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make hash commitment always include the m.relates_to

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Hubert Chathi 2019-11-18 16:24:59 -05:00
parent a514485bcb
commit 1590ae224c
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79
proposals/2241-e2e-verification-in-dms.md
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@ -159,6 +159,85 @@ The messages used in SAS verification are the same as those currently defined,
except that instead of the `transaction_id` property, an `m.relates_to`
property, as defined above, is used instead.
If the key verification messages are encrypted, the hash commitment sent in the
`m.key.verification.accept` message MUST be based on the decrypted
`m.key.verification.start` message contents, and include the `m.relates_to`
field, even if the decrypted message contents do not include that field. For
example, if Alice sends a message to start the SAS verification:
```json
{
"content": {
"algorithm": "m.megolm.v1.aes-sha2",
"ciphertext": "ABCDEFG...",
"device_id": "Dynabook",
"sender_key": "alice+sender+key",
"session_id": "session+id",
"m.relates_to": {
"rel_type": "m.reference",
"event_id": "$verification_request_event"
}
},
"event_id": "$event_id",
"origin_server_ts": 1234567890,
"sender": "@alice:example.org",
"type": "m.room.encrypted",
"room_id": "!room_id:example.org"
}
```
which, when decrypted, yields:
```json
{
"room_id": "!room_id:example.org",
"type": "m.key.verification.start",
"content": {
"from_device": "Dynabook",
"hashes": [
"sha256"
],
"key_agreement_protocols": [
"curve25519"
],
"message_authentication_codes": [
"hkdf-hmac-sha256"
],
"method": "m.sas.v1",
"short_authentication_string": [
"decimal",
"emoji"
]
}
}
```
then the hash commitment will be based on the message contents:
```json
{
"from_device": "Dynabook",
"hashes": [
"sha256"
],
"key_agreement_protocols": [
"curve25519"
],
"message_authentication_codes": [
"hkdf-hmac-sha256"
],
"method": "m.sas.v1",
"short_authentication_string": [
"decimal",
"emoji"
],
"m.relates_to": {
"rel_type": "m.reference",
"event_id": "$verification_request_event"
}
}
```
## Alternatives
Messages sent by the verification methods, after the initial key verification