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Dominic / ssb-private-groups



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Dominic Tarr committed on 12/27/2018, 9:19:59 AM

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LICENSEadded
README.mdadded
index.jsadded
package.jsonadded
LICENSEView
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1 …+Copyright (c) 2018 Dominic Tarr
2 …+
3 …+Permission is hereby granted, free of charge,
4 …+to any person obtaining a copy of this software and
5 …+associated documentation files (the "Software"), to
6 …+deal in the Software without restriction, including
7 …+without limitation the rights to use, copy, modify,
8 …+merge, publish, distribute, sublicense, and/or sell
9 …+copies of the Software, and to permit persons to whom
10 …+the Software is furnished to do so,
11 …+subject to the following conditions:
12 …+
13 …+The above copyright notice and this permission notice
14 …+shall be included in all copies or substantial portions of the Software.
15 …+
16 …+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
17 …+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
18 …+OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
19 …+IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR
20 …+ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
21 …+TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
22 …+SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
README.mdView
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1 …+# ssb-private-groups
2 …+
3 …+
4 …+## receive key
5 …+
6 …+to indicate you support box2, post a message
7 …+
8 …+```
9 …+{
10 …+ type: 'private-msg-key',
11 …+ key: curve25519.public
12 …+}
13 …+``
14 …+when decrypting messages from another feed,
15 …+you know it came from their most recent
16 …+private message key, because they are in a strict order.
17 …+
18 …+when decrypting messages _for your feed_ these must
19 …+be combined with each private-msg-key you retain.
20 …+when rotating keys, it is advisable to keep both keys
21 …+alive for an overlap period, to improve chances that
22 …+sender has your new key when they write a message to you.
23 …+
24 …+If they write a message to a key you have discarded,
25 …+you won't know, because you'll be unable to decrypt that message.
26 …+
27 …+
28 …+
29 …+## License
30 …+
31 …+MIT
index.jsView
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1 …+function isBox2(ctxt) {
2 …+ //we can just do a fairly lax check here, don't check the content
3 …+ //is canonical base64, because that check has already been done.
4 …+ return 'string' == typeof ctxt && /\.box2$/.test(ctxt)
5 …+}
6 …+
7 …+function ctxtToBuffer(ctxt) {
8 …+ return isBox2(ctxt) && Buffer.from(ctxt.substring(ctxt.indexOf('.')), 'base64')
9 …+}
10 …+
11 …+function idToBuffer (id) {
12 …+ return Buffer.from(id.substring(1, id.indexOf('.')), 'base64')
13 …+}
14 …+
15 …+//by deriving the message key from the group id (the founding
16 …+//message id) and the unbox key for that message, this ensures
17 …+//someone can't decrypt the message without knowing the founding
18 …+//message, therefore avoiding surruptious sharing the group.
19 …+//they can't _not_ know who made the group, so if someone else
20 …+//shares it to them, they know they are being sneaky.
21 …+
22 …+//and, you can verify this property from the design! you can't
23 …+//rewrite this code so they don't know the founding message
24 …+//and still be able to decrypt these messages.
25 …+
26 …+function getGroupMsgKey(previous, group) {
27 …+ return hmac(Buffer.concat([previous, group.id]), group.unbox)
28 …+}
29 …+
30 …+exports.init = function () {
31 …+
32 …+ var af = AtomicFile(
33 …+ path.join(config.path, 'private-groups/local-keys.json')
34 …+ )
35 …+ var ready = false, waiting = []
36 …+ af.get(function (err, data) {
37 …+ keyState = data || {msgKeys: [], groupKeys: []}
38 …+ ready = true
39 …+ while(waiting.length) waiting.shift()()
40 …+ })
41 …+
42 …+ //state:
43 …+ /*
44 …+ {
45 …+ <author>: {
46 …+ key: <author's latest privacy key>
47 …+ }
48 …+ }
49 …+ */
50 …+
51 …+ var keyState = null
52 …+ var state = null
53 …+ //cache: {<author>: [scalar_mult(msg_keys[i], <author's latest privacy key>)]
54 …+ var cache = {}
55 …+
56 …+
57 …+ sbot._flumeUse('private-groups/remote-keys', Reduce(1, function (acc, msg) {
58 …+ state = acc = acc || {}
59 …+ if(msg.content.type === 'private-msg-key') {
60 …+ acc[msg.author] = [{sequence: msg.sequence, key: msg.content.key}]
61 …+ cache[msg.author] = null
62 …+ }
63 …+ })
64 …+
65 …+ //sbot._flumeUse('private-groups/old-remote-keys', Level(1, function (data) {
66 …+ // if(msg.content.type === 'private-msg-key') {
67 …+ // return [msg.author, msg.sequence, msg.content.type]
68 …+ // }
69 …+ //})
70 …+
71 …+ sbot.addMap(function (data, cb) {
72 …+ if(!isBox2(data.value.content)) return cb(null, data)
73 …+ //the views and keyState have not been loaded
74 …+ //delay processing any box2 messages until they are.
75 …+ if(ready) cb(null, data)
76 …+ else waiting.push(function () {
77 …+ cb(null, data)
78 …+ })
79 …+ })
80 …+
81 …+ sbot.addUnboxer({
82 …+ key:
83 …+ function (content, value) {
84 …+ if(!isBox2(content)) return
85 …+ var a_state = state[value.author]
86 …+ if(!a_state) return
87 …+
88 …+ var keys_to_try = cache[value.author]
89 …+ if(!keys_to_try) {
90 …+ keys_to_try = cache[value.author] = keyState.msgKeys.map(function (key) {
91 …+ return scalarmult(a_state.key, curve.private)
92 …+ })
93 …+
94 …+ var ctxt = ctxtToBuffer(content), nonce = idToBuffer(value.previous)
95 …+ var key = groupbox.unboxKey( //direct recipients
96 …+ ctxt, nonce, keys_to_try, 8
97 …+ )
98 …+ if(key) return key
99 …+
100 …+ var group_keys = []
101 …+ for(var id in keyState.groupKeys)
102 …+ group_keys.push(getGroupMsgKey(nonce, keyState.groupKeys[id])
103 …+ //note: if we only allow groups in the first 4 slots
104 …+ //that means better sort them before any individuals
105 …+ key = groupbox.unboxKey( //groups we are in
106 …+ ctxt, nonce, group_keys, 4
107 …+ )
108 …+ if(key) return key
109 …+ },
110 …+ value: function (content, key) {
111 …+ if(!isBox2(content)) return
112 …+ return groupbox.unboxBody(content, key)
113 …+ }
114 …+ })
115 …+
116 …+ return {
117 …+// addGroupKey: function (group, cb) {
118 …+// af.get(function () {
119 …+// keyState.groupKeys[hmac(group.id, group.unbox)] = group)
120 …+// af.set(keys, cb)
121 …+// })
122 …+// },
123 …+ addCurvePair: function (curve_keys, cb) {
124 …+ if(!isCurvePair(curve_keys)) return cb(new Error('expected a pair of curve25519 keys')
125 …+ keyState.msgKeys.push(curve_keys)
126 …+ cache = {} //clear cache, so it's regenerated up to date.
127 …+ //NOTE: identiy adding this key must publish
128 …+ // a message advertising this receive key, or no one
129 …+ // will send them messages!
130 …+ af.set(msg_keys, cb)
131 …+ },
132 …+//forgetting old keys. crude basis for forward secrecy.
133 …+//you will no longer be able to decrypt messages sent to curve_pk
134 …+ forget: function (curve_pk, cb) {
135 …+ af.get(function () {
136 …+ for(var i = msg_keys.length-1; i >= 0; i--)
137 …+ if(curve_pk == msg_keys[i].public)
138 …+ msg_keys.splice(i, 1)
139 …+ cache = {} //clear cache, will be regenerated.
140 …+ af.set(msg_keys, cb)
141 …+ })
142 …+ }
143 …+ }
144 …+}
145 …+
146 …+
147 …+
148 …+
149 …+
150 …+
151 …+
package.jsonView
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1 …+{
2 …+ "name": "ssb-private-groups",
3 …+ "description": "",
4 …+ "version": "1.0.0",
5 …+ "homepage": "https://github.com/dominictarr/ssb-private-groups",
6 …+ "repository": {
7 …+ "type": "git",
8 …+ "url": "git://github.com/dominictarr/ssb-private-groups.git"
9 …+ },
10 …+ "dependencies": {
11 …+ },
12 …+ "devDependencies": {
13 …+ },
14 …+ "scripts": {
15 …+ "test": "set -e; for t in test/*.js; do node $t; done"
16 …+ },
17 …+ "author": "Dominic Tarr <dominic.tarr@gmail.com> (http://dominictarr.com)",
18 …+ "license": "MIT"
19 …+}

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