salsa20: add expose-core feature

salsa20/Cargo.toml

@@ -19,9 +19,10 @@ cipher = { version = "0.2", features = ["dev"] }
 
 [features]
 default = ["xsalsa20"]
+expose-core = []
 hsalsa20 = ["xsalsa20"]
 xsalsa20 = []
 
 [package.metadata.docs.rs]
-all-features = true
+features = ["hsalsa20", "xsalsa20"]
 rustdoc-args = ["--cfg", "docsrs"]

salsa20/src/block.rs

@@ -8,7 +8,7 @@ use core::{convert::TryInto, marker::PhantomData, mem};
 /// While Salsa20 is a stream cipher, not a block cipher, its core
 /// primitive is a function which acts on a 512-bit block
 // TODO(tarcieri): zeroize? need to make sure we're actually copying first
-pub(crate) struct Block<R: Rounds> {
+pub struct Block<R: Rounds> {
     /// Internal state of the block function
     state: [u32; STATE_WORDS],
 
@@ -18,7 +18,7 @@ pub(crate) struct Block<R: Rounds> {
 
 impl<R: Rounds> Block<R> {
     /// Initialize block function with the given key and IV
-    pub(crate) fn new(key: &Key, iv: &Nonce) -> Self {
+    pub fn new(key: &Key, iv: &Nonce) -> Self {
         #[allow(unsafe_code)]
         let mut state: [u32; STATE_WORDS] = unsafe { mem::zeroed() };
         state[0] = CONSTANTS[0];
@@ -50,9 +50,8 @@ impl<R: Rounds> Block<R> {
     }
 
     /// Generate output, overwriting data already in the buffer
-    pub(crate) fn generate(&mut self, counter: u64, output: &mut [u8]) {
+    pub fn generate(&mut self, output: &mut [u8]) {
         debug_assert_eq!(output.len(), BLOCK_SIZE);
-        self.counter_setup(counter);
 
         let mut state = self.state;
         self.rounds(&mut state);
@@ -63,7 +62,7 @@ impl<R: Rounds> Block<R> {
     }
 
     /// Apply generated keystream to the output buffer
-    pub(crate) fn apply_keystream(&mut self, counter: u64, output: &mut [u8]) {
+    pub fn apply_keystream(&mut self, counter: u64, output: &mut [u8]) {
         debug_assert_eq!(output.len(), BLOCK_SIZE);
         self.counter_setup(counter);
 
@@ -78,7 +77,7 @@ impl<R: Rounds> Block<R> {
     }
 
     #[inline]
-    fn counter_setup(&mut self, counter: u64) {
+    pub(crate) fn counter_setup(&mut self, counter: u64) {
         self.state[8] = (counter & 0xffff_ffff) as u32;
         self.state[9] = ((counter >> 32) & 0xffff_ffff) as u32;
     }
@@ -106,6 +105,15 @@ impl<R: Rounds> Block<R> {
     }
 }
 
+impl<R: Rounds> From<[u32; STATE_WORDS]> for Block<R> {
+    fn from(state: [u32; STATE_WORDS]) -> Block<R> {
+        Self {
+            state,
+            rounds: PhantomData,
+        }
+    }
+}
+
 #[inline]
 #[allow(clippy::many_single_char_names)]
 pub(crate) fn quarter_round(

salsa20/src/lib.rs

@@ -66,12 +66,18 @@ mod xsalsa;
 
 pub use crate::salsa::{Key, Nonce, Salsa, Salsa12, Salsa20, Salsa8};
 
-#[cfg(feature = "xsalsa20")]
-pub use crate::xsalsa::{XNonce, XSalsa20};
+#[cfg(feature = "expose-core")]
+pub use crate::{
+    block::Block,
+    rounds::{R12, R20, R8},
+};
 
 #[cfg(feature = "hsalsa20")]
 pub use crate::xsalsa::hsalsa20;
 
+#[cfg(feature = "xsalsa20")]
+pub use crate::xsalsa::{XNonce, XSalsa20};
+
 /// Size of a Salsa20 block in bytes
 pub const BLOCK_SIZE: usize = 64;
 

salsa20/src/salsa.rs

@@ -116,7 +116,8 @@ impl<R: Rounds> SyncStreamCipher for Salsa<R> {
         self.buffer_pos = rem.len() as u8;
         self.counter = counter;
         if !rem.is_empty() {
-            self.block.generate(counter, &mut self.buffer);
+            self.block.counter_setup(counter);
+            self.block.generate(&mut self.buffer);
             xor(rem, &self.buffer[..rem.len()]);
         }
 
@@ -134,7 +135,8 @@ impl<R: Rounds> SyncStreamCipherSeek for Salsa<R> {
         self.counter = res.0;
         self.buffer_pos = res.1;
         if self.buffer_pos != 0 {
-            self.block.generate(self.counter, &mut self.buffer);
+            self.block.counter_setup(self.counter);
+            self.block.generate(&mut self.buffer);
         }
         Ok(())
     }