| 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 | */ |
| 28 | |
| 29 | #include <errno.h> |
| 30 | #include <stdio.h> |
| 31 | #include <fcntl.h> |
| 32 | #include <signal.h> |
| 33 | #include <unistd.h> |
| 34 | #include <stdlib.h> |
| 35 | #include <string.h> |
| 36 | #include <limits.h> |
| 37 | #include <dirent.h> |
| 38 | #include <sys/wait.h> |
| 39 | #include <sys/stat.h> |
| 40 | #include <sys/types.h> |
| 41 | |
| 42 | #if DEBUG |
| 43 | #define printf_dbg(fmt, args...) printf(fmt, args) |
| 44 | #else |
| 45 | #define printf_dbg(fmt, ...) |
| 46 | #endif |
| 47 | |
| 48 | static char *trace_path; |
| 49 | static char trace_path_pid[PATH_MAX]; |
| 50 | static int autotrace; /* |
| 51 | * Is the trace_path automatically chosen in /tmp ? Can |
| 52 | * we unlink if needed ? |
| 53 | */ |
| 54 | static int sigfwd_pid; |
| 55 | |
| 56 | static int recunlink(const char *dirname) |
| 57 | { |
| 58 | DIR *dir; |
| 59 | struct dirent *entry; |
| 60 | char path[PATH_MAX]; |
| 61 | |
| 62 | dir = opendir(dirname); |
| 63 | if (dir == NULL) { |
| 64 | if (errno == ENOENT) |
| 65 | return 0; |
| 66 | perror("Error opendir()"); |
| 67 | return -errno; |
| 68 | } |
| 69 | |
| 70 | while ((entry = readdir(dir)) != NULL) { |
| 71 | if (strcmp(entry->d_name, ".") && strcmp(entry->d_name, "..")) { |
| 72 | snprintf(path, (size_t) PATH_MAX, "%s/%s", dirname, |
| 73 | entry->d_name); |
| 74 | if (entry->d_type == DT_DIR) |
| 75 | recunlink(path); |
| 76 | else |
| 77 | unlink(path); |
| 78 | } |
| 79 | } |
| 80 | closedir(dir); |
| 81 | rmdir(dirname); |
| 82 | |
| 83 | return 0; |
| 84 | } |
| 85 | |
| 86 | static int start_tracing(void) |
| 87 | { |
| 88 | int ret; |
| 89 | char command[PATH_MAX]; |
| 90 | |
| 91 | if (autotrace) { |
| 92 | ret = recunlink(trace_path); |
| 93 | if (ret) |
| 94 | return ret; |
| 95 | } |
| 96 | |
| 97 | /* |
| 98 | * Create the directory in /tmp to deal with races (refuse if fail). |
| 99 | * Only allow user and group to read the trace data (to limit |
| 100 | * information disclosure). |
| 101 | */ |
| 102 | ret = mkdir(trace_path, S_IRWXU|S_IRWXG); |
| 103 | if (ret) { |
| 104 | perror("Trace directory creation error"); |
| 105 | return ret; |
| 106 | } |
| 107 | ret = system("ltt-armall > /dev/null"); |
| 108 | if (ret) |
| 109 | return ret; |
| 110 | |
| 111 | ret = snprintf(command, PATH_MAX - 1, |
| 112 | "lttctl -C -w %s autotrace1 > /dev/null", |
| 113 | trace_path); |
| 114 | ret = ret < 0 ? ret : 0; |
| 115 | if (ret) |
| 116 | return ret; |
| 117 | ret = system(command); |
| 118 | if (ret) |
| 119 | return ret; |
| 120 | } |
| 121 | |
| 122 | static int stop_tracing(uid_t uid, gid_t egid) |
| 123 | { |
| 124 | int ret; |
| 125 | |
| 126 | ret = system("lttctl -D autotrace1 > /dev/null"); |
| 127 | if (ret) |
| 128 | return ret; |
| 129 | ret = system("ltt-disarmall > /dev/null"); |
| 130 | if (ret) |
| 131 | return ret; |
| 132 | /* Hand the trace back to the user after tracing is over */ |
| 133 | ret = chown(trace_path, uid, egid); |
| 134 | if (ret) { |
| 135 | perror("chown error"); |
| 136 | return ret; |
| 137 | } |
| 138 | } |
| 139 | |
| 140 | static int write_child_pid(pid_t pid, uid_t uid, gid_t gid) |
| 141 | { |
| 142 | int fd; |
| 143 | FILE *fp; |
| 144 | int ret; |
| 145 | |
| 146 | /* Create the file as exclusive to deal with /tmp file creation races */ |
| 147 | fd = open(trace_path_pid, O_WRONLY | O_CREAT | O_EXCL | O_TRUNC, |
| 148 | S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP); |
| 149 | fp = fdopen(fd, "w"); |
| 150 | if (!fp) { |
| 151 | perror("Error writing child pid"); |
| 152 | return -errno; |
| 153 | } |
| 154 | |
| 155 | fprintf(fp, "%u", (unsigned int) pid); |
| 156 | ret = fclose(fp); |
| 157 | if (ret) |
| 158 | perror("Error in fclose"); |
| 159 | /* Hand pid information file back to user */ |
| 160 | ret = chown(trace_path_pid, uid, gid); |
| 161 | if (ret) |
| 162 | perror("chown error"); |
| 163 | return ret; |
| 164 | } |
| 165 | |
| 166 | static int parse_options(int argc, char *argv[], int *arg) |
| 167 | { |
| 168 | int ret = 0; |
| 169 | |
| 170 | for (;;) { |
| 171 | if (*arg >= argc |
| 172 | || argv[*arg][0] != '-' |
| 173 | || argv[*arg][0] == '\0' |
| 174 | || argv[*arg][1] == '\0' |
| 175 | || !strcmp(argv[*arg], "--")) |
| 176 | break; |
| 177 | switch (argv[*arg][1]) { |
| 178 | case 'o': if (*arg + 1 >= argc) { |
| 179 | printf("Missing -o trace name\n"); |
| 180 | ret = -EINVAL; |
| 181 | break; |
| 182 | } |
| 183 | trace_path = argv[*arg + 1]; |
| 184 | (*arg) += 2; |
| 185 | break; |
| 186 | default: printf("Unknown option -%c\n", argv[*arg][1]); |
| 187 | ret = -EINVAL; |
| 188 | return ret; |
| 189 | } |
| 190 | } |
| 191 | return ret; |
| 192 | } |
| 193 | |
| 194 | static int init_trace_path(void) |
| 195 | { |
| 196 | int ret; |
| 197 | |
| 198 | if (!trace_path) { |
| 199 | trace_path = "/tmp/autotrace1"; |
| 200 | autotrace = 1; |
| 201 | } |
| 202 | ret = snprintf(trace_path_pid, PATH_MAX - 1, "%s/%s", |
| 203 | trace_path, "pid"); |
| 204 | ret = ret < 0 ? ret : 0; |
| 205 | return ret; |
| 206 | } |
| 207 | |
| 208 | static void sighandler(int signo, siginfo_t *siginfo, void *context) |
| 209 | { |
| 210 | kill(sigfwd_pid, signo); |
| 211 | } |
| 212 | |
| 213 | static int init_sighand(sigset_t *saved_mask) |
| 214 | { |
| 215 | sigset_t sig_all_mask; |
| 216 | int gret = 0, ret; |
| 217 | |
| 218 | /* Block signals */ |
| 219 | ret = sigfillset(&sig_all_mask); |
| 220 | if (ret) |
| 221 | perror("Error in sigfillset"); |
| 222 | gret = (gret == 0) ? ret : gret; |
| 223 | ret = sigprocmask(SIG_SETMASK, &sig_all_mask, saved_mask); |
| 224 | if (ret) |
| 225 | perror("Error in sigprocmask"); |
| 226 | gret = (gret == 0) ? ret : gret; |
| 227 | return gret; |
| 228 | } |
| 229 | |
| 230 | static int forward_signals(pid_t pid, sigset_t *saved_mask) |
| 231 | { |
| 232 | struct sigaction act; |
| 233 | int gret = 0, ret; |
| 234 | |
| 235 | /* Forward SIGINT and SIGTERM */ |
| 236 | sigfwd_pid = pid; |
| 237 | act.sa_sigaction = sighandler; |
| 238 | act.sa_flags = SA_SIGINFO | SA_RESTART; |
| 239 | sigemptyset(&act.sa_mask); |
| 240 | ret = sigaction(SIGINT, &act, NULL); |
| 241 | if (ret) |
| 242 | perror("Error in sigaction"); |
| 243 | gret = (gret == 0) ? ret : gret; |
| 244 | ret = sigaction(SIGTERM, &act, NULL); |
| 245 | if (ret) |
| 246 | perror("Error in sigaction"); |
| 247 | gret = (gret == 0) ? ret : gret; |
| 248 | |
| 249 | /* Reenable signals */ |
| 250 | ret = sigprocmask(SIG_SETMASK, saved_mask, NULL); |
| 251 | if (ret) |
| 252 | perror("Error in sigprocmask"); |
| 253 | gret = (gret == 0) ? ret : gret; |
| 254 | return gret; |
| 255 | } |
| 256 | |
| 257 | int main(int argc, char *argv[]) |
| 258 | { |
| 259 | uid_t euid, uid; |
| 260 | gid_t egid, gid; |
| 261 | pid_t pid; |
| 262 | int gret = 0, ret = 0; |
| 263 | int arg = 1; |
| 264 | sigset_t saved_mask; |
| 265 | |
| 266 | if (argc < 2) |
| 267 | return -ENOENT; |
| 268 | |
| 269 | euid = geteuid(); |
| 270 | uid = getuid(); |
| 271 | egid = getegid(); |
| 272 | gid = geteuid(); |
| 273 | |
| 274 | if (euid != 0 && uid != 0) { |
| 275 | printf("%s must be setuid root\n", argv[0]); |
| 276 | return -EPERM; |
| 277 | } |
| 278 | |
| 279 | printf_dbg("euid: %d\n", euid); |
| 280 | printf_dbg("uid: %d\n", uid); |
| 281 | printf_dbg("egid: %d\n", egid); |
| 282 | printf_dbg("gid: %d\n", gid); |
| 283 | |
| 284 | if (arg < argc) { |
| 285 | ret = parse_options(argc, argv, &arg); |
| 286 | if (ret) |
| 287 | return ret; |
| 288 | } |
| 289 | |
| 290 | ret = init_trace_path(); |
| 291 | gret = (gret == 0) ? ret : gret; |
| 292 | |
| 293 | ret = init_sighand(&saved_mask); |
| 294 | gret = (gret == 0) ? ret : gret; |
| 295 | |
| 296 | ret = start_tracing(); |
| 297 | if (ret) |
| 298 | return ret; |
| 299 | |
| 300 | pid = fork(); |
| 301 | if (pid > 0) { /* parent */ |
| 302 | int status; |
| 303 | |
| 304 | ret = forward_signals(pid, &saved_mask); |
| 305 | gret = (gret == 0) ? ret : gret; |
| 306 | pid = wait(&status); |
| 307 | if (pid == -1) |
| 308 | gret = (gret == 0) ? -errno : gret; |
| 309 | |
| 310 | ret = stop_tracing(uid, egid); |
| 311 | gret = (gret == 0) ? ret : gret; |
| 312 | ret = write_child_pid(pid, uid, egid); |
| 313 | gret = (gret == 0) ? ret : gret; |
| 314 | } else if (pid == 0) { /* child */ |
| 315 | /* Drop root euid before executing child program */ |
| 316 | seteuid(uid); |
| 317 | /* Reenable signals */ |
| 318 | ret = sigprocmask(SIG_SETMASK, &saved_mask, NULL); |
| 319 | if (ret) { |
| 320 | perror("Error in sigprocmask"); |
| 321 | return ret; |
| 322 | } |
| 323 | ret = execvp(argv[arg], &argv[arg]); |
| 324 | if (ret) |
| 325 | perror("Execution error"); |
| 326 | return ret; |
| 327 | } else { /* error */ |
| 328 | perror("Error in fork"); |
| 329 | return -errno; |
| 330 | } |
| 331 | return ret; |
| 332 | } |