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From f21b9f7b21067fa3630607cdc1663141b2735ae5 Mon Sep 17 00:00:00 2001
From: Armin Kuster <akuster@mvista.com>
Date: Thu, 2 Mar 2017 12:24:31 +0000
Subject: [PATCH] Create meta-gplv2 from files from OE-Core

Upstream-Status: Backport
https://git.lysator.liu.se/nettle/nettle/commit/c71d2c9d20eeebb985e3872e4550137209e3ce4d

CVE: CVE-2015-8803
CVE: CVE-2015-8805

Same fix for both.

Signed-off-by: Armin Kuster <akuster@mvista.com>

---
 ChangeLog |  6 ++++++
 ecc-256.c | 23 ++++++++++++++++++-----
 2 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 7b7854d..abdd974 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2015-12-10  Niels Möller  <nisse@lysator.liu.se>
+
+   * ecc-256.c (ecc_256_modp): Fixed carry propagation bug. Problem
+   reported by Hanno Böck.
+   (ecc_256_modq): Fixed another carry propagation bug.
+
 2013-05-28  Niels Möller  <nisse@lysator.liu.se>
 
 	* Released nettle-2.7.1.
diff --git a/ecc-256.c b/ecc-256.c
index 571cf73..7bee4c7 100644
--- a/ecc-256.c
+++ b/ecc-256.c
@@ -96,9 +96,19 @@ ecc_256_modp (const struct ecc_curve *ecc, mp_limb_t *rp)
       q2 += t + (q1 < t);
 
       assert (q2 < 2);
-
-      /* We multiply by two low limbs of p, 2^96 - 1, so we could use
-	 shifts rather than mul. */
+      /*
+   n-1 n-2 n-3 n-4
+        +---+---+---+---+
+        | u1| u0| u low |
+        +---+---+---+---+
+          - | q1(2^96-1)|
+            +-------+---+
+            |q2(2^.)|
+            +-------+
+
+   We multiply by two low limbs of p, 2^96 - 1, so we could use
+   shifts rather than mul.
+      */
       t = mpn_submul_1 (rp + n - 4, ecc->p, 2, q1);
       t += cnd_sub_n (q2, rp + n - 3, ecc->p, 1);
       t += (-q2) & 0xffffffff;
@@ -108,7 +118,10 @@ ecc_256_modp (const struct ecc_curve *ecc, mp_limb_t *rp)
       u0 -= t;
       t = (u1 < cy);
       u1 -= cy;
-      u1 += cnd_add_n (t, rp + n - 4, ecc->p, 3);
+
+      cy = cnd_add_n (t, rp + n - 4, ecc->p, 2);
+      u0 += cy;
+      u1 += (u0 < cy);
       u1 -= (-t) & 0xffffffff;
     }
   rp[2] = u0;
@@ -195,7 +208,7 @@ ecc_256_modq (const struct ecc_curve *ecc, mp_limb_t *rp)
 
       /* Conditional add of p */
       u1 += t;
-      u2 += (t<<32) + (u0 < t);
+      u2 += (t<<32) + (u1 < t);
 
       t = cnd_add_n (t, rp + n - 4, ecc->q, 2);
       u1 += t;