+bool isOnRootFilesystem(const char *path)
+{
+ int rc = 0;
+ struct statfs sfb;
+
+ rc = statfs(path, &sfb);
+ if (rc != 0) {
+ secerror("Unable to check if path is on rootfs: %d, %s", errno, path);
+ return false;
+ }
+ return ((sfb.f_flags & MNT_ROOTFS) == MNT_ROOTFS);
+}
+
+bool pathExists(const char *path)
+{
+ int rc;
+
+ if (!path) {
+ secerror("path is NULL");
+ return false;
+ }
+
+ rc = access(path, F_OK);
+ if (rc != 0) {
+ if (errno != ENOENT) {
+ secerror("Unable to check if path exists: %d, %s", errno, path);
+ }
+ return false;
+ }
+
+ return true;
+}
+
+bool pathMatchesXattrFilenameSpec(const char *path)
+{
+ char *baseName = NULL;
+ bool ret = false;
+
+ if (!path) {
+ secerror("path is NULL");
+ goto done;
+ }
+
+ // Extra byte for NULL storage.
+ baseName = (char *)malloc(strlen(path) + 1);
+ if (!baseName) {
+ secerror("Unable to allocate space for storing basename: %d [%s]", errno, strerror(errno));
+ goto done;
+ }
+
+ // basename_r will return a "/" if path is only slashes. It will return
+ // a "." for a NULL/empty path. Both of these cases are handled by the logic
+ // later. The only situation where basename_r will return a NULL is when path
+ // is longer than MAXPATHLEN.
+
+ if (basename_r(path, baseName) == NULL) {
+ secerror("Could not get basename of %s: %d [%s]", path, errno, strerror(errno));
+ goto done;
+ }
+
+ // The file name must start with "._", followed by the name
+ // of the file for which it stores the xattrs. Hence, its length
+ // must be at least three --> 2 for "._" and 1 for a non-empty file
+ // name.
+ if (strlen(baseName) < 3) {
+ goto done;
+ }
+
+ if (baseName[0] != '.' || baseName[1] != '_') {
+ goto done;
+ }
+
+ ret = true;
+
+done:
+ if (baseName) {
+ free(baseName);
+ }
+
+ return ret;
+}
+
+bool pathIsRegularFile(const char *path)
+{
+ if (!path) {
+ secerror("path is NULL");
+ return false;
+ }
+
+ struct stat sb;
+ if (stat(path, &sb)) {
+ secerror("Unable to stat %s: %d [%s]", path, errno, strerror(errno));
+ return false;
+ }
+
+ return (sb.st_mode & S_IFREG) == S_IFREG;
+}
+
+bool pathHasXattrs(const char *path)
+{
+ if (!path) {
+ secerror("path is NULL");
+ return false;
+ }
+
+ ssize_t xattrSize = listxattr(path, NULL, 0, 0);
+ if (xattrSize == -1) {
+ secerror("Unable to acquire the xattr list from %s", path);
+ return false;
+ }
+
+ return (xattrSize > 0);
+}
+
+bool pathFileSystemUsesXattrFiles(const char *path)
+{
+ struct _VolumeCapabilitiesWrapped {
+ uint32_t length;
+ vol_capabilities_attr_t volume_capabilities;
+ } __attribute__((aligned(4), packed));
+
+ struct attrlist attr_list;
+ struct _VolumeCapabilitiesWrapped volume_cap_wrapped;
+ struct statfs sfb;
+
+ if (!path) {
+ secerror("path is NULL");
+ return false;
+ }
+
+ int ret = statfs(path, &sfb);
+ if (ret != 0) {
+ secerror("Unable to convert %s to its filesystem mount [statfs failed]: %d [%s]", path, errno, strerror(errno));
+ return false;
+ }
+ path = sfb.f_mntonname;
+
+ memset(&attr_list, 0, sizeof(attr_list));
+ attr_list.bitmapcount = ATTR_BIT_MAP_COUNT;
+ attr_list.volattr = ATTR_VOL_INFO | ATTR_VOL_CAPABILITIES;
+
+ ret = getattrlist(path, &attr_list, &volume_cap_wrapped, sizeof(volume_cap_wrapped), 0);
+ if (ret) {
+ secerror("Unable to get volume capabilities from %s: %d [%s]", path, errno, strerror(errno));
+ return false;
+ }
+
+ if (volume_cap_wrapped.length != sizeof(volume_cap_wrapped)) {
+ secerror("getattrlist return length incorrect, expected %lu, got %u", sizeof(volume_cap_wrapped), volume_cap_wrapped.length);
+ return false;
+ }
+
+ // The valid bit tells us whether the corresponding bit in capabilities is valid
+ // or not. For file systems where the valid bit isn't set, we can safely assume that
+ // extended attributes aren't supported natively.
+
+ bool xattr_valid = (volume_cap_wrapped.volume_capabilities.valid[VOL_CAPABILITIES_INTERFACES] & VOL_CAP_INT_EXTENDED_ATTR) == VOL_CAP_INT_EXTENDED_ATTR;
+ if (!xattr_valid) {
+ return true;
+ }
+
+ bool xattr_capability = (volume_cap_wrapped.volume_capabilities.capabilities[VOL_CAPABILITIES_INTERFACES] & VOL_CAP_INT_EXTENDED_ATTR) == VOL_CAP_INT_EXTENDED_ATTR;
+ if (!xattr_capability) {
+ return true;
+ }
+
+ return false;
+}
+
+bool pathIsValidXattrFile(const string fullPath, const char *scope)
+{
+ // Confirm that fullPath begins from root.
+ if (fullPath[0] != '/') {
+ secinfo(scope, "%s isn't a full path, but a relative path", fullPath.c_str());
+ return false;
+ }
+
+ // Confirm that fullPath is a regular file.
+ if (!pathIsRegularFile(fullPath.c_str())) {
+ secinfo(scope, "%s isn't a regular file", fullPath.c_str());
+ return false;
+ }
+
+ // Check that the file name matches the Xattr file spec.
+ if (!pathMatchesXattrFilenameSpec(fullPath.c_str())) {
+ secinfo(scope, "%s doesn't match Xattr file path spec", fullPath.c_str());
+ return false;
+ }
+
+ // We are guaranteed to have at least one "/" by virtue of fullPath
+ // being a path from the root of the filesystem hierarchy.
+ //
+ // We construct the real file name by copying everything up to
+ // the last "/", adding the "/" back in, then skipping
+ // over the backslash (+1) and the "._" (+2) in the rest of the
+ // string.
+
+ size_t lastBackSlash = fullPath.find_last_of("/");
+ const string realFilePath = fullPath.substr(0, lastBackSlash) + "/" + fullPath.substr(lastBackSlash + 1 + 2);
+
+ if (!pathExists(realFilePath.c_str())) {
+ secinfo(scope, "%s does not exist, forcing resource validation on %s", realFilePath.c_str(), fullPath.c_str());
+ return false;
+ }
+
+ // Lastly, we need to confirm that the real file contains some xattrs. If not,
+ // then the file represented by fullPath isn't an xattr file.
+ if (!pathHasXattrs(realFilePath.c_str())) {
+ secinfo(scope, "%s does not contain xattrs, forcing resource validation on %s", realFilePath.c_str(), fullPath.c_str());
+ return false;
+ }
+
+ return true;
+}
+
projects / apple / security.git / blobdiff