source: vendor/current/source3/lib/messages_dgm.c

/*
 * Unix SMB/CIFS implementation.
 * Samba internal messaging functions
 * Copyright (C) 2013 by Volker Lendecke
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "replace.h"
#include "system/network.h"
#include "system/filesys.h"
#include <dirent.h>
#include "lib/util/data_blob.h"
#include "lib/util/debug.h"
#include "lib/unix_msg/unix_msg.h"
#include "system/filesys.h"
#include "lib/messages_dgm.h"
#include "lib/param/param.h"
#include "poll_funcs/poll_funcs_tevent.h"
#include "unix_msg/unix_msg.h"
#include "lib/util/genrand.h"

struct sun_path_buf {
        /*
         * This will carry enough for a socket path
         */
        char buf[sizeof(struct sockaddr_un)];
};

struct messaging_dgm_context {
        pid_t pid;
        struct poll_funcs *msg_callbacks;
        void *tevent_handle;
        struct unix_msg_ctx *dgm_ctx;
        struct sun_path_buf socket_dir;
        struct sun_path_buf lockfile_dir;
        int lockfile_fd;

        void (*recv_cb)(const uint8_t *msg,
                        size_t msg_len,
                        int *fds,
                        size_t num_fds,
                        void *private_data);
        void *recv_cb_private_data;

        bool *have_dgm_context;
};

static struct messaging_dgm_context *global_dgm_context;

static void messaging_dgm_recv(struct unix_msg_ctx *ctx,
                               uint8_t *msg, size_t msg_len,
                               int *fds, size_t num_fds,
                               void *private_data);

static int messaging_dgm_context_destructor(struct messaging_dgm_context *c);

static int messaging_dgm_lockfile_create(struct messaging_dgm_context *ctx,
                                         pid_t pid, int *plockfile_fd,
                                         uint64_t *punique)
{
        char buf[64];
        int lockfile_fd;
        struct sun_path_buf lockfile_name;
        struct flock lck;
        uint64_t unique;
        int unique_len, ret;
        ssize_t written;

        ret = snprintf(lockfile_name.buf, sizeof(lockfile_name.buf),
                       "%s/%u", ctx->lockfile_dir.buf, (unsigned)pid);
        if (ret >= sizeof(lockfile_name.buf)) {
                return ENAMETOOLONG;
        }

        /* no O_EXCL, existence check is via the fcntl lock */

        lockfile_fd = open(lockfile_name.buf, O_NONBLOCK|O_CREAT|O_RDWR,
                           0644);

        if ((lockfile_fd == -1) &&
            ((errno == ENXIO) /* Linux */ ||
             (errno == ENODEV) /* Linux kernel bug */ ||
             (errno == EOPNOTSUPP) /* FreeBSD */)) {
                /*
                 * Huh -- a socket? This might be a stale socket from
                 * an upgrade of Samba. Just unlink and retry, nobody
                 * else is supposed to be here at this time.
                 *
                 * Yes, this is racy, but I don't see a way to deal
                 * with this properly.
                 */
                unlink(lockfile_name.buf);

                lockfile_fd = open(lockfile_name.buf,
                                   O_NONBLOCK|O_CREAT|O_WRONLY,
                                   0644);
        }

        if (lockfile_fd == -1) {
                ret = errno;
                DEBUG(1, ("%s: open failed: %s\n", __func__, strerror(errno)));
                return ret;
        }

        lck = (struct flock) {
                .l_type = F_WRLCK,
                .l_whence = SEEK_SET
        };

        ret = fcntl(lockfile_fd, F_SETLK, &lck);
        if (ret == -1) {
                ret = errno;
                DEBUG(1, ("%s: fcntl failed: %s\n", __func__, strerror(ret)));
                goto fail_close;
        }

        /*
         * Directly using the binary value for
         * SERVERID_UNIQUE_ID_NOT_TO_VERIFY is a layering
         * violation. But including all of ndr here just for this
         * seems to be a bit overkill to me. Also, messages_dgm might
         * be replaced sooner or later by something streams-based,
         * where unique_id generation will be handled differently.
         */

        do {
                generate_random_buffer((uint8_t *)&unique, sizeof(unique));
        } while (unique == UINT64_C(0xFFFFFFFFFFFFFFFF));

        unique_len = snprintf(buf, sizeof(buf), "%ju\n", (uintmax_t)unique);

        /* shorten a potentially preexisting file */

        ret = ftruncate(lockfile_fd, unique_len);
        if (ret == -1) {
                ret = errno;
                DEBUG(1, ("%s: ftruncate failed: %s\n", __func__,
                          strerror(ret)));
                goto fail_unlink;
        }

        written = write(lockfile_fd, buf, unique_len);
        if (written != unique_len) {
                ret = errno;
                DEBUG(1, ("%s: write failed: %s\n", __func__, strerror(ret)));
                goto fail_unlink;
        }

        *plockfile_fd = lockfile_fd;
        *punique = unique;
        return 0;

fail_unlink:
        unlink(lockfile_name.buf);
fail_close:
        close(lockfile_fd);
        return ret;
}

int messaging_dgm_init(struct tevent_context *ev,
                       uint64_t *punique,
                       const char *socket_dir,
                       const char *lockfile_dir,
                       void (*recv_cb)(const uint8_t *msg,
                                       size_t msg_len,
                                       int *fds,
                                       size_t num_fds,
                                       void *private_data),
                       void *recv_cb_private_data)
{
        struct messaging_dgm_context *ctx;
        int ret;
        struct sockaddr_un socket_address;
        size_t len;
        static bool have_dgm_context = false;

        if (have_dgm_context) {
                return EEXIST;
        }

        ctx = talloc_zero(NULL, struct messaging_dgm_context);
        if (ctx == NULL) {
                goto fail_nomem;
        }
        ctx->pid = getpid();
        ctx->recv_cb = recv_cb;
        ctx->recv_cb_private_data = recv_cb_private_data;

        len = strlcpy(ctx->lockfile_dir.buf, lockfile_dir,
                      sizeof(ctx->lockfile_dir.buf));
        if (len >= sizeof(ctx->lockfile_dir.buf)) {
                TALLOC_FREE(ctx);
                return ENAMETOOLONG;
        }

        len = strlcpy(ctx->socket_dir.buf, socket_dir,
                      sizeof(ctx->socket_dir.buf));
        if (len >= sizeof(ctx->socket_dir.buf)) {
                TALLOC_FREE(ctx);
                return ENAMETOOLONG;
        }

        socket_address = (struct sockaddr_un) { .sun_family = AF_UNIX };
        len = snprintf(socket_address.sun_path,
                       sizeof(socket_address.sun_path),
                       "%s/%u", socket_dir, (unsigned)ctx->pid);
        if (len >= sizeof(socket_address.sun_path)) {
                TALLOC_FREE(ctx);
                return ENAMETOOLONG;
        }

        ret = messaging_dgm_lockfile_create(ctx, ctx->pid, &ctx->lockfile_fd,
                                            punique);
        if (ret != 0) {
                DEBUG(1, ("%s: messaging_dgm_create_lockfile failed: %s\n",
                          __func__, strerror(ret)));
                TALLOC_FREE(ctx);
                return ret;
        }

        ctx->msg_callbacks = poll_funcs_init_tevent(ctx);
        if (ctx->msg_callbacks == NULL) {
                goto fail_nomem;
        }

        ctx->tevent_handle = poll_funcs_tevent_register(
                ctx, ctx->msg_callbacks, ev);
        if (ctx->tevent_handle == NULL) {
                goto fail_nomem;
        }

        unlink(socket_address.sun_path);

        ret = unix_msg_init(&socket_address, ctx->msg_callbacks, 1024,
                            messaging_dgm_recv, ctx, &ctx->dgm_ctx);
        if (ret != 0) {
                DEBUG(1, ("unix_msg_init failed: %s\n", strerror(ret)));
                TALLOC_FREE(ctx);
                return ret;
        }
        talloc_set_destructor(ctx, messaging_dgm_context_destructor);

        ctx->have_dgm_context = &have_dgm_context;

        global_dgm_context = ctx;
        return 0;

fail_nomem:
        TALLOC_FREE(ctx);
        return ENOMEM;
}

static int messaging_dgm_context_destructor(struct messaging_dgm_context *c)
{
        /*
         * First delete the socket to avoid races. The lockfile is the
         * indicator that we're still around.
         */
        unix_msg_free(c->dgm_ctx);

        if (getpid() == c->pid) {
                struct sun_path_buf name;
                int ret;

                ret = snprintf(name.buf, sizeof(name.buf), "%s/%u",
                               c->lockfile_dir.buf, (unsigned)c->pid);
                if (ret >= sizeof(name.buf)) {
                        /*
                         * We've checked the length when creating, so this
                         * should never happen
                         */
                        abort();
                }
                unlink(name.buf);
        }
        close(c->lockfile_fd);

        if (c->have_dgm_context != NULL) {
                *c->have_dgm_context = false;
        }

        return 0;
}

void messaging_dgm_destroy(void)
{
        TALLOC_FREE(global_dgm_context);
}

int messaging_dgm_send(pid_t pid,
                       const struct iovec *iov, int iovlen,
                       const int *fds, size_t num_fds)
{
        struct messaging_dgm_context *ctx = global_dgm_context;
        struct sockaddr_un dst;
        ssize_t dst_pathlen;
        int ret;

        if (ctx == NULL) {
                return ENOTCONN;
        }

        dst = (struct sockaddr_un) { .sun_family = AF_UNIX };

        dst_pathlen = snprintf(dst.sun_path, sizeof(dst.sun_path),
                               "%s/%u", ctx->socket_dir.buf, (unsigned)pid);
        if (dst_pathlen >= sizeof(dst.sun_path)) {
                return ENAMETOOLONG;
        }

        DEBUG(10, ("%s: Sending message to %u\n", __func__, (unsigned)pid));

        ret = unix_msg_send(ctx->dgm_ctx, &dst, iov, iovlen, fds, num_fds);

        return ret;
}

static void messaging_dgm_recv(struct unix_msg_ctx *ctx,
                               uint8_t *msg, size_t msg_len,
                               int *fds, size_t num_fds,
                               void *private_data)
{
        struct messaging_dgm_context *dgm_ctx = talloc_get_type_abort(
                private_data, struct messaging_dgm_context);

        dgm_ctx->recv_cb(msg, msg_len, fds, num_fds,
                         dgm_ctx->recv_cb_private_data);
}

static int messaging_dgm_read_unique(int fd, uint64_t *punique)
{
        char buf[25];
        ssize_t rw_ret;
        unsigned long long unique;
        char *endptr;

        rw_ret = pread(fd, buf, sizeof(buf)-1, 0);
        if (rw_ret == -1) {
                return errno;
        }
        buf[rw_ret] = '\0';

        unique = strtoull(buf, &endptr, 10);
        if ((unique == 0) && (errno == EINVAL)) {
                return EINVAL;
        }
        if ((unique == ULLONG_MAX) && (errno == ERANGE)) {
                return ERANGE;
        }
        if (endptr[0] != '\n') {
                return EINVAL;
        }
        *punique = unique;
        return 0;
}

int messaging_dgm_get_unique(pid_t pid, uint64_t *unique)
{
        struct messaging_dgm_context *ctx = global_dgm_context;
        struct sun_path_buf lockfile_name;
        int ret, fd;

        if (ctx == NULL) {
                return EBADF;
        }

        if (pid == getpid()) {
                /*
                 * Protect against losing our own lock
                 */
                return messaging_dgm_read_unique(ctx->lockfile_fd, unique);
        }

        ret = snprintf(lockfile_name.buf, sizeof(lockfile_name.buf),
                       "%s/%u", ctx->lockfile_dir.buf, (int)pid);
        if (ret >= sizeof(lockfile_name.buf)) {
                return ENAMETOOLONG;
        }

        fd = open(lockfile_name.buf, O_NONBLOCK|O_RDONLY, 0);
        if (fd == -1) {
                return errno;
        }

        ret = messaging_dgm_read_unique(fd, unique);
        close(fd);
        return ret;
}

int messaging_dgm_cleanup(pid_t pid)
{
        struct messaging_dgm_context *ctx = global_dgm_context;
        struct sun_path_buf lockfile_name, socket_name;
        int fd, len, ret;
        struct flock lck = {};

        if (ctx == NULL) {
                return ENOTCONN;
        }

        len = snprintf(socket_name.buf, sizeof(socket_name.buf), "%s/%u",
                       ctx->socket_dir.buf, (unsigned)pid);
        if (len >= sizeof(socket_name.buf)) {
                return ENAMETOOLONG;
        }

        len = snprintf(lockfile_name.buf, sizeof(lockfile_name.buf), "%s/%u",
                       ctx->lockfile_dir.buf, (unsigned)pid);
        if (len >= sizeof(lockfile_name.buf)) {
                return ENAMETOOLONG;
        }

        fd = open(lockfile_name.buf, O_NONBLOCK|O_WRONLY, 0);
        if (fd == -1) {
                ret = errno;
                if (ret != ENOENT) {
                        DEBUG(10, ("%s: open(%s) failed: %s\n", __func__,
                                   lockfile_name.buf, strerror(ret)));
                }
                return ret;
        }

        lck.l_type = F_WRLCK;
        lck.l_whence = SEEK_SET;
        lck.l_start = 0;
        lck.l_len = 0;

        ret = fcntl(fd, F_SETLK, &lck);
        if (ret != 0) {
                ret = errno;
                if ((ret != EACCES) && (ret != EAGAIN)) {
                        DEBUG(10, ("%s: Could not get lock: %s\n", __func__,
                                   strerror(ret)));
                }
                close(fd);
                return ret;
        }

        DEBUG(10, ("%s: Cleaning up : %s\n", __func__, strerror(ret)));

        (void)unlink(socket_name.buf);
        (void)unlink(lockfile_name.buf);
        (void)close(fd);
        return 0;
}

int messaging_dgm_wipe(void)
{
        struct messaging_dgm_context *ctx = global_dgm_context;
        DIR *msgdir;
        struct dirent *dp;
        pid_t our_pid = getpid();
        int ret;

        if (ctx == NULL) {
                return ENOTCONN;
        }

        /*
         * We scan the socket directory and not the lock directory. Otherwise
         * we would race against messaging_dgm_lockfile_create's open(O_CREAT)
         * and fcntl(SETLK).
         */

        msgdir = opendir(ctx->socket_dir.buf);
        if (msgdir == NULL) {
                return errno;
        }

        while ((dp = readdir(msgdir)) != NULL) {
                unsigned long pid;

                pid = strtoul(dp->d_name, NULL, 10);
                if (pid == 0) {
                        /*
                         * . and .. and other malformed entries
                         */
                        continue;
                }
                if (pid == our_pid) {
                        /*
                         * fcntl(F_GETLK) will succeed for ourselves, we hold
                         * that lock ourselves.
                         */
                        continue;
                }

                ret = messaging_dgm_cleanup(pid);
                DEBUG(10, ("messaging_dgm_cleanup(%lu) returned %s\n",
                           pid, ret ? strerror(ret) : "ok"));
        }
        closedir(msgdir);

        return 0;
}

void *messaging_dgm_register_tevent_context(TALLOC_CTX *mem_ctx,
                                            struct tevent_context *ev)
{
        struct messaging_dgm_context *ctx = global_dgm_context;

        if (ctx == NULL) {
                return NULL;
        }
        return poll_funcs_tevent_register(mem_ctx, ctx->msg_callbacks, ev);
}