1 files changed, 118 insertions, 0 deletions
diff --git a/vendor/signature/src/signer.rs b/vendor/signature/src/signer.rs
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+//! Traits for generating digital signatures
+
+use crate::error::Error;
+
+#[cfg(feature = "digest")]
+use crate::digest::Digest;
+
+#[cfg(feature = "rand_core")]
+use crate::rand_core::CryptoRngCore;
+
+/// Sign the provided message bytestring using `Self` (e.g. a cryptographic key
+/// or connection to an HSM), returning a digital signature.
+pub trait Signer<S> {
+    /// Sign the given message and return a digital signature
+    fn sign(&self, msg: &[u8]) -> S {
+        self.try_sign(msg).expect("signature operation failed")
+    }
+
+    /// Attempt to sign the given message, returning a digital signature on
+    /// success, or an error if something went wrong.
+    ///
+    /// 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(&self, msg: &[u8]) -> Result<S, Error>;
+}
+
+/// Sign the provided message bytestring using `&mut Self` (e.g. an evolving
+/// cryptographic key such as a stateful hash-based signature), returning a
+/// digital signature.
+pub trait SignerMut<S> {
+    /// Sign the given message, update the state, and return a digital signature.
+    fn sign(&mut self, msg: &[u8]) -> S {
+        self.try_sign(msg).expect("signature operation failed")
+    }
+
+    /// Attempt to sign the given message, updating the state, and returning a
+    /// digital signature on success, or an error if something went wrong.
+    ///
+    /// Signing can fail, e.g., if the number of time periods allowed by the
+    /// current key is exceeded.
+    fn try_sign(&mut self, msg: &[u8]) -> Result<S, Error>;
+}
+
+/// Blanket impl of [`SignerMut`] for all [`Signer`] types.
+impl<S, T: Signer<S>> SignerMut<S> for T {
+    fn try_sign(&mut self, msg: &[u8]) -> Result<S, Error> {
+        T::try_sign(self, msg)
+    }
+}
+
+/// Sign the given prehashed message [`Digest`] using `Self`.
+///
+/// ## Notes
+///
+/// This trait is primarily intended for signature algorithms based on the
+/// [Fiat-Shamir heuristic], a method for converting an interactive
+/// challenge/response-based proof-of-knowledge protocol into an offline
+/// digital signature through the use of a random oracle, i.e. a digest
+/// function.
+///
+/// The security of such protocols critically rests upon the inability of
+/// an attacker to solve for the output of the random oracle, as generally
+/// otherwise such signature algorithms are a system of linear equations and
+/// therefore doing so would allow the attacker to trivially forge signatures.
+///
+/// To prevent misuse which would potentially allow this to be possible, this
+/// API accepts a [`Digest`] instance, rather than a raw digest value.
+///
+/// [Fiat-Shamir heuristic]: https://en.wikipedia.org/wiki/Fiat%E2%80%93Shamir_heuristic
+#[cfg(feature = "digest")]
+pub trait DigestSigner<D: Digest, S> {
+    /// Sign the given prehashed message [`Digest`], returning a signature.
+    ///
+    /// Panics in the event of a signing error.
+    fn sign_digest(&self, digest: D) -> S {
+        self.try_sign_digest(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(&self, digest: D) -> Result<S, Error>;
+}
+
+/// Sign the given message using the provided external randomness source.
+#[cfg(feature = "rand_core")]
+pub trait RandomizedSigner<S> {
+    /// Sign the given message and return a digital signature
+    fn sign_with_rng(&self, rng: &mut impl CryptoRngCore, msg: &[u8]) -> S {
+        self.try_sign_with_rng(rng, msg)
+            .expect("signature operation failed")
+    }
+
+    /// Attempt to sign the given message, returning a digital signature on
+    /// success, or an error if something went wrong.
+    ///
+    /// 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(&self, rng: &mut impl CryptoRngCore, msg: &[u8]) -> Result<S, Error>;
+}
+
+/// Combination of [`DigestSigner`] and [`RandomizedSigner`] with support for
+/// computing a signature over a digest which requires entropy from an RNG.
+#[cfg(all(feature = "digest", feature = "rand_core"))]
+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(&self, rng: &mut impl CryptoRngCore, 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(&self, rng: &mut impl CryptoRngCore, digest: D)
+        -> Result<S, Error>;
+}