redacted e2e message says "Unable to decrypt: Unknown encryption algorithm "undefined"."

[uhoreg]

From the #megolm room:

It should just not try to decrypt the message if it has been redacted.

FWIW, view source on that message says:

{
  "origin_server_ts": 1493156450619,
  "sender": "@aaron:raim.ist",
  "event_id": "$14931564505asBdk:raim.ist",
  "age": 71191306,
  "unsigned": {
    "age": 71191306,
    "redacted_by": "$14931577096KrKPI:raim.ist",
    "redacted_because": {
      "origin_server_ts": 1493157709838,
      "sender": "@aaron:raim.ist",
      "event_id": "$14931577096KrKPI:raim.ist",
      "age": 69932087,
      "unsigned": {
        "age": 69932087
      },
      "content": {},
      "redacts": "$14931564505asBdk:raim.ist",
      "room_id": "!UCnwUWwIKhcpaPTHtR:sw1v.org",
      "user_id": "@aaron:raim.ist",
      "type": "m.room.redaction"
    }
  },
  "content": {},
  "room_id": "!UCnwUWwIKhcpaPTHtR:sw1v.org",
  "user_id": "@aaron:raim.ist",
  "type": "m.room.encrypted",
  "redacted_because": {
    "origin_server_ts": 1493157709838,
    "sender": "@aaron:raim.ist",
    "event_id": "$14931577096KrKPI:raim.ist",
    "age": 69932087,
    "unsigned": {
      "age": 69932087
    },
    "content": {},
    "redacts": "$14931564505asBdk:raim.ist",
    "room_id": "!UCnwUWwIKhcpaPTHtR:sw1v.org",
    "user_id": "@aaron:raim.ist",
    "type": "m.room.redaction"
  }
}

[ara4n]

this is really really ugly.

[uhoreg]

Fixed by matrix-org/matrix-js-sdk#554

[michel-zimmer]

This exact issue is happening again for me as far as I can tell:

Decrypted event source:

{
  "type": "m.room.message",
  "content": {
    "msgtype": "m.bad.encrypted",
    "body": "** Unable to decrypt: Unknown encryption algorithm \"undefined\". **"
  }
}

Original event source:

{
  "content": {},
  "origin_server_ts": 1593761398124,
  "room_id": "!…:matrix.org",
  "sender": "@michel-zimmer:matrix.org",
  "type": "m.room.encrypted",
  "unsigned": {
    "redacted_by": "$6M1oJkRMLfn3k1ALmnLbbWq2vemoO6cCLomowO4BkbM",
    "redacted_because": {
      "content": {},
      "origin_server_ts": 1593764558519,
      "redacts": "$VmprAKEQ9RA_NloLleUbkCKPpf8FWVf5yly2gD_mW58",
      "room_id": "!…:matrix.org",
      "sender": "@michel-zimmer:matrix.org",
      "type": "m.room.redaction",
      "unsigned": {
        "age": 22680076733
      },
      "event_id": "$6M1oJkRMLfn3k1ALmnLbbWq2vemoO6cCLomowO4BkbM",
      "user_id": "@michel-zimmer:matrix.org",
      "age": 22680076733
    },
    "age": 22683237128
  },
  "event_id": "$VmprAKEQ9RA_NloLleUbkCKPpf8FWVf5yly2gD_mW58",
  "user_id": "@michel-zimmer:matrix.org",
  "age": 22683237128,
  "redacted_because": {
    "content": {},
    "origin_server_ts": 1593764558519,
    "redacts": "$VmprAKEQ9RA_NloLleUbkCKPpf8FWVf5yly2gD_mW58",
    "room_id": "!…:matrix.org",
    "sender": "@michel-zimmer:matrix.org",
    "type": "m.room.redaction",
    "unsigned": {
      "age": 22680076733
    },
    "event_id": "$6M1oJkRMLfn3k1ALmnLbbWq2vemoO6cCLomowO4BkbM",
    "user_id": "@michel-zimmer:matrix.org",
    "age": 22680076733
  }
}

Is there anything I can do?

[SimonBrandner]

@michel-zimmer, it might be better to open a new issue in this case