Add descriptions to Errors

Sources/SFrame/MLS.swift

@@ -15,6 +15,22 @@ public enum MLSError: Error {
     case contextOverflow
     /// Epoch bits must be 0 < x < 64.
     case badEpochBits
+
+    public var localizedDescription: String {
+        switch self {
+        case .unknownEpoch:
+            return "Unknown epoch."
+
+        case .senderOverflow:
+            return "Sender ID exceeds maximum allowed."
+
+        case .contextOverflow:
+            return "Context ID exceeds maximum allowed."
+
+        case .badEpochBits:
+            return "Epoch bits must be between 1 and 63."
+        }
+    }
 }
 
 /// Provides an interface to utilize SFrame with MLS keying.

Sources/SFrame/Provider.swift

@@ -76,4 +76,11 @@ public protocol CryptoProvider {
 public enum CryptoProviderError: Error {
     /// This provider does not support the requested cipher suite.
     case unsupportedCipherSuite
+
+    public var localizedDescription: String {
+        switch self {
+        case .unsupportedCipherSuite:
+            return "This provider does not support the requested cipher suite."
+        }
+    }
 }

Sources/SFrame/SFrame.swift

@@ -17,7 +17,22 @@ public enum SFrameError: Error {
     case existingKey
     case badParameter
     case malformedCipherText
-    case keyMisuse
+
+    public var localizedDescription: String {
+        switch self {
+        case .missingKey:
+            return "The required key is missing."
+
+        case .existingKey:
+            return "This key already exists."
+
+        case .badParameter:
+            return "A bit size parameter was invalid."
+
+        case .malformedCipherText:
+            return "The ciphertext is malformed."
+        }
+    }
 }
 
 /// The operation this key is to be used for.

Sources/SFrame/SyntheticAEAD.swift

@@ -9,6 +9,19 @@ public enum SyntheticAEADError: Error {
     case missingKeySize
     case authenticationFailure
     case badKeySize
+
+    public var localizedDescription: String {
+        switch self {
+        case .missingKeySize:
+            return "The cipher suite does not specify a key size."
+
+        case .authenticationFailure:
+            return "Authentication failed."
+
+        case .badKeySize:
+            return "The provided key size does not match the cipher suite requirements."
+        }
+    }
 }
 
 /// SFrame AES-CTR with SHA2 implementation.

Sources/SFrame/Utilities.swift

@@ -4,17 +4,24 @@
 
 import Foundation
 
-public enum DataError: Error {
-    case lengthMismatch
-}
-
 // SealedBox implementation.
 internal struct SealedDataBox: SealedBox {
     internal let authTag: Data
     internal let encrypted: Data
     internal let nonceBytes: Data
 }
 
+public enum DataError: Error {
+    case lengthMismatch
+
+    public var localizedDescription: String {
+        switch self {
+        case .lengthMismatch:
+            return "XOR requires buffers of equal length."
+        }
+    }
+}
+
 extension Data {
     /// Initialize a view into a contiguous byte buffer.
     /// - Parameter bytes: The contiguous byte buffer to expose a view into.

Tests/SFrameTests/Utilities.swift

@@ -176,6 +176,16 @@ internal func hexToData(_ hex: String) -> Data {
 internal enum TestError: Error {
     case missingVectors
     case unsupportedCipherSuite
+
+    internal var localizedDescription: String {
+        switch self {
+        case .missingVectors:
+            return "Test vectors are missing."
+
+        case .unsupportedCipherSuite:
+            return "The cipher suite is not supported."
+        }
+    }
 }
 
 internal func loadTestVectors() throws -> TestVectors {