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1052 lines
34 KiB
Markdown
1052 lines
34 KiB
Markdown
---
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title: "Appendices"
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weight: 70
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type: docs
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---
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## Unpadded Base64
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*Unpadded* Base64 refers to 'standard' Base64 encoding as defined in
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[RFC 4648](https://tools.ietf.org/html/rfc4648), without "=" padding.
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Specifically, where RFC 4648 requires that encoded data be padded to a
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multiple of four characters using `=` characters, unpadded Base64 omits
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this padding.
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For reference, RFC 4648 uses the following alphabet for Base 64:
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Value Encoding Value Encoding Value Encoding Value Encoding
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0 A 17 R 34 i 51 z
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1 B 18 S 35 j 52 0
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2 C 19 T 36 k 53 1
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3 D 20 U 37 l 54 2
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4 E 21 V 38 m 55 3
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5 F 22 W 39 n 56 4
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6 G 23 X 40 o 57 5
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7 H 24 Y 41 p 58 6
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8 I 25 Z 42 q 59 7
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9 J 26 a 43 r 60 8
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10 K 27 b 44 s 61 9
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11 L 28 c 45 t 62 +
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12 M 29 d 46 u 63 /
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13 N 30 e 47 v
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14 O 31 f 48 w
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15 P 32 g 49 x
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16 Q 33 h 50 y
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Examples of strings encoded using unpadded Base64:
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UNPADDED_BASE64("") = ""
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UNPADDED_BASE64("f") = "Zg"
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UNPADDED_BASE64("fo") = "Zm8"
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UNPADDED_BASE64("foo") = "Zm9v"
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UNPADDED_BASE64("foob") = "Zm9vYg"
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UNPADDED_BASE64("fooba") = "Zm9vYmE"
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UNPADDED_BASE64("foobar") = "Zm9vYmFy"
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When decoding Base64, implementations SHOULD accept input with or
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without padding characters wherever possible, to ensure maximum
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interoperability.
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## Signing JSON
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Various points in the Matrix specification require JSON objects to be
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cryptographically signed. This requires us to encode the JSON as a
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binary string. Unfortunately the same JSON can be encoded in different
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ways by changing how much white space is used or by changing the order
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of keys within objects.
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Signing an object therefore requires it to be encoded as a sequence of
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bytes using [Canonical JSON](#canonical-json), computing the signature
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for that sequence and then adding the signature to the original JSON
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object.
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### Canonical JSON
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We define the canonical JSON encoding for a value to be the shortest
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UTF-8 JSON encoding with dictionary keys lexicographically sorted by
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Unicode codepoint. Numbers in the JSON must be integers in the range
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`[-(2**53)+1, (2**53)-1]`.
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We pick UTF-8 as the encoding as it should be available to all platforms
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and JSON received from the network is likely to be already encoded using
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UTF-8. We sort the keys to give a consistent ordering. We force integers
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to be in the range where they can be accurately represented using IEEE
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double precision floating point numbers since a number of JSON libraries
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represent all numbers using this representation.
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{{% boxes/warning %}}
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Events in room versions 1, 2, 3, 4, and 5 might not be fully compliant
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with these restrictions. Servers SHOULD be capable of handling JSON
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which is considered invalid by these restrictions where possible.
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The most notable consideration is that integers might not be in the
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range specified above.
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{{% /boxes/warning %}}
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{{% boxes/note %}}
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Float values are not permitted by this encoding.
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{{% /boxes/note %}}
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```py
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import json
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def canonical_json(value):
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return json.dumps(
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value,
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# Encode code-points outside of ASCII as UTF-8 rather than \u escapes
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ensure_ascii=False,
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# Remove unnecessary white space.
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separators=(',',':'),
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# Sort the keys of dictionaries.
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sort_keys=True,
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# Encode the resulting Unicode as UTF-8 bytes.
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).encode("UTF-8")
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```
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#### Grammar
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Adapted from the grammar in <http://tools.ietf.org/html/rfc7159>
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removing insignificant whitespace, fractions, exponents and redundant
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character escapes.
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value = false / null / true / object / array / number / string
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false = %x66.61.6c.73.65
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null = %x6e.75.6c.6c
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true = %x74.72.75.65
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object = %x7B [ member *( %x2C member ) ] %7D
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member = string %x3A value
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array = %x5B [ value *( %x2C value ) ] %5B
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number = [ %x2D ] int
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int = %x30 / ( %x31-39 *digit )
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digit = %x30-39
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string = %x22 *char %x22
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char = unescaped / %x5C escaped
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unescaped = %x20-21 / %x23-5B / %x5D-10FFFF
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escaped = %x22 ; " quotation mark U+0022
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/ %x5C ; \ reverse solidus U+005C
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/ %x62 ; b backspace U+0008
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/ %x66 ; f form feed U+000C
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/ %x6E ; n line feed U+000A
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/ %x72 ; r carriage return U+000D
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/ %x74 ; t tab U+0009
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/ %x75.30.30.30 (%x30-37 / %x62 / %x65-66) ; u000X
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/ %x75.30.30.31 (%x30-39 / %x61-66) ; u001X
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#### Examples
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To assist in the development of compatible implementations, the
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following test values may be useful for verifying the canonical
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transformation code.
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Given the following JSON object:
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```json
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{}
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```
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The following canonical JSON should be produced:
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```json
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{}
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```
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Given the following JSON object:
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```json
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{
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"one": 1,
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"two": "Two"
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}
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```
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The following canonical JSON should be produced:
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```json
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{"one":1,"two":"Two"}
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```
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Given the following JSON object:
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```json
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{
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"b": "2",
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"a": "1"
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}
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```
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The following canonical JSON should be produced:
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```json
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{"a":"1","b":"2"}
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```
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Given the following JSON object:
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```json
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{"b":"2","a":"1"}
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```
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The following canonical JSON should be produced:
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```json
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{"a":"1","b":"2"}
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```
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Given the following JSON object:
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```json
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{
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"auth": {
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"success": true,
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"mxid": "@john.doe:example.com",
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"profile": {
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"display_name": "John Doe",
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"three_pids": [
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{
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"medium": "email",
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"address": "john.doe@example.org"
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},
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{
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"medium": "msisdn",
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"address": "123456789"
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}
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]
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}
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}
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}
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```
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The following canonical JSON should be produced:
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```json
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{"auth":{"mxid":"@john.doe:example.com","profile":{"display_name":"John Doe","three_pids":[{"address":"john.doe@example.org","medium":"email"},{"address":"123456789","medium":"msisdn"}]},"success":true}}
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```
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Given the following JSON object:
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```json
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{
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"a": "日本語"
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}
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```
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The following canonical JSON should be produced:
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```json
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{"a":"日本語"}
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```
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Given the following JSON object:
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```json
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{
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"本": 2,
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"日": 1
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}
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```
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The following canonical JSON should be produced:
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```json
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{"日":1,"本":2}
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```
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Given the following JSON object:
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```json
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{
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"a": "\u65E5"
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}
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```
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The following canonical JSON should be produced:
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```json
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{"a":"日"}
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```
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Given the following JSON object:
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```json
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{
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"a": null
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}
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```
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The following canonical JSON should be produced:
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```json
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{"a":null}
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```
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### Signing Details
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JSON is signed by encoding the JSON object without `signatures` or keys
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grouped as `unsigned`, using the canonical encoding described above. The
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JSON bytes are then signed using the signature algorithm and the
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signature is encoded using [unpadded Base64](#unpadded-base64). The resulting base64
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signature is added to an object under the *signing key identifier* which
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is added to the `signatures` object under the name of the entity signing
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it which is added back to the original JSON object along with the
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`unsigned` object.
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The *signing key identifier* is the concatenation of the *signing
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algorithm* and a *key identifier*. The *signing algorithm* identifies
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the algorithm used to sign the JSON. The currently supported value for
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*signing algorithm* is `ed25519` as implemented by NACL
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(<http://nacl.cr.yp.to/>). The *key identifier* is used to distinguish
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between different signing keys used by the same entity.
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The `unsigned` object and the `signatures` object are not covered by the
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signature. Therefore intermediate entities can add unsigned data such as
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timestamps and additional signatures.
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```json
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{
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"name": "example.org",
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"signing_keys": {
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"ed25519:1": "XSl0kuyvrXNj6A+7/tkrB9sxSbRi08Of5uRhxOqZtEQ"
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},
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"unsigned": {
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"age_ts": 922834800000
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},
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"signatures": {
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"example.org": {
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"ed25519:1": "s76RUgajp8w172am0zQb/iPTHsRnb4SkrzGoeCOSFfcBY2V/1c8QfrmdXHpvnc2jK5BD1WiJIxiMW95fMjK7Bw"
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}
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}
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}
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```
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```py
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def sign_json(json_object, signing_key, signing_name):
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signatures = json_object.pop("signatures", {})
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unsigned = json_object.pop("unsigned", None)
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signed = signing_key.sign(encode_canonical_json(json_object))
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signature_base64 = encode_base64(signed.signature)
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key_id = "%s:%s" % (signing_key.alg, signing_key.version)
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signatures.setdefault(signing_name, {})[key_id] = signature_base64
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json_object["signatures"] = signatures
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if unsigned is not None:
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json_object["unsigned"] = unsigned
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return json_object
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```
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### Checking for a Signature
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To check if an entity has signed a JSON object an implementation does
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the following:
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1. Checks if the `signatures` member of the object contains an entry
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with the name of the entity. If the entry is missing then the check
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fails.
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2. Removes any *signing key identifiers* from the entry with algorithms
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it doesn't understand. If there are no *signing key identifiers*
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left then the check fails.
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3. Looks up *verification keys* for the remaining *signing key
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identifiers* either from a local cache or by consulting a trusted
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key server. If it cannot find a *verification key* then the check
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fails.
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4. Decodes the base64 encoded signature bytes. If base64 decoding fails
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then the check fails.
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5. Removes the `signatures` and `unsigned` members of the object.
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6. Encodes the remainder of the JSON object using the [Canonical
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JSON](#canonical-json) encoding.
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7. Checks the signature bytes against the encoded object using the
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*verification key*. If this fails then the check fails. Otherwise
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the check succeeds.
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## Identifier Grammar
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Some identifiers are specific to given room versions, please refer to
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the [room versions specification](/#room-versions) for more
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information.
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### Server Name
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A homeserver is uniquely identified by its server name. This value is
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used in a number of identifiers, as described below.
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The server name represents the address at which the homeserver in
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question can be reached by other homeservers. All valid server names are
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included by the following grammar:
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server_name = hostname [ ":" port ]
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port = 1*5DIGIT
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hostname = IPv4address / "[" IPv6address "]" / dns-name
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IPv4address = 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT
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IPv6address = 2*45IPv6char
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IPv6char = DIGIT / %x41-46 / %x61-66 / ":" / "."
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; 0-9, A-F, a-f, :, .
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dns-name = 1*255dns-char
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dns-char = DIGIT / ALPHA / "-" / "."
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— in other words, the server name is the hostname, followed by an
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optional numeric port specifier. The hostname may be a dotted-quad IPv4
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address literal, an IPv6 address literal surrounded with square
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brackets, or a DNS name.
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IPv4 literals must be a sequence of four decimal numbers in the range 0
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to 255, separated by `.`. IPv6 literals must be as specified by
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[RFC3513, section 2.2](https://tools.ietf.org/html/rfc3513#section-2.2).
|
|
|
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DNS names for use with Matrix should follow the conventional
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|
restrictions for internet hostnames: they should consist of a series of
|
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labels separated by `.`, where each label consists of the alphanumeric
|
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characters or hyphens.
|
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|
|
Examples of valid server names are:
|
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|
|
- `matrix.org`
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- `matrix.org:8888`
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- `1.2.3.4` (IPv4 literal)
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- `1.2.3.4:1234` (IPv4 literal with explicit port)
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- `[1234:5678::abcd]` (IPv6 literal)
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- `[1234:5678::abcd]:5678` (IPv6 literal with explicit port)
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|
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{{% boxes/note %}}
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This grammar is based on the standard for internet host names, as
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specified by [RFC1123, section
|
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2.1](https://tools.ietf.org/html/rfc1123#page-13), with an extension for
|
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IPv6 literals.
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{{% /boxes/note %}}
|
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Server names must be treated case-sensitively: in other words,
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`@user:matrix.org` is a different person from `@user:MATRIX.ORG`.
|
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|
|
Some recommendations for a choice of server name follow:
|
|
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- The length of the complete server name should not exceed 230
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characters.
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- Server names should not use upper-case characters.
|
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|
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### Common Identifier Format
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|
|
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The Matrix protocol uses a common format to assign unique identifiers to
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a number of entities, including users, events and rooms. Each identifier
|
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takes the form:
|
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|
|
&string
|
|
|
|
where `&` represents a 'sigil' character; `string` is the string which
|
|
makes up the identifier.
|
|
|
|
The sigil characters are as follows:
|
|
|
|
- `@`: User ID
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|
- `!`: Room ID
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|
- `$`: Event ID
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|
- `+`: Group ID
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|
- `#`: Room alias
|
|
|
|
User IDs, group IDs, room IDs, room aliases, and sometimes event IDs
|
|
take the form:
|
|
|
|
&localpart:domain
|
|
|
|
where `domain` is the [server name](#server-name) of the homeserver
|
|
which allocated the identifier, and `localpart` is an identifier
|
|
allocated by that homeserver.
|
|
|
|
The precise grammar defining the allowable format of an identifier
|
|
depends on the type of identifier. For example, event IDs can sometimes
|
|
be represented with a `domain` component under some conditions - see the
|
|
[Event IDs](#room-ids-and-event-ids) section below for more information.
|
|
|
|
#### User Identifiers
|
|
|
|
Users within Matrix are uniquely identified by their Matrix user ID. The
|
|
user ID is namespaced to the homeserver which allocated the account and
|
|
has the form:
|
|
|
|
@localpart:domain
|
|
|
|
The `localpart` of a user ID is an opaque identifier for that user. It
|
|
MUST NOT be empty, and MUST contain only the characters `a-z`, `0-9`,
|
|
`.`, `_`, `=`, `-`, and `/`.
|
|
|
|
The `domain` of a user ID is the [server name](#server-name) of the
|
|
homeserver which allocated the account.
|
|
|
|
The length of a user ID, including the `@` sigil and the domain, MUST
|
|
NOT exceed 255 characters.
|
|
|
|
The complete grammar for a legal user ID is:
|
|
|
|
user_id = "@" user_id_localpart ":" server_name
|
|
user_id_localpart = 1*user_id_char
|
|
user_id_char = DIGIT
|
|
/ %x61-7A ; a-z
|
|
/ "-" / "." / "=" / "_" / "/"
|
|
|
|
{{% boxes/rationale %}}
|
|
A number of factors were considered when defining the allowable
|
|
characters for a user ID.
|
|
|
|
Firstly, we chose to exclude characters outside the basic US-ASCII
|
|
character set. User IDs are primarily intended for use as an identifier
|
|
at the protocol level, and their use as a human-readable handle is of
|
|
secondary benefit. Furthermore, they are useful as a last-resort
|
|
differentiator between users with similar display names. Allowing the
|
|
full Unicode character set would make very difficult for a human to
|
|
distinguish two similar user IDs. The limited character set used has the
|
|
advantage that even a user unfamiliar with the Latin alphabet should be
|
|
able to distinguish similar user IDs manually, if somewhat laboriously.
|
|
|
|
We chose to disallow upper-case characters because we do not consider it
|
|
valid to have two user IDs which differ only in case: indeed it should
|
|
be possible to reach `@user:matrix.org` as `@USER:matrix.org`. However,
|
|
user IDs are necessarily used in a number of situations which are
|
|
inherently case-sensitive (notably in the `state_key` of `m.room.member`
|
|
events). Forbidding upper-case characters (and requiring homeservers to
|
|
downcase usernames when creating user IDs for new users) is a relatively
|
|
simple way to ensure that `@USER:matrix.org` cannot refer to a different
|
|
user to `@user:matrix.org`.
|
|
|
|
Finally, we decided to restrict the allowable punctuation to a very
|
|
basic set to reduce the possibility of conflicts with special characters
|
|
in various situations. For example, "\*" is used as a wildcard in some
|
|
APIs (notably the filter API), so it cannot be a legal user ID
|
|
character.
|
|
|
|
The length restriction is derived from the limit on the length of the
|
|
`sender` key on events; since the user ID appears in every event sent by
|
|
the user, it is limited to ensure that the user ID does not dominate
|
|
over the actual content of the events.
|
|
{{% /boxes/rationale %}}
|
|
|
|
Matrix user IDs are sometimes informally referred to as MXIDs.
|
|
|
|
##### Historical User IDs
|
|
|
|
Older versions of this specification were more tolerant of the
|
|
characters permitted in user ID localparts. There are currently active
|
|
users whose user IDs do not conform to the permitted character set, and
|
|
a number of rooms whose history includes events with a `sender` which
|
|
does not conform. In order to handle these rooms successfully, clients
|
|
and servers MUST accept user IDs with localparts from the expanded
|
|
character set:
|
|
|
|
extended_user_id_char = %x21-39 / %x3B-7E ; all ASCII printing chars except :
|
|
|
|
##### Mapping from other character sets
|
|
|
|
In certain circumstances it will be desirable to map from a wider
|
|
character set onto the limited character set allowed in a user ID
|
|
localpart. Examples include a homeserver creating a user ID for a new
|
|
user based on the username passed to `/register`, or a bridge mapping
|
|
user ids from another protocol.
|
|
|
|
Implementations are free to do this mapping however they choose. Since
|
|
the user ID is opaque except to the implementation which created it, the
|
|
only requirement is that the implementation can perform the mapping
|
|
consistently. However, we suggest the following algorithm:
|
|
|
|
1. Encode character strings as UTF-8.
|
|
2. Convert the bytes `A-Z` to lower-case.
|
|
- In the case where a bridge must be able to distinguish two
|
|
different users with ids which differ only by case, escape
|
|
upper-case characters by prefixing with `_` before downcasing.
|
|
For example, `A` becomes `_a`. Escape a real `_` with a second
|
|
`_`.
|
|
3. Encode any remaining bytes outside the allowed character set, as
|
|
well as `=`, as their hexadecimal value, prefixed with `=`. For
|
|
example, `#` becomes `=23`; `á` becomes `=c3=a1`.
|
|
|
|
{{% boxes/rationale %}}
|
|
The suggested mapping is an attempt to preserve human-readability of
|
|
simple ASCII identifiers (unlike, for example, base-32), whilst still
|
|
allowing representation of *any* character (unlike punycode, which
|
|
provides no way to encode ASCII punctuation).
|
|
{{% /boxes/rationale %}}
|
|
|
|
#### Room IDs and Event IDs
|
|
|
|
A room has exactly one room ID. A room ID has the format:
|
|
|
|
!opaque_id:domain
|
|
|
|
An event has exactly one event ID. The format of an event ID depends
|
|
upon the [room version specification](/#room-versions).
|
|
|
|
The `domain` of a room ID is the [server name](#server-name) of the
|
|
homeserver which created the room/event. The domain is used only for
|
|
namespacing to avoid the risk of clashes of identifiers between
|
|
different homeservers. There is no implication that the room or event in
|
|
question is still available at the corresponding homeserver.
|
|
|
|
Event IDs and Room IDs are case-sensitive. They are not meant to be
|
|
human-readable. They are intended to be treated as fully opaque strings
|
|
by clients.
|
|
|
|
#### Group Identifiers
|
|
|
|
Groups within Matrix are uniquely identified by their group ID. The
|
|
group ID is namespaced to the group server which hosts this group and
|
|
has the form:
|
|
|
|
+localpart:domain
|
|
|
|
The `localpart` of a group ID is an opaque identifier for that group. It
|
|
MUST NOT be empty, and MUST contain only the characters `a-z`, `0-9`,
|
|
`.`, `_`, `=`, `-`, and `/`.
|
|
|
|
The `domain` of a group ID is the [server name](#server-name) of the
|
|
group server which hosts this group.
|
|
|
|
The length of a group ID, including the `+` sigil and the domain, MUST
|
|
NOT exceed 255 characters.
|
|
|
|
The complete grammar for a legal group ID is:
|
|
|
|
group_id = "+" group_id_localpart ":" server_name
|
|
group_id_localpart = 1*group_id_char
|
|
group_id_char = DIGIT
|
|
/ %x61-7A ; a-z
|
|
/ "-" / "." / "=" / "_" / "/"
|
|
|
|
#### Room Aliases
|
|
|
|
A room may have zero or more aliases. A room alias has the format:
|
|
|
|
#room_alias:domain
|
|
|
|
The `domain` of a room alias is the [server name](#server-name) of the
|
|
homeserver which created the alias. Other servers may contact this
|
|
homeserver to look up the alias.
|
|
|
|
Room aliases MUST NOT exceed 255 bytes (including the `#` sigil and the
|
|
domain).
|
|
|
|
#### matrix.to navigation
|
|
|
|
{{% boxes/note %}}
|
|
This namespacing is in place pending a `matrix://` (or similar) URI
|
|
scheme. This is **not** meant to be interpreted as an available web
|
|
service - see below for more details.
|
|
{{% /boxes/note %}}
|
|
|
|
Rooms, users, aliases, and groups may be represented as a "matrix.to"
|
|
URI. This URI can be used to reference particular objects in a given
|
|
context, such as mentioning a user in a message or linking someone to a
|
|
particular point in the room's history (a permalink).
|
|
|
|
A matrix.to URI has the following format, based upon the specification
|
|
defined in RFC 3986:
|
|
|
|
> <https://matrix.to/#/><identifier>/<extra
|
|
> parameter>?<additional arguments>
|
|
|
|
The identifier may be a room ID, room alias, user ID, or group ID. The
|
|
extra parameter is only used in the case of permalinks where an event ID
|
|
is referenced. The matrix.to URI, when referenced, must always start
|
|
with `https://matrix.to/#/` followed by the identifier.
|
|
|
|
The `<additional arguments>` and the preceding question mark are
|
|
optional and only apply in certain circumstances, documented below.
|
|
|
|
Clients should not rely on matrix.to URIs falling back to a web server
|
|
if accessed and instead should perform some sort of action within the
|
|
client. For example, if the user were to click on a matrix.to URI for a
|
|
room alias, the client may open a view for the user to participate in
|
|
the room.
|
|
|
|
The components of the matrix.to URI (`<identifier>` and
|
|
`<extra parameter>`) are to be percent-encoded as per RFC 3986.
|
|
|
|
Examples of matrix.to URIs are:
|
|
|
|
- Room alias: `https://matrix.to/#/%23somewhere%3Aexample.org`
|
|
- Room: `https://matrix.to/#/!somewhere%3Aexample.org`
|
|
- Permalink by room:
|
|
`https://matrix.to/#/!somewhere%3Aexample.org/%24event%3Aexample.org`
|
|
- Permalink by room alias:
|
|
`https://matrix.to/#/%23somewhere:example.org/%24event%3Aexample.org`
|
|
- User: `https://matrix.to/#/%40alice%3Aexample.org`
|
|
- Group: `https://matrix.to/#/%2Bexample%3Aexample.org`
|
|
|
|
{{% boxes/note %}}
|
|
Historically, clients have not produced URIs which are fully encoded.
|
|
Clients should try to interpret these cases to the best of their
|
|
ability. For example, an unencoded room alias should still work within
|
|
the client if possible.
|
|
{{% /boxes/note %}}
|
|
|
|
{{% boxes/note %}}
|
|
Clients should be aware that decoding a matrix.to URI may result in
|
|
extra slashes appearing due to some [room
|
|
versions](/#room-versions). These slashes should normally be
|
|
encoded when producing matrix.to URIs, however.
|
|
{{% /boxes/note %}}
|
|
|
|
##### Routing
|
|
|
|
Room IDs are not routable on their own as there is no reliable domain to
|
|
send requests to. This is partially mitigated with the addition of a
|
|
`via` argument on a matrix.to URI, however the problem of routability is
|
|
still present. Clients should do their best to route Room IDs to where
|
|
they need to go, however they should also be aware of [issue
|
|
\#1579](https://github.com/matrix-org/matrix-doc/issues/1579).
|
|
|
|
A room (or room permalink) which isn't using a room alias should supply
|
|
at least one server using `via` in the `<additional arguments>`, like
|
|
so:
|
|
`https://matrix.to/!somewhere%3Aexample.org?via=example.org&via=alt.example.org`.
|
|
The parameter can be supplied multiple times to specify multiple servers
|
|
to try.
|
|
|
|
The values of `via` are intended to be passed along as the `server_name`
|
|
parameters on the Client Server `/join` API.
|
|
|
|
When generating room links and permalinks, the application should pick
|
|
servers which have a high probability of being in the room in the
|
|
distant future. How these servers are picked is left as an
|
|
implementation detail, however the current recommendation is to pick 3
|
|
unique servers based on the following criteria:
|
|
|
|
- The first server should be the server of the highest power level
|
|
user in the room, provided they are at least power level 50. If no
|
|
user meets this criterion, pick the most popular server in the room
|
|
(most joined users). The rationale for not picking users with power
|
|
levels under 50 is that they are unlikely to be around into the
|
|
distant future while higher ranking users (and therefore servers)
|
|
are less likely to give up their power and move somewhere else. Most
|
|
rooms in the public federation have a power level 100 user and have
|
|
not deviated from the default structure where power level 50 users
|
|
have moderator-style privileges.
|
|
- The second server should be the next highest server by population,
|
|
or the first highest by population if the first server was based on
|
|
a user's power level. The rationale for picking popular servers is
|
|
that the server is unlikely to be removed as the room naturally
|
|
grows in membership due to that server joining users. The server
|
|
could be refused participation in the future due to server ACLs or
|
|
similar, however the chance of that happening to a server which is
|
|
organically joining the room is unlikely.
|
|
- The third server should be the next highest server by population.
|
|
- Servers which are blocked due to server ACLs should never be chosen.
|
|
- Servers which are IP addresses should never be chosen. Servers which
|
|
use a domain name are less likely to be unroutable in the future
|
|
whereas IP addresses cannot be pointed to a different location and
|
|
therefore higher risk options.
|
|
- All 3 servers should be unique from each other. If the room does not
|
|
have enough users to supply 3 servers, the application should only
|
|
specify the servers it can. For example, a room with only 2 users in
|
|
it would result in maximum 2 `via` parameters.
|
|
|
|
## 3PID Types
|
|
|
|
Third Party Identifiers (3PIDs) represent identifiers on other
|
|
namespaces that might be associated with a particular person. They
|
|
comprise a tuple of `medium` which is a string that identifies the
|
|
namespace in which the identifier exists, and an `address`: a string
|
|
representing the identifier in that namespace. This must be a canonical
|
|
form of the identifier, *i.e.* if multiple strings could represent the
|
|
same identifier, only one of these strings must be used in a 3PID
|
|
address, in a well-defined manner.
|
|
|
|
For example, for e-mail, the `medium` is 'email' and the `address` would
|
|
be the email address, *e.g.* the string `bob@example.com`. Since domain
|
|
resolution is case-insensitive, the email address `bob@Example.com` is
|
|
also has the 3PID address of `bob@example.com` (without the capital 'e')
|
|
rather than `bob@Example.com`.
|
|
|
|
The namespaces defined by this specification are listed below. More
|
|
namespaces may be defined in future versions of this specification.
|
|
|
|
### E-Mail
|
|
|
|
Medium: `email`
|
|
|
|
Represents E-Mail addresses. The `address` is the raw email address in
|
|
`user@domain` form with the domain in lowercase. It must not contain
|
|
other text such as real name, angle brackets or a mailto: prefix.
|
|
|
|
### PSTN Phone numbers
|
|
|
|
Medium: `msisdn`
|
|
|
|
Represents telephone numbers on the public switched telephone network.
|
|
The `address` is the telephone number represented as a MSISDN (Mobile
|
|
Station International Subscriber Directory Number) as defined by the
|
|
E.164 numbering plan. Note that MSISDNs do not include a leading '+'.
|
|
|
|
## Security Threat Model
|
|
|
|
### Denial of Service
|
|
|
|
The attacker could attempt to prevent delivery of messages to or from
|
|
the victim in order to:
|
|
|
|
- Disrupt service or marketing campaign of a commercial competitor.
|
|
- Censor a discussion or censor a participant in a discussion.
|
|
- Perform general vandalism.
|
|
|
|
#### Threat: Resource Exhaustion
|
|
|
|
An attacker could cause the victim's server to exhaust a particular
|
|
resource (e.g. open TCP connections, CPU, memory, disk storage)
|
|
|
|
#### Threat: Unrecoverable Consistency Violations
|
|
|
|
An attacker could send messages which created an unrecoverable
|
|
"split-brain" state in the cluster such that the victim's servers could
|
|
no longer derive a consistent view of the chatroom state.
|
|
|
|
#### Threat: Bad History
|
|
|
|
An attacker could convince the victim to accept invalid messages which
|
|
the victim would then include in their view of the chatroom history.
|
|
Other servers in the chatroom would reject the invalid messages and
|
|
potentially reject the victims messages as well since they depended on
|
|
the invalid messages.
|
|
|
|
#### Threat: Block Network Traffic
|
|
|
|
An attacker could try to firewall traffic between the victim's server
|
|
and some or all of the other servers in the chatroom.
|
|
|
|
#### Threat: High Volume of Messages
|
|
|
|
An attacker could send large volumes of messages to a chatroom with the
|
|
victim making the chatroom unusable.
|
|
|
|
#### Threat: Banning users without necessary authorisation
|
|
|
|
An attacker could attempt to ban a user from a chatroom without the
|
|
necessary authorisation.
|
|
|
|
### Spoofing
|
|
|
|
An attacker could try to send a message claiming to be from the victim
|
|
without the victim having sent the message in order to:
|
|
|
|
- Impersonate the victim while performing illicit activity.
|
|
- Obtain privileges of the victim.
|
|
|
|
#### Threat: Altering Message Contents
|
|
|
|
An attacker could try to alter the contents of an existing message from
|
|
the victim.
|
|
|
|
#### Threat: Fake Message "origin" Field
|
|
|
|
An attacker could try to send a new message purporting to be from the
|
|
victim with a phony "origin" field.
|
|
|
|
### Spamming
|
|
|
|
The attacker could try to send a high volume of solicited or unsolicited
|
|
messages to the victim in order to:
|
|
|
|
- Find victims for scams.
|
|
- Market unwanted products.
|
|
|
|
#### Threat: Unsolicited Messages
|
|
|
|
An attacker could try to send messages to victims who do not wish to
|
|
receive them.
|
|
|
|
#### Threat: Abusive Messages
|
|
|
|
An attacker could send abusive or threatening messages to the victim
|
|
|
|
### Spying
|
|
|
|
The attacker could try to access message contents or metadata for
|
|
messages sent by the victim or to the victim that were not intended to
|
|
reach the attacker in order to:
|
|
|
|
- Gain sensitive personal or commercial information.
|
|
- Impersonate the victim using credentials contained in the messages.
|
|
(e.g. password reset messages)
|
|
- Discover who the victim was talking to and when.
|
|
|
|
#### Threat: Disclosure during Transmission
|
|
|
|
An attacker could try to expose the message contents or metadata during
|
|
transmission between the servers.
|
|
|
|
#### Threat: Disclosure to Servers Outside Chatroom
|
|
|
|
An attacker could try to convince servers within a chatroom to send
|
|
messages to a server it controls that was not authorised to be within
|
|
the chatroom.
|
|
|
|
#### Threat: Disclosure to Servers Within Chatroom
|
|
|
|
An attacker could take control of a server within a chatroom to expose
|
|
message contents or metadata for messages in that room.
|
|
|
|
## Cryptographic Test Vectors
|
|
|
|
To assist in the development of compatible implementations, the
|
|
following test values may be useful for verifying the cryptographic
|
|
event signing code.
|
|
|
|
### Signing Key
|
|
|
|
The following test vectors all use the 32-byte value given by the
|
|
following Base64-encoded string as the seed for generating the `ed25519`
|
|
signing key:
|
|
|
|
SIGNING_KEY_SEED = decode_base64(
|
|
"YJDBA9Xnr2sVqXD9Vj7XVUnmFZcZrlw8Md7kMW+3XA1"
|
|
)
|
|
|
|
In each case, the server name and key ID are as follows:
|
|
|
|
SERVER_NAME = "domain"
|
|
|
|
KEY_ID = "ed25519:1"
|
|
|
|
### JSON Signing
|
|
|
|
Given an empty JSON object:
|
|
|
|
```json
|
|
{}
|
|
```
|
|
|
|
The JSON signing algorithm should emit the following signed data:
|
|
|
|
```json
|
|
{
|
|
"signatures": {
|
|
"domain": {
|
|
"ed25519:1": "K8280/U9SSy9IVtjBuVeLr+HpOB4BQFWbg+UZaADMtTdGYI7Geitb76LTrr5QV/7Xg4ahLwYGYZzuHGZKM5ZAQ"
|
|
}
|
|
}
|
|
}
|
|
```
|
|
|
|
Given the following JSON object with data values in it:
|
|
|
|
```json
|
|
{
|
|
"one": 1,
|
|
"two": "Two"
|
|
}
|
|
```
|
|
|
|
The JSON signing algorithm should emit the following signed JSON:
|
|
|
|
```json
|
|
{
|
|
"one": 1,
|
|
"signatures": {
|
|
"domain": {
|
|
"ed25519:1": "KqmLSbO39/Bzb0QIYE82zqLwsA+PDzYIpIRA2sRQ4sL53+sN6/fpNSoqE7BP7vBZhG6kYdD13EIMJpvhJI+6Bw"
|
|
}
|
|
},
|
|
"two": "Two"
|
|
}
|
|
```
|
|
|
|
### Event Signing
|
|
|
|
Given the following minimally-sized event:
|
|
|
|
```json
|
|
{
|
|
"room_id": "!x:domain",
|
|
"sender": "@a:domain",
|
|
"origin": "domain",
|
|
"origin_server_ts": 1000000,
|
|
"signatures": {},
|
|
"hashes": {},
|
|
"type": "X",
|
|
"content": {},
|
|
"prev_events": [],
|
|
"auth_events": [],
|
|
"depth": 3,
|
|
"unsigned": {
|
|
"age_ts": 1000000
|
|
}
|
|
}
|
|
```
|
|
|
|
The event signing algorithm should emit the following signed event:
|
|
|
|
```json
|
|
{
|
|
"auth_events": [],
|
|
"content": {},
|
|
"depth": 3,
|
|
"hashes": {
|
|
"sha256": "5jM4wQpv6lnBo7CLIghJuHdW+s2CMBJPUOGOC89ncos"
|
|
},
|
|
"origin": "domain",
|
|
"origin_server_ts": 1000000,
|
|
"prev_events": [],
|
|
"room_id": "!x:domain",
|
|
"sender": "@a:domain",
|
|
"signatures": {
|
|
"domain": {
|
|
"ed25519:1": "KxwGjPSDEtvnFgU00fwFz+l6d2pJM6XBIaMEn81SXPTRl16AqLAYqfIReFGZlHi5KLjAWbOoMszkwsQma+lYAg"
|
|
}
|
|
},
|
|
"type": "X",
|
|
"unsigned": {
|
|
"age_ts": 1000000
|
|
}
|
|
}
|
|
```
|
|
|
|
Given the following event containing redactable content:
|
|
|
|
```json
|
|
{
|
|
"content": {
|
|
"body": "Here is the message content"
|
|
},
|
|
"event_id": "$0:domain",
|
|
"origin": "domain",
|
|
"origin_server_ts": 1000000,
|
|
"type": "m.room.message",
|
|
"room_id": "!r:domain",
|
|
"sender": "@u:domain",
|
|
"signatures": {},
|
|
"unsigned": {
|
|
"age_ts": 1000000
|
|
}
|
|
}
|
|
```
|
|
|
|
The event signing algorithm should emit the following signed event:
|
|
|
|
```json
|
|
{
|
|
"content": {
|
|
"body": "Here is the message content"
|
|
},
|
|
"event_id": "$0:domain",
|
|
"hashes": {
|
|
"sha256": "onLKD1bGljeBWQhWZ1kaP9SorVmRQNdN5aM2JYU2n/g"
|
|
},
|
|
"origin": "domain",
|
|
"origin_server_ts": 1000000,
|
|
"type": "m.room.message",
|
|
"room_id": "!r:domain",
|
|
"sender": "@u:domain",
|
|
"signatures": {
|
|
"domain": {
|
|
"ed25519:1": "Wm+VzmOUOz08Ds+0NTWb1d4CZrVsJSikkeRxh6aCcUwu6pNC78FunoD7KNWzqFn241eYHYMGCA5McEiVPdhzBA"
|
|
}
|
|
},
|
|
"unsigned": {
|
|
"age_ts": 1000000
|
|
}
|
|
}
|
|
```
|