Internet Engineering Task Force S. Walter, Ed. Internet-Draft GNOME Intended status: BCP September 2010 Expires: March 5, 2011 Storing Trust Assertions in PKCS#11 Modules draft-walter-pkcs11-trust Abstract PKCS#11 is a standard that defines ways to store certificates, keys and perform crypto operations. It does not specify a way to store trust assertions. Trust assertions are used to assign an explicit level of trust to a certificate. Examples of trust assertions are certificate authority root certificates, certificate revocation lists, and certificate trust exceptions. This document outlines a way to store trust assertions with PKCS#11. This is not a new design, but documentation of the method already in use by libraries such as NSS. Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on March 5, 2011. Walter Expires March 5, 2011 [Page 1] Internet-Draft PKCS#11 Trust Assertions September 2010 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. PKCS#11 Primer . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 2. Trust Assertions . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Level of Trust . . . . . . . . . . . . . . . . . . . . . . 3 2.2. Usage or Purpose . . . . . . . . . . . . . . . . . . . . . 4 2.3. Certificate Reference . . . . . . . . . . . . . . . . . . 4 3. PKCS#11 Trust Assertion Objects . . . . . . . . . . . . . . . 4 4. Operations . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4.1. Checking Trust Assertions . . . . . . . . . . . . . . . . 7 4.1.1. Checking a Root Certificate Authority . . . . . . . . 7 4.1.2. Checking a Self-Signed Certificate . . . . . . . . . . 8 4.1.3. Checking an otherwise Trusted Certificate . . . . . . 8 4.2. Storing Trust Assertions . . . . . . . . . . . . . . . . . 8 4.3. Reading Trust Assertions . . . . . . . . . . . . . . . . . 8 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8 6. Further Considerations . . . . . . . . . . . . . . . . . . . . 9 7. Security Considerations . . . . . . . . . . . . . . . . . . . 9 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 8.1. Normative References . . . . . . . . . . . . . . . . . . . 9 8.2. Informative References . . . . . . . . . . . . . . . . . . 9 Appendix A. Additional Stuff . . . . . . . . . . . . . . . . . . 9 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 9 Intellectual Property and Copyright Statements . . . . . . . . . . 10 Walter Expires March 5, 2011 [Page 2] Internet-Draft PKCS#11 Trust Assertions September 2010 1. Introduction PKCS#11 is a useful and widely supported standard for storage and use of keys and certificates. It is often used with smart cards. 1.1. PKCS#11 Primer Xxxx 1.2. Terminology Xxxxx Xxxx The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119. 2. Trust Assertions A trust assertion describes a level of trust in an object for a given usage or purpose. Conceptually each trust assertion is a triple containing: o Certificate Reference o Usage or Purpose o Level of Trust We examine each of these parts of the triple in further detail below. 2.1. Level of Trust A trust assertion ultimately denotes a level of trust. These are: o Untrusted: The certificate is explicitly untrusted. o Unknown: The trust is not known and should be determined elsewhere. o Trusted: The certificate itself is explicitly trusted. o Trusted Delegator: The certificate is trusted as a certificate authority trust root. Trust is confers to certificates that this certificate has signed, or signed certificates have signed, and so on. Walter Expires March 5, 2011 [Page 3] Internet-Draft PKCS#11 Trust Assertions September 2010 2.2. Usage or Purpose A trust assertion always refers to a specific purpose or usage. A certificate may be trusted for purposes like: email, code signing, authenticating a server. 2.3. Certificate Reference Each trust assertion contains a reference to a certificate. There are two ways to refer to a certificate depending on whether that certificate is self-signed (like a certificate authority) or signed by another trusted certificate. Self-signed certificates are referred to by their complete hash of the DER value of the certificate. Certificates signed by another certificate are referred to by the DER value of the issuer field, and the serial number. Referring to a self-signed certificate by its issuer and serial number is meaningless. Referring to a signed certificate by its hash, would preclude uses such as certificate relocation lists, which do not contain certificates or enough information to generate a hash. Therefore different methods MUST be used to refer to self-signed and issuer-signed certificates. 3. PKCS#11 Trust Assertion Objects Trust assertions are stored as objects on a PKCS#11 token. Although these are specific to a certificate, they do not need to be stored on the same token as the certificate. Trust assertions objects are of the class CKO_NETSCAPE_TRUST and have the following attributes. Walter Expires March 5, 2011 [Page 4] Internet-Draft PKCS#11 Trust Assertions September 2010 Trust object attributes. +----------------------------+-----------------+--------------------+ | Attribute | Type | Description | +----------------------------+-----------------+--------------------+ | CKA_CLASS | CK_OBJECT_CLASS | CKO_NETSCAPE_TRUST | +----------------------------+-----------------+--------------------+ | CKA_ISSUER | Byte array | DER-encoding of | | | | the certificate | | | | issuer name | +----------------------------+-----------------+--------------------+ | CKA_SUBJECT | Byte array | DER-encoding of | | | | the certificate | | | | subject name. | | | | Optional, default | | | | empty | +----------------------------+-----------------+--------------------+ | CKA_SERIAL_NUMBER | Byte array | DER-encoding of | | | | the certificate | | | | serial number | +----------------------------+-----------------+--------------------+ | CKA_CERT_SHA1_HASH | Byte array | SHA1 hash of the | | | | the DER-encoding | | | | of certificate. | | | | Required for | | | | self-signed | | | | certificates. | +----------------------------+-----------------+--------------------+ | CKA_CERT_MD5_HASH | Byte array | MD5 hash of the | | | | the DER-encoding | | | | of certificate. | | | | Required for | | | | self-signed | | | | certificates. | +----------------------------+-----------------+--------------------+ | CKA_TRUST_SERVER_AUTH | CK_TRUST | Level of trust for | | | | server | | | | authentication | | | | extended usage. | +----------------------------+-----------------+--------------------+ | CKA_TRUST_CLIENT_AUTH | CK_TRUST | Level of trust for | | | | client | | | | authentication | | | | extended usage. | +----------------------------+-----------------+--------------------+ | CKA_TRUST_CODE_SIGNING | CK_TRUST | Level of trust for | | | | code signing | | | | extended usage. | Walter Expires March 5, 2011 [Page 5] Internet-Draft PKCS#11 Trust Assertions September 2010 | CKA_TRUST_EMAIL_PROTECTION | CK_TRUST | Level of trust for | | | | email protection | | | | extended usage. | +----------------------------+-----------------+--------------------+ | CKA_TRUST_IPSEC_END_SYSTEM | CK_TRUST | Level of trust for | | | | IPSEC end system | | | | extended usage. | +----------------------------+-----------------+--------------------+ | CKA_TRUST_IPSEC_TUNNEL | CK_TRUST | Level of trust for | | | | IPSEC tunnel | | | | extended usage. | +----------------------------+-----------------+--------------------+ | CKA_TRUST_IPSEC_USER | CK_TRUST | Level of trust for | | | | IPSEC user | | | | extended usage. | +----------------------------+-----------------+--------------------+ | CKA_TRUST_TIME_STAMPING | CK_TRUST | Level of trust for | | | | IPSEC time | | | | stamping extended | | | | usage. | +----------------------------+-----------------+--------------------+ | CKA_TRUST_DIGITAL_SIGNATUR | CK_TRUST | Level of trust for | | E | | digital signature | | | | key usage. | +----------------------------+-----------------+--------------------+ | CKA_TRUST_NON_REPUDIATION | CK_TRUST | Level of trust for | | | | non-repudiation | | | | key usage. | +----------------------------+-----------------+--------------------+ | CKA_TRUST_KEY_ENCIPHERMENT | CK_TRUST | Level of trust for | | | | key-encipherment | | | | key usage. | +----------------------------+-----------------+--------------------+ | CKA_TRUST_DATA_ENCIPHERMEN | CK_TRUST | Level of trust for | | T | | data-encipherment | | | | key usage. | +----------------------------+-----------------+--------------------+ | CKA_TRUST_KEY_AGREEMENT | CK_TRUST | Level of trust for | | | | key-agreement key | | | | usage. | +----------------------------+-----------------+--------------------+ | CKA_TRUST_KEY_CERT_SIGN | CK_TRUST | Level of trust for | | | | certificate | | | | signing key usage. | +----------------------------+-----------------+--------------------+ Walter Expires March 5, 2011 [Page 6] Internet-Draft PKCS#11 Trust Assertions September 2010 +----------------------------+-----------------+--------------------+ | CKA_TRUST_KEY_CRL_SIGN | CK_TRUST | Level of trust for | | | | crl signing key | | | | usage. | +----------------------------+-----------------+--------------------+ Xxxx: Possible additional attributes: CKA_TRUST_TYPE (CKT_CERTIFICATE_SELF_SIGNED, CKT_CERTIFICATE_SIGNED), CKA_CERT_SHA256_HASH Table 1: Trust Object Attributes CK_TRUST represenst a level of trust. +-----------------------+-------------------------------------------+ | Value | Description | +-----------------------+-------------------------------------------+ | CKT_UNTRUSTED | Explicitly untrusted. | | CKT_UNKNOWN | Trust is unknown and should be determined | | | elsewhere. | | CKT_TRUSTED | Explicitly trusts the certificate in the | | | assertion. | | CKT_TRUSTED_DELEGATOR | Trusts the certificate as a certificate | | | authority. | +-----------------------+-------------------------------------------+ Table 2: CK_TRUST values 4. Operations 4.1. Checking Trust Assertions Trust assertions are checked using a PKCS#11 C_FindObjects operation. Because trust is involved and presence/lack of results is important, this operation MUST be done with a specific set of lookup attributes. The attributes used differ depending on whether the certificate is self-signed or is signed by an issuer. Checking of trust assertions is always done for a specific purpose. 4.1.1. Checking a Root Certificate Authority A C_FindObjects operation is done using the following attributes. Walter Expires March 5, 2011 [Page 7] Internet-Draft PKCS#11 Trust Assertions September 2010 +--------------------+---------------------------------------+ | Attribute | Value | +--------------------+---------------------------------------+ | CKA_CLASS | CKO_NETSCAPE_TRUST | | CKA_CERT_SHA1_HASH | 20 byte value of hash of certificate. | | Purpose attribute | CKT_TRUSTED_DELEGATOR | +--------------------+---------------------------------------+ 4.1.2. Checking a Self-Signed Certificate A C_FindObjects operation is done using the following attributes. +--------------------+---------------------------------------+ | Attribute | Value | +--------------------+---------------------------------------+ | CKA_CLASS | CKO_NETSCAPE_TRUST | | CKA_CERT_SHA1_HASH | 20 byte value of hash of certificate. | | Purpose attribute | CKT_TRUSTED | +--------------------+---------------------------------------+ 4.1.3. Checking an otherwise Trusted Certificate A C_FindObjects operation is done using the following attributes. +-------------------+--------------------------------------------+ | Attribute | Value | +-------------------+--------------------------------------------+ | CKA_CLASS | CKO_NETSCAPE_TRUST | | CKA_ISSUER | DER encoding of certificate issuer. | | CKA_SERIAL_NUMBER | DER encoding of certificate serial number. | | Purpose attribute | CKT_UNTRUSTED | +-------------------+--------------------------------------------+ 4.2. Storing Trust Assertions Xxxx 4.3. Reading Trust Assertions Xxxx 5. Acknowledgements NSS: Who? Walter Expires March 5, 2011 [Page 8] Internet-Draft PKCS#11 Trust Assertions September 2010 6. Further Considerations xxxx 7. Security Considerations Xxxx: Use of multiple PKCS#11 modules Not using just any module. 8. References 8.1. Normative References [min_ref] authSurName, authInitials., "Minimal Reference", 2006. 8.2. Informative References [DOMINATION] Mad Dominators, Inc., "Ultimate Plan for Taking Over the World", 1984, . Appendix A. Additional Stuff This becomes an Appendix. Author's Address Stef Walter (editor) GNOME Phone: +1 505 926 1827 Email: stefw@gnome.org Walter Expires March 5, 2011 [Page 9] Internet-Draft PKCS#11 Trust Assertions September 2010 Full Copyright Statement Copyright (C) The IETF Trust (2010). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Intellectual Property The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Walter Expires March 5, 2011 [Page 10]