Android 打包镜像对权限的管理

程序员文章站 2022-11-01 16:54:21

Android ext4镜像制作的主要逻辑都在system/extras/ext4_utils/make_ext4fs.c文件中，其实就是根据某个文件夹创建ext4格式的二进制文件。 ext4包含superblock，inode， inode table， group descriptors， block bitmap 和block等主要的结构。文件的权限信息一般保存在inode中。正常情况下打包文件的权限和目标目录下的权限应该是相同的static u32 build_directory_structu...

Android ext4镜像制作的主要逻辑都在system/extras/ext4_utils/make_ext4fs.c文件中，其实就是根据某个文件夹创建ext4格式的二进制文件。 ext4包含superblock，inode， inode table， group descriptors， block bitmap 和block等主要的结构。
文件的权限信息一般保存在inode中。正常情况下打包文件的权限和目标目录下的权限应该是相同的

static u32 build_directory_structure(const char *full_path, const char *dir_path, const char *target_out_path,
      u32 dir_inode, fs_config_func_t fs_config_func,
      struct selabel_handle *sehnd, int verbose, time_t fixed_time)
{
 ......
    entries = scandir(full_path, &namelist, filter_dot, (void*)alphasort);
 ......
   for (i = 0; i < entries; i++) {
     dentries[i].filename = strdup(namelist[i]->d_name);
     ret = lstat(dentries[i].full_path, &stat);   // 获取原来文件stat信息
      if (ret < 0) {
         error_errno("lstat");
         i--;
         entries--;
         continue;
      }
 
      dentries[i].size = stat.st_size;
      dentries[i].mode = stat.st_mode & (S_ISUID|S_ISGID|S_ISVTX|S_IRWXU|S_IRWXG|S_IRWXO); // 保留原来权限信息
      if (fixed_time == -1) {   // 跟新mtime
         dentries[i].mtime = stat.st_mtime;
      } else {
         dentries[i].mtime = fixed_time;
      }
      uint64_t capabilities;
      if (fs_config_func != NULL) {  // 如果是Android系统还需要使用fs_config_func来设置文件权限和属主属组
#ifdef ANDROID
         unsigned int mode = 0;
         unsigned int uid = 0;
         unsigned int gid = 0;
         int dir = S_ISDIR(stat.st_mode);
         fs_config_func(dentries[i].path, dir, target_out_path, &uid, &gid, &mode, &capabilities);
         dentries[i].mode = mode;
         dentries[i].uid = uid;
         dentries[i].gid = gid;
         dentries[i].capabilities = capabilities;
#else
         error("can't set android permissions - built without android support");
#endif
      }

void fs_config(const char *path, int dir, const char *target_out_path,
               unsigned *uid, unsigned *gid, unsigned *mode, uint64_t *capabilities)
{
    const struct fs_path_config *pc;
    int fd, plen;
 
    if (path[0] == '/') {
        path++;
    }
 
    plen = strlen(path);
 
    fd = fs_config_open(dir, target_out_path);
    if (fd >= 0) { // 检查配置文件是否有设置该目录或者文件属性
        struct fs_path_config_from_file header;
 
        while (TEMP_FAILURE_RETRY(read(fd, &header, sizeof(header))) == sizeof(header)) {
            char *prefix;
            uint16_t host_len = get2LE((const uint8_t *)&header.len);
            ssize_t len, remainder = host_len - sizeof(header);
            if (remainder <= 0) {
                ALOGE("%s len is corrupted", dir ? conf_dir : conf_file);
                break;
            }
            prefix = calloc(1, remainder);
            if (!prefix) {
                ALOGE("%s out of memory", dir ? conf_dir : conf_file);
                break;
            }
            if (TEMP_FAILURE_RETRY(read(fd, prefix, remainder)) != remainder) {
                free(prefix);
                ALOGE("%s prefix is truncated", dir ? conf_dir : conf_file);
                break;
            }
            len = strnlen(prefix, remainder);
            if (len >= remainder) { /* missing a terminating null */
                free(prefix);
                ALOGE("%s is corrupted", dir ? conf_dir : conf_file);
                break;
            }
            if (fs_config_cmp(dir, prefix, len, path, plen)) {
                free(prefix);
                close(fd);
                *uid = get2LE((const uint8_t *)&(header.uid));
                *gid = get2LE((const uint8_t *)&(header.gid));
                *mode = (*mode & (~07777)) | get2LE((const uint8_t *)&(header.mode));
                *capabilities = get8LE((const uint8_t *)&(header.capabilities));
                return;
            }
            free(prefix);
        }
        close(fd);
    }
 
    // 使用android_dirs或者 android_files数组检查配置属性
    pc = dir ? android_dirs : android_files;
    for(; pc->prefix; pc++){
        if (fs_config_cmp(dir, pc->prefix, strlen(pc->prefix), path, plen)) {
            break;
        }
    }
    *uid = pc->uid;
    *gid = pc->gid;
    *mode = (*mode & (~07777)) | pc->mode;
    *capabilities = pc->capabilities;
}

函数先检查配置文件中有没有配置目录属性，再检查android_dirs或者android_files中有没有设置配置属性，最终使用配置属性来更新目录的属性（uid，gid，mode，capabilities）。

配置属性信息如下：

static const struct fs_path_config android_dirs[] = {
    { 00770, AID_SYSTEM, AID_CACHE,  0, "cache" },
    { 00771, AID_SYSTEM, AID_SYSTEM, 0, "data/app" },
    { 00771, AID_SYSTEM, AID_SYSTEM, 0, "data/app-private" },
    { 00771, AID_ROOT,   AID_ROOT,   0, "data/dalvik-cache" },
    { 00771, AID_SYSTEM, AID_SYSTEM, 0, "data/data" },
    { 00771, AID_SHELL,  AID_SHELL,  0, "data/local/tmp" },
    { 00771, AID_SHELL,  AID_SHELL,  0, "data/local" },
    { 01771, AID_SYSTEM, AID_MISC,   0, "data/misc" },
    { 00770, AID_DHCP,   AID_DHCP,   0, "data/misc/dhcp" },
    { 00771, AID_SHARED_RELRO, AID_SHARED_RELRO, 0, "data/misc/shared_relro" },
    { 00775, AID_MEDIA_RW, AID_MEDIA_RW, 0, "data/media" },
    { 00775, AID_MEDIA_RW, AID_MEDIA_RW, 0, "data/media/Music" },
    { 00771, AID_SYSTEM, AID_SYSTEM, 0, "data" },
    { 00750, AID_ROOT,   AID_SHELL,  0, "sbin" },
    { 00755, AID_ROOT,   AID_SHELL,  0, "system/bin" },
    { 00755, AID_ROOT,   AID_SHELL,  0, "system/vendor" },
    { 00755, AID_ROOT,   AID_SHELL,  0, "system/xbin" },
    { 00755, AID_ROOT,   AID_ROOT,   0, "system/etc/ppp" },
    { 00755, AID_ROOT,   AID_SHELL,  0, "vendor" },
    { 00777, AID_ROOT,   AID_ROOT,   0, "sdcard" },
    { 00755, AID_ROOT,   AID_ROOT,   0, 0 },
};
 
 
 
 
static const struct fs_path_config android_files[] = {
    { 00440, AID_ROOT,      AID_SHELL,     0, "system/etc/init.goldfish.rc" },
    { 00550, AID_ROOT,      AID_SHELL,     0, "system/etc/init.goldfish.sh" },
    { 00550, AID_ROOT,      AID_SHELL,     0, "system/etc/init.ril" },
    { 00550, AID_DHCP,      AID_SHELL,     0, "system/etc/dhcpcd/dhcpcd-run-hooks" },
    { 00555, AID_ROOT,      AID_ROOT,      0, "system/etc/ppp/*" },
    { 00555, AID_ROOT,      AID_ROOT,      0, "system/etc/rc.*" },
    { 00444, AID_ROOT,      AID_ROOT,      0, conf_dir + 1 },
    { 00444, AID_ROOT,      AID_ROOT,      0, conf_file + 1 },
    { 00644, AID_SYSTEM,    AID_SYSTEM,    0, "data/app/*" },
    { 00644, AID_MEDIA_RW,  AID_MEDIA_RW,  0, "data/media/*" },
    { 00644, AID_SYSTEM,    AID_SYSTEM,    0, "data/app-private/*" },
    { 00644, AID_APP,       AID_APP,       0, "data/data/*" },
 
    /* the following five files are INTENTIONALLY set-uid, but they
     * are NOT included on user builds. */
    { 06755, AID_ROOT,      AID_SHELL,     0, "system/xbin/su" },
    { 07777, AID_ROOT,      AID_SHELL,     0, "system/xbin/deamonsu" },
    { 06755, AID_ROOT,      AID_SHELL,     0, "system/xbin/supolicy" },
    { 06755, AID_ROOT,      AID_SHELL,     0, "system/xbin/dropbear" },
    { 06755, AID_ROOT,      AID_ROOT,      0, "system/xbin/librank" },
    { 06755, AID_ROOT,      AID_ROOT,      0, "system/xbin/procrank" },
    { 06755, AID_ROOT,      AID_ROOT,      0, "system/xbin/procmem" },
    { 04770, AID_ROOT,      AID_RADIO,     0, "system/bin/pppd-ril" },
 
    /* the following files have enhanced capabilities and ARE included in user builds. */
    { 00750, AID_ROOT,      AID_SHELL,     (1ULL << CAP_SETUID) | (1ULL << CAP_SETGID), "system/bin/run-as" },
    { 00700, AID_SYSTEM,    AID_SHELL,     (1ULL << CAP_BLOCK_SUSPEND), "system/bin/inputflinger" },
 
    { 00750, AID_ROOT,      AID_ROOT,      0, "system/bin/uncrypt" },
    { 00750, AID_ROOT,      AID_ROOT,      0, "system/bin/install-recovery.sh" },
    { 00755, AID_ROOT,      AID_SHELL,     0, "system/bin/*" },
    { 00755, AID_ROOT,      AID_ROOT,      0, "system/lib/valgrind/*" },
    { 00755, AID_ROOT,      AID_ROOT,      0, "system/lib64/valgrind/*" },
    { 00755, AID_ROOT,      AID_SHELL,     0, "system/xbin/*" },
    { 00755, AID_ROOT,      AID_SHELL,     0, "system/vendor/bin/*" },
    { 00755, AID_ROOT,      AID_SHELL,     0, "vendor/bin/*" },
    { 00750, AID_ROOT,      AID_SHELL,     0, "sbin/*" },
    { 00755, AID_ROOT,      AID_ROOT,      0, "bin/*" },
    { 00750, AID_ROOT,      AID_SHELL,     0, "init*" },
    { 00750, AID_ROOT,      AID_SHELL,     0, "sbin/fs_mgr" },
    { 00640, AID_ROOT,      AID_SHELL,     0, "fstab.*" },
    { 00644, AID_ROOT,      AID_ROOT,      0, 0 },
};

本文地址：https://blog.csdn.net/woai110120130/article/details/112549228

Android 打包镜像对权限的管理

Android 打包镜像对权限的管理

Android 8.0 API 24.0 以上版本对SD卡的读写权限无效的问题

Android中对已安装应用的管理实现

RDIFramework.NET V3.3 Web版角色授权管理新增角色对操作权限项、模块起止生效日期的设置

Android 打包镜像对权限的管理

Android 8.0 API 24.0 以上版本对SD卡的读写权限无效的问题