Let implementations choose the tag length

crates/api-desc/CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Patch
 
+- Add `crypto::gcm::tag_length()` function
 - Use `*const u8` instead of `*mut u8` for opaque data
 
 ## 0.1.3

crates/api-desc/src/crypto/gcm.rs

@@ -42,6 +42,12 @@ pub(crate) fn new() -> Item {
                 support: usize,
             }
         },
+        item! {
+            /// Returns the supported tag length.
+            ///
+            /// The tag argument to [`encrypt()`] and [`decrypt()`] must be of that length.
+            fn tag_length "cgt" {} -> { len: usize }
+        },
         item! {
             /// Encrypts and authenticates a clear text with associated data given a key and IV.
             fn encrypt "cge" {
@@ -69,7 +75,7 @@ pub(crate) fn new() -> Item {
                 /// The cipher text.
                 cipher: *mut u8,
 
-                /// The 16 bytes authentication tag.
+                /// The authentication tag (see [`super::tag_length()`]).
                 tag: *mut u8,
             } -> {
                 /// Zero on success, bitwise complement of [`Error`](crate::crypto::Error)
@@ -92,7 +98,7 @@ pub(crate) fn new() -> Item {
                 /// The length of the additional authenticated data.
                 aad_len: usize,
 
-                /// The 16 bytes authentication tag.
+                /// The authentication tag (see [`super::tag_length()`]).
                 tag: *const u8,
 
                 /// The length of the cipher (and clear) text.

crates/board/CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Major
 
+- Make the tag length configurable for `crypto::aead::Api`
 - Change crypto API to mention `Keysize`, `BlockSize`, and `OutputSize`
 
 ### Minor
@@ -59,4 +60,4 @@
 
 ## 0.1.0
 
-<!-- Increment to skip CHANGELOG.md test: 8 -->
+<!-- Increment to skip CHANGELOG.md test: 9 -->

crates/board/src/crypto.rs

@@ -26,8 +26,8 @@ pub mod ecc;
 
 /// Cryptography interface.
 pub trait Api {
-    type Aes128Ccm: aead::Api<U16, U13, U4>;
-    type Aes256Gcm: aead::Api<U32, U12, U16>;
+    type Aes128Ccm: aead::Api<U16, U13, Tag = U4>;
+    type Aes256Gcm: aead::Api<U32, U12>;
 
     type HmacSha256: Support<bool> + Hmac<KeySize = U64, OutputSize = U32>;
     type HmacSha384: Support<bool> + Hmac<KeySize = U128, OutputSize = U48>;
@@ -45,12 +45,12 @@ pub trait Hmac: KeyInit + Update + FixedOutput + MacMarker {}
 impl<T: Default + BlockSizeUser + Update + FixedOutputReset + HashMarker> Hash for T {}
 impl<T: KeyInit + Update + FixedOutput + MacMarker> Hmac for T {}
 
-pub struct UnsupportedHash<Block: ArrayLength<u8> + 'static, Output: ArrayLength<u8> + 'static> {
+pub struct UnsupportedHash<Block: ArrayLength<u8>, Output: ArrayLength<u8>> {
     _never: !,
     _block: Block,
     _output: Output,
 }
-pub struct UnsupportedHmac<Key: ArrayLength<u8> + 'static, Output: ArrayLength<u8> + 'static> {
+pub struct UnsupportedHmac<Key: ArrayLength<u8>, Output: ArrayLength<u8>> {
     _never: !,
     _key: Key,
     _output: Output,
@@ -79,11 +79,11 @@ macro_rules! software {
 impl<T: Api> Api for UnsupportedCrypto<T> {
     software! {
         #[cfg(feature = "software-crypto-aes128-ccm")]
-        type Aes128Ccm = ccm::Ccm<aes::Aes128, U4, U13> | Unsupported;
+        type Aes128Ccm = ccm::Ccm<aes::Aes128, U4, U13> | aead::Unsupported<U4>;
     }
     software! {
         #[cfg(feature = "software-crypto-aes256-gcm")]
-        type Aes256Gcm = aes_gcm::Aes256Gcm | Unsupported;
+        type Aes256Gcm = aes_gcm::Aes256Gcm | aead::Unsupported<U16>;
     }
 
     software! {
@@ -127,31 +127,31 @@ impl Api for Unsupported {
 
 impl<B, O> BlockSizeUser for UnsupportedHash<B, O>
 where
-    B: ArrayLength<u8> + 'static,
-    O: ArrayLength<u8> + 'static,
+    B: ArrayLength<u8>,
+    O: ArrayLength<u8>,
 {
     type BlockSize = B;
 }
 
 impl<B, O> OutputSizeUser for UnsupportedHash<B, O>
 where
-    B: ArrayLength<u8> + 'static,
-    O: ArrayLength<u8> + 'static,
+    B: ArrayLength<u8>,
+    O: ArrayLength<u8>,
 {
     type OutputSize = O;
 }
 
 impl<B, O> HashMarker for UnsupportedHash<B, O>
 where
-    B: ArrayLength<u8> + 'static,
-    O: ArrayLength<u8> + 'static,
+    B: ArrayLength<u8>,
+    O: ArrayLength<u8>,
 {
 }
 
 impl<B, O> Default for UnsupportedHash<B, O>
 where
-    B: ArrayLength<u8> + 'static,
-    O: ArrayLength<u8> + 'static,
+    B: ArrayLength<u8>,
+    O: ArrayLength<u8>,
 {
     fn default() -> Self {
         unreachable!()
@@ -160,8 +160,8 @@ where
 
 impl<B, O> Update for UnsupportedHash<B, O>
 where
-    B: ArrayLength<u8> + 'static,
-    O: ArrayLength<u8> + 'static,
+    B: ArrayLength<u8>,
+    O: ArrayLength<u8>,
 {
     fn update(&mut self, _: &[u8]) {
         unreachable!()
@@ -170,8 +170,8 @@ where
 
 impl<B, O> FixedOutput for UnsupportedHash<B, O>
 where
-    B: ArrayLength<u8> + 'static,
-    O: ArrayLength<u8> + 'static,
+    B: ArrayLength<u8>,
+    O: ArrayLength<u8>,
 {
     fn finalize_into(self, _: &mut Output<Self>) {
         unreachable!()
@@ -180,8 +180,8 @@ where
 
 impl<B, O> FixedOutputReset for UnsupportedHash<B, O>
 where
-    B: ArrayLength<u8> + 'static,
-    O: ArrayLength<u8> + 'static,
+    B: ArrayLength<u8>,
+    O: ArrayLength<u8>,
 {
     fn finalize_into_reset(&mut self, _: &mut Output<Self>) {
         unreachable!()
@@ -190,8 +190,8 @@ where
 
 impl<B, O> Reset for UnsupportedHash<B, O>
 where
-    B: ArrayLength<u8> + 'static,
-    O: ArrayLength<u8> + 'static,
+    B: ArrayLength<u8>,
+    O: ArrayLength<u8>,
 {
     fn reset(&mut self) {
         unreachable!()
@@ -200,39 +200,39 @@ where
 
 impl<B, O> Support<bool> for UnsupportedHash<B, O>
 where
-    B: ArrayLength<u8> + 'static,
-    O: ArrayLength<u8> + 'static,
+    B: ArrayLength<u8>,
+    O: ArrayLength<u8>,
 {
     const SUPPORT: bool = false;
 }
 
 impl<K, O> KeySizeUser for UnsupportedHmac<K, O>
 where
-    K: ArrayLength<u8> + 'static,
-    O: ArrayLength<u8> + 'static,
+    K: ArrayLength<u8>,
+    O: ArrayLength<u8>,
 {
     type KeySize = K;
 }
 
 impl<K, O> OutputSizeUser for UnsupportedHmac<K, O>
 where
-    K: ArrayLength<u8> + 'static,
-    O: ArrayLength<u8> + 'static,
+    K: ArrayLength<u8>,
+    O: ArrayLength<u8>,
 {
     type OutputSize = O;
 }
 
 impl<K, O> MacMarker for UnsupportedHmac<K, O>
 where
-    K: ArrayLength<u8> + 'static,
-    O: ArrayLength<u8> + 'static,
+    K: ArrayLength<u8>,
+    O: ArrayLength<u8>,
 {
 }
 
 impl<K, O> KeyInit for UnsupportedHmac<K, O>
 where
-    K: ArrayLength<u8> + 'static,
-    O: ArrayLength<u8> + 'static,
+    K: ArrayLength<u8>,
+    O: ArrayLength<u8>,
 {
     fn new(_: &Key<Self>) -> Self {
         unreachable!()
@@ -241,8 +241,8 @@ where
 
 impl<K, O> Update for UnsupportedHmac<K, O>
 where
-    K: ArrayLength<u8> + 'static,
-    O: ArrayLength<u8> + 'static,
+    K: ArrayLength<u8>,
+    O: ArrayLength<u8>,
 {
     fn update(&mut self, _: &[u8]) {
         unreachable!()
@@ -251,8 +251,8 @@ where
 
 impl<K, O> FixedOutput for UnsupportedHmac<K, O>
 where
-    K: ArrayLength<u8> + 'static,
-    O: ArrayLength<u8> + 'static,
+    K: ArrayLength<u8>,
+    O: ArrayLength<u8>,
 {
     fn finalize_into(self, _: &mut Output<Self>) {
         unreachable!()
@@ -261,8 +261,8 @@ where
 
 impl<K, O> Support<bool> for UnsupportedHmac<K, O>
 where
-    K: ArrayLength<u8> + 'static,
-    O: ArrayLength<u8> + 'static,
+    K: ArrayLength<u8>,
+    O: ArrayLength<u8>,
 {
     const SUPPORT: bool = false;
 }

crates/board/src/crypto/aead.rs

@@ -18,7 +18,7 @@ use generic_array::{ArrayLength, GenericArray};
 #[cfg(feature = "internal-aead")]
 pub use software::*;
 
-use crate::{Error, Support, Unsupported};
+use crate::{Error, Support};
 
 #[derive(Copy, Clone)]
 pub struct AeadSupport {
@@ -33,51 +33,61 @@ impl From<AeadSupport> for bool {
 }
 
 /// Elliptic-curve cryptography interface.
-pub trait Api<Key, Iv, Tag>: Support<AeadSupport>
+pub trait Api<Key, Iv>: Support<AeadSupport>
 where
     Key: ArrayLength<u8>,
     Iv: ArrayLength<u8>,
-    Tag: ArrayLength<u8>,
 {
+    /// The tag length.
+    type Tag: ArrayLength<u8>;
+
     /// Encrypts and authenticates a clear text with associated data given a key and IV.
     ///
     /// The clear- and cipher-texts must have the same length. If the clear text is omitted, then
     /// the cipher text is encrypted in place.
     fn encrypt(
         key: &Array<Key>, iv: &Array<Iv>, aad: &[u8], clear: Option<&[u8]>, cipher: &mut [u8],
-        tag: &mut Array<Tag>,
+        tag: &mut Array<Self::Tag>,
     ) -> Result<(), Error>;
 
     /// Decrypts and authenticates a cipher text with associated data given a key and IV.
     ///
     /// The cipher- and clear-texts must have the same length. If the cipher text is omitted, then
     /// the clear text is decrypted in place.
     fn decrypt(
-        key: &Array<Key>, iv: &Array<Iv>, aad: &[u8], cipher: Option<&[u8]>, tag: &Array<Tag>,
-        clear: &mut [u8],
+        key: &Array<Key>, iv: &Array<Iv>, aad: &[u8], cipher: Option<&[u8]>,
+        tag: &Array<Self::Tag>, clear: &mut [u8],
     ) -> Result<(), Error>;
 }
 
 pub type Array<N> = GenericArray<u8, N>;
 
-impl Support<AeadSupport> for Unsupported {
+pub struct Unsupported<Tag: ArrayLength<u8>> {
+    _never: !,
+    _tag: Tag,
+}
+
+impl<Tag: ArrayLength<u8>> Support<AeadSupport> for Unsupported<Tag> {
     const SUPPORT: AeadSupport = AeadSupport { no_copy: false, in_place_no_copy: false };
 }
 
-impl<Key, Iv, Tag> Api<Key, Iv, Tag> for Unsupported
+impl<Key, Iv, Tag: ArrayLength<u8>> Api<Key, Iv> for Unsupported<Tag>
 where
     Key: ArrayLength<u8>,
     Iv: ArrayLength<u8>,
-    Tag: ArrayLength<u8>,
 {
+    type Tag = Tag;
+
     fn encrypt(
-        _: &Array<Key>, _: &Array<Iv>, _: &[u8], _: Option<&[u8]>, _: &mut [u8], _: &mut Array<Tag>,
+        _: &Array<Key>, _: &Array<Iv>, _: &[u8], _: Option<&[u8]>, _: &mut [u8],
+        _: &mut Array<Self::Tag>,
     ) -> Result<(), Error> {
         unreachable!()
     }
 
     fn decrypt(
-        _: &Array<Key>, _: &Array<Iv>, _: &[u8], _: Option<&[u8]>, _: &Array<Tag>, _: &mut [u8],
+        _: &Array<Key>, _: &Array<Iv>, _: &[u8], _: Option<&[u8]>, _: &Array<Self::Tag>,
+        _: &mut [u8],
     ) -> Result<(), Error> {
         unreachable!()
     }
@@ -94,18 +104,19 @@ mod software {
         const SUPPORT: AeadSupport = AeadSupport { no_copy: false, in_place_no_copy: true };
     }
 
-    impl<Key, Iv, Tag, T> Api<Key, Iv, Tag> for T
+    impl<Key, Iv, T> Api<Key, Iv> for T
     where
         T: KeyInit + AeadInPlace,
         T: KeySizeUser<KeySize = Key>,
-        T: AeadCore<NonceSize = Iv, TagSize = Tag>,
+        T: AeadCore<NonceSize = Iv>,
         Key: ArrayLength<u8>,
         Iv: ArrayLength<u8>,
-        Tag: ArrayLength<u8>,
     {
+        type Tag = T::TagSize;
+
         fn encrypt(
             key: &Array<Key>, iv: &Array<Iv>, aad: &[u8], clear: Option<&[u8]>, cipher: &mut [u8],
-            tag: &mut Array<Tag>,
+            tag: &mut Array<Self::Tag>,
         ) -> Result<(), Error> {
             let aead = T::new(key);
             if let Some(clear) = clear {
@@ -118,8 +129,8 @@ mod software {
         }
 
         fn decrypt(
-            key: &Array<Key>, iv: &Array<Iv>, aad: &[u8], cipher: Option<&[u8]>, tag: &Array<Tag>,
-            clear: &mut [u8],
+            key: &Array<Key>, iv: &Array<Iv>, aad: &[u8], cipher: Option<&[u8]>,
+            tag: &Array<Self::Tag>, clear: &mut [u8],
         ) -> Result<(), Error> {
             let aead = T::new(key);
             if let Some(cipher) = cipher {

crates/prelude/CHANGELOG.md

@@ -1,6 +1,10 @@
 # Changelog
 
-## 0.2.1-git
+## 0.3.0-git
+
+### Major
+
+- Make the AES256-GCM tag variable length
 
 ### Minor