Commit message: ccpp: do not read data from root directories

Users are allowed to modify /proc/[pid]/root to any directory by running
their own MOUNT namespace.

Related: #1211835

Signed-off-by: Jakub Filak <jfilak@redhat.com>
CVE: CVE-2015-3315
CWE: CWE-59
Vulnerability description: Automatic Bug Reporting Tool (ABRT) allows local users to read, change the ownership of, or have other unspecified impact on arbitrary files via a symlink attack on (1) /var/tmp/abrt/*/maps, (2) /tmp/jvm-*/hs_error.log, (3) /proc/*/exe, (4) /etc/os-release in a chroot, or (5) an unspecified root directory related to librpm.

Project: abrt

int main(int argc, char** argv)
{
    /* Kernel starts us with all fd's closed.
     * But it's dangerous:
     * fprintf(stderr) can dump messages into random fds, etc.
     * Ensure that if any of fd 0,1,2 is closed, we open it to /dev/null.
     */
    int fd = xopen("/dev/null", O_RDWR);
    while (fd < 2)
	fd = xdup(fd);
    if (fd > 2)
	close(fd);

    if (argc < 8)
    {
        /* percent specifier:         %s   %c              %p  %u  %g  %t   %e          %h */
        /* argv:                  [0] [1]  [2]             [3] [4] [5] [6]  [7]         [8]*/
        error_msg_and_die("Usage: %s SIGNO CORE_SIZE_LIMIT PID UID GID TIME BINARY_NAME [HOSTNAME]", argv[0]);
    }

    /* Not needed on 2.6.30.
     * At least 2.6.18 has a bug where
     * argv[1] = "SIGNO CORE_SIZE_LIMIT PID ..."
     * argv[2] = "CORE_SIZE_LIMIT PID ..."
     * and so on. Fixing it:
     */
    if (strchr(argv[1], ' '))
    {
        int i;
        for (i = 1; argv[i]; i++)
        {
            strchrnul(argv[i], ' ')[0] = '\0';
        }
    }

    logmode = LOGMODE_JOURNAL;

    /* Parse abrt.conf */
    load_abrt_conf();
    /* ... and plugins/CCpp.conf */
    bool setting_MakeCompatCore;
    bool setting_SaveBinaryImage;
    {
        map_string_t *settings = new_map_string();
        load_abrt_plugin_conf_file("CCpp.conf", settings);
        const char *value;
        value = get_map_string_item_or_NULL(settings, "MakeCompatCore");
        setting_MakeCompatCore = value && string_to_bool(value);
        value = get_map_string_item_or_NULL(settings, "SaveBinaryImage");
        setting_SaveBinaryImage = value && string_to_bool(value);
        value = get_map_string_item_or_NULL(settings, "VerboseLog");
        if (value)
            g_verbose = xatoi_positive(value);
        free_map_string(settings);
    }

    errno = 0;
    const char* signal_str = argv[1];
    int signal_no = xatoi_positive(signal_str);
    off_t ulimit_c = strtoull(argv[2], NULL, 10);
    if (ulimit_c < 0) /* unlimited? */
    {
        /* set to max possible >0 value */
        ulimit_c = ~((off_t)1 << (sizeof(off_t)*8-1));
    }
    const char *pid_str = argv[3];
    pid_t pid = xatoi_positive(argv[3]);
    uid_t uid = xatoi_positive(argv[4]);
    if (errno || pid <= 0)
    {
        perror_msg_and_die("PID '%s' or limit '%s' is bogus", argv[3], argv[2]);
    }

    {
        char *s = xmalloc_fopen_fgetline_fclose(VAR_RUN"/abrt/saved_core_pattern");
        /* If we have a saved pattern and it's not a "|PROG ARGS" thing... */
        if (s && s[0] != '|')
            core_basename = s;
        else
            free(s);
    }

    struct utsname uts;
    if (!argv[8]) /* no HOSTNAME? */
    {
        uname(&uts);
        argv[8] = uts.nodename;
    }

    char path[PATH_MAX];

    int src_fd_binary = -1;
    char *executable = get_executable(pid, setting_SaveBinaryImage ? &src_fd_binary : NULL);
    if (executable && strstr(executable, "/abrt-hook-ccpp"))
    {
        error_msg_and_die("PID %lu is '%s', not dumping it to avoid recursion",
                        (long)pid, executable);
    }

    user_pwd = get_cwd(pid); /* may be NULL on error */
    log_notice("user_pwd:'%s'", user_pwd);

    sprintf(path, "/proc/%lu/status", (long)pid);
    proc_pid_status = xmalloc_xopen_read_close(path, /*maxsz:*/ NULL);

    uid_t fsuid = uid;
    uid_t tmp_fsuid = get_fsuid();
    int suid_policy = dump_suid_policy();
    if (tmp_fsuid != uid)
    {
        /* use root for suided apps unless it's explicitly set to UNSAFE */
        fsuid = 0;
        if (suid_policy == DUMP_SUID_UNSAFE)
        {
            fsuid = tmp_fsuid;
        }
    }

    /* Open a fd to compat coredump, if requested and is possible */
    if (setting_MakeCompatCore && ulimit_c != 0)
        /* note: checks "user_pwd == NULL" inside; updates core_basename */
        user_core_fd = open_user_core(uid, fsuid, pid, &argv[1]);

    if (executable == NULL)
    {
        /* readlink on /proc/$PID/exe failed, don't create abrt dump dir */
        error_msg("Can't read /proc/%lu/exe link", (long)pid);
        goto create_user_core;
    }

    const char *signame = NULL;
    switch (signal_no)
    {
        case SIGILL : signame = "ILL" ; break;
        case SIGFPE : signame = "FPE" ; break;
        case SIGSEGV: signame = "SEGV"; break;
        case SIGBUS : signame = "BUS" ; break; //Bus error (bad memory access)
        case SIGABRT: signame = "ABRT"; break; //usually when abort() was called
        case SIGTRAP: signame = "TRAP"; break; //Trace/breakpoint trap
        default: goto create_user_core; // not a signal we care about
    }

    if (!daemon_is_ok())
    {
        /* not an error, exit with exit code 0 */
        log("abrtd is not running. If it crashed, "
            "/proc/sys/kernel/core_pattern contains a stale value, "
            "consider resetting it to 'core'"
        );
        goto create_user_core;
    }

    if (g_settings_nMaxCrashReportsSize > 0)
    {
        /* If free space is less than 1/4 of MaxCrashReportsSize... */
        if (low_free_space(g_settings_nMaxCrashReportsSize, g_settings_dump_location))
            goto create_user_core;
    }

    /* Check /var/tmp/abrt/last-ccpp marker, do not dump repeated crashes
     * if they happen too often. Else, write new marker value.
     */
    snprintf(path, sizeof(path), "%s/last-ccpp", g_settings_dump_location);
    if (check_recent_crash_file(path, executable))
    {
        /* It is a repeating crash */
        goto create_user_core;
    }

    const char *last_slash = strrchr(executable, '/');
    if (last_slash && strncmp(++last_slash, "abrt", 4) == 0)
    {
        /* If abrtd/abrt-foo crashes, we don't want to create a _directory_,
         * since that can make new copy of abrtd to process it,
         * and maybe crash again...
         * Unlike dirs, mere files are ignored by abrtd.
         */
        snprintf(path, sizeof(path), "%s/%s-coredump", g_settings_dump_location, last_slash);
        int abrt_core_fd = xopen3(path, O_WRONLY | O_CREAT | O_TRUNC, 0600);
        off_t core_size = copyfd_eof(STDIN_FILENO, abrt_core_fd, COPYFD_SPARSE);
        if (core_size < 0 || fsync(abrt_core_fd) != 0)
        {
            unlink(path);
            /* copyfd_eof logs the error including errno string,
             * but it does not log file name */
            error_msg_and_die("Error saving '%s'", path);
        }
        log("Saved core dump of pid %lu (%s) to %s (%llu bytes)", (long)pid, executable, path, (long long)core_size);
        return 0;
    }

    unsigned path_len = snprintf(path, sizeof(path), "%s/ccpp-%s-%lu.new",
            g_settings_dump_location, iso_date_string(NULL), (long)pid);
    if (path_len >= (sizeof(path) - sizeof("/"FILENAME_COREDUMP)))
    {
        goto create_user_core;
    }

    /* use fsuid instead of uid, so we don't expose any sensitive
     * information of suided app in /var/tmp/abrt
     */
    dd = dd_create(path, fsuid, DEFAULT_DUMP_DIR_MODE);
    if (dd)
     {
         char *rootdir = get_rootdir(pid);
 
        dd_create_basic_files(dd, fsuid, (rootdir && strcmp(rootdir, "/") != 0) ? rootdir : NULL);
 
         char source_filename[sizeof("/proc/%lu/somewhat_long_name") + sizeof(long)*3];
         int source_base_ofs = sprintf(source_filename, "/proc/%lu/smaps", (long)pid);
        source_base_ofs -= strlen("smaps");
        char *dest_filename = concat_path_file(dd->dd_dirname, "also_somewhat_longish_name");
        char *dest_base = strrchr(dest_filename, '/') + 1;


        strcpy(source_filename + source_base_ofs, "maps");
        strcpy(dest_base, FILENAME_MAPS);
        copy_file_ext(source_filename, dest_filename, 0640, dd->dd_uid, dd->dd_gid, O_RDONLY, O_WRONLY | O_CREAT | O_TRUNC | O_EXCL);

        strcpy(source_filename + source_base_ofs, "limits");
        strcpy(dest_base, FILENAME_LIMITS);
        copy_file_ext(source_filename, dest_filename, 0640, dd->dd_uid, dd->dd_gid, O_RDONLY, O_WRONLY | O_CREAT | O_TRUNC | O_EXCL);

        strcpy(source_filename + source_base_ofs, "cgroup");
        strcpy(dest_base, FILENAME_CGROUP);
        copy_file_ext(source_filename, dest_filename, 0640, dd->dd_uid, dd->dd_gid, O_RDONLY, O_WRONLY | O_CREAT | O_TRUNC | O_EXCL);

        strcpy(dest_base, FILENAME_OPEN_FDS);
        dump_fd_info(dest_filename, source_filename, source_base_ofs, dd->dd_uid, dd->dd_gid);

        free(dest_filename);

        dd_save_text(dd, FILENAME_ANALYZER, "CCpp");
        dd_save_text(dd, FILENAME_TYPE, "CCpp");
        dd_save_text(dd, FILENAME_EXECUTABLE, executable);
        dd_save_text(dd, FILENAME_PID, pid_str);
        dd_save_text(dd, FILENAME_PROC_PID_STATUS, proc_pid_status);
        if (user_pwd)
            dd_save_text(dd, FILENAME_PWD, user_pwd);
        if (rootdir)
        {
            if (strcmp(rootdir, "/") != 0)
                dd_save_text(dd, FILENAME_ROOTDIR, rootdir);
        }

        char *reason = xasprintf("%s killed by SIG%s",
                                 last_slash, signame ? signame : signal_str);
        dd_save_text(dd, FILENAME_REASON, reason);
        free(reason);

        char *cmdline = get_cmdline(pid);
        dd_save_text(dd, FILENAME_CMDLINE, cmdline ? : "");
        free(cmdline);

        char *environ = get_environ(pid);
        dd_save_text(dd, FILENAME_ENVIRON, environ ? : "");
        free(environ);

        char *fips_enabled = xmalloc_fopen_fgetline_fclose("/proc/sys/crypto/fips_enabled");
        if (fips_enabled)
        {
            if (strcmp(fips_enabled, "0") != 0)
                dd_save_text(dd, "fips_enabled", fips_enabled);
            free(fips_enabled);
        }

        dd_save_text(dd, FILENAME_ABRT_VERSION, VERSION);

        if (src_fd_binary > 0)
        {
            strcpy(path + path_len, "/"FILENAME_BINARY);
            int dst_fd = create_or_die(path);
            off_t sz = copyfd_eof(src_fd_binary, dst_fd, COPYFD_SPARSE);
            if (fsync(dst_fd) != 0 || close(dst_fd) != 0 || sz < 0)
            {
                dd_delete(dd);
                error_msg_and_die("Error saving '%s'", path);
            }
            close(src_fd_binary);
        }

        strcpy(path + path_len, "/"FILENAME_COREDUMP);
        int abrt_core_fd = create_or_die(path);

        /* We write both coredumps at once.
         * We can't write user coredump first, since it might be truncated
         * and thus can't be copied and used as abrt coredump;
         * and if we write abrt coredump first and then copy it as user one,
         * then we have a race when process exits but coredump does not exist yet:
         * $ echo -e '#include<signal.h>\nmain(){raise(SIGSEGV);}' | gcc -o test -x c -
         * $ rm -f core*; ulimit -c unlimited; ./test; ls -l core*
         * 21631 Segmentation fault (core dumped) ./test
         * ls: cannot access core*: No such file or directory <=== BAD
         */
        off_t core_size = copyfd_sparse(STDIN_FILENO, abrt_core_fd, user_core_fd, ulimit_c);
        if (fsync(abrt_core_fd) != 0 || close(abrt_core_fd) != 0 || core_size < 0)
        {
            unlink(path);
            dd_delete(dd);
            if (user_core_fd >= 0)
            {
                xchdir(user_pwd);
                unlink(core_basename);
            }
            /* copyfd_sparse logs the error including errno string,
             * but it does not log file name */
            error_msg_and_die("Error writing '%s'", path);
        }
        if (user_core_fd >= 0
            /* error writing user coredump? */
         && (fsync(user_core_fd) != 0 || close(user_core_fd) != 0
            /* user coredump is too big? */
            || (ulimit_c == 0 /* paranoia */ || core_size > ulimit_c)
            )
        ) {
            /* nuke it (silently) */
            xchdir(user_pwd);
            unlink(core_basename);
        }

/* Because of #1211835 and #1126850 */
#if 0
        /* Save JVM crash log if it exists. (JVM's coredump per se
         * is nearly useless for JVM developers)
         */
        {
            char *java_log = xasprintf("/tmp/jvm-%lu/hs_error.log", (long)pid);
            int src_fd = open(java_log, O_RDONLY);
            free(java_log);

            /* If we couldn't open the error log in /tmp directory we can try to
             * read the log from the current directory. It may produce AVC, it
             * may produce some error log but all these are expected.
             */
            if (src_fd < 0)
            {
                java_log = xasprintf("%s/hs_err_pid%lu.log", user_pwd, (long)pid);
                src_fd = open(java_log, O_RDONLY);
                free(java_log);
            }

            if (src_fd >= 0)
            {
                strcpy(path + path_len, "/hs_err.log");
                int dst_fd = create_or_die(path);
                off_t sz = copyfd_eof(src_fd, dst_fd, COPYFD_SPARSE);
                if (close(dst_fd) != 0 || sz < 0)
                {
                    dd_delete(dd);
                    error_msg_and_die("Error saving '%s'", path);
                }
                close(src_fd);
            }
        }
#endif

        /* We close dumpdir before we start catering for crash storm case.
         * Otherwise, delete_dump_dir's from other concurrent
         * CCpp's won't be able to delete our dump (their delete_dump_dir
         * will wait for us), and we won't be able to delete their dumps.
         * Classic deadlock.
         */
        dd_close(dd);
        path[path_len] = '\0'; /* path now contains only directory name */
        char *newpath = xstrndup(path, path_len - (sizeof(".new")-1));
        if (rename(path, newpath) == 0)
            strcpy(path, newpath);
        free(newpath);

        log("Saved core dump of pid %lu (%s) to %s (%llu bytes)", (long)pid, executable, path, (long long)core_size);

        notify_new_path(path);

        /* rhbz#539551: "abrt going crazy when crashing process is respawned" */
        if (g_settings_nMaxCrashReportsSize > 0)
        {
            /* x1.25 and round up to 64m: go a bit up, so that usual in-daemon trimming
             * kicks in first, and we don't "fight" with it:
             */
            unsigned maxsize = g_settings_nMaxCrashReportsSize + g_settings_nMaxCrashReportsSize / 4;
            maxsize |= 63;
            trim_problem_dirs(g_settings_dump_location, maxsize * (double)(1024*1024), path);
        }

        free(rootdir);
        return 0;
    }

    /* We didn't create abrt dump, but may need to create compat coredump */
 create_user_core:
    if (user_core_fd >= 0)
    {
        off_t core_size = copyfd_size(STDIN_FILENO, user_core_fd, ulimit_c, COPYFD_SPARSE);
        if (fsync(user_core_fd) != 0 || close(user_core_fd) != 0 || core_size < 0)
        {
            /* perror first, otherwise unlink may trash errno */
            perror_msg("Error writing '%s'", full_core_basename);
            xchdir(user_pwd);
            unlink(core_basename);
            return 1;
        }
        if (ulimit_c == 0 || core_size > ulimit_c)
        {
            xchdir(user_pwd);
            unlink(core_basename);
            return 1;
        }
        log("Saved core dump of pid %lu to %s (%llu bytes)", (long)pid, full_core_basename, (long long)core_size);
    }

    return 0;
}