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Fix CVE-2016-0739 (Weak Diffie-Hellman secret generation in
dh_generate_x() and dh_generate_y()).
"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."
Source:
https://git.libssh.org/projects/libssh.git/commit/?id=f8d0026c65fc8a55748ae481758e2cf376c26c86
This patch was created by upstream for libssh-0.7.3, but applied without
modification to libssh-0.6.3 by Debian. In Guix, we apply it without
modification to libssh-0.6.5.
References:
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2016-0739
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-0739
https://security-tracker.debian.org/tracker/CVE-2016-0739
---
src/dh.c | 22 +++++++++++++++++-----
1 file changed, 17 insertions(+), 5 deletions(-)
diff --git a/src/dh.c b/src/dh.c
index e489a1d..d27b66e 100644
--- a/src/dh.c
+++ b/src/dh.c
@@ -227,15 +227,21 @@ void ssh_crypto_finalize(void) {
}
int 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();
if (session->next_crypto->x == NULL) {
return -1;
}
#ifdef HAVE_LIBGCRYPT
- bignum_rand(session->next_crypto->x, 128);
+ bignum_rand(session->next_crypto->x, keysize);
#elif defined HAVE_LIBCRYPTO
- bignum_rand(session->next_crypto->x, 128, 0, -1);
+ bignum_rand(session->next_crypto->x, keysize, -1, 0);
#endif
/* not harder than this */
@@ -248,15 +254,21 @@ int dh_generate_x(ssh_session session) {
/* used by server */
int 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) {
return -1;
}
#ifdef HAVE_LIBGCRYPT
- bignum_rand(session->next_crypto->y, 128);
+ bignum_rand(session->next_crypto->y, keysize);
#elif defined HAVE_LIBCRYPTO
- bignum_rand(session->next_crypto->y, 128, 0, -1);
+ bignum_rand(session->next_crypto->y, keysize, -1, 0);
#endif
/* not harder than this */
--
cgit v0.12
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