src/udev/udev-ctrl.c - systemd - Git at Google

 /* SPDX-License-Identifier: LGPL-2.1-or-later */

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

 #include "sd-event.h"

 #include "alloc-util.h"
 #include "errno-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"

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

 typedef struct UdevCtrlMessageWire {
         char version[16];
         unsigned magic;
         UdevCtrlMessageType type;
         UdevCtrlMessageValue value;
 } UdevCtrlMessageWire;

 struct UdevCtrl {
         unsigned n_ref;
         int sock;
         int sock_connect;
         union sockaddr_union saddr;
         socklen_t addrlen;
         bool bound;
         bool connected;
         bool maybe_disconnected;
         sd_event *event;
         sd_event_source *event_source;
         sd_event_source *event_source_connect;
         udev_ctrl_handler_t callback;
         void *userdata;
 };

 int udev_ctrl_new_from_fd(UdevCtrl **ret, int fd) {
         _cleanup_close_ int sock = -EBADF;
         UdevCtrl *uctrl;

         assert(ret);

         if (fd < 0) {
                 sock = socket(AF_UNIX, SOCK_SEQPACKET|SOCK_NONBLOCK|SOCK_CLOEXEC, 0);
                 if (sock < 0)
                         return log_error_errno(errno, "Failed to create socket: %m");
         }

         uctrl = new(UdevCtrl, 1);
         if (!uctrl)
                 return -ENOMEM;

         *uctrl = (UdevCtrl) {
                 .n_ref = 1,
                 .sock = fd >= 0 ? fd : TAKE_FD(sock),
                 .sock_connect = -EBADF,
                 .bound = fd >= 0,
         };

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

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

         *ret = TAKE_PTR(uctrl);
         return 0;
 }

 int udev_ctrl_enable_receiving(UdevCtrl *uctrl) {
         assert(uctrl);

         if (uctrl->bound)
                 return 0;

         (void) sockaddr_un_unlink(&uctrl->saddr.un);
         if (bind(uctrl->sock, &uctrl->saddr.sa, uctrl->addrlen) < 0)
                 return log_error_errno(errno, "Failed to bind udev control socket: %m");

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

         uctrl->bound = true;
         return 0;
 }

 static void udev_ctrl_disconnect(UdevCtrl *uctrl) {
         if (!uctrl)
                 return;

         uctrl->event_source_connect = sd_event_source_unref(uctrl->event_source_connect);
         uctrl->sock_connect = safe_close(uctrl->sock_connect);
 }

 static UdevCtrl *udev_ctrl_free(UdevCtrl *uctrl) {
         assert(uctrl);

         udev_ctrl_disconnect(uctrl);

         sd_event_source_unref(uctrl->event_source);
         safe_close(uctrl->sock);

         sd_event_unref(uctrl->event);
         return mfree(uctrl);
 }

 DEFINE_TRIVIAL_REF_UNREF_FUNC(UdevCtrl, udev_ctrl, udev_ctrl_free);

 int udev_ctrl_attach_event(UdevCtrl *uctrl, sd_event *event) {
         int r;

         assert_return(uctrl, -EINVAL);
         assert_return(!uctrl->event, -EBUSY);

         if (event)
                 uctrl->event = sd_event_ref(event);
         else {
                 r = sd_event_default(&uctrl->event);
                 if (r < 0)
                         return r;
         }

         return 0;
 }

 sd_event_source *udev_ctrl_get_event_source(UdevCtrl *uctrl) {
         assert(uctrl);

         return uctrl->event_source;
 }

 static void udev_ctrl_disconnect_and_listen_again(UdevCtrl *uctrl) {
         udev_ctrl_disconnect(uctrl);
         udev_ctrl_unref(uctrl);
         (void) sd_event_source_set_enabled(uctrl->event_source, SD_EVENT_ON);
         /* We don't return NULL here because uctrl is not freed */
 }

 DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(UdevCtrl*, udev_ctrl_disconnect_and_listen_again, NULL);

 static int udev_ctrl_connection_event_handler(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
         _cleanup_(udev_ctrl_disconnect_and_listen_againp) UdevCtrl *uctrl = NULL;
         UdevCtrlMessageWire msg_wire;
         struct iovec iov = IOVEC_MAKE(&msg_wire, sizeof(UdevCtrlMessageWire));
         CMSG_BUFFER_TYPE(CMSG_SPACE(sizeof(struct ucred))) control;
         struct msghdr smsg = {
                 .msg_iov = &iov,
                 .msg_iovlen = 1,
                 .msg_control = &control,
                 .msg_controllen = sizeof(control),
         };
         struct cmsghdr *cmsg;
         struct ucred *cred;
         ssize_t size;

         assert(userdata);

         /* When UDEV_CTRL_EXIT is received, manager unref udev_ctrl object.
          * To avoid the object freed, let's increment the refcount. */
         uctrl = udev_ctrl_ref(userdata);

         size = next_datagram_size_fd(fd);
         if (size < 0)
                 return log_error_errno(size, "Failed to get size of message: %m");
         if (size == 0)
                 return 0; /* Client disconnects? */

         size = recvmsg_safe(fd, &smsg, 0);
         if (size == -EINTR)
                 return 0;
         if (size < 0)
                 return log_error_errno(size, "Failed to receive ctrl message: %m");

         cmsg_close_all(&smsg);

         cmsg = CMSG_FIRSTHDR(&smsg);

         if (!cmsg || cmsg->cmsg_type != SCM_CREDENTIALS) {
                 log_error("No sender credentials received, ignoring message");
                 return 0;
         }

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

         if (cred->uid != 0) {
                 log_error("Invalid sender uid "UID_FMT", ignoring message", cred->uid);
                 return 0;
         }

         if (msg_wire.magic != UDEV_CTRL_MAGIC) {
                 log_error("Message magic 0x%08x doesn't match, ignoring message", msg_wire.magic);
                 return 0;
         }

         if (msg_wire.type == _UDEV_CTRL_END_MESSAGES)
                 return 0;

         if (uctrl->callback)
                 (void) uctrl->callback(uctrl, msg_wire.type, &msg_wire.value, uctrl->userdata);

         /* Do not disconnect and wait for next message. */
         uctrl = udev_ctrl_unref(uctrl);
         return 0;
 }

 static int udev_ctrl_event_handler(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
         UdevCtrl *uctrl = ASSERT_PTR(userdata);
         _cleanup_close_ int sock = -EBADF;
         struct ucred ucred;
         int r;

         sock = accept4(fd, NULL, NULL, SOCK_CLOEXEC|SOCK_NONBLOCK);
         if (sock < 0) {
                 if (ERRNO_IS_ACCEPT_AGAIN(errno))
                         return 0;

                 return log_error_errno(errno, "Failed to accept ctrl connection: %m");
         }

         /* check peer credential of connection */
         r = getpeercred(sock, &ucred);
         if (r < 0) {
                 log_error_errno(r, "Failed to receive credentials of ctrl connection: %m");
                 return 0;
         }

         if (ucred.uid > 0) {
                 log_error("Invalid sender uid "UID_FMT", closing connection", ucred.uid);
                 return 0;
         }

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

         r = sd_event_add_io(uctrl->event, &uctrl->event_source_connect, sock, EPOLLIN, udev_ctrl_connection_event_handler, uctrl);
         if (r < 0) {
                 log_error_errno(r, "Failed to create event source for udev control connection: %m");
                 return 0;
         }

         (void) sd_event_source_set_description(uctrl->event_source_connect, "udev-ctrl-connection");

         /* Do not accept multiple connection. */
         (void) sd_event_source_set_enabled(uctrl->event_source, SD_EVENT_OFF);

         uctrl->sock_connect = TAKE_FD(sock);
         return 0;
 }

 int udev_ctrl_start(UdevCtrl *uctrl, udev_ctrl_handler_t callback, void *userdata) {
         int r;

         assert(uctrl);

         if (!uctrl->event) {
                 r = udev_ctrl_attach_event(uctrl, NULL);
                 if (r < 0)
                         return r;
         }

         r = udev_ctrl_enable_receiving(uctrl);
         if (r < 0)
                 return r;

         uctrl->callback = callback;
         uctrl->userdata = userdata;

         r = sd_event_add_io(uctrl->event, &uctrl->event_source, uctrl->sock, EPOLLIN, udev_ctrl_event_handler, uctrl);
         if (r < 0)
                 return r;

         (void) sd_event_source_set_description(uctrl->event_source, "udev-ctrl");

         return 0;
 }

 int udev_ctrl_send(UdevCtrl *uctrl, UdevCtrlMessageType type, const void *data) {
         UdevCtrlMessageWire ctrl_msg_wire = {
                 .version = "udev-" STRINGIFY(PROJECT_VERSION),
                 .magic = UDEV_CTRL_MAGIC,
                 .type = type,
         };

         if (uctrl->maybe_disconnected)
                 return -ENOANO; /* to distinguish this from other errors. */

         if (type == UDEV_CTRL_SET_ENV) {
                 assert(data);
                 strscpy(ctrl_msg_wire.value.buf, sizeof(ctrl_msg_wire.value.buf), data);
         } else if (IN_SET(type, UDEV_CTRL_SET_LOG_LEVEL, UDEV_CTRL_SET_CHILDREN_MAX))
                 ctrl_msg_wire.value.intval = PTR_TO_INT(data);

         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;

         if (type == UDEV_CTRL_EXIT)
                 uctrl->maybe_disconnected = true;

         return 0;
 }

 int udev_ctrl_wait(UdevCtrl *uctrl, usec_t timeout) {
         _cleanup_(sd_event_source_disable_unrefp) sd_event_source *source_io = NULL, *source_timeout = NULL;
         int r;

         assert(uctrl);

         if (uctrl->sock < 0)
                 return 0;
         if (!uctrl->connected)
                 return 0;

         if (!uctrl->maybe_disconnected) {
                 r = udev_ctrl_send(uctrl, _UDEV_CTRL_END_MESSAGES, NULL);
                 if (r < 0)
                         return r;
         }

         if (timeout == 0)
                 return 0;

         if (!uctrl->event) {
                 r = udev_ctrl_attach_event(uctrl, NULL);
                 if (r < 0)
                         return r;
         }

         r = sd_event_add_io(uctrl->event, &source_io, uctrl->sock, EPOLLIN, NULL, INT_TO_PTR(0));
         if (r < 0)
                 return r;

         (void) sd_event_source_set_description(source_io, "udev-ctrl-wait-io");

         if (timeout != USEC_INFINITY) {
                 r = sd_event_add_time_relative(
                                 uctrl->event, &source_timeout, CLOCK_BOOTTIME,
                                 timeout,
                                 0, NULL, INT_TO_PTR(-ETIMEDOUT));
                 if (r < 0)
                         return r;

                 (void) sd_event_source_set_description(source_timeout, "udev-ctrl-wait-timeout");
         }

         return sd_event_loop(uctrl->event);
 }
	/* SPDX-License-Identifier: LGPL-2.1-or-later */

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

	#include "sd-event.h"

	#include "alloc-util.h"
	#include "errno-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"

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

	typedef struct UdevCtrlMessageWire {
	char version[16];
	unsigned magic;
	UdevCtrlMessageType type;
	UdevCtrlMessageValue value;
	} UdevCtrlMessageWire;

	struct UdevCtrl {
	unsigned n_ref;
	int sock;
	int sock_connect;
	union sockaddr_union saddr;
	socklen_t addrlen;
	bool bound;
	bool connected;
	bool maybe_disconnected;
	sd_event *event;
	sd_event_source *event_source;
	sd_event_source *event_source_connect;
	udev_ctrl_handler_t callback;
	void *userdata;
	};

	int udev_ctrl_new_from_fd(UdevCtrl **ret, int fd) {
	_cleanup_close_ int sock = -EBADF;
	UdevCtrl *uctrl;

	assert(ret);

	if (fd < 0) {
	sock = socket(AF_UNIX, SOCK_SEQPACKET\|SOCK_NONBLOCK\|SOCK_CLOEXEC, 0);
	if (sock < 0)
	return log_error_errno(errno, "Failed to create socket: %m");
	}

	uctrl = new(UdevCtrl, 1);
	if (!uctrl)
	return -ENOMEM;

	*uctrl = (UdevCtrl) {
	.n_ref = 1,
	.sock = fd >= 0 ? fd : TAKE_FD(sock),
	.sock_connect = -EBADF,
	.bound = fd >= 0,
	};

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

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

	*ret = TAKE_PTR(uctrl);
	return 0;
	}

	int udev_ctrl_enable_receiving(UdevCtrl *uctrl) {
	assert(uctrl);

	if (uctrl->bound)
	return 0;

	(void) sockaddr_un_unlink(&uctrl->saddr.un);
	if (bind(uctrl->sock, &uctrl->saddr.sa, uctrl->addrlen) < 0)
	return log_error_errno(errno, "Failed to bind udev control socket: %m");

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

	uctrl->bound = true;
	return 0;
	}

	static void udev_ctrl_disconnect(UdevCtrl *uctrl) {
	if (!uctrl)
	return;

	uctrl->event_source_connect = sd_event_source_unref(uctrl->event_source_connect);
	uctrl->sock_connect = safe_close(uctrl->sock_connect);
	}

	static UdevCtrl udev_ctrl_free(UdevCtrl uctrl) {
	assert(uctrl);

	udev_ctrl_disconnect(uctrl);

	sd_event_source_unref(uctrl->event_source);
	safe_close(uctrl->sock);

	sd_event_unref(uctrl->event);
	return mfree(uctrl);
	}

	DEFINE_TRIVIAL_REF_UNREF_FUNC(UdevCtrl, udev_ctrl, udev_ctrl_free);

	int udev_ctrl_attach_event(UdevCtrl uctrl, sd_event event) {
	int r;

	assert_return(uctrl, -EINVAL);
	assert_return(!uctrl->event, -EBUSY);

	if (event)
	uctrl->event = sd_event_ref(event);
	else {
	r = sd_event_default(&uctrl->event);
	if (r < 0)
	return r;
	}

	return 0;
	}

	sd_event_source udev_ctrl_get_event_source(UdevCtrl uctrl) {
	assert(uctrl);

	return uctrl->event_source;
	}

	static void udev_ctrl_disconnect_and_listen_again(UdevCtrl *uctrl) {
	udev_ctrl_disconnect(uctrl);
	udev_ctrl_unref(uctrl);
	(void) sd_event_source_set_enabled(uctrl->event_source, SD_EVENT_ON);
	/* We don't return NULL here because uctrl is not freed */
	}

	DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(UdevCtrl*, udev_ctrl_disconnect_and_listen_again, NULL);

	static int udev_ctrl_connection_event_handler(sd_event_source s, int fd, uint32_t revents, void userdata) {
	_cleanup_(udev_ctrl_disconnect_and_listen_againp) UdevCtrl *uctrl = NULL;
	UdevCtrlMessageWire msg_wire;
	struct iovec iov = IOVEC_MAKE(&msg_wire, sizeof(UdevCtrlMessageWire));
	CMSG_BUFFER_TYPE(CMSG_SPACE(sizeof(struct ucred))) control;
	struct msghdr smsg = {
	.msg_iov = &iov,
	.msg_iovlen = 1,
	.msg_control = &control,
	.msg_controllen = sizeof(control),
	};
	struct cmsghdr *cmsg;
	struct ucred *cred;
	ssize_t size;

	assert(userdata);

	/* When UDEV_CTRL_EXIT is received, manager unref udev_ctrl object.
	* To avoid the object freed, let's increment the refcount. */
	uctrl = udev_ctrl_ref(userdata);

	size = next_datagram_size_fd(fd);
	if (size < 0)
	return log_error_errno(size, "Failed to get size of message: %m");
	if (size == 0)
	return 0; /* Client disconnects? */

	size = recvmsg_safe(fd, &smsg, 0);
	if (size == -EINTR)
	return 0;
	if (size < 0)
	return log_error_errno(size, "Failed to receive ctrl message: %m");

	cmsg_close_all(&smsg);

	cmsg = CMSG_FIRSTHDR(&smsg);

	if (!cmsg \|\| cmsg->cmsg_type != SCM_CREDENTIALS) {
	log_error("No sender credentials received, ignoring message");
	return 0;
	}

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

	if (cred->uid != 0) {
	log_error("Invalid sender uid "UID_FMT", ignoring message", cred->uid);
	return 0;
	}

	if (msg_wire.magic != UDEV_CTRL_MAGIC) {
	log_error("Message magic 0x%08x doesn't match, ignoring message", msg_wire.magic);
	return 0;
	}

	if (msg_wire.type == _UDEV_CTRL_END_MESSAGES)
	return 0;

	if (uctrl->callback)
	(void) uctrl->callback(uctrl, msg_wire.type, &msg_wire.value, uctrl->userdata);

	/* Do not disconnect and wait for next message. */
	uctrl = udev_ctrl_unref(uctrl);
	return 0;
	}

	static int udev_ctrl_event_handler(sd_event_source s, int fd, uint32_t revents, void userdata) {
	UdevCtrl *uctrl = ASSERT_PTR(userdata);
	_cleanup_close_ int sock = -EBADF;
	struct ucred ucred;
	int r;

	sock = accept4(fd, NULL, NULL, SOCK_CLOEXEC\|SOCK_NONBLOCK);
	if (sock < 0) {
	if (ERRNO_IS_ACCEPT_AGAIN(errno))
	return 0;

	return log_error_errno(errno, "Failed to accept ctrl connection: %m");
	}

	/* check peer credential of connection */
	r = getpeercred(sock, &ucred);
	if (r < 0) {
	log_error_errno(r, "Failed to receive credentials of ctrl connection: %m");
	return 0;
	}

	if (ucred.uid > 0) {
	log_error("Invalid sender uid "UID_FMT", closing connection", ucred.uid);
	return 0;
	}

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

	r = sd_event_add_io(uctrl->event, &uctrl->event_source_connect, sock, EPOLLIN, udev_ctrl_connection_event_handler, uctrl);
	if (r < 0) {
	log_error_errno(r, "Failed to create event source for udev control connection: %m");
	return 0;
	}

	(void) sd_event_source_set_description(uctrl->event_source_connect, "udev-ctrl-connection");

	/* Do not accept multiple connection. */
	(void) sd_event_source_set_enabled(uctrl->event_source, SD_EVENT_OFF);

	uctrl->sock_connect = TAKE_FD(sock);
	return 0;
	}

	int udev_ctrl_start(UdevCtrl uctrl, udev_ctrl_handler_t callback, void userdata) {
	int r;

	assert(uctrl);

	if (!uctrl->event) {
	r = udev_ctrl_attach_event(uctrl, NULL);
	if (r < 0)
	return r;
	}

	r = udev_ctrl_enable_receiving(uctrl);
	if (r < 0)
	return r;

	uctrl->callback = callback;
	uctrl->userdata = userdata;

	r = sd_event_add_io(uctrl->event, &uctrl->event_source, uctrl->sock, EPOLLIN, udev_ctrl_event_handler, uctrl);
	if (r < 0)
	return r;

	(void) sd_event_source_set_description(uctrl->event_source, "udev-ctrl");

	return 0;
	}

	int udev_ctrl_send(UdevCtrl uctrl, UdevCtrlMessageType type, const void data) {
	UdevCtrlMessageWire ctrl_msg_wire = {
	.version = "udev-" STRINGIFY(PROJECT_VERSION),
	.magic = UDEV_CTRL_MAGIC,
	.type = type,
	};

	if (uctrl->maybe_disconnected)
	return -ENOANO; /* to distinguish this from other errors. */

	if (type == UDEV_CTRL_SET_ENV) {
	assert(data);
	strscpy(ctrl_msg_wire.value.buf, sizeof(ctrl_msg_wire.value.buf), data);
	} else if (IN_SET(type, UDEV_CTRL_SET_LOG_LEVEL, UDEV_CTRL_SET_CHILDREN_MAX))
	ctrl_msg_wire.value.intval = PTR_TO_INT(data);

	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;

	if (type == UDEV_CTRL_EXIT)
	uctrl->maybe_disconnected = true;

	return 0;
	}

	int udev_ctrl_wait(UdevCtrl *uctrl, usec_t timeout) {
	_cleanup_(sd_event_source_disable_unrefp) sd_event_source source_io = NULL, source_timeout = NULL;
	int r;

	assert(uctrl);

	if (uctrl->sock < 0)
	return 0;
	if (!uctrl->connected)
	return 0;

	if (!uctrl->maybe_disconnected) {
	r = udev_ctrl_send(uctrl, _UDEV_CTRL_END_MESSAGES, NULL);
	if (r < 0)
	return r;
	}

	if (timeout == 0)
	return 0;

	if (!uctrl->event) {
	r = udev_ctrl_attach_event(uctrl, NULL);
	if (r < 0)
	return r;
	}

	r = sd_event_add_io(uctrl->event, &source_io, uctrl->sock, EPOLLIN, NULL, INT_TO_PTR(0));
	if (r < 0)
	return r;

	(void) sd_event_source_set_description(source_io, "udev-ctrl-wait-io");

	if (timeout != USEC_INFINITY) {
	r = sd_event_add_time_relative(
	uctrl->event, &source_timeout, CLOCK_BOOTTIME,
	timeout,
	0, NULL, INT_TO_PTR(-ETIMEDOUT));
	if (r < 0)
	return r;

	(void) sd_event_source_set_description(source_timeout, "udev-ctrl-wait-timeout");
	}

	return sd_event_loop(uctrl->event);
	}