X-Git-Url: http://git.euphorik.ch/?a=blobdiff_plain;f=labo2-fsharp%2FCryptoFile%2FAPI.fs;h=250bdbe22786dc140cb8b343961646b51e2cc383;hb=61a8b3492e89e883b23c158eb52ba2b070234df8;hp=e4a70086fc60b1df218c70fc3e7c48ae3bf8bac7;hpb=137157b6dbd5efb99b486a30da6e10b0a175f530;p=crypto_lab2.git

diff --git a/labo2-fsharp/CryptoFile/API.fs b/labo2-fsharp/CryptoFile/API.fs
index e4a7008..250bdbe 100644
--- a/labo2-fsharp/CryptoFile/API.fs
+++ b/labo2-fsharp/CryptoFile/API.fs
@@ -1,26 +1,35 @@
 namespace CryptoFile
+
+open System
 open System.IO
 
+// To read and write metadata.
 type internal Metadata (d: (string * string) list) =
-    new (stream : Stream, size: int) =
-        let binaryReader = new BinaryReader (stream)
-        new Metadata ([])
+    // 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 ()])
 
+    // Write metadata to a stream.
     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
+
+    // May raise 'KeyNotFoundException'.
+    member this.get (key: string) : string =
+        List.pick (function
+                    | (k, v) when k = key -> Some (v)
+                    | _ -> None) d
 
 module API =
-    module internal MetaData =
-        let filename = "filename"
-        let creationTimeKey = "file-creation-time"
+    module internal Metadata =
+        let filenameKey = "filename"
+        let modificationTimeKey = "file-modification-time"
 
     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)
@@ -32,13 +41,14 @@ module API =
 
         Crypto.encryptRSA cryptPubKey (Array.append keyAES <| Array.append 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)
 
         // Write the file metadata.
-        let metaData = new Metadata ([MetaData.filename, fileInfo.Name
-                                      MetaData.creationTimeKey, fileInfo.CreationTimeUtc.Ticks.ToString ()])
+        let metaData = new Metadata ([Metadata.filenameKey, fileInfo.Name
+                                      Metadata.modificationTimeKey, fileInfo.LastWriteTimeUtc.Ticks.ToString ()])
         metaData.WriteTo cryptoStream
 
         // Write the content of the file.
@@ -51,7 +61,38 @@ module API =
 
         // Write the signature.
         Crypto.signRSA signaturePrivKey hmac.Hash |> writer.Write
-        ()
 
     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 = 
+            try reader.ReadBytes 256 |> Crypto.decryptRSA decryptPrivKey
+            with 
+                | :? Security.Cryptography.CryptographicException -> raise UnableToDecryptAESKeys
+        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 its content and metadata.
+        let filePath = Path.Combine (targetDirPath, metadata.get Metadata.filenameKey)
+        let modificationTime = new DateTime (metadata.get Metadata.modificationTimeKey |> int64)
+        let fileInfo = new FileInfo (filePath)
+        using (fileInfo.Create ()) <| fun outputStream -> cryptoStream.CopyTo outputStream
+        fileInfo.LastWriteTimeUtc <- modificationTime
+    
\ No newline at end of file