Typos in report + 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 886b0d9..925f933 100644 (file)
--- a/labo2-fsharp/CryptoFile/API.fs
+++ b/labo2-fsharp/CryptoFile/API.fs
@@ -3,21 +3,21 @@
 open System
 open System.IO
 
-// To read and write metadata.
+/// To read and write metadata.
 type internal Metadata (d: (string * string) list) =
-    // Read metadata from a stream.
+    /// Read metadata from a stream.
     new (stream : Stream) =
         let reader = new BinaryReader (stream)
         let length = reader.ReadByte () |> int
-        Metadata ([for i in 1..length -> reader.ReadString (), reader.ReadString ()])
+        Metadata ([for _ in 1 .. length -> reader.ReadString (), reader.ReadString ()])
 
-    // Write metadata to a stream.
+    /// 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'.
+    /// May raise 'KeyNotFoundException'.
     member this.get (key: string) : string =
         List.pick (function
                     | (k, v) when k = key -> Some (v)
@@ -30,8 +30,16 @@ module API =
 
     let internal (@@) a1 a2 = Array.append a1 a2
 
-    let generatKeysPair : Key * Key = Crypto.generateRSAKeysPair
+    let test = 256 / 8
+    let hmacSize = 256 / 8 // [byte].
+    let signatureSize = Crypto.rsaKeySize / 8 // [byte].
+    let keysSize = Crypto.rsaKeySize / 8 // [byte].
 
+    let generatKeysPair () : Key * Key = Crypto.generateRSAKeysPair ()
+
+    /// Format of the container:
+    ///  <mac><signature><encrypted keys><cyphertext>
+    /// Where the sizes of the three first parts are given by 'hmacSize', 'signatureSize' and 'keysSize'.
     let encryptFile (inputFilePath : string) (outputFilePath : string) (signaturePrivKey: Key) (cryptPubKey : Key)  =
         let keyAES, keyMAC, iv = Crypto.rand 16, Crypto.rand 32, Crypto.rand 16
         let fileInfo = FileInfo (inputFilePath)
@@ -39,7 +47,7 @@ module API =
         use outputStream = new FileStream (outputFilePath, FileMode.Create, FileAccess.Write)
         use writer = new BinaryWriter (outputStream)
 
-        outputStream.Position <- 32L + 256L // Skips mac and signature. They will be written later.
+        outputStream.Position <- (int64 <| hmacSize + signatureSize) // Skips mac and signature. They will be written later.
 
         Crypto.encryptRSA cryptPubKey (keyAES @@ keyMAC @@ iv) |> writer.Write
 
@@ -64,22 +72,22 @@ module API =
         // Write the signature.
         Crypto.signRSA signaturePrivKey hmac.Hash |> writer.Write
 
-    // May raise one of the following error:
-    //  * IntegrityError
-    //  * SignatureMismatch 
-    //  * UnableToDecryptAESKeys
+    /// 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 mac = reader.ReadBytes hmacSize
+        let signature = reader.ReadBytes signatureSize
         let keys = 
-            try reader.ReadBytes 256 |> Crypto.decryptRSA decryptPrivKey
+            try reader.ReadBytes keysSize |> Crypto.decryptRSA decryptPrivKey
             with 
-                | :? Security.Cryptography.CryptographicException -> raise UnableToDecryptAESKeys
-        let keyAES = keys.[0..15]
-        let keyMAC = keys.[16..47]
-        let iv = keys.[48..63]
+                | :? Security.Cryptography.CryptographicException -> raise UnableToDecryptKeys
+        let keyAES = keys.[0 .. 15]
+        let keyMAC = keys.[16 .. 47]
+        let iv = keys.[48 .. 63]
 
         // Integrity validation.
         let mac' = Crypto.ComputeHMAC keyMAC inputStream
@@ -91,14 +99,14 @@ module API =
             raise SignatureMismatch
 
         // Decrypt metadata.
-        inputStream.Position <- 32L + 256L + 256L
+        inputStream.Position <- (int64 <| hmacSize + signatureSize + keysSize)
         use cryptoStream = Crypto.decryptAES keyAES iv inputStream
-        let metadata = Metadata (cryptoStream)
+        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
+        let fileInfo = FileInfo filePath
+        using (fileInfo.Create ()) cryptoStream.CopyTo // We have to close the result file before updating the modification time.
         fileInfo.LastWriteTimeUtc <- modificationTime
     
\ No newline at end of file