| // Copyright (c) 2009 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| // The following is duplicated from base/linux_utils.cc. |
| // We shouldn't link against C++ code in a setuid binary. |
| |
| // Needed for O_DIRECTORY, must be defined before fcntl.h is included |
| // (and it can be included earlier than the explicit #include below |
| // in some versions of glibc). |
| #define _GNU_SOURCE |
| |
| #include "sandbox/linux/suid/linux_util.h" |
| |
| #include <dirent.h> |
| #include <errno.h> |
| #include <fcntl.h> |
| #include <limits.h> |
| #include <stdio.h> |
| #include <stdlib.h> |
| #include <string.h> |
| #include <sys/stat.h> |
| #include <sys/types.h> |
| #include <unistd.h> |
| |
| // expected prefix of the target of the /proc/self/fd/%d link for a socket |
| static const char kSocketLinkPrefix[] = "socket:["; |
| |
| // Parse a symlink in /proc/pid/fd/$x and return the inode number of the |
| // socket. |
| // inode_out: (output) set to the inode number on success |
| // path: e.g. /proc/1234/fd/5 (must be a UNIX domain socket descriptor) |
| static bool ProcPathGetInodeAt(ino_t* inode_out, |
| int base_dir_fd, |
| const char* path) { |
| // We also check that the path is relative. |
| if (!inode_out || !path || *path == '/') |
| return false; |
| char buf[256]; |
| const ssize_t n = readlinkat(base_dir_fd, path, buf, sizeof(buf) - 1); |
| if (n < 0) |
| return false; |
| buf[n] = 0; |
| |
| if (memcmp(kSocketLinkPrefix, buf, sizeof(kSocketLinkPrefix) - 1)) |
| return false; |
| |
| char* endptr = NULL; |
| errno = 0; |
| const unsigned long long int inode_ull = |
| strtoull(buf + sizeof(kSocketLinkPrefix) - 1, &endptr, 10); |
| if (inode_ull == ULLONG_MAX || !endptr || *endptr != ']' || errno != 0) |
| return false; |
| |
| *inode_out = inode_ull; |
| return true; |
| } |
| |
| static DIR* opendirat(int base_dir_fd, const char* name) { |
| // Also check that |name| is relative. |
| if (base_dir_fd < 0 || !name || *name == '/') |
| return NULL; |
| int new_dir_fd = openat(base_dir_fd, name, O_RDONLY | O_DIRECTORY); |
| if (new_dir_fd < 0) |
| return NULL; |
| |
| return fdopendir(new_dir_fd); |
| } |
| |
| bool FindProcessHoldingSocket(pid_t* pid_out, ino_t socket_inode) { |
| bool already_found = false; |
| |
| DIR* proc = opendir("/proc"); |
| if (!proc) |
| return false; |
| |
| const uid_t uid = getuid(); |
| struct dirent* dent; |
| while ((dent = readdir(proc))) { |
| char* endptr = NULL; |
| errno = 0; |
| const unsigned long int pid_ul = strtoul(dent->d_name, &endptr, 10); |
| if (pid_ul == ULONG_MAX || !endptr || *endptr || errno != 0) |
| continue; |
| |
| // We have this setuid code here because the zygote and its children have |
| // /proc/$pid/fd owned by root. While scanning through /proc, we add this |
| // extra check so users cannot accidentally gain information about other |
| // users' processes. To determine process ownership, we use the property |
| // that if user foo owns process N, then /proc/N is owned by foo. |
| int proc_pid_fd = -1; |
| { |
| char buf[256]; |
| struct stat statbuf; |
| snprintf(buf, sizeof(buf), "/proc/%lu", pid_ul); |
| proc_pid_fd = open(buf, O_RDONLY | O_DIRECTORY); |
| if (proc_pid_fd < 0) |
| continue; |
| if (fstat(proc_pid_fd, &statbuf) < 0 || uid != statbuf.st_uid) { |
| close(proc_pid_fd); |
| continue; |
| } |
| } |
| |
| DIR* fd = opendirat(proc_pid_fd, "fd"); |
| if (!fd) { |
| close(proc_pid_fd); |
| continue; |
| } |
| |
| while ((dent = readdir(fd))) { |
| char buf[256]; |
| int printed = snprintf(buf, sizeof(buf), "fd/%s", dent->d_name); |
| if (printed < 0 || printed >= (int)(sizeof(buf) - 1)) { |
| continue; |
| } |
| |
| ino_t fd_inode; |
| if (ProcPathGetInodeAt(&fd_inode, proc_pid_fd, buf)) { |
| if (fd_inode == socket_inode) { |
| if (already_found) { |
| closedir(fd); |
| close(proc_pid_fd); |
| closedir(proc); |
| return false; |
| } |
| |
| already_found = true; |
| *pid_out = pid_ul; |
| break; |
| } |
| } |
| } |
| closedir(fd); |
| close(proc_pid_fd); |
| } |
| closedir(proc); |
| |
| return already_found; |
| } |