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dh: Fix CVE-2016-0739

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Due to a byte/bit confusion, the DH secret was too short. This file was
completely reworked and will be commited in a future version.

Signed-off-by: Aris Adamantiadis <aris@0xbadc0de.be>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
This commit is contained in:
Aris Adamantiadis
2016-02-09 15:09:27 +01:00
committed by Andreas Schneider
parent f8bde7156f
commit 4e6ff36a9a
1 changed files with 17 additions and 5 deletions
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22
src/dh.c
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@@ -227,15 +227,21 @@ void ssh_crypto_finalize(void) {
} }
int ssh_dh_generate_x(ssh_session session) { int ssh_dh_generate_x(ssh_session session) {
int keysize;
if (session->next_crypto->kex_type == SSH_KEX_DH_GROUP1_SHA1) {
keysize = 1023;
} else {
keysize = 2047;
}
session->next_crypto->x = bignum_new(); session->next_crypto->x = bignum_new();
if (session->next_crypto->x == NULL) { if (session->next_crypto->x == NULL) {
return -1; return -1;
} }
#ifdef HAVE_LIBGCRYPT #ifdef HAVE_LIBGCRYPT
bignum_rand(session->next_crypto->x, 128); bignum_rand(session->next_crypto->x, keysize);
#elif defined HAVE_LIBCRYPTO #elif defined HAVE_LIBCRYPTO
bignum_rand(session->next_crypto->x, 128, 0, -1); bignum_rand(session->next_crypto->x, keysize, -1, 0);
#endif #endif
/* not harder than this */ /* not harder than this */
@@ -248,15 +254,21 @@ int ssh_dh_generate_x(ssh_session session) {
/* used by server */ /* used by server */
int ssh_dh_generate_y(ssh_session session) { int ssh_dh_generate_y(ssh_session session) {
session->next_crypto->y = bignum_new(); int keysize;
if (session->next_crypto->kex_type == SSH_KEX_DH_GROUP1_SHA1) {
keysize = 1023;
} else {
keysize = 2047;
}
session->next_crypto->y = bignum_new();
if (session->next_crypto->y == NULL) { if (session->next_crypto->y == NULL) {
return -1; return -1;
} }
#ifdef HAVE_LIBGCRYPT #ifdef HAVE_LIBGCRYPT
bignum_rand(session->next_crypto->y, 128); bignum_rand(session->next_crypto->y, keysize);
#elif defined HAVE_LIBCRYPTO #elif defined HAVE_LIBCRYPTO
bignum_rand(session->next_crypto->y, 128, 0, -1); bignum_rand(session->next_crypto->y, keysize, -1, 0);
#endif #endif
/* not harder than this */ /* not harder than this */