| <!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/openssl-0.10.54/src/memcmp.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>memcmp.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../normalize.css"><link rel="stylesheet" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../ayu.css" disabled><link rel="stylesheet" href="../../dark.css" disabled><link rel="stylesheet" href="../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../storage.js"></script><script defer src="../../source-script.js"></script><script defer src="../../source-files.js"></script><script defer src="../../main.js"></script><noscript><link rel="stylesheet" href="../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../favicon.svg"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../openssl/index.html"><div class="logo-container"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../openssl/index.html"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
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| </pre><pre class="rust"><code><span class="doccomment">//! 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)); |
| //! ``` |
| </span><span class="kw">use </span>libc::size_t; |
| <span class="kw">use </span>openssl_macros::corresponds; |
| |
| <span class="doccomment">/// 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)); |
| /// ``` |
| </span><span class="attribute">#[corresponds(CRYPTO_memcmp)] |
| </span><span class="kw">pub fn </span>eq(a: <span class="kw-2">&</span>[u8], b: <span class="kw-2">&</span>[u8]) -> bool { |
| <span class="macro">assert!</span>(a.len() == b.len()); |
| <span class="kw">let </span>ret = <span class="kw">unsafe </span>{ |
| ffi::CRYPTO_memcmp( |
| a.as_ptr() <span class="kw">as </span><span class="kw-2">*const </span><span class="kw">_</span>, |
| b.as_ptr() <span class="kw">as </span><span class="kw-2">*const </span><span class="kw">_</span>, |
| a.len() <span class="kw">as </span>size_t, |
| ) |
| }; |
| ret == <span class="number">0 |
| </span>} |
| |
| <span class="attribute">#[cfg(test)] |
| </span><span class="kw">mod </span>tests { |
| <span class="kw">use </span><span class="kw">super</span>::eq; |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>test_eq() { |
| <span class="macro">assert!</span>(eq(<span class="kw-2">&</span>[], <span class="kw-2">&</span>[])); |
| <span class="macro">assert!</span>(eq(<span class="kw-2">&</span>[<span class="number">1</span>], <span class="kw-2">&</span>[<span class="number">1</span>])); |
| <span class="macro">assert!</span>(!eq(<span class="kw-2">&</span>[<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>], <span class="kw-2">&</span>[<span class="number">1</span>, <span class="number">2</span>, <span class="number">4</span>])); |
| } |
| |
| <span class="attribute">#[test] |
| #[should_panic] |
| </span><span class="kw">fn </span>test_diff_lens() { |
| eq(<span class="kw-2">&</span>[], <span class="kw-2">&</span>[<span class="number">1</span>]); |
| } |
| } |
| </code></pre></div> |
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