test: add basic integration tests

Signed-off-by: Justin Chadwell <me@jedevc.com>

vendor/github.com/containerd/continuity/groups_unix.go

@@ -0,0 +1,130 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+//nolint:unused,deadcode
+package continuity
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+	"strconv"
+	"strings"
+)
+
+// TODO(stevvooe): This needs a lot of work before we can call it useful.
+
+type groupIndex struct {
+	byName map[string]*group
+	byGID  map[int]*group
+}
+
+func getGroupIndex() (*groupIndex, error) {
+	f, err := os.Open("/etc/group")
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	groups, err := parseGroups(f)
+	if err != nil {
+		return nil, err
+	}
+
+	return newGroupIndex(groups), nil
+}
+
+func newGroupIndex(groups []group) *groupIndex {
+	gi := &groupIndex{
+		byName: make(map[string]*group),
+		byGID:  make(map[int]*group),
+	}
+
+	for i, group := range groups {
+		gi.byGID[group.gid] = &groups[i]
+		gi.byName[group.name] = &groups[i]
+	}
+
+	return gi
+}
+
+type group struct {
+	name    string
+	gid     int
+	members []string
+}
+
+func getGroupName(gid int) (string, error) {
+	f, err := os.Open("/etc/group")
+	if err != nil {
+		return "", err
+	}
+	defer f.Close()
+
+	groups, err := parseGroups(f)
+	if err != nil {
+		return "", err
+	}
+
+	for _, group := range groups {
+		if group.gid == gid {
+			return group.name, nil
+		}
+	}
+
+	return "", fmt.Errorf("no group for gid")
+}
+
+// parseGroups parses an /etc/group file for group names, ids and membership.
+// This is unix specific.
+func parseGroups(rd io.Reader) ([]group, error) {
+	var groups []group
+	scanner := bufio.NewScanner(rd)
+
+	for scanner.Scan() {
+		if strings.HasPrefix(scanner.Text(), "#") {
+			continue // skip comment
+		}
+
+		parts := strings.SplitN(scanner.Text(), ":", 4)
+
+		if len(parts) != 4 {
+			return nil, fmt.Errorf("bad entry: %q", scanner.Text())
+		}
+
+		name, _, sgid, smembers := parts[0], parts[1], parts[2], parts[3]
+
+		gid, err := strconv.Atoi(sgid)
+		if err != nil {
+			return nil, fmt.Errorf("bad gid: %q", gid)
+		}
+
+		members := strings.Split(smembers, ",")
+
+		groups = append(groups, group{
+			name:    name,
+			gid:     gid,
+			members: members,
+		})
+	}
+
+	if scanner.Err() != nil {
+		return nil, scanner.Err()
+	}
+
+	return groups, nil
+}