aead-stream: move the remaining items from aead (#647)

This PR follows removal of the items from `aead` in
RustCrypto/traits#1713

In a future PR I plan to refactor `aead-stream` further, so it's
convenient to have all code in one place.

aead-stream/Cargo.toml

@@ -13,7 +13,7 @@ categories = ["cryptography", "no-std"]
 rust-version = "1.81"
 
 [dependencies]
-aead = { version = "=0.6.0-rc.0", default-features = false, features = ["stream"] }
+aead = { version = "=0.6.0-rc.0", default-features = false }
 
 [features]
 alloc = ["aead/alloc"]

aead-stream/src/lib.rs

@@ -5,19 +5,21 @@
 #[cfg(feature = "alloc")]
 extern crate alloc;
 
-use aead::array::{
-    typenum::{Unsigned, U4, U5},
-    Array, ArraySize,
+use aead::{
+    array::{
+        typenum::{Unsigned, U4, U5},
+        Array, ArraySize,
+    },
+    AeadCore, AeadInPlace, Buffer, Error, Result,
 };
-use aead::{AeadCore, AeadInPlace, Buffer, Error, Result};
-use core::ops::Sub;
+use core::ops::{AddAssign, Sub};
 
 pub use aead;
 
-pub use aead::{
-    stream::{Decryptor, Encryptor, NewStream, StreamPrimitive},
-    Key, KeyInit,
-};
+pub use aead::{Key, KeyInit};
+
+#[cfg(feature = "alloc")]
+use {aead::Payload, alloc::vec::Vec};
 
 /// Nonce as used by a given AEAD construction and STREAM primitive.
 pub type Nonce<A, S> = Array<u8, NonceSize<A, S>>;
@@ -27,6 +29,295 @@ pub type Nonce<A, S> = Array<u8, NonceSize<A, S>>;
 pub type NonceSize<A, S> =
     <<A as AeadCore>::NonceSize as Sub<<S as StreamPrimitive<A>>::NonceOverhead>>::Output;
 
+/// Create a new STREAM from the provided AEAD.
+pub trait NewStream<A>: StreamPrimitive<A>
+where
+    A: AeadInPlace,
+    A::NonceSize: Sub<Self::NonceOverhead>,
+    NonceSize<A, Self>: ArraySize,
+{
+    /// Create a new STREAM with the given key and nonce.
+    fn new(key: &Key<A>, nonce: &Nonce<A, Self>) -> Self
+    where
+        A: KeyInit,
+        Self: Sized,
+    {
+        Self::from_aead(A::new(key), nonce)
+    }
+
+    /// Create a new STREAM from the given AEAD cipher.
+    fn from_aead(aead: A, nonce: &Nonce<A, Self>) -> Self;
+}
+
+/// Low-level STREAM implementation.
+///
+/// This trait provides a particular "flavor" of STREAM, as there are
+/// different ways the specifics of the construction can be implemented.
+///
+/// Deliberately immutable and stateless to permit parallel operation.
+pub trait StreamPrimitive<A>
+where
+    A: AeadInPlace,
+    A::NonceSize: Sub<Self::NonceOverhead>,
+    NonceSize<A, Self>: ArraySize,
+{
+    /// Number of bytes this STREAM primitive requires from the nonce.
+    type NonceOverhead: ArraySize;
+
+    /// Type used as the STREAM counter.
+    type Counter: AddAssign + Copy + Default + Eq;
+
+    /// Value to use when incrementing the STREAM counter (i.e. one)
+    const COUNTER_INCR: Self::Counter;
+
+    /// Maximum value of the STREAM counter.
+    const COUNTER_MAX: Self::Counter;
+
+    /// Encrypt an AEAD message in-place at the given position in the STREAM.
+    fn encrypt_in_place(
+        &self,
+        position: Self::Counter,
+        last_block: bool,
+        associated_data: &[u8],
+        buffer: &mut dyn Buffer,
+    ) -> Result<()>;
+
+    /// Decrypt an AEAD message in-place at the given position in the STREAM.
+    fn decrypt_in_place(
+        &self,
+        position: Self::Counter,
+        last_block: bool,
+        associated_data: &[u8],
+        buffer: &mut dyn Buffer,
+    ) -> Result<()>;
+
+    /// Encrypt the given plaintext payload, and return the resulting
+    /// ciphertext as a vector of bytes.
+    #[cfg(feature = "alloc")]
+    fn encrypt<'msg, 'aad>(
+        &self,
+        position: Self::Counter,
+        last_block: bool,
+        plaintext: impl Into<Payload<'msg, 'aad>>,
+    ) -> Result<Vec<u8>> {
+        let payload = plaintext.into();
+        let mut buffer = Vec::with_capacity(payload.msg.len() + A::TagSize::to_usize());
+        buffer.extend_from_slice(payload.msg);
+        self.encrypt_in_place(position, last_block, payload.aad, &mut buffer)?;
+        Ok(buffer)
+    }
+
+    /// Decrypt the given ciphertext slice, and return the resulting plaintext
+    /// as a vector of bytes.
+    #[cfg(feature = "alloc")]
+    fn decrypt<'msg, 'aad>(
+        &self,
+        position: Self::Counter,
+        last_block: bool,
+        ciphertext: impl Into<Payload<'msg, 'aad>>,
+    ) -> Result<Vec<u8>> {
+        let payload = ciphertext.into();
+        let mut buffer = Vec::from(payload.msg);
+        self.decrypt_in_place(position, last_block, payload.aad, &mut buffer)?;
+        Ok(buffer)
+    }
+
+    /// Obtain [`Encryptor`] for this [`StreamPrimitive`].
+    fn encryptor(self) -> Encryptor<A, Self>
+    where
+        Self: Sized,
+    {
+        Encryptor::from_stream_primitive(self)
+    }
+
+    /// Obtain [`Decryptor`] for this [`StreamPrimitive`].
+    fn decryptor(self) -> Decryptor<A, Self>
+    where
+        Self: Sized,
+    {
+        Decryptor::from_stream_primitive(self)
+    }
+}
+
+/// Implement a stateful STREAM object (i.e. encryptor or decryptor)
+macro_rules! impl_stream_object {
+    (
+        $name:ident,
+        $next_method:tt,
+        $next_in_place_method:tt,
+        $last_method:tt,
+        $last_in_place_method:tt,
+        $op:tt,
+        $in_place_op:tt,
+        $op_desc:expr,
+        $obj_desc:expr
+    ) => {
+        #[doc = "Stateful STREAM object which can"]
+        #[doc = $op_desc]
+        #[doc = "AEAD messages one-at-a-time."]
+        #[doc = ""]
+        #[doc = "This corresponds to the "]
+        #[doc = $obj_desc]
+        #[doc = "object as defined in the paper"]
+        #[doc = "[Online Authenticated-Encryption and its Nonce-Reuse Misuse-Resistance][1]."]
+        #[doc = ""]
+        #[doc = "[1]: https://eprint.iacr.org/2015/189.pdf"]
+        #[derive(Debug)]
+        pub struct $name<A, S>
+        where
+            A: AeadInPlace,
+            S: StreamPrimitive<A>,
+            A::NonceSize: Sub<<S as StreamPrimitive<A>>::NonceOverhead>,
+            NonceSize<A, S>: ArraySize,
+        {
+            /// Underlying STREAM primitive.
+            stream: S,
+
+            /// Current position in the STREAM.
+            position: S::Counter,
+        }
+
+        impl<A, S> $name<A, S>
+        where
+            A: AeadInPlace,
+            S: StreamPrimitive<A>,
+            A::NonceSize: Sub<<S as StreamPrimitive<A>>::NonceOverhead>,
+            NonceSize<A, S>: ArraySize,
+        {
+            #[doc = "Create a"]
+            #[doc = $obj_desc]
+            #[doc = "object from the given AEAD key and nonce."]
+            pub fn new(key: &Key<A>, nonce: &Nonce<A, S>) -> Self
+            where
+                A: KeyInit,
+                S: NewStream<A>,
+            {
+                Self::from_stream_primitive(S::new(key, nonce))
+            }
+
+            #[doc = "Create a"]
+            #[doc = $obj_desc]
+            #[doc = "object from the given AEAD primitive."]
+            pub fn from_aead(aead: A, nonce: &Nonce<A, S>) -> Self
+            where
+                A: KeyInit,
+                S: NewStream<A>,
+            {
+                Self::from_stream_primitive(S::from_aead(aead, nonce))
+            }
+
+            #[doc = "Create a"]
+            #[doc = $obj_desc]
+            #[doc = "object from the given STREAM primitive."]
+            pub fn from_stream_primitive(stream: S) -> Self {
+                Self {
+                    stream,
+                    position: Default::default(),
+                }
+            }
+
+            #[doc = "Use the underlying AEAD to"]
+            #[doc = $op_desc]
+            #[doc = "the next AEAD message in this STREAM, returning the"]
+            #[doc = "result as a [`Vec`]."]
+            #[cfg(feature = "alloc")]
+            pub fn $next_method<'msg, 'aad>(
+                &mut self,
+                payload: impl Into<Payload<'msg, 'aad>>,
+            ) -> Result<Vec<u8>> {
+                if self.position == S::COUNTER_MAX {
+                    // Counter overflow. Note that the maximum counter value is
+                    // deliberately disallowed, as it would preclude being able
+                    // to encrypt a last block (i.e. with `$last_in_place_method`)
+                    return Err(Error);
+                }
+
+                let result = self.stream.$op(self.position, false, payload)?;
+
+                // Note: overflow checked above
+                self.position += S::COUNTER_INCR;
+                Ok(result)
+            }
+
+            #[doc = "Use the underlying AEAD to"]
+            #[doc = $op_desc]
+            #[doc = "the next AEAD message in this STREAM in-place."]
+            pub fn $next_in_place_method(
+                &mut self,
+                associated_data: &[u8],
+                buffer: &mut dyn Buffer,
+            ) -> Result<()> {
+                if self.position == S::COUNTER_MAX {
+                    // Counter overflow. Note that the maximum counter value is
+                    // deliberately disallowed, as it would preclude being able
+                    // to encrypt a last block (i.e. with `$last_in_place_method`)
+                    return Err(Error);
+                }
+
+                self.stream
+                    .$in_place_op(self.position, false, associated_data, buffer)?;
+
+                // Note: overflow checked above
+                self.position += S::COUNTER_INCR;
+                Ok(())
+            }
+
+            #[doc = "Use the underlying AEAD to"]
+            #[doc = $op_desc]
+            #[doc = "the last AEAD message in this STREAM,"]
+            #[doc = "consuming the "]
+            #[doc = $obj_desc]
+            #[doc = "object in order to prevent further use."]
+            #[cfg(feature = "alloc")]
+            pub fn $last_method<'msg, 'aad>(
+                self,
+                payload: impl Into<Payload<'msg, 'aad>>,
+            ) -> Result<Vec<u8>> {
+                self.stream.$op(self.position, true, payload)
+            }
+
+            #[doc = "Use the underlying AEAD to"]
+            #[doc = $op_desc]
+            #[doc = "the last AEAD message in this STREAM in-place,"]
+            #[doc = "consuming the "]
+            #[doc = $obj_desc]
+            #[doc = "object in order to prevent further use."]
+            pub fn $last_in_place_method(
+                self,
+                associated_data: &[u8],
+                buffer: &mut dyn Buffer,
+            ) -> Result<()> {
+                self.stream
+                    .$in_place_op(self.position, true, associated_data, buffer)
+            }
+        }
+    };
+}
+
+impl_stream_object!(
+    Encryptor,
+    encrypt_next,
+    encrypt_next_in_place,
+    encrypt_last,
+    encrypt_last_in_place,
+    encrypt,
+    encrypt_in_place,
+    "encrypt",
+    "ℰ STREAM encryptor"
+);
+
+impl_stream_object!(
+    Decryptor,
+    decrypt_next,
+    decrypt_next_in_place,
+    decrypt_last,
+    decrypt_last_in_place,
+    decrypt,
+    decrypt_in_place,
+    "decrypt",
+    "𝒟 STREAM decryptor"
+);
+
 /// STREAM encryptor instantiated with [`StreamBE32`] as the underlying
 /// STREAM primitive.
 pub type EncryptorBE32<A> = Encryptor<A, StreamBE32<A>>;