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commit 8b3deef9012abc8da5814eb5e3ed46c0a5448a0f
Author: Werner Koch <wk at gnupg.org>
Date: Wed May 18 09:35:35 2016 +0200
drafts: openpgp-webkey-service - published 01
diff --git a/misc/id/openpgp-webkey-service/Makefile b/misc/id/openpgp-webkey-service/Makefile
index 5e95728..dad63f1 100644
--- a/misc/id/openpgp-webkey-service/Makefile
+++ b/misc/id/openpgp-webkey-service/Makefile
@@ -7,7 +7,7 @@ MD_EXAMPLE_FIX = '(defun org-md-example-block (example-block contents info) \
(org-export-format-code-default example-block info))))'
-draft.txt: draft.org
+draft.txt, draft.xml: draft.org
emacs --batch \
--eval "(require 'org)" \
--eval "(require 'ox-md)" \
@@ -22,4 +22,5 @@ draft.txt: draft.org
sed <draft.md -n '/^# Back/,$$ p' | \
sed '1 d' >tmp-back.md
pandoc2rfc tmp-abstract.md tmp-middle.md tmp-back.md
- rm template.xml tmp-abstract.md tmp-middle.md tmp-back.md
+ pandoc2rfc -X tmp-abstract.md tmp-middle.md tmp-back.md
+ rm template.xml tmp-abstract.md tmp-middle.md tmp-back.md draft.md
diff --git a/misc/id/openpgp-webkey-service/draft-koch-openpgp-webkey-service-01.txt b/misc/id/openpgp-webkey-service/draft-koch-openpgp-webkey-service-01.txt
new file mode 100644
index 0000000..e36c435
--- /dev/null
+++ b/misc/id/openpgp-webkey-service/draft-koch-openpgp-webkey-service-01.txt
@@ -0,0 +1,560 @@
+
+
+
+
+Network Working Group W. Koch
+Internet-Draft GnuPG Project
+Intended status: Informational May 18, 2016
+Expires: November 19, 2016
+
+
+ OpenPGP Web Key Service
+ draft-koch-openpgp-webkey-service-01
+
+Abstract
+
+ This specification describes a service to locate OpenPGP keys by mail
+ address using a Web service and the HTTPS protocol. It also provides
+ a method for secure communication between the key owner and the mail
+ provider to publish and revoke the public key.
+
+Status of This Memo
+
+ This Internet-Draft is submitted in full conformance with the
+ provisions of BCP 78 and 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 November 19, 2016.
+
+Copyright Notice
+
+ Copyright (c) 2016 IETF Trust and the persons identified as the
+ document authors. All rights reserved.
+
+ This document is subject to BCP 78 and the IETF Trust's Legal
+ Provisions Relating to IETF Documents
+ (http://trustee.ietf.org/license-info) in effect on the date of
+ publication of this document. Please review these documents
+ carefully, as they describe your rights and restrictions with respect
+ to this document. Code Components extracted from this document must
+ include Simplified BSD License text as described in Section 4.e of
+ the Trust Legal Provisions and are provided without warranty as
+ described in the Simplified BSD License.
+
+
+
+
+Koch Expires November 19, 2016 [Page 1]
+
+Internet-Draft OpenPGP Web Key Service May 2016
+
+
+Table of Contents
+
+ 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
+ 2. Notational Conventions . . . . . . . . . . . . . . . . . . . 2
+ 3. Web Key Directory . . . . . . . . . . . . . . . . . . . . . . 2
+ 3.1. Key Discovery . . . . . . . . . . . . . . . . . . . . . . 3
+ 4. Web Key Directory Update Protocol . . . . . . . . . . . . . . 4
+ 4.1. The Submission Address . . . . . . . . . . . . . . . . . 5
+ 4.2. The Submission Mail . . . . . . . . . . . . . . . . . . . 6
+ 4.3. The Confirmation Request . . . . . . . . . . . . . . . . 6
+ 4.4. The Confirmation Response . . . . . . . . . . . . . . . . 7
+ 4.5. Policy Flags . . . . . . . . . . . . . . . . . . . . . . 8
+ 5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
+ 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
+ 6.1. Well-Known URI . . . . . . . . . . . . . . . . . . . . . 9
+ 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9
+ 8. Normative References . . . . . . . . . . . . . . . . . . . . 9
+ Appendix A. Test Vectors . . . . . . . . . . . . . . . . . . . . 10
+ A.1. Sample key . . . . . . . . . . . . . . . . . . . . . . . 10
+ A.2. Software Notes . . . . . . . . . . . . . . . . . . . . . 10
+ Appendix B. Changes since -00 . . . . . . . . . . . . . . . . . 10
+ B.1. TODO . . . . . . . . . . . . . . . . . . . . . . . . . . 10
+ Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 10
+
+1. Introduction
+
+ This memo describes a method to associate OpenPGP keys with a mail
+ address and how to look them up using a web service with a well-known
+ URI. In addition a mail based protocol is given to allow a client to
+ setup such an association and to maintain it.
+
+2. Notational Conventions
+
+ 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 [RFC2119].
+
+3. Web Key Directory
+
+ A major use case for OpenPGP is the encryption of mail. A common
+ difficulty of sending encrypted mails to a new communication partner
+ is to find the appropriate public key of the recipient. Unless an
+ off-channel key exchange has been done, there are no easy ways to
+ discover the required key. The common practice is to search the
+ network of public key servers for a key matching the recipient's mail
+ address. This practise bears the problem that the keyservers are not
+ able to give a positive confirmation that a key actually belongs to
+ the mail addresses given in the key. Further, there are often
+
+
+
+Koch Expires November 19, 2016 [Page 2]
+
+Internet-Draft OpenPGP Web Key Service May 2016
+
+
+ several keys matching a mail address and thus one needs to pick a key
+ on good luck. This is clearly not a secure way to setup an end-to-
+ end encryption. Even if the need for a trusted key for an initial
+ mail message is relinquished, a non-authenticated key may be a wrong
+ one and the actual recipient would receive a mail which she can't
+ decrypt, due to the use of a wrong key.
+
+ Methods to overcome this problem are
+
+ o sending an initial unencrypted message with the public key
+ attached,
+
+ o using the OpenPGP DANE protocol to lookup the recipients key via
+ the DNS.
+
+ The first method has the obvious problems of not even trying to
+ encrypt the initial mail, an extra mail round-trip, and problems with
+ unattended key discovery.
+
+ The latter method works fine but requires that mail providers need to
+ set up a separate DNS resolver to provide the key. The
+ administration of a DNS zone is often not in the hands of small mail
+ installations. Thus an update of the DNS resource records needs to
+ be delegated to the ISP running the DNS service. Further, DNS
+ lookups are not encrypted and missing all confidentially. Even if
+ the participating MUAs are using STARTTLS to encrypt the mail
+ exchange, a DNS lookup for the key unnecessarily identifies the
+ local-part of the recipients mail address to any passive
+ eavesdroppers.
+
+ This memo specified a new method for key discovery using an encrypted
+ https connection.
+
+3.1. Key Discovery
+
+ Although URIs are able to encode all kind of characters,
+ straightforward implementations of a key directory may want to store
+ the "local-part" of a mail address directly in the file system. This
+ forbids the use of certain characters in the "local-part". To allow
+ for such an implementation method the URI uses an encoded form of the
+ "local-part" which can be directly mapped to a file name.
+
+ OpenPGP defines its User IDs, and thus the mail address, as UTF-8
+ strings. To help with the common pattern of using capitalized names
+ (e.g. "Joe.Doe at example.org") for mail addresses, and under the
+ premise that almost all MTAs treat the "local-part" case-insensitive
+ and that the "domain-part" is required to be compared case-
+
+
+
+
+Koch Expires November 19, 2016 [Page 3]
+
+Internet-Draft OpenPGP Web Key Service May 2016
+
+
+ insensitive anyway, all upper-case ASCII characters in a User ID are
+ mapped to lowercase. Non-ASCII characters are not changed.
+
+ The so mapped "local-part" is hashed using the SHA-1 algorithm. The
+ resulting 160 bit digest is encoded using the Z-Base-32 method as
+ described in [RFC6189], section 5.1.6. The resulting string has a
+ fixed length of 32 octets. To form the URI, the scheme "https://" is
+ concatenated with the mapped "domain-part", the fixed string "./well-
+ known/openpgpkey/hu/", and the above constructed 32 octet string.
+
+ For example the URI to lookup the key for Joe.Doe at Example.ORG is:
+
+ https://example.org/.well-known/openpgpkey/
+ hu/iy9q119eutrkn8s1mk4r39qejnbu3n5q
+
+ (line has been wrapped for rendering purposes)
+
+ The HTTP GET method MUST return the binary representation of the
+ OpenPGP key for the given mail address. The key needs to carry a
+ User ID packet ([RFC4880]) with that mail address. Note that the key
+ may be revoked or expired - it is up to the client to handle such
+ conditions. The server MUST also accept a HEAD method so that a
+ client may only check for the existence of a key.
+
+ The server SHOULD return "application/octet-string" as the content-
+ type for the data but clients MAY also accept any other appropriate
+ content-type. The server MUST NOT return an ASCII armored version of
+ the key.
+
+4. Web Key Directory Update Protocol
+
+ To put keys into the key directory a protocol to automate the task is
+ desirable. The protocol defined here is entirely based on mail and
+ the assumption that a mail provider can securely deliver mail to the
+ INBOX of a user (e.g. an IMAP folder). Note that the same protocol
+ may also be used for submitting keys for use with OpenPGP DANE.
+
+ We assume that the user already created a key for her mail account
+ alice at example.org. To install the key at her provider's Web Key
+ Directory, she performs the following steps:
+
+ 1. She retrieves a file which contains one line with the mail
+ address used to submit the key to the mail provider. See below
+ for the syntax of that file. For a mail address at the domain
+ "example.org" the URI of the file is
+
+ https://example.org/.well-known/openpgpkey/submission-address
+
+
+
+
+Koch Expires November 19, 2016 [Page 4]
+
+Internet-Draft OpenPGP Web Key Service May 2016
+
+
+ 2. She sends her key using SMTP (or any other transport mechanism)
+ to the provider using the submission address and key format as
+ specified by PGP/MIME.
+
+ 3. The provider checks that the received key has a User ID which
+ matches an account name of the provider.
+
+ 4. The provider sends an encrypted message containing a nonce and
+ the fingerprint of the key to the mail account of the user. Note
+ that a similar scheme is used by the well known caff(1) tool to
+ help with key signing parties.
+
+ 5. A legitimate user will be able to decrypt the message because she
+ created the key and is in charge of the private key. This step
+ verifies that the submitted key has actually been created by the
+ owner of the account.
+
+ 6. The user sends the decrypted nonce back to the submission address
+ as a confirmation that the private key is owned by her and that
+ the provider may now publish the key. Also technically not
+ required, it is suggested that the mail to the provider is
+ encrypted. The public key for this is retrieved using the key
+ lookup protocol described above.
+
+ 7. The provider receives the nonce, matches it with its database of
+ pending confirmations and then publishes the key. Finally the
+ provider sends a mail back to the user to notify her of the the
+ publication of her key.
+
+ The message data structures used for the above protocol are specified
+ in detail below. In the following sections the string "WELLKNOWN"
+ denotes the first part of an URI specific for a domain. In the
+ examples the domain "example.org" is assumed, thus
+
+ WELLKNOWN := https://example.org/.well-known/openpgpkey
+
+ The term "target key" denotes the to be published key, the term
+ "submission key" the key associated with the submission-address of
+ the mail provider.
+
+4.1. The Submission Address
+
+ The address of the submission file is
+
+ WELLKNOWN/submission-address
+
+ The file consists of exactly one line, terminated by a LF, or the
+ sequence of CR and LF, with the full mail address to be used for
+
+
+
+Koch Expires November 19, 2016 [Page 5]
+
+Internet-Draft OpenPGP Web Key Service May 2016
+
+
+ submission of a key to the mail provider. For example the content of
+ the file may be
+
+ key-submission-example.org at directory.example.org
+
+4.2. The Submission Mail
+
+ The mail used to submit a key to the mail provider MUST comply to the
+ PGP/MIME specification ([RFC3156], section 7), which states that the
+ Content-Type must be "application/pgp-keys", there are no required or
+ optional parameters, and the body part contains the ASCII-armored
+ transferable Public Key Packets as defined in [RFC4880], section
+ 11.1.
+
+ If the mail provider has published an encryption key for the
+ submission-address in the Web Key Directory, the key to be published
+ MUST be submitted using a PGP/MIME encrypted message ([RFC3156],
+ section 4). The message MUST NOT be signed (because the authenticity
+ of the signing key has not yet been confirmed). After decryption of
+ the message at the mail provider a single "application/pgp-keys"
+ part, as specified above, is expected.
+
+4.3. The Confirmation Request
+
+ The mail provider sends a confirmation mail in response to a received
+ key publication request. The message SHOULD be sent from the
+ submission-address of the mail provider to the mail address extracted
+ from the target key. The message needs to be encrypted to the target
+ key and MAY be signed by the submission key. PGP/MIME MUST be used
+ for encryption and signing; the Combined method ([RFC3156], section
+ 6.2) MUST be used if the message is to be signed.
+
+ The Content-type used for the plaintext part MUST be "application/
+ vnd.gnupg.wkd". The body consists of name-value pairs with one name-
+ value pair per LF or CR+LF terminated line. Empty lines are allowed
+ and will be ignored by the receiver. A colon is used to terminate a
+ name.
+
+ In a confirmation request the following names MUST be send in the
+ specified order:
+
+ o *"type":* The value must be "confirmation-request".
+
+ o *"sender":* This is the mailbox the user is expected to sent the
+ confirmation response to. The value must match the mailbox part
+ of the "From:" address of this request. Exactly one address MUST
+ be given.
+
+
+
+
+Koch Expires November 19, 2016 [Page 6]
+
+Internet-Draft OpenPGP Web Key Service May 2016
+
+
+ o *"address":* The value is the addr-spec part of the target key's
+ mail address. The value SHOULD match the addr-spec part of the
+ recipient's address. The value MUST be UTF-8 encoded as required
+ for an OpenPGP User ID.
+
+ o *"fingerprint":* The value is the fingerprint of the target key.
+ The fingerprint is given in uppercase hex encoding without any
+ interleaving spaces.
+
+ o *"nonce":* The value is a string with a minimum length of 16
+ octets and a maximum length of 64 octets. The string must
+ entirely be made up of random ASCII letters or digits. This nonce
+ will be sent back to the mail provider as proof that the recipient
+ is the legitimate owner of the target-key.
+
+ The receiver of the message decrypts the message, checks that the
+ "fingerprint" matches the target key, checks that the "address"
+ matches a User ID of the target key, and checks the other constrains
+ of the request format. If any constraint is not asserted, or the
+ fingerprint or User ID do not match the target key, or there is no
+ pending publication requests (i.e. a mail recently sent o the
+ submission address), the user MAY be notified about this fake
+ confirmation attempt.
+
+ In other cases the confirmation request is legitimate and the MUA
+ shall silently send a response as described in the next section.
+
+4.4. The Confirmation Response
+
+ A response to a confirmation request MUST only be send in the
+ positive case; there is no negative confirmation response. A mail
+ service provider is expected to cancel a pending key submission after
+ a suitable time without a confirmation. The mail service provider
+ SHOULD NOT retry the sending of a confirmation request after the
+ first request has been send successfully.
+
+ The user MUST send the confirmation response from her target mail
+ address to the "from" address of the confirmation request. The
+ message MUST be signed and SHOULD be encrypted. The PGP/MIME
+ Combined format MUST be used for encryption and signing ([RFC3156],
+ section 6.2). The encryption key can be taken from the Web Key
+ Directory.
+
+ The Content-type used for the plaintext message MUST also be
+ "application/vnd.gnupg.wkd". The format is the same as described
+ above for the Confirmation Request. The body must contain three
+ name-value pairs in this order:
+
+
+
+
+Koch Expires November 19, 2016 [Page 7]
+
+Internet-Draft OpenPGP Web Key Service May 2016
+
+
+ o *"type":* The value must be "confirmation-response".
+
+ o *"sender":* The value must match the mailbox part of the "From:"
+ address of this response. Exactly one address MUST be given.
+
+ o *"nonce":* The value is the value of the "nonce" parameter from
+ the confirmation request.
+
+4.5. Policy Flags
+
+ For key generation and submission it is sometimes useful to tell the
+ client about certain properties of the mail provider in advance.
+ This can be done with a file at the URL
+
+ WELLKNOWN/policy
+
+ The file contains keywords, one per line with each line terminated by
+ a LF or the sequence of CR and LF. Empty lines and lines starting
+ with a '#' character are considered comment lines. A keyword is made
+ up of lowercase letters, digits, hyphens, or dots. An underscore is
+ allowed as a name space delimiters; see below. The first character
+ must be a letter. Clients MUST use case-insensitive matching.
+
+ Currently defined keywords are:
+
+ o *"mailbox-only":* The mail server provider does only accept keys
+ with only a mailbox in the User ID. In particular User IDs with a
+ real name in addition to the mailbox will be rejected as invalid.
+
+ o *"dane-only":* The mail server provider does not run a Web Key
+ Directory but only an OpenPGP DANE service. The Web Key Directory
+ Update protocol is used to update the keys for the DANE service.
+
+ More keywords will be defined in updates to this I-D. There is no
+ registry yet except for this document. For experimental use of new
+ features or for provider specific settings, keywords MUST be prefixed
+ with a domain name and an underscore.
+
+5. Security Considerations
+
+ The use of SHA-1 for the mapping of the "local-part" to a fixed
+ string is not a security feature but merely used to map the local-
+ part to a fixed-sized string made from a well defined set of
+ characters. It is not intended to conceal information about a mail
+ address.
+
+
+
+
+
+
+Koch Expires November 19, 2016 [Page 8]
+
+Internet-Draft OpenPGP Web Key Service May 2016
+
+
+ The domain name part of the mail address is not part of the hash to
+ avoid problems with internationalized domain names. Instead a
+ separate web service is required for each domain name.
+
+6. IANA Considerations
+
+6.1. Well-Known URI
+
+ IANA is requested to assign a well-known URI in the "Well-Known URIs"
+ registry as defined by [RFC5785]:
+
+ URI suffix: openpgpkey
+
+ Change controller: IETF
+
+ Specification document: This
+
+7. Acknowledgments
+
+ The author would like to acknowledge the help of the individuals who
+ kindly voiced their opinions on the GnuPG mailing lists, in
+ particular, the help of Bernhard Reiter and Guilhem Moulin.
+
+8. Normative References
+
+ [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [RFC3156] Elkins, M., Del Torto, D., Levien, R., and T. Roessler,
+ "MIME Security with OpenPGP", RFC 3156, August 2001.
+
+ [RFC4880] Callas, J., Donnerhacke, L., Finney, H., Shaw, D., and R.
+ Thayer, "OpenPGP Message Format", RFC 4880, November 2007.
+
+ [RFC5785] Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known
+ Uniform Resource Identifiers (URIs)", RFC 5785, DOI
+ 10.17487/RFC5785, April 2010,
+ <http://www.rfc-editor.org/info/rfc5785>.
+
+ [RFC6189] Zimmermann, P., Johnston, A., Ed., and J. Callas, "ZRTP:
+ Media Path Key Agreement for Unicast Secure RTP", RFC
+ 6189, DOI 10.17487/RFC6189, April 2011,
+ <http://www.rfc-editor.org/info/rfc6189>.
+
+
+
+
+
+
+
+
+Koch Expires November 19, 2016 [Page 9]
+
+Internet-Draft OpenPGP Web Key Service May 2016
+
+
+Appendix A. Test Vectors
+
+ For help implementing this specification a non-normative example is
+ given:
+
+A.1. Sample key
+
+ TODO
+
+A.2. Software Notes
+
+ GnuPG supports the key discovery described in version -00 of this
+ document since version 2.1.12, 2.1.13 and the gurrent git version
+ will be adjusted to the changes specs dfescribed in -01. To use it,
+ the new method "wkd" needs to be used with the "--auto-key-locate"
+ option.
+
+Appendix B. Changes since -00
+
+ o Dropped the second occurrence of the domain name from the URL.
+
+ o Changed field names in the request and response format.
+
+ o Removed useless checks.
+
+ o Added a new policy flag.
+
+B.1. TODO
+
+ o What about authenticated submission?
+
+ o Describe how to handle a key with several User IDs.
+
+Author's Address
+
+ Werner Koch
+ GnuPG Project
+
+ Email: wk at gnupg.org
+ URI: https://gnupg.org
+
+
+
+
+
+
+
+
+
+
+
+Koch Expires November 19, 2016 [Page 10]
diff --git a/misc/id/openpgp-webkey-service/draft.org b/misc/id/openpgp-webkey-service/draft.org
index b10dedf..5756e7d 100644
--- a/misc/id/openpgp-webkey-service/draft.org
+++ b/misc/id/openpgp-webkey-service/draft.org
@@ -19,7 +19,7 @@
]>
<rfc ipr="trust200902" category="info"
- docName="draft-koch-openpgp-webkey-service-00">
+ docName="draft-koch-openpgp-webkey-service-01">
<?rfc toc="yes"?>
<?rfc symrefs="yes"?>
@@ -429,16 +429,17 @@ TODO
** Software Notes
-GnuPG supports the key discovery described in this document since
-version 2.1.12. To use it, the new method "wkd" needs to be used with
-the =--auto-key-locate= option.
+GnuPG supports the key discovery described in version -00 of this
+document since version 2.1.12, 2.1.13 and the gurrent git version will
+be adjusted to the changes specs dfescribed in -01. To use it, the
+new method "wkd" needs to be used with the =--auto-key-locate= option.
* Changes since -00
+- Dropped the second occurrence of the domain name from the URL.
- Changed field names in the request and response format.
- Removed useless checks.
- Added a new policy flag.
-- Dropped the second occurrence of the domain name from the URL.
** TODO
-----------------------------------------------------------------------
Summary of changes:
misc/id/openpgp-webkey-service/Makefile | 5 +-
...xt => draft-koch-openpgp-webkey-service-01.txt} | 198 ++++++++++-----------
misc/id/openpgp-webkey-service/draft.org | 11 +-
3 files changed, 108 insertions(+), 106 deletions(-)
copy misc/id/openpgp-webkey-service/{draft-koch-openpgp-webkey-service-00.txt => draft-koch-openpgp-webkey-service-01.txt} (80%)
hooks/post-receive
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