| 1 | /* |
| 2 | * lttngtrace.c |
| 3 | * |
| 4 | * lttngtrace starts/stop system wide tracing around program execution. |
| 5 | * |
| 6 | * Copyright (c) 2010 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 7 | * |
| 8 | * This program is free software; you can redistribute it and/or modify |
| 9 | * it under the terms of the GNU General Public License as published by |
| 10 | * the Free Software Foundation; either version 2 of the License, or |
| 11 | * (at your option) any later version. |
| 12 | * |
| 13 | * This program is distributed in the hope that it will be useful, |
| 14 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 16 | * GNU General Public License for more details. |
| 17 | * |
| 18 | * You should have received a copy of the GNU General Public License along |
| 19 | * with this program; if not, write to the Free Software Foundation, Inc., |
| 20 | * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. |
| 21 | * |
| 22 | * This file should be setuid root, and belong to a "tracing" group. Only users |
| 23 | * part of the tracing group can trace and view the traces gathered. |
| 24 | * |
| 25 | * TODO: LTTng should support per-session tracepoint activation. |
| 26 | * TODO: use mkstemp() and save last trace name in user's home directory. |
| 27 | * TODO: drop priv + reenable standard signal handlers + call lttv at the end. |
| 28 | * TODO: -o option should be limited to creation of files in locations that the |
| 29 | * calling user has file creation access. |
| 30 | */ |
| 31 | |
| 32 | #include <errno.h> |
| 33 | #include <stdio.h> |
| 34 | #include <fcntl.h> |
| 35 | #include <signal.h> |
| 36 | #include <unistd.h> |
| 37 | #include <stdlib.h> |
| 38 | #include <string.h> |
| 39 | #include <limits.h> |
| 40 | #include <dirent.h> |
| 41 | #include <sys/wait.h> |
| 42 | #include <sys/stat.h> |
| 43 | #include <sys/types.h> |
| 44 | |
| 45 | #if DEBUG |
| 46 | #define printf_dbg(fmt, args...) printf(fmt, args) |
| 47 | #else |
| 48 | #define printf_dbg(fmt, ...) |
| 49 | #endif |
| 50 | |
| 51 | static char *trace_path; |
| 52 | static char trace_path_pid[PATH_MAX]; |
| 53 | static int autotrace; /* |
| 54 | * Is the trace_path automatically chosen in /tmp ? Can |
| 55 | * we unlink if needed ? |
| 56 | */ |
| 57 | static int sigfwd_pid; |
| 58 | static char *progname = NULL; |
| 59 | |
| 60 | void usage(void) { |
| 61 | fprintf(stderr, "usage : %s [-o trace_name] command\n", progname); |
| 62 | fprintf(stderr, "\nTracing tool for LTTng and UST\n\ |
| 63 | \n\ |
| 64 | Options:\n\ |
| 65 | -o trace_name\t\tOutput file of the trace\n\ |
| 66 | "); |
| 67 | } |
| 68 | |
| 69 | static int recunlink(const char *dirname) |
| 70 | { |
| 71 | DIR *dir; |
| 72 | struct dirent *entry; |
| 73 | char path[PATH_MAX]; |
| 74 | |
| 75 | dir = opendir(dirname); |
| 76 | if (dir == NULL) { |
| 77 | if (errno == ENOENT) |
| 78 | return 0; |
| 79 | perror("Error opendir()"); |
| 80 | return -errno; |
| 81 | } |
| 82 | |
| 83 | while ((entry = readdir(dir)) != NULL) { |
| 84 | if (strcmp(entry->d_name, ".") && strcmp(entry->d_name, "..")) { |
| 85 | snprintf(path, (size_t) PATH_MAX, "%s/%s", dirname, |
| 86 | entry->d_name); |
| 87 | if (entry->d_type == DT_DIR) |
| 88 | recunlink(path); |
| 89 | else |
| 90 | unlink(path); |
| 91 | } |
| 92 | } |
| 93 | closedir(dir); |
| 94 | rmdir(dirname); |
| 95 | |
| 96 | return 0; |
| 97 | } |
| 98 | |
| 99 | static int start_tracing(void) |
| 100 | { |
| 101 | int ret; |
| 102 | char command[PATH_MAX]; |
| 103 | |
| 104 | if (autotrace) { |
| 105 | ret = recunlink(trace_path); |
| 106 | if (ret) |
| 107 | return ret; |
| 108 | } |
| 109 | |
| 110 | /* |
| 111 | * Create the directory in /tmp to deal with races (refuse if fail). |
| 112 | * Only allow user and group to read the trace data (to limit |
| 113 | * information disclosure). |
| 114 | */ |
| 115 | ret = mkdir(trace_path, S_IRWXU|S_IRWXG); |
| 116 | if (ret) { |
| 117 | perror("Trace directory creation error"); |
| 118 | return ret; |
| 119 | } |
| 120 | ret = system("ltt-armall > /dev/null"); |
| 121 | if (ret) |
| 122 | return ret; |
| 123 | |
| 124 | ret = snprintf(command, PATH_MAX - 1, |
| 125 | "lttctl -C -w %s autotrace1 > /dev/null", |
| 126 | trace_path); |
| 127 | ret = ret < 0 ? ret : 0; |
| 128 | if (ret) |
| 129 | return ret; |
| 130 | ret = system(command); |
| 131 | if (ret) |
| 132 | return ret; |
| 133 | } |
| 134 | |
| 135 | static int stop_tracing(uid_t uid, gid_t egid) |
| 136 | { |
| 137 | int ret; |
| 138 | |
| 139 | ret = system("lttctl -D autotrace1 > /dev/null"); |
| 140 | if (ret) |
| 141 | return ret; |
| 142 | ret = system("ltt-disarmall > /dev/null"); |
| 143 | if (ret) |
| 144 | return ret; |
| 145 | /* Hand the trace back to the user after tracing is over */ |
| 146 | ret = chown(trace_path, uid, egid); |
| 147 | if (ret) { |
| 148 | perror("chown error"); |
| 149 | return ret; |
| 150 | } |
| 151 | } |
| 152 | |
| 153 | static int write_child_pid(pid_t pid, uid_t uid, gid_t gid) |
| 154 | { |
| 155 | int fd; |
| 156 | FILE *fp; |
| 157 | int ret; |
| 158 | |
| 159 | /* Create the file as exclusive to deal with /tmp file creation races */ |
| 160 | fd = open(trace_path_pid, O_WRONLY | O_CREAT | O_EXCL | O_TRUNC, |
| 161 | S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP); |
| 162 | fp = fdopen(fd, "w"); |
| 163 | if (!fp) { |
| 164 | perror("Error writing child pid"); |
| 165 | return -errno; |
| 166 | } |
| 167 | |
| 168 | fprintf(fp, "%u", (unsigned int) pid); |
| 169 | ret = fclose(fp); |
| 170 | if (ret) |
| 171 | perror("Error in fclose"); |
| 172 | /* Hand pid information file back to user */ |
| 173 | ret = chown(trace_path_pid, uid, gid); |
| 174 | if (ret) |
| 175 | perror("chown error"); |
| 176 | return ret; |
| 177 | } |
| 178 | |
| 179 | static int parse_options(int argc, char **argv, int *arg) |
| 180 | { |
| 181 | int i, c; |
| 182 | |
| 183 | while ((c = getopt(argc, argv, "ho:")) != -1) { |
| 184 | switch (c) { |
| 185 | case 'o': |
| 186 | trace_path = strdup(optarg); |
| 187 | break; |
| 188 | case 'h': |
| 189 | usage(); |
| 190 | exit(EXIT_SUCCESS); |
| 191 | case '?': |
| 192 | usage(); |
| 193 | exit(EXIT_FAILURE); |
| 194 | default: |
| 195 | exit(EXIT_FAILURE); |
| 196 | } |
| 197 | } |
| 198 | |
| 199 | if (argc - optind > 0) { |
| 200 | for (i = optind + 1; i < argc; i++) { |
| 201 | printf ("Non-option argument %s\n", argv[i]); |
| 202 | } |
| 203 | } else { |
| 204 | usage(); |
| 205 | exit(EXIT_FAILURE); |
| 206 | } |
| 207 | |
| 208 | *arg = optind; |
| 209 | |
| 210 | return 0; |
| 211 | } |
| 212 | |
| 213 | static int init_trace_path(void) |
| 214 | { |
| 215 | int ret; |
| 216 | |
| 217 | if (!trace_path) { |
| 218 | trace_path = "/tmp/autotrace1"; |
| 219 | autotrace = 1; |
| 220 | } |
| 221 | ret = snprintf(trace_path_pid, PATH_MAX - 1, "%s/%s", |
| 222 | trace_path, "pid"); |
| 223 | ret = ret < 0 ? ret : 0; |
| 224 | return ret; |
| 225 | } |
| 226 | |
| 227 | static void sighandler(int signo, siginfo_t *siginfo, void *context) |
| 228 | { |
| 229 | kill(sigfwd_pid, signo); |
| 230 | } |
| 231 | |
| 232 | static int init_sighand(sigset_t *saved_mask) |
| 233 | { |
| 234 | sigset_t sig_all_mask; |
| 235 | int gret = 0, ret; |
| 236 | |
| 237 | /* Block signals */ |
| 238 | ret = sigfillset(&sig_all_mask); |
| 239 | if (ret) |
| 240 | perror("Error in sigfillset"); |
| 241 | gret = (gret == 0) ? ret : gret; |
| 242 | ret = sigprocmask(SIG_SETMASK, &sig_all_mask, saved_mask); |
| 243 | if (ret) |
| 244 | perror("Error in sigprocmask"); |
| 245 | gret = (gret == 0) ? ret : gret; |
| 246 | return gret; |
| 247 | } |
| 248 | |
| 249 | static int forward_signals(pid_t pid, sigset_t *saved_mask) |
| 250 | { |
| 251 | struct sigaction act; |
| 252 | int gret = 0, ret; |
| 253 | |
| 254 | /* Forward SIGINT and SIGTERM */ |
| 255 | sigfwd_pid = pid; |
| 256 | act.sa_sigaction = sighandler; |
| 257 | act.sa_flags = SA_SIGINFO | SA_RESTART; |
| 258 | sigemptyset(&act.sa_mask); |
| 259 | ret = sigaction(SIGINT, &act, NULL); |
| 260 | if (ret) |
| 261 | perror("Error in sigaction"); |
| 262 | gret = (gret == 0) ? ret : gret; |
| 263 | ret = sigaction(SIGTERM, &act, NULL); |
| 264 | if (ret) |
| 265 | perror("Error in sigaction"); |
| 266 | gret = (gret == 0) ? ret : gret; |
| 267 | |
| 268 | /* Reenable signals */ |
| 269 | ret = sigprocmask(SIG_SETMASK, saved_mask, NULL); |
| 270 | if (ret) |
| 271 | perror("Error in sigprocmask"); |
| 272 | gret = (gret == 0) ? ret : gret; |
| 273 | return gret; |
| 274 | } |
| 275 | |
| 276 | int main(int argc, char *argv[]) |
| 277 | { |
| 278 | uid_t euid, uid; |
| 279 | gid_t egid, gid; |
| 280 | pid_t pid; |
| 281 | int gret = 0, ret = 0; |
| 282 | int arg = 1; |
| 283 | sigset_t saved_mask; |
| 284 | |
| 285 | progname = argv[0]; |
| 286 | |
| 287 | if (argc < 2) { |
| 288 | usage(); |
| 289 | return -ENOENT; |
| 290 | } |
| 291 | |
| 292 | euid = geteuid(); |
| 293 | uid = getuid(); |
| 294 | egid = getegid(); |
| 295 | gid = geteuid(); |
| 296 | |
| 297 | if (euid != 0 && uid != 0) { |
| 298 | printf("%s must be setuid root\n", progname); |
| 299 | return -EPERM; |
| 300 | } |
| 301 | |
| 302 | printf_dbg("euid: %d\n", euid); |
| 303 | printf_dbg("uid: %d\n", uid); |
| 304 | printf_dbg("egid: %d\n", egid); |
| 305 | printf_dbg("gid: %d\n", gid); |
| 306 | |
| 307 | ret = parse_options(argc, argv, &arg); |
| 308 | if (ret) |
| 309 | return ret; |
| 310 | |
| 311 | ret = init_trace_path(); |
| 312 | gret = (gret == 0) ? ret : gret; |
| 313 | |
| 314 | ret = init_sighand(&saved_mask); |
| 315 | gret = (gret == 0) ? ret : gret; |
| 316 | |
| 317 | ret = start_tracing(); |
| 318 | if (ret) |
| 319 | return ret; |
| 320 | |
| 321 | pid = fork(); |
| 322 | if (pid > 0) { /* parent */ |
| 323 | int status; |
| 324 | |
| 325 | ret = forward_signals(pid, &saved_mask); |
| 326 | gret = (gret == 0) ? ret : gret; |
| 327 | pid = wait(&status); |
| 328 | if (pid == -1) |
| 329 | gret = (gret == 0) ? -errno : gret; |
| 330 | |
| 331 | ret = stop_tracing(uid, egid); |
| 332 | gret = (gret == 0) ? ret : gret; |
| 333 | ret = write_child_pid(pid, uid, egid); |
| 334 | gret = (gret == 0) ? ret : gret; |
| 335 | } else if (pid == 0) { /* child */ |
| 336 | /* Drop root euid before executing child program */ |
| 337 | seteuid(uid); |
| 338 | /* Reenable signals */ |
| 339 | ret = sigprocmask(SIG_SETMASK, &saved_mask, NULL); |
| 340 | if (ret) { |
| 341 | perror("Error in sigprocmask"); |
| 342 | return ret; |
| 343 | } |
| 344 | ret = execvp(argv[arg], &argv[arg]); |
| 345 | if (ret) |
| 346 | perror("Execution error"); |
| 347 | return ret; |
| 348 | } else { /* error */ |
| 349 | perror("Error in fork"); |
| 350 | return -errno; |
| 351 | } |
| 352 | return ret; |
| 353 | } |