src/udev/udev-ctrl.c

/* SPDX-License-Identifier: LGPL-2.1+
 *
 * libudev - interface to udev device information
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 */

#include <errno.h>
#include <poll.h>
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>

#include "alloc-util.h"
#include "fd-util.h"
#include "format-util.h"
#include "io-util.h"
#include "socket-util.h"
#include "strxcpyx.h"
#include "udev-ctrl.h"
#include "util.h"

/* wire protocol magic must match */
#define UDEV_CTRL_MAGIC                                0xdead1dea

enum udev_ctrl_msg_type {
        UDEV_CTRL_UNKNOWN,
        UDEV_CTRL_SET_LOG_LEVEL,
        UDEV_CTRL_STOP_EXEC_QUEUE,
        UDEV_CTRL_START_EXEC_QUEUE,
        UDEV_CTRL_RELOAD,
        UDEV_CTRL_SET_ENV,
        UDEV_CTRL_SET_CHILDREN_MAX,
        UDEV_CTRL_PING,
        UDEV_CTRL_EXIT,
};

struct udev_ctrl_msg_wire {
        char version[16];
        unsigned magic;
        enum udev_ctrl_msg_type type;
        union {
                int intval;
                char buf[256];
        };
};

struct udev_ctrl_msg {
        unsigned n_ref;
        struct udev_ctrl_connection *conn;
        struct udev_ctrl_msg_wire ctrl_msg_wire;
};

struct udev_ctrl {
        unsigned n_ref;
        int sock;
        union sockaddr_union saddr;
        socklen_t addrlen;
        bool bound;
        bool cleanup_socket;
        bool connected;
};

struct udev_ctrl_connection {
        unsigned n_ref;
        struct udev_ctrl *uctrl;
        int sock;
};

struct udev_ctrl *udev_ctrl_new_from_fd(int fd) {
        struct udev_ctrl *uctrl;
        int r;

        uctrl = new0(struct udev_ctrl, 1);
        if (!uctrl)
                return NULL;
        uctrl->n_ref = 1;

        if (fd < 0) {
                uctrl->sock = socket(AF_LOCAL, SOCK_SEQPACKET|SOCK_NONBLOCK|SOCK_CLOEXEC, 0);
                if (uctrl->sock < 0) {
                        log_error_errno(errno, "Failed to create socket: %m");
                        udev_ctrl_unref(uctrl);
                        return NULL;
                }
        } else {
                uctrl->bound = true;
                uctrl->sock = fd;
        }

        /*
         * FIXME: remove it as soon as we can depend on this:
         *   http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=90c6bd34f884cd9cee21f1d152baf6c18bcac949
         */
        r = setsockopt_int(uctrl->sock, SOL_SOCKET, SO_PASSCRED, true);
        if (r < 0)
                log_warning_errno(r, "Failed to set SO_PASSCRED: %m");

        uctrl->saddr.un = (struct sockaddr_un) {
                .sun_family = AF_UNIX,
                .sun_path = "/run/udev/control",
        };

        uctrl->addrlen = SOCKADDR_UN_LEN(uctrl->saddr.un);
        return uctrl;
}

struct udev_ctrl *udev_ctrl_new(void) {
        return udev_ctrl_new_from_fd(-1);
}

int udev_ctrl_enable_receiving(struct udev_ctrl *uctrl) {
        int err;

        if (!uctrl->bound) {
                err = bind(uctrl->sock, &uctrl->saddr.sa, uctrl->addrlen);
                if (err < 0 && errno == EADDRINUSE) {
                        (void) sockaddr_un_unlink(&uctrl->saddr.un);
                        err = bind(uctrl->sock, &uctrl->saddr.sa, uctrl->addrlen);
                }

                if (err < 0)
                        return log_error_errno(errno, "Failed to bind socket: %m");

                err = listen(uctrl->sock, 0);
                if (err < 0)
                        return log_error_errno(errno, "Failed to listen: %m");

                uctrl->bound = true;
                uctrl->cleanup_socket = true;
        }
        return 0;
}

static struct udev_ctrl *udev_ctrl_free(struct udev_ctrl *uctrl) {
        assert(uctrl);

        safe_close(uctrl->sock);
        return mfree(uctrl);
}

DEFINE_PRIVATE_TRIVIAL_REF_FUNC(struct udev_ctrl, udev_ctrl);
DEFINE_TRIVIAL_UNREF_FUNC(struct udev_ctrl, udev_ctrl, udev_ctrl_free);

int udev_ctrl_cleanup(struct udev_ctrl *uctrl) {
        if (!uctrl)
                return 0;
        if (uctrl->cleanup_socket)
                sockaddr_un_unlink(&uctrl->saddr.un);
        return 0;
}

int udev_ctrl_get_fd(struct udev_ctrl *uctrl) {
        if (!uctrl)
                return -EINVAL;
        return uctrl->sock;
}

struct udev_ctrl_connection *udev_ctrl_get_connection(struct udev_ctrl *uctrl) {
        struct udev_ctrl_connection *conn;
        struct ucred ucred = {};
        int r;

        conn = new(struct udev_ctrl_connection, 1);
        if (!conn)
                return NULL;
        conn->n_ref = 1;
        conn->uctrl = uctrl;

        conn->sock = accept4(uctrl->sock, NULL, NULL, SOCK_CLOEXEC|SOCK_NONBLOCK);
        if (conn->sock < 0) {
                if (errno != EINTR)
                        log_error_errno(errno, "Failed to receive ctrl connection: %m");
                goto err;
        }

        /* check peer credential of connection */
        r = getpeercred(conn->sock, &ucred);
        if (r < 0) {
                log_error_errno(r, "Failed to receive credentials of ctrl connection: %m");
                goto err;
        }
        if (ucred.uid > 0) {
                log_error("Sender uid="UID_FMT", message ignored", ucred.uid);
                goto err;
        }

        /* enable receiving of the sender credentials in the messages */
        r = setsockopt_int(conn->sock, SOL_SOCKET, SO_PASSCRED, true);
        if (r < 0)
                log_warning_errno(r, "Failed to set SO_PASSCRED: %m");

        udev_ctrl_ref(uctrl);
        return conn;
err:
        safe_close(conn->sock);
        return mfree(conn);
}

static struct udev_ctrl_connection *udev_ctrl_connection_free(struct udev_ctrl_connection *conn) {
        assert(conn);

        safe_close(conn->sock);
        udev_ctrl_unref(conn->uctrl);
        return mfree(conn);
}

DEFINE_TRIVIAL_REF_UNREF_FUNC(struct udev_ctrl_connection, udev_ctrl_connection, udev_ctrl_connection_free);

static int ctrl_send(struct udev_ctrl *uctrl, enum udev_ctrl_msg_type type, int intval, const char *buf, usec_t timeout) {
        struct udev_ctrl_msg_wire ctrl_msg_wire = {
                .version = "udev-" STRINGIFY(PROJECT_VERSION),
                .magic = UDEV_CTRL_MAGIC,
                .type = type,
        };

        if (buf)
                strscpy(ctrl_msg_wire.buf, sizeof(ctrl_msg_wire.buf), buf);
        else
                ctrl_msg_wire.intval = intval;

        if (!uctrl->connected) {
                if (connect(uctrl->sock, &uctrl->saddr.sa, uctrl->addrlen) < 0)
                        return -errno;
                uctrl->connected = true;
        }
        if (send(uctrl->sock, &ctrl_msg_wire, sizeof(ctrl_msg_wire), 0) < 0)
                return -errno;

        /* wait for peer message handling or disconnect */
        for (;;) {
                struct pollfd pfd = {
                        .fd = uctrl->sock,
                        .events = POLLIN,
                };
                int r;

                r = poll(&pfd, 1, DIV_ROUND_UP(timeout, USEC_PER_MSEC));
                if (r < 0) {
                        if (errno == EINTR)
                                continue;
                        return -errno;
                }
                if (r == 0)
                        return -ETIMEDOUT;
                if (pfd.revents & POLLERR)
                        return -EIO;
                return 0;
        }
}

int udev_ctrl_send_set_log_level(struct udev_ctrl *uctrl, int priority, usec_t timeout) {
        return ctrl_send(uctrl, UDEV_CTRL_SET_LOG_LEVEL, priority, NULL, timeout);
}

int udev_ctrl_send_stop_exec_queue(struct udev_ctrl *uctrl, usec_t timeout) {
        return ctrl_send(uctrl, UDEV_CTRL_STOP_EXEC_QUEUE, 0, NULL, timeout);
}

int udev_ctrl_send_start_exec_queue(struct udev_ctrl *uctrl, usec_t timeout) {
        return ctrl_send(uctrl, UDEV_CTRL_START_EXEC_QUEUE, 0, NULL, timeout);
}

int udev_ctrl_send_reload(struct udev_ctrl *uctrl, usec_t timeout) {
        return ctrl_send(uctrl, UDEV_CTRL_RELOAD, 0, NULL, timeout);
}

int udev_ctrl_send_set_env(struct udev_ctrl *uctrl, const char *key, usec_t timeout) {
        return ctrl_send(uctrl, UDEV_CTRL_SET_ENV, 0, key, timeout);
}

int udev_ctrl_send_set_children_max(struct udev_ctrl *uctrl, int count, usec_t timeout) {
        return ctrl_send(uctrl, UDEV_CTRL_SET_CHILDREN_MAX, count, NULL, timeout);
}

int udev_ctrl_send_ping(struct udev_ctrl *uctrl, usec_t timeout) {
        return ctrl_send(uctrl, UDEV_CTRL_PING, 0, NULL, timeout);
}

int udev_ctrl_send_exit(struct udev_ctrl *uctrl, usec_t timeout) {
        return ctrl_send(uctrl, UDEV_CTRL_EXIT, 0, NULL, timeout);
}

struct udev_ctrl_msg *udev_ctrl_receive_msg(struct udev_ctrl_connection *conn) {
        struct udev_ctrl_msg *uctrl_msg;
        ssize_t size;
        struct cmsghdr *cmsg;
        struct iovec iov;
        char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
        struct msghdr smsg = {
                .msg_iov = &iov,
                .msg_iovlen = 1,
                .msg_control = cred_msg,
                .msg_controllen = sizeof(cred_msg),
        };
        struct ucred *cred;

        uctrl_msg = new0(struct udev_ctrl_msg, 1);
        if (!uctrl_msg)
                return NULL;
        uctrl_msg->n_ref = 1;
        uctrl_msg->conn = conn;
        udev_ctrl_connection_ref(conn);

        /* wait for the incoming message */
        for (;;) {
                struct pollfd pfd[1];
                int r;

                pfd[0].fd = conn->sock;
                pfd[0].events = POLLIN;

                r = poll(pfd, 1, 10000);
                if (r < 0) {
                        if (errno == EINTR)
                                continue;
                        goto err;
                } else if (r == 0) {
                        log_error("Timeout waiting for ctrl message");
                        goto err;
                } else {
                        if (!(pfd[0].revents & POLLIN)) {
                                log_error("Invalid ctrl connection: %m");
                                goto err;
                        }
                }

                break;
        }

        iov = IOVEC_MAKE(&uctrl_msg->ctrl_msg_wire, sizeof(struct udev_ctrl_msg_wire));

        size = recvmsg(conn->sock, &smsg, 0);
        if (size < 0) {
                log_error_errno(errno, "Failed to receive ctrl message: %m");
                goto err;
        }

        cmsg_close_all(&smsg);

        cmsg = CMSG_FIRSTHDR(&smsg);

        if (!cmsg || cmsg->cmsg_type != SCM_CREDENTIALS) {
                log_error("No sender credentials received, ignoring message");
                goto err;
        }

        cred = (struct ucred *) CMSG_DATA(cmsg);

        if (cred->uid != 0) {
                log_error("Sender uid="UID_FMT", ignoring message", cred->uid);
                goto err;
        }

        if (uctrl_msg->ctrl_msg_wire.magic != UDEV_CTRL_MAGIC) {
                log_error("Message magic 0x%08x doesn't match, ignoring", uctrl_msg->ctrl_msg_wire.magic);
                goto err;
        }

        return uctrl_msg;
err:
        udev_ctrl_msg_unref(uctrl_msg);
        return NULL;
}

static struct udev_ctrl_msg *udev_ctrl_msg_free(struct udev_ctrl_msg *ctrl_msg) {
        assert(ctrl_msg);

        udev_ctrl_connection_unref(ctrl_msg->conn);
        return mfree(ctrl_msg);
}

DEFINE_TRIVIAL_UNREF_FUNC(struct udev_ctrl_msg, udev_ctrl_msg, udev_ctrl_msg_free);

int udev_ctrl_get_set_log_level(struct udev_ctrl_msg *ctrl_msg) {
        if (ctrl_msg->ctrl_msg_wire.type == UDEV_CTRL_SET_LOG_LEVEL)
                return ctrl_msg->ctrl_msg_wire.intval;
        return -1;
}

int udev_ctrl_get_stop_exec_queue(struct udev_ctrl_msg *ctrl_msg) {
        if (ctrl_msg->ctrl_msg_wire.type == UDEV_CTRL_STOP_EXEC_QUEUE)
                return 1;
        return -1;
}

int udev_ctrl_get_start_exec_queue(struct udev_ctrl_msg *ctrl_msg) {
        if (ctrl_msg->ctrl_msg_wire.type == UDEV_CTRL_START_EXEC_QUEUE)
                return 1;
        return -1;
}

int udev_ctrl_get_reload(struct udev_ctrl_msg *ctrl_msg) {
        if (ctrl_msg->ctrl_msg_wire.type == UDEV_CTRL_RELOAD)
                return 1;
        return -1;
}

const char *udev_ctrl_get_set_env(struct udev_ctrl_msg *ctrl_msg) {
        if (ctrl_msg->ctrl_msg_wire.type == UDEV_CTRL_SET_ENV)
                return ctrl_msg->ctrl_msg_wire.buf;
        return NULL;
}

int udev_ctrl_get_set_children_max(struct udev_ctrl_msg *ctrl_msg) {
        if (ctrl_msg->ctrl_msg_wire.type == UDEV_CTRL_SET_CHILDREN_MAX)
                return ctrl_msg->ctrl_msg_wire.intval;
        return -1;
}

int udev_ctrl_get_ping(struct udev_ctrl_msg *ctrl_msg) {
        if (ctrl_msg->ctrl_msg_wire.type == UDEV_CTRL_PING)
                return 1;
        return -1;
}

int udev_ctrl_get_exit(struct udev_ctrl_msg *ctrl_msg) {
        if (ctrl_msg->ctrl_msg_wire.type == UDEV_CTRL_EXIT)
                return 1;
        return -1;
}