ubusd_acl.c

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/*
 * Copyright (C) 2015 John Crispin <blogic@openwrt.org>
 * Copyright (C) 2018 Hans Dedecker <dedeckeh@gmail.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License version 2.1
 * as published by the Free Software Foundation
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */
 
#define _GNU_SOURCE
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/stat.h>
 
#include <syslog.h>
#include <unistd.h>
#include <glob.h>
#include <grp.h>
#include <pwd.h>
 
#include <libubox/vlist.h>
#include <libubox/blobmsg_json.h>
#include <libubox/avl-cmp.h>
#include <libubox/ulog.h>
 
#include "ubusd.h"
 
#ifndef SO_PEERCRED
struct ucred {
        int pid;
        int uid;
        int gid;
};
#endif
 
struct ubusd_acl_obj {
        struct avl_node avl;
        struct list_head list;
 
        bool partial;
 
        const char *user;
        const char *group;
 
        struct blob_attr *methods;
        struct blob_attr *tags;
        struct blob_attr *priv;
        bool subscribe;
        bool publish;
        bool listen;
        bool send;
};
 
struct ubusd_acl_file {
        struct vlist_node avl;
 
        const char *user;
        const char *group;
 
        struct blob_attr *blob;
        struct list_head acl;
 
        int ok;
};
 
const char *ubusd_acl_dir = "/usr/share/acl.d";
static struct blob_buf bbuf;
static struct avl_tree ubusd_acls;
static int ubusd_acl_seq;
static struct ubus_object *acl_obj;
 
static int
ubusd_acl_match_cred(struct ubus_client *cl, struct ubusd_acl_obj *obj)
{
        if (obj->user && !strcmp(cl->user, obj->user))
                return 0;
 
        if (obj->group && !strcmp(cl->group, obj->group))
                return 0;
 
        return -1;
}
 
int
ubusd_acl_check(struct ubus_client *cl, const char *obj,
                const char *method, enum ubusd_acl_type type)
{
        struct ubusd_acl_obj *acl;
        int match_len = 0;
 
        if (!cl || !cl->uid || !obj)
                return 0;
 
        /*
         * Since this tree is sorted alphabetically, we can only expect
         * to find matching entries as long as the number of matching
         * characters between the access list string and the object path
         * is monotonically increasing.
         */
        avl_for_each_element(&ubusd_acls, acl, avl) {
                const char *key = acl->avl.key;
                int cur_match_len;
                bool full_match;
 
                full_match = ubus_strmatch_len(obj, key, &cur_match_len);
                if (cur_match_len < match_len)
                        break;
 
                match_len = cur_match_len;
 
                if (!full_match) {
                        if (!acl->partial)
                                continue;
 
                        if (match_len != (int) strlen(key))
                                continue;
                }
 
                if (ubusd_acl_match_cred(cl, acl))
                        continue;
 
                switch (type) {
                case UBUS_ACL_PUBLISH:
                        if (acl->publish)
                                return 0;
                        break;
 
                case UBUS_ACL_SUBSCRIBE:
                        if (acl->subscribe)
                                return 0;
                        break;
 
                case UBUS_ACL_LISTEN:
                        if (acl->listen)
                                return 0;
                        break;
 
                case UBUS_ACL_SEND:
                        if (acl->send)
                                return 0;
                        break;
 
                case UBUS_ACL_ACCESS:
                        if (acl->methods) {
                                struct blob_attr *cur;
                                char *cur_method;
                                size_t rem;
 
                                blobmsg_for_each_attr(cur, acl->methods, rem)
                                        if (blobmsg_type(cur) == BLOBMSG_TYPE_STRING) {
                                                cur_method = blobmsg_get_string(cur);
 
                                                if (!strcmp(method, cur_method) || !strcmp("*", cur_method))
                                                        return 0;
                                        }
                        }
                        break;
                }
        }
 
        return -1;
}
 
int
ubusd_acl_init_client(struct ubus_client *cl, int fd)
{
        struct ucred cred;
        struct passwd *pwd;
        struct group *group;
 
#ifdef SO_PEERCRED
        unsigned int len = sizeof(struct ucred);
 
        if (getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &cred, &len) == -1) {
                ULOG_ERR("Failed getsockopt(): %m\n");
                return -1;
        }
#else
        memset(&cred, 0, sizeof(cred));
#endif
 
        pwd = getpwuid(cred.uid);
        if (!pwd) {
                ULOG_ERR("Failed getpwuid(): %m\n");
                return -1;
        }
 
        group = getgrgid(cred.gid);
        if (!group) {
                ULOG_ERR("Failed getgrgid(): %m\n");
                return -1;
        }
 
        cl->uid = cred.uid;
        cl->gid = cred.gid;
 
        cl->group = strdup(group->gr_name);
        cl->user = strdup(pwd->pw_name);
 
        return 0;
}
 
void
ubusd_acl_free_client(struct ubus_client *cl)
{
        free(cl->group);
        free(cl->user);
}
 
static void
ubusd_acl_file_free(struct ubusd_acl_file *file)
{
        struct ubusd_acl_obj *p, *q;
 
        list_for_each_entry_safe(p, q, &file->acl, list) {
                avl_delete(&ubusd_acls, &p->avl);
                list_del(&p->list);
                free(p);
        }
 
        free(file);
}
 
enum {
        ACL_ACCESS_METHODS,
        ACL_ACCESS_TAGS,
        ACL_ACCESS_PRIV,
        __ACL_ACCESS_MAX
};
 
static const struct blobmsg_policy acl_obj_policy[__ACL_ACCESS_MAX] = {
        [ACL_ACCESS_METHODS] = { .name = "methods", .type = BLOBMSG_TYPE_ARRAY },
        [ACL_ACCESS_TAGS] = { .name = "tags", .type = BLOBMSG_TYPE_ARRAY },
        [ACL_ACCESS_PRIV] = { .name = "acl", .type = BLOBMSG_TYPE_TABLE },
};
 
static struct ubusd_acl_obj*
ubusd_acl_alloc_obj(struct ubusd_acl_file *file, const char *obj)
{
        struct ubusd_acl_obj *o;
        int len = strlen(obj);
        char *k;
        bool partial = false;
 
        if (obj[len - 1] == '*') {
                partial = true;
                len--;
        }
 
        o = calloc_a(sizeof(*o), &k, len + 1);
        o->partial = partial;
        o->user = file->user;
        o->group = file->group;
        o->avl.key = memcpy(k, obj, len);
 
        list_add(&o->list, &file->acl);
        avl_insert(&ubusd_acls, &o->avl);
 
        return o;
}
 
static void
ubusd_acl_add_access(struct ubusd_acl_file *file, struct blob_attr *obj)
{
        struct blob_attr *tb[__ACL_ACCESS_MAX];
        struct ubusd_acl_obj *o;
 
        blobmsg_parse(acl_obj_policy, __ACL_ACCESS_MAX, tb, blobmsg_data(obj),
                      blobmsg_data_len(obj));
 
        if (!tb[ACL_ACCESS_METHODS] && !tb[ACL_ACCESS_TAGS] && !tb[ACL_ACCESS_PRIV])
                return;
 
        o = ubusd_acl_alloc_obj(file, blobmsg_name(obj));
 
        o->methods = tb[ACL_ACCESS_METHODS];
        o->tags = tb[ACL_ACCESS_TAGS];
        o->priv = tb[ACL_ACCESS_PRIV];
 
        if (file->user || file->group)
                file->ok = 1;
}
 
static void
ubusd_acl_add_subscribe(struct ubusd_acl_file *file, const char *obj)
{
        struct ubusd_acl_obj *o = ubusd_acl_alloc_obj(file, obj);
 
        o->subscribe = true;
}
 
static void
ubusd_acl_add_publish(struct ubusd_acl_file *file, const char *obj)
{
        struct ubusd_acl_obj *o = ubusd_acl_alloc_obj(file, obj);
 
        o->publish = true;
}
 
static void ubusd_acl_add_listen(struct ubusd_acl_file *file, const char *obj)
{
        struct ubusd_acl_obj *o = ubusd_acl_alloc_obj(file, obj);
 
        o->listen = true;
}
 
static void ubusd_acl_add_send(struct ubusd_acl_file *file, const char *obj)
{
        struct ubusd_acl_obj *o = ubusd_acl_alloc_obj(file, obj);
 
        o->send = true;
}
 
enum {
        ACL_USER,
        ACL_GROUP,
        ACL_ACCESS,
        ACL_PUBLISH,
        ACL_SUBSCRIBE,
        ACL_INHERIT,
        ACL_LISTEN,
        ACL_SEND,
        __ACL_MAX
};
 
static const struct blobmsg_policy acl_policy[__ACL_MAX] = {
        [ACL_USER] = { .name = "user", .type = BLOBMSG_TYPE_STRING },
        [ACL_GROUP] = { .name = "group", .type = BLOBMSG_TYPE_STRING },
        [ACL_ACCESS] = { .name = "access", .type = BLOBMSG_TYPE_TABLE },
        [ACL_PUBLISH] = { .name = "publish", .type = BLOBMSG_TYPE_ARRAY },
        [ACL_SUBSCRIBE] = { .name = "subscribe", .type = BLOBMSG_TYPE_ARRAY },
        [ACL_INHERIT] = { .name = "inherit", .type = BLOBMSG_TYPE_ARRAY },
        [ACL_LISTEN] = { .name= "listen", .type = BLOBMSG_TYPE_ARRAY },
        [ACL_SEND] = { .name= "send", .type = BLOBMSG_TYPE_ARRAY },
};
 
static void
ubusd_acl_file_add(struct ubusd_acl_file *file)
{
        struct blob_attr *tb[__ACL_MAX], *cur;
        size_t rem;
 
        blobmsg_parse(acl_policy, __ACL_MAX, tb, blob_data(file->blob),
                      blob_len(file->blob));
 
        if (tb[ACL_USER])
                file->user = blobmsg_get_string(tb[ACL_USER]);
        else if (tb[ACL_GROUP])
                file->group = blobmsg_get_string(tb[ACL_GROUP]);
        else
                return;
 
        if (tb[ACL_ACCESS])
                blobmsg_for_each_attr(cur, tb[ACL_ACCESS], rem)
                        ubusd_acl_add_access(file, cur);
 
        if (tb[ACL_SUBSCRIBE])
                blobmsg_for_each_attr(cur, tb[ACL_SUBSCRIBE], rem)
                        if (blobmsg_type(cur) == BLOBMSG_TYPE_STRING)
                                ubusd_acl_add_subscribe(file, blobmsg_get_string(cur));
 
        if (tb[ACL_PUBLISH])
                blobmsg_for_each_attr(cur, tb[ACL_PUBLISH], rem)
                        if (blobmsg_type(cur) == BLOBMSG_TYPE_STRING)
                                ubusd_acl_add_publish(file, blobmsg_get_string(cur));
 
        if (tb[ACL_LISTEN])
                blobmsg_for_each_attr(cur, tb[ACL_LISTEN], rem)
                        if (blobmsg_type(cur) == BLOBMSG_TYPE_STRING)
                                ubusd_acl_add_listen(file, blobmsg_get_string(cur));
 
        if (tb[ACL_SEND])
                blobmsg_for_each_attr(cur, tb[ACL_SEND], rem)
                        if (blobmsg_type(cur) == BLOBMSG_TYPE_STRING)
                                ubusd_acl_add_send(file, blobmsg_get_string(cur));
}
 
static void
ubusd_acl_update_cb(struct vlist_tree *tree, struct vlist_node *node_new,
        struct vlist_node *node_old)
{
        struct ubusd_acl_file *file;
 
        if (node_old) {
                file = container_of(node_old, struct ubusd_acl_file, avl);
                ubusd_acl_file_free(file);
        }
 
        if (node_new) {
                file = container_of(node_new, struct ubusd_acl_file, avl);
                ubusd_acl_file_add(file);
        }
}
 
static struct ubus_msg_buf *
ubusd_create_sequence_event_msg(void *priv, const char *id)
{
        void *s;
 
        blob_buf_init(&b, 0);
        blob_put_int32(&b, UBUS_ATTR_OBJID, 0);
        blob_put_string(&b, UBUS_ATTR_METHOD, id);
        s = blob_nest_start(&b, UBUS_ATTR_DATA);
        blobmsg_add_u32(&b, "sequence", ubusd_acl_seq);
        blob_nest_end(&b, s);
 
        return ubus_msg_new(b.head, blob_raw_len(b.head), true);
}
 
static VLIST_TREE(ubusd_acl_files, avl_strcmp, ubusd_acl_update_cb, false, false);
 
static int
ubusd_acl_load_file(const char *filename)
{
        struct ubusd_acl_file *file;
        void *blob;
 
        blob_buf_init(&bbuf, 0);
        if (!blobmsg_add_json_from_file(&bbuf, filename)) {
                syslog(LOG_ERR, "failed to parse %s\n", filename);
                return -1;
        }
 
        file = calloc_a(sizeof(*file), &blob, blob_raw_len(bbuf.head));
        if (!file)
                return -1;
 
        file->blob = blob;
 
        memcpy(blob, bbuf.head, blob_raw_len(bbuf.head));
        INIT_LIST_HEAD(&file->acl);
 
        vlist_add(&ubusd_acl_files, &file->avl, filename);
        syslog(LOG_INFO, "loading %s\n", filename);
 
        return 0;
}
 
void
ubusd_acl_load(void)
{
        struct stat st;
        glob_t gl;
        size_t j;
        const char *suffix = "/*.json";
        char *path = alloca(strlen(ubusd_acl_dir) + strlen(suffix) + 1);
 
        sprintf(path, "%s%s", ubusd_acl_dir, suffix);
        if (glob(path, GLOB_NOESCAPE | GLOB_MARK, NULL, &gl))
                return;
 
        vlist_update(&ubusd_acl_files);
        for (j = 0; j < gl.gl_pathc; j++) {
                if (stat(gl.gl_pathv[j], &st) || !S_ISREG(st.st_mode))
                        continue;
 
                if (st.st_uid || st.st_gid) {
                        syslog(LOG_ERR, "%s has wrong owner\n", gl.gl_pathv[j]);
                        continue;
                }
                if (st.st_mode & (S_IWOTH | S_IWGRP | S_IXOTH)) {
                        syslog(LOG_ERR, "%s has wrong permissions\n", gl.gl_pathv[j]);
                        continue;
                }
                ubusd_acl_load_file(gl.gl_pathv[j]);
        }
 
        globfree(&gl);
        vlist_flush(&ubusd_acl_files);
        ubusd_acl_seq++;
        ubusd_send_event(NULL, "ubus.acl.sequence", ubusd_create_sequence_event_msg, NULL);
}
 
static void
ubusd_reply_add(struct ubus_object *obj)
{
        struct ubusd_acl_obj *acl;
        int match_len = 0;
 
        if (!obj->path.key)
                return;
 
        /*
         * Since this tree is sorted alphabetically, we can only expect
         * to find matching entries as long as the number of matching
         * characters between the access list string and the object path
         * is monotonically increasing.
         */
        avl_for_each_element(&ubusd_acls, acl, avl) {
                const char *key = acl->avl.key;
                int cur_match_len;
                bool full_match;
                void *c;
 
                if (!acl->priv)
                        continue;
 
                full_match = ubus_strmatch_len(obj->path.key, key, &cur_match_len);
                if (cur_match_len < match_len)
                        break;
 
                match_len = cur_match_len;
 
                if (!full_match) {
                        if (!acl->partial)
                                continue;
 
                        if (match_len != (int) strlen(key))
                                continue;
                }
 
                c = blobmsg_open_table(&b, NULL);
                blobmsg_add_string(&b, "obj", obj->path.key);
                if (acl->user)
                        blobmsg_add_string(&b, "user", acl->user);
                if (acl->group)
                        blobmsg_add_string(&b, "group", acl->group);
 
                blobmsg_add_field(&b, blobmsg_type(acl->priv), "acl",
                        blobmsg_data(acl->priv), blobmsg_data_len(acl->priv));
 
                blobmsg_close_table(&b, c);
        }
}
 
static int ubusd_reply_query(struct ubus_client *cl, struct ubus_msg_buf *ub, struct blob_attr **attr, struct blob_attr *msg)
{
        struct ubus_object *obj;
        void *d, *a;
 
        if (!attr[UBUS_ATTR_OBJID])
                return UBUS_STATUS_INVALID_ARGUMENT;
 
        obj = ubusd_find_object(blob_get_u32(attr[UBUS_ATTR_OBJID]));
        if (!obj)
                return UBUS_STATUS_NOT_FOUND;
 
        blob_buf_init(&b, 0);
        blob_put_int32(&b, UBUS_ATTR_OBJID, obj->id.id);
        d = blob_nest_start(&b, UBUS_ATTR_DATA);
 
        blobmsg_add_u32(&b, "seq", ubusd_acl_seq);
        a = blobmsg_open_array(&b, "acl");
        list_for_each_entry(obj, &cl->objects, list)
                ubusd_reply_add(obj);
        blobmsg_close_table(&b, a);
 
        blob_nest_end(&b, d);
 
        ubus_proto_send_msg_from_blob(cl, ub, UBUS_MSG_DATA);
 
        return 0;
}
 
static int ubusd_acl_recv(struct ubus_client *cl, struct ubus_msg_buf *ub, const char *method, struct blob_attr *msg)
{
        if (!strcmp(method, "query"))
                return ubusd_reply_query(cl, ub, ubus_parse_msg(ub->data, blob_raw_len(ub->data)), msg);
 
        return UBUS_STATUS_INVALID_COMMAND;
}
 
void ubusd_acl_init(void)
{
        ubus_init_string_tree(&ubusd_acls, true);
        acl_obj = ubusd_create_object_internal(NULL, UBUS_SYSTEM_OBJECT_ACL);
        acl_obj->recv_msg = ubusd_acl_recv;
}