1 files changed, 43 insertions, 0 deletions
diff --git a/vendor/spki/src/fingerprint.rs b/vendor/spki/src/fingerprint.rs
new file mode 100644
index 000000000..6a3901fb1
--- /dev/null
+++ b/vendor/spki/src/fingerprint.rs
@@ -0,0 +1,43 @@
+//! SPKI fingerprint support.
+
+use der::Writer;
+use sha2::{Digest, Sha256};
+
+/// Size of a SHA-256 SPKI fingerprint in bytes.
+pub(crate) const SIZE: usize = 32;
+
+/// Raw bytes of a SPKI fingerprint i.e. SHA-256 digest of
+/// `SubjectPublicKeyInfo`'s DER encoding.
+///
+/// See [RFC7469 § 2.1.1] for more information.
+///
+/// [RFC7469 § 2.1.1]: https://datatracker.ietf.org/doc/html/rfc7469#section-2.1.1
+#[cfg_attr(docsrs, doc(cfg(feature = "fingerprint")))]
+pub type FingerprintBytes = [u8; SIZE];
+
+/// Writer newtype which accepts DER being serialized on-the-fly and computes a
+/// hash of the contents.
+#[derive(Clone, Default)]
+pub(crate) struct Builder {
+    /// In-progress digest being computed from streaming DER.
+    digest: Sha256,
+}
+
+impl Builder {
+    /// Create a new fingerprint builder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Finish computing a fingerprint, returning the computed digest.
+    pub fn finish(self) -> FingerprintBytes {
+        self.digest.finalize().into()
+    }
+}
+
+impl Writer for Builder {
+    fn write(&mut self, der_bytes: &[u8]) -> der::Result<()> {
+        self.digest.update(der_bytes);
+        Ok(())
+    }
+}