--- /dev/null
+/*
+ * Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
+ * Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * 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; only version 2 of the License.
+ *
+ * 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, write to the Free Software Foundation, Inc., 59 Temple
+ * Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/wait.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sched.h>
+#include <sys/mman.h>
+
+#include <lttngerr.h>
+
+#define CHILD_STACK_SIZE 10485760
+
+struct run_as_data {
+ int (*cmd)(void *data);
+ void *data;
+ uid_t uid;
+ gid_t gid;
+ int retval_pipe;
+};
+
+struct mkdir_data {
+ const char *path;
+ mode_t mode;
+};
+
+struct open_data {
+ const char *path;
+ int flags;
+ mode_t mode;
+};
+
+/*
+ * Create recursively directory using the FULL path.
+ */
+static
+int _mkdir_recursive(void *_data)
+{
+ struct mkdir_data *data = _data;
+ const char *path;
+ char *p, tmp[PATH_MAX];
+ struct stat statbuf;
+ mode_t mode;
+ size_t len;
+ int ret;
+
+ path = data->path;
+ mode = data->mode;
+
+ ret = snprintf(tmp, sizeof(tmp), "%s", path);
+ if (ret < 0) {
+ PERROR("snprintf mkdir");
+ goto error;
+ }
+
+ len = ret;
+ if (tmp[len - 1] == '/') {
+ tmp[len - 1] = 0;
+ }
+
+ for (p = tmp + 1; *p; p++) {
+ if (*p == '/') {
+ *p = 0;
+ ret = stat(tmp, &statbuf);
+ if (ret < 0) {
+ ret = mkdir(tmp, mode);
+ if (ret < 0) {
+ if (!(errno == EEXIST)) {
+ PERROR("mkdir recursive");
+ ret = -errno;
+ goto error;
+ }
+ }
+ }
+ *p = '/';
+ }
+ }
+
+ ret = mkdir(tmp, mode);
+ if (ret < 0) {
+ if (!(errno == EEXIST)) {
+ PERROR("mkdir recursive last piece");
+ ret = -errno;
+ } else {
+ ret = 0;
+ }
+ }
+
+error:
+ return ret;
+}
+
+static
+int _mkdir(void *_data)
+{
+ struct mkdir_data *data = _data;
+ return mkdir(data->path, data->mode);
+}
+
+static
+int _open(void *_data)
+{
+ struct open_data *data = _data;
+ return open(data->path, data->flags, data->mode);
+}
+
+static
+int child_run_as(void *_data)
+{
+ struct run_as_data *data = _data;
+ size_t writelen, writeleft, index;
+ union {
+ int i;
+ char c[sizeof(int)];
+ } sendret;
+ int ret;
+
+ /*
+ * Child: it is safe to drop egid and euid while sharing the
+ * file descriptors with the parent process, since we do not
+ * drop "uid": therefore, the user we are dropping egid/euid to
+ * cannot attach to this process with, e.g. ptrace, nor map this
+ * process memory.
+ */
+ if (data->gid != getegid()) {
+ ret = setegid(data->gid);
+ if (ret < 0) {
+ perror("setegid");
+ return EXIT_FAILURE;
+ }
+ }
+ if (data->uid != geteuid()) {
+ ret = seteuid(data->uid);
+ if (ret < 0) {
+ perror("seteuid");
+ return EXIT_FAILURE;
+ }
+ }
+ /*
+ * Also set umask to 0 for mkdir executable bit.
+ */
+ umask(0);
+ sendret.i = (*data->cmd)(data->data);
+ /* send back return value */
+ writeleft = sizeof(sendret);
+ index = 0;
+ do {
+ writelen = write(data->retval_pipe, &sendret.c[index],
+ writeleft);
+ if (writelen < 0) {
+ perror("write");
+ return EXIT_FAILURE;
+ }
+ writeleft -= writelen;
+ index += writelen;
+ } while (writeleft > 0);
+ return EXIT_SUCCESS;
+}
+
+static
+int run_as(int (*cmd)(void *data), void *data, uid_t uid, gid_t gid)
+{
+ struct run_as_data run_as_data;
+ int ret = 0;
+ int status;
+ pid_t pid;
+ int retval_pipe[2];
+ ssize_t readlen, readleft, index;
+ void *child_stack;
+ union {
+ int i;
+ char c[sizeof(int)];
+ } retval;
+
+ /*
+ * If we are non-root, we can only deal with our own uid.
+ */
+ if (geteuid() != 0) {
+ if (uid != geteuid()) {
+ ERR("Client (%d)/Server (%d) UID mismatch (and sessiond is not root)",
+ uid, geteuid());
+ return -EPERM;
+ }
+ }
+
+ ret = pipe(retval_pipe);
+ if (ret < 0) {
+ perror("pipe");
+ goto end;
+ }
+ run_as_data.data = data;
+ run_as_data.cmd = cmd;
+ run_as_data.uid = uid;
+ run_as_data.gid = gid;
+ run_as_data.retval_pipe = retval_pipe[1]; /* write end */
+ child_stack = mmap(NULL, CHILD_STACK_SIZE,
+ PROT_WRITE | PROT_READ,
+ MAP_PRIVATE | MAP_GROWSDOWN | MAP_ANONYMOUS | MAP_STACK,
+ -1, 0);
+ if (child_stack == MAP_FAILED) {
+ perror("mmap");
+ ret = -ENOMEM;
+ goto close_pipe;
+ }
+ /*
+ * Pointing to the middle of the stack to support architectures
+ * where the stack grows up (HPPA).
+ */
+ pid = clone(child_run_as, child_stack + (CHILD_STACK_SIZE / 2),
+ CLONE_FILES | SIGCHLD | CLONE_VM,
+ &run_as_data, NULL);
+ if (pid < 0) {
+ perror("clone");
+ ret = pid;
+ goto unmap_stack;
+ }
+ /* receive return value */
+ readleft = sizeof(retval);
+ index = 0;
+ do {
+ readlen = read(retval_pipe[0], &retval.c[index], readleft);
+ if (readlen < 0) {
+ perror("read");
+ ret = -1;
+ break;
+ }
+ readleft -= readlen;
+ index += readlen;
+ } while (readleft > 0);
+
+ /*
+ * Parent: wait for child to return, in which case the
+ * shared memory map will have been created.
+ */
+ pid = waitpid(pid, &status, 0);
+ if (pid < 0 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) {
+ perror("wait");
+ ret = -1;
+ }
+unmap_stack:
+ ret = munmap(child_stack, CHILD_STACK_SIZE);
+ if (ret < 0) {
+ perror("munmap");
+ }
+close_pipe:
+ close(retval_pipe[0]);
+ close(retval_pipe[1]);
+end:
+ return retval.i;
+}
+
+int mkdir_recursive_run_as(const char *path, mode_t mode, uid_t uid, gid_t gid)
+{
+ struct mkdir_data data;
+
+ DBG3("mkdir() recursive %s with mode %d for uid %d and gid %d",
+ path, mode, uid, gid);
+ data.path = path;
+ data.mode = mode;
+ return run_as(_mkdir_recursive, &data, uid, gid);
+}
+
+int mkdir_run_as(const char *path, mode_t mode, uid_t uid, gid_t gid)
+{
+ struct mkdir_data data;
+
+ DBG3("mkdir() %s with mode %d for uid %d and gid %d",
+ path, mode, uid, gid);
+ data.path = path;
+ data.mode = mode;
+ return run_as(_mkdir, &data, uid, gid);
+}
+
+/*
+ * Note: open_run_as is currently not working. We'd need to pass the fd
+ * opened in the child to the parent.
+ */
+int open_run_as(const char *path, int flags, mode_t mode, uid_t uid, gid_t gid)
+{
+ struct open_data data;
+
+ DBG3("open() %s with flags %X mode %d for uid %d and gid %d",
+ path, flags, mode, uid, gid);
+ data.path = path;
+ data.flags = flags;
+ data.mode = mode;
+ return run_as(_open, &data, uid, gid);
+}
projects / lttng-tools.git / blobdiff