rfc9925v1.md   rfc9925.md 
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{{Section 4.1.2.4 of !RFC5280}} forbid empty issuers, so such a value may not be {{Section 4.1.2.4 of !RFC5280}} forbid empty issuers, so such a value may not be
interoperable with existing applications. interoperable with existing applications.
If the subject is not empty, senders MAY set the issuer to the subject, similar If the subject is not empty, senders MAY set the issuer to the subject, similar
to how they would construct a self-signed certificate. to how they would construct a self-signed certificate.
This may be useful in applications that, for example, This may be useful in applications that, for example,
expect trust anchors to have a matching issuer and subject. This is, however, a expect trust anchors to have a matching issuer and subject. This is, however, a
placeholder value. The unsigned certificate is not considered self-signed or placeholder value. The unsigned certificate is not considered self-signed or
self-issued. self-issued.
<!--[rfced] For clarity, may we update the latter part of this sentence
as follows?
Original:
Senders MAY alternatively use a short placeholder issuer consisting
of a single relative distinguished name, with a single attribute of
type id-rdna-unsigned and value a zero-length UTF8String.
Perhaps:
Senders MAY alternatively use a short placeholder issuer consisting
of a single relative distinguished name that has a single attribute of
type id-rdna-unsigned and a value with a zero-length UTF8String.
Senders MAY alternatively use a short placeholder issuer consisting of a single Senders MAY alternatively use a short placeholder issuer consisting of a single
relative distinguished name, with a single attribute of type id-rdna-unsigned relative distinguished name that has a single attribute with a type of id-rdna-unsign
and value a zero-length UTF8String. id-rdna-unsigned is defined as follows: ed
and value of a zero-length UTF8String. id-rdna-unsigned is defined as follows:
~~~ ~~~
id-rdna-unsigned OBJECT IDENTIFIER ::= {1 3 6 1 5 5 7 25 1} id-rdna-unsigned OBJECT IDENTIFIER ::= {1 3 6 1 5 5 7 25 1}
~~~ ~~~
This placeholder name, in the string representation of {{?RFC4514}}, is: This placeholder name, in the string representation of {{?RFC4514}}, is:
~~~ ~~~
1.3.6.1.5.5.7.25.1=#0C00 1.3.6.1.5.5.7.25.1=#0C00
~~~ ~~~
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and already forbidden by {{Section 4.1.2.8 of !RFC5280}}. and already forbidden by {{Section 4.1.2.8 of !RFC5280}}.
## Extensions ## Extensions
Some X.509 extensions also describe the certificate issuer and thus are not Some X.509 extensions also describe the certificate issuer and thus are not
meaningful for an unsigned certificate: meaningful for an unsigned certificate:
* authority key identifier ({{Section 4.2.1.1 of !RFC5280}}) * authority key identifier ({{Section 4.2.1.1 of !RFC5280}})
* issuer alternative name ({{Section 4.2.1.7 of !RFC5280}}) * issuer alternative name ({{Section 4.2.1.7 of !RFC5280}})
<!--[rfced] To improve readability and avoid the repetition of "include" and
"includes", may we update this sentence as follows?
Original:
Section 4.2.1.1 of [RFC5280] requires
certificates to include the authority key identifier, but includes an
exception for self-signed certificates used when distributing a
public key.
Perhaps:
Section 4.2.1.1 of [RFC5280] requires
certificates to include the authority key identifier, but it also describes an
exception for self-signed certificates used when distributing a
public key.
Senders SHOULD omit the authority key identifier and issuer alternative name Senders SHOULD omit the authority key identifier and issuer alternative name
extensions. {{Section 4.2.1.1 of !RFC5280}} requires certificates to include extensions. {{Section 4.2.1.1 of !RFC5280}} requires certificates to include
the authority key identifier, but includes an exception for self-signed certificates the authority key identifier, but it permits an exception for self-signed certificate s
used when distributing a public key. This document updates {{!RFC5280}} to also used when distributing a public key. This document updates {{!RFC5280}} to also
permit omitting the authority key identifier in unsigned certificates. permit omitting the authority key identifier in unsigned certificates.
Some extensions reflect whether the subject is a CA or an end entity: Some extensions reflect whether the subject is a CA or an end entity:
* key usage ({{Section 4.2.1.3 of !RFC5280}}) * key usage ({{Section 4.2.1.3 of !RFC5280}})
* basic constraints ({{Section 4.2.1.9 of !RFC5280}}) * basic constraints ({{Section 4.2.1.9 of !RFC5280}})
<!--[rfced] FYI - We've reformatted the following text into an unordered
list. Please review and let us know of any objections.
Original:
Senders SHOULD fill in these values to reflect the subject. That is:
If the subject is a CA, it SHOULD assert the keyCertSign key usage
bit and SHOULD include a basic constraints extensions that sets the
cA boolean to TRUE.
If the subject is an end entity, it SHOULD NOT assert the keyCertSign
key usage bit, and it SHOULD either omit the basic constraints
extension or set the cA boolean to FALSE. Unlike a self-signed
certificate, an unsigned certificate does not issue itself, so there
is no need to accommodate a self-signature in either extension.
Current:
Senders SHOULD fill in these values to reflect the subject. That is:
* If the subject is a CA, it SHOULD assert the keyCertSign key usage
bit and SHOULD include a basic constraints extension that sets
the cA boolean to TRUE.
* If the subject is an end entity, it SHOULD NOT assert the
keyCertSign key usage bit, and it SHOULD either omit the basic
constraints extension or set the cA boolean to FALSE. Unlike a
self-signed certificate, an unsigned certificate does not issue
itself, so there is no need to accommodate a self-signature in
either extension.
Senders SHOULD fill in these values to reflect the subject. That is: Senders SHOULD fill in these values to reflect the subject. That is:
* If the subject is a CA, it SHOULD assert the keyCertSign key usage bit and * If the subject is a CA, it SHOULD assert the keyCertSign key usage bit and
SHOULD include a basic constraints extension that sets the cA boolean to TRUE. SHOULD include a basic constraints extension that sets the cA boolean to TRUE.
* If the subject is an end entity, it SHOULD NOT assert the keyCertSign key usage * If the subject is an end entity, it SHOULD NOT assert the keyCertSign key usage
bit, and it SHOULD either omit the basic constraints extension or set the cA bit, and it SHOULD either omit the basic constraints extension or set the cA
boolean to FALSE. Unlike a self-signed certificate, an unsigned certificate does boolean to FALSE. Unlike a self-signed certificate, an unsigned certificate does
not issue itself, so there is no need to accommodate a self-signature in either not issue itself, so there is no need to accommodate a self-signature in either
extension. extension.
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reuse by removing the X.509 self-signature. reuse by removing the X.509 self-signature.
If an application accepts id-alg-unsigned as part of a certification path, or If an application accepts id-alg-unsigned as part of a certification path, or
in any other context where it is necessary to verify the X.509 signature, the in any other context where it is necessary to verify the X.509 signature, the
signature check would be bypassed. Thus, {{consuming-unsigned-certificates}} signature check would be bypassed. Thus, {{consuming-unsigned-certificates}}
prohibits this and recommends that applications treat id-alg-unsigned the same prohibits this and recommends that applications treat id-alg-unsigned the same
as any other previously unrecognized signature algorithm. Non-compliant as any other previously unrecognized signature algorithm. Non-compliant
applications risk vulnerabilities analogous to those described in {{JWT}} and applications risk vulnerabilities analogous to those described in {{JWT}} and
{{Section 1.1 of ?I-D.ietf-jose-deprecate-none-rsa15}}. {{Section 1.1 of ?I-D.ietf-jose-deprecate-none-rsa15}}.
<!--[rfced] To improve readability, may we update "etc." to "for example"?
Original:
However, some applications might use
it as an integrity check to guard against accidental storage
corruption, etc.
Perhaps:
However, some applications might, for example, use
it as an integrity check to guard against accidental storage
corruption.
The signature in a self-signed certificate is self-derived and thus of limited The signature in a self-signed certificate is self-derived and thus of limited
use to convey trust. However, some applications might use it as an integrity use to convey trust. However, some applications might, for example, use it as an inte
check to guard against accidental storage corruption, etc. An unsigned grity
check to guard against accidental storage corruption. An unsigned
certificate does not provide any integrity check. Applications checking certificate does not provide any integrity check. Applications checking
self-signature for integrity SHOULD instead use some other mechanism, such as an self-signature for integrity SHOULD instead use some other mechanism, such as an
external hash that is verified out-of-band. external hash that is verified out-of-band.
# IANA Considerations # IANA Considerations
## Module Identifier ## Module Identifier
IANA has added the following entry in the "SMI Security for PKIX IANA has added the following entry in the "SMI Security for PKIX
Module Identifier" registry, defined by {{?RFC7299}}: Module Identifier" registry, defined by {{?RFC7299}}:
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|---------|------------------|------------| |---------|------------------|------------|
| 1 | id-rdna-unsigned | RFC 9925 | | 1 | id-rdna-unsigned | RFC 9925 |
Future updates to this table are to be made according to the Specification Future updates to this table are to be made according to the Specification
Required policy as defined in {{!RFC8126}}. Required policy as defined in {{!RFC8126}}.
--- back --- back
# ASN.1 Module # ASN.1 Module
<!--[rfced] We note that [RFC5912] is only cited in the ASN.1 module. This ASN.1 module uses the conventions established by [RFC5912].
In order to have a 1:1 matchup between the references section and the text,
please review the text and let us know where a citation may be included.
We suggest adding a sentence before the ASN.1 module to cite [RFC5912].
Perhaps:
This ASN.1 module uses the conventions established by [RFC5912].
~~~ asn.1 ~~~ asn.1
SignatureAlgorithmNone SignatureAlgorithmNone
{ iso(1) identified-organization(3) dod(6) internet(1) { iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0) security(5) mechanisms(5) pkix(7) id-mod(0)
id-mod-algUnsigned-2025(122) } id-mod-algUnsigned-2025(122) }
DEFINITIONS IMPLICIT TAGS ::= DEFINITIONS IMPLICIT TAGS ::=
BEGIN BEGIN
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END END
~~~ ~~~
# Acknowledgements # Acknowledgements
{:numbered="false"} {:numbered="false"}
Thanks to {{{Bob Beck}}}, {{{Nick Harper}}}, and {{{Sophie Schmieg}}} for reviewing a n early Thanks to {{{Bob Beck}}}, {{{Nick Harper}}}, and {{{Sophie Schmieg}}} for reviewing a n early
iteration of this document. Thanks to {{{Alex Gaynor}}} for providing a link to cite iteration of this document. Thanks to {{{Alex Gaynor}}} for providing a link to cite
for {{JWT}}. Thanks to {{{Russ Housley}}} for additional input. for {{JWT}}. Thanks to {{{Russ Housley}}} for additional input.
<!-- [rfced] FYI - We have added an expansion for the following abbreviation
per Section 3.6 of RFC 7322 ("RFC Style Guide"). Please review each
expansion in the document carefully to ensure correctness.
Key Encapsulation Mechanism (KEM)
<!-- [rfced] Please review the "Inclusive Language" portion of the online
Style Guide <https://www.rfc-editor.org/styleguide/part2/#inclusive_language>
and let us know if any changes are needed. Updates of this nature typically
result in more precise language, which is helpful for readers.
Note that our script did not flag any words in particular, but this should
still be reviewed as a best practice.
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