1 /*
2 * Copyright (C) 2018 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include "common/libs/utils/users.h"
18
19 #include <cerrno>
20 #include <cstring>
21 #include <sys/types.h>
22 #include <unistd.h>
23 #include <grp.h>
24
25 #include <algorithm>
26 #include <vector>
27
28 #include <android-base/logging.h>
29
30 namespace cuttlefish {
31 namespace {
GroupIdFromName(const std::string & group_name)32 gid_t GroupIdFromName(const std::string& group_name) {
33 struct group grp{};
34 struct group* grp_p{};
35 std::vector<char> buffer(100);
36 int result = 0;
37 while(true) {
38 result = getgrnam_r(group_name.c_str(), &grp, buffer.data(), buffer.size(),
39 &grp_p);
40 if (result != ERANGE) {
41 break;
42 }
43 buffer.resize(2*buffer.size());
44 }
45 if (result == 0) {
46 if (grp_p != nullptr) {
47 return grp.gr_gid;
48 } else {
49 // Caller may be checking with non-existent group name
50 return -1;
51 }
52 } else {
53 LOG(ERROR) << "Unable to get group id for group " << group_name << ": "
54 << std::strerror(result);
55 return -1;
56 }
57 }
58
GetSuplementaryGroups()59 std::vector<gid_t> GetSuplementaryGroups() {
60 int num_groups = getgroups(0, nullptr);
61 if (num_groups < 0) {
62 LOG(ERROR) << "Unable to get number of suplementary groups: "
63 << std::strerror(errno);
64 return {};
65 }
66 std::vector<gid_t> groups(num_groups + 1);
67 int retval = getgroups(groups.size(), groups.data());
68 if (retval < 0) {
69 LOG(ERROR) << "Error obtaining list of suplementary groups (list size: "
70 << groups.size() << "): " << std::strerror(errno);
71 return {};
72 }
73 return groups;
74 }
75 } // namespace
76
InGroup(const std::string & group)77 bool InGroup(const std::string& group) {
78 auto gid = GroupIdFromName(group);
79 if (gid == static_cast<gid_t>(-1)) {
80 return false;
81 }
82
83 if (gid == getegid()) {
84 return true;
85 }
86
87 auto groups = GetSuplementaryGroups();
88
89 if (std::find(groups.cbegin(), groups.cend(), gid) != groups.cend()) {
90 return true;
91 }
92 return false;
93 }
94
95 } // namespace cuttlefish
96