Add support for new dehydrated device format #199

uhoreg · 2024-11-27T23:44:50Z

as documented in the current version of MSC3814

Fixes #196

poljar · 2024-12-05T11:59:18Z

Gonna close and reopen this to see if the codecov thing kicks in.

codecov-commenter · 2024-12-05T12:02:38Z

Codecov Report

Attention: Patch coverage is 89.65517% with 9 lines in your changes missing coverage. Please review.

Project coverage is 90.24%. Comparing base (5eb25a6) to head (e22dfcb).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/lib.rs	33.33%	6 Missing ⚠️
src/olm/account/mod.rs	97.01%	2 Missing ⚠️
src/types/ed25519.rs	87.50%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #199      +/-   ##
==========================================
- Coverage   90.28%   90.24%   -0.05%     
==========================================
  Files          34       34              
  Lines        1905     1989      +84     
==========================================
+ Hits         1720     1795      +75     
- Misses        185      194       +9

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so that if new keys get generated, the existing keys don't get overwritten

uhoreg · 2024-12-17T23:29:47Z

@poljar can I get a review on this PR? Thanks

poljar

Hi, sorry for the late reply, we miscommunicated on who would do the first review.

A good start but needs a bit more polish.

poljar · 2024-12-18T09:58:38Z

src/utilities/mod.rs

@@ -22,6 +21,8 @@ use base64::{
    engine::{general_purpose, GeneralPurpose},
    Engine,
 };
+#[cfg(not(feature = "libolm-compat"))]
+pub(crate) use libolm_compat::{pickle_libolm, unpickle_libolm};


You can just import this unconditionally and remove the imports from the line bellow.

src/olm/account/mod.rs

poljar · 2024-12-18T10:13:42Z

src/olm/account/mod.rs

@@ -439,6 +439,45 @@ impl Account {

        pickle.try_into()
    }
+
+    /// Create a dehydrated device pickle.


This is pretty terse, perhaps we should explain a bit what a dehydrated device is and add an example how this can be used.

This also has the IV reuse problem, right? Mentioned here and in the MSC. I wonder if we should fix this properly now and just include a random IV or Nonce in the pickle.

Yup, I had considered fixing the IV problem, but also wasn't sure if I wanted to introduce a new encryption scheme into the code. I'll think about it some more.

We now have a dep on Chacha20 in vodozemac due to the QR Login work, and it's likely going to be needed for the PQ support.

So using a new scheme isn't as problematic anymore.

Added more to the comment, and switch encryption to using Chacha20poly1305

src/olm/account/mod.rs

poljar · 2024-12-18T10:56:12Z

src/olm/account/mod.rs

+    pub(super) struct Pickle {
+        version: u32,
+        private_curve25519_key: Box<[u8; 32]>,
+        private_ed25519_key: Box<[u8; 64]>,
+        one_time_keys: Vec<OneTimeKey>,
+        opt_fallback_key: OptFallbackKey,
+    }


Since this format will come from the homeserver, we should add a fuzz target for it and fuzz it for a bit to ensure that we're not introducing a vulnerability. We already have a fuzz target for all the other formats we receive over the network and have to decode.

Forgot to respond to this earlier.

I've written the basic code:

use afl::fuzz; use arbitrary::Arbitrary; use vodozemac::olm::Account; #[derive(Arbitrary)] struct Data { ciphertext: String, nonce: String, key: [u8; 32], } fn main() { fuzz!(|data: Data| { let _ = Account::from_dehydrated_device(&data.ciphertext, &data.nonce, &data.key); }); }

It looks like the afl documentation is suggesting to provide some example input? Or can I just let it provide random input?

To use it, do I just run cargo afl fuzz? When I do that, I get a permission error -- which may be because my home directory is mounted noexec, so I need to figure out how to get it to run. But I was wondering if there was something else I need to add to the command line.

src/olm/account/mod.rs

…thod

uhoreg · 2025-01-02T17:45:54Z

src/lib.rs

+    }
+}
+
+impl From<chacha20poly1305::aead::Error> for DehydratedDeviceError {


I tried using Decryption(#[from] chacha20poly1305::aead::Error), but it was complaining about some missing traits. So I had to do this instead. I'm not sure if there's a better way.

uhoreg · 2025-01-02T17:46:41Z

src/olm/account/mod.rs

+    pub fn to_dehydrated_device(
+        &self,
+        key: &[u8; 32],
+    ) -> Result<(String, String), crate::DehydratedDeviceError> {


Should I create a new struct instead of returning (String, String)?

Yeah that sounds good, and it might implement Serialize

uhoreg · 2025-01-09T05:06:27Z

The clippy failure seems to be in code that I did not change. I'm guessing that I should create a new PR to fix that, rather than adding the fixes to this PR.

uhoreg force-pushed the dehydration_format branch from 4fbc6c6 to d867b21 Compare November 30, 2024 01:03

add support for new dehydrated device format

fbf8e39

uhoreg force-pushed the dehydration_format branch from 97c798f to fbf8e39 Compare December 4, 2024 02:56

uhoreg marked this pull request as ready for review December 4, 2024 03:00

uhoreg requested review from dkasak and poljar as code owners December 4, 2024 03:00

poljar closed this Dec 5, 2024

poljar reopened this Dec 5, 2024

uhoreg added 2 commits December 13, 2024 21:47

update OTK next ID

764c0d0

so that if new keys get generated, the existing keys don't get overwritten

we also need to save the ed25519 private key

048b0f3

uhoreg mentioned this pull request Dec 16, 2024

Use the dehydrated device format implemented by vodozemac matrix-org/matrix-rust-sdk#4421

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1 task

poljar requested changes Dec 18, 2024

View reviewed changes

uhoreg added 4 commits December 20, 2024 17:59

make changes as requested by review, including changing encryption me…

99be10a

…thod

fmt

00ddc18

hide unused items when not using libolm-compat

6778b11

use unexpanded key in dehydrated device

e8c1622

uhoreg commented Jan 2, 2025

View reviewed changes

uhoreg requested a review from poljar January 6, 2025 14:05

uhoreg added 3 commits January 8, 2025 23:23

add some comments

f234c45

use struct for dehydrated device return value

23d3900

add test for unexpanded key

e22dfcb

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Add support for new dehydrated device format #199

Add support for new dehydrated device format #199

uhoreg commented Nov 27, 2024 •

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uhoreg commented Jan 9, 2025

Add support for new dehydrated device format #199

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Add support for new dehydrated device format #199

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uhoreg commented Jan 9, 2025

uhoreg commented Nov 27, 2024 •

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codecov-commenter commented Dec 5, 2024 •

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