| <!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/ring-0.16.20/src/aead/gcm/gcm_nohw.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>gcm_nohw.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="../../../../ring/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="../../../../ring/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="comment">// Copyright (c) 2019, Google Inc. |
| // Portions Copyright 2020 Brian Smith. |
| // |
| // Permission to use, copy, modify, and/or distribute this software for any |
| // purpose with or without fee is hereby granted, provided that the above |
| // copyright notice and this permission notice appear in all copies. |
| // |
| // THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES |
| // WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF |
| // MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY |
| // SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES |
| // WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION |
| // OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN |
| // CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. |
| |
| // This file is based on BoringSSL's gcm_nohw.c. |
| |
| // This file contains a constant-time implementation of GHASH based on the notes |
| // in https://bearssl.org/constanttime.html#ghash-for-gcm and the reduction |
| // algorithm described in |
| // https://crypto.stanford.edu/RealWorldCrypto/slides/gueron.pdf. |
| // |
| // Unlike the BearSSL notes, we use u128 in the 64-bit implementation. |
| |
| </span><span class="kw">use super</span>::{<span class="kw">super</span>::Block, Xi}; |
| <span class="kw">use </span><span class="kw">crate</span>::endian::BigEndian; |
| <span class="kw">use </span>core::convert::TryInto; |
| |
| <span class="attribute">#[cfg(target_pointer_width = <span class="string">"64"</span>)] |
| </span><span class="kw">fn </span>gcm_mul64_nohw(a: u64, b: u64) -> (u64, u64) { |
| <span class="attribute">#[inline(always)] |
| </span><span class="kw">fn </span>lo(a: u128) -> u64 { |
| a <span class="kw">as </span>u64 |
| } |
| |
| <span class="attribute">#[inline(always)] |
| </span><span class="kw">fn </span>hi(a: u128) -> u64 { |
| lo(a >> <span class="number">64</span>) |
| } |
| |
| <span class="attribute">#[inline(always)] |
| </span><span class="kw">fn </span>mul(a: u64, b: u64) -> u128 { |
| u128::from(a) * u128::from(b) |
| } |
| |
| <span class="comment">// One term every four bits means the largest term is 64/4 = 16, which barely |
| // overflows into the next term. Using one term every five bits would cost 25 |
| // multiplications instead of 16. It is faster to mask off the bottom four |
| // bits of |a|, giving a largest term of 60/4 = 15, and apply the bottom bits |
| // separately. |
| </span><span class="kw">let </span>a0 = a & <span class="number">0x1111111111111110</span>; |
| <span class="kw">let </span>a1 = a & <span class="number">0x2222222222222220</span>; |
| <span class="kw">let </span>a2 = a & <span class="number">0x4444444444444440</span>; |
| <span class="kw">let </span>a3 = a & <span class="number">0x8888888888888880</span>; |
| |
| <span class="kw">let </span>b0 = b & <span class="number">0x1111111111111111</span>; |
| <span class="kw">let </span>b1 = b & <span class="number">0x2222222222222222</span>; |
| <span class="kw">let </span>b2 = b & <span class="number">0x4444444444444444</span>; |
| <span class="kw">let </span>b3 = b & <span class="number">0x8888888888888888</span>; |
| |
| <span class="kw">let </span>c0 = mul(a0, b0) ^ mul(a1, b3) ^ mul(a2, b2) ^ mul(a3, b1); |
| <span class="kw">let </span>c1 = mul(a0, b1) ^ mul(a1, b0) ^ mul(a2, b3) ^ mul(a3, b2); |
| <span class="kw">let </span>c2 = mul(a0, b2) ^ mul(a1, b1) ^ mul(a2, b0) ^ mul(a3, b3); |
| <span class="kw">let </span>c3 = mul(a0, b3) ^ mul(a1, b2) ^ mul(a2, b1) ^ mul(a3, b0); |
| |
| <span class="comment">// Multiply the bottom four bits of |a| with |b|. |
| </span><span class="kw">let </span>a0_mask = <span class="number">0u64</span>.wrapping_sub(a & <span class="number">1</span>); |
| <span class="kw">let </span>a1_mask = <span class="number">0u64</span>.wrapping_sub((a >> <span class="number">1</span>) & <span class="number">1</span>); |
| <span class="kw">let </span>a2_mask = <span class="number">0u64</span>.wrapping_sub((a >> <span class="number">2</span>) & <span class="number">1</span>); |
| <span class="kw">let </span>a3_mask = <span class="number">0u64</span>.wrapping_sub((a >> <span class="number">3</span>) & <span class="number">1</span>); |
| <span class="kw">let </span>extra = u128::from(a0_mask & b) |
| ^ (u128::from(a1_mask & b) << <span class="number">1</span>) |
| ^ (u128::from(a2_mask & b) << <span class="number">2</span>) |
| ^ (u128::from(a3_mask & b) << <span class="number">3</span>); |
| |
| <span class="kw">let </span>lo = (lo(c0) & <span class="number">0x1111111111111111</span>) |
| ^ (lo(c1) & <span class="number">0x2222222222222222</span>) |
| ^ (lo(c2) & <span class="number">0x4444444444444444</span>) |
| ^ (lo(c3) & <span class="number">0x8888888888888888</span>) |
| ^ lo(extra); |
| <span class="kw">let </span>hi = (hi(c0) & <span class="number">0x1111111111111111</span>) |
| ^ (hi(c1) & <span class="number">0x2222222222222222</span>) |
| ^ (hi(c2) & <span class="number">0x4444444444444444</span>) |
| ^ (hi(c3) & <span class="number">0x8888888888888888</span>) |
| ^ hi(extra); |
| (lo, hi) |
| } |
| |
| <span class="attribute">#[cfg(not(target_pointer_width = <span class="string">"64"</span>))] |
| </span><span class="kw">fn </span>gcm_mul32_nohw(a: u32, b: u32) -> u64 { |
| <span class="attribute">#[inline(always)] |
| </span><span class="kw">fn </span>mul(a: u32, b: u32) -> u64 { |
| u64::from(a) * u64::from(b) |
| } |
| |
| <span class="comment">// One term every four bits means the largest term is 32/4 = 8, which does not |
| // overflow into the next term. |
| </span><span class="kw">let </span>a0 = a & <span class="number">0x11111111</span>; |
| <span class="kw">let </span>a1 = a & <span class="number">0x22222222</span>; |
| <span class="kw">let </span>a2 = a & <span class="number">0x44444444</span>; |
| <span class="kw">let </span>a3 = a & <span class="number">0x88888888</span>; |
| |
| <span class="kw">let </span>b0 = b & <span class="number">0x11111111</span>; |
| <span class="kw">let </span>b1 = b & <span class="number">0x22222222</span>; |
| <span class="kw">let </span>b2 = b & <span class="number">0x44444444</span>; |
| <span class="kw">let </span>b3 = b & <span class="number">0x88888888</span>; |
| |
| <span class="kw">let </span>c0 = mul(a0, b0) ^ mul(a1, b3) ^ mul(a2, b2) ^ mul(a3, b1); |
| <span class="kw">let </span>c1 = mul(a0, b1) ^ mul(a1, b0) ^ mul(a2, b3) ^ mul(a3, b2); |
| <span class="kw">let </span>c2 = mul(a0, b2) ^ mul(a1, b1) ^ mul(a2, b0) ^ mul(a3, b3); |
| <span class="kw">let </span>c3 = mul(a0, b3) ^ mul(a1, b2) ^ mul(a2, b1) ^ mul(a3, b0); |
| |
| (c0 & <span class="number">0x1111111111111111</span>) |
| | (c1 & <span class="number">0x2222222222222222</span>) |
| | (c2 & <span class="number">0x4444444444444444</span>) |
| | (c3 & <span class="number">0x8888888888888888</span>) |
| } |
| |
| <span class="attribute">#[cfg(not(target_pointer_width = <span class="string">"64"</span>))] |
| </span><span class="kw">fn </span>gcm_mul64_nohw(a: u64, b: u64) -> (u64, u64) { |
| <span class="attribute">#[inline(always)] |
| </span><span class="kw">fn </span>lo(a: u64) -> u32 { |
| a <span class="kw">as </span>u32 |
| } |
| <span class="attribute">#[inline(always)] |
| </span><span class="kw">fn </span>hi(a: u64) -> u32 { |
| lo(a >> <span class="number">32</span>) |
| } |
| |
| <span class="kw">let </span>a0 = lo(a); |
| <span class="kw">let </span>a1 = hi(a); |
| <span class="kw">let </span>b0 = lo(b); |
| <span class="kw">let </span>b1 = hi(b); |
| <span class="comment">// Karatsuba multiplication. |
| </span><span class="kw">let </span>lo = gcm_mul32_nohw(a0, b0); |
| <span class="kw">let </span>hi = gcm_mul32_nohw(a1, b1); |
| <span class="kw">let </span>mid = gcm_mul32_nohw(a0 ^ a1, b0 ^ b1) ^ lo ^ hi; |
| (lo ^ (mid << <span class="number">32</span>), hi ^ (mid >> <span class="number">32</span>)) |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>init(xi: [u64; <span class="number">2</span>]) -> <span class="kw">super</span>::u128 { |
| <span class="comment">// We implement GHASH in terms of POLYVAL, as described in RFC8452. This |
| // avoids a shift by 1 in the multiplication, needed to account for bit |
| // reversal losing a bit after multiplication, that is, |
| // rev128(X) * rev128(Y) = rev255(X*Y). |
| // |
| // Per Appendix A, we run mulX_POLYVAL. Note this is the same transformation |
| // applied by |gcm_init_clmul|, etc. Note |Xi| has already been byteswapped. |
| // |
| // See also slide 16 of |
| // https://crypto.stanford.edu/RealWorldCrypto/slides/gueron.pdf |
| </span><span class="kw">let </span><span class="kw-2">mut </span>lo = xi[<span class="number">1</span>]; |
| <span class="kw">let </span><span class="kw-2">mut </span>hi = xi[<span class="number">0</span>]; |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>carry = hi >> <span class="number">63</span>; |
| carry = <span class="number">0u64</span>.wrapping_sub(carry); |
| |
| hi <<= <span class="number">1</span>; |
| hi |= lo >> <span class="number">63</span>; |
| lo <<= <span class="number">1</span>; |
| |
| <span class="comment">// The irreducible polynomial is 1 + x^121 + x^126 + x^127 + x^128, so we |
| // conditionally add 0xc200...0001. |
| </span>lo ^= carry & <span class="number">1</span>; |
| hi ^= carry & <span class="number">0xc200000000000000</span>; |
| |
| <span class="comment">// This implementation does not use the rest of |Htable|. |
| </span><span class="kw">super</span>::u128 { lo, hi } |
| } |
| |
| <span class="kw">fn </span>gcm_polyval_nohw(xi: <span class="kw-2">&mut </span>[u64; <span class="number">2</span>], h: <span class="kw">super</span>::u128) { |
| <span class="comment">// Karatsuba multiplication. The product of |Xi| and |H| is stored in |r0| |
| // through |r3|. Note there is no byte or bit reversal because we are |
| // evaluating POLYVAL. |
| </span><span class="kw">let </span>(r0, <span class="kw-2">mut </span>r1) = gcm_mul64_nohw(xi[<span class="number">0</span>], h.lo); |
| <span class="kw">let </span>(<span class="kw-2">mut </span>r2, <span class="kw-2">mut </span>r3) = gcm_mul64_nohw(xi[<span class="number">1</span>], h.hi); |
| <span class="kw">let </span>(<span class="kw-2">mut </span>mid0, <span class="kw-2">mut </span>mid1) = gcm_mul64_nohw(xi[<span class="number">0</span>] ^ xi[<span class="number">1</span>], h.hi ^ h.lo); |
| mid0 ^= r0 ^ r2; |
| mid1 ^= r1 ^ r3; |
| r2 ^= mid1; |
| r1 ^= mid0; |
| |
| <span class="comment">// Now we multiply our 256-bit result by x^-128 and reduce. |r2| and |
| // |r3| shifts into position and we must multiply |r0| and |r1| by x^-128. We |
| // have: |
| // |
| // 1 = x^121 + x^126 + x^127 + x^128 |
| // x^-128 = x^-7 + x^-2 + x^-1 + 1 |
| // |
| // This is the GHASH reduction step, but with bits flowing in reverse. |
| |
| // The x^-7, x^-2, and x^-1 terms shift bits past x^0, which would require |
| // another reduction steps. Instead, we gather the excess bits, incorporate |
| // them into |r0| and |r1| and reduce once. See slides 17-19 |
| // of https://crypto.stanford.edu/RealWorldCrypto/slides/gueron.pdf. |
| </span>r1 ^= (r0 << <span class="number">63</span>) ^ (r0 << <span class="number">62</span>) ^ (r0 << <span class="number">57</span>); |
| |
| <span class="comment">// 1 |
| </span>r2 ^= r0; |
| r3 ^= r1; |
| |
| <span class="comment">// x^-1 |
| </span>r2 ^= r0 >> <span class="number">1</span>; |
| r2 ^= r1 << <span class="number">63</span>; |
| r3 ^= r1 >> <span class="number">1</span>; |
| |
| <span class="comment">// x^-2 |
| </span>r2 ^= r0 >> <span class="number">2</span>; |
| r2 ^= r1 << <span class="number">62</span>; |
| r3 ^= r1 >> <span class="number">2</span>; |
| |
| <span class="comment">// x^-7 |
| </span>r2 ^= r0 >> <span class="number">7</span>; |
| r2 ^= r1 << <span class="number">57</span>; |
| r3 ^= r1 >> <span class="number">7</span>; |
| |
| <span class="kw-2">*</span>xi = [r2, r3]; |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>gmult(xi: <span class="kw-2">&mut </span>Xi, h: <span class="kw">super</span>::u128) { |
| with_swapped_xi(xi, |swapped| { |
| gcm_polyval_nohw(swapped, h); |
| }) |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>ghash(xi: <span class="kw-2">&mut </span>Xi, h: <span class="kw">super</span>::u128, input: <span class="kw-2">&</span>[u8]) { |
| with_swapped_xi(xi, |swapped| { |
| input.chunks_exact(<span class="number">16</span>).for_each(|inp| { |
| swapped[<span class="number">0</span>] ^= u64::from_be_bytes(inp[<span class="number">8</span>..].try_into().unwrap()); |
| swapped[<span class="number">1</span>] ^= u64::from_be_bytes(inp[..<span class="number">8</span>].try_into().unwrap()); |
| gcm_polyval_nohw(swapped, h); |
| }); |
| }); |
| } |
| |
| <span class="attribute">#[inline] |
| </span><span class="kw">fn </span>with_swapped_xi(Xi(xi): <span class="kw-2">&mut </span>Xi, f: <span class="kw">impl </span>FnOnce(<span class="kw-2">&mut </span>[u64; <span class="number">2</span>])) { |
| <span class="kw">let </span>unswapped = xi.u64s_be_to_native(); |
| <span class="kw">let </span><span class="kw-2">mut </span>swapped: [u64; <span class="number">2</span>] = [unswapped[<span class="number">1</span>], unswapped[<span class="number">0</span>]]; |
| f(<span class="kw-2">&mut </span>swapped); |
| <span class="kw-2">*</span>xi = Block::from_u64_be(BigEndian::from(swapped[<span class="number">1</span>]), BigEndian::from(swapped[<span class="number">0</span>])) |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../../" data-current-crate="ring" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
