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Initialization vector of encrypted files is sent as padded base64 #4172

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tulir opened this issue Mar 31, 2021 · 0 comments · Fixed by matrix-org/matrix-ios-sdk#1059
Closed

Initialization vector of encrypted files is sent as padded base64 #4172

tulir opened this issue Mar 31, 2021 · 0 comments · Fixed by matrix-org/matrix-ios-sdk#1059

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@tulir
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tulir commented Mar 31, 2021

Describe the bug
The iv value in encrypted files is sent as normal base64 instead of unpadded base64. This breaks other clients which require iv to follow the spec precisely.

To Reproduce

  1. Send an image with Element iOS in an encrypted room.
  2. View the (decrypted) event source, find the iv field and see unexpected == at the end:
    image

Expected behavior
iv is sent as unpadded base64 as specified in the spec:

The 128-bit unique counter block used by AES-CTR, encoded as unpadded base64.

Smartphone (please complete the following information):

  • Device: 8+
  • OS: 14.4.2
  • Version: 1.2.7
Johennes added a commit to Johennes/matrix-ios-sdk that referenced this issue Apr 1, 2021
@Johennes
Remove padding from base64 encoded iv value
3c7cb0b 
This uses the existing `MXBase64Tools` to trim the `=` padding from the base64
encoded string. The reinsertion of the padding prior to decoding was already
implemented (line 224 in the same file).

Closes: element-hq/element-ios#4172

Signed-off-by: Johannes Marbach <n0-0ne+github@mailbox.org>
@Johennes Johennes mentioned this issue Apr 1, 2021
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Remove padding from base64 encoded iv value Johennes/matrix-ios-sdk
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@tulir