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Added command execution support

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Marco Cetica
2024-08-20 16:09:42 +02:00
parent 4e25735cd9
commit 77f6db18a5
3 changed files with 162 additions and 16 deletions
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110
wolf.c
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@@ -1,3 +1,5 @@
#define _GNU_SOURCE
#ifndef __linux__
#error "Unsupported platform"
#endif
@@ -11,6 +13,8 @@
#include <poll.h>
#include <time.h>
#include <sys/inotify.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <stdint.h>
#include <signal.h>
@@ -32,8 +36,10 @@ typedef enum {
typedef enum { false, true } bool;
static void handle_inotify_events(int fd, const int *wd, int wd_len, char **watched_files, const bool is_timestamp_enabled);
static void handle_inotify_events(int fd, const int *wd, int wd_len, char **watched_files, const bool is_timestamp_enabled, const char *watchdog_cmd);
static void get_timestamp(uint8_t *timestamp, const ssize_t timestamp_len);
static void exec_command(const char *cmd);
static uint8_t **tokenize_command(const char *cmd);
volatile sig_atomic_t stop_signal = 0;
void sigint_handler() {
@@ -51,6 +57,7 @@ void helper(const char *name) {
"-w, --write | Add a watchdog for writing events\n"
"-p, --permission | Add a watchdog for permissions changes\n"
"-f, --full | Enable all the previous options\n"
"-e, --exec | Execute a command when a watchdog detects a change\n"
"--no-timestamp | Disable timestamp from watchdog output\n"
"-v, --version | Show program version\n"
"-h, --help | Show this helper\n\n"
@@ -68,7 +75,8 @@ void version() {
int main(int argc, char **argv) {
int opt, opt_idx = 0;
const char *short_opts = "cdmrwpfvh";
const char *short_opts = "cdmrwpfvhe:";
char *watchdog_cmd = NULL;
uint32_t mask = 0;
bool is_timestamp_enabled = true;
struct option long_opts[] = {
@@ -79,6 +87,7 @@ int main(int argc, char **argv) {
{"write", no_argument, NULL, 'w'},
{"permission", no_argument, NULL, 'p'},
{"full", no_argument, NULL, 'f'},
{"exec", required_argument, NULL, 'e'},
{"no-timestamp", no_argument, NULL, 0 },
{"version", no_argument, NULL, 'v'},
{"help", no_argument, NULL, 'h'},
@@ -96,6 +105,7 @@ int main(int argc, char **argv) {
case 'p': mask |= IN_ATTRIB; break;
case 'f': mask = IN_CREATE | IN_DELETE | IN_DELETE_SELF | IN_MOVED_FROM |
IN_ACCESS | IN_MODIFY | IN_ATTRIB; break;
case 'e': watchdog_cmd = optarg; break;
case 0:
if(!strcmp(long_opts[opt_idx].name, "no-timestamp")) {
is_timestamp_enabled = false;
@@ -171,7 +181,9 @@ int main(int argc, char **argv) {
if(poll_num > 0) {
// Inotify events are available
if(fds->revents & POLLIN) {
handle_inotify_events(fd, wd, number_of_files, (argv + optind), is_timestamp_enabled);
handle_inotify_events(fd, wd, number_of_files, (argv + optind), is_timestamp_enabled, watchdog_cmd);
}
}
}
@@ -183,7 +195,7 @@ int main(int argc, char **argv) {
return 0;
}
static void handle_inotify_events(int fd, const int *wd, int wd_len, char **watched_files, const bool is_timestamp_enabled) {
static void handle_inotify_events(int fd, const int *wd, int wd_len, char **watched_files, const bool is_timestamp_enabled, const char *watchdog_cmd) {
// Align inotify reading buffer to inotify_event struct
char inotify_read_buf[4096]
__attribute__((aligned((__alignof__(struct inotify_event)))));
@@ -270,6 +282,11 @@ static void handle_inotify_events(int fd, const int *wd, int wd_len, char **watc
break;
}
}
// If user supplied a command, execute it
if(watchdog_cmd != NULL) {
exec_command(watchdog_cmd);
}
free(file_name);
}
memset(inotify_read_buf, 0, sizeof(inotify_read_buf));
@@ -281,3 +298,88 @@ static void get_timestamp(uint8_t *timestamp, const ssize_t timestamp_len) {
struct tm *timeinfo = localtime(&now);
strftime((char*)timestamp, timestamp_len, "%Y-%m-%d %H:%M:%S", timeinfo);
}
static void exec_command(const char *cmd) {
// Ignore SIGCHLD signals.
// This allows us to avoid blocking the parent process until the child completes
// its execution; furthermore, it allows us to prevent the creation of zombie processes
// by delegating the cleanup process to the kernel. By doing so, we lose the ability
// to check the return status of the child process.
signal(SIGCHLD, SIG_IGN);
// Execute command in a new process
pid_t pid = fork();
if(pid == -1) {
perror("fork");
exit(EXIT_FAILURE);
} else if(pid == 0) { // Child process
// Tokenize command
uint8_t **argv = tokenize_command(cmd);
// Replace memory of child process with new program
execvp((char*)argv[0], (char**)argv);
// If execvp returns, it means it has failed
switch(errno) {
case ENOENT: puts("Cannot execute command: no such file or directory"); break;
case EACCES: puts("Cannot execute command: permission denied"); break;
default: puts("Cannot execute command"); break;
}
// Free allocated resources
for (int i = 0; argv[i] != NULL; i++) {
free(argv[i]);
}
free(argv);
exit(EXIT_FAILURE);
}
}
static uint8_t **tokenize_command(const char *cmd) {
// Duplicate command
char *cmd_dup = strdup(cmd);
if(cmd_dup == NULL) {
perror("strdup");
exit(EXIT_FAILURE);
}
// Count number of arguments
size_t argc = 0;
char *token = strtok(cmd_dup, " ");
while(token != NULL) {
argc++;
token = strtok(NULL, " ");
}
// Allocate enough memory for arguments(and null terminator)
uint8_t **argv = malloc((argc + 1) * sizeof(uint8_t*));
if(argv == NULL) {
perror("malloc");
exit(EXIT_FAILURE);
}
// Reset command string and tokenize again
strcpy(cmd_dup, cmd);
size_t idx = 0;
token = strtok(cmd_dup, " ");
while(token != NULL) {
argv[idx] = (uint8_t*)strdup(token);
if(argv[idx] == NULL) {
perror("strdup");
while(idx > 0) { free(argv[--idx]); }
free(argv);
free(cmd_dup);
exit(EXIT_FAILURE);
}
idx++;
token = strtok(NULL, " ");
}
// Null-terminate the string
argv[idx] = NULL;
// Clear temporary resources
free(cmd_dup);
return argv;
}