and MUST use UTC time (i.e. YYYY-MM-DDThh:mm:ssZ, e.g. 2007-11-29T04:40:00Z). If the client's certificate has a validity notAfter time that is different to this this time then the client SHOULD request a new certificate to be issued for this resource class. (OPTIONAL)If this field is present then it indicates a publication namespace which the server has made available to the client to use for its own collection of published products. Presence of this field does not mean that the client has permission from the repository operator to lodge under this URI, only that the client has permission from the server to lodge under this URI. value is the Base64 encoding of the DER-encoded issuer's CA certificate (the CA-enabled certificate where the issuer is the certificate's subject). Each certificate element describes the most recently issued current certificate where the certificate's subject refers to the client for each active client key pair. A "current" certificate is a non-expired, non-revoked certificate. If no current certificate has been issued, then no certificate element will be included in the response. in the context of a certificate element, this is a pointer to the location where the certificate issuer has published this certificate. This field is the issuer's suggestion for the AIA field for the subject to use in subordinate certificates that are issued by the subject. According to the Resource Certificate Profile [insert ref here] the AIA field is a non-empty (contains a minimum of 1 element) list of URI's, one of which MUST be an RSYNC URI. The order of URI's in the AIA field may be interpreted as the publisher's relative preference for access methods for this certificate. The cert_url conforms to this AIA specification. Its value is a comma-separated list of URIs, one of which MUST be an RSYNC URI. Any comma values within a URI MUST be escaped ("%2C"). the set of AS numbers that were specified in the corresponding original certificate request that defined the maximal requested span of the certified AS number set, following the syntax described above. If this attribute was present in the certificate request, then the attribute MUST be present in this response, otherwise it MUST NOT be present. the set of IPv4 addresses that were specified in the corresponding original certificate request that defined the maximal requested span of the certified IPv4 address set, following the syntax described above. If this attribute was present in the certificate request, then the attribute MUST be present in this response, otherwise it MUST NOT be present. the set of IPv6 addresses that were specified in the corresponding original certificate request that defined the maximal requested span of the certified IPv6 address set, following the syntax described above. If this attribute was present in the certificate request, then the attribute MUST be present in this response, otherwise it MUST NOT be present. value is the Base64 encoding of the DER-encoded certificate.

The value of the message "type" element for this request is: type="issue"

[Certificate request] --------------------------------------------------------------- ]]> The client must use different key pairs for each distinct resource class. If any of the req_resource_set attributes are specified in the request, then any missing req_resource_set attributes are to be interpreted as specifying the complete set of the corresponding resource type that match the client's current resource allocation. If the value of any req_resource_set attributes is the null value (""), then this indicates that no resources of that resource type are to be certified with this request. The requested resource set values are held as a local record by the issuer against the resource class and the client's public key. Any subsequent Certificate Issuance Requests that specify the same Resource Class and the same client's public key will (re)set the issuer's local record of the requested resource sets to the most recently specified values. value is the server's identifier of a Resource Class. (OPTIONAL)the set of AS numbers that define the maximal requested span of the certified AS number set, formatted as per the resource_set_as attribute of the Resource Class List Response. (OPTIONAL)the set of IPv4 addresses that define the maximal requested span of the certified IPv4 address set, formatted as per the resource_set_ipv4 attribute of the Resource Class List Response. (OPTIONAL)the set of IPv6 addresses that define the maximal requested span of the certified IPv6 address set, formatted as per the resource_set_ipv6 attribute of the Resource Class List Response. value is the certificate request. This is a Base-64 encoded DER version of a request formatted using PKCS#10.

The value of the message "type" element for this response is: type="issue_response"

[certificate] [issuer's certificate] --------------------------------------------------------------- ]]> If the certificate issuer determines that the issued certificate would be identical in all respects to the most recently issued certificate for this client, other than the certificate's serial number, were the certificate to be issued, the issuer may choose to respond with the most recently issued certificate and not issue a new certificate for this request. The definition of the attributes and syntax of the values is the same as the resource class list response, but the response only references the (single) named resource class, and the (single) certificate issued against the client's public key as provided in the corresponding certificate request.

The value of the message "type" element for this request is: type="revoke"

--------------------------------------------------------------- ]]> This command 'retires' a client's key pair by requesting the issuer to revoke all certificates for this client that contain the matching public key, within the scope of a named Resource Class. Individual issued certificates cannot be revoked within the scope of this protocol. This command directs the issuer to immediately mark all issued valid certificates issued by this issuer within the named Resource Class with this client's SKI value to be marked as revoked, causing the issued certificates to be withdrawn from the publication repository and to be listed in the server's subsequent CRLs within this Resource Class. value is the issuer-assigned name of the issuer's Resource Class. value is the encoded hash of the client's public key that is to be revoked. The algorithm for the encoding is to generate the 160-bit SHA-1 hash of the client's public key, as defined in method (1) of section 4.2.1.2 of , and encode this value using the Base 64 encoding with URL and Filename Safe Alphabet, as defined in section 5 of .

The value of the message "type" element for this response is: type="revoke_response"

--------------------------------------------------------------- ]]> value is the issuer-assigned name of the server's Resource Class. value is the encoded hash of the client's public key that is to be revoked. The algorithm for the encoding is to generate the 160-bit SHA-1 hash of the client's public key, as defined in method (1) of section 4.2.1.2 of , and encode this value using the Base 64 encoding with URL and Filename Safe Alphabet, as defined in section 5 of .

The value of the message "type" element for this response is: type="error_response"

[Code] [Readable text] --------------------------------------------------------------- ]]> All states where an error response if to be generated, either due to detected errors or inconsistencies in the content of the request or server-side states that prevent the request being performed, generate a Request-Not-Performed response. value is a text field. This element MAY be present. It's value has no defined meaning within the scope of this protocol, and implementations may assume that some form of human-readable text may be used here. If the HTTP request that triggered this error response includes an Accept-Language header as defined in section 14.4 of the HTTP/1.1 specification [insert reference to RFC2616] then the server will make a best effort to include a second description element using the highest ranked preferred language of the client. The en-US description will always be included if the element is present. The error code set is: