nettle/nettle-3.7-chacha-counter-ppc64.patch

From 64837b2e433e2b99b893683949bad3a99acab38f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Niels=20M=C3=B6ller?= <nisse@lysator.liu.se>
Date: Wed, 10 Feb 2021 11:22:23 +0100
Subject: [PATCH] Fix chacha counter update for _4core variants.

---
 ChangeLog      |  4 ++++
 chacha-crypt.c | 10 +++++++---
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/chacha-crypt.c b/chacha-crypt.c
index 081ebcf4..1fdfc813 100644
--- a/chacha-crypt.c
+++ b/chacha-crypt.c
@@ -80,13 +80,16 @@ _nettle_chacha_crypt_4core(struct chacha_ctx *ctx,
   while (length > 2*CHACHA_BLOCK_SIZE)
     {
       _nettle_chacha_4core (x, ctx->state, CHACHA_ROUNDS);
-      ctx->state[12] += 4;
-      ctx->state[13] += (ctx->state[12] < 4);
       if (length <= 4*CHACHA_BLOCK_SIZE)
 	{
+	  uint32_t incr = 3 + (length > 3*CHACHA_BLOCK_SIZE);
+	  ctx->state[12] += incr;
+	  ctx->state[13] += (ctx->state[12] < incr);
 	  memxor3 (dst, src, x, length);
 	  return;
 	}
+      ctx->state[12] += 4;
+      ctx->state[13] += (ctx->state[12] < 4);
       memxor3 (dst, src, x, 4*CHACHA_BLOCK_SIZE);
 
       length -= 4*CHACHA_BLOCK_SIZE;
@@ -200,12 +203,13 @@ _nettle_chacha_crypt32_4core(struct chacha_ctx *ctx,
   while (length > 2*CHACHA_BLOCK_SIZE)
     {
       _nettle_chacha_4core32 (x, ctx->state, CHACHA_ROUNDS);
-      ctx->state[12] += 4;
       if (length <= 4*CHACHA_BLOCK_SIZE)
 	{
+	  ctx->state[12] += 3 + (length > 3*CHACHA_BLOCK_SIZE);
 	  memxor3 (dst, src, x, length);
 	  return;
 	}
+      ctx->state[12] += 4;
       memxor3 (dst, src, x, 4*CHACHA_BLOCK_SIZE);
 
       length -= 4*CHACHA_BLOCK_SIZE;
-- 
2.29.2