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 =
| (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.
// 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
// 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