The following subsection describes feature updates to [
RFC 4210]. They are always related to the base specification. Hence, references to the original sections in [
RFC 4210] are used whenever possible.
Insert this section after the current
Section 1 of
RFC 4210:
1.1. Changes Since
RFC 4210
The following updates are made in this document:
-
Adding new extended key usages for various CMP server types, e.g., registration authority and certification authority, to express the authorization of the entity identified in the certificate containing the respective extended key usage extension that acts as the indicated PKI management entity.
-
Extending the description of multiple protection to cover additional use cases, e.g., batch processing of messages.
-
Offering EnvelopedData as the preferred choice next to EncryptedValue to better support crypto agility in CMP. Note that, according to RFC 4211, Section 2.1, point 9, the use of the EncryptedValue structure has been deprecated in favor of the EnvelopedData structure. [RFC 4211] offers the EncryptedKey structure a choice of EncryptedValue and EnvelopedData for migration to EnvelopedData. For reasons of completeness and consistency, the type EncryptedValue has been exchanged in all occurrences in [RFC 4210]. This includes the protection of centrally generated private keys, encryption of certificates, and protection of revocation passphrases. To properly differentiate the support of EnvelopedData instead of EncryptedValue, CMP version 3 is introduced in case a transaction is supposed to use EnvelopedData.
-
Offering an optional hashAlg field in CertStatus that supports confirmation of certificates signed with signature algorithms, e.g., preparing for upcoming post quantum algorithms, not directly indicating a specific hash algorithm to use to compute the certHash.
-
Adding new general message types to request CA certificates, a root CA update, a certificate request template, or a Certificate Revocation List (CRL) update.
-
Extending the usage of polling to p10cr, certConf, rr, genm, and error messages.
-
Deleting the mandatory algorithm profile in Appendix D.2 of RFC 4210 and referring to Section 7 of RFC 9481.
The following subsection introduces a new extended key usage for CMP servers authorized to centrally generate key pairs on behalf of end entities.
Insert this section after
Section 4.4.3 of
RFC 4210:
4.5. Extended Key Usage
The extended key usage (EKU) extension indicates the purposes for which the certified key pair may be used. Therefore, it restricts the use of a certificate to specific applications.
A CA may want to delegate parts of its duties to other PKI management entities. This section provides a mechanism to both prove this delegation and enable an automated means for checking the authorization of this delegation. Such delegation may also be expressed by other means, e.g., explicit configuration.
To offer automatic validation for the delegation of a role by a CA to another entity, the certificates used for CMP message protection or signed data for central key generation
MUST be issued by the delegating CA and
MUST contain the respective EKUs. This proves the authorization of this entity by delegating CA to act in the given role, as described below.
The OIDs to be used for these EKUs are:
id-kp-cmcCA OBJECT IDENTIFIER ::= {
iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) kp(3) 27 }
id-kp-cmcRA OBJECT IDENTIFIER ::= {
iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) kp(3) 28 }
id-kp-cmKGA OBJECT IDENTIFIER ::= {
iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) kp(3) 32 }
Note:
Section 2.10 of
RFC 6402 specifies OIDs for a Certificate Management over CMS (CMC) CA and a CMC RA. As the functionality of a CA and RA is not specific to any certificate management protocol (such as CMC or CMP), these EKUs are reused by CMP.
The meaning of the id-kp-cmKGA EKU is as follows:
-
CMP KGA:
-
CMP key generation authorities are CAs or are identified by the id-kp-cmKGA extended key usage. The CMP KGA knows the private key it generated on behalf of the end entity. This is a very sensitive service and needs specific authorization, which by default is with the CA certificate itself. The CA may delegate its authorization by placing the id-kp-cmKGA extended key usage in the certificate used to authenticate the origin of the generated private key. The authorization may also be determined through local configuration of the end entity.
Section 5.1.1 of
RFC 4210 describes the PKI message header. This document introduces the new version 3, indicating support of EnvelopedData as specified in
Section 2.7 and hashAlg as specified in
Section 2.10.
Replace the ASN.1 syntax of PKIHeader and the subsequent description of pvno with the following text:
PKIHeader ::= SEQUENCE {
pvno INTEGER { cmp1999(1), cmp2000(2),
cmp2021(3) },
sender GeneralName,
recipient GeneralName,
messageTime [0] GeneralizedTime OPTIONAL,
protectionAlg [1] AlgorithmIdentifier{ALGORITHM, {...}}
OPTIONAL,
senderKID [2] KeyIdentifier OPTIONAL,
recipKID [3] KeyIdentifier OPTIONAL,
transactionID [4] OCTET STRING OPTIONAL,
senderNonce [5] OCTET STRING OPTIONAL,
recipNonce [6] OCTET STRING OPTIONAL,
freeText [7] PKIFreeText OPTIONAL,
generalInfo [8] SEQUENCE SIZE (1..MAX) OF
InfoTypeAndValue OPTIONAL
}
PKIFreeText ::= SEQUENCE SIZE (1..MAX) OF UTF8String
The usage of the protocol version number (pvno) is described in Section
7.
Section 5.1.1 of
RFC 4210 defines the PKIHeader and id-it OIDs to be used in the generalInfo field. This section introduces id-it-certProfile.
Insert this section after
Section 5.1.1.2 of
RFC 4210:
5.1.1.3. CertProfile
This is used by the EE to indicate specific certificate profiles, e.g., when requesting a new certificate or a certificate request template; see Section 5.3.19.16.
id-it-certProfile OBJECT IDENTIFIER ::= {id-it 21}
CertProfileValue ::= SEQUENCE SIZE (1..MAX) OF UTF8String
When used in an ir/cr/kur/genm, the value
MUST NOT contain more elements than the number of CertReqMsg or InfoTypeAndValue elements and the certificate profile names refer to the elements in the given order.
When used in a p10cr, the value
MUST NOT contain multiple certificate profile names.
Section 5.1.3.1 of
RFC 4210 describes the protection of a PKIMessage based on message authentication code (MAC) using the algorithm id-PasswordBasedMac.
Replace the first paragraph with the following text:
In this case, the sender and recipient share secret information with sufficient entropy (established via out-of-band means or from a previous PKI management operation). PKIProtection will contain a MAC value and the protectionAlg
MAY be one of the options described in [
RFC 9481]. The PasswordBasedMac is specified as follows (see also [
RFC 4211] and [
RFC 9045]):
Replace the last paragraph with the following text (Note: This fixes Errata ID 2616):
Note: It is
RECOMMENDED that the fields of PBMParameter remain constant throughout the messages of a single transaction (e.g., ir/ip/certConf/pkiConf) to reduce the overhead associated with PasswordBasedMac computation.
Section 5.1.3.4 of
RFC 4210 describes the nested message. This document also enables using nested messages for batch-delivery transport of PKI messages between PKI management entities and with mixed body types.
Replace the text of the section with the following text:
5.1.3.4. Multiple Protection
When receiving a protected PKI message, a PKI management entity, such as an RA,
MAY forward that message along with adding its own protection (which is a MAC or a signature, depending on the information and certificates shared between the RA and the CA). Additionally, multiple PKI messages
MAY be aggregated. There are several use cases for such messages.
-
The RA confirms having validated and authorized a message and forwards the original message unchanged.
-
The RA modifies the message(s) in some way (e.g., adds or modifies particular field values or adds new extensions) before forwarding them; then, it MAY create its own desired PKIBody. If the changes made by the RA to PKIMessage break the POP of a certificate request, the RA MUST set the popo field to RAVerified. It MAY include the original PKIMessage from the EE in the generalInfo field of PKIHeader of a nested message (to accommodate, for example, cases in which the CA wishes to check POP or other information on the original EE message). The infoType to be used in this situation is {id-it 15} (see Section 5.3.19 for the value of id-it), and the infoValue is PKIMessages (contents MUST be in the same order as the message in PKIBody).
-
A PKI management entity collects several messages that are to be forwarded in the same direction and forwards them in a batch. Request messages can be transferred as batch upstream (towards the CA); response or announce messages can be transferred as batch downstream (towards an RA but not to the EE). For instance, this can be used when bridging an off-line connection between two PKI management entities.
These use cases are accomplished by nesting the messages within a new PKI message. The structure used is as follows:
NestedMessageContent ::= PKIMessages
Section 5.2.2 of
RFC 4210 describes the use of EncryptedValue to transport encrypted data. This document extends the encryption of data to preferably use EnvelopedData.
Replace the text of the section with the following text:
5.2.2. Encrypted Values
Where encrypted data (in this specification, private keys, certificates, or revocation passphrase) is sent in PKI messages, the EncryptedKey data structure is used.
EncryptedKey ::= CHOICE {
encryptedValue EncryptedValue, -- deprecated
envelopedData [0] EnvelopedData }
See [
RFC 4211] for EncryptedKey and EncryptedValue syntax and [
RFC 5652] for EnvelopedData syntax. Using the EncryptedKey data structure offers the choice to either use EncryptedValue (for backward compatibility only) or EnvelopedData. The use of the EncryptedValue structure has been deprecated in favor of the EnvelopedData structure. Therefore, it is
RECOMMENDED to use EnvelopedData.
Note: The EncryptedKey structure defined in [
RFC 4211] is reused here, which makes the update backward compatible. Using the new syntax with the untagged default choice EncryptedValue is bits-on-the-wire compatible with the old syntax.
To indicate support for EnvelopedData, the pvno cmp2021 has been introduced. Details on the usage of the protocol version number (pvno) are described in Section
7.
The EncryptedKey data structure is used in CMP to transport a private key, certificate, or revocation passphrase in encrypted form.
EnvelopedData is used as follows:
-
It contains only one RecipientInfo structure because the content is encrypted only for one recipient.
-
It may contain a private key in the AsymmetricKeyPackage structure, as defined in [RFC 5958], that is wrapped in a SignedData structure, as specified in Section 5 of RFC 5652 and [RFC 8933], and signed by the Key Generation Authority.
-
It may contain a certificate or revocation passphrase directly in the encryptedContent field.
The content of the EnvelopedData structure, as specified in
Section 6 of
RFC 5652,
MUST be encrypted using a newly generated symmetric content-encryption key. This content-encryption key
MUST be securely provided to the recipient using one of three key management techniques.
The choice of the key management technique to be used by the sender depends on the credential available at the recipient:
-
recipient's certificate with an algorithm identifier and a public key that supports key transport and where any given key usage extension allows keyEncipherment: The content-encryption key will be protected using the key transport key management technique, as specified in Section 6.2.1 of RFC 5652.
-
recipient's certificate with an algorithm identifier and a public key that supports key agreement and where any given key usage extension allows keyAgreement: The content-encryption key will be protected using the key agreement key management technique, as specified in Section 6.2.2 of RFC 5652.
-
a password or shared secret: The content-encryption key will be protected using the password-based key management technique, as specified in Section 6.2.4 of RFC 5652.
Section 5.3.4 of
RFC 4210 describes the Certification Response. This document updates the syntax by using the parent structure EncryptedKey instead of EncryptedValue, as described in
Section 2.7 above. Additionally, it clarifies the certReqId to be used in response to a p10cr message.
Replace the ASN.1 syntax with the following text (Note: This also fixes Errata ID 3949 and 4078):
CertRepMessage ::= SEQUENCE {
caPubs [1] SEQUENCE SIZE (1..MAX) OF CMPCertificate
OPTIONAL,
response SEQUENCE OF CertResponse
}
CertResponse ::= SEQUENCE {
certReqId INTEGER,
status PKIStatusInfo,
certifiedKeyPair CertifiedKeyPair OPTIONAL,
rspInfo OCTET STRING OPTIONAL
-- analogous to the id-regInfo-utf8Pairs string defined
-- for regInfo in CertReqMsg [RFC4211]
}
CertifiedKeyPair ::= SEQUENCE {
certOrEncCert CertOrEncCert,
privateKey [0] EncryptedKey OPTIONAL,
-- See [RFC4211] for comments on encoding.
publicationInfo [1] PKIPublicationInfo OPTIONAL
}
CertOrEncCert ::= CHOICE {
certificate [0] CMPCertificate,
encryptedCert [1] EncryptedKey
}
Add the following as a new paragraph right after the ASN.1 syntax:
A p10cr message contains exactly one CertificationRequestInfo data structure, as specified in [
RFC 2986], but no certReqId. Therefore, the certReqId in the corresponding Certification Response (cp) message
MUST be set to -1.
Add the following as new paragraphs to the end of the section:
The use of EncryptedKey is described in Section
5.2.2.
Note: To indicate support for EnvelopedData, the pvno cmp2021 has been introduced. Details on the usage of different protocol version numbers (pvno) are described in Section
7.
This section introduces an optional hashAlg field to the CertStatus type used in certConf messages to explicitly specify the hash algorithm for those certificates where no hash algorithm is specified in the signatureAlgorithm field.
Replace the ASN.1 Syntax of CertStatus with the following text:
CertStatus ::= SEQUENCE {
certHash OCTET STRING,
certReqId INTEGER,
statusInfo PKIStatusInfo OPTIONAL,
hashAlg [0] AlgorithmIdentifier{DIGEST-ALGORITHM, {...}}
OPTIONAL
}
The hashAlg field
SHOULD be used only in exceptional cases where the signatureAlgorithm of the certificate to be confirmed does not specify a hash algorithm in the OID or in the parameters. In such cases, e.g., for EdDSA, the hashAlg
MUST be used to specify the hash algorithm to be used for calculating the certHash value. Otherwise, the certHash value
SHALL be computed using the same hash algorithm as used to create and verify the certificate signature. If hashAlg is used, the CMP version indicated by the certConf message header must be cmp2021(3).
The following section clarifies the usage of the Signing Key Pair Types on referencing elliptic curves.
Insert this note at the end of
Section 5.3.19.2 of
RFC 4210:
Note: In case several elliptic curves are supported, several id-ecPublicKey elements as defined in [
RFC 5480] need to be given, one per named curve.
The following section clarifies the use of the Encryption/Key Agreement Key Pair Types on referencing elliptic curves.
Insert this note at the end of
Section 5.3.19.3 of
RFC 4210:
Note: In case several elliptic curves are supported, several id-ecPublicKey elements as defined in [
RFC 5480] need to be given, one per named curve.
Section 5.3.19.9 of
RFC 4210 describes the provisioning of a revocation passphrase for authenticating a later revocation request. This document updates the handling by using the parent structure EncryptedKey instead of EncryptedValue to transport this information, as described in
Section 2.7 above.
Replace the text of the section with the following text:
5.3.19.9. Revocation Passphrase
This
MAY be used by the EE to send a passphrase to a CA/RA for the purpose of authenticating a later revocation request (in the case that the appropriate signing private key is no longer available to authenticate the request). See Appendix
B for further details on the use of this mechanism.
GenMsg: {id-it 12}, EncryptedKey
GenRep: {id-it 12}, < absent >
The use of EncryptedKey is described in Section
5.2.2.
The following subsection describes PKI general messages using id-it-caCerts. The intended use is specified in
Section 4.3 of
RFC 9483.
Insert this section after
Section 5.3.19.13 of
RFC 4210:
5.3.19.14. CA Certificates
This
MAY be used by the client to get CA certificates.
GenMsg: {id-it 17}, < absent >
GenRep: {id-it 17}, SEQUENCE SIZE (1..MAX) OF
CMPCertificate | < absent >
The following subsection describes PKI general messages using id-it-rootCaCert and id-it-rootCaKeyUpdate. The use is specified in
Section 4.3 of
RFC 9483.
Insert this section after the new Section 5.3.19.14:
5.3.19.15. Root CA Certificate Update
This
MAY be used by the client to get an update of a root CA certificate, which is provided in the body of the request message. In contrast to the ckuann message, this approach follows the request/response model.
The EE
SHOULD reference its current trust anchor in a TrustAnchor structure in the request body, giving the root CA certificate if available; otherwise, the public key value of the trust anchor is given.
GenMsg: {id-it 20}, RootCaCertValue | < absent >
GenRep: {id-it 18}, RootCaKeyUpdateContent | < absent >
RootCaCertValue ::= CMPCertificate
RootCaKeyUpdateValue ::= RootCaKeyUpdateContent
RootCaKeyUpdateContent ::= SEQUENCE {
newWithNew CMPCertificate,
newWithOld [0] CMPCertificate OPTIONAL,
oldWithNew [1] CMPCertificate OPTIONAL
}
Note: In contrast to CAKeyUpdAnnContent, this type offers omitting newWithOld and oldWithNew in the GenRep message, depending on the needs of the EE.
The following subsection introduces the PKI general message using id-it-certReqTemplate. Details are specified in
Section 4.3 of
RFC 9483.
Insert this section after the new Section 5.3.19.15:
5.3.19.16. Certificate Request Template
This
MAY be used by the client to get a template containing requirements for certificate request attributes and extensions. The controls id-regCtrl-algId and id-regCtrl-rsaKeyLen
MAY contain details on the types of subject public keys the CA is willing to certify.
The id-regCtrl-algId control
MAY be used to identify a cryptographic algorithm (see
Section 4.1.2.7 of
RFC 5280) other than rsaEncryption. The algorithm field
SHALL identify a cryptographic algorithm. The contents of the optional parameters field will vary according to the algorithm identified. For example, when the algorithm is set to id-ecPublicKey, the parameters identify the elliptic curve to be used; see [
RFC 5480].
The id-regCtrl-rsaKeyLen control
SHALL be used for algorithm rsaEncryption and
SHALL contain the intended modulus bit length of the RSA key.
GenMsg: {id-it 19}, < absent >
GenRep: {id-it 19}, CertReqTemplateContent | < absent >
CertReqTemplateValue ::= CertReqTemplateContent
CertReqTemplateContent ::= SEQUENCE {
certTemplate CertTemplate,
keySpec Controls OPTIONAL }
Controls ::= SEQUENCE SIZE (1..MAX) OF AttributeTypeAndValue
id-regCtrl-algId OBJECT IDENTIFIER ::= { iso(1)
identified-organization(3) dod(6) internet(1) security(5)
mechanisms(5) pkix(7) pkip(5) regCtrl(1) 11 }
AlgIdCtrl ::= AlgorithmIdentifier{ALGORITHM, {...}}
id-regCtrl-rsaKeyLen OBJECT IDENTIFIER ::= { iso(1)
identified-organization(3) dod(6) internet(1) security(5)
mechanisms(5) pkix(7) pkip(5) regCtrl(1) 12 }
RsaKeyLenCtrl ::= INTEGER (1..MAX)
The CertReqTemplateValue contains the prefilled certTemplate to be used for a future certificate request. The publicKey field in the certTemplate
MUST NOT be used. In case the PKI management entity wishes to specify supported public-key algorithms, the keySpec field
MUST be used. One AttributeTypeAndValue per supported algorithm or RSA key length
MUST be used.
Note: The controls ASN.1 type is defined in
Section 6 of
RFC 4211.
The following subsection introduces the PKI general message using id-it-crlStatusList and id-it-crls. Details are specified in
Section 4.3 of
RFC 9483. Insert this section after the new Section 5.3.19.16:
5.3.19.17. CRL Update Retrieval
This
MAY be used by the client to get new CRLs, specifying the source of the CRLs and the thisUpdate value of the latest CRL it already has, if available. A CRL source is given either by a DistributionPointName or the GeneralNames of the issuing CA. The DistributionPointName should be treated as an internal pointer to identify a CRL that the server already has and not as a way to ask the server to fetch CRLs from external locations. The server shall only provide those CRLs that are more recent than the ones indicated by the client.
GenMsg: {id-it 22}, SEQUENCE SIZE (1..MAX) OF CRLStatus
GenRep: {id-it 23}, SEQUENCE SIZE (1..MAX) OF
CertificateList | < absent >
CRLSource ::= CHOICE {
dpn [0] DistributionPointName,
issuer [1] GeneralNames }
CRLStatus ::= SEQUENCE {
source CRLSource,
thisUpdate Time OPTIONAL }
Section 5.3.21 of
RFC 4210 describes the regular use of error messages. This document adds a use by a PKI management entity to initiate delayed delivery in response to certConf, rr, and genm requests and to error messages.
Replace the first sentence of the first paragraph with the following one:
This data structure
MAY be used by an EE, CA, or RA to convey error information and by a PKI management entity to initiate delayed delivery of responses.
Replace the second paragraph with the following text:
This message
MAY be generated at any time during a PKI transaction. If the client sends this request, the server
MUST respond with a PKIConfirm response or another ErrorMsg if any part of the header is not valid. In case a PKI management entity sends an error message to the EE with the pKIStatusInfo field containing the status "waiting", the EE will initiate polling as described in Section
5.3.22. Otherwise, both sides
MUST treat this message as the end of the transaction (if a transaction is in progress).
Section 5.3.22 of
RFC 4210 describes when and how polling messages are used for ir, cr, and kur messages. This document extends the polling mechanism for outstanding responses to any kind of request message. This update also fixes the inconsistent use of the terms 'pReq' vs. 'pollReq' and 'pRep' vs. 'pollRep'.
Replace
Section 5.3.22 of
RFC 4210 with following text:
This pair of messages is intended to handle scenarios in which the client needs to poll the server to determine the status of an outstanding response (i.e., when the "waiting" PKIStatus has been received).
PollReqContent ::= SEQUENCE OF SEQUENCE {
certReqId INTEGER }
PollRepContent ::= SEQUENCE OF SEQUENCE {
certReqId INTEGER,
checkAfter INTEGER, -- time in seconds
reason PKIFreeText OPTIONAL }
In response to an ir, cr, p10cr, or kur request message, polling is initiated with an ip, cp, or kup response message containing status "waiting". For any type of request message, polling can be initiated with an error response messages with status "waiting". The following clauses describe how polling messages are used. It is assumed that multiple certConf messages can be sent during transactions. There will be one sent in response to each ip, cp, or kup that contains a CertStatus for an issued certificate.
- 1
- In response to an ip, cp, or kup message, an EE will send a certConf for all issued certificates and expect a PKIconf for each certConf. An EE will send a pollReq message in response to each CertResponse element of an ip, cp, or kup message with status "waiting" and in response to an error message with status "waiting". Its certReqId MUST be either the index of a CertResponse data structure with status "waiting" or -1, referring to the complete response.
- 2
- In response to a pollReq, a CA/RA will return an ip, cp, or kup if one or more of the still pending requested certificates are ready or the final response to some other type of request is available; otherwise, it will return a pollRep.
- 3
- If the EE receives a pollRep, it will wait for at least the number of seconds given in the checkAfter field before sending another pollReq.
- 4
- If the EE receives an ip, cp, or kup, then it will be treated in the same way as the initial response; if it receives any other response, then this will be treated as the final response to the original request.
The following client-side state machine describes polling for individual CertResponse elements.
START
|
v
Send ir
| ip
v
Check status
of returned <------------------------+
certs |
| |
+------------------------>|<------------------+ |
| | | |
| (issued) v (waiting) | |
Add to <----------- Check CertResponse ------> Add to |
conf list for each certificate pending list |
/ |
/ |
(conf list) / (empty conf list) |
/ ip |
/ +-----------------+
(empty pending list) / | pollRep
END <---- Send certConf Send pollReq---------->Wait
| ^ ^ |
| | | |
+-----------------+ +---------------+
(pending list)
In the following exchange, the end entity is enrolling for two certificates in one request.
Step End Entity PKI
--------------------------------------------------------------------
1 Format ir
2 -> ir ->
3 Handle ir
4 Manual intervention is
required for both certs
5 <- ip <-
6 Process ip
7 Format pollReq
8 -> pollReq ->
9 Check status of cert requests
10 Certificates not ready
11 Format pollRep
12 <- pollRep <-
13 Wait
14 Format pollReq
15 -> pollReq ->
16 Check status of cert requests
17 One certificate is ready
18 Format ip
19 <- ip <-
20 Handle ip
21 Format certConf
22 -> certConf ->
23 Handle certConf
24 Format ack
25 <- pkiConf <-
26 Format pollReq
27 -> pollReq ->
28 Check status of certificate
29 Certificate is ready
30 Format ip
31 <- ip <-
31 Handle ip
32 Format certConf
33 -> certConf ->
34 Handle certConf
35 Format ack
36 <- pkiConf <-
The following client-side state machine describes polling for a complete response message.
Start
|
| Send request
|
+----------- Receive response ------------+
| |
| ip/cp/kup/error with | other
| status "waiting" | response
| |
v |
+------> Polling |
| | |
| | Send pollReq |
| | Receive response |
| | |
| pollRep | other response |
+-----------+------------------->+<-------------------+
|
v
Handle response
|
v
End
In the following exchange, the end entity is sending a general message request, and the response is delayed by the server.
Step End Entity PKI
--------------------------------------------------------------------
1 Format genm
2 -> genm ->
3 Handle genm
4 delay in response is necessary
5 Format error message "waiting"
with certReqId set to -1
6 <- error <-
7 Process error
8 Format pollReq
9 -> pollReq ->
10 Check status of original request
general message response not ready
11 Format pollRep
12 <- pollRep <-
13 Wait
14 Format pollReq
15 -> pollReq ->
16 Check status of original request
general message response is ready
17 Format genp
18 <- genp <-
19 Handle genp
Section 7 of
RFC 4210 describes the use of CMP versions. This document describes the handling of the additional CMP version cmp2021, which is introduced to indicate support of EnvelopedData and hashAlg.
Replace the text of the second paragraph with the following text:
If a client knows the protocol version(s) supported by the server (e.g., from a previous PKIMessage exchange or via some out-of-band means), then it
MUST send a PKIMessage with the highest version supported by both it and the server. If a client does not know what version(s) the server supports, then it
MUST send a PKIMessage using the highest version it supports with the following exception. Version cmp2021
SHOULD only be used if cmp2021 syntax is needed for the request being sent or for the expected response.
Note: Using cmp2000 as the default pvno is done to avoid extra message exchanges for version negotiation and to foster compatibility with cmp2000 implementations. Version cmp2021 syntax is only needed if a message exchange uses hashAlg (in CertStatus) or EnvelopedData.
Section 7.1.1 of
RFC 4210 describes the behavior of a client sending a cmp2000 message talking to a cmp1999 server, as specified in [
RFC 2510]. This document extends the section to clients with any higher version than cmp1999.
Replace the first sentence of
Section 7.1.1 of
RFC 4210 with the following text:
If, after sending a message with a protocol version number higher than cmp1999, a client receives an ErrorMsgContent with a version of cmp1999, then it
MUST abort the current transaction.
The following subsection addresses the risk arising from reusing the CA private key for CMP message protection.
Insert this section after
Section 8.3 of
RFC 4210 (Note: This fixes Errata ID 5731):
8.4. Private Keys for Certificate Signing and CMP Message Protection
A CA should not reuse its certificate signing key for other purposes, such as protecting CMP responses and TLS connections. This way, exposure to other parts of the system and the number of uses of this particularly critical key are reduced to a minimum.
The following subsection addresses the risk arising from low entropy of random numbers, asymmetric keys, and shared secret information.
Insert this section after the new Section 8.4:
8.5. Entropy of Random Numbers, Key Pairs, and Shared Secret Information
Implementations must generate nonces and private keys from random input. The use of inadequate pseudorandom number generators (PRNGs) to generate cryptographic keys can result in little or no security. An attacker may find it much easier to reproduce the PRNG environment that produced the keys and to search the resulting small set of possibilities than brute-force searching the whole key space. As an example of predictable random numbers, see [
CVE-2008-0166]; consequences of low-entropy random numbers are discussed in [
MiningPsQs]. The generation of quality random numbers is difficult. [
ISO.20543-2019], [
NIST_SP_800_90Ar1], [
AIS31], and other specifications offer valuable guidance in this area.
If shared secret information is generated by a cryptographically secure random number generator (CSRNG), it is safe to assume that the entropy of the shared secret information equals its bit length. If no CSRNG is used, the entropy of shared secret information depends on the details of the generation process and cannot be measured securely after it has been generated. If user-generated passwords are used as shared secret information, their entropy cannot be measured and are typically insufficient for protected delivery of centrally generated keys or trust anchors.
If the entropy of shared secret information protecting the delivery of a centrally generated key pair is known, it should not be less than the security strength of that key pair; if the shared secret information is reused for different key pairs, the security of the shared secret information should exceed the security strength of each individual key pair.
For the case of a PKI management operation that delivers a new trust anchor (e.g., a root CA certificate) using caPubs or genm that is (a) not concluded in a timely manner or (b) where the shared secret information is reused for several key management operations, the entropy of the shared secret information, if known, should not be less than the security strength of the trust anchor being managed by the operation. The shared secret information should have an entropy that at least matches the security strength of the key material being managed by the operation. Certain use cases may require shared secret information that may be of a low security strength, e.g., a human-generated password. It is
RECOMMENDED that such secret information be limited to a single PKI management operation.
The following subsection addresses the risk arising from in-band provisioning of new trust anchors in a PKI management operation.
Insert this section after the new Section 8.5:
8.6. Trust Anchor Provisioning Using CMP Messages
A provider of trust anchors, which may be an RA involved in configuration management of its clients,
MUST NOT include to-be-trusted CA certificates in a CMP message unless the specific deployment scenario can ensure that it is adequate that the receiving EE trusts these certificates, e.g., by loading them into its trust store.
Whenever an EE receives in a CMP message a CA certificate to be used as a trust anchor (for example in the caPubs field of a certificate response or in a general response), it
MUST properly authenticate the message sender with existing trust anchor information without requiring the new trust anchors included in the message.
Additionally, the EE
MUST verify that the sender is an authorized source of trust anchors. This authorization is governed by local policy and typically indicated using shared secret information or with a signature-based message protection using a certificate issued by a PKI that is explicitly authorized for this purpose.
The following subsection addresses the security considerations to follow when authorizing requests for certificates containing specific EKUs.
Insert this section after new Section 8.6:
8.7. Authorizing Requests for Certificates with Specific EKUs
When a CA issues a certificate containing extended key usage extensions as defined in Section 4.5, this expresses delegation of an authorization that originally is only with the CA certificate itself. Such delegation is a very sensitive action in a PKI and therefore special care must be taken when approving such certificate requests to ensure that only legitimate entities receive a certificate containing such an EKU.
Appendix B of
RFC 4210 describes the use of the revocation passphrase. As this document updates [
RFC 4210] to utilize the parent structure EncryptedKey instead of EncryptedValue as described in
Section 2.7 above, the description is updated accordingly.
Replace the first bullet point of this section with the following text:
-
The OID and value specified in Section 5.3.19.9 MAY be sent in a GenMsg message at any time or MAY be sent in the generalInfo field of the PKIHeader of any PKIMessage at any time. (In particular, the EncryptedKey structure as described in Section 5.2.2 may be sent in the header of the certConf message that confirms acceptance of certificates requested in an initialization request or certificate request message.) This conveys a revocation passphrase chosen by the entity to the relevant CA/RA. When EnvelopedData is used, this is in the decrypted bytes of the encryptedContent field. When EncryptedValue is used, this is in the decrypted bytes of the encValue field. Furthermore, the transfer is accomplished with appropriate confidentiality characteristics.
Replace the third bullet point of this section with the following text:
-
Either the localKeyId attribute of EnvelopedData as specified in [RFC 2985] or the valueHint field of EncryptedValue MAY contain a key identifier (chosen by the entity, along with the passphrase itself) to assist in later retrieval of the correct passphrase (e.g., when the revocation request is constructed by the entity and received by the CA/RA).
Appendix C of
RFC 4210 provides clarifications to the request message behavior. As this document updates [
RFC 4210] to utilize the parent structure EncryptedKey instead of EncryptedValue as described in
Section 2.7 above, the description is updated accordingly.
Replace the comment within the ASN.1 syntax coming after the definition of POPOSigningKey with the following text (Note: This fixes Errata ID 2615):
-- **********
-- * For the purposes of this specification, the ASN.1 comment
-- * given in [RFC4211] pertains not only to certTemplate but
-- * also to the altCertTemplate control.
-- **********
-- * The signature (using "algorithmIdentifier") is on the
-- * DER-encoded value of poposkInput (i.e., the "value" OCTETs
-- * of the POPOSigningKeyInput DER). NOTE: If CertReqMsg
-- * certReq certTemplate (or the altCertTemplate control)
-- * contains the subject and publicKey values, then poposkInput
-- * MUST be omitted and the signature MUST be computed on the
-- * DER-encoded value of CertReqMsg certReq (or the DER-
-- * encoded value of AltCertTemplate). If
-- * certTemplate/altCertTemplate does not contain both the
-- * subject and public key values (i.e., if it contains only
-- * one of these or neither), then poposkInput MUST be present
-- * and MUST be signed.
-- **********
Replace the ASN.1 syntax of POPOPrivKey with the following text:
POPOPrivKey ::= CHOICE {
thisMessage [0] BIT STRING, -- deprecated
subsequentMessage [1] SubsequentMessage,
dhMAC [2] BIT STRING, -- deprecated
agreeMAC [3] PKMACValue,
encryptedKey [4] EnvelopedData }
-- **********
-- * When using CMP V2, the encrypted value MUST be transferred in
-- * the thisMessage field that is given as BIT STRING in [RFC4211],
-- * but it requires EncryptedValue. Therefore, this document makes
-- * the behavioral clarification for CMP V2 of specifying that the
-- * contents of "thisMessage" MUST be encoded as an
-- * EncryptedValue and then wrapped in a BIT STRING.
-- * When using CMP V3, the encrypted value MUST be transferred
-- * in the encryptedKey field, as specified in Section 5.2.2.
-- **********
Appendix D.1 of
RFC 4210 provides general rules for interpretation of the PKI management messages profiles specified in Appendices
D and
E of [
RFC 4210]. This document updates a sentence regarding the new protocol version cmp2021.
Replace the last sentence of the first paragraph of the section with the following text:
Mandatory fields are not mentioned if they have an obvious value (e.g., in this version of these profiles, pvno is always cmp2000).
Appendix D.2 of
RFC 4210 provides a list of algorithms that implementations must support when claiming conformance with PKI management message profiles, as specified in
Appendix D.2 of
RFC 4210. This document redirects to the new algorithm profile, as specified in
Section 7.1 of
RFC 9481.
Replace the text of the section with the following text:
D.2. Algorithm Use Profile
For specifications of algorithm identifiers and respective conventions for conforming implementations, please refer to
Section 7.1 of
RFC 9481.
Appendix D.4 of
RFC 4210 provides the initial registration/certification scheme. This scheme shall continue using EncryptedValue for backward compatibility reasons.
Replace the line specifying protectionAlg of the Initialization Response message with the following text (Note: This fixes Errata ID 5201):
protectionAlg MSG_MAC_ALG
Replace the comment after the privateKey field of crc[1].certifiedKeyPair in the syntax of the Initialization Response message with the following text:
-- see Appendix C (Request Message Behavioral Clarifications)
-- for backward compatibility reasons, use EncryptedValue