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| 1 | +use crate::key_vault::KeyVault; |
| 2 | +use crate::models::EncryptedMessage; |
| 3 | +use crate::storage::Storage; |
| 4 | +use crate::x3dh::{self, PreKeyBundle}; |
| 5 | +use ed25519_dalek::VerifyingKey; |
| 6 | +use x25519_dalek::PublicKey; |
| 7 | + |
| 8 | +pub struct MessagingService<'a> { |
| 9 | + storage: &'a Storage, |
| 10 | + vault: &'a KeyVault, |
| 11 | +} |
| 12 | + |
| 13 | +impl<'a> MessagingService<'a> { |
| 14 | + pub fn new(storage: &'a Storage, vault: &'a KeyVault) -> Self { |
| 15 | + Self { storage, vault } |
| 16 | + } |
| 17 | + |
| 18 | + /// Encrypts a message for a recipient. |
| 19 | + pub async fn encrypt_message( |
| 20 | + &self, |
| 21 | + recipient_did: &str, |
| 22 | + recipient_ed25519_key: Option<&VerifyingKey>, // Required if new session |
| 23 | + recipient_bundle: Option<&PreKeyBundle>, // Required if new session |
| 24 | + plaintext: &[u8], |
| 25 | + ) -> Result<EncryptedMessage, String> { |
| 26 | + // 1. Load Session |
| 27 | + let session_opt = self |
| 28 | + .storage |
| 29 | + .load_session(recipient_did) |
| 30 | + .await |
| 31 | + .map_err(|e| e.to_string())?; |
| 32 | + |
| 33 | + if let Some(mut session) = session_opt { |
| 34 | + // Existing Session |
| 35 | + let (header, ciphertext) = session.encrypt(plaintext).map_err(|e| e.to_string())?; |
| 36 | + |
| 37 | + // Save Session |
| 38 | + self.storage |
| 39 | + .save_session(recipient_did, &session) |
| 40 | + .await |
| 41 | + .map_err(|e| e.to_string())?; |
| 42 | + |
| 43 | + Ok(EncryptedMessage::Whisper { header, ciphertext }) |
| 44 | + } else { |
| 45 | + // New Session - Needs Bundle |
| 46 | + let bundle = recipient_bundle.ok_or("No session and no PreKeyBundle provided")?; |
| 47 | + let recipient_vk = |
| 48 | + recipient_ed25519_key.ok_or("No session and no Recipient Identity Key provided")?; |
| 49 | + |
| 50 | + let result = x3dh::initialize_alice( |
| 51 | + &self.vault.dh_identity, |
| 52 | + PublicKey::from(&self.vault.dh_identity), |
| 53 | + bundle, |
| 54 | + recipient_vk, |
| 55 | + plaintext, |
| 56 | + )?; |
| 57 | + |
| 58 | + // Save Session |
| 59 | + self.storage |
| 60 | + .save_session(recipient_did, &result.session) |
| 61 | + .await |
| 62 | + .map_err(|e| e.to_string())?; |
| 63 | + |
| 64 | + Ok(EncryptedMessage::X3dhInit { |
| 65 | + sender_identity_key: PublicKey::from(&self.vault.dh_identity), |
| 66 | + ephemeral_key: result.ephemeral_key, |
| 67 | + header: result.initial_header, |
| 68 | + ciphertext: result.initial_ciphertext, |
| 69 | + used_spk: bundle.signed_prekey, // Tell Bob which SPK we used |
| 70 | + used_opk: result.used_opk, // Tell Bob which OPK we used |
| 71 | + }) |
| 72 | + } |
| 73 | + } |
| 74 | + |
| 75 | + /// Decrypts an incoming message |
| 76 | + pub async fn decrypt_message( |
| 77 | + &self, |
| 78 | + sender_did: &str, |
| 79 | + message: EncryptedMessage, |
| 80 | + ) -> Result<Vec<u8>, String> { |
| 81 | + match message { |
| 82 | + EncryptedMessage::Whisper { header, ciphertext } => { |
| 83 | + let mut session = self |
| 84 | + .storage |
| 85 | + .load_session(sender_did) |
| 86 | + .await |
| 87 | + .map_err(|e| e.to_string())? |
| 88 | + .ok_or("No session found for sender")?; |
| 89 | + |
| 90 | + let plaintext = session.decrypt(&header, &ciphertext)?; |
| 91 | + |
| 92 | + self.storage |
| 93 | + .save_session(sender_did, &session) |
| 94 | + .await |
| 95 | + .map_err(|e| e.to_string())?; |
| 96 | + Ok(plaintext) |
| 97 | + } |
| 98 | + EncryptedMessage::X3dhInit { |
| 99 | + sender_identity_key, |
| 100 | + ephemeral_key, |
| 101 | + header, |
| 102 | + ciphertext, |
| 103 | + used_spk, |
| 104 | + used_opk, |
| 105 | + } => { |
| 106 | + // Bob receives init |
| 107 | + |
| 108 | + // 1. Fetch Secrets |
| 109 | + let spk_secret = self |
| 110 | + .storage |
| 111 | + .get_signed_prekey_secret(&used_spk) |
| 112 | + .await |
| 113 | + .map_err(|e| e.to_string())? |
| 114 | + .ok_or("Signed PreKey not found")?; |
| 115 | + |
| 116 | + let mut opk_secret = None; |
| 117 | + if let Some(opk_pub) = used_opk { |
| 118 | + let secret = self |
| 119 | + .storage |
| 120 | + .get_onetime_prekey_secret(&opk_pub) |
| 121 | + .await |
| 122 | + .map_err(|e| e.to_string())? |
| 123 | + .ok_or("One-time PreKey not found")?; |
| 124 | + opk_secret = Some(secret); |
| 125 | + } |
| 126 | + |
| 127 | + // 2. Initialize |
| 128 | + let (session, plaintext) = x3dh::initialize_bob( |
| 129 | + &self.vault.dh_identity, |
| 130 | + &spk_secret, |
| 131 | + opk_secret.as_ref(), |
| 132 | + sender_identity_key, |
| 133 | + ephemeral_key, |
| 134 | + &header, |
| 135 | + &ciphertext, |
| 136 | + )?; |
| 137 | + |
| 138 | + // 3. Save Session |
| 139 | + self.storage |
| 140 | + .save_session(sender_did, &session) |
| 141 | + .await |
| 142 | + .map_err(|e| e.to_string())?; |
| 143 | + |
| 144 | + // 4. Delete consumed OPK |
| 145 | + if let Some(opk_pub) = used_opk { |
| 146 | + self.storage |
| 147 | + .delete_onetime_prekey(&opk_pub) |
| 148 | + .await |
| 149 | + .map_err(|e| e.to_string())?; |
| 150 | + } |
| 151 | + |
| 152 | + Ok(plaintext) |
| 153 | + } |
| 154 | + } |
| 155 | + } |
| 156 | +} |
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