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)
let internal (@@) a1 a2 = Array.append a1 a2
- let generatKeysPair : Key * Key = Crypto.generateRSAKeysPair
+ 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)
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
// 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
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 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
+ 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