fix security issue that predictable filenames with system

src/kylin-network-interface.c

@@ -32,6 +32,8 @@
 #include <fcntl.h>
 #include <sys/syslog.h>
 #include <pwd.h>
+#include <sys/wait.h>
+#include <errno.h>
 
 //获取网络接口名
 ifname *kylin_network_get_ifacename()
@@ -194,19 +196,43 @@ activecon *kylin_network_get_activecon_info()
     struct passwd *pwd;
     pwd = getpwuid(getuid());
     char *name = pwd->pw_name;
-    char *tmpPrefix = "/tmp/kylin-nm-activecon-";
-    char *chr = "nmcli connection show -active > ";
+    char tmpTemplate[] = "/tmp/kylin-nm-activecon-XXXXXX";
+    int fd = mkstemp(tmpTemplate);
+    if (fd == -1) {
+        syslog(LOG_ERR, "mkstemp() failed in kylin_network_get_activecon_info: %s", strerror(errno));
+        return NULL;
+    }
 
-    char *cmd;
-    asprintf(&cmd, "%s%s%s", chr, tmpPrefix, name);
-    char *path;
-    asprintf(&path, "%s%s", tmpPrefix, name);
-    int status = system(cmd);
-    if (status != 0)
-        syslog(LOG_ERR, "execute 'nmcli connection show -active' in function 'kylin_network_get_activecon_info' failed");
-    free(cmd);
+    pid_t pid = fork();
+    if (pid == -1) {
+        syslog(LOG_ERR, "fork() in kylin_network_get_activecon_info failed");
+        close(fd);
+        unlink(tmpTemplate);
+        return NULL;
+    } else if (pid == 0) {
+        //Child process
+        dup2(fd, STDOUT_FILENO);
+        close(fd);
 
-    char *filename = path;
+        execlp("nmcli", "nmcli", "connection", "show", "--active",(char *)NULL);
+
+        // If execlp() fails
+        syslog(LOG_ERR, "execlp() failed");
+        _exit(EXIT_FAILURE);
+    } else {
+        // Parent process
+        int status;
+        waitpid(pid, &status, 0);
+        if (status !=0 ) {
+            syslog(LOG_ERR, "execute 'nmcli connection show --active' in 'kylin_network_get_activecon_info' failed");
+            close(fd);
+            unlink(tmpTemplate);
+            return NULL;
+        }
+        close(fd);
+    }
+
+    char *filename = strdup(tmpTemplate);
 
     FILE *activefp;
     int activenum=0;
@@ -233,7 +259,6 @@ activecon *kylin_network_get_activecon_info()
         printf("error!");
 
     }
-    free(path);
 
     fgets(StrLine,1024,fp);
     while(!feof(fp))
@@ -325,6 +350,8 @@ activecon *kylin_network_get_activecon_info()
     }
     fclose(fp);
 
+    unlink(tmpTemplate);
+
     activelist[count].con_name=NULL;
     activelist[count].type=NULL;
     activelist[count].dev=NULL;