X-Git-Url: http://git.euphorik.ch/?a=blobdiff_plain;f=labo2-fsharp%2FCryptoFile%2FAPI.fs;h=f542f49f0e41b006f702029b0537c4018d327109;hb=c0d86015957eda6badbe9c6e5256807f9ab0c02f;hp=2cf2167a92191d2e2eabc16fd26c60517060c5de;hpb=beda8d83dc421c479bdcf5ee626ec85ee8555a80;p=crypto_lab2.git

diff --git a/labo2-fsharp/CryptoFile/API.fs b/labo2-fsharp/CryptoFile/API.fs
index 2cf2167..f542f49 100644
--- a/labo2-fsharp/CryptoFile/API.fs
+++ b/labo2-fsharp/CryptoFile/API.fs
@@ -1,45 +1,112 @@
 namespace CryptoFile
+
+open System
 open System.IO
 
-type internal Metadata (d : (string * string) list) =
-    new (stream : Stream, size: int) =
-        let binaryReader = new BinaryReader (stream)
-        new Metadata ([])
+// 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
+        Metadata ([for _ in 1..length -> reader.ReadString (), reader.ReadString ()])
+
+    // Write metadata to a stream.
     member this.WriteTo (stream : Stream) =
-        let binaryWriter = new BinaryWriter (stream)
-        List.iter (fun (key : string, value : string) -> binaryWriter.Write key; binaryWriter.Write value) d
+        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 =
+        List.pick (function
+                    | (k, v) when k = key -> Some (v)
+                    | _ -> None) d
 
 module API =
-    let internal filename = "filename"
-    let internal creationTimeKey = "file-creation-time"
+    module internal MetadataKeys =
+        let filename = "filename"
+        let modificationTime = "file-modification-time"
+
+    let internal (@@) a1 a2 = Array.append a1 a2
+
+    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
+    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 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)
 
-        ignore <| writer.Seek (8 + 32 + 256, SeekOrigin.Current) // Skips file-content-size, 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 (Array.append keyAES <| Array.append keyMAC iv) |> writer.Write
+        Crypto.encryptRSA cryptPubKey (keyAES @@ keyMAC @@ iv) |> writer.Write
 
-        printfn "pos: %A" outputStream.Position
+        // Plaintext -> cryptoStream -> hmacStream -> cyphertext.
+        let hmacStream, hmac = Crypto.HMACStream keyMAC outputStream
+        use cryptoStream = Crypto.encryptAES keyAES iv hmacStream
+        use cryptoWriter = new BinaryWriter (cryptoStream)
 
-        use cryptoStream = Crypto.encryptAES keyAES iv outputStream
-        let cryptoWriter = new BinaryWriter (cryptoStream)
+        // Write the file metadata.
+        let metaData = Metadata ([MetadataKeys.filename, fileInfo.Name
+                                  MetadataKeys.modificationTime, fileInfo.LastWriteTimeUtc.Ticks.ToString ()])
+        metaData.WriteTo cryptoStream
 
-        // Write metadata.
-        let metaData = new Metadata ([filename, fileInfo.Name; creationTimeKey, fileInfo.CreationTimeUtc.Ticks.ToString ()])
-        let metaDataStream = new MemoryStream ()
-        metaData.WriteTo metaDataStream
-        cryptoWriter.Write (int metaDataStream.Length)
-        printfn "meta size: %A" (int metaDataStream.Length)
-        metaDataStream.Position <- 0L
-        metaDataStream.CopyTo cryptoStream
-        ()
+        // Write the content of the file.
+        inputStream.CopyTo cryptoStream
+        cryptoStream.FlushFinalBlock ()
 
+        // Write the HMAC at the begining of the file.
+        outputStream.Position <- 0L
+        writer.Write hmac.Hash
+
+        // 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 hmacSize
+        let signature = reader.ReadBytes signatureSize
+        let keys = 
+            try reader.ReadBytes keysSize |> Crypto.decryptRSA decryptPrivKey
+            with 
+                | :? 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
+        if mac' <> mac then
+            raise IntegrityError
+        
+        // Authentication validation.
+        if not <| Crypto.verifySignRSA signaturePubKey mac' signature then
+            raise SignatureMismatch
+
+        // Decrypt metadata.
+        inputStream.Position <- (int64 <| hmacSize + signatureSize + keysSize)
+        use cryptoStream = Crypto.decryptAES keyAES iv inputStream
+        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 ()) cryptoStream.CopyTo // We have to close the result file before updating the modification time.
+        fileInfo.LastWriteTimeUtc <- modificationTime
+    
\ No newline at end of file