Create new librespot-audio crate

audio/src/decrypt.rs

@@ -0,0 +1,57 @@
+use crypto::aes;
+use crypto::symmetriccipher::SynchronousStreamCipher;
+use num_bigint::BigUint;
+use num_traits::FromPrimitive;
+use std::io;
+use std::ops::Add;
+
+use core::audio_key::AudioKey;
+
+const AUDIO_AESIV: &'static [u8] = &[0x72, 0xe0, 0x67, 0xfb, 0xdd, 0xcb, 0xcf, 0x77, 0xeb, 0xe8,
+                                     0xbc, 0x64, 0x3f, 0x63, 0x0d, 0x93];
+
+pub struct AudioDecrypt<T: io::Read> {
+    cipher: Box<SynchronousStreamCipher + 'static>,
+    key: AudioKey,
+    reader: T,
+}
+
+impl<T: io::Read> AudioDecrypt<T> {
+    pub fn new(key: AudioKey, reader: T) -> AudioDecrypt<T> {
+        let cipher = aes::ctr(aes::KeySize::KeySize128, &key.0, AUDIO_AESIV);
+        AudioDecrypt {
+            cipher: cipher,
+            key: key,
+            reader: reader,
+        }
+    }
+}
+
+impl<T: io::Read> io::Read for AudioDecrypt<T> {
+    fn read(&mut self, output: &mut [u8]) -> io::Result<usize> {
+        let mut buffer = vec![0u8; output.len()];
+        let len = try!(self.reader.read(&mut buffer));
+
+        self.cipher.process(&buffer[..len], &mut output[..len]);
+
+        Ok(len)
+    }
+}
+
+impl<T: io::Read + io::Seek> io::Seek for AudioDecrypt<T> {
+    fn seek(&mut self, pos: io::SeekFrom) -> io::Result<u64> {
+        let newpos = try!(self.reader.seek(pos));
+        let skip = newpos % 16;
+
+        let iv = BigUint::from_bytes_be(AUDIO_AESIV)
+                     .add(BigUint::from_u64(newpos / 16).unwrap())
+                     .to_bytes_be();
+        self.cipher = aes::ctr(aes::KeySize::KeySize128, &self.key.0, &iv);
+
+        let buf = vec![0u8; skip as usize];
+        let mut buf2 = vec![0u8; skip as usize];
+        self.cipher.process(&buf, &mut buf2);
+
+        Ok(newpos as u64)
+    }
+}