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diff --git a/vendor/openssl/src/memcmp.rs b/vendor/openssl/src/memcmp.rs
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+//! Utilities to safely compare cryptographic values.
+//!
+//! Extra care must be taken when comparing values in
+//! cryptographic code. If done incorrectly, it can lead
+//! to a [timing attack](https://en.wikipedia.org/wiki/Timing_attack).
+//! By analyzing the time taken to execute parts of a cryptographic
+//! algorithm, and attacker can attempt to compromise the
+//! cryptosystem.
+//!
+//! The utilities in this module are designed to be resistant
+//! to this type of attack.
+//!
+//! # Examples
+//!
+//! To perform a constant-time comparison of two arrays of the same length but different
+//! values:
+//!
+//! ```
+//! use openssl::memcmp::eq;
+//!
+//! // We want to compare `a` to `b` and `c`, without giving
+//! // away through timing analysis that `c` is more similar to `a`
+//! // than `b`.
+//! let a = [0, 0, 0];
+//! let b = [1, 1, 1];
+//! let c = [0, 0, 1];
+//!
+//! // These statements will execute in the same amount of time.
+//! assert!(!eq(&a, &b));
+//! assert!(!eq(&a, &c));
+//! ```
+use libc::size_t;
+use openssl_macros::corresponds;
+
+/// Returns `true` iff `a` and `b` contain the same bytes.
+///
+/// This operation takes an amount of time dependent on the length of the two
+/// arrays given, but is independent of the contents of a and b.
+///
+/// # Panics
+///
+/// This function will panic the current task if `a` and `b` do not have the same
+/// length.
+///
+/// # Examples
+///
+/// To perform a constant-time comparison of two arrays of the same length but different
+/// values:
+///
+/// ```
+/// use openssl::memcmp::eq;
+///
+/// // We want to compare `a` to `b` and `c`, without giving
+/// // away through timing analysis that `c` is more similar to `a`
+/// // than `b`.
+/// let a = [0, 0, 0];
+/// let b = [1, 1, 1];
+/// let c = [0, 0, 1];
+///
+/// // These statements will execute in the same amount of time.
+/// assert!(!eq(&a, &b));
+/// assert!(!eq(&a, &c));
+/// ```
+#[corresponds(CRYPTO_memcmp)]
+pub fn eq(a: &[u8], b: &[u8]) -> bool {
+    assert!(a.len() == b.len());
+    let ret = unsafe {
+        ffi::CRYPTO_memcmp(
+            a.as_ptr() as *const _,
+            b.as_ptr() as *const _,
+            a.len() as size_t,
+        )
+    };
+    ret == 0
+}
+
+#[cfg(test)]
+mod tests {
+    use super::eq;
+
+    #[test]
+    fn test_eq() {
+        assert!(eq(&[], &[]));
+        assert!(eq(&[1], &[1]));
+        assert!(!eq(&[1, 2, 3], &[1, 2, 4]));
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_diff_lens() {
+        eq(&[], &[1]);
+    }
+}