s3:crypto/gse: implement channel binding support

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15621

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>

diff --git a/source3/librpc/crypto/gse.c b/source3/librpc/crypto/gse.c
index ddda18e45d93f010a893c417491cee7607f7ceb9..077b193d60eb364a8a960c65bb7e161fa421285b 100644 (file)
--- a/source3/librpc/crypto/gse.c
+++ b/source3/librpc/crypto/gse.c
@@ -64,6 +64,9 @@ struct gse_context {
        gss_cred_id_t creds;
 
        gss_OID ret_mech;
+
+       struct gss_channel_bindings_struct _channel_bindings;
+       struct gss_channel_bindings_struct *channel_bindings;
 };
 
 /* free non talloc dependent contexts */
@@ -171,7 +174,7 @@ static NTSTATUS gse_setup_server_principal(TALLOC_CTX *mem_ctx,
        return NT_STATUS_OK;
 }
 
-static NTSTATUS gse_context_init(TALLOC_CTX *mem_ctx,
+static NTSTATUS gse_context_init(struct gensec_security *gensec_security,
                                 bool do_sign, bool do_seal,
                                 const char *ccache_name,
                                 uint32_t add_gss_c_flags,
@@ -181,7 +184,7 @@ static NTSTATUS gse_context_init(TALLOC_CTX *mem_ctx,
        krb5_error_code k5ret;
        NTSTATUS status;
 
-       gse_ctx = talloc_zero(mem_ctx, struct gse_context);
+       gse_ctx = talloc_zero(gensec_security, struct gse_context);
        if (!gse_ctx) {
                return NT_STATUS_NO_MEMORY;
        }
@@ -206,6 +209,32 @@ static NTSTATUS gse_context_init(TALLOC_CTX *mem_ctx,
 
        gse_ctx->gss_want_flags |= add_gss_c_flags;
 
+       if (gensec_security->channel_bindings != NULL) {
+               gse_ctx->_channel_bindings.initiator_addrtype =
+                       gensec_security->channel_bindings->initiator_addrtype;
+               gse_ctx->_channel_bindings.initiator_address.value =
+                       gensec_security->channel_bindings->initiator_address.data;
+               gse_ctx->_channel_bindings.initiator_address.length =
+                       gensec_security->channel_bindings->initiator_address.length;
+
+               gse_ctx->_channel_bindings.acceptor_addrtype =
+                       gensec_security->channel_bindings->acceptor_addrtype;
+               gse_ctx->_channel_bindings.acceptor_address.value =
+                       gensec_security->channel_bindings->acceptor_address.data;
+               gse_ctx->_channel_bindings.acceptor_address.length =
+                       gensec_security->channel_bindings->acceptor_address.length;
+
+               gse_ctx->_channel_bindings.application_data.value =
+                       gensec_security->channel_bindings->application_data.data;
+               gse_ctx->_channel_bindings.application_data.length =
+                       gensec_security->channel_bindings->application_data.length;
+
+               gse_ctx->channel_bindings =
+                       &gse_ctx->_channel_bindings;
+       } else {
+               gse_ctx->channel_bindings = GSS_C_NO_CHANNEL_BINDINGS;
+       }
+
        /* Initialize Kerberos Context */
        k5ret = smb_krb5_init_context_common(&gse_ctx->k5ctx);
        if (k5ret) {
@@ -464,7 +493,7 @@ static NTSTATUS gse_get_client_auth_token(TALLOC_CTX *mem_ctx,
                                               &gse_ctx->gss_mech,
                                               gse_ctx->gss_want_flags,
                                               time_req,
-                                              GSS_C_NO_CHANNEL_BINDINGS,
+                                              gse_ctx->channel_bindings,
                                               &in_data,
                                               NULL,
                                               &out_data,
@@ -520,7 +549,8 @@ static NTSTATUS gse_get_client_auth_token(TALLOC_CTX *mem_ctx,
                                        gse_ctx->server_name,
                                        &gse_ctx->gss_mech,
                                        gse_ctx->gss_want_flags,
-                                       time_req, GSS_C_NO_CHANNEL_BINDINGS,
+                                       time_req,
+                                       gse_ctx->channel_bindings,
                                        &in_data, NULL, &out_data,
                                        &gse_ctx->gss_got_flags, &time_rec);
        goto init_sec_context_done;
@@ -620,7 +650,7 @@ done:
        return status;
 }
 
-static NTSTATUS gse_init_server(TALLOC_CTX *mem_ctx,
+static NTSTATUS gse_init_server(struct gensec_security *gensec_security,
                                bool do_sign, bool do_seal,
                                uint32_t add_gss_c_flags,
                                struct gse_context **_gse_ctx)
@@ -630,7 +660,7 @@ static NTSTATUS gse_init_server(TALLOC_CTX *mem_ctx,
        krb5_error_code ret;
        NTSTATUS status;
 
-       status = gse_context_init(mem_ctx, do_sign, do_seal,
+       status = gse_context_init(gensec_security, do_sign, do_seal,
                                  NULL, add_gss_c_flags, &gse_ctx);
        if (!NT_STATUS_IS_OK(status)) {
                return NT_STATUS_NO_MEMORY;
@@ -689,13 +719,46 @@ static NTSTATUS gse_get_server_auth_token(TALLOC_CTX *mem_ctx,
                                         &gse_ctx->gssapi_context,
                                         gse_ctx->creds,
                                         &in_data,
-                                        GSS_C_NO_CHANNEL_BINDINGS,
+                                        gse_ctx->channel_bindings,
                                         &gse_ctx->client_name,
                                         &gse_ctx->ret_mech,
                                         &out_data,
                                         &gse_ctx->gss_got_flags,
                                         &time_rec,
                                         &gse_ctx->delegated_cred_handle);
+#ifdef GSS_C_CHANNEL_BOUND_FLAG
+       if (gss_maj == GSS_S_COMPLETE &&
+           gensec_security->channel_bindings != NULL &&
+           !(gensec_security->want_features & GENSEC_FEATURE_CB_OPTIONAL) &&
+           !(gse_ctx->gss_got_flags & GSS_C_CHANNEL_BOUND_FLAG))
+       {
+               /*
+                * If we require valid channel bindings
+                * we need to check the client provided
+                * them.
+                *
+                * We detect this if
+                * GSS_C_CHANNEL_BOUND_FLAG is given.
+                *
+                * Recent heimdal and MIT releases support this
+                * with older releases (e.g. MIT > 1.19).
+                *
+                * It means client with zero channel bindings
+                * on a server with non-zero channel bindings
+                * won't generate GSS_S_BAD_BINDINGS directly
+                * unless KERB_AP_OPTIONS_CBT was also
+                * provides by the client.
+                *
+                * So we need to convert a missing
+                * GSS_C_CHANNEL_BOUND_FLAG into
+                * GSS_S_BAD_BINDINGS by default
+                * (unless GENSEC_FEATURE_CB_OPTIONAL is given).
+                */
+               gss_maj = GSS_S_BAD_BINDINGS;
+               gss_min = 0;
+       }
+#endif /* GSS_C_CHANNEL_BOUND_FLAG */
+
        switch (gss_maj) {
        case GSS_S_COMPLETE:
                /* we are done with it */
@@ -708,6 +771,10 @@ static NTSTATUS gse_get_server_auth_token(TALLOC_CTX *mem_ctx,
                /* we will need a third leg */
                status = NT_STATUS_MORE_PROCESSING_REQUIRED;
                break;
+       case GSS_S_BAD_BINDINGS:
+               DBG_WARNING("Got GSS_S_BAD_BINDINGS\n");
+               status = NT_STATUS_BAD_BINDINGS;
+               goto done;
        default:
                DEBUG(1, ("gss_accept_sec_context failed with [%s]\n",
                          gse_errstr(talloc_tos(), gss_maj, gss_min)));
@@ -836,6 +903,20 @@ static NTSTATUS gensec_gse_client_start(struct gensec_security *gensec_security)
                want_flags |= GSS_C_DCE_STYLE;
        }
 
+#ifdef HAVE_CLIENT_GSS_C_CHANNEL_BOUND_FLAG
+       /*
+        * We can only use GSS_C_CHANNEL_BOUND_FLAG if the kerberos library
+        * supports that in order to add KERB_AP_OPTIONS_CBT.
+        *
+        * See:
+        * https://github.com/heimdal/heimdal/pull/1234
+        * https://github.com/krb5/krb5/pull/1329
+        */
+       if (!(gensec_security->want_features & GENSEC_FEATURE_CB_OPTIONAL)) {
+               want_flags |= GSS_C_CHANNEL_BOUND_FLAG;
+       }
+#endif
+
        nt_status = gse_init_client(gensec_security, do_sign, do_seal, NULL,
                                    hostname, service, realm,
                                    username, password, want_flags,