CVE-2020-1472(ZeroLogon): libcli/auth: add netlogon_creds_random_challenge()

It's good to have just a single isolated function that will generate
random challenges, in future we can add some logic in order to
avoid weak values, which are likely to be rejected by a server.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14497

Signed-off-by: Stefan Metzmacher <metze@samba.org>

diff --git a/libcli/auth/credentials.c b/libcli/auth/credentials.c
index 319dacdac0b8734389e44954359f1486a6b6377c..c79f5e2ce24514fb2608d9d5909b224253dbaab1 100644 (file)
--- a/libcli/auth/credentials.c
+++ b/libcli/auth/credentials.c
@@ -30,9 +30,16 @@
 #include <gnutls/gnutls.h>
 #include <gnutls/crypto.h>
 
+void netlogon_creds_random_challenge(struct netr_Credential *challenge)
+{
+       ZERO_STRUCTP(challenge);
+       generate_random_buffer(challenge->data, sizeof(challenge->data));
+}
+
 static void netlogon_creds_step_crypt(struct netlogon_creds_CredentialState *creds,
                                      const struct netr_Credential *in,
                                      struct netr_Credential *out)
+
 {
        if (creds->negotiate_flags & NETLOGON_NEG_SUPPORTS_AES) {
                AES_KEY key;

diff --git a/libcli/auth/proto.h b/libcli/auth/proto.h
index afd7f0d148d99c042edc2874a07c686dc779882f..19a0e846357e0530f6af5918d83f8f718c991548 100644 (file)
--- a/libcli/auth/proto.h
+++ b/libcli/auth/proto.h
@@ -11,10 +11,13 @@
 
 /* The following definitions come from /home/jeremy/src/samba/git/master/source3/../source4/../libcli/auth/credentials.c  */
 
+void netlogon_creds_random_challenge(struct netr_Credential *challenge);
+
 void netlogon_creds_des_encrypt_LMKey(struct netlogon_creds_CredentialState *creds, struct netr_LMSessionKey *key);
 void netlogon_creds_des_decrypt_LMKey(struct netlogon_creds_CredentialState *creds, struct netr_LMSessionKey *key);
 void netlogon_creds_des_encrypt(struct netlogon_creds_CredentialState *creds, struct samr_Password *pass);
 void netlogon_creds_des_decrypt(struct netlogon_creds_CredentialState *creds, struct samr_Password *pass);
+
 NTSTATUS netlogon_creds_arcfour_crypt(struct netlogon_creds_CredentialState *creds,
                                      uint8_t *data,
                                      size_t len);