openmls/framing/
public_message.rs

1//! # PublicMessage
2//!
3//! A PublicMessage is a framing structure for MLS messages. It can contain
4//! Proposals, Commits and application messages.
5
6use std::io::Write;
7
8use openmls_traits::{crypto::OpenMlsCrypto, types::Ciphersuite};
9use tls_codec::{
10    Serialize as TlsSerializeTrait, TlsDeserialize, TlsDeserializeBytes, TlsSerialize, TlsSize,
11};
12
13use super::{
14    mls_auth_content::{AuthenticatedContent, FramedContentAuthData},
15    mls_content::{framed_content_tbs_serialized_detached, AuthenticatedContentTbm, FramedContent},
16    *,
17};
18use crate::{error::LibraryError, versions::ProtocolVersion};
19
20/// Wrapper around a `Mac` used for type safety.
21#[derive(
22    Debug,
23    PartialEq,
24    Clone,
25    Serialize,
26    Deserialize,
27    TlsSerialize,
28    TlsDeserialize,
29    TlsDeserializeBytes,
30    TlsSize,
31)]
32pub(crate) struct MembershipTag(pub(crate) Mac);
33
34/// [`PublicMessage`] is a framing structure for MLS messages. It can contain
35/// Proposals, Commits and application messages.
36///
37/// 9. Message framing
38///
39/// ```c
40/// // draft-ietf-mls-protocol-17
41///
42/// struct {
43///     FramedContent content;
44///     FramedContentAuthData auth;
45///     optional<MAC> membership_tag;
46/// } PublicMessage;
47/// ```
48#[derive(Debug, PartialEq, Clone, Serialize, Deserialize)]
49pub struct PublicMessage {
50    pub(crate) content: FramedContent,
51    pub(crate) auth: FramedContentAuthData,
52    pub(crate) membership_tag: Option<MembershipTag>,
53}
54
55#[cfg(test)]
56impl PublicMessage {
57    pub(crate) fn content(&self) -> &crate::framing::mls_content::FramedContentBody {
58        &self.content.body
59    }
60
61    pub fn set_confirmation_tag(&mut self, confirmation_tag: Option<ConfirmationTag>) {
62        self.auth.confirmation_tag = confirmation_tag;
63    }
64
65    pub fn unset_membership_tag(&mut self) {
66        self.membership_tag = None;
67    }
68
69    pub(crate) fn set_content(&mut self, content: FramedContentBody) {
70        self.content.body = content;
71    }
72
73    pub fn set_epoch(&mut self, epoch: u64) {
74        self.content.epoch = epoch.into();
75    }
76
77    pub fn confirmation_tag(&self) -> Option<&ConfirmationTag> {
78        self.auth.confirmation_tag.as_ref()
79    }
80
81    pub(crate) fn invalidate_signature(&mut self) {
82        let mut modified_signature = self.auth.signature.as_slice().to_vec();
83        modified_signature[0] ^= 0xFF;
84        self.auth.signature.modify(&modified_signature);
85    }
86
87    /// Set the sender.
88    pub(crate) fn set_sender(&mut self, sender: Sender) {
89        self.content.sender = sender;
90    }
91
92    /// Set the group id.
93    pub(crate) fn set_group_id(&mut self, group_id: GroupId) {
94        self.content.group_id = group_id;
95    }
96
97    /// Returns `true` if this is a handshake message and `false` otherwise.
98    pub(crate) fn is_handshake_message(&self) -> bool {
99        self.content_type().is_handshake_message()
100    }
101}
102
103impl From<AuthenticatedContent> for PublicMessage {
104    fn from(v: AuthenticatedContent) -> Self {
105        Self {
106            content: v.content,
107            auth: v.auth,
108            membership_tag: None,
109        }
110    }
111}
112
113impl PublicMessage {
114    /// Returns the [`ContentType`] of the message.
115    pub fn content_type(&self) -> ContentType {
116        self.content.body.content_type()
117    }
118
119    /// Returns the [`GroupId`] of the group the message was sent in.
120    pub fn group_id(&self) -> &GroupId {
121        &self.content.group_id
122    }
123
124    /// Returns the epoch of the message.
125    pub fn epoch(&self) -> GroupEpoch {
126        self.content.epoch
127    }
128
129    /// Get the sender of this message.
130    pub(crate) fn sender(&self) -> &Sender {
131        &self.content.sender
132    }
133
134    /// Adds a membership tag to this `PublicMessage`. The membership_tag is
135    /// produced using the the membership secret.
136    ///
137    /// This should be used after signing messages from group members.
138    pub(crate) fn set_membership_tag(
139        &mut self,
140        crypto: &impl OpenMlsCrypto,
141        ciphersuite: Ciphersuite,
142        membership_key: &MembershipKey,
143        serialized_context: &[u8],
144    ) -> Result<(), LibraryError> {
145        let tbs_payload = framed_content_tbs_serialized_detached(
146            ProtocolVersion::default(),
147            WireFormat::PublicMessage,
148            &self.content,
149            &self.content.sender,
150            serialized_context,
151        )
152        .map_err(LibraryError::missing_bound_check)?;
153        let tbm_payload = AuthenticatedContentTbm::new(&tbs_payload, &self.auth)?;
154        let membership_tag = membership_key.tag_message(crypto, ciphersuite, tbm_payload)?;
155
156        self.membership_tag = Some(membership_tag);
157        Ok(())
158    }
159
160    #[cfg(test)]
161    pub(crate) fn set_membership_tag_test(&mut self, membership_tag: MembershipTag) {
162        self.membership_tag = Some(membership_tag);
163    }
164}
165
166#[cfg(test)]
167impl From<PublicMessage> for FramedContentTbs {
168    fn from(v: PublicMessage) -> Self {
169        FramedContentTbs {
170            version: ProtocolVersion::default(),
171            wire_format: WireFormat::PublicMessage,
172            content: v.content,
173            serialized_context: None,
174        }
175    }
176}
177
178// -------------------------------------------------------------------------------------------------
179
180/// ```c
181/// // draft-ietf-mls-protocol-17
182/// struct {
183///     WireFormat wire_format;
184///     FramedContent content; /* with content_type == commit */
185///     opaque signature<V>;
186///} ConfirmedTranscriptHashInput;
187/// ```
188#[derive(TlsSerialize, TlsSize)]
189pub(crate) struct ConfirmedTranscriptHashInput<'a> {
190    pub(super) wire_format: WireFormat,
191    pub(super) mls_content: &'a FramedContent,
192    pub(super) signature: &'a Signature,
193}
194
195impl ConfirmedTranscriptHashInput<'_> {
196    pub(crate) fn calculate_confirmed_transcript_hash(
197        self,
198        crypto: &impl OpenMlsCrypto,
199        ciphersuite: Ciphersuite,
200        interim_transcript_hash: &[u8],
201    ) -> Result<Vec<u8>, LibraryError> {
202        let serialized: Vec<u8> = self
203            .tls_serialize_detached()
204            .map_err(LibraryError::missing_bound_check)?;
205
206        crypto
207            .hash(
208                ciphersuite.hash_algorithm(),
209                &[interim_transcript_hash, &serialized].concat(),
210            )
211            .map_err(LibraryError::unexpected_crypto_error)
212    }
213}
214
215impl<'a> TryFrom<&'a AuthenticatedContent> for ConfirmedTranscriptHashInput<'a> {
216    type Error = &'static str;
217
218    fn try_from(mls_content: &'a AuthenticatedContent) -> Result<Self, Self::Error> {
219        if !matches!(mls_content.content().content_type(), ContentType::Commit) {
220            return Err("PublicMessage needs to contain a Commit.");
221        }
222
223        Ok(ConfirmedTranscriptHashInput {
224            wire_format: mls_content.wire_format(),
225            mls_content: &mls_content.content,
226            signature: mls_content.signature(),
227        })
228    }
229}
230
231// -------------------------------------------------------------------------------------------------
232
233/// ```c
234/// // draft-ietf-mls-protocol-17
235/// struct {
236///     MAC confirmation_tag;
237/// } InterimTranscriptHashInput;
238/// ```
239#[derive(TlsSerialize, TlsSize)]
240pub(crate) struct InterimTranscriptHashInput<'a> {
241    pub(crate) confirmation_tag: &'a ConfirmationTag,
242}
243
244impl InterimTranscriptHashInput<'_> {
245    pub fn calculate_interim_transcript_hash(
246        self,
247        crypto: &impl OpenMlsCrypto,
248        ciphersuite: Ciphersuite,
249        confirmed_transcript_hash: &[u8],
250    ) -> Result<Vec<u8>, LibraryError> {
251        let serialized = self
252            .tls_serialize_detached()
253            .map_err(LibraryError::missing_bound_check)?;
254
255        crypto
256            .hash(
257                ciphersuite.hash_algorithm(),
258                &[confirmed_transcript_hash, &serialized].concat(),
259            )
260            .map_err(LibraryError::unexpected_crypto_error)
261    }
262}
263
264impl<'a> TryFrom<&'a PublicMessage> for InterimTranscriptHashInput<'a> {
265    type Error = &'static str;
266
267    fn try_from(public_message: &'a PublicMessage) -> Result<Self, Self::Error> {
268        match public_message.auth.confirmation_tag.as_ref() {
269            Some(confirmation_tag) => Ok(InterimTranscriptHashInput { confirmation_tag }),
270            None => Err("PublicMessage needs to contain a confirmation tag."),
271        }
272    }
273}
274
275impl<'a> From<&'a ConfirmationTag> for InterimTranscriptHashInput<'a> {
276    fn from(confirmation_tag: &'a ConfirmationTag) -> Self {
277        InterimTranscriptHashInput { confirmation_tag }
278    }
279}
280
281// -------------------------------------------------------------------------------------------------
282
283impl Size for PublicMessage {
284    #[inline]
285    fn tls_serialized_len(&self) -> usize {
286        self.content.tls_serialized_len()
287            + self.auth.tls_serialized_len()
288            + if let Some(membership_tag) = &self.membership_tag {
289                membership_tag.tls_serialized_len()
290            } else {
291                0
292            }
293    }
294}
295
296impl TlsSerializeTrait for PublicMessage {
297    fn tls_serialize<W: Write>(&self, writer: &mut W) -> Result<usize, tls_codec::Error> {
298        // Serialize the content, not the TBS.
299        let mut written = self.content.tls_serialize(writer)?;
300        written += self.auth.tls_serialize(writer)?;
301        written += if let Some(membership_tag) = &self.membership_tag {
302            membership_tag.tls_serialize(writer)?
303        } else {
304            0
305        };
306        Ok(written)
307    }
308}
openmls/framing/public_message.rs

openmls/framing/
public_message.rs
