NetworkManager/src/core/nm-auth-utils.c

/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 * Copyright (C) 2010 Red Hat, Inc.
 */

#include "nm-default.h"

#include "nm-auth-utils.h"

#include "nm-glib-aux/nm-c-list.h"
#include "nm-setting-connection.h"
#include "nm-libnm-core-intern/nm-auth-subject.h"
#include "nm-auth-manager.h"
#include "nm-session-monitor.h"
#include "nm-dbus-manager.h"
#include "nm-core-utils.h"

/*****************************************************************************/

typedef struct {
    const char *   tag;
    gpointer       data;
    GDestroyNotify destroy;
} ChainData;

struct _NMAuthChain {
    CList parent_lst;

    ChainData *data_arr;
    guint      data_len;
    guint      data_alloc;

    CList auth_call_lst_head;

    GDBusMethodInvocation *context;
    NMAuthSubject *        subject;

    GCancellable *cancellable;

    /* if set, it also means that the chain is already started and was cancelled. */
    GSource *cancellable_idle_source;

    NMAuthChainResultFunc done_func;
    gpointer              user_data;

    gulong cancellable_id;

    guint num_pending_auth_calls;

    bool is_started : 1;
    bool is_destroyed : 1;
    bool is_finishing : 1;
};

G_STATIC_ASSERT(G_STRUCT_OFFSET(NMAuthChain, parent_lst) == 0);

typedef struct {
    CList                auth_call_lst;
    NMAuthChain *        chain;
    NMAuthManagerCallId *call_id;
    const char *         permission;
    NMAuthCallResult     result;
} AuthCall;

/*****************************************************************************/

static void _auth_chain_destroy(NMAuthChain *self);

/*****************************************************************************/

static void
_ASSERT_call(AuthCall *call)
{
    nm_assert(call);
    nm_assert(call->chain);
    nm_assert(call->permission && strlen(call->permission) > 0);
    nm_assert(nm_c_list_contains_entry(&call->chain->auth_call_lst_head, call, auth_call_lst));
#if NM_MORE_ASSERTS > 5
    {
        AuthCall *auth_call;
        guint     n = 0;

        c_list_for_each_entry (auth_call, &call->chain->auth_call_lst_head, auth_call_lst) {
            nm_assert(auth_call->result == NM_AUTH_CALL_RESULT_UNKNOWN || !auth_call->call_id);
            if (auth_call->call_id)
                n++;
        }
        nm_assert(n == call->chain->num_pending_auth_calls);
    }
#endif
}

/*****************************************************************************/

static void
_done_and_destroy(NMAuthChain *self)
{
    self->is_finishing = TRUE;
    self->done_func(self, self->context, self->user_data);
    nm_assert(self->is_finishing);
    _auth_chain_destroy(self);
}

static gboolean
_cancellable_idle_cb(gpointer user_data)
{
    NMAuthChain *self = user_data;
    AuthCall *   call;

    nm_assert(g_cancellable_is_cancelled(self->cancellable));
    nm_assert(self->cancellable_idle_source);

    c_list_for_each_entry (call, &self->auth_call_lst_head, auth_call_lst) {
        if (call->call_id) {
            self->num_pending_auth_calls--;
            nm_auth_manager_check_authorization_cancel(g_steal_pointer(&call->call_id));
        }
    }

    _done_and_destroy(self);
    return G_SOURCE_REMOVE;
}

static void
_cancellable_on_idle(NMAuthChain *self)
{
    if (self->cancellable_idle_source)
        return;

    self->cancellable_idle_source =
        nm_g_idle_source_new(G_PRIORITY_DEFAULT, _cancellable_idle_cb, self, NULL);
    g_source_attach(self->cancellable_idle_source, NULL);
}

GCancellable *
nm_auth_chain_get_cancellable(NMAuthChain *self)
{
    return self->cancellable;
}

static void
_cancellable_cancelled(GCancellable *cancellable, NMAuthChain *self)
{
    _cancellable_on_idle(self);
}

void
nm_auth_chain_set_cancellable(NMAuthChain *self, GCancellable *cancellable)
{
    g_return_if_fail(self);
    g_return_if_fail(G_IS_CANCELLABLE(cancellable));

    /* after the chain is started, the cancellable can no longer be changed.
     * No need to handle the complexity of swapping the cancellable *after*
     * requests are already started. */
    g_return_if_fail(!self->is_started);
    nm_assert(c_list_is_empty(&self->auth_call_lst_head));

    /* also no need to allow setting different cancellables. */
    g_return_if_fail(!self->cancellable);

    self->cancellable = g_object_ref(cancellable);
}

/*****************************************************************************/

static void
auth_call_free(AuthCall *call)
{
    _ASSERT_call(call);

    c_list_unlink_stale(&call->auth_call_lst);
    if (call->call_id) {
        call->chain->num_pending_auth_calls--;
        nm_auth_manager_check_authorization_cancel(call->call_id);
    }
    nm_g_slice_free(call);
}

static AuthCall *
_find_auth_call(NMAuthChain *self, const char *permission)
{
    AuthCall *auth_call;

    c_list_for_each_entry (auth_call, &self->auth_call_lst_head, auth_call_lst) {
        if (nm_streq(auth_call->permission, permission))
            return auth_call;
    }
    return NULL;
}

/*****************************************************************************/

static ChainData *
_get_data(NMAuthChain *self, const char *tag)
{
    guint i;

    for (i = 0; i < self->data_len; i++) {
        ChainData *chain_data = &self->data_arr[i];

        if (chain_data->tag && nm_streq(chain_data->tag, tag))
            return chain_data;
    }
    return NULL;
}

gpointer
nm_auth_chain_get_data(NMAuthChain *self, const char *tag)
{
    ChainData *chain_data;

    g_return_val_if_fail(self, NULL);
    g_return_val_if_fail(tag, NULL);

    chain_data = _get_data(self, tag);
    return chain_data ? chain_data->data : NULL;
}

/**
 * nm_auth_chain_steal_data:
 * @self: A #NMAuthChain.
 * @tag: A "tag" uniquely identifying the data to steal.
 *
 * Removes the datum associated with @tag from the chain's data associations,
 * without invoking the association's destroy handler.  The caller assumes
 * ownership over the returned value.
 *
 * Returns: the datum originally associated with @tag
 */
gpointer
nm_auth_chain_steal_data(NMAuthChain *self, const char *tag)
{
    ChainData *chain_data;

    g_return_val_if_fail(self, NULL);
    g_return_val_if_fail(tag, NULL);

    chain_data = _get_data(self, tag);
    if (!chain_data)
        return NULL;

    /* Make sure the destroy handler isn't called when freeing.
     *
     * We don't bother to really remove the element from the array.
     * Just mark the entry as unused by clearing the tag. */
    chain_data->destroy = NULL;
    chain_data->tag     = NULL;
    return chain_data->data;
}

/**
 * nm_auth_chain_set_data_unsafe:
 * @self: the #NMAuthChain
 * @tag: the tag for referencing the attached data.
 * @data: the data to attach. If %NULL, this call has no effect
 *   and nothing is attached.
 * @data_destroy: (allow-none): the destroy function for the data pointer.
 *
 * @tag string is not cloned and must outlive @self. That is why
 * the function is "unsafe". Use nm_auth_chain_set_data() with a C literal
 * instead.
 *
 * It is a bug to add the same tag more than once.
 */
void
nm_auth_chain_set_data_unsafe(NMAuthChain *  self,
                              const char *   tag,
                              gpointer       data,
                              GDestroyNotify data_destroy)
{
    ChainData *chain_data;

    g_return_if_fail(self);
    g_return_if_fail(tag);

    /* The tag must not yet exist. Otherwise, we'd have to first search the
     * list for an existing entry. That usage pattern is not supported. */
    nm_assert(!_get_data(self, tag));

    if (!data) {
        /* we don't track user data of %NULL.
         *
         * In the past this had also the meaning of removing a user-data. But since
         * nm_auth_chain_set_data() does not allow being called more than once
         * for the same tag, we don't need to remove anything. */
        return;
    }

    if (self->data_len + 1 > self->data_alloc) {
        if (self->data_alloc == 0)
            self->data_alloc = 8;
        else
            self->data_alloc *= 2;
        self->data_arr = g_realloc(self->data_arr, sizeof(self->data_arr[0]) * self->data_alloc);
    }

    chain_data  = &self->data_arr[self->data_len++];
    *chain_data = (ChainData){
        .tag     = tag,
        .data    = data,
        .destroy = data_destroy,
    };
}

/*****************************************************************************/

NMAuthCallResult
nm_auth_chain_get_result(NMAuthChain *self, const char *permission)
{
    AuthCall *auth_call;

    g_return_val_if_fail(self, NM_AUTH_CALL_RESULT_UNKNOWN);
    g_return_val_if_fail(permission, NM_AUTH_CALL_RESULT_UNKNOWN);

    /* it is a bug to request the result other than from the done_func()
     * callback. You are not supposed to poll for the result but request
     * it upon notification. */
    nm_assert(self->is_finishing);

    auth_call = _find_auth_call(self, permission);

    /* it is a bug to request a permission result that was not
     * previously requested or which did not complete yet. */
    if (!auth_call)
        g_return_val_if_reached(NM_AUTH_CALL_RESULT_UNKNOWN);

    nm_assert(!auth_call->call_id);

    if (self->cancellable_idle_source) {
        /* already cancelled. We always return unknown (even if we happen to
         * have already received the response. */
        return NM_AUTH_CALL_RESULT_UNKNOWN;
    }

    return auth_call->result;
}

NMAuthSubject *
nm_auth_chain_get_subject(NMAuthChain *self)
{
    g_return_val_if_fail(self, NULL);

    return self->subject;
}

GDBusMethodInvocation *
nm_auth_chain_get_context(NMAuthChain *self)
{
    g_return_val_if_fail(self, NULL);

    return self->context;
}

/*****************************************************************************/

static void
pk_call_cb(NMAuthManager *      auth_manager,
           NMAuthManagerCallId *call_id,
           gboolean             is_authorized,
           gboolean             is_challenge,
           GError *             error,
           gpointer             user_data)
{
    NMAuthChain *self;
    AuthCall *   call;

    nm_assert(call_id);

    if (g_error_matches(error, G_IO_ERROR, G_IO_ERROR_CANCELLED))
        return;

    call = user_data;

    _ASSERT_call(call);
    nm_assert(call->call_id == call_id);
    nm_assert(call->result == NM_AUTH_CALL_RESULT_UNKNOWN);

    self = call->chain;

    nm_assert(!self->is_destroyed);
    nm_assert(!self->is_finishing);

    call->call_id = NULL;

    call->result = nm_auth_call_result_eval(is_authorized, is_challenge, error);

    call->chain->num_pending_auth_calls--;

    _ASSERT_call(call);

    if (call->chain->num_pending_auth_calls == 0) {
        /* we are on an idle-handler or a clean call-stack (non-reentrant) so it's safe
         * to invoke the callback right away. */
        _done_and_destroy(self);
    }
}

/**
 * nm_auth_chain_add_call_unsafe:
 * @self: the #NMAuthChain
 * @permission: the permission string. This string is kept by reference
 *   and you must make sure that it's lifetime lasts until the NMAuthChain
 *   gets destroyed. That's why the function is "unsafe". Use
 *   nm_auth_chain_add_call() instead.
 * @allow_interaction: flag
 *
 * It's "unsafe" because @permission is not copied. It's the callers responsibility
 * that the permission string stays valid as long as NMAuthChain.
 *
 * If you can, use nm_auth_chain_add_call() instead!
 *
 * If you have a non-static string, you may attach the permission string as
 * user-data via nm_auth_chain_set_data().
 */
void
nm_auth_chain_add_call_unsafe(NMAuthChain *self, const char *permission, gboolean allow_interaction)
{
    AuthCall *call;

    g_return_if_fail(self);
    g_return_if_fail(self->subject);
    g_return_if_fail(!self->is_finishing);
    g_return_if_fail(!self->is_destroyed);
    g_return_if_fail(permission && *permission);
    nm_assert(NM_IN_SET(nm_auth_subject_get_subject_type(self->subject),
                        NM_AUTH_SUBJECT_TYPE_UNIX_PROCESS,
                        NM_AUTH_SUBJECT_TYPE_INTERNAL));

    /* duplicate permissions are not supported, also because nm_auth_chain_get_result()
     * can only return one-permission. */
    nm_assert(!_find_auth_call(self, permission));

    if (!self->is_started) {
        self->is_started = TRUE;
        nm_assert(!self->cancellable_id);
        if (self->cancellable) {
            if (g_cancellable_is_cancelled(self->cancellable)) {
                /* the operation is already cancelled. Schedule the callback on idle. */
                _cancellable_on_idle(self);
            } else {
                self->cancellable_id = g_signal_connect(self->cancellable,
                                                        "cancelled",
                                                        G_CALLBACK(_cancellable_cancelled),
                                                        self);
            }
        }
    }

    call  = g_slice_new(AuthCall);
    *call = (AuthCall){
        .chain   = self,
        .call_id = NULL,
        .result  = NM_AUTH_CALL_RESULT_UNKNOWN,

        /* we don't clone the permission string. It's the callers responsibility. */
        .permission = permission,
    };

    /* above we assert that no duplicate permissions are added. Still, track the
     * new request to the front of the list so that it would shadow an earlier
     * call. */
    c_list_link_front(&self->auth_call_lst_head, &call->auth_call_lst);

    if (self->cancellable_idle_source) {
        /* already cancelled. No need to actually start the request. */
        nm_assert(call->result == NM_AUTH_CALL_RESULT_UNKNOWN);
    } else {
        call->call_id = nm_auth_manager_check_authorization(nm_auth_manager_get(),
                                                            self->subject,
                                                            permission,
                                                            allow_interaction,
                                                            pk_call_cb,
                                                            call);

        self->num_pending_auth_calls++;
    }

    _ASSERT_call(call);

    /* we track auth-calls in a linked list. If we end up requesting too many permissions this
     * becomes inefficient. If that ever happens, consider a more efficient data structure for
     * a large number of requests. */
    nm_assert(c_list_length(&self->auth_call_lst_head) < 25);
    G_STATIC_ASSERT_EXPR(NM_CLIENT_PERMISSION_LAST < 25);
}

/*****************************************************************************/

/* Creates the NMAuthSubject automatically */
NMAuthChain *
nm_auth_chain_new_context(GDBusMethodInvocation *context,
                          NMAuthChainResultFunc  done_func,
                          gpointer               user_data)
{
    NMAuthSubject *subject;
    NMAuthChain *  chain;

    g_return_val_if_fail(context, NULL);
    nm_assert(done_func);

    subject = nm_dbus_manager_new_auth_subject_from_context(context);
    if (!subject)
        return NULL;

    chain = nm_auth_chain_new_subject(subject, context, done_func, user_data);
    g_object_unref(subject);
    return chain;
}

NMAuthChain *
nm_auth_chain_new_subject(NMAuthSubject *        subject,
                          GDBusMethodInvocation *context,
                          NMAuthChainResultFunc  done_func,
                          gpointer               user_data)
{
    NMAuthChain *self;

    g_return_val_if_fail(NM_IS_AUTH_SUBJECT(subject), NULL);
    nm_assert(NM_IN_SET(nm_auth_subject_get_subject_type(subject),
                        NM_AUTH_SUBJECT_TYPE_UNIX_PROCESS,
                        NM_AUTH_SUBJECT_TYPE_INTERNAL));
    nm_assert(done_func);

    self  = g_slice_new(NMAuthChain);
    *self = (NMAuthChain){
        .done_func          = done_func,
        .user_data          = user_data,
        .context            = nm_g_object_ref(context),
        .subject            = g_object_ref(subject),
        .parent_lst         = C_LIST_INIT(self->parent_lst),
        .auth_call_lst_head = C_LIST_INIT(self->auth_call_lst_head),
    };
    return self;
}

/**
 * nm_auth_chain_destroy:
 * @self: the auth-chain
 *
 * Destroys the auth-chain. By destroying the auth-chain, you also cancel
 * the receipt of the done-callback. IOW, the callback will not be invoked.
 *
 * The only exception is, you may call nm_auth_chain_destroy() from inside
 * the callback. In this case the call has no effect and @self stays alive
 * until the callback returns.
 *
 * Note that you might only destroy an auth-chain exactly once, and never
 * after the callback was handled. After the callback returns, the auth chain
 * always gets automatically destroyed. So you only need to explicitly destroy
 * it, if you want to abort it before the callback complets.
 */
void
nm_auth_chain_destroy(NMAuthChain *self)
{
    g_return_if_fail(self);
    g_return_if_fail(!self->is_destroyed);

    self->is_destroyed = TRUE;

    if (self->is_finishing) {
        /* we are called from inside the callback. Keep the instance alive for the moment. */
        return;
    }

    _auth_chain_destroy(self);
}

static void
_auth_chain_destroy(NMAuthChain *self)
{
    AuthCall *call;

    c_list_unlink(&self->parent_lst);

    nm_clear_g_object(&self->subject);
    nm_clear_g_object(&self->context);

    nm_clear_g_signal_handler(self->cancellable, &self->cancellable_id);
    nm_clear_g_source_inst(&self->cancellable_idle_source);

    /* we must first destroy all AuthCall instances before ChainData. The reason is
     * that AuthData.permission is not cloned and the lifetime of the string must
     * be ensured by the caller. A sensible thing to do for the caller is attach the
     * permission string via nm_auth_chain_set_data(). Hence, first free the AuthCall. */
    while ((call = c_list_first_entry(&self->auth_call_lst_head, AuthCall, auth_call_lst)))
        auth_call_free(call);

    while (self->data_len > 0) {
        ChainData *chain_data = &self->data_arr[--self->data_len];

        if (chain_data->destroy)
            chain_data->destroy(chain_data->data);
    }
    g_free(self->data_arr);

    nm_g_object_unref(self->cancellable);

    nm_g_slice_free(self);
}

/******************************************************************************
 * utils
 *****************************************************************************/

gboolean
nm_auth_is_subject_in_acl(NMConnection *connection, NMAuthSubject *subject, char **out_error_desc)
{
    NMSettingConnection *s_con;
    gs_free char *       user = NULL;
    gulong               uid;

    g_return_val_if_fail(connection, FALSE);
    g_return_val_if_fail(NM_IS_AUTH_SUBJECT(subject), FALSE);
    nm_assert(NM_IN_SET(nm_auth_subject_get_subject_type(subject),
                        NM_AUTH_SUBJECT_TYPE_UNIX_PROCESS,
                        NM_AUTH_SUBJECT_TYPE_INTERNAL));

    if (nm_auth_subject_get_subject_type(subject) == NM_AUTH_SUBJECT_TYPE_INTERNAL)
        return TRUE;

    uid = nm_auth_subject_get_unix_process_uid(subject);

    /* Root gets a free pass */
    if (0 == uid)
        return TRUE;

    user = nm_utils_uid_to_name(uid);
    if (!user) {
        NM_SET_OUT(out_error_desc,
                   g_strdup_printf("Could not determine username for uid %lu", uid));
        return FALSE;
    }

    s_con = nm_connection_get_setting_connection(connection);
    if (!s_con) {
        /* This can only happen when called from AddAndActivate, so we know
         * the user will be authorized when the connection is completed.
         */
        return TRUE;
    }

    /* Match the username returned by the session check to a user in the ACL */
    if (!nm_setting_connection_permissions_user_allowed(s_con, user)) {
        NM_SET_OUT(out_error_desc,
                   g_strdup_printf("uid %lu has no permission to perform this operation", uid));
        return FALSE;
    }

    return TRUE;
}

gboolean
nm_auth_is_subject_in_acl_set_error(NMConnection * connection,
                                    NMAuthSubject *subject,
                                    GQuark         err_domain,
                                    int            err_code,
                                    GError **      error)
{
    char *error_desc = NULL;

    nm_assert(!error || !*error);

    if (nm_auth_is_subject_in_acl(connection, subject, error ? &error_desc : NULL))
        return TRUE;

    g_set_error_literal(error, err_domain, err_code, error_desc);
    g_free(error_desc);
    return FALSE;
}

gboolean
nm_auth_is_invocation_in_acl_set_error(NMConnection *         connection,
                                       GDBusMethodInvocation *invocation,
                                       GQuark                 err_domain,
                                       int                    err_code,
                                       NMAuthSubject **       out_subject,
                                       GError **              error)
{
    gs_unref_object NMAuthSubject *subject = NULL;
    gboolean                       success;

    nm_assert(!out_subject || !*out_subject);

    subject = nm_dbus_manager_new_auth_subject_from_context(invocation);
    if (!subject) {
        g_set_error_literal(error, err_domain, err_code, NM_UTILS_ERROR_MSG_REQ_UID_UKNOWN);
        return FALSE;
    }

    success = nm_auth_is_subject_in_acl_set_error(connection, subject, err_domain, err_code, error);

    NM_SET_OUT(out_subject, g_steal_pointer(&subject));

    return success;
}