signature: relax Sized requirements on rng (#1765)

signature/src/signer.rs

@@ -86,7 +86,7 @@ pub trait DigestSigner<D: Digest, S> {
 #[cfg(feature = "rand_core")]
 pub trait RandomizedSigner<S> {
     /// Sign the given message and return a digital signature
-    fn sign_with_rng<R: CryptoRng>(&self, rng: &mut R, msg: &[u8]) -> S {
+    fn sign_with_rng<R: CryptoRng + ?Sized>(&self, rng: &mut R, msg: &[u8]) -> S {
         self.try_sign_with_rng(rng, msg)
             .expect("signature operation failed")
     }
@@ -96,7 +96,11 @@ pub trait RandomizedSigner<S> {
     ///
     /// The main intended use case for signing errors is when communicating
     /// with external signers, e.g. cloud KMS, HSMs, or other hardware tokens.
-    fn try_sign_with_rng<R: TryCryptoRng>(&self, rng: &mut R, msg: &[u8]) -> Result<S, Error>;
+    fn try_sign_with_rng<R: TryCryptoRng + ?Sized>(
+        &self,
+        rng: &mut R,
+        msg: &[u8],
+    ) -> Result<S, Error>;
 }
 
 /// Combination of [`DigestSigner`] and [`RandomizedSigner`] with support for
@@ -106,15 +110,18 @@ pub trait RandomizedDigestSigner<D: Digest, S> {
     /// Sign the given prehashed message `Digest`, returning a signature.
     ///
     /// Panics in the event of a signing error.
-    fn sign_digest_with_rng<R: CryptoRng>(&self, rng: &mut R, digest: D) -> S {
+    fn sign_digest_with_rng<R: CryptoRng + ?Sized>(&self, rng: &mut R, digest: D) -> S {
         self.try_sign_digest_with_rng(rng, digest)
             .expect("signature operation failed")
     }
 
     /// Attempt to sign the given prehashed message `Digest`, returning a
     /// digital signature on success, or an error if something went wrong.
-    fn try_sign_digest_with_rng<R: TryCryptoRng>(&self, rng: &mut R, digest: D)
-    -> Result<S, Error>;
+    fn try_sign_digest_with_rng<R: TryCryptoRng + ?Sized>(
+        &self,
+        rng: &mut R,
+        digest: D,
+    ) -> Result<S, Error>;
 }
 
 /// Sign the provided message bytestring using `&mut Self` (e.g. an evolving
@@ -123,7 +130,7 @@ pub trait RandomizedDigestSigner<D: Digest, S> {
 #[cfg(feature = "rand_core")]
 pub trait RandomizedSignerMut<S> {
     /// Sign the given message, update the state, and return a digital signature.
-    fn sign_with_rng<R: CryptoRng>(&mut self, rng: &mut R, msg: &[u8]) -> S {
+    fn sign_with_rng<R: CryptoRng + ?Sized>(&mut self, rng: &mut R, msg: &[u8]) -> S {
         self.try_sign_with_rng(rng, msg)
             .expect("signature operation failed")
     }
@@ -133,13 +140,21 @@ pub trait RandomizedSignerMut<S> {
     ///
     /// Signing can fail, e.g., if the number of time periods allowed by the
     /// current key is exceeded.
-    fn try_sign_with_rng<R: TryCryptoRng>(&mut self, rng: &mut R, msg: &[u8]) -> Result<S, Error>;
+    fn try_sign_with_rng<R: TryCryptoRng + ?Sized>(
+        &mut self,
+        rng: &mut R,
+        msg: &[u8],
+    ) -> Result<S, Error>;
 }
 
 /// Blanket impl of [`RandomizedSignerMut`] for all [`RandomizedSigner`] types.
 #[cfg(feature = "rand_core")]
 impl<S, T: RandomizedSigner<S>> RandomizedSignerMut<S> for T {
-    fn try_sign_with_rng<R: TryCryptoRng>(&mut self, rng: &mut R, msg: &[u8]) -> Result<S, Error> {
+    fn try_sign_with_rng<R: TryCryptoRng + ?Sized>(
+        &mut self,
+        rng: &mut R,
+        msg: &[u8],
+    ) -> Result<S, Error> {
         T::try_sign_with_rng(self, rng, msg)
     }
 }