Decrypting should work.

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

diff --git a/labo2-fsharp/CryptoFile/API.fs b/labo2-fsharp/CryptoFile/API.fs
index e4a7008..0014c1e 100644 (file)
--- a/labo2-fsharp/CryptoFile/API.fs
+++ b/labo2-fsharp/CryptoFile/API.fs
@@ -2,19 +2,24 @@
 open System.IO
 
 type internal Metadata (d: (string * string) list) =
-    new (stream : Stream, size: int) =
-        let binaryReader = new BinaryReader (stream)
-        new Metadata ([])
+    new (stream : Stream) =
+        let reader = new BinaryReader (stream)
+        let length = reader.ReadByte () |> int
+        new Metadata ([for i in 1..length -> reader.ReadString (), reader.ReadString ()])
+
+    // May raise 'KeyNotFoundException'.
+    member this.get (key: string) : string =
+        List.pick (function
+                    | (k, v) when k = key -> Some (v)
+                    | _ -> None) d
 
     member this.WriteTo (stream : Stream) =
-        let memoryStream = new MemoryStream () // To know the serialized meta-data size before writtent them to 'stream'.
-        let memoryWriter = new BinaryWriter (memoryStream)
-        List.iter (fun (key : string, value : string) -> memoryWriter.Write key; memoryWriter.Write value) d
-        (new BinaryWriter (stream)).Write (int memoryStream.Length)
-        memoryStream.CopyTo (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 Metadata =
         let filename = "filename"
         let creationTimeKey = "file-creation-time"
 
@@ -37,8 +42,8 @@ module API =
         let cryptoWriter = new BinaryWriter (cryptoStream)
 
         // Write the file metadata.
-        let metaData = new Metadata ([MetaData.filename, fileInfo.Name
-                                      MetaData.creationTimeKey, fileInfo.CreationTimeUtc.Ticks.ToString ()])
+        let metaData = new Metadata ([Metadata.filename, fileInfo.Name
+                                      Metadata.creationTimeKey, fileInfo.CreationTimeUtc.Ticks.ToString ()])
         metaData.WriteTo cryptoStream
 
         // Write the content of the file.
@@ -54,4 +59,31 @@ module API =
         ()
 
     let decryptFile (sourceFilePath : string) (targetDirPath : string) (signaturePubKey: Key) (decryptPrivKey : Key) =
-        ()
\ No newline at end of file
+        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]
+
+        // 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
+
+        // 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
+        ()