Clean up.

[crypto_lab2.git] / labo2-fsharp / CryptoFile / API.fs

diff --git a/labo2-fsharp/CryptoFile/API.fs b/labo2-fsharp/CryptoFile/API.fs
index 0014c1e..2f80c07 100644 (file)
--- a/labo2-fsharp/CryptoFile/API.fs
+++ b/labo2-fsharp/CryptoFile/API.fs
@@ -1,11 +1,21 @@
 namespace CryptoFile
+
+open System
 open System.IO
 
+// To read and write metadata.
 type internal Metadata (d: (string * string) list) =
+    // Read metadata from a stream.
     new (stream : Stream) =
         let reader = new BinaryReader (stream)
         let length = reader.ReadByte () |> int
-        new Metadata ([for i in 1..length -> reader.ReadString (), reader.ReadString ()])
+        Metadata ([for i in 1..length -> reader.ReadString (), reader.ReadString ()])
+
+    // Write metadata to a stream.
+    member this.WriteTo (stream : Stream) =
+        let writer = new BinaryWriter (stream)
+        writer.Write (byte d.Length)
+        List.iter (fun (key : string, value : string) -> writer.Write key; writer.Write value) d
 
     // May raise 'KeyNotFoundException'.
     member this.get (key: string) : string =
@@ -13,37 +23,34 @@ type internal Metadata (d: (string * string) list) =
                     | (k, v) when k = key -> Some (v)
                     | _ -> None) d
 
-    member this.WriteTo (stream : Stream) =
-        let writer = new BinaryWriter (stream)
-        writer.Write (byte d.Length)
-        List.iter (fun (key : string, value : string) -> writer.Write key; writer.Write value) d
-
 module API =
-    module internal Metadata =
+    module internal MetadataKeys =
         let filename = "filename"
-        let creationTimeKey = "file-creation-time"
+        let modificationTime = "file-modification-time"
+
+    let internal (@@) a1 a2 = Array.append a1 a2
 
     let generatKeysPair : Key * Key = Crypto.generateRSAKeysPair
 
-    // Encrypt a given file
     let encryptFile (inputFilePath : string) (outputFilePath : string) (signaturePrivKey: Key) (cryptPubKey : Key)  =
-        let keyAES, keyMAC, iv = Crypto.rand 32, Crypto.rand 32, Crypto.rand 16
-        let fileInfo = new FileInfo (inputFilePath)
-        use inputStream = new FileStream (inputFilePath, FileMode.Open, FileAccess.Read)
+        let keyAES, keyMAC, iv = Crypto.rand 16, Crypto.rand 32, Crypto.rand 16
+        let fileInfo = FileInfo (inputFilePath)
+        use inputStream = fileInfo.OpenRead ()
         use outputStream = new FileStream (outputFilePath, FileMode.Create, FileAccess.Write)
-        let writer = new BinaryWriter (outputStream)
+        use writer = new BinaryWriter (outputStream)
 
-        writer.Seek (32 + 256, SeekOrigin.Current) |> ignore // Skips mac and signature. They will be written later.
+        outputStream.Position <- 32L + 256L // Skips mac and signature. They will be written later.
 
-        Crypto.encryptRSA cryptPubKey (Array.append keyAES <| Array.append keyMAC iv) |> writer.Write
+        Crypto.encryptRSA cryptPubKey (keyAES @@ keyMAC @@ iv) |> writer.Write
 
-        let (hmacStream, hmac) = Crypto.HMACStream keyMAC outputStream
+        // Plaintext -> cryptoStream -> hmacStream -> cyphertext.
+        let hmacStream, hmac = Crypto.HMACStream keyMAC outputStream
         use cryptoStream = Crypto.encryptAES keyAES iv hmacStream
-        let cryptoWriter = new BinaryWriter (cryptoStream)
+        use cryptoWriter = new BinaryWriter (cryptoStream)
 
         // Write the file metadata.
-        let metaData = new Metadata ([Metadata.filename, fileInfo.Name
-                                      Metadata.creationTimeKey, fileInfo.CreationTimeUtc.Ticks.ToString ()])
+        let metaData = Metadata ([MetadataKeys.filename, fileInfo.Name
+                                  MetadataKeys.modificationTime, fileInfo.LastWriteTimeUtc.Ticks.ToString ()])
         metaData.WriteTo cryptoStream
 
         // Write the content of the file.
@@ -56,23 +63,29 @@ module API =
 
         // Write the signature.
         Crypto.signRSA signaturePrivKey hmac.Hash |> writer.Write
-        ()
 
+    // May raise one of the following error:
+    //  * IntegrityError
+    //  * SignatureMismatch 
+    //  * UnableToDecryptAESKeys
     let decryptFile (sourceFilePath : string) (targetDirPath : string) (signaturePubKey: Key) (decryptPrivKey : Key) =
         use inputStream = new FileStream (sourceFilePath, FileMode.Open, FileAccess.Read)
         use reader = new BinaryReader (inputStream)
         let mac = reader.ReadBytes 32
         let signature = reader.ReadBytes 256
-        let keys = reader.ReadBytes 256 |> Crypto.decryptRSA decryptPrivKey
-        let keyAES = keys.[0..31]
-        let keyMAC = keys.[32..63]
-        let iv = keys.[64..79]
+        let keys = 
+            try reader.ReadBytes 256 |> Crypto.decryptRSA decryptPrivKey
+            with 
+                | :? Security.Cryptography.CryptographicException -> raise UnableToDecryptAESKeys
+        let keyAES = keys.[0..15]
+        let keyMAC = keys.[16..47]
+        let iv = keys.[48..63]
 
         // Integrity validation.
         let mac' = Crypto.ComputeHMAC keyMAC inputStream
         if mac' <> mac then
             raise IntegrityError
-
+        
         // Authentication validation.
         if not <| Crypto.verifySignRSA signaturePubKey mac' signature then
             raise SignatureMismatch
@@ -80,10 +93,12 @@ module API =
         // Decrypt metadata.
         inputStream.Position <- 32L + 256L + 256L
         use cryptoStream = Crypto.decryptAES keyAES iv inputStream
-        let metadata = new Metadata (cryptoStream)
-
-        // Create the file and write.
-        let filename = metadata.get Metadata.filename
-        use outputStream = new FileStream (Path.Combine (targetDirPath, filename), FileMode.Create, FileAccess.Write)
-        cryptoStream.CopyTo outputStream
-        ()
+        let metadata = Metadata cryptoStream
+
+        // Create the file and write its content and metadata.
+        let filePath = Path.Combine (targetDirPath, metadata.get MetadataKeys.filename)
+        let modificationTime = DateTime (metadata.get MetadataKeys.modificationTime |> int64)
+        let fileInfo = FileInfo filePath
+        using (fileInfo.Create ()) <| fun outputStream -> cryptoStream.CopyTo outputStream
+        fileInfo.LastWriteTimeUtc <- modificationTime
+    
\ No newline at end of file