sas: Allow to just get the emoji index instead of the emoji and descryption

matrix_sdk_crypto/src/verification/sas/helpers.rs

@@ -436,6 +436,43 @@ pub fn get_emoji(
     bytes_to_emoji(bytes)
 }
 
+/// Get the index of the emoji of the short authentication string.
+///
+/// Returns seven u8 numbers in the range from 0 to 63 inclusive, those numbers
+/// can be converted to a unique emoji defined by the spec using the
+/// [emoji_from_index](#method.emoji_from_index) method.
+///
+/// # Arguments
+///
+/// * `sas` - The Olm SAS object that can be used to generate bytes using the
+/// shared secret.
+///
+/// * `ids` - The ids that are used for this SAS authentication flow.
+///
+/// * `flow_id` - The unique id that identifies this SAS verification process.
+///
+/// * `we_started` - Flag signaling if the SAS process was started on our side.
+///
+/// # Panics
+///
+/// This will panic if the public key of the other side wasn't set.
+pub fn get_emoji_index(
+    sas: &OlmSas,
+    ids: &SasIds,
+    their_pubkey: &str,
+    flow_id: &str,
+    we_started: bool,
+) -> [u8; 7] {
+    let bytes = sas
+        .generate_bytes(
+            &extra_info_sas(&ids, &sas.public_key(), their_pubkey, &flow_id, we_started),
+            6,
+        )
+        .expect("Can't generate bytes");
+
+    bytes_to_emoji_index(bytes)
+}
+
 fn bytes_to_emoji_index(bytes: Vec<u8>) -> [u8; 7] {
     let bytes: Vec<u64> = bytes.iter().map(|b| *b as u64).collect();
     // Join the 6 bytes into one 64 bit unsigned int. This u64 will contain 48

matrix_sdk_crypto/src/verification/sas/inner_sas.rs

@@ -351,6 +351,14 @@ impl InnerSas {
         }
     }
 
+    pub fn emoji_index(&self) -> Option<[u8; 7]> {
+        match self {
+            InnerSas::KeyRecieved(s) => Some(s.get_emoji_index()),
+            InnerSas::MacReceived(s) => Some(s.get_emoji_index()),
+            _ => None,
+        }
+    }
+
     pub fn decimals(&self) -> Option<(u16, u16, u16)> {
         match self {
             InnerSas::KeyRecieved(s) => Some(s.get_decimal()),

matrix_sdk_crypto/src/verification/sas/mod.rs

@@ -633,6 +633,16 @@ impl Sas {
         self.inner.lock().unwrap().emoji()
     }
 
+    /// Get the index of the emoji representing the short auth string
+    ///
+    /// Returns None if we can't yet present the short auth string, otherwise
+    /// seven u8 numbers in the range from 0 to 63 inclusive which can be
+    /// converted to an emoji using the
+    /// [relevant spec entry](https://spec.matrix.org/unstable/client-server-api/#sas-method-emoji).
+    pub fn emoji_index(&self) -> Option<[u8; 7]> {
+        self.inner.lock().unwrap().emoji_index()
+    }
+
     /// Get the decimal version of the short auth string.
     ///
     /// Returns None if we can't yet present the short auth string, otherwise a

matrix_sdk_crypto/src/verification/sas/sas_state.rs

@@ -47,7 +47,8 @@ use super::{
         AcceptContent, CancelContent, DoneContent, KeyContent, MacContent, StartContent,
     },
     helpers::{
-        calculate_commitment, get_decimal, get_emoji, get_mac_content, receive_mac_event, SasIds,
+        calculate_commitment, get_decimal, get_emoji, get_emoji_index, get_mac_content,
+        receive_mac_event, SasIds,
     },
 };
 
@@ -757,6 +758,20 @@ impl SasState<KeyReceived> {
         )
     }
 
+    /// Get the index of the emoji of the short authentication string.
+    ///
+    /// Returns seven u8 numbers in the range from 0 to 63 inclusive, those numbers
+    /// can be converted to a unique emoji defined by the spec.
+    pub fn get_emoji_index(&self) -> [u8; 7] {
+        get_emoji_index(
+            &self.inner.lock().unwrap(),
+            &self.ids,
+            &self.state.their_pubkey,
+            self.verification_flow_id.as_str(),
+            self.state.we_started,
+        )
+    }
+
     /// Get the decimal version of the short authentication string.
     ///
     /// Returns a tuple containing three 4 digit integer numbers that represent
@@ -978,6 +993,20 @@ impl SasState<MacReceived> {
         )
     }
 
+    /// Get the index of the emoji of the short authentication string.
+    ///
+    /// Returns seven u8 numbers in the range from 0 to 63 inclusive, those numbers
+    /// can be converted to a unique emoji defined by the spec.
+    pub fn get_emoji_index(&self) -> [u8; 7] {
+        get_emoji_index(
+            &self.inner.lock().unwrap(),
+            &self.ids,
+            &self.state.their_pubkey,
+            self.verification_flow_id.as_str(),
+            self.state.we_started,
+        )
+    }
+
     /// Get the decimal version of the short authentication string.
     ///
     /// Returns a tuple containing three 4 digit integer numbers that represent