From 648f14ede2e1b90c0a67d30b2553d853719d9851 Mon Sep 17 00:00:00 2001
From: Arthur Gautier <arthur.gautier@arista.com>
Date: Thu, 4 May 2023 10:36:32 -0700
Subject: [PATCH] ecdsa: Adds support for the `SignatureBitStringEncoding`
 trait

---
 Cargo.lock       |  5 +++--
 ecdsa/Cargo.toml |  3 ++-
 ecdsa/src/der.rs | 13 +++++++++++++
 3 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 447325da..04d5eaf1 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -177,6 +177,7 @@ dependencies = [
  "serdect",
  "sha2",
  "signature",
+ "spki",
 ]
 
 [[package]]
@@ -650,9 +651,9 @@ checksum = "6e63cff320ae2c57904679ba7cb63280a3dc4613885beafb148ee7bf9aa9042d"
 
 [[package]]
 name = "spki"
-version = "0.7.1"
+version = "0.7.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "37a5be806ab6f127c3da44b7378837ebf01dadca8510a0e572460216b228bd0e"
+checksum = "9d1e996ef02c474957d681f1b05213dfb0abab947b446a62d37770b23500184a"
 dependencies = [
  "base64ct",
  "der",
diff --git a/ecdsa/Cargo.toml b/ecdsa/Cargo.toml
index bc4316a9..f70ac3f0 100644
--- a/ecdsa/Cargo.toml
+++ b/ecdsa/Cargo.toml
@@ -25,6 +25,7 @@ digest = { version = "0.10.6", optional = true, default-features = false, featur
 rfc6979 = { version = "0.4", optional = true, path = "../rfc6979" }
 serdect = { version = "0.2", optional = true, default-features = false, features = ["alloc"] }
 sha2 = { version = "0.10", optional = true, default-features = false, features = ["oid"] }
+spki = { version = "0.7.2", optional = true, default-features = false }
 
 [dev-dependencies]
 elliptic-curve = { version = "0.13", default-features = false, features = ["dev"] }
@@ -33,7 +34,7 @@ sha2 = { version = "0.10", default-features = false }
 
 [features]
 default = ["digest"]
-alloc = ["elliptic-curve/alloc", "signature/alloc"]
+alloc = ["elliptic-curve/alloc", "signature/alloc", "spki/alloc"]
 std = ["alloc", "elliptic-curve/std", "signature/std"]
 
 arithmetic = ["elliptic-curve/arithmetic"]
diff --git a/ecdsa/src/der.rs b/ecdsa/src/der.rs
index 5395dff6..b4b03c17 100644
--- a/ecdsa/src/der.rs
+++ b/ecdsa/src/der.rs
@@ -19,6 +19,7 @@ use elliptic_curve::{
 use {
     alloc::{boxed::Box, vec::Vec},
     signature::SignatureEncoding,
+    spki::{der::asn1::BitString, SignatureBitStringEncoding},
 };
 
 #[cfg(feature = "serde")]
@@ -309,6 +310,18 @@ where
     }
 }
 
+#[cfg(feature = "alloc")]
+impl<C> SignatureBitStringEncoding for Signature<C>
+where
+    C: PrimeCurve,
+    MaxSize<C>: ArrayLength<u8>,
+    <FieldBytesSize<C> as Add>::Output: Add<MaxOverhead> + ArrayLength<u8>,
+{
+    fn to_bitstring(&self) -> der::Result<BitString> {
+        BitString::new(0, self.to_vec())
+    }
+}
+
 #[cfg(feature = "serde")]
 impl<C> Serialize for Signature<C>
 where