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From dc2eaa017fe77e53bd9f1d4327a480d9bfe6cc6a Mon Sep 17 00:00:00 2001
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From: Aris Adamantiadis <aris@0xbadc0de.be>
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Date: Tue, 9 Feb 2016 15:09:27 +0100
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Subject: [PATCH] dh: fix CVE-2016-0739
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Due to a byte/bit confusion, the DH secret was too short. This file was
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completely reworked and will be commited in a future version.
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---
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src/dh.c | 22 +++++++++++++++++-----
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1 file changed, 17 insertions(+), 5 deletions(-)
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diff --git a/src/dh.c b/src/dh.c
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index e489a1d..d27b66e 100644
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--- a/src/dh.c
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+++ b/src/dh.c
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@@ -227,15 +227,21 @@ void ssh_crypto_finalize(void) {
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}
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int dh_generate_x(ssh_session session) {
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+ int keysize;
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+ if (session->next_crypto->kex_type == SSH_KEX_DH_GROUP1_SHA1) {
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+ keysize = 1023;
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+ } else {
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+ keysize = 2047;
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+ }
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session->next_crypto->x = bignum_new();
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if (session->next_crypto->x == NULL) {
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return -1;
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}
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#ifdef HAVE_LIBGCRYPT
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- bignum_rand(session->next_crypto->x, 128);
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+ bignum_rand(session->next_crypto->x, keysize);
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#elif defined HAVE_LIBCRYPTO
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- bignum_rand(session->next_crypto->x, 128, 0, -1);
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+ bignum_rand(session->next_crypto->x, keysize, -1, 0);
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#endif
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/* not harder than this */
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@@ -248,15 +254,21 @@ int dh_generate_x(ssh_session session) {
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/* used by server */
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int dh_generate_y(ssh_session session) {
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- session->next_crypto->y = bignum_new();
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+ int keysize;
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+ if (session->next_crypto->kex_type == SSH_KEX_DH_GROUP1_SHA1) {
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+ keysize = 1023;
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+ } else {
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+ keysize = 2047;
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+ }
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+ session->next_crypto->y = bignum_new();
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if (session->next_crypto->y == NULL) {
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return -1;
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}
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#ifdef HAVE_LIBGCRYPT
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- bignum_rand(session->next_crypto->y, 128);
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+ bignum_rand(session->next_crypto->y, keysize);
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#elif defined HAVE_LIBCRYPTO
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- bignum_rand(session->next_crypto->y, 128, 0, -1);
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+ bignum_rand(session->next_crypto->y, keysize, -1, 0);
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#endif
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/* not harder than this */
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--
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2.7.1
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