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commit 706f736fdbc9ef00d6606a45e73bf5169e9ce4ea
Author: Werner Koch <wk at gnupg.org>
Date: Tue Jan 31 12:07:13 2017 +0100
drafts,openpgp-webkey-service: Published -03
diff --git a/misc/id/openpgp-webkey-service/draft-koch-openpgp-webkey-service-03.txt b/misc/id/openpgp-webkey-service/draft-koch-openpgp-webkey-service-03.txt
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+++ b/misc/id/openpgp-webkey-service/draft-koch-openpgp-webkey-service-03.txt
@@ -0,0 +1,952 @@
+
+
+
+
+Network Working Group W. Koch
+Internet-Draft GnuPG Project
+Intended status: Informational January 31, 2017
+Expires: August 4, 2017
+
+
+ OpenPGP Web Key Service
+ draft-koch-openpgp-webkey-service-03
+
+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 August 4, 2017.
+
+Copyright Notice
+
+ Copyright (c) 2017 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 August 4, 2017 [Page 1]
+
+Internet-Draft OpenPGP Web Key Service January 2017
+
+
+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 . . . . . . . . . . . . . . 5
+ 4.1. The Submission Address . . . . . . . . . . . . . . . . . 6
+ 4.2. The Submission Mail . . . . . . . . . . . . . . . . . . . 6
+ 4.3. The Confirmation Request . . . . . . . . . . . . . . . . 6
+ 4.4. The Confirmation Response . . . . . . . . . . . . . . . . 8
+ 4.5. Policy Flags . . . . . . . . . . . . . . . . . . . . . . 9
+ 5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
+ 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
+ 6.1. Well-Known URI . . . . . . . . . . . . . . . . . . . . . 10
+ 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
+ 8. Normative References . . . . . . . . . . . . . . . . . . . . 10
+ Appendix A. Sample Protocol Run . . . . . . . . . . . . . . . . 11
+ A.1. Sample Keys . . . . . . . . . . . . . . . . . . . . . . . 11
+ A.2. Sample Messages . . . . . . . . . . . . . . . . . . . . . 12
+ Appendix B. Changes Since -02 . . . . . . . . . . . . . . . . . 16
+ Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 17
+
+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
+ several keys matching a mail address and thus one needs to pick a key
+
+
+
+Koch Expires August 4, 2017 [Page 2]
+
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+
+
+ 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-insensitive
+ anyway, all upper-case ASCII characters in a User ID are mapped to
+ lowercase. Non-ASCII characters are not changed.
+
+
+
+Koch Expires August 4, 2017 [Page 3]
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+
+
+ 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 following parts are
+ concatenated:
+
+ o The scheme "https://",
+
+ o the domain-part,
+
+ o the string "/.well-known/openpgpkey/hu/",
+
+ o 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)
+
+ DNS SRV resource records ([RFC2782]) may be used to query a different
+ host or a port other than 443. For example:
+
+ _openpgpkey._tcp.example.org. IN SRV 0 0 8443 wkd.example.org.
+
+ changes the above to query the host "wkd.example.org" at port 8443
+ instead of the host "gnupg.org" at port 443. The target (in the
+ example "wkd.example.org") MUST be a sub-domain of the domain-part
+ (here "example.org"). If the target is not a sub-domain, the SRV RR
+ MUST be be ignored. The recommended name for the sub-domain is
+ "wkd".
+
+ 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. To ease distribution of revoked keys, a server may
+ return revoked keys in addition to a new key. The keys are returned
+ by a single request as concatenated key blocks.
+
+ The server MUST accept the HTTP HEAD method to allow a client to
+ check for the existence of a key.
+
+ The server SHOULD use "application/octet-string" as the Content-Type
+ for the data but clients SHOULD also accept any other Content-Type.
+ The server MUST NOT return an ASCII armored version of the key.
+
+
+
+
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+
+
+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. The DNS SRV
+ rules described for the Web Key Directory apply here as well.
+ 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
+
+ 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. Although 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
+ publication of her key.
+
+
+
+Koch Expires August 4, 2017 [Page 5]
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+
+
+ 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
+ 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.
+
+ The mail provider MUST publish a key capable of signing and
+ encryption for the submission-address in the Web Key Directory or via
+ DANE. 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 MUST be sent from the
+ submission-address of the mail provider to the mail address extracted
+ from the target key. The message needs to be a PGP/MIME signed
+
+
+
+
+Koch Expires August 4, 2017 [Page 6]
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+
+
+ message using the submission key of the provider for the signature.
+ The signed message MUST have two parts:
+
+ The first part MUST have "text" as its Content-Type and can be used
+ to explain the purpose of the mail. For example it may point to this
+ RFC and explain on how to manually perform the protocol.
+
+ The second part MUST have "application/vnd.gnupg.wkd" as its Content-
+ Type and carry an OpenPGP encrypted message in ASCII Armor format.
+ The message MUST be encrypted to the target key and MUST NOT be
+ signed. After decryption a text file in the Web Key data format must
+ be yielded.
+
+ That data format 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.
+
+ 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 that message is expected to verify the outer
+ signature and disregard the entire message if it can't be verified or
+ has not been signed by the key associated with the submission
+ address.
+
+
+
+
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+
+
+ After the message as been verified the receiver decrypts the second
+ part of 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.
+
+ The rationale for the outer signature used with this request is to
+ allow early detection of spam mails. This can be done prior to the
+ decryption step and avoids asking the user to enter a passphrase to
+ perform the decryption for a non-legitimate message. The use of a
+ simple encrypted attachment, instead of using PGP/MIME encryption, is
+ to convey the Content-Type of that attachment in the clear and also
+ to prevent automatic decryption of that attachment by PGP/MIME aware
+ clients. The MUA may in fact detect this confirmation request and
+ present a customized dialog for confirming that request.
+
+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 encrypted using the PGP/MIME Combined
+ format ([RFC3156], section 6.2). The signing key is the target key
+ and the encryption key is the key associated with the provider's
+ submission address.
+
+ 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:
+
+ 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.
+
+
+
+
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+
+
+ 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 and optioanlly values, 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. Keywords which are
+ defined to require a value are directly followed by a colon and then
+ after optional white space the value. Clients MUST use case-
+ insensitive matching for the keyword.
+
+ 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.
+
+ o "auth-submit": The submission of the mail to the server is done
+ using an authenticated connection. Thus the submitted key will be
+ published immediately without any confirmation request.
+
+ More keywords will be defined in updates to this I-D. There is no
+ registry 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.
+
+
+
+
+
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+
+
+ The domain name part of the mail address is not part of the hash to
+ avoid problems with internationalized domain names. Instead a
+ separate URL is required for each domain name.
+
+ The use of DNS SRV records reduces the certainty that a mail address
+ belongs to a domain. For example an attacker may change the target
+ to a host in a sub-domain under their control and thus gain full
+ control over all keys. An implementation may want to weight the
+ certainty of a mapping different if it has been retrieved via a sub-
+ domain and in particular if a non-recommended name is used for the
+ sub-domain.
+
+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.
+
+ [RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
+ specifying the location of services (DNS SRV)", RFC 2782,
+ DOI 10.17487/RFC2782, February 2000,
+ <http://www.rfc-editor.org/info/rfc2782>.
+
+ [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.
+
+
+
+
+
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+
+
+ [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>.
+
+Appendix A. Sample Protocol Run
+
+ The following non-normative example can be used by implementors as
+ guidance.
+
+ Note that GnuPG version 2.1.12 supports the key discovery described
+ in version -00 of this document (auto-key-locate method "wkd").
+ Version 2.1.16 can run the protocol decribed in this document but is
+ also able to run the protocol version specified by -01.
+
+A.1. Sample Keys
+
+ This is the provider's submission key:
+
+ -----BEGIN PGP PRIVATE KEY BLOCK-----
+
+ lFgEV/TAohYJKwYBBAHaRw8BAQdAB/k9YQfSTI8qQqqK1KimH/BsvzsowWItSQPT
+ FP+fOC4AAP46uJ3Snno3Vy+kORye3rf0VvWvuz82voEQLxG6WpfHhREEtBprZXkt
+ c3VibWlzc2lvbkBleGFtcGxlLm5ldIh5BBMWCAAhBQJX9MCiAhsDBQsJCAcCBhUI
+ CQoLAgQWAgMBAh4BAheAAAoJEKhtNooW0cqEWMUA/0e9XaeptszWC9ZvPg8INL6a
+ BvRqPBYGU7PGmuXsxBovAQDyckOykG0UAfHVyN1w4gSK/biMcnqVr857i8/HuvjW
+ C5xdBFf0wKISCisGAQQBl1UBBQEBB0Apvaoe4MtSEJ1fpds/4DFl2kXXBpnVji/s
+ Wg9btdthNQMBCAcAAP9FJX99T1LEJzBnvBBnc6bimnT6/1OKM9RdO4R0/uVP6BFL
+ iGEEGBYIAAkFAlf0wKICGwwACgkQqG02ihbRyoTlGwD9FBr92osjL7HkhhZZ7Z2D
+ My3b9zpoZeMjvPg5YPqpdKMA/jhZoHuZCRMBYf7YRFb8aXtuyetDFZYrkjnum+OG
+ HFAD
+ =Hnwd
+ -----END PGP PRIVATE KEY BLOCK-----
+
+ This is the target key to be published:
+
+
+
+
+
+
+
+
+
+
+
+Koch Expires August 4, 2017 [Page 11]
+
+Internet-Draft OpenPGP Web Key Service January 2017
+
+
+ -----BEGIN PGP PRIVATE KEY BLOCK-----
+
+ lFgEV2o9XRYJKwYBBAHaRw8BAQdAZ8zkuQDL9x7rcvvoo6s3iEF1j88Dknd9nZhL
+ nTEoBRkAAP94nCZMM4WY2IORXfM6phLGSz3RsHvs/vA1Opaus4+R3BKJtBtwYXRy
+ aWNlLmx1bXVtYmFAZXhhbXBsZS5uZXSIeQQTFggAIQUCV2o9XQIbAwULCQgHAgYV
+ CAkKCwIEFgIDAQIeAQIXgAAKCRATlWNoKgINCpkNAQDFDcwJUzsxu7aJUiPdpYXj
+ 4uVarrXakxEE8mGFotWhLAD9GH4rqLDYIE3NKEU0s+Okt4tEIwJaV8H1NNPPPMiK
+ 3g2cXQRXaj2NEgorBgEEAZdVAQUBAQdAFnnmZc99TuKk5iCq9wmYZUVF2RcXN2Cs
+ qAl8iGQQUWsDAQgHAAD/VN/VGmlcwGBPcLTya2hfU4t37nMcFCKdNSXjJ5DFA0AP
+ PohhBBgWCAAJBQJXaj2NAhsMAAoJEBOVY2gqAg0Ky4UA/0GmVaXzXemLvv1Xw4yx
+ Eaz/KfKKGc4RJ+38fyqUzw8NAQCohQ+ki3I5f84EXLZEiUiLsnVtOn1HNxvND/gW
+ TiFZBA==
+ =GHi7
+ -----END PGP PRIVATE KEY BLOCK-----
+
+A.2. Sample Messages
+
+ The first message triggeres the publication requests.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Koch Expires August 4, 2017 [Page 12]
+
+Internet-Draft OpenPGP Web Key Service January 2017
+
+
+ From: patrice.lumumba at example.net
+ To: key-submission at example.net
+ Subject: Key publishing request
+ MIME-Version: 1.0
+ Content-Type: multipart/encrypted;
+ protocol="application/pgp-encrypted";
+ boundary="=-=01-e8k41e11ob31eefa36wo=-="
+ Date: Wed, 05 Oct 2016 10:15:51 +0000
+
+
+ --=-=01-e8k41e11ob31eefa36wo=-=
+ Content-Type: application/pgp-encrypted
+
+ Version: 1
+
+ --=-=01-e8k41e11ob31eefa36wo=-=
+ Content-Type: application/octet-stream
+
+ -----BEGIN PGP MESSAGE-----
+
+ hF4DUgLY5tvmW2sSAQdAR1AcqvFpQe/fHRZbf0xcnl9Tb+AtwaX2yZnZXGELGHsw
+ 1/e3E0JptwM5tpRAVe71ooF8Zq4jl76ZgQKfj/SyjpLJxyoEDy2N5wTQaqW4JtML
+ 0ukB1vh7dIRDxBJX/LQIJC0wz8o1Q3vjcLJKFFvDb7YrerABpPIzwOAupcgIbQHj
+ 5m1+2WU5CL8ffyJy2h1jV2X4OnvWF1Sn6J6SVD6DfZpOPRt9TxSemJrN1LJ3lG0N
+ ts8AuYmCOeC1H2r5TYyxqkC98JF8+Nvyxd/fwne8IOjK9uixkNMC5H9/ZOH0YWCb
+ wBnNB4iXuym4OIPxiLkDymsVF0ww/XrODE9Y259EGmO45VFNrJAX3HFs9/PcMCVk
+ n2qMyEkr8LHiXeEPun6Z54RHUPYv2cUkEZ0hhSJ+rtBxkc/5D/cAScCEXRKFSKEF
+ jLJAvLK/u/ga5DAzVai+vh6b6Bq+YVPaD9GWMhWj4CgR90p9LULi6S/Hzwhv9Wzf
+ 8fJoJOaDjyvRDgr09jYLWamxkS9NWxqwy6MXJvxwbNdd5XtqiW4Y4o0Ll1hDJhxR
+ ljn/XvotXKwhKN+4QGhIXDVt4Dl4XxS5ptWfVTau8W8DYqDsU2obEcfsirZv53M1
+ Q9FCD8CD9+dkBt8VAJekCWVhEltcRHxlrznbk2jxm93xSD2o6gZ5X0VSaSUXyEhm
+ J+8F3gyTHGgbq/TgyjFoockWh5EtGgAFuWvmPJCF5PO/UaNeoKwgwSJBu6oTXkHx
+ R4nvvMRcj5UgTsKpZ79NiDQukbjG5ScNT5TCUiiZsBXBqBx3fD61EH6cAuh4P3Kr
+ iM7PY4fwAHo890Dx+Qlt
+ =WIhx
+ -----END PGP MESSAGE-----
+
+ --=-=01-e8k41e11ob31eefa36wo=-=--
+
+ The server decrypts this message to
+
+
+
+
+
+
+
+
+
+
+
+Koch Expires August 4, 2017 [Page 13]
+
+Internet-Draft OpenPGP Web Key Service January 2017
+
+
+ Content-Type: application/pgp-keys
+
+ -----BEGIN PGP PUBLIC KEY BLOCK-----
+
+ mDMEV2o9XRYJKwYBBAHaRw8BAQdAZ8zkuQDL9x7rcvvoo6s3iEF1j88Dknd9nZhL
+ nTEoBRm0G3BhdHJpY2UubHVtdW1iYUBleGFtcGxlLm5ldIh5BBMWCAAhBQJXaj1d
+ AhsDBQsJCAcCBhUICQoLAgQWAgMBAh4BAheAAAoJEBOVY2gqAg0KmQ0BAMUNzAlT
+ OzG7tolSI92lhePi5VqutdqTEQTyYYWi1aEsAP0YfiuosNggTc0oRTSz46S3i0Qj
+ AlpXwfU00888yIreDbg4BFdqPY0SCisGAQQBl1UBBQEBB0AWeeZlz31O4qTmIKr3
+ CZhlRUXZFxc3YKyoCXyIZBBRawMBCAeIYQQYFggACQUCV2o9jQIbDAAKCRATlWNo
+ KgINCsuFAP9BplWl813pi779V8OMsRGs/ynyihnOESft/H8qlM8PDQEAqIUPpIty
+ OX/OBFy2RIlIi7J1bTp9RzcbzQ/4Fk4hWQQ=
+ =qRfF
+ -----END PGP PUBLIC KEY BLOCK-----
+
+ and returns this confirmation request
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Koch Expires August 4, 2017 [Page 14]
+
+Internet-Draft OpenPGP Web Key Service January 2017
+
+
+ From: key-submission at example.net
+ To: patrice.lumumba at example.net
+ Subject: Confirm your key publication
+ MIME-Version: 1.0
+ Content-Type: multipart/encrypted;
+ protocol="application/pgp-encrypted";
+ boundary="=-=01-wrzqued738dfx4x97u7y=-="
+ Date: Wed, 05 Oct 2016 10:16:57 +0000
+
+
+ --=-=01-wrzqued738dfx4x97u7y=-=
+ Content-Type: application/pgp-encrypted
+
+ Version: 1
+
+ --=-=01-wrzqued738dfx4x97u7y=-=
+ Content-Type: application/octet-stream
+
+ -----BEGIN PGP MESSAGE-----
+
+ hF4DkYWHjk/NdMASAQdAluQeqhECpU2T0zEyBAEbFzhLkpubN160wjkFCrtUc0Mw
+ FwYgM2fp9cvTMdJ/xjkvmAcIEOT4AY/hn1yFQ4z0KG0gCkSac+8mkDylnPdxlXYw
+ 0sBSAXlbqpVA7eUpFuU2Zs10zbIXxlwe6osR5wUIJut/RCOsYQmfvxC55x8mUX5/
+ zgTnNzlMzye5ws4pTgAeQm2x0Yv018L8IZgY5KxwJLBzlss0wLZ45ZcS80hR11Fx
+ NCow1fKF8lMnOJxagTEOih807nctz8vT5bR1gx0d7N3LM+th8nAg9/6Ghf1XTpLo
+ MzwGW0FtOG7Dg1Uxbw2bjaOuRBeh6IIpmNAw1pmIfnNu7PpoRydU5w1K/R8MT06z
+ MKdJ7IW5mVGes9EGnG3e4mjuILvNaZhfYy+a73IhDSaPm3oqdl1Qx7tbNg6lGjn6
+ KStCYAcPGPp3m7aWkfsPGThOVRhEXqaFFywfwSVEj1pdIRjDFA==
+ =Cdjh
+ -----END PGP MESSAGE-----
+
+ --=-=01-wrzqued738dfx4x97u7y=-=--
+
+ The client decrypts the attachment as
+
+ Content-Type: application/vnd.gnupg.wks
+ Content-Transfer-Encoding: 8bit
+
+ type: confirmation-request
+ sender: key-submission at example.net
+ address: patrice.lumumba at example.net
+ fingerprint: B21DEAB4F875FB3DA42F1D1D139563682A020D0A
+ nonce: f5pscz57zj6fk11wekk8gx4cmrb659a7
+
+ creates this response
+
+
+
+
+
+
+Koch Expires August 4, 2017 [Page 15]
+
+Internet-Draft OpenPGP Web Key Service January 2017
+
+
+ Content-Type: application/vnd.gnupg.wks
+ Content-Transfer-Encoding: 8bit
+
+ type: confirmation-response
+ sender: key-submission at example.net
+ address: patrice.lumumba at example.net
+ nonce: f5pscz57zj6fk11wekk8gx4cmrb659a7
+
+ and sends it encrypted to the server
+
+ From: patrice.lumumba at example.net
+ To: key-submission at example.net
+ Subject: Key publication confirmation
+ MIME-Version: 1.0
+ Content-Type: multipart/encrypted;
+ protocol="application/pgp-encrypted";
+ boundary="=-=01-iacqg4og4pqz11a5cg1o=-="
+ Date: Wed, 05 Oct 2016 10:18:52 +0000
+
+
+ --=-=01-iacqg4og4pqz11a5cg1o=-=
+ Content-Type: application/pgp-encrypted
+
+ Version: 1
+
+ --=-=01-iacqg4og4pqz11a5cg1o=-=
+ Content-Type: application/octet-stream
+
+ -----BEGIN PGP MESSAGE-----
+
+ hF4DUgLY5tvmW2sSAQdAnB1C3PMjS4AsGU0qaCqBdWQO5i6blWEyZrEsY+JZY1Qw
+ ooNq7zdVWOHhL9LPGAALAgoL3Qfz+dN2u5QamSQ/LJ2c8M0XipNs3lqlNH63yQN1
+ 0sAmAc3W8xkwul+rf6OLK/gMi6WzM4fnUhd4D1LJGIJoNUN0l3636C7ecOt2lkMl
+ 5bVAYg/SyMT3ymyfQnvtiem2T5DSnPsS1g6n6QNXWvkqvX9yGxNsNDJEHTuGJB8k
+ OJoRlfWQTEo6pgA89febWl1EdeM1pPLstQ2uZE8NPjXoY1nMxAlu+iPYsR41/4sg
+ dqwOv5BPLh/GIat8hh9SPWCA9iKlgSQ/EIv5DpjQogEzpriT55dkgfvSVYIAcOdO
+ ShZ91YKkcZffevdY72omqTk10a1SUXehPooIlRFmroDsi3VDaRKrUIo=
+ =7uve
+ -----END PGP MESSAGE-----
+
+ --=-=01-iacqg4og4pqz11a5cg1o=-=--
+
+Appendix B. Changes Since -02
+
+ o Specified the use of DNS SRV.
+
+
+
+
+
+
+Koch Expires August 4, 2017 [Page 16]
+
+Internet-Draft OpenPGP Web Key Service January 2017
+
+
+Author's Address
+
+ Werner Koch
+ GnuPG Project
+
+ Email: wk at gnupg.org
+ URI: https://gnupg.org
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Koch Expires August 4, 2017 [Page 17]
diff --git a/misc/id/openpgp-webkey-service/draft.org b/misc/id/openpgp-webkey-service/draft.org
index 3b90470..1239442 100644
--- a/misc/id/openpgp-webkey-service/draft.org
+++ b/misc/id/openpgp-webkey-service/draft.org
@@ -20,7 +20,7 @@
]>
<rfc ipr="trust200902" category="info"
- docName="draft-koch-openpgp-webkey-service-03">
+ docName="draft-koch-openpgp-webkey-service-04">
<?rfc toc="yes"?>
<?rfc symrefs="yes"?>
@@ -40,7 +40,7 @@
</address>
</author>
- <date month="January" year="2017" />
+ <date month="MONTH" year="2017" />
<area>Security</area>
<abstract>
commit 64ef954ef4f510631e40868341bab8132d1ec45b
Author: Werner Koch <wk at gnupg.org>
Date: Tue Jan 31 11:27:47 2017 +0100
drafts,openpgp-webkey-service: Prepare -03 for publication.
diff --git a/misc/id/openpgp-webkey-service/draft.org b/misc/id/openpgp-webkey-service/draft.org
index b5339cf..3b90470 100644
--- a/misc/id/openpgp-webkey-service/draft.org
+++ b/misc/id/openpgp-webkey-service/draft.org
@@ -40,7 +40,7 @@
</address>
</author>
- <date month="MONTH" year="2016" />
+ <date month="January" year="2017" />
<area>Security</area>
<abstract>
@@ -149,11 +149,14 @@ 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 {{{RFC(6189)}}}, section 5.1.6. The resulting string has a
-fixed length of 32 octets. To form the URI, the scheme
-{{{https_scheme}}} is concatenated with the domain-part, the
-fixed string ~/.well-known/openpgpkey/hu/~, and the above constructed
-32 octet string.
+described in {{{RFC(6189)}}}, section 5.1.6. The resulting string has
+a fixed length of 32 octets. To form the URI, the following parts are
+concatenated:
+
+- The scheme {{{https_scheme}}},
+- the domain-part,
+- the 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:
@@ -171,7 +174,7 @@ different host or a port other than 443. For example:
_openpgpkey._tcp.example.org. IN SRV 0 0 8443 wkd.example.org.
#+END_EXAMPLE
-changes the above query to query the host "wkd.example.org" at port
+changes the above to query the host "wkd.example.org" at port
8443 instead of the host "gnupg.org" at port 443. The target (in the
example "wkd.example.org") MUST be a sub-domain of the domain-part
(here "example.org"). If the target is not a sub-domain, the SRV RR
@@ -207,14 +210,13 @@ 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
+ used to submit the key to the mail provider. The DNS SRV rules
+ described for the Web Key Directory apply here as well. See below
+ for the syntax of that file. For a mail address at the domain
+ "example.org" the URI of the file is
#+begin_example
https://example.org/.well-known/openpgpkey/submission-address
#+end_example
- The DNS SRV RR rules described for the Web Key Directory apply here
- as well.
2. She sends her key using SMTP (or any other transport mechanism) to
the provider using the submission address and key format as specified
commit eef1640bf8edee36e7c6415d02277ea2faa42a7a
Author: Werner Koch <wk at gnupg.org>
Date: Tue Jan 31 11:26:37 2017 +0100
drafts: Update readme and Makefile.
diff --git a/misc/id/common/README b/misc/id/common/README
index 5afef41..4b6302d 100644
--- a/misc/id/common/README
+++ b/misc/id/common/README
@@ -1,2 +1,3 @@
Online references can be found at:
- http://xml.resource.org/public/rfc/bibxml3/
+ http://xml.resource.org/public/rfc/bibxml-rfcs/
+ http://xml.resource.org/public/rfc/bibxml3/
diff --git a/misc/id/openpgp-webkey-service/Makefile b/misc/id/openpgp-webkey-service/Makefile
index 9023455..c1d2ce8 100644
--- a/misc/id/openpgp-webkey-service/Makefile
+++ b/misc/id/openpgp-webkey-service/Makefile
@@ -8,7 +8,7 @@ MD_EXAMPLE_FIX = '(defun org-md-example-block (example-block contents info) \
draft.txt, draft.xml: draft.org
- emacs --batch \
+ emacs23 --batch \
--eval "(require 'org)" \
--eval "(require 'ox-md)" \
--eval $(MD_EXAMPLE_FIX) \
commit d44b8be4a96cf662c53cdc79067bdaad4715e11a
Author: Werner Koch <wk at gnupg.org>
Date: Tue Jan 31 11:17:42 2017 +0100
drafts,openpgp-webkey-service: Specify DNS SRV
diff --git a/misc/id/openpgp-webkey-service/draft.org b/misc/id/openpgp-webkey-service/draft.org
index 25a661f..b5339cf 100644
--- a/misc/id/openpgp-webkey-service/draft.org
+++ b/misc/id/openpgp-webkey-service/draft.org
@@ -11,6 +11,7 @@
<!ENTITY pandocMiddle PUBLIC '' 'tmp-middle.xml'>
<!ENTITY pandocBack PUBLIC '' 'tmp-back.xml'>
<!ENTITY rfc.2119 PUBLIC '' '../common/reference.RFC.2119.xml'>
+ <!ENTITY rfc.2782 PUBLIC '' '../common/reference.RFC.2782.xml'>
<!ENTITY rfc.3156 PUBLIC '' '../common/reference.RFC.3156.xml'>
<!ENTITY rfc.4880 PUBLIC '' '../common/reference.RFC.4880.xml'>
<!ENTITY rfc.5226 PUBLIC '' '../common/reference.RFC.5226.xml'>
@@ -54,6 +55,7 @@
<back>
<references title="Normative References">
&rfc.2119;
+ &rfc.2782;
&rfc.3156;
&rfc.4880;
&rfc.5785;
@@ -131,25 +133,25 @@ https connection.
** 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
+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"
+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-insensitive anyway,
+that almost all MTAs treat the local-part case-insensitive and that
+the domain-part is required to be compared case-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
+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 {{{RFC(6189)}}}, section 5.1.6. The resulting string has a
fixed length of 32 octets. To form the URI, the scheme
-{{{https_scheme}}} is concatenated with the mapped "domain-part", the
+{{{https_scheme}}} is concatenated with the domain-part, the
fixed string ~/.well-known/openpgpkey/hu/~, and the above constructed
32 octet string.
@@ -162,6 +164,19 @@ For example the URI to lookup the key for Joe.Doe at Example.ORG is:
(line has been wrapped for rendering purposes)
+DNS SRV resource records ({{{RFC(2782)}}}) may be used to query a
+different host or a port other than 443. For example:
+
+#+BEGIN_EXAMPLE
+_openpgpkey._tcp.example.org. IN SRV 0 0 8443 wkd.example.org.
+#+END_EXAMPLE
+
+changes the above query to query the host "wkd.example.org" at port
+8443 instead of the host "gnupg.org" at port 443. The target (in the
+example "wkd.example.org") MUST be a sub-domain of the domain-part
+(here "example.org"). If the target is not a sub-domain, the SRV RR
+MUST be be ignored. The recommended name for the sub-domain is "wkd".
+
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 ({{{RFC(4880)}}}) with that mail address. Note that the key
@@ -173,11 +188,12 @@ single request as concatenated key blocks.
The server MUST accept the HTTP HEAD method to allow a client to
check for the existence of a key.
-The server SHOULD return "application/octet-string" as the
+The server SHOULD use "application/octet-string" as the
Content-Type for the data but clients SHOULD also accept any other
Content-Type. The server MUST NOT return an ASCII armored version of
the key.
+
* Web Key Directory Update Protocol
To put keys into the key directory a protocol to automate the task is
@@ -197,6 +213,8 @@ Directory, she performs the following steps:
#+begin_example
https://example.org/.well-known/openpgpkey/submission-address
#+end_example
+ The DNS SRV RR rules described for the Web Key Directory apply here
+ as well.
2. She sends her key using SMTP (or any other transport mechanism) to
the provider using the submission address and key format as specified
@@ -425,14 +443,22 @@ with a domain name and an underscore.
* Security Considerations
-The use of SHA-1 for the mapping of the "local-part" to a fixed string
+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.
The domain name part of the mail address is not part of the hash to
-avoid problems with internationalized domain names. Instead a separate
-URL is required for each domain name.
+avoid problems with internationalized domain names. Instead a
+separate URL is required for each domain name.
+
+The use of DNS SRV records reduces the certainty that a mail address
+belongs to a domain. For example an attacker may change the target to
+a host in a sub-domain under their control and thus gain full control
+over all keys. An implementation may want to weight the certainty of
+a mapping different if it has been retrieved via a sub-domain and in
+particular if a non-recommended name is used for the sub-domain.
+
* IANA Considerations
@@ -660,7 +686,6 @@ ShZ91YKkcZffevdY72omqTk10a1SUXehPooIlRFmroDsi3VDaRKrUIo=
#+end_example
-* Changes Since -01
+* Changes Since -02
-- Changed the format of the confirmation request.
-- Added sample messages.
+- Specified the use of DNS SRV.
-----------------------------------------------------------------------
Summary of changes:
misc/id/common/README | 3 +-
misc/id/openpgp-webkey-service/Makefile | 2 +-
...xt => draft-koch-openpgp-webkey-service-03.txt} | 314 ++++++++++++---------
misc/id/openpgp-webkey-service/draft.org | 73 +++--
4 files changed, 238 insertions(+), 154 deletions(-)
copy misc/id/openpgp-webkey-service/{draft-koch-openpgp-webkey-service-02.txt => draft-koch-openpgp-webkey-service-03.txt} (82%)
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