libgcrypt: fix CVE-2017-9526

In libgcrypt before 1.7.7, an attacker who learns the EdDSA session key (from
side-channel observation during the signing process) can easily recover the
long-term secret key. 1.7.7 makes a cipher/ecc-eddsa.c change to store this
session key in secure memory, to ensure that constant-time point operations are
used in the MPI library.

(From OE-Core rev: 6039dbfd981830b5406c25a27ccfae0e5ed016e8)

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-support/libgcrypt/files/0001-ecc-Store-EdDSA-session-key-in-secure-memory.patch

@@ -0,0 +1,39 @@
+CVE: CVE-2017-9526
+Upstream-Status: Backport
+Signed-off-by: Ross Burton <ross.burton@intel.com>
+
+From 4a1768d683f6572ad86d833508c70e6b3dc1efdc Mon Sep 17 00:00:00 2001
+From: Jo Van Bulck <jo.vanbulck@cs.kuleuven.be>
+Date: Thu, 19 Jan 2017 17:00:15 +0100
+Subject: [PATCH] ecc: Store EdDSA session key in secure memory.
+
+* cipher/ecc-eddsa.c (_gcry_ecc_eddsa_sign): use mpi_snew to allocate
+session key.
+--
+
+An attacker who learns the EdDSA session key from side-channel
+observation during the signing process, can easily revover the long-
+term secret key. Storing the session key in secure memory ensures that
+constant time point operations are used in the MPI library.
+
+Signed-off-by: Jo Van Bulck <jo.vanbulck@cs.kuleuven.be>
+---
+ cipher/ecc-eddsa.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/cipher/ecc-eddsa.c b/cipher/ecc-eddsa.c
+index f91f8489..813e030d 100644
+--- a/cipher/ecc-eddsa.c
++++ b/cipher/ecc-eddsa.c
+@@ -603,7 +603,7 @@ _gcry_ecc_eddsa_sign (gcry_mpi_t input, ECC_secret_key *skey,
+   a = mpi_snew (0);
+   x = mpi_new (0);
+   y = mpi_new (0);
+-  r = mpi_new (0);
++  r = mpi_snew (0);
+   ctx = _gcry_mpi_ec_p_internal_new (skey->E.model, skey->E.dialect, 0,
+                                      skey->E.p, skey->E.a, skey->E.b);
+   b = (ctx->nbits+7)/8;
+-- 
+2.11.0
+

meta/recipes-support/libgcrypt/libgcrypt.inc

@@ -20,6 +20,7 @@ SRC_URI = "${GNUPG_MIRROR}/libgcrypt/libgcrypt-${PV}.tar.gz \
            file://libgcrypt-fix-building-error-with-O2-in-sysroot-path.patch \
            file://fix-ICE-failure-on-mips-with-option-O-and-g.patch \
            file://fix-undefined-reference-to-pthread.patch \
+           file://0001-ecc-Store-EdDSA-session-key-in-secure-memory.patch \
 "
 
 BINCONFIG = "${bindir}/libgcrypt-config"