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doc (encryption): update pubsub encryption specifications.
author Goffi <goffi@goffi.org>
date Sat, 13 Jul 2024 17:45:47 +0200
parents c4418949aa37
children
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4281:9e63e02318ec 4282:8da377040ba6
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42 Pubsub is not encrypted the same way as messages, because you generally need to access all 42 Pubsub is not encrypted the same way as messages, because you generally need to access all
43 items of a pubsub node, even if you get access to the node once items have already been 43 items of a pubsub node, even if you get access to the node once items have already been
44 published. 44 published.
45 45
46 E2ee is currently done using `OpenPGP`_ (or OX for PubSub: OXPS). Each item is encrypted 46 E2ee is currently done using `OpenPGP`_ (`XEP-0473: OpenPGP for XMPP Pubsub`_). Each item is encrypted
47 using a **symmetric** encryption, which mean that the same key (called "shared secret") is 47 using a **symmetric** encryption, which mean that the same key (called "shared secret") is
48 used both to encrypt and decrypt an item, and is shared between all people who must access 48 used both to encrypt and decrypt an item, and is shared between all people who must access
49 or publish to the pubsub node (i.e. blog, event calendar, etc). This is done this way to 49 or publish to the pubsub node (i.e. blog, event calendar, etc). This is done this way to
50 make it easy to add a new members, who can then access all archives of the node, but this 50 make it easy to add a new members, who can then access all archives of the node, but this
51 also means that if the shared secret is compromised (i.e. somebody who should not has 51 also means that if the shared secret is compromised (i.e. somebody who should not has
52 obtained a copy), all items made with this secret are accessible to the persons in 52 obtained a copy), all items made with this secret are accessible to the persons in
53 possession of the secret. 53 possession of the secret.
54
55 .. note::
56
57 OXPS specification is not currently an official XEP (XMPP Extension Protocol), it is
58 about to be examinated by "XMPP council". This documentation will be updated with the
59 evolution of the situation. You can read current specification proposal at
60 https://xmpp.org/extensions/inbox/pubsub-encryption.html (which is inaccessible due to
61 a 404 error at the time of writting, this should be fixed hopefully when you read this
62 documentation).
63 54
64 To make an encrypted pubsub node accessible to somebody, you need to share the secret with 55 To make an encrypted pubsub node accessible to somebody, you need to share the secret with
65 them. 56 them.
66 57
67 You can see that as the key of a house: everybody who has a copy of the key can go inside 58 You can see that as the key of a house: everybody who has a copy of the key can go inside
90 To handle encrypted pubsub node shared secrets from command line, you may use 81 To handle encrypted pubsub node shared secrets from command line, you may use
91 :ref:`libervia-cli_pubsub_secret`. 82 :ref:`libervia-cli_pubsub_secret`.
92 83
93 .. _OpenPGP: https://en.wikipedia.org/wiki/Pretty_Good_Privacy#OpenPGP 84 .. _OpenPGP: https://en.wikipedia.org/wiki/Pretty_Good_Privacy#OpenPGP
94 85
86 .. _XEP-0473: OpenPGP for XMPP Pubsub: https://xmpp.org/extensions/xep-0473.html
87
88
95 Pubsub Targeted Encryption 89 Pubsub Targeted Encryption
96 ========================== 90 ==========================
97 91
98 It is also possible to encrypt a single pubsub item for a restricted set of users. This is 92 It is also possible to encrypt a single pubsub item for a restricted set of users. This is
99 different from the pubsub encryption explained above, as if you want to encrypt for a 93 different from the pubsub encryption explained above, as if you want to encrypt for a
118 By default, identity of the publisher of a pubsub item is difficult to authenticate: it 112 By default, identity of the publisher of a pubsub item is difficult to authenticate: it
119 may be specified by the pubsub service (using the `"publisher" attribute`_), but this 113 may be specified by the pubsub service (using the `"publisher" attribute`_), but this
120 attribute is not set by all pubsub services, and it can be spoofed by the service or the 114 attribute is not set by all pubsub services, and it can be spoofed by the service or the
121 XMPP server. 115 XMPP server.
122 116
123 To strongly authenticate the publisher of a pubsub item, it is possible to cryptographically sign an item. This can work with any pubsub item, encrypted or not, and it can be done after the item has been published. The process use `Pubsub Signing protoXEP`_ 117 To strongly authenticate the publisher of a pubsub item, it is possible to cryptographically sign an item. This can work with any pubsub item, encrypted or not, and it can be done after the item has been published. The process use `XEP-0476: Pubsub Signing: OpenPGP Profile`_.
124
125 .. note::
126
127 Pubsub Signing specification is not currently an official XEP (XMPP Extension
128 Protocol), it is about to be examinated by "XMPP council". This documentation will be
129 updated with the evolution of the situation.
130 118
131 .. attention:: 119 .. attention::
132 120
133 Signature only certifies that the signers strongly link themselves with this version of 121 Signature only certifies that the signers strongly link themselves with this version of
134 the item, not that the signers are the original authors of the item. In other words, it 122 the item, not that the signers are the original authors of the item. In other words, it
141 To handle pubsub signatures from command line, you may use 129 To handle pubsub signatures from command line, you may use
142 :ref:`libervia-cli_pubsub_signature`. 130 :ref:`libervia-cli_pubsub_signature`.
143 131
144 .. _"publisher" attribute: https://xmpp.org/extensions/xep-0060.html#publisher-publish-success-publisher 132 .. _"publisher" attribute: https://xmpp.org/extensions/xep-0060.html#publisher-publish-success-publisher
145 133
146 .. _Pubsub Signing protoXEP: https://github.com/xsf/xeps/pull/1228 134 .. _XEP-0476: Pubsub Signing: OpenPGP Profile: https://xmpp.org/extensions/xep-0476.html
135