mirror of https://github.com/oxen-io/session-ios
Merge pull request #267 from loki-project/shared-sender-keys
Shared Sender Keys Protocol Changespull/268/head
Niels Andriesse
5 years ago
committed by
GitHub
commit
aa2757f2f8
@ -1 +1 @@
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Subproject commit c89ab147afd32d3dde1e249070dd544abcf9c1c5
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Subproject commit 06051dd2a8aeb819363f6e77de58a038c1ad705e
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@ -0,0 +1,18 @@
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import CryptoSwift
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enum DecryptionUtilities {
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/// - Note: Sync. Don't call from the main thread.
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internal static func decrypt(_ ivAndCiphertext: Data, usingAESGCMWithSymmetricKey symmetricKey: Data) throws -> Data {
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if Thread.isMainThread {
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#if DEBUG
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preconditionFailure("It's illegal to call decrypt(_:usingAESGCMWithSymmetricKey:) from the main thread.")
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#endif
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}
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let iv = ivAndCiphertext[0..<Int(EncryptionUtilities.ivSize)]
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let ciphertext = ivAndCiphertext[Int(EncryptionUtilities.ivSize)...]
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let gcm = GCM(iv: iv.bytes, tagLength: Int(EncryptionUtilities.gcmTagSize), mode: .combined)
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let aes = try AES(key: symmetricKey.bytes, blockMode: gcm, padding: .noPadding)
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return Data(try aes.decrypt(ciphertext.bytes))
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}
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}
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import CryptoSwift
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internal typealias EncryptionResult = (ciphertext: Data, symmetricKey: Data, ephemeralPublicKey: Data)
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enum EncryptionUtilities {
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internal static let gcmTagSize: UInt = 16
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internal static let ivSize: UInt = 12
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/// - Note: Sync. Don't call from the main thread.
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internal static func encrypt(_ plaintext: Data, usingAESGCMWithSymmetricKey symmetricKey: Data) throws -> Data {
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if Thread.isMainThread {
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#if DEBUG
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preconditionFailure("It's illegal to call encrypt(_:usingAESGCMWithSymmetricKey:) from the main thread.")
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#endif
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}
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let iv = Data.getSecureRandomData(ofSize: ivSize)!
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let gcm = GCM(iv: iv.bytes, tagLength: Int(gcmTagSize), mode: .combined)
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let aes = try AES(key: symmetricKey.bytes, blockMode: gcm, padding: .noPadding)
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let ciphertext = try aes.encrypt(plaintext.bytes)
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return iv + Data(bytes: ciphertext)
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}
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/// - Note: Sync. Don't call from the main thread.
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internal static func encrypt(_ plaintext: Data, using hexEncodedX25519PublicKey: String) throws -> EncryptionResult {
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if Thread.isMainThread {
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#if DEBUG
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preconditionFailure("It's illegal to call encrypt(_:forSnode:) from the main thread.")
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#endif
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}
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let x25519PublicKey = Data(hex: hexEncodedX25519PublicKey)
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let ephemeralKeyPair = Curve25519.generateKeyPair()
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let ephemeralSharedSecret = try Curve25519.generateSharedSecret(fromPublicKey: x25519PublicKey, privateKey: ephemeralKeyPair.privateKey)
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let salt = "LOKI"
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let symmetricKey = try HMAC(key: salt.bytes, variant: .sha256).authenticate(ephemeralSharedSecret.bytes)
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let ciphertext = try encrypt(plaintext, usingAESGCMWithSymmetricKey: Data(bytes: symmetricKey))
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return (ciphertext, Data(bytes: symmetricKey), ephemeralKeyPair.publicKey)
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}
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}
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import CryptoSwift
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import SessionMetadataKit
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@objc(LKClosedGroupUtilities)
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public final class ClosedGroupUtilities : NSObject {
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private static let gcmTagSize: UInt = 16
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private static let ivSize: UInt = 12
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@objc(LKSSKDecryptionError)
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public class SSKDecryptionError : NSError { // Not called `Error` for Obj-C interoperablity
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@objc public static let invalidGroupPublicKey = SSKDecryptionError(domain: "SSKErrorDomain", code: 1, userInfo: [ NSLocalizedDescriptionKey : "Invalid group public key." ])
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@objc public static let noData = SSKDecryptionError(domain: "SSKErrorDomain", code: 2, userInfo: [ NSLocalizedDescriptionKey : "Received an empty envelope." ])
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@objc public static let noGroupPrivateKey = SSKDecryptionError(domain: "SSKErrorDomain", code: 3, userInfo: [ NSLocalizedDescriptionKey : "Missing group private key." ])
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}
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@objc(encryptData:usingGroupPublicKey:transaction:error:)
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public static func encrypt(data: Data, groupPublicKey: String, transaction: YapDatabaseReadWriteTransaction) throws -> Data {
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// 1. ) Encrypt the data with the user's sender key
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guard let userPublicKey = OWSIdentityManager.shared().identityKeyPair()?.hexEncodedPublicKey else {
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throw SMKError.assertionError(description: "[Loki] Couldn't find user key pair.")
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}
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let ciphertextAndKeyIndex = try SharedSenderKeysImplementation.shared.encrypt(data, forGroupWithPublicKey: groupPublicKey,
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senderPublicKey: userPublicKey, protocolContext: transaction)
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let ivAndCiphertext = ciphertextAndKeyIndex[0] as! Data
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let keyIndex = ciphertextAndKeyIndex[1] as! UInt
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let encryptedMessage = ClosedGroupCiphertextMessage(_throws_withIVAndCiphertext: ivAndCiphertext, senderPublicKey: Data(hex: userPublicKey), keyIndex: UInt32(keyIndex))
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// 2. ) Encrypt the result for the group's public key to hide the sender public key and key index
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let (ciphertext, _, ephemeralPublicKey) = try EncryptionUtilities.encrypt(encryptedMessage.serialized, using: groupPublicKey.removing05PrefixIfNeeded())
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// 3. ) Wrap the result
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return try SSKProtoClosedGroupCiphertextMessageWrapper.builder(ciphertext: ciphertext, ephemeralPublicKey: ephemeralPublicKey).build().serializedData()
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}
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@objc(decryptEnvelope:transaction:error:)
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public static func decrypt(envelope: SSKProtoEnvelope, transaction: YapDatabaseReadWriteTransaction) throws -> [Any] {
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let (plaintext, senderPublicKey) = try decrypt(envelope: envelope, transaction: transaction)
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return [ plaintext, senderPublicKey ]
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}
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public static func decrypt(envelope: SSKProtoEnvelope, transaction: YapDatabaseReadWriteTransaction) throws -> (plaintext: Data, senderPublicKey: String) {
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// 1. ) Check preconditions
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guard let groupPublicKey = envelope.source, SharedSenderKeysImplementation.shared.isClosedGroup(groupPublicKey) else {
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throw SSKDecryptionError.invalidGroupPublicKey
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}
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guard let data = envelope.content else {
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throw SSKDecryptionError.noData
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}
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guard let hexEncodedGroupPrivateKey = Storage.getClosedGroupPrivateKey(for: groupPublicKey) else {
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throw SSKDecryptionError.noGroupPrivateKey
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}
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let groupPrivateKey = Data(hex: hexEncodedGroupPrivateKey)
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// 2. ) Parse the wrapper
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let wrapper = try SSKProtoClosedGroupCiphertextMessageWrapper.parseData(data)
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let ivAndCiphertext = wrapper.ciphertext
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let ephemeralPublicKey = wrapper.ephemeralPublicKey
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// 3. ) Decrypt the data inside
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let ephemeralSharedSecret = try Curve25519.generateSharedSecret(fromPublicKey: ephemeralPublicKey, privateKey: groupPrivateKey)
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let salt = "LOKI"
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let symmetricKey = try HMAC(key: salt.bytes, variant: .sha256).authenticate(ephemeralSharedSecret.bytes)
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let closedGroupCiphertextMessageAsData = try DecryptionUtilities.decrypt(ivAndCiphertext, usingAESGCMWithSymmetricKey: Data(symmetricKey))
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// 4. ) Parse the closed group ciphertext message
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let closedGroupCiphertextMessage = ClosedGroupCiphertextMessage(_throws_with: closedGroupCiphertextMessageAsData)
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let senderPublicKey = closedGroupCiphertextMessage.senderPublicKey.toHexString()
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// 5. ) Use the info inside the closed group ciphertext message to decrypt the actual message content
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let plaintext = try SharedSenderKeysImplementation.shared.decrypt(closedGroupCiphertextMessage.ivAndCiphertext, forGroupWithPublicKey: groupPublicKey,
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senderPublicKey: senderPublicKey, keyIndex: UInt(closedGroupCiphertextMessage.keyIndex), protocolContext: transaction)
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// 6. ) Return
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return (plaintext, senderPublicKey)
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}
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}
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