mirror of
https://github.com/moparisthebest/xeps
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1de225472c
git-svn-id: file:///home/ksmith/gitmigration/svn/xmpp/trunk@2842 4b5297f7-1745-476d-ba37-a9c6900126ab
709 lines
33 KiB
XML
709 lines
33 KiB
XML
<?xml version='1.0' encoding='UTF-8'?>
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<!DOCTYPE xep SYSTEM 'xep.dtd' [
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<!ENTITY % ents SYSTEM 'xep.ent'>
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%ents;
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]>
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<?xml-stylesheet type='text/xsl' href='xep.xsl'?>
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<xep>
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<header>
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<title>Public Key Publishing</title>
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<abstract>This specification defines a method by which an entity can publish its public keys over XMPP.</abstract>
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&LEGALNOTICE;
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<number>0189</number>
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<status>Experimental</status>
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<type>Standards Track</type>
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<sig>Standards</sig>
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<dependencies>
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<spec>XMPP Core</spec>
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<spec>XEP-0060</spec>
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<spec>XEP-0163</spec>
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</dependencies>
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<supersedes>None</supersedes>
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<supersededby>None</supersededby>
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<shortname>NOT_YET_ASSIGNED</shortname>
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&ianpaterson;
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&stpeter;
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&dmeyer;
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<revision>
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<version>0.9</version>
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<date>2009-03-08</date>
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<initials>dm/psa</initials>
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<remark><p>Required specification of an algorithm for elements with hashes; removed fingerprint in <keyinfo/>; added sign request; added guidelines for key management; improved examples; changed namespace from urn:xmpp:tmp:pubkey to urn:xmpp:pubkey:0.</p></remark>
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</revision>
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<revision>
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<version>0.8</version>
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<date>2008-09-08</date>
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<initials>dm</initials>
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<remark><p>Change KeyInfo element from W3C XML Signature to ASCII and add signature support</p></remark>
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</revision>
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<revision>
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<version>0.7</version>
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<date>2008-03-03</date>
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<initials>psa</initials>
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<remark><p>Changed temporary namespace per XEP-0053 procedures; corrected several small errors in the text and examples.</p></remark>
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</revision>
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<revision>
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<version>0.6</version>
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<date>2007-08-15</date>
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<initials>psa</initials>
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<remark><p>More clearly explained node creation and key publication workflows.</p></remark>
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</revision>
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<revision>
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<version>0.5</version>
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<date>2007-03-05</date>
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<initials>ip</initials>
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<remark><p>Merged node creation and first publish examples; recommended the value of each <KeyName/> element and id attribute is set to the key fingerprint; added fprint element and more examples</p></remark>
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</revision>
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<revision>
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<version>0.4</version>
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<date>2006-11-27</date>
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<initials>ip</initials>
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<remark><p>Added jid attribute and send use case; changed namespace</p></remark>
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</revision>
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<revision>
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<version>0.3</version>
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<date>2006-11-20</date>
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<initials>ip</initials>
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<remark><p>Specified that PEP nodes SHOULD be persistent</p></remark>
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</revision>
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<revision>
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<version>0.2</version>
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<date>2006-09-29</date>
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<initials>ip</initials>
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<remark><p>Replaced pubkey and key elements with the KeyInfo element defined in W3C XML Signature</p></remark>
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</revision>
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<revision>
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<version>0.1</version>
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<date>2006-07-18</date>
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<initials>ip</initials>
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<remark><p>Initial version.</p></remark>
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</revision>
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</header>
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<section1 topic='Introduction' anchor='intro'>
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<p>This document defines different methods an entity MAY use for publishing its long-term public keys:</p>
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<ul>
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<li>Publishing public keys to a set of subscribers.</li>
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<li>Querying another entity for its public keys.</li>
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<li>Sign one key with another</li>
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</ul>
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<p>An entity MAY have multiple public keys with different formats, signatures, algorithms, strengths and expiry dates. Each client used by a user MAY use different keys. Guidelines how to manage different public keys in included in this document.</p>
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</section1>
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<section1 topic='The KeyInfo Format' anchor='keyinfo'>
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<p>This document does not use the 'http://www.w3.org/2000/09/xmldsig#' namespace as specified in &w3xmlsig; because it is too complicated and the complexity is not needed for this use case. The <keyinfo/> element defined in the 'urn:xmpp:pubkey:0' namespace &VNOTE; is based on the ASCII output most cryptographic libraries support. It has two parts: the public key data and signatures from other keys (optional). The optional argument 'jid' SHOULD be set if the X.509 certificate or OpenPGP key does not belong to the user providing it to another.</p>
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<section2 topic='X.509 Certificate' anchor='x509'>
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<p>The public key data is the X.509 certificate in DER encoding. To be included in an XML stream the data is Base64 encoded.</p>
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<example caption='X.509 Certificate'><![CDATA[
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<keyinfo xmlns='urn:xmpp:pubkey:0'>
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<x509cert>
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MIICCTCCAXKgAwIBAgIJALhU0Id6xxwQMA0GCSqGSIb3DQEBBQUAMA4xDDAKBgNV
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BAMTA2ZvbzAeFw0wNzEyMjgyMDA1MTRaFw0wODEyMjcyMDA1MTRaMA4xDDAKBgNV
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BAMTA2ZvbzCBnzANBgkqhkiG9w0BAQEFAAOBjQAwgYkCgYEA0DPcfeJzKWLGE22p
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RMINLKr+CxqozF14DqkXkLUwGzTqYRi49yK6aebZ9ssFspTTjqa2uNpw1U32748t
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qU6bpACWHbcC+eZ/hm5KymXBhL3Vjfb/dW0xrtxjI9JRFgrgWAyxndlNZUpN2s3D
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hKDfVgpPSx/Zp8d/ubbARxqZZZkCAwEAAaNvMG0wHQYDVR0OBBYEFJWwFqmSRGcx
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YXmQfdF+XBWkeML4MD4GA1UdIwQ3MDWAFJWwFqmSRGcxYXmQfdF+XBWkeML4oRKk
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EDAOMQwwCgYDVQQDEwNmb2+CCQC4VNCHesccEDAMBgNVHRMEBTADAQH/MA0GCSqG
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SIb3DQEBBQUAA4GBAIhlUeGZ0d0msNVxYWAXg2lRsJt9INHJQTCJMmoUeTtaRjyp
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ffJtuopguNNBDn+MjrEp2/+zLNMahDYLXaTVmBf6zvY0hzB9Ih0kNTh23Fb5j+yK
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QChPXQUo0EGCaODWhfhKRNdseUozfNWOz9iTgMGw8eYNLllQRL//iAOfOr/8
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</x509cert>
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</keyinfo>
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]]></example>
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</section2>
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<section2 topic='OpenPGP' anchor='openpgp'>
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<p>The public key data is the OpenPGP public key (&rfc4880;) using binary output. Like X.509 certificates the data MUST be Base64 encoded to fit in an XML stream.</p>
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<example caption='OpenPGP Public Key'><![CDATA[
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<keyinfo xmlns='urn:xmpp:pubkey:0'
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jid='romeo@montague.net'>
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<pgpdata>
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mQGiBDsKPy8RBACG1vVC8+5jMbtr8YUSfL2ciIu/Zb7/dDhwFd4iFlH7BIEt3RjR
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wmiCUw/pcL8LHav7L2L4/Yxm8peJxyK0c11tP5Mq8kG3v55BSkZzn3fwKilEYG1c
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rkOPWMEHds3c8kLDn+WNyxrSpw10EyJSsXc0edBdl7eLHiNQsCNmPpZhvwCg8uCQ
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...
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HDU4Qg9lslDyfa2pHqkweHvC/LmIxrZeCSxOgSMLV8bqbbra1n3F4vdqgc8VP8I2
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o9wBSf3HMohGBBgRAgAGBQI7Cj82AAoJEE598tACtM5EuWIAn0tHJF+Bk7pPAngp
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hFOdFgS8UBSAAJ9ZPviS2XDzrWRpiyKV+hDqO/WTHA==
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</pgpdata>
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</keyinfo>
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]]></example>
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</section2>
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<section2 topic='Signatures' anchor='signature'>
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<p>Besides the data, a key can have one or more signatures. A signature can be used to sign an X.509 certificate with an OpenPGP key or the other way around. This makes it possible to verify a self-signed X.509 certificate with the OpenPGP web-of-trust. A second use case is the concept of user and client keys. A user MAY choose to use a different X.509 certificates for each client for &xtls; or &saslext;. All these client key can be signed by a user key. Once the user key is known, all clients can be verified. This XMPP based approach makes it possible to use self-signed certificates without setting up a CA (see <link url='#management'>Key Management Guidelines for Secure End-to-End Communication</link>).</p>
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<p>The signature has an issuer and the signature data. The issuer contains the fingerprint of the key that was used to create the signature. An optional argument 'jid' SHOULD be set if the issuer has a different base JID than the key to sign. This makes it possible to find the issuer key using PEP (see <link url='#pub'>Public Key Publication via PEP</link>).</p>
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<p>While OpenPGP defines how to sign a string, X.509 does not specify the hash algorithm. For X.509 the signature data MUST contain an attribute what hash and sign algorithms were used. This document only defines 'RSA-SHA1' at this time. To make it easier to use standard cryptographic libraries the hash MUST contain the ASN.1 BER SHA1 algorithm designator prefix required in PKCS1. See XML-SIG section 6.4.2 how to hash and sign a string using RSA-SHA1. In most cases the cryptographic library will automatically take care of this. The data to sign is the X.509 certificate in DER encoding or the OpenPGP binary string of the fingerprint (the provided key data without Base64 encoding).</p>
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<p>The next example contains an X.509 certificate signed by the key defined in the first example.</p>
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<example caption='X.509 Certificate with external Signature'><![CDATA[
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<keyinfo xmlns='urn:xmpp:pubkey:0'>
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<x509cert>
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MIICXDCCAcWgAwIBAgIJAKBfLqul2lj3MA0GCSqGSIb3DQEBBQUAMCkxJzAlBgNV
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BAMUHmRtZXllckBqYWJiZXIuY29tXDJmdGVzdGNsaWVudDAeFw0wODA5MDYxOTI0
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MjVaFw0wOTA5MDYxOTI0MjVaMCkxJzAlBgNVBAMUHmRtZXllckBqYWJiZXIuY29t
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XDJmdGVzdGNsaWVudDCBnzANBgkqhkiG9w0BAQEFAAOBjQAwgYkCgYEAwaRLyj7J
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/mmliYhjEwGnRGRs6gmcPaIywEK2QLFz6c3/RmRabYbIOE0iZ22D33TguSNQBWfd
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lweT3bBETUhd3yuCcqWO5Ptiq/6wulMlxVeV5mxwNP/IF94VPWj0jHbRJcU8ZhS4
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UnX6R5q6OSfBGdUU4mYKdiaHpgqTAO9eeqUCAwEAAaOBizCBiDAdBgNVHQ4EFgQU
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b8touIdFuXF5clv2I/S1aOOFdN4wWQYDVR0jBFIwUIAUb8touIdFuXF5clv2I/S1
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aOOFdN6hLaQrMCkxJzAlBgNVBAMUHmRtZXllckBqYWJiZXIuY29tXDJmdGVzdGNs
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aWVudIIJAKBfLqul2lj3MAwGA1UdEwQFMAMBAf8wDQYJKoZIhvcNAQEFBQADgYEA
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pA5tI1J9Qpn3jSoQctFksRLb2H3A48R3rU8/qnarwE/AyOvth3k3ulLEmhJBT+0S
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mVb6WzrZEA/2plu7DhR8ylhuvJv6cAEIN+TPha3yzO2P8uoVZf7hdunOhMLl2Z6w
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xEfiGI5X9OsaMeFOQa+B2C3uUVAMLbVV7Rp/qQkai1Y=
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</x509cert>
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<signature>
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<issuer algo='sha1'>428b1358a286430f628da23fb33ddaf6e474f5c5</issuer>
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<value method='RSA-SHA1'>
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E3q/UkjRR3zcZMcIIoE2sSVKUATl26zyzO1Pmoe96p8apW91c3a0KqkQp1ZMBqXX
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+e2ImqQ79CKv+9qzXitxx+V4EcniKN0ZsSR+9ZbfflxkOvmBa2rpq9hFE1NYyfuT
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fsAZkRhAGlP7P5ELcvhqJ4WL6qBPYQU2NEnbVlcZSbA=
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</value>
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</signature>
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</keyinfo>
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]]></example>
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</section2>
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</section1>
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<section1 topic='Public Key Publication via PEP' anchor='pub'>
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<p>An entity SHOULD follow the best practices defined in &xep0222; to publish its long-term public keys via its own server. Processes for doing so are described in the following sections.</p>
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<section2 topic='Creating the Node' anchor='pub-create'>
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<p>If the pubkeys PEP node does not exist already then the entity needs to create it. The node MUST have a NodeID of "urn:xmpp:pubkey:0" &VNOTE;.</p>
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<p>The node MUST be configured as follows:</p>
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<ul>
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<li>Items published to the node are persistent (this is done by setting the "persist_items" option to true).</li>
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<li>Keys will be pushed to subscribers only when new keys are published, not when subscribers become newly available or when a new subscription is created (this is done by setting the "send_last_published_item" option to "never").</li>
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</ul>
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<p>If the user wants to control access to his/her identity (see <link url='#security'>Security Considerations</link>) then the node access model SHOULD be something other than "open" (this can be done by setting the "access_model" option to a value of "authorize", "presence", "roster", or "whitelist").</p>
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<example caption='Entity Creates Node'><![CDATA[
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<iq from='juliet@capulet.com/balcony'
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id='hfgt54ew'
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type='set'>
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<pubsub xmlns='http://jabber.org/protocol/pubsub'>
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<create node='urn:xmpp:pubkey:0'/>
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<configure>
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<x xmlns='jabber:x:data' type='submit'>
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<field var='FORM_TYPE' type='hidden'>
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<value>http://jabber.org/protocol/pubsub#node_config</value>
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</field>
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<field var='pubsub#persist_items'>
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<value>1</value>
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</field>
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<field var='pubsub#send_last_published_item'>
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<value>never</value>
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</field>
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<field var='pubsub#access_model'>
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<value>roster</value>
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</field>
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<field var='pubsub#roster_groups_allowed'>
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<value>friends</value>
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</field>
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</x>
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</configure>
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</pubsub>
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</iq>
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]]></example>
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<p>Alternatively, if the entity's pubsub service supports both the "auto-create" and "publish-options" features, then the entity MAY create the node by publishing a key and in the first publish including a <publish-options/> element. However, note that not all pubsub services support this feature, since it is optional in &xep0060;.</p>
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<example caption='Entity Auto-Creates Node and Publishes an RSA Key'><![CDATA[
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<iq from='juliet@capulet.com/balcony'
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id='hfgt54ed'
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type='set'>
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<pubsub xmlns='http://jabber.org/protocol/pubsub'>
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<publish node='urn:xmpp:pubkey:0'>
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<item id='Juliet-PGP-Key-Hash'>
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<keyinfo xmlns='urn:xmpp:pubkey:0'>
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<openpgp>PKP-Key-Base64-encoded</openpgp>
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</keyinfo>
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</item>
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</publish>
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<configure>
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<x xmlns='jabber:x:data' type='submit'>
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<field var='FORM_TYPE' type='hidden'>
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<value>http://jabber.org/protocol/pubsub#node_config</value>
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</field>
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<field var='pubsub#persist_items'>
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<value>1</value>
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</field>
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<field var='pubsub#send_last_published_item'>
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<value>never</value>
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</field>
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<field var='pubsub#access_model'>
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<value>roster</value>
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</field>
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<field var='pubsub#roster_groups_allowed'>
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<value>friends</value>
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</field>
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</x>
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</configure>
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</pubsub>
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</iq>
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]]></example>
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</section2>
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<section2 topic='Publishing a Key' anchor='pub-publish'>
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<p>The entity publishes a key by sending a pubsub publish request to the pubsub service. A previously published key can be updated by re-publishing the key using the same ItemID. The value of the ItemID SHOULD be the fingerprint of the X.509 certificate or the OpenPGP key and SHOULD be written in lower case. Since X.509 has no standard fingerprint mechanisms, the SHA1 value in hex is SHOULD be used as ItemID. Therefore subscribers or other interested entities are able to request a single key by specifying its fingerprint (for example, when a subscriber is using <cite>XTLS</cite>).</p>
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<example caption='Entity Publishes an X.509 Certificate to its Server'><![CDATA[
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<iq from='juliet@capulet.com/balcony'
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id='gfy54e66'
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type='set'>
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<pubsub xmlns='http://jabber.org/protocol/pubsub'>
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<publish node='urn:xmpp:pubkey:0'>
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<item id='Juliet-X509-Cert-Hash'>
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<keyinfo xmlns='urn:xmpp:pubkey:0'>
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<x509cert>
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Certificate-in-DER-format-Base64-encoded
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</x509cert>
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<signature>
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<issuer>Juliet-PGP-Key-Hash</issuer>
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<value>
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Signature-Base64-encoded
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</value>
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</signature>
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</keyinfo>
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</item>
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</publish>
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</pubsub>
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</iq>
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]]></example>
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<p>After the account owner publishes the key, the pubsub service shall send a notification to each subscriber or otherwise authorized and interested entity.</p>
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<example caption='Pubsub Service Sends Notification with Key'><![CDATA[
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<message to='romeo@montague.net/garden' from='juliet@capulet.com' type='headline'>
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<event xmlns='http://jabber.org/protocol/pubsub#event'>
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<items node='urn:xmpp:pubkey:0'>
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<item id='Juliet-X509-Cert-Hash'>
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<keyinfo xmlns='urn:xmpp:pubkey:0'>
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<x509cert>
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Certificate-in-DER-format-Base64-encoded
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</x509cert>
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<signature>
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<issuer>Juliet-PGP-Key-Hash</issuer>
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<value>
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Signature-Base64-encoded
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</value>
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</signature>
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</keyinfo>
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</item>
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</items>
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</event>
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<addresses xmlns='http://jabber.org/protocol/address'>
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<address type='replyto' jid='juliet@capulet.com/balcony'/>
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</addresses>
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</message>
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]]></example>
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<p>Note: The stanza containing the event notification (see example above) MAY also include 'replyto' data (as specified by the &xep0033; protocol) to provide an explicit association between the published data and the <em>resource</em> that published it.</p>
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</section2>
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</section1>
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<section1 topic='Public Key Retrieval via PEP' anchor='retrieve'>
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<example caption='Subscriber Requests Keys from Account'><![CDATA[
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<iq from='romeo@montague.net/garden'
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to='juliet@capulet.com'
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id='hfgtredy'
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type='get'>
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<pubsub xmlns='http://jabber.org/protocol/pubsub'>
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<items node='urn:xmpp:pubkey:0'/>
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</pubsub>
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</iq>
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]]></example>
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<example caption='Entity's Server Returns Keys to Subscriber'><![CDATA[
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<iq from='juliet@capulet.com'
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to='romeo@montague.net/garden'
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id='hfgtredy'
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type='result'>
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<pubsub xmlns='http://jabber.org/protocol/pubsub'>
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<items node='urn:xmpp:pubkey:0'>
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<item id='Juliet-PGP-Key-Hash'>
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<keyinfo xmlns='urn:xmpp:pubkey:0'>
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<pgpdata>
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PKP-Key-Base64-encoded
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</pgpdata>
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</keyinfo>
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</item>
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<item id='Juliet-X509-Cert-Hash'>
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<keyinfo xmlns='urn:xmpp:pubkey:0'>
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<x509cert>
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Certificate-in-DER-format-Base64-encoded
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</x509cert>
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</keyinfo>
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</item>
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</items>
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</pubsub>
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</iq>
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]]></example>
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<example caption='Subscriber Requests Specific Key'><![CDATA[
|
|
<iq from='romeo@montague.net/garden'
|
|
to='juliet@capulet.com'
|
|
id='gf654ewq'
|
|
type='get'>
|
|
<pubsub xmlns='http://jabber.org/protocol/pubsub'>
|
|
<items node='urn:xmpp:pubkey:0'>
|
|
<item id='Juliet-X509-Cert-Hash'/>
|
|
</items>
|
|
</pubsub>
|
|
</iq>
|
|
]]></example>
|
|
<example caption='Entity's Server Returns Key to Subscriber'><![CDATA[
|
|
<iq from='juliet@capulet.com'
|
|
to='romeo@montague.net/garden'
|
|
id='gf654ewq'
|
|
type='result'>
|
|
<pubsub xmlns='http://jabber.org/protocol/pubsub'>
|
|
<items node='urn:xmpp:pubkey:0'>
|
|
<item id='Juliet-X509-Cert-Hash'>
|
|
<keyinfo xmlns='urn:xmpp:pubkey:0'>
|
|
<x509cert>
|
|
Certificate-in-DER-format-Base64-encoded
|
|
</x509cert>
|
|
</keyinfo>
|
|
</item>
|
|
</items>
|
|
</pubsub>
|
|
</iq>
|
|
]]></example>
|
|
</section1>
|
|
|
|
<section1 topic='Requesting Public Keys Directly From Another Entity' anchor='request'>
|
|
<p>If an entity wishes to request the public keys of another entity and it cannot access the keys via <cite>Personal Eventing via Pubsub</cite>, then the entity MAY send an &IQ; of type 'get' to the other entity, containing an empty <pubkeys/> element qualified by the 'urn:xmpp:pubkey:0' namespace &VNOTE;.</p>
|
|
<example caption='Public keys request'><![CDATA[
|
|
<iq from='romeo@montague.net/garden'
|
|
to='juliet@capulet.com/balcony'
|
|
id='hfgt654s'
|
|
type='get'>
|
|
<pubkeys xmlns='urn:xmpp:pubkey:0'/>
|
|
</iq>
|
|
]]></example>
|
|
<p>The other entity MUST make a careful access control decision before returning only those public keys for which it holds the corresponding private key (not necessarily the full list of keys being published via <cite>Personal Eventing via Pubsub</cite>). The client MAY also include the public key which was used to sign its keys even if it does not hold the private key. In that case the <keyinfo/> element MUST contain the 'jid' attribute of the public key even it is belongs to the same user.</p>
|
|
<example caption='Successful public keys response'><![CDATA[
|
|
<iq from='juliet@capulet.com/balcony'
|
|
to='romeo@montague.net/garden'
|
|
id='hfgt654s'
|
|
type='result'>
|
|
<pubkeys xmlns='urn:xmpp:pubkey:0'>
|
|
<keyinfo>
|
|
<x509cert>Juliet-X509-Client-Cert</x509cert>
|
|
<signature>
|
|
<issuer algo='sha1'>Juliet-X509-User-Cert-Hash</issuer>
|
|
<value method='RSA-SHA1'>
|
|
Signature-Base64-encoded
|
|
</value>
|
|
</signature>
|
|
</keyinfo>
|
|
<keyinfo jid='juliet@capulet.com'>
|
|
<x509cert>Juliet-X509-User-Cert</x509cert>
|
|
</keyinfo>
|
|
<keyinfo>
|
|
<pgpdata>Juliet-PGP-Key</pgpdata>
|
|
</keyinfo>
|
|
</pubkeys>
|
|
</iq>
|
|
]]></example>
|
|
<p>If the receiving entity decides not to return the public keys, it MUST return an IQ error, which SHOULD be &unavailable; (to avoid divulging presence to unauthorized entities), but MAY be some other appropriate error, such as &forbidden; or ¬allowed;:</p>
|
|
<example caption='Access to public keys denied'><![CDATA[
|
|
<iq from='juliet@capulet.com/balcony'
|
|
to='romeo@montague.net/garden'
|
|
id='hfgt654s'
|
|
type='error'>
|
|
<pubkeys xmlns='urn:xmpp:pubkey:0'/>
|
|
<error code='503' type='cancel'>
|
|
<service-unavailable xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
|
|
</error>
|
|
</iq>
|
|
]]></example>
|
|
<p>An entity MAY request one or more specific public keys by specifying their fingerprints (see <link url='#pub'>Public Key Publication via PEP</link>) as the content of <fingerprint/> child elements:</p>
|
|
<example caption='Specific public keys request'><![CDATA[
|
|
<iq from='juliet@capulet.com/balcony'
|
|
to='romeo@montague.net/garden'
|
|
id='54fgtyre'
|
|
type='get'>
|
|
<pubkeys xmlns='urn:xmpp:pubkey:0'>
|
|
<fingerprint algo='sha1'>Juliet-X509-Cert-Hash</fingerprint>
|
|
<fingerprint>Juliet-PKP-Hash</fingerprint>
|
|
</pubkeys>
|
|
</iq>
|
|
]]></example>
|
|
<example caption='Successful specific public keys response'><![CDATA[
|
|
<iq from='juliet@capulet.com/balcony'
|
|
to='romeo@montague.net/garden'
|
|
id='54fgtyre'
|
|
type='result'>
|
|
<pubkeys xmlns='urn:xmpp:pubkey:0'>
|
|
<keyinfo>
|
|
<x509cert>
|
|
Certificate-in-DER-format-Base64-encoded
|
|
</x509cert>
|
|
</keyinfo>
|
|
<keyinfo>
|
|
<pgpdata>
|
|
PKP-Key-Base64-encoded
|
|
</pgpdata>
|
|
</keyinfo>
|
|
</pubkeys>
|
|
</iq>
|
|
]]></example>
|
|
</section1>
|
|
|
|
<section1 topic='Requesting Public Keys Directly From a Third Party' anchor='third'>
|
|
<p>An entity can request the public keys of another entity from a third party using the 'jid' attribute of the <pubkeys/> element to specify the JID that the keys belong to:</p>
|
|
<example caption='Requesting public keys from a third-party'><![CDATA[
|
|
<iq from='juliet@capulet.com/balcony'
|
|
to='romeo@montague.net/garden'
|
|
id='gftrse3w'
|
|
type='get'>
|
|
<pubkeys xmlns='urn:xmpp:pubkey:0' jid='benvolio@montague.net'/>
|
|
</iq>
|
|
]]></example>
|
|
<example caption='Third-party responds with public keys'><![CDATA[
|
|
<iq from='romeo@montague.net/garden'
|
|
to='juliet@capulet.com/balcony'
|
|
id='gftrse3w'
|
|
type='result'>
|
|
<pubkeys xmlns='urn:xmpp:pubkey:0' jid='benvolio@montague.net'>
|
|
<keyinfo jid='benvolio@montague.net'>
|
|
...
|
|
</keyinfo>
|
|
<keyinfo jid='benvolio@montague.net'>
|
|
...
|
|
</keyinfo>
|
|
</pubkeys>
|
|
</iq>
|
|
]]></example>
|
|
<example caption='Third party has no copies of the keys'><![CDATA[
|
|
<iq from='romeo@montague.net/garden'
|
|
to='juliet@capulet.com/balcony'
|
|
id='gftrse3w'
|
|
type='error'>
|
|
<pubkeys xmlns='urn:xmpp:pubkey:0' jid='benvolio@montague.net'/>
|
|
<error code='404' type='cancel'>
|
|
<item-not-found xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
|
|
</error>
|
|
</iq>
|
|
]]></example>
|
|
</section1>
|
|
|
|
<section1 topic='Sending Public Keys Directly To Another Entity' anchor='send'>
|
|
<p>If an entity wishes to send public keys to another entity then it MAY include them in a &MESSAGE; stanza. The entity MAY use the 'jid' attribute of the <keyinfo/> element to specify the JID that the keys belong to. If no 'jid' attribute is specified then the other entity SHOULD assume the keys belong to the sender of the stanza.</p>
|
|
<example caption='Sending public keys'><![CDATA[
|
|
<message from='romeo@montague.net/garden'
|
|
to='juliet@capulet.com/balcony'>
|
|
<pubkeys xmlns='urn:xmpp:pubkey:0'>
|
|
<keyinfo>
|
|
...
|
|
</keyinfo>
|
|
<keyinfo jid='benvolio@montague.net'>
|
|
...
|
|
</keyinfo>
|
|
</pubkeys>
|
|
</message>
|
|
]]></example>
|
|
</section1>
|
|
|
|
<section1 topic='Signing Public Keys' anchor='sign'>
|
|
<p>A client can add another client's X.509 certificate to the pubsub node or send it directly to another client, and the client wants that certificate signed with the user's private key. If the client is not in possession of the private key, it can send a 'sign' request to another client of the user having access to the certificate.</p>
|
|
<example caption='Client sends Signing Request'><![CDATA[
|
|
<iq from='juliet@capulet.com/chamber'
|
|
to='juliet@capulet.com/balcony'
|
|
type='set'
|
|
id='hft65du8'>
|
|
<sign node='urn:xmpp:pubkey:0'>
|
|
<issuer algo='sha1'>UserCertificateHash</issuer>
|
|
<pubkeys>
|
|
<keyinfo>
|
|
<x509cert>
|
|
Certificate-in-DER-format-Base64-encoded
|
|
<x509cert/>
|
|
</keyinfo>
|
|
<pubkeys>
|
|
</sign>
|
|
</iq>
|
|
]]></example>
|
|
<p>The signing client SHOULD only accept signing requests from clients of the same user (sharing a bare JID) and it is RECOMMENDED to use a secure end-to-end communicate according to &xtls; or &xep0250; for serverless-messing.</p>
|
|
<example caption='Signing Client Returns Keys'><![CDATA[
|
|
<iq from='juliet@capulet.com/balcony'
|
|
to='juliet@capulet.com/chamber'
|
|
type='result'
|
|
id='hft65du8'>
|
|
<pubkeys>
|
|
<keyinfo>
|
|
<x509cert>
|
|
Certificate-in-DER-format-Base64-encoded
|
|
<x509cert/>
|
|
<signature>
|
|
<issuer algo='sha1'>UserCertificateHash</issuer>
|
|
<value method='RSA-SHA1'>
|
|
Signature-Base64-encoded
|
|
</value>
|
|
</signature>
|
|
</keyinfo>
|
|
<pubkeys>
|
|
</iq>
|
|
]]></example>
|
|
<p>Possible error conditions are that the signing client does not have the requested private key, the client is not authorized to request a signature, or that the signing client requires a secure connection and the request was issued over an insecure link.</p>
|
|
<example caption='Error Conditions'><![CDATA[
|
|
<error code='404' type='cancel'>
|
|
<item-not-found xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
|
|
</error>
|
|
|
|
<error type='auth'>
|
|
<forbidden xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
|
|
</error>
|
|
|
|
<error type='cancel'>
|
|
<not-acceptable xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
|
|
<security-required xmlns='urn:xmpp:jingle:errors:0'/>
|
|
</error>
|
|
]]></example>
|
|
</section1>
|
|
|
|
<section1 topic='Key Management Guidelines for Secure End-to-End Communication' anchor='management'>
|
|
<p>Different X.509 certificates for each client, a user X.509 certificate to sign client certificates, and secure communication with friends make the scenario quite confusing. This section provides guidelines how to manage the different public keys and what kind of key to sign. The desired use case is to manage for secure end-to-end communication as defined by <cite>XTLS</cite>.</p>
|
|
<ul>
|
|
<li><p>Each client has its own certificate. This certificate is most likely self-signed.</p></li>
|
|
<li><p>The user has a user certificate and one or more clients can have access to the user's private key to sign certificates. To bootstrap the system, one client generates the certificate on behalf of the user.</p></li>
|
|
<li><p>Users SHOULD sign all their client certificates with their user certificate. To accomplish this in a userfriendly way, the user MAY log into the account with more than one client simultaneously. One client MUST have the user's private key or is trusted to issue a 'sign' request. The two clients open a secure connection between themselves based on TLS-SRP (see <cite>XTLS, Section 6</cite>). After a secure communicate between the two clients is established, the client without the user certificate requests its certificate to be signed. After that it can be uploaded to the pubsub node. The new client SHOULD also request the user certificate to be able to validate signatures for other clients.</p></li>
|
|
<li><p>If a client opens a secure connection to another user based on TLS-SRP, it SHOULD request the user certificate of its peer. It will either sign the certificate itself or ask another client with the user's private key to do so. The friend's user certificate can then be uploaded to the pubsub node of the user (not the friend). The <keyinfo/> element SHOULD contain the bare JID of the friend in the 'jid' attribute.</p></li>
|
|
<li><p>If a client wants to open a secure end-to-end connection to another client of the same user, it SHOULD check the pubsub node for the certificate. The certificate MUST be signed by the user's certificate.</p></li>
|
|
<li><p>If a client wants to open a secure end-to-end connection to a client of another user, it SHOULD check the its pubsub node for the friend's user certificate and the friend's pubsub node for the client certificate. The friend's user certificate MUST be signed by its own user certificate and the clients certificate MUST be signed by the friend's user certificate.</p></li>
|
|
</ul>
|
|
<p>If a user possess an OpenPGP key, the user certificate SHOULD be signed with that key. This allows another users to verify the certificate based on the OpenPGP web-of-trust, and two users might be able to bootstrap a secure communicate without the usage of TLS-SRP.</p>
|
|
</section1>
|
|
|
|
<section1 topic='Determining Support' anchor='support'>
|
|
<p>If an entity can sign certificates or OpenPGP keys with the user's private key, it MUST report that by including a service discovery feature of "urn:xmpp:pubkey:0:sign" in response to disco#info requests &VNOTE;.</p>
|
|
<example caption="Initial Service Discovery Information Request"><![CDATA[
|
|
<iq from='juliet@capulet.com/chamber'
|
|
to='juliet@capulet.com/balcony'
|
|
id='gfd68yt4'
|
|
type='get'>
|
|
<query xmlns='http://jabber.org/protocol/disco#info'/>
|
|
</iq>
|
|
]]></example>
|
|
<example caption="Service Discovery Information Response"><![CDATA[
|
|
<iq from='juliet@capulet.com/balcony'
|
|
to='juliet@capulet.com/chamber'
|
|
id='gfd68yt4'
|
|
type='result'>
|
|
<query xmlns='http://jabber.org/protocol/disco#info'>
|
|
<feature var='urn:xmpp:pubkey:0'/>
|
|
<feature var='urn:xmpp:pubkey:0:sign'/>
|
|
</query>
|
|
</iq>
|
|
]]></example>
|
|
</section1>
|
|
|
|
<section1 topic='Security Considerations' anchor='security'>
|
|
<p>The reliable association between a user or entity and its public keys is beyond the scope of this document. However, each client SHOULD maintain its own secure library of the public keys (or the "fingerprints" of the keys) it associates with other users (not necessarily JIDs).</p>
|
|
<p>Whenever public keys are published an identity is typically associated with a JID. Although the public keys are public information, it can be critically important for the user of the JID to keep his identity secret from all but a few specified people. Implementors MUST take great care to ensure that the identity of the user of a JID is never divulged to anyone except the entities who have been permitted by the user to access the public key.</p>
|
|
<p>The usage of secure end-to-end communication is RECOMMENDED for exchanging public keys without a pubsub service.</p>
|
|
</section1>
|
|
|
|
<section1 topic='IANA Considerations' anchor='iana'>
|
|
<p>This document requires no interaction with &IANA;.</p>
|
|
</section1>
|
|
|
|
<section1 topic='XMPP Registrar Considerations' anchor='registrar'>
|
|
<section2 topic='Protocol Namespaces' anchor='registrar-ns'>
|
|
<p>This specification defines the following XML namespace:</p>
|
|
<ul>
|
|
<li>urn:xmpp:pubkey:0</li>
|
|
</ul>
|
|
<p>Upon advancement of this specification to a status of Draft, the ®ISTRAR; shall add this namespace in the registry located at &NAMESPACES;, as described in Section 4 of &xep0053;.</p>
|
|
</section2>
|
|
<section2 topic='Protocol Versioning' anchor='registrar-versioning'>
|
|
&NSVER;
|
|
</section2>
|
|
<section2 topic='Service Discovery Features' anchor='registrar-features'>
|
|
<p>The XMPP Registrar shall include the following features in its registry of service discovery features (see &DISCOFEATURES;), where the string "urn:xmpp:pubkey:0" shall be replaced with the URN issued by the XMPP Registrar:</p>
|
|
<code><![CDATA[
|
|
<var>
|
|
<name>urn:xmpp:pubkey:0:sign</name>
|
|
<desc>The client is in possession of the user's private client to sign certificates.</desc>
|
|
<doc>XEP-0189</doc>
|
|
</var>
|
|
]]></code>
|
|
</section2>
|
|
</section1>
|
|
|
|
<section1 topic='XML Schema' anchor='schema'>
|
|
<code><![CDATA[
|
|
<?xml version='1.0' encoding='UTF-8'?>
|
|
|
|
<xs:schema
|
|
xmlns:xs='http://www.w3.org/2001/XMLSchema'
|
|
targetNamespace='urn:xmpp:pubkey:0'
|
|
xmlns='urn:xmpp:pubkey:0'
|
|
elementFormDefault='qualified'>
|
|
|
|
<xs:element name='pubkeys'>
|
|
<xs:complexType>
|
|
<xs:choice>
|
|
<xs:element ref='fingerprint'/>
|
|
<xs:element ref='keyinfo'/>
|
|
</xs:choice>
|
|
<xs:attribute name='jid' type='xs:string' use='optional'/>
|
|
<xs:anyAttribute namespace='##any' processContents='lax'/>
|
|
</xs:complexType>
|
|
</xs:element>
|
|
|
|
<xs:element name='keyinfo'>
|
|
<xs:complexType>
|
|
<xs:element name='name' minOccurs='1' maxOccurs='1' type='xs:string'/>
|
|
<xs:choice minOccurs='0' maxOccurs='1'>
|
|
<xs:element name='x509cert' type='xs:string'/>
|
|
<xs:element name='pgpdata' type='xs:string'/>
|
|
</xs:choice>
|
|
<xs:element ref='signature' minOccurs='0' maxOccurs='unbounded'/>
|
|
<xs:attribute name='jid' type='xs:string' use='optional'/>
|
|
</xs:complexType>
|
|
</xs:element>
|
|
|
|
<xs:element name='fingerprint'>
|
|
<xs:complexType>
|
|
<xs:simpleContent>
|
|
<xs:extension base='xs:string'>
|
|
<xs:attribute name='algo' type='xs:string' use='optional'/>
|
|
</xs:extension>
|
|
</xs:simpleContent>
|
|
</xs:complexType>
|
|
</xs:element>
|
|
|
|
<xs:element name='signature'>
|
|
<xs:complexType>
|
|
<xs:sequence>
|
|
<xs:element ref='issuer'/>
|
|
<xs:element ref='value'/>
|
|
</xs:sequence>
|
|
</xs:complexType>
|
|
</xs:element>
|
|
|
|
<xs:element name='issuer'>
|
|
<xs:complexType>
|
|
<xs:simpleContent>
|
|
<xs:extension base='xs:string'>
|
|
<xs:attribute name='algo' type='xs:string' use='optional'/>
|
|
<xs:attribute name='jid' type='xs:string' use='optional'/>
|
|
</xs:extension>
|
|
</xs:simpleContent>
|
|
</xs:complexType>
|
|
</xs:element>
|
|
|
|
<xs:element name='value'>
|
|
<xs:complexType>
|
|
<xs:simpleContent>
|
|
<xs:extension base='xs:string'>
|
|
<xs:attribute name='method' type='xs:string' use='optional'/>
|
|
</xs:extension>
|
|
</xs:simpleContent>
|
|
</xs:complexType>
|
|
</xs:element>
|
|
|
|
<xs:element name='sign'>
|
|
<xs:complexType>
|
|
<xs:sequence>
|
|
<xs:element ref='issuer'/>
|
|
<xs:element ref='pubkeys'/>
|
|
</xs:sequence>
|
|
</xs:complexType>
|
|
</xs:element>
|
|
|
|
</xs:schema>
|
|
]]></code>
|
|
</section1>
|
|
</xep>
|